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Semester 2 St Guide KEY
Chapter 20: Urinary System
I. Introduction
A. The organs of the urinary system are kidneys, ureters, urinary bladder and urethra.
B. The functions of the kidneys are to remove substances from blood, form urine, and to regulate
certain metabolic processes.
C. The function of the ureter is to carry urine from the kidneys to the bladder.
D. The function of the bladder is to store urine.
E. The function of the urethra is to convey urine from the bladder to the outside.
II. Kidneys
A. Introduction
1. A kidney is reddish brown in color and bean shaped.
2. A kidney is enclosed by a tough, fibrous capsule.
B. Location of Kidneys
1. The kidneys are located on either side of the vertebral column in a depression high on the
posterior wall of the abdominal cavity. They are positioned about the level of the 1st three
lumbar vertebrae.
2. Retroperitoneally means behind the parietal peritoneum and against the deep muscles of the
back.
C. Kidney Structure
1. The renal sinus is a hollow chamber on the medial side of each kidney.
2. The renal pelvis is the expansion of the ureters in the kidney.
3. The renal pelvis is divided into major calyces.
4. Major calyces are divided into minor calyces.
5. Renal papillae are small projections that project into each minor calyx.
6. The renal medulla is an inner region composed of conical masses called renal pyramids.
7. Renal pyramids are divisions of the renal medulla.
8. The renal cortex is the outer region of a kidney.
9. Renal columns are cortical tissues between renal pyramids.
10. The renal capsule is a fibrous membrane surrounding a kidney.
D. Functions of the Kidneys
1. The main functions of the kidneys are to regulate the volume, composition, and pH of body
fluids and to remove metabolic wastes from the blood and excrete them to the outside.
2. Erythropoietin functions to regulate the production of red blood cells.
3. Renin regulates blood pressure.
4. Hemodialysis is an artificial means of removing substances from blood that would normally
be excreted in urine.
E. Renal Blood Vessels
1. Renal arteries arise from the abdominal aorta.
2. At rest, the renal arteries contain 15% t0 30% of the total cardiac output.
3. Renal arteries branch into interlobar arteries, which pass between renal pyramids.
4. Interlobar arteries branch into arcuate arteries.
5. Arcuate arteries branch into interlobular arteries.
6. Interlobular arteries branch into afferent arterioles.
7. Afferent arterioles lead to the nephrons.
8. Venous blood of the kidneys is returned through a series of vessels that generally correspond
to the arterial pathways.
9. Renal veins join the inferior vena cava.
F. Nephrons
1. Structure of a Nephron
a. Functional units of the kidneys are called nephrons.
b. Each nephron consists of a renal corpuscle and renal tubules.
c. A renal corpuscle consists of a glomerulus and glomerular capsule.
d. A glomerulus is a tuft of capillaries.
e. A glomerular capsule is thin walled, saclike structure the surrounds a glomerulus.
f. Afferent arterioles give rise to glomeruli, which lead to efferent arterioles.
g. The two layers of the glomerular capsule are a visceral layer and a parietal layer.
h. Podocytes are located in the visceral layer.
i. Slit pores are cleft between podocytes.
j. The renal tubule leads away from the glomerular capsule.
k. The parts of the renal tubule are proximal convoluted tubule, nephron loop, and distal
convoluted tubules.
l. Distal convoluted tubules merge together to form a collecting duct, which empties into
a minor calyx.
2. Juxtaglomerular Apparatus
a. The macula densa is comprised of epithelial cells of the distal convoluted tubule that
contact and are between the afferent and efferent arterioles.
b. The juxtaglomerular cells are vascular smooth muscle cells in the walls of an afferent
arteriole near its attachment to a glomerulus.
c. The juxtaglomerular apparatus is composed of juxtaglomerular cells and macula densa
cells.
d. The juxtaglomerular apparatus is important in regulating the secretion of renin.
3. Cortical and Juxtamedullary Nephrons
a. Cortical nephrons have relatively short nephron loops that do not reach the renal
medulla.
b. Juxtamedullary nephrons have corpuscles that extend deep into the medulla.
c. The juxtamedullary nephrons are important in regulating water balance.
4. Blood Supply of a Nephron
1. Blood enters a glomerulus through an afferent arteriole.
2. Blood leaves a glomerulus through an efferent arteriole.
3. An efferent arteriole delivers blood to the peritubular capillary system.
4. A peritubular capillary system is located around the renal tubule.
5. Vasa recta are capillary loops that are closely associated with juxtamedullary
nephrons.
6. Blood leaves the peritubular capillary system through the venous system of the
kidney.
III. Urine Formation
A. Introduction
1. The main function of the nephrons is to control the composition of body fluids and remove
wastes from the blood.
2. Urine is the product produced by kidneys and contains wastes, excess water, and electrolytes.
3. The three processes involved in urine formation are glomerular filtration, tubular
reabsorption, and tubular secretion.
4. In glomerular filtration, blood plasma is filtered.
5. The function of tubular reabsorption is to return most of the products filtered from plasma
back to the blood.
6. The function of tubular secretion is to put waste products into the filtrate to be excreted from
the kidney.
B. Glomerular Filtration
1. Glomerular filtration is the process in which water and other small dissolved molecules and
ions are filtered out of the glomerular capillary plasma and into the glomerular capsule.
2. Glomerular filtrate is the fluid in the glomerular capsule.
3. The normal composition of glomerular filtrate is mostly water and the same solutes as in
blood plasma, except for the larger protein molecules.
C. Filtration Pressure
1. The main force that moves substances through the glomerular capillary wall is the hydrostatic
pressure of the blood inside.
2. Glomerular filtration is also influenced by the osmotic pressure of the blood plasma in the
glomerulus and the hydrostatic pressure inside the glomerular capsule.
3. Net filtration pressure is the net effect of all forces that influence glomerular filtration and
normally favors filtration at the glomerulus.
4. Net filtration can be calculated by subtracting forces opposing filtration from forces favoring
filtration.
D. Filtration Rate
1. The glomerular filtration rate is directly proportional to the net filtration pressure.
2. The factors that affect glomerular filtration are glomerular hydrostatic pressure, glomerular
plasma osmotic pressure, or hydrostatic pressure in the glomerular capsule.
3. Normally the most important factor affecting net filtration pressure and GFR is glomerular
hydrostatic pressure.
4. If the afferent arteriole constricts, net filtration pressure decreases and the filtration rate drops.
5. If the efferent arteriole constricts, net filtration pressure increases and the filtration rate rises.
6. Factors that can change the hydrostatic pressure in the glomerular capsule are obstructions in
the glomerular capsule.
7. If hydrostatic pressure in the glomerular capsule becomes too high, net filtration pressure will
decrease.
E. Control of Filtration Rate
1. GFR may increase when body fluids are in excess and decrease when the body must conserve
fluid.
2. If blood pressure and volume drop, vasoconstriction of the afferent arterioles results, which
leads to a decrease in filtration pressure and GFR.
3. If excess body fluids are detected, vasodilation of the afferent arterioles results, which leads
to an increase in filtration pressure and GFR.
4. Renin is secreted by the juxtaglomerular cells in response to stimulation from sympathetic
nerves and pressure-sensitive cells.
5. Renal baroreceptors detect pressure.
6. In the bloodstream, renin reacts with angiotensinogen to form angiotensin I.
7. Angiotensin I is used to make angiotensin II.
8. The effects of angiotensin II are vasocontriction, increased aldosterone secretion, increased
ADH secretion, and increased thirst.
9. The functions of ANP are to stimulate sodium excretion through a number of mechanisms,
including increasing GFR.
F. Tubular Reabsorption
1. Introduction
a. Tubular reabsorption is the process by which substances are transported out of the
tubular fluid, through the epithelium of the renal tubule, and into the interstitial fluid and
then into the peritubular capillaries.
b. Tubular reabsorption returns substances to the internal environment.
c. In tubular reabsorption, substances must first cross the cell membrane facing the inside
of the tubule and then the cell membrane facing the interstitial fluid.
d. Active tubular reabsorption requires ATP.
e. The factors that enhance the rate of fluid reabsorption from the renal tubule are the
low pressure in the peritubular capillary, the increased permeability of the peritubular
capillary wall, and the colloid osmotic pressure of the peritubular capillary plasma.
f. Tubular reabsorption occurs throughout the renal tubules but most occurs in the
proximal convoluted portion.
g. Microvilli in the proximal convoluted tubule function to greatly increase the surface
area exposed to the glomerular filtrate and enhance reabsorption.
h. Segments of the renal tubule are adapted to reabsorb specific substances, using
particular modes of transport.
i. Usually all of the glucose in glomerular filtrate is reabsorbed because there are enough
carrier molecules to transport it.
j. The renal plasma threshold is when the plasma concentration of a substance increases
to a critical level in which more substances are in the filtrate than the active transport
mechanisms can handle.
k. Glucose is excreted in urine when its concentration exceeds the renal plasma
threshold.
l. Diuresis is an increase in urine volume.
m. Osmotic diuresis is when nonreabsorbed glucose in the tubular fluid draws water into
the renal tubules by osmosis, thus increasing urine volume.
n. Examples of substances that are reabsorbed through renal tubules are glucose, amino
acids, small proteins, creatine, lactic acid, citric acid, uric acid, ascorbic acid, and many
ions.
2. Sodium and Water Reabsorption
a. Water reabsorption occurs by osmosis and is closely associated with the active
reabsorption of sodium ions.
b. If sodium reabsorption increases, water reabsorption increases.
c. Much of the sodium reabsorption occurs in proximal segment of the renal tubule by
active transport.
d. When sodium ions move through the tubular wall, negatively charged ions move with
them.
e. About 70% of water and sodium may be reabsorbed before urine is excreted.
f. Two hormones that affect sodium and water reabsorption are ADH and aldosterone.
G. Tubular Secretion
1. In tubular secretion, substances move from the plasma of the peritubular capillary into the
fluid of the renal tubule.
2. Examples of substances that are secreted into renal tubules are drugs, histamine, ammonia and
various ions.
3. To summarize, urine forms as a result of glomerular filtration of materials from blood plasma,
reabsorption of substances, and secretion of substances.
H. Regulation of Urine Concentration and Volume
1. Aldosterone and ANP affect the solute concentration of urine.
2. The cells lining the later portion of the distal convoluted tubule and the collecting ducts are
impermeable to water unless ADH is present.
3. A countercurrent mechanism ensures that the medullary interstitial fluid becomes hypertonic.
4. Chloride ions are reabsorbed in the in the ascending limb and sodium ions follow the chloride
ions.
5. Tubular fluid in the ascending limb becomes hypotonic as it loses solutes.
6. Water leaves the descending limb by osmosis and NaCl enters the descending limb by
diffusion.
7. Tubular fluid in the descending limb becomes hypertonic as it loses water and gains NaCl.
8. As NaCl repeats the circuit, its concentration in the medulla increases.
9. The vasa recta countercurrent mechanism helps maintain the NaCl concentration in the
medulla.
I. Urea and Uric Acid Excretion
1. Urea is a by-product of amino acid catabolism in the liver.
2. Urea enters the renal tubule through filtration.
3. About 50% of urea is reabsorbed but the remainder is excreted in urine.
4. Uric acid is a product of the metabolism of certain nucleic acid bases.
5. Uric acid is completely reabsorbed.
6. About 10% of the reabsorbed uric acid ends up in urine because it is secreted into the renal
tubule.
J. Urine Composition
1. Urine is normally composed of water, urea, uric acid, creatinine, trace amounts of amino
acids and various electrolytes.
2. Factors that change urine composition are fluid intake, environmental temperature, relative
humidity of surrounding air, a person’s emotional condition, respiratory rate, and body
temperature.
K. Renal Clearance
1. Renal clearance is the rate at which a particular substance is removed from the plasma.
2. The inulin clearance test is used to calculate the rate of glomerular filtration.
3. The creatinine clearance test is used to calculate GRF and to determine amount of renal
failure.
4. The para-aminohippuric acid test is used to calculate the rate of plasma flow through the
kidneys.
IV. Elimination of Urine
A. Introduction
1. After forming in the nephrons, urine passes from the collecting ducts through openings in
renal papillae and enters the calyces of the kidney.
2. From the renal calyces, urine passes through the renal pelvis into a ureters, and into the
urinary bladder.
B. Ureters
1. Ureters are located posterior to the parietal peritoneum and parallel to the vertebral column.
In the pelvic cavity, they course forward and medially to join the bladder.
2. The three layers of the wall of a ureter are an inner mucous coat, a middle muscular coat, and
an outer fibrous coat.
3. Urine is moved through ureters by peristaltic waves.
4. A renal calculus is a kidney stone.
5. The effects of ureter obstruction are to stimulate constriction of the renal arterioles and to
reduce urine output.
C. Urinary Bladder
1. The urinary bladder is located within the pelvic cavity, posterior to the symphysis pubis and
inferior to the parietal peritoneum.
2. The trigone of the bladder consists of the opening of the urethra and the two openings of the
ureters.
3. The neck of the bladder is a funnel shaped extension of the bladder that contains the opening
into the urethra.
4. The four layers of the wall of the bladder are an inner mucous coat, a submucous coat, a
muscular coat, and an outer serous coat.
5. The mucous coat is composed of transitional epithelial cells.
6. The submucosa consists of connective tissue and elastic fibers.
7. The muscular coat is composed of smooth muscle fibers.
8. The detrusor muscle is the collection of smooth muscle fibers in the wall of the urinary
bladder.
9. The internal urethral sphincter is located in the neck of the bladder and functions to prevent
the bladder from emptying until the pressure within the bladder increases to a certain level.
10. The serous coat is composed of the parietal peritoneum.
D. Urethra
1. The urethra conveys urine from the bladder to the outside.
2. Urethral glands are located in the urethral wall and function to secrete mucus into the urethral
canal.
3. The external urethral sphincter is located as part of the urogenital diaphragm and functions to
voluntarily control urination.
4. The three parts of the male urethra are prostatic, membranous, and spongy.
E. Micturition
1. Micturition is urination.
2. The muscles that contract during micturition are the destrusor muscle, abdominal wall
muscles, pelvic floor muscles and the diaphragm.
3. The micturition reflex center is located in the sacral portion of the spinal cord.
4. The urgency to urinate occurs when the bladder wall distends as it fills with urine.
5. Micturition is usually under voluntary control because the external urethral sphincter is under
voluntary control.
V. Life-Span Changes
A. With age, changes of the kidneys include shrinkage, scarring, loss of glomeruli, and a decreases
ability to remove nitrogenous wastes and toxins.
B. Changes of the nephron include thickening of renal tubules, shortening of renal tubules, and a
decreased ability to clear drugs and other substances from the blood.
C. Changes of the bladder, ureters, and urethra include loss of elasticity.
D. Common reasons for incontinence are loss of muscle tone in the bladder, urethra, and ureters, and
the atrophy of bladder sphincters. In males, an enlarged prostate may lead to incontinence.
Chapter 13: Endocrine System
I. General Characteristics of the Endocrine System
A. The endocrine glands secrete hormones.
B. Hormones diffuse from interstitial fluids into the blood stream and eventually act on target cells.
C. Paracrine secretions are secretions that do not travel in the blood stream to their targets.
D. Autocrine secretions are secretions that affect the secreting cell itself.
E. Exocrine glands secrete substances into ducts.
F. Endocrine glands and their hormones control metabolic processes.
G. Endocrine hormones also play vital roles in reproduction, development, and growth.
H. The larger endocrine glands are the pituitary, thyroid, parathyroids, adrenals, and pancreas.
II. Hormone Action
A. Introduction
1. Hormones only affect their target cells.
2. Target cells have receptors for particular hormones.
B. Chemistry of Hormones
1. Introduction
a. Steroid hormones are synthesized from cholesterol.
b. Nonsteroid hormones are synthesized from amino acids.
2. Steroid Hormones
a. Steroids are lipids that include complex rings of carbon and hydrogen atoms.
b. Examples of steroid hormones are testosterone, estrogen, aldosterone, and cortisol.
3. Nonsteroid Hormones
a. Examples of hormones called amines are norepinephrine and epinephrine.
b. Protein hormones are composed of long chains of amino acids.
c. Examples of protein hormones are those secreted by the anterior pituitary and
parathyroid glands.
d. Hormones called glycoproteins are produced by the anterior pituitary.
e. Peptide hormones are short chains of amino acids.
f. Peptide hormones come from the posterior pituitary and hypothalamus.
g. Prostaglandins are paracrine substances and are produced in a wide variety of cells.
C. Actions of Hormones
1. Introduction
a. Hormones exert their effects by altering metabolic processes.
b. Hormones may reach all cells but only affect those that have appropriate receptors.
c. The more receptors the hormone binds on its target cell, the greater the response.
2. Steroid Hormones
a. Steroid hormones are insoluble in water but are soluble in lipids.
b. Steroid hormones can diffuse into cells relatively easily.
c. Once steroid hormones are inside a cell, they combine with specific protein receptors
located usually in the nucleus.
d. The binding of a steroid hormone to its receptor usually activates or inhibits a gene.
e. Activated genes code for specific proteins.
f. The new proteins may be enzymes, transport proteins, or hormone receptors and they
bring about cellular changes.
3. Nonsteroid Hormones
a. A nonsteroid hormone usually binds with receptors located on the cell membrane.
b. When a nonsteroid hormone binds to a membrane receptor, this causes the receptor’s
activity site to interact with other membrane proteins.
c. Receptor binding may alter the function of enzymes or membrane transport
mechanisms, changing the concentrations of still other cellular components.
d. A first messenger is the hormone.
e. Second messengers are the chemicals in the cell that induce the changes that are
recognized as responses to the hormone.
f. Many hormones use cyclic AMP as a second messenger.
g. G proteins are activated by the binding of a hormone to a membrane receptor.
h. Adenylate cyclase is activated by G proteins.
i. Adenylate cyclase functions to form cyclic AMP from ATP.
j. Cyclic AMP activates another set of enzymes called protein kinases.
k. Protein kinases function to transfer phosphate groups from ATP to proteins substrate
molecules.
l. Phosphorylated substrates may be converted from inactive to active forms.
m. Activated proteins then alter various cellular processes to bring about the effect of
that particular hormone.
n. Hormones whose actions depend upon cyclic AMP include releasing-hormones form
the hypothalamus, TSH, ACTH, FSH, LH, ADH, PTH, norepinephrine, epinephrine,
glucagon, and calcitonin.
o. An example of another second messenger is DAG.
p. In another mechanism, a hormone binding to its receptor increases calcium, ion
concentration within the target cell.
q. Calcium ions bind to the protein calmodulin to activate it.
r. Activated calmodulin functions to interact with enzymes, altering their activities.
s. Cells are highly sensitive to changes in concentration of nonsteroid hormones because
responses to them is greatly amplified through second messengers.
D. Prostaglandins
1. Prostaglandins are paracrine substances that act locally.
2. Some prostaglandins regulate cellular responses to hormones.
3. The variety of effects prostaglandins can produce include relaxation of smooth muscle in
airway and blood vessels, contraction of smooth muscle in the uterus, stimulation of secretion of
various hormones, and promotion of inflammation.
III. Control of Hormonal Secretions
A. Introduction
1. Hormones are continually excreted in urine and broken down by enzymes in the liver.
2. Increasing or decreasing blood levels of hormones requires increased of decreased secretion.
B. Control Sources
1. The hypothalamus controls the anterior pituitary gland’s release of tropic hormones.
2. Tropic hormones are those that stimulate other endocrine gland sto release hormones.
3. An example of an endocrine organ directly stimulated by the nervous system is the adrenal
medulla.
4. Some endocrine glands respond to changes in the composition of the internal environment.
5. As a result of negative feedback mechanisms, hormone levels remain relatively stable.
IV. Pituitary Gland
A. Introduction
1. The pituitary gland is located at the base of the brain.
2. The infundibulum is a stalk that attaches the pituitary gland to the hypothalamus.
3. The two portions of the pituitary are anterior and posterior.
4. The anterior lobe secretes the following hormones: GH, TSH, ACTH, FSH, LH, PRL.
5. The posterior pituitary secretes the following hormones: OT and ADH
6. The hypothalamus controls most of the pituitary gland’s activities.
7. The posterior pituitary receives impulses from the hypothalamus.
8. Releasing hormones from the hypothalamus control the anterior pituitary.
9. The hypophyseal portal veins are vessels that pass downward along the pituitary stalk from
the hypothalamus and give rise to a capillary be in the anterior lobe of the pituitary.
B. Anterior Pituitary Hormones
1. Somatotropes secrete GH.
2. Mammotropes secrete PRL.
3. Thyrotropes secrete TSH.
4. Corticotropes secrete ACTH.
5. Gonadotropes secrete FSH and LH.
6. Actions of growth hormone are stimulation of cells to enlarge and more rapidly divide,
enhance movement of amino acids through the cell membranes, and increases the rate of protein
synthesis. GH also decreases the rate as which cells utilize carbohydrates and increases the rate
at which cells use fats.
7. The secretion of GH is controlled by somatostatin and GHRH.
8. Actions of prolactin are to sustain mild production after birth and to amplify effect of LH in
males.
9. The secretion of PRL is controlled by PIH and PRF.
10. Actions of thyroid-stimulating hormone are to stimulate the thyroid gland to release its
hormones.
11. The secretion of TSH is controlled by TRH.
12. The actions of adrenocorticotropic hormone are to control secretion of certain hormone from
the adrenal cortex.
13. The secretion of ACTH is controlled by CRH.
14. Gonadotropins are LH and FSH.
15. The actions of follicle-stimulating hormone are to promote development of egg-containing
follicles in ovaries, to simulate follicular cells to releases estrogen, and in male, to stimulate
production of sperm cells.
16. The actions of luteinizing hormone are to promote secretion of sex hormones and to promote
the release egg cells in females.
17. The secretion of FSH and LH is controlled by GnRH.
C. Posterior Pituitary Hormones
1. The posterior pituitary consists of nerve fibers and neuroglial cells.
2. Specialized neurons in the hypothalamus produce two hormones called OT and ADH.
3. The hormones produced in the hypothalamus travel down axons through the pituitary stalk to
the posterior pituitary.
4. The actions of antidiuretic hormone are to cause a reduction in water excretion, and to raise
blood pressure.
5. The secretion of ADH is controlled by blood water concentration and blood volume.
6. The actions of oxytocin are to contact muscles in uterine wall and to contract muscles
associated with milk-secreting cells.
7. The secretion of oxytocin is controlled by uterine stretch and stimulation of breasts.
V. Thyroid Gland
A. Introduction
1. The thyroid gland consists of two lobes.
2. The thyroid gland is located just below the larynx on either side and anterior to the trachea.
B. Structure of the Gland
1. Follicles are secretory parts of the thyroid gland.
2. Colloid is a viscous fluid that fills follicles and contains thyroglobulin.
3. Thyroglobulin is a glycoprotein.
4. Extrafollicular cells are located outside of follicles.
5. The follicular cells produce hormones.
C. Thyroid Hormones
1. The three hormones produced by the thyroid gland are T4, T3, and calcitonin.
2. The actions of thyroxine and triiodothyronine are to regulate metabolism of carbohydrates,
lipids, and proteins.
3. The secretion of T3 and T4 are controlled by TSH.
4. Follicular cells require iodine to produce T3 and T4.
5. The actions of calcitonin are to lower blood calcium levels.
6. The secretion of calcitonin is controlled by blood calcium levels. It is released in response to
high blood calcium levels.
VII. Parathyroid Glands
A. Introduction
1. Parathyroid glands are located embedded in the thyroid gland.
2. Usually a person has four parathyroid glands.
B. Structure of the Glands
1. Each parathyroid gland is covered by a thin capsule.
2. The body of a parathyroid gland consists of many tightly packed secretory cells.
C. Parathyroid Hormone
1. The actions of PTH are to raise blood calcium levels.
2. The secretion of PTH is controlled by blood calcium levels. It is released in response to low
blood calcium levels.
VIII. Adrenal Glands
A. Structure of the Glands
1. The adrenal glands are shaped like pyramids.
2. The two parts of an adrenal gland are the cortex and medulla.
3. The adrenal medulla consists of irregularly shaped cells grouped around blood vessels.
4. The adrenal cortex is composed of closely packed masses of epithelial layers.
5. The three layers of the adrenal cortex are the outer zona glomerulosa, the middle zona
fasciculata, and the inner zona reticulairs.
B. Hormones of the Adrenal Medulla
1. The two hormones released by the adrenal medulla are epinephrine and norepinephrine.
2. The actions of epinephrine and norepinephrine are increased heart rate, increased force of
cardiac muscle contraction, elevated blood pressure, increased breathing rate and decreased
activity of the digestive system
3. The secretion of epinephrine and norepinephrine are controlled by the sympathetic nervous
system.
C. Hormones of the Adrenal Cortex
1. Introduction
a. The adrenal cortex produces more than 30 different steroids.
b. The most important adrenal cortical hormones are aldosterone, cortisol, and certain
sex hormones.
2. Aldosterone
a. Aldosterone is secreted by the zona glomerulosa and is called a mineralocorticoid
because it helps regulate the concentration of mineral electrolytes.
b. The actions of aldosterone are regulation of concentration of extracellular electrolytes
by conserving sodium ions and excreting potassium ions.
c. The secretion of aldosterone is controlled by electrolyte concentrations in body fluids
and the renin-angiotensin mechanism
3. Cortisol
a. Cortisol is secreted by the zona fascilulata and is called a glucocorticoid because it
affects glucose metabolism
b. The actions of cortisol are to decrease protein synthesis, increase fatty acid release,
and simulate glucose synthesis from noncarbohydrates.
c. The secretion of cortisol is controlled by CRH.
IX. Pancreas
A. Structure of the Gland
1. The pancreas is located posterior to the stomach.
2. The endocrine portion of the pancreas consists of islets of Langerhans which are also called
pancreatic islets.
3. Three cell types of the pancreatic islets are alpha, beta, and delta.
4. Alpha cells secrete glucagon.
5. Beta cells secrete insulin.
6. Delta cells secrete somatostatin.
B. Hormones of the Pancreatic Islets
1. The actions of glucagon are to stimulate the liver to break down glycogen and to convert
noncarbohydrates into glucose. It also simulated the breakdown of fats.
2. The secretion of glucagon is controlled by blood glucose concentrations.
3. The actions of insulin are to promote the formation of glycogen from glucose, to inhibit
conversion of noncarbohydrates into glucose, and to enhance movement of glucose through
adipose and muscle cell membranes. It also decreases blood glucose concentrations, promotes
transport of amine acids into cells, and enhances synthesis of proteins and fats.
4. The secretion of insulin is controlled by blood glucose concentrations.
5. The function of somatostatin is to help regulate carbohydrates.
X. Other Endocrine Glands
A. Pineal Gland
1. The pineal gland is located near the roof of the third ventricle.
2. The pineal gland produces the hormone melatonin.
3. The functions of melatonin are to help regulate circadian rhythms and to inhibit secretion of
gonadotropins.
B. Thymus gland
1. The thymus gland is located between the lungs.
2. The thymus gland secretes a group of hormones called thymosins.
3. The function of thymosin is to promote the maturation of T lymphocytes.
C. Reproductive Organs
1. Reproductive organs that secrete hormones are ovaries and testes.
2. Examples of hormones produced by reproductive organs are estrogen, progesterone, and
testosterone.
D. Other Hormone-Producing Organs
1. The hormone produced by the heart is ANP.
2. The hormone produced by the kidneys is erythropoietin.
Chapter 6: Skin and the Integumentary System
I. Skin and Its Tissues
A. Introduction
1. The skin is composed of several kinds of tissues.
2. Skin is a protective covering that prevents many harmful substances from entering the body.
3. Skin also retards water loss and helps regulate body temperature.
4. Skin houses sensory receptors and contains immune system cells.
5. Skin synthesizes vitamin D and excretes a small amount of waste products.
6. The two distinct layers of skin are epidermis and dermis.
7. The outer layer is called the epidermis and is composed of stratified squamous epithelium.
8. The inner layer is called dermis and is made up of connective tissues, epithelial tissue, muscle
tissue, nervous tissue, and blood.
9. A basement membrane separates the two skin layers.
10. The subcutaneous layer is beneath the dermis.
11. The subcutaneous layer is composed of loose connective tissues and adipose.
B. Epidermis
1. The epidermis lacks blood vessels.
2. The deepest layer of the epidermis is called the stratum basale.
3. The stratum basale is nourished by blood vessels in the dermis.
4. Cells of the stratum basale can divide and grow because they are nourished so well.
5. When new cells enlarge they push old epidermal cells away from the dermis toward the
surface of skin.
6. The farther the cells travel, the poorer their nutrient supply becomes and eventually they die.
7. Older skin cells are called keratinocytes and are held together with desmosomes.
8. Keratinization is the accumulation of keratin in epidermal cells which hardens the epidermis.
9. As a result of keratinization many layers of tough, tightly packed cells
accumulate in the epidermis.
10. The outermost layer of the epidermis is called the stratum corneum.
11. The epidermis is thickest on palms of the hand and the soles of the feet.
12. Most areas of epidermis have 4 layers.
13. The four layers starting with the deepest are stratum basale, stratum spinosum, stratum
germinativum, and stratum corneum.
14. An additional layer called stratum lucidum is in thickened skin.
15. In healthy skin, production of epidermal cells
is balanced with loss of dead cells from the stratum corneum.
16. The rate of cell division increases where the skin is frequently rubbed or pressed.
17. Calluses are a thickening of the stratum corneum.
18. Corns are keratinized conical masses on the toes.
19. Specialized cells in the epidermis called melanocytes.
produce melanin.
20. Melanin provides skin color and absorbs UV radiation.
21. Melanocytes lie in the stratum basale and
in the underlying connective tissues of the dermis.
22. The extensions of melanocytes transfer melanin granules to epidermal cells by a process
called cytocrine secretion.
C. Dermis
1. The boundary between the dermis and epidermis is uneven because
the epidermis
projects inward and the dermis has papillae between the ridges of the epidermis.
2. Fingerprints form from the undulations of the dermis and epidermis.
3. The dermis binds the epidermis to the subcutaneous layer.
4. The dermis is largely composed of irregular dense connective tissue that includes tough
collagenous fibers and elastic fibers in a gel-like ground substance.
5. The dermis also contains smooth muscles that can wrinkle the skin of the scrotum.
6. Some smooth muscle of the skin is associated with hair follicles.
7. In the face, skeletal muscles are anchored to the dermis.
8. Nerve cell processes are scattered throughout the dermis.
9. Pacinian corpuscles are stimulated by heavy pressure.
10. Meissner’s corpuscles are stimulated by light touch.
D. Subcutaneous Layer
1. The subcutaneous layer consists of loose connective tissue and adipose tissue.
2. No sharp boundary separates the dermis and subcutaneous layer because the fibers of the
dermis are continuous with the fibers of the subcutaneous layer.
3. The adipose tissue of the subcutaneous layer insulates the body.
4. The subcutaneous layer contains major blood vessels that supply the skin.
II. Accessory Organs of the Skin
A. Hair Follicles
1. Hair is present on all skin surfaces except the palms, soles, lips, nipples, and parts of external
reproductive organs.
2. A hair follicle is a group of epidermal cell at the base of a tubelike depression in the dermis of
skin.
3. A follicle extends from the surface of skin into the dermis.
4. The hair root is the portion of hair embedded in skin.
5. The hair papilla is a projection of connective tissue at the end of the hair follicle. It contains
blood vessels.
6. The hair shaft is the portion of hair that extends from the surface of skin.
7. A hair is composed of dead keratinocytes.
8. Baldness results when hairs fall out and are not replaced.
9. Genes determine hair color by directing the type and amount of pigment that epidermal
melanocytes produce.
10. Dark hair has more melanin than blond hair.
11. White hair of albinos lack melanin.
12. Red hair contains an iron pigment called trichosiderin.
13. Hairs appear gray from a mix of pigmentation and unpigmentation.
14. An arrector pili muscle is a band of smooth muscle and attaches to hair follicles.
15. Goose bumps are produced when arrector pili muscles contract.
B. Nails
1. Nails are protective coverings on the ends of fingers and toes.
2. Each nail consists of a nail plate that overlies a surface of skin called the nail bed.
3. The lunula of a nail is the whitish, thickened, half-moon shaped region at the base of a nail
plate.
C. Skin Glands
1. Sebaceous glands contain groups of specialized epithelial cells and are associated with hair
follicles.
2. Sebaceous glands are holocrine glands and their cells produce sebum.
3. Sebum is a mixture of fatty material and cellular debris.
4. Sebum is secreted into hair follicles and helps keep hair and skin soft and pliable.
5. Sebaceous glands are not found on palms and soles.
6. Sebaceous glands open directly onto skin in some regions, such as, the lips, corners of the
mouth, and parts of the external reproductive organs.
7. Sweat glands are also called sudoriferous glands.
8. Each sweat gland consists of a tiny tube in the dermis or superficial subcutaneous layer.
9. The most numerous sweat glands are eccrine.
10. Eccrine glands respond to heat.
11. Eccrine glands are common on the forehead, neck, and back.
12. A pore is the opening of a sweat gland duct.
13. Sweat contains water, wastes, and salts.
14. Apocrine glands become active at puberty.
15. They can wet certain areas of skin when a person is nervous or stressed.
16. Apocrine glands are most numerous in the axilla, groin, and around the nipples.
17. Ceruminous glands of the external ear canal and secrete cerumen.
18. Mammary glands secrete milk.
III. Regulation of Body Temperature
A. Introduction
1. Regulation of body temperature is important because even slight shifts can disrupt the rates of
metabolic reactions.
2. A normal temperature of deeper body parts remains close to 37oC.
B. Heat Production and Loss
1. Heat is a product of cellular metabolism.
2. When body temperature rises above the set point, nerve impulses stimulate structures in the
skin and other organs to release heat.
3. During physical activity, active muscles release heat, which the blood carries away.
4. When warmed blood reaches the hypothalamus, muscles in the walls of dermal blood vessels
relax.
5. As dermal blood vessels dilate, heat escapes to the outside world.
6. Skin reddens because dermal blood vessels are dilated.
7. The primary means of body heat loss is radiation.
8. Radiation is the spread of heat from warm areas to cooler areas.
9. Conduction is the movement of heat into molecules of cooler objects.
10. Convection is the continuous circulation of air over a warm surface.
11. Evaporation is the change of a liquid to a gas.
12. When sweat evaporates, it carries heat away from the skin surface.
13. When body temperature falls below the set point, muscles of dermal blood vessels constrict
which decreases the flow of blood through the skin.
14. When body temperature falls, sweat glands become inactive.
15. When body temperature continues to fall, small groups of muscles to contract slightly to
produce shivering.
C. Problems in Temperature Regulation
1. Hyperthermia is a rise in body temperature.
2. If air temperature is high, heat loss by radiation is less effective.
3. Hypothermia is a low body temperature.
4. Hypothermia can result from prolonged exposure to cold or an illness.
5. Hypothermia can lead to mental confusion, lethargy, and loss of consciousness.
6. Children and the elderly are at a higher risk for developing hypothermia.
IV. Skin Color
A. Genetic Factors
1. Regardless of racial origin, all people have about the same number of melanocytes in their
skin.
2. Differences in skin color result from the differences in the amount of melanin melanocytes
produce.
3. The more melanin produced, the darker the skin.
4. The distribution and size of pigment granules within melanocytes also influence skin color.
B. Environmental Factors
1. Environmental factors such as sunlight and X rays affect skin color.
2. These factors stimulate melanocytes to produce more pigment.
3. Tans fade as pigmented epidermal cells become keratinized and wear away.
C. Physiological Factors
1. When blood is well oxygenated, the blood pigment hemoglobin is bright red and the skin of
light-complexioned people appears pink.
2. When blood oxygen concentration is low, hemoglobin is dark red and the skin appears bluish.
3. If dermal blood vessels are dilated, more blood enters skin and skin appears pinkish or
reddish.
4. If dermal blood vessels are constricted, less blood enters skin and skin appears pale.
5. Carotene is a yellow-orange pigment found in certain vegetables.
6. Carotene can give skin a yellowish color.
V. Healing of Wounds and Burns
A. Introduction
1. Inflammation is a normal response to injury or stress.
2. During inflammation, blood vessels dilate and become more permeable.
3. Inflamed skin may become reddened, swollen, warm, and painful to the touch.
4. The dilated blood vessels provide the tissues with more nutrients,
which aids healing.
5. The specific events of healing depend on the nature and extent of the injury.
B. Cuts
1. If a break in the skin is shallow, epithelial cells are stimulated to divide more rapidly than
normal.
2. If a cut extends into the dermis or subcutaneous layer, blood vessels break and the escaping
blood forms a clot.
3. A clot consists mainly of fibrin, plasma, blood cells, and platelets.
4. A scab is a blood clot and dried fluids.
5. Fibroblasts migrate into the injured area and begin forming new fibers that bind the edges of
the wound together.
6. Connective tissue matrix secretes growth factors that stimulate certain cells to divide and
regenerate damaged tissues.
7. As healing continues, blood vessels extend into the area beneath the scab.
8. Phagocytic cells remove dead cells and other debris.
9. A scar results when the wound is extensive.
10. A granulation consists of a branch of a blood vessel, and a cluster of collagen-secreting
fibroblasts.
C. Burns
1. A first degree burn is one that only affects the epidermis.
2. A second degree burn is that affects a part of the dermis and epidermis.
3. Blisters appear in second degree burns.
4. The healing of second degree burns depends on accessory organs of the skin that survive the
burn.
5. A third degree burn is one that affects the entire thickness of skin.
6. In a third degree burn, the skin becomes dry and leathery.
7. If a third degree burn is extensive, treatment may involve removing a thin layer of skin from
an unburned region of the body and transplanting it to the injured area.
8. An autograft is a graft from the same person.
9. A homograft is a graft from a cadaver.
10. Skin substitutes include amniotic membranes, membranes of silicon, polyurethane or nylon.
11. The treatment of a burn patient requires estimating the extent fo the body’s surface that is
affected.
12. To estimate, physicians use the rule of nines.
13. This rule divides the skin’s surface into 11 areas of 9% each.
VI. Life-Span Changes
A. Aging skin affects appearance, temperature regulation and vitamin D production.
B. Age spots or liver spots are patches of pigments.
C. The dermis becomes reduced as synthesis of the connective tissue proteins collagen and
elastin slows.
D. Wrinkling and sagging skin result from the shrinking of the dermis and loss of fat from the
subcutaneous layer.
E. Skin becomes drier because sebaceous glands produce less oil.
F. Slowed melanin production causes gray or white hair.
G. Nail growth is impaired because the blood supply to the nails is diminished.
H. Sensitivity to pain and pressure diminishes with age.
I. An older person is less able to tolerate heat because the sweat glands and hair follicle shrink,
and the number of dermal blood vessels decrease.
J. Vitamin D is necessary for calcium absorption.
Chapter 7: Skeletal System
I. Bone Structure
A. Bone Classification
1. The four classes of bone according to shape are long, short, flat, irregular., and sesamoid.
B. Parts of a Long Bone
1. An expanded end of a long bone is an epiphysis.
3. Articular cartilage is located on an epiphysis.
4. The shaft of a long bone is called a diaphysis.
5. Periosteum is a tough, vascular, fibrous membrane covering the diaphysis of a bone.
7. Processes provide sites for attachments of tendons or ligaments.
8. The wall of the diaphysis is composed of compact bone.
10. The epiphyses are largely composed of spongy bone.
C. Microscopic Structure
1. Introduction
a. Youthful bone cells are called osteoblasts.
b. Mature bone cells are called osteocytes.
c. Bone cells that crush bone tissue are called osteoclasts.
d. Lacunae are tiny, chambers that contain osteocytes.
II. Bone Development and Growth
B. Intramembranous Bones
1. Examples of intramembranous bones are flat bones of the skull, the clavicle and the mandible
C. Endochondral Bones
1. Most of the bones of the skeleton are endochondral bones.
2. Endochondral bones develop as masses of hyaline cartilage
C. Blood Cell Formation
1. Hematopoiesis is blood cell formation.
6. Red marrow occupies the cavities of most bones in an infant..
8. Yellow marrow stores fat.
Chapter 9: Muscular System
I. Structure of a Skeletal Muscle
B. Connective Tissue Coverings
1. Fascia is dense connective tissue that separates individual skeletal muscles.
2. A tendon is a cordlike structure that consists of dense connective tissue.
3. Tendons connect a muscle to a bone.
4. An aponeurosis is a sheetlike structure composed of dense connective tissue.
5. Epimysium is a layer of connective tissue that closely surrounds a skeletal muscle.
6. Perimysium is connective tissue that separates muscles into fascicles.
7. A fascicle is a section of a muscle.
8. Endomysium is connective tissue that surrounds individual muscle cells.
C. Skeletal Muscle Fibers
1. A skeletal muscle fiber is a single muscle cell.
2. The sarcolemma is the plasma membrane of a muscle cell.
3. The sarcoplasm is the cytoplasm of a muscle cell..
5. Myofibrils are threadlike structures and are located in the sarcoplasm..
7. Thick myofilaments are composed of myosin.
8. Thin myofilaments are composed of actin.
9. The organization of myofilaments produces the alternating light and dark striation characteristic of skeletal muscles.
21. Actin has a binding site to which the cross-bridges of a myosin molecule can attach.
22. Troponin and tropomyosin associate with actin filaments.
23. Sarcoplasmic reticulum is endoplasmic reticulum of a muscle fiber.
24. Transverse tubules are membranous channels that extend into the sarcoplasm as invaginations continuous with the
sarcolemma and contains extracellular fluid.
25. Cisternae are enlarged portions of sarcoplasmic reticulum
II. Skeletal Muscle Contraction
A. Neuromuscular Junction
4. A neuromuscular junction is where the axon and muscle fiber meet.
5. A motor end plate is a specialized portion of the muscle cell membrane that is extensively folded.
6. A motor unit is a motor neuron and the muscle fibers it controls.
7. A synaptic cleft separates the membranes of the neuron and the membrane of the muscle fiber.
8. Synaptic vesicles store neurotransmitters.
6. ATP is necessary for both muscle contraction and relaxation
G. Energy Sources for Contraction
1. Creatine phosphate is an energy source available to generate ATP from ADP.
I. Oxygen Debt
2. Under anaerobic conditions, glycolysis breaks down glucose into pyruvic acid and converts it to lactic acid..
4. Liver cells can convert lactic acid to glucose.
B. Origin and Insertion
1. The origin of a muscle is the immovable end of the muscle.
2. The insertion of a muscle is the movable end of a muscle.
3. When a muscle contracts, its insertion is pulled toward its origin.
Chapter 17: Digestive System
I. Introduction
B. Mechanical digestion breaks large pieces of food into smaller ones without altering their chemical composition.
C. Chemical digestion breaks down food into simpler chemicals.
E. The alimentary canal is composed of the mouth, pharynx, esophagus, stomach, small and large intestine, and anal canal.
F. The accessory organs of the digestive system are salivary glands, liver, gallbladder, and pancreas.
II. General Characteristics of the Alimentary Canal
C. Movements of the Tube
3. Peristalsis is a wavelike motion.
III. Mouth
A. Introduction
1. The functions of the mouth are to receive food and to begin digestion.
2. Mastication is chewing.
4. The oral cavity is the space between the tongue and palate.
C. Tongue
1. The tongue is located in the floor of the oral cavity.
D. Palate
1. The palate forms the roof of the oral cavity and consists of a hard part and a soft part.
4. The uvula is a downward extension of the soft palate.
5. The function of the uvula is to prevent food or liquids from entering the nasal cavity.
IV. Salivary Glands
A. Introduction
1. Salivary glands secrete saliva.
2. The functions of saliva are to moisten food, bind food together, and begin the chemical digestion of carbohydrates.
V. Pharynx and Esophagus
A. Introduction
1. The pharynx is a cavity posterior to the nasal and oral cavities.
D. Esophagus
1. The esophagus is a passageway for food.
4. The esophageal hiatus is an opening in the diaphragm.
6. The lower esophageal sphincter is located where the esophagus and stomach join and prevents regurgitation of food.
VII. Stomach
A. Introduction
3. Rugae are thick folds in the lining of the stomach.
4. The functions of the stomach are to mix food with gastric juice, begin protein digestion, to begin a small amount of absorption, and
movement of food into the small intestine.
B. Parts of the Stomach
1. The four parts of the stomach are cardiac portion, body, fundus, and pylorus.
2. The cardiac region is the region near the esophageal opening.
3. The fundic region is a pouch that extends superior to the cardiac portion.
4. The body of the stomach is the main part of the stomach.
5. The pyloric region is the narrow region that is continuous with the small intestine.
6. The pyloric sphincter is located between the pylorus and the duodenum and functions to control the movement of food into the
small intestine.
C. Gastric Secretions
1. Gastric pits are openings of gastric glands.
2. The three cell types of gastric glands are parietal, chief, and mucous.
3. Mucous cells secrete mucus.
4. Chief cells secrete digestive enzymes.
5. Parietal cells secrete hydrochloric acid and intrinsic factor.
6. Gastric juice is a mixture of the secretions of mucous, parietal, and chief cells.
7. Pepsin is an enzyme that digests proteins.
8. The function of pepsinogen is to be converted to pepsin when needed.
9. The function of hydrochloric acid in the stomach is to convert pepsinogen into pepsin and to destroy pathogens.
10. The coating of the stomach is important for protecting the stomach wall from digestive enzymes and acids.
11. The function of intrinsic factor is to enhance the absorption of vitamin B12.
E. Gastric Absorption
1. The stomach absorbs alcohol, some drugs, salts, and a small amount of water.
2. Most nutrients are absorbed in the small intestine.
F. Mixing and Emptying Actions.
2. Chyme is food substances that have been mixed with gastric juice.
3. Peristaltic waves push chyme toward the pylorus of the stomach.
5. The lower esophageal sphincter prevents regurgitation of food.
VIII. Pancreas
B. Pancreatic Juice
1. Pancreatic juice contains many enzymes and bicarbonate ions.
2. The function of pancreatic amylase is to digest carbohydrates.
3. The function of pancreatic lipase is digest lipids.
4. The functions of trypsin, chymotrypsin, and carboxypeptidase are to digest proteins.
6. The function of trypsinogen is to be converted to trypsin.
7. The functions of nucleases are to digest nucleic acids.
C. Regulation of Pancreatic Secretion
2. The function of secretin is to stim. the pancreas to release pancreatic juice with a high concentration of bicarbonate ions.
3. The release of cholecystokinin is triggered by the presence of chyme in the small intestine.
4. The action of cholecystokinin on the pancreas is to release panc. juice that has a high concentration of digestive enzymes.
IX. Liver
A. Introduction
1. The largest internal organ is the liver.
B. Liver Structure
C. Liver Functions
8. The liver’s role in digestion is to produce and secrete bile.
D. Composition of Bile
2. Bile contains water, bile salts, bile pigments, cholesterol, and electrolytes.
E. Gallbladder
1. The gallbladder is located inferior to the liver.
2. The cystic duct is the duct of the gallbladder and opens into the common bile duct.
3. The common bile duct is formed from the cystic duct and common hepatic duct and opens into duodenum.
4. Gallstones form when bile is too concentrated.
F. Regulation of Bile Release
1. Cholecystokinin triggers the gallbladder to release bile.
2. Cholecystokinin is released in response to presence of lipids and proteins in the small intestine.
G. Functions of Bile Salts
2. Emulsification is the breaking of fat globules into smaller droplets.
X. Small Intestine
A. Introduction
1. The small intestine extends from the stomach to the large intestine.
B. Parts of the Small Intestine
1. The three parts of the small intestine are duodenum, jejunum, and ileum.
C. Structure of the Small Intestinal Wall
1. The velvety appearance of the inner wall of the small intestine is due to intestinal villi.
2. Intestinal villi are tiny projections of the mucosa of the small intestine.
3. The functions of villi are to increase the surface area of the lining of the small intestine.
6. Microvilli increase the surface area intestinal cells.
F. Absorption in the Small Intestine
1. The most important absorbing organ is the small intestine.
4. A peristaltic rush is the rapid sweeping of chyme into the large intestine.
5. Diarrhea results from a peristaltic rush.
6. The ileocecal sphincter joins the ileum and cecum.
XI. Large Intestine
A. Introduction
2. The functions of the large intestine are to form feces, eliminate solid wastes, and to absorb remaining water and electrolytes from
chyme.
B. Parts of the Large Intestine
1. The parts of the large intestine are cecum, colon, rectum, and anal canal.
2. The cecum is the initial portion of the large intestine.
3. The vermiform appendix is located off the cecum and consists of lymphatic tissue.
4. The four parts of the colon are ascending colon, transverse colon, descending colon, and sigmoid colon.
9. The rectum is the continuation of the sigmoid colon.
10. The anal canal is the continuation of the rectum.
12. The anus is the opening of the anal canal.
13. Two sphincters of the anus are the internal and external.
14. The internal anal sphincter is composed of smooth muscle.
15. The external anal sphincter is composed of skeletal muscle.
D. Functions of the Large Intestine
4. The large intestine can absorb water and electrolytes.
Chapter 10: Nervous System I
I. General Functions of the Nervous System
A. The nervous system is composed predominately of nervous tissue but also includes some blood vessels and connective
tissue.
B. Two cell types of nervous tissue are neurons and neuroglial cells.
C. Neurons are specialized to react to physical and chemical changes in their surroundings.
D. Dendrites are small cellular processes that receive input.
E. Axons are long cellular processes that carry information away from neurons.
F. Nerve impulses are bioelectric signals produced by neurons.
G. Bundles of axons are called nerves.
H. Small spaces between neurons are called synapses.
I. Neurotransmitters are biological messengers produced by neurons.
J. The central nervous system contains the brain and spinal cord.
K. The peripheral nervous system contains cranial and spinal nerves.
N. Receptors gather information.
O. Receptors convert their information into nerve impulses, which are then transmitted over peripheral nerves to the
central nervous system.
R. The motor functions of the nervous system use neurons to carry impulses from the central nervous system to effectors.
S. Examples of effectors are muscles and glands.
T. The two divisions of the motor division are somatic and autonomic.
U. Somatic nervous system is involved in conscious activities.
V. The autonomic nervous system is involved in unconscious activities.
W. The nervous system can detect changes in the body, make decisions, and stimulate muscles or glands to respond.
X. The three parts all neurons have are cell body, axon, and dendrites.
II. Classification of Neurons and Neuroglia
A. Classification of Neurons
1. The three major classifications of neurons based on structural differences are bipolar, multipolar, and unipolar.
2. Bipolar neurons have two processes; one process is a dendrite and the other an axon.
3. Bipolar neurons are found within the eyes, ears, and nose.
4. Unipolar neurons have one process which divides into an axon and a dendrite
7. Multipolar neurons have multiple dendrites and one axon.
8. Multipolar neurons are located in the brain and spinal cord.
9. The three classes of neurons based on functional differences are sensory, motor, and interneurons.
10. Sensory neurons carry impulses from peripheral body parts to the brain and spinal cord.
11. Sensory neurons have specialized receptors ends at the tips of their dendrites.
12. Most sensory neurons are unipolar but some are bipolar.
13. Interneurons are located in the brain and spinal cord.
14. Interneurons are multipolar and form links between other neurons.
15. Motor neurons carry nerve impulses from the brain and spinal cord to effectors.
B. Classification of Neuroglial Cells
3. Schwann cells are the neuroglia of peripheral nervous system.
4. The four neuroglial cells of the CNS are astrocytes, oligodendrocytes, microglial cells, and ependymal cells.
5. Astrocytes are star shaped and are commonly found between neurons and blood vessels.
6. Astrocytes provide support and hold structures together.
9. Astrocytes play a role in the blood-brain barrier, which restricts movement of substances between the blood and CNS.
10. Oligodendrocytes occur in rows along myelinated axons and form myelin in the brain and spinal cord.
11. Unlike Schwann cells, oligodendrocytes do not form neurilemmal sheaths.
12. Microglia function to support neurons, and phagocytize bacterial cells and cellular debris.
13. Ependyma form the inner lining of the central canal of the spinal cord and ventricles of the brain.
16. Covering the choroids plexus, ependymal cells also regulate the composition of the cerebrospinal fluid.
III. Cell Membrane Potential
A. Introduction
1. Polarized means electrically charged.
2. When a cell membrane is polarized, the inside is negatively charged with respect to the outside.
3. The polarization of a cell membrane is due to an unequal distribution of positive and negative ions on either side of the
membrane.
B. Distribution of Ions
1. Potassium ions are the major intracellular positive ion and sodium ions are the major extracellular cation.
2. The distribution of potassium and sodium is largely created by the sodium-potassium pump.
C. Resting Potential
1. A resting nerve cell is one that is not being stimulated to send a nerve impulse.
2. At rest, a cell membrane gets a slight surplus of positive charges outside, and inside reflects a slight negative surplus of
impermeable negatively charged ions because the cell membrane is more permeable to potassium ions than sodium ions.
Also the cell may contain anions and proteins that are negatively charged that cannot diffuse out of the cell.
3. The cell uses ATP to actively transport sodium and potassium ions in opposite directions.
6. The membrane potential is the potential difference across the cell membrane and is measured in millivolts.
7. Resting potential is the membrane potential of a resting neuron and has a value of –70 millivolts.
8. The negative sign of a resting membrane potential is relative to the inside of the cell and is due to the excess negative
charges on the inside of the cell membrane.
E. Action Potentials
3. At the resting membrane potential, sodium channels are closed but when threshold is reached, sodium channels open.
4. As sodium ions rush into the cell, the membrane potential changes and temporarily becomes positive on the inside.
5. When sodium channels close and potassium channels open, potassium diffuses out across the membrane and the inside
of the membrane becomes negatively charged again.
6. Repolarized means the membrane polar again or returned to its original resting state.
7. Axons are capable of action potentials but the cell body and dendrites are not.
8. A nerve impulse is the propagation of action potentials along an axon.
H. Impulse Conduction
1. Myelin serves as an insulator.
2. Saltatory conduction is the type of nerve impulse conduction that occurs only at nodes.
3. Myelinated axons exhibit salutatory conduction.
4. Myelinated axons send nerve impulses faster than unmyelinated axons.
5. The diameter of an axon also affects the speed of a nerve impulse.
Special Senses
F. Sense of Sight
a. Each eyelid is composed of skin, muscle, connective tissue, and conjunctiva.
b. The orbiculais oculi muscle functions to close the eyelids.
c. The levator palpebrae muscle functions to raise the upper eyelids.
k. The six extrinsic muscles of the eye are superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique,
and inferior oblique.
3. Structure of the Eye
a. The three layers of the eyeball are outer fibrous, middle vascular, and inner nervous.
c. The two parts of the outer tunic are the cornea and sclera.
i. The ciliary body is the thickest part of the middle layer and forms a ring around the front of the eye and its functions
include holding and moving the lens.
l. Suspensory ligaments extend from the ciliary processes and hold the lens in position.
p. The iris is a thin diaphragm and functions to control the amount of light that enters the eye.
q. The anterior cavity of the eye is the portion of the eye in front of the lens.
r. The anterior chamber of the eye is the portion of the eye in front of the iris.
s. The posterior chamber of the eye is the portion of the eye between the iris and lens.
t. Aqueous humor is located in the anterior cavity of the eye and functions to provide nutrients to surrounding tissues.
u. The pupil is a hole in an iris.
v. The size of the pupil changes in response to light intensity.
w. The inner tunic of the eye consists of the retina which contains the visual receptor cells.
x. The retina has distinct layers including pigmented epithelium, neurons, nerve fibers, and limit in membranes.
bb. The macula lutea is yellowish spot in the center of the retina.
cc. The fovea centralis is a depression in the center of the macula lutea.
dd. The optic disc is where axons from the retina exit the eye.
ee. The posterior cavity is the portion of the eye behind the lens.
ff. Vitreous humor is located in the posterior cavity and functions to support the internal eye structures and helps maintain
its shape.
5. Visual Receptors
a. Two kinds of photoreceptor cells are rods and cones.
b. Rods and cones are found in a deep layer of the retina.
c. Rods and cones are stimulated when light reaches them.
d. Rods are more sensitive to light than cones.
e. Rods provide vision in dim light.
f. Rods produce colorless vision, whereas cones detect colors.
i. Erythrolabe is most sensitive to red light waves.
j. Chlorolabe is most sensitive to green light waves.
k. Cyanolabe is most sensitive to blue light waves.
G. “Floaters” are due to crystal-like deposits in the vitreous humor.
I. Glaucoma is increased pressure in the eye due to accumulation of aqueous humor.
J. Cataracts are eye disorders in which the lenses become clouded and somewhat opaque.
.