Download Keshara Senanayake Kraus notes Chapter 9 (what we used to

Keshara Senanayake
Kraus notes
Chapter 9 (what we used to answer pg 186/187 for homework)
-An organism constantly responds to changes in its external and internal environment
>a principle of homeostasis is that the internal environment is stable in spite of changes in the external
environment
>responses usually involve several of the life processes and systems of the body
>these various responses must be coordinated (work together to produce homeostasis)
>these responses must be controlled in amount and direction.
>the coordination of life activities is called regulation
>multicellular animals accomplish regulation via the nervous and endocrine system
>the endocrine system functions by chemical means
>A stimulus is a change in the environment that causes changes or activity in an organism
>can be physical or chemical in nature
>examples: changes in temperatures, pressure, light, sound, and chemical environment
The action or movement resulting from a stimulus is a response
>one-celled organisms respond directly
>in multicellular has multiple steps
>the electrical and chemical nature of the impulse is the same, regardless of the stimulus
-A receptor is specialized nerve tissue that is sensitive to a specific stimulus.
>some receptors are simple nerve endings --> others organs
-each receptor is stimulated by a specific stimuli
-Effectors are parts of the body that respond --> muscles or glands
-The neuron or nerve cell is the basic unit of the nervous system.
>can be very long --> has three main parts.
>cyton (cell body) the axon and the terminal branches
>cyton has the nucleus and much cytoplasm. It has branched extensions called dendrites that receive
stimuli and send impulses to the cyton. From the cyton, the impulses pass along the axon.
--> axons are covered by myelin (fatty) sheaths. It is formed from cells that wraps itself around the axon.
>it helps speed the passage of impulses --> axons terminates with the terminal branches
The 3 types of neurons and their functions are illustrated in the reflex arc. --> pathways of impulses that
occurs in the simple type of behavior known a reflex.
Stimulus --> receptor --> sensory neuron --> synapse --> interneuron --> motor neuron --> effectors
Nerves are composed or bundles of axons/dendrites of many neurons (covered w/ connective tissues)
>Nerves with sensory neurons --> sensory nerves
>Nerves with motor neurons --> motor nerves
>Nerves with both --> mixed nerves
Nerve impulse is a series of electrochemical changes that proceed along the membrane of a neuron.
>the electrical aspect of an impulse involves a reversal of positive and negative charges on the outside and
inside surfaces of the neuron’s cell membrane. The chemical aspect involves the diffusion of sodium (Na+)
ions and potassium (K+) ions through the cell membrane.
>resting membrane is a polarized membrane (inside negative and outside positive)
>when the impulse has passed a part of an axon and has returned to its original condition it is called the
repolarized membrane
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-impulse passes along the membrane as a wave of depolarization in the membrane
-Changes of Na+ and K+ causes the electrical charges.
>on the polarized membrane active transport moves Na+ inside --> to out
>K+ ions move outside to inside
>called Na+/K+ pump
-It creates a high concentration of Na+ outside and K+ outside
>axon membrane is more permeable to K+ than to Na+ so K+ diffuses inside to outside
>outward diffusion of K+ builds excess (+) charge outside
>A sudden change in the permeability (causes by the impulse) of the membrane allows Na+ ions to go back
inside. Enough Na+ diffuses into axon to reverse the balance of electrical charge and depolarize the
membrane. Then K+ diffuses from inside to outside sufficiently to restore the positive charge outside the
membrane. --> the Na+/K+ pump is restored and ion concentrations return to their original state.
>depolarization lasts for a fraction of a millisecond
>a stimulus must be sufficient enough to exceed the threshold (initial barrier) to its passage
>once exceeded each impulse is same strength and speed
>a stimulus of greater strength initiates a train of more frequent impulses
>results in the production of a sufficient chemical to exceed the threshold of the next neurons
># of impulses per second (not variation in speed/strength) that determines the intensity of a response
>acetylcholine was the first neurotransmitter discovered
>a neurotransmitter is a chemical messenger secreted by a neuron at the terminal branches of an axon
>it diffuses across a synapse to affect the next neuron in a pathway
>or it diffuses from the terminal branches to affect a muscle
>two common neurotransmitters are acetylcholine and noradrenaline (is a neurotransmitter and a hormone)
How do pulses pass from one neuron to another?
-terminal branches of the first neuron have tiny cavities that store a neurotransmitter (such as acetylcholine)
>when the wave of depolarization reaches these cavities they release their neurotransmitters
>the neurotransmitters diffuse across the synapse and reach the dendrites of the second neuron
>they combine with receptor molecules on the surface of the dendrite membrane
>when sufficient neurotransmitters molecules accumulate, they initiate a new wave of depolarization in the
2nd neuron
>impulses cross the synapse in one direction --> terminal branches --> dendrites
Two nerve endings leading to the same organ can have opposite effects
>one nerve ending can release acetylcholine and the other can release noradrenaline
>in the example in the book acetylcholine is released by the vagus nerve to inhibit heart muscle
>noradrenaline from the accelerator nerve excited heart muscle
>It is the target organ not the neurotransmitter that determines response!
>is acetylcholine released at the synapses were not rapid destroyed --> muscle spasms/paralysis
>hydrolyzed by cholinesterase
---------------------------------------Irritability --> capacity to respond to stimuli
>basic properties of protoplasm
-It responds to small food particles or certain chemicals with feeding behavior
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>the nervous system of the hydra consists of a network of neurons called a nerve net
>impulses gradually spread throughout the body
>nematocyst (stinging cells) of hydra are struck by a living water flea, the threads injects paralyzing
chemicals into the prey. The prey releases glutathione which acts as a stimulus for initiating hydra’s
feeding reflex
>earthworms have a central nervous system
-this system passes impulses quickly over a definite pathway from receptors to effectors. The earthworms
CNS consists of a simple dorsal brain and a solid ventral nerve cord
>earthworms also have a peripheral nervous system --> consists of nerves that branches out from the CNS
to all parts of the body
>carries impulses
-Tiny swelling glands visible in each segment of the nerve cord are ganglia. Each ganglion consists of the
cell bodies of a group neurons. Thus, ganglia are tiny nerve control centers
>receives sensory impulses and relay impulses
>a pair of solid large ganglia above (dorsal to) the pharynx is the earthworms brain
>brain is simple but --> causes contraction and relaxations of muscles that move setae (bristles) in the front
and rear portions of the body
>contractions of one --> leads to another. This aspect of locomotion needs spinal NO BRAIN NEEDED
>hydra is radially symmetrical --> earthworm is bilaterally symmetrical
>means right and left sides are copies of each other
>also have a head (cephalic) that proceeds first
>grasshopper is far more active and responsive than the earthworm, its more complex nervous system
follows the same general invertebrate pattern
>has solid ventral nerve cord
>ganglia in the ventral nerve cord serve as segmental control centers
-as in earthworm, the ventral nerve cord is joined to the dorsal brain by connective tissues
>the overall pattern for the vertebrates nervous system differs from that of the invertebrates such as
earthworm and grasshoppers. The vertebrate verve cord is dorsal to the food tube, instead of ventral,
and hollow, instead of solid.
-------Phototropism is the bending of a plant toward the light
A tropism is a growth of a plant toward or away from a stimulus
>differs from taxis, which is the movement of an ENTIRE organism in response to a stimuli
>(+) stimulus is a growth of a plant toward a stimulus
>(-) is growth away from stimulus
Phototropism - light
Geotropism - gravity
Chemotropism - chemicals
Thigmotropism - touch
Hydrotropism - Water
>explained by auxins
>auxins are plant regulators --> influence cell division/elongation/and differentiation
>cell differentiation is the development of special tissues characteristics by cells that are unspecialized
when formed first
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>auxins causes growth of cells in the stem
>tips produce auxins
>this chemical diffuses down to a region of elongation. Here light causes an uneven distribution of auxins -> more on the unlighted side than on the lighted side
>people think light destroys auxins on the lighted side, or that light causes auxins to move to the other side
>increased growth of cells on the unlighted side causes bending toward the lighted side
>IAA (indole acetic acid) causes cell elongation in stems. It softens cell walls permitting the cell to absorb
more water and swell
>auxins can inhibit AND stimulate growth
Plant hormone responses depend on 1) hormones involved 2) their concentrations 3) the tissues affected.
A concentration that inhibits root growth may stimulate stem growth
Gibberella is a fungus that produces chemicals that causes extreme growth. The chemical it releases is
called Gibberellins.
>they stimulate the stems to grow longer
-some auxins are used as weed killers
Auxins are also used to:
-stimulate root formation for cuttings
-produce seedless fruit
-to prevent fruit from falling before maturity
Chemical control in animals differs from that in plants.
>animals have special cells for production of hormones
>in lower invertebrates hormones are formed from scattered cells
>in higher invertebrates they posses definite glands that product chemical hormones
-chemical secretions of endocrine glands are called hormones
>a hormone is a chemical that is secreted in one place and has its effects at a distance
-have widespread effects
-An organ that is influenced by a hormone is called a target organ for that hormones pass their secretions
into their blood capillaries rather than into ducts. Glands having ducts are called exocrine (externally
secreting) glands. Endocrine glands are called ductless glands
EXOCRINE (duct glands) GLANDS
>sections are liberated externally through a duct
>secretions are juices such as bile, sweat, saliva..
>effects of secretions are produced in the region where the duct empties
ENDOCRINE (ductless) GLANDS
>secretions are liberated into the capillaries of the bloodstream
>secretions are hormones such as thyroxin, adrenaline, and insulin
>effects of hormones many be produced throughout the body or in special target hormones
Chapter 15 (what we used to answer pg 272)
-The nervous system and the endocrine system together share the job of controlling the body’s activities
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-nervous system --> operates via nerve cells
-endocrine system -> operates via chemicals
>both secrete chemicals. Chemicals of the nervous system include neurotransmitters which carry impulses
across the synapses.
>the chemicals of the endocrine system are hormones secreted by ductless glands
(some neurons secrete noradrenaline, the adrenal medulla secrets noradrenaline also)
>both help maintain homeostasis
>differ in that nerve responses are more rapid than endocrine responses and last for shorter period of time
>nerves transmit impulses via neurons
>endocrine system hormones are carried by plasma of the blood
Nervous system of humans consists of basic components like: sensory neurons, interneuron, and motor
neurons
>nerves or bundles or neurons are sensory, motor or mixed
>nervous system divided into --> 1) CNS 2) PNS
>CNS is composed of the brain and spinal cord
>spinal cord is a hallow tube composed of nerve fibers that carry impulses to or from the brain
>also connect to the PNS and serves as center for many reflexes
The brain is an expanded hallow portion of the spinal cord
>composed of millions of neurons and their synapses
>also enables humans to have sensations, make judgments, and initiate action
>brain is protected by a bony cranium of the skull and by three membranes called meninges
>the three main portions of the brain are the cerebrum, the cerebellum, and the medulla
>the cerebrum is more highly developed in humans than in other animas
>the surface of it has ridges and folds called convolutions
>cortex is the outer portion of the cerebrum
-this region consists of cyton and numerous synapses which comprise the gray matter
>the inner portion of the cerebrum are axons with fatty sheaths that make up white matter
>superior thinking has seen associated with gray matter
>although eyes receives stimulus of light, the sensation of sight occurs in the cerebrum of the brain
>if optic nerve is stimulation the sensation of sight occurs in the cerebrum
>each of the sense organs and each part of the skin has a special part of the cerebral cortex where its
impulses are received and interpreted.
>regions of the cerebral cortex control specifically the voluntary muscles of the body
>higher functions of coordination --> reasoning, memory, emotion are controlled by the front part of the
cerebrum
Humans have short term and long term memory
>short term --> is maintained by impulses circulating within areas of the brain
>long term seems to involved the synthesis of protein molecules
>short term memory decreases with age
Habits are complicated acts that are examples of conditioned behavior.
>intrinsic reward --> one that follows naturally from performance of an act
>extrinsic reward --> an artificial reward
>memory and learning seems to: 1) change the function of existing neurons 2) formation of new synapses.
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>repetition establishes pathways for the transmission of nerve impulses which permit rapid automatic
responses to be made
>cerebellum coordinates and controls all voluntary activities (and some involuntary ones). It also sends info
from receptors in the inner ear and sends motor impulses to maintain balance
>medulla connects the spinal cord to other parts of the brain.
>it is the controls center for various involuntary functions
>like breathing, heartbeat, blood pressure, muscle contractions in the blood vessels, and the digestive tract,
and swallowing.
-Spinal cord is a tubular structure containing a hallow space, the spinal canal (in the center)
>in humans it is protected by 26 vertebrae, which make up the spinal column and by three membranes.
>the darker region is called gray matter
>this is the region where synapses occur between neurons.
>the white matter in the outer areas contains bundles of nerve tracts which carry impulses up and down the
spinal cord.
>the spinal cord is filled with cerebrospinal fluid which also occupies cavities of the brain.
>spinal cord is the center for reflex action
>a reflex is a simple innate form of behavior that is involuntary
>interneuron in the spinal cord also make connections leading to the brain
Characteristics of reflexes:
-reflexes are inborn
-reflexes are automatic
-reflexes protect the body
Functions of the brain and spinal cord
Cerebrum - creative through. Memory. Judgment. Sensation. Voluntary Action. Habits.
Cerebellum - coordination of voluntary activities. control of balance
Medulla - controls reflexes in upper regions of the body and such involuntary activities such as heart
action, breathing, coughing, swallowing, sneezing, movements of the digestive tract
Spinal cord -regulates reflexes, carries nerve impulses between various parts of the body and the brain
The peripheral nervous system has two parts
1) somatic nervous system
2) autonomic nervous system
>the PNS consists of nerves that carry impulses between the CNS and the various parts of the body
-all nerves outside the brain and spinal cord that extends throughout the body is PNS
-12 pairs of nerves connecting w/ the brain are cranial nerves
-31 pairs of nerves connecting with the spinal cord are spinal nerves
-olfactory nerves --> to the nose
-optic nerves -> eyes
-auditory nerves -> ears
-spinal nerves joins the spinal cords by two roots
>posterior root carries sensory impulses to the spinal cord
-anterior roots carries motor impulses from the spinal cord
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-within spinal nerve itself some neurons carry impulses in one direction and others in the opposite direction
so the spinal nerve is a MIXED nerve w/ sensory and motor components
The autonomic nervous system control involuntary activities
>functioning of internal organs
>this system maintained homeostasis by keeping the circulatory, respiratory, and digestive systems going at
the proper rates for working in unison.
>consists of two divisions
1) Sympathetic nervous systems and 2) parasympathetic nervous system
>have opposite effects
>Sympathetic --> produce responses for periods of stress (fight/flight response)
>Parasympathetic --> calms
ANS is linked by nerves to the spinal cord and brain. Thus the CNS are the ANS are interdependent.
>a large group of ganglia --> forms plexus --> serves as relay center containing interneuron
-Sympathetic releases noradrenaline
-Parasympathetic releases acetylcholine
>acetylcholine inhibits the action of heart muscle but stimulates intestinal muscle (makes digestion happen
faster9
>noradrenaline speeds heart rate but slows digestion
ANS contains only motor neurons while the somatic nervous system contain both sensory and motor
neurons
>somatic nervous system controls the activity of skeletal muscles which are under conscious control -->
react with outside world
>automatic nervous system --> homeostasis
Some malfunctions of the nervous system
1) cerebral palsy -> paralysis caused by damage to motor areas of the brain (you have involuntary
movements/difficulty coordinating voluntary muscle actions)
2) Meningitis: inflammation of the meninges (the membrane surrounding the brain and the spinal cord.
Caused by bacterium meningococcal (or by a virus)
3) Stroke: if a part of a brain’s blood supply is cut off the resulting damage to brain cells is a stroke. The
interruption of the blood supply can be caused by a hemorrhage or by a blood clot.
4) polio: “anterior poliomyelitis” virus infects the anterior (motor) roots of spinal nerves) Salk vaccine
(killed virus) and Sabin vaccine (weakened alive virus) exists
>human endocrine system consists of more than a dozen glands and groups of cells
>secretions of these glands are called hormones
>endocrine glands influence each other and thus form an interrelated system
>the endocrine helps to 1) coordinate life processes 2) maintain homeostasis despite change in the external
and internal environment
>the hypothalamus is a tiny structure of the brain located near its base. It is part of the CNS, but also has an
endocrine function.
>pituitary gland (major gland of endocrine) is connected to the hypothalamus by a stalk
>hypothalamus produced brain hormones that flow to the pituitary glands by means of a network of
capillaries and other hormones that pass by way of nerve fibers and stored in the pituitary gland until
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released.
-pituitary gland produces hormones that affect many other endocrine glands
>many endocrine glands stimulate and inhibit one another in coordinating the functions of the body
>two sections 1)anterior lobe 2) posterior lobe
>anterior pituitary --> releases growth hormone. Hypersecretion --> lead to giantism. Hyposecretion -->
leads to dwarfism
>releases Thyroid stimulating hormone (TSH): stimulates the thyroid gland to produce its own hormone,
thyroxin
>follicle-stimulating hormone (FSH) stimulates the ovaries to develop
>ACTH stimulates the adrenal cortex to produce the hormone cortisone
>posterior pituitary releases 2 hormones
1)oxytocin -> contractions in uterus
2) antiduretic hormones (ADH) --> affects water balance. Both are produced in brain’s hypothalamus but
are stores/released from here
-The thyroid gland produces thyroxin. It increases the general rate of the body’s metabolism, and is
essential to normal growth.
>hypothyroidism --> undersectrion of thyroxin --> rate of metabolism is lowered --> not active
several forms 1) cretinism: since birth --> may be physically or mentally retarded
2) myxedema: in adults, slowing of mental processes/metabolic rate 3) endemic goiter: enlargement of
thyroid gland. Caused by lack of iodide
>hyperthyroidism: metabolism increased. Is energetic/restless
>can cause exophtalmic goiter where the thyroid gland swells
>basal metabolism test measures rate which person takes in oxygen and gives off CO2 at rest
>parathyroid are a group of tiny glands located on the lobes of thyroids. The hormone they secrete,
parathormone regulates calcium in the blood and the rate at which calcium is deposited in the bones.
>shortage --> blood to bones --> causes violent involuntary muscular contractions called tetany
>Pancreases contains cells that secrete hormones into the bloodstreams
>so it is a duct gland and a ductless gland
>when German physician Paul Langerhans looks at the pancreases hw saw groups of cells that were
different from others. They stood out in the mass of other tissue. It was called the Islets of Langerhands.
>two kinds of these islet cells secrete insulin and glucagon
-Insulin is secreted in response to rise in blood glucose --> 1) promotes conversions of glucose to glycogen
to be stored in liver/muscle 2) helps cells to take glucose from blood and oxidize it
>excess of blood glucose called --> hyperglycemia --> lack called hypoglycemia
>diabetes mellitus is a hyperglycemia resulting from insulin deficiency
>in diabetes the loss of glucose excreted from urine is accompanies by water loss
>dehydration can cause failure of blood circulation due to drop in blood pressure
>glucagon is produced by different islet cells than those of insulin. It increases blood sugar levels by
promoting the breakdown of liver’s glycogen to glucose.
>two adrenal glands (one on top of each kidney) has two parts each
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1) medulla or inner part 2) cortex or outer part
Adrenal medulla: inner part of the adrenal gland produces the hormones adrenaline (or epinephrine) and
noradrenaline (or norepinphrine).
>shows relationship between nervous and endocrine system. Release of adrenaline from the adrenal
medulla is stimulated by a nerve fiber of the sympathetic system
>adrenanal medulla “gland of combat”
-increases rate/strength of heartbeat
-it stimulates respiration
-dilates respiratory air passages
-affects muscles of arteriole walls in a way that diverts blood from the digestive system to skeletal muscles
and to the brain.
-promotes activity of the enzymes that break down glycogen to glucose
>adrenal cortex secretes several steroid hormones.
>steroid hormone is a complex molecule but it is smaller than hormones which are protein
>an example is cortisol --> raises level of glucose in the blood by converting protein and fat of body tissues
into glucose
>also prevents inflammation
-another type of steroid produced promotes reabsorption into the kidneys tubules. Promotes reaborptions
into the bloodstream of Na+ and Cl- (helps maintain blood pressure)
>stimulated by ACTH [produced by the anterior pituitary gland]
>too much shuts off ACTG by negative feedback on the hypothalamus and the anterior pituitary
-gonads are sex glands. Produces hormones important in sexual cycle
>responsible for development of secondary sexual characteristics (breast, deepening of voice ect)
>estrogen and progesterone = female --> breast
>androgens (male sex hormones) Testosterone main one
>puberty is the period when the body becomes sexually matured
Endocrine glands work together to control body functions.
>2 examples --> glucose metabolism and pituitary-thyroid relationship
-glucose metabolism: the concentration of glucose in the blood remains fairly constant although some body
processes remove while other add
>a state of homeostasis is maintained by the combined action of insulin, glucagon, and adrenaline
>pancreas --> insulin and glucagon
>adrenal medulla --> adrenaline
>Insulin removes glucose from blood and stores it in the liver as glycogen. It also removes glucose from
the blood for use by cells of the body. When glucose levels drop, adrenaline and glucagon take glycogen in
the liver and converts it to glucose
-pituitary-thyroid feedback: the level of thyroxin in the blood is kept constant by a feedback system that
involves the anterior pituitary and thyroid glands. It is an example of negative feedback
Anterior pituitary gland releases TSH --> causes thyroid to release thyroxin --> increases rate of cellular
metabolism --> high level of thyroxin inhibits the anterior pituitary from producing TSH
-On or within a cell membrane of a target cells are specific receptor molecules. The shape of the receptor
molecule fits the shape of the appropriate hormone molecule, and two molecules combines.
-Hormones are 2 types
>small steroid molecules --> pass through cell membrane and form a hormone-receptor combination with
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the cell
>large protein molecules --> do not penetrate cell, they attach to specific receptor molecules on the cell
membrane. This combination on the cell membrane promotes the formation of a 2nd messenger molecules
within the cell. --> affects gene action in the nucleus to cause the hormone’s effects. Prostaglandin is an
intermediary molecule within the cell membrane
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