Download The Endocrine System

The Endocrine System
Unit 7
General Functions of the
Endocrine System
• Coordinating and regulating body cells,
tissues, organs, and systems to maintain
homeostasis by secreting chemicals
(hormones)
• Effects are sustained and work for longer
periods of times than the nervous system
• Works primarily on negative feedback
mechanisms
Refresher: Negative Feedback
vs. Positive Feedback
• Negative Feedback Mechanisms (Inhibitory)
• The response counteracts the input
• The most common feedback mechanism
• Examples:
•
•
•
•
Blood pressure
Blood sugar regulation
Cardiac output
Temperature regulation
• Positive Feedback Mechanisms (Stimulatory)
• The response is intensified by the input
• Example:
• Breastfeeding
• Childbirth
• Blood clotting
What is a hormone?
• Chemical messengers released by one tissue
(gland) and transported by the bloodstream to
reach the target tissues
• The target tissue is where the effect of the
hormone actually occurs
Gland
Bloodstream
Target Tissue
• Over 50 different hormones
• Most only affect a few, specific types of cells
Hormone Function
• Regulates chemical and volume of the body’s
internal environment
• Regulates metabolism and energy balance
• Regulates contraction of cardiac and smooth
muscle
• Regulates certain activities of the immune
system
Hormone Function (cont.)
• Maintains homeostasis despite emergency
environmental interruptions
•
•
•
•
Infection
Dehydration
Emotional stress
Trauma
• Hemorrhage
• Temperature
extremes
• starvation
• Plays a role in normal growth and sequential
development
• Contributes to the process of reproduction
Endocrine Glands
• Glands that secrete their products (hormones)
into extracellular spaces around cells. The
hormones then enter into the bloodstream by
diffusing into the capillaries located next to
the glands.
Glands and Organs of the
Endocrine System
• Hypothalamus
• Pineal
• Pituitary
• Thalamus
• Thyroid
• Kidneys
• Parathyroid
• Liver
• Thymus
• Stomach
• Pancreas
• Adrenal
• Gonads
• Testes
• Ovaries
• Lungs
• Heart
• Small Intestines
• Skin
• Placenta
Endocrine Glands
Endocrine Glands
And The Hormones they
Secrete
Pituitary Gland (Hypophysis)
Hormones of the
Pituitary Gland
• Growth hormone
• Thyroid stimulating hormone
• Adrenocorticotropic hormone
Pituitary Gland
• Found in the brain (attached to the
hypothalamus by a small stalk called the
infundibulum
• Sits in the sella turcica of the sphenoid bone!
(yes, I’m really excited about that)
• Often called the “master gland”
• Produces or stores 9 hormones
• Structurally divided into two parts:
• Anterior pituitary gland (adenohypophysis)
• Posterior pituitary gland (neurohypophysis)
Growth Hormone (GH)
• Also called human growth hormone (hGH)
• The most abundant anterior pituitary hormone
• Stimulates growth of body cells
• Stimulates protein synthesis by helping in the use of
amino acids in making new proteins
• Inhibits protein breakdown
• Stimulates lipolysis (fat breakdown)
• Inhibits the use of glucose as a fuel for metabolism
• Affects nearly every tissue of the body
Thyroid Stimulating
Hormone (TSH)
• Also called Thyrotropin
• Influences the body’s metabolic rate
• Target tissue is the thyroid gland
• Stimulates the secretion of:
• T3—Triiodothyronine
• T4--Thyroxine
Adrenocorticotropic
Hormone (ACTH)
• Target tissues are the adrenal glands
• Stimulates the release of steroid hormones
• Glucocorticoids (cortisol)
Thyroid Gland
Thyroid Gland
• Located just below the thyroid cartilage (Adam’s
apple) of the larynx
• Has a bow-tie shape
• Reddish-brown in color
• Has two lobes connected to each other by the
isthmus
• The only gland that can store its secretory product
in large quantities
• Normally about 100 day supply
Hormones of the Thyroid
Gland
• Thyroxine (T4)
• Contains 4 iodine atoms
• Requires mineral iodine to be made
• Targets most body cells and acts to increase
metabolism by improving energy utilization, O2
consumption, growth and development
• Most is converted to T3 by the removal of an
iodine atom
Actions of the Thyroid
Hormones (T3 and T4)
• Regulates oxygen utilization and basal metabolic
rate
• Regulates cellular metabolism
• Increases protein synthesis
• Increases lipolysis
• Increases glucose use in ATP production
• Works in conjunction with hGH to regulate growth
and development catecholamines
• Enhances the actions of
• Epinephrine
• Norepinephrine
Parathyroid Gland
Parathyroid Gland
• Four tiny glands located on the posterior
surface of the thyroid gland
• Control the body’s calcium levels
• Produces parathyroid hormone
Parathyroid Hormone (PTH)
• Raises blood calcium levels by:
• Breaking down bone
• Increasing body’s ability to absorb calcium from
food
• Increasing the kidney’s ability to hold on to
calcium that would otherwise be lost in urine
• Negative feedback
Parathyroid Hormone (PTH)
Adrenal (Suprarenal
Glands)
Adrenal (Suprarenal
Glands)
• Glands located superior to each kidney
• Structurally divided into two regions:
• Adrenal cortex
• Outer region
• Adrenal medulla
• the inner portion of the gland
Adrenal Medulla
• The inner portion of the gland
• Reddish-brown in color due to the large number
of blood vessels
• Contains two sets of hormone producing cells
• Under the direct control of the autonomic nervous
system (ANS)
• Contains many sympathetic nerve cells
• Functions with the sympathetic division of the
nervous system
• Hormone production and release can occur almost
immediately
Hormones of the Adrenal
Medulla
• Epinephrine (adrenaline)
•
•
•
•
•
Fight or flight
Raises the heart rate
Constricts blood vessels
Dilates pupils
Suppresses the immune system
• Norepinephrine (noradrenaline)
•
•
•
•
Fight or flight
Raises the heart rate
Causes glucose to be released as energy
Causes blood to flow to the muscles
Epinephrine and
Norepinephrine
• Epinephrine accounts for 80% and norepinephrine accounts for 20% of
secretions from the adrenal medulla
• Target tissues include skeletal muscles, adipose tissue, and the liver
• Effects:
•
•
•
•
•
•
•
•
Breakdown of glycogen to form glucose to provide more ATP (energy)
Increased muscular power and endurance
Increased heart rate and force of contraction (contractility)
Increases blood flow to the vital organs such as the brain, lungs, and
heart
Increased mental alertness
Enlarged airways
Increased breathing rate
OVERALL: helps the body cope with emergency and stress situations
Adrenal Cortex
• Outer region of the adrenal glands
• Makes up the majority of the gland
• Appears yellow due to the presence of lipids
• Produces more than 2 dozen steroid hormones
known as corticosteroids
Hormones of the Adrenal
Cortex
• Glucocorticoids
•
•
•
•
Regulate metabolism
Influence resistance to stress
Regulated by the secretion of ACTH
Cortisol (hydrocortisone)
• Makes up 95% of glucocorticoids
• Primary role is that of gluconeogenesis
• Synthesis of glucose and destruction of glycogen in the liver which
provides body with adequate glucose to produce ATP
• Promotes normal metabolism
• Provides resistance to stress (back up for stress response by the
adrenal medulla)
• Acts as an anti-inflammatory compound
• Inhibits allergens
Pancreas
Pancreas
• Located just posterior and slightly inferior to
the stomach
• Pink organ with a nodular appearance
• Both an endocrine and exocrine gland
• Exocrine produce digestive enzymes
• Endocrine produce hormones
• Endocrine tissue of the pancreas is called the
Pancreatic Islets or Islets of Langerhans
Cell Types of the Islets of
Langerhans
• Alpha Cells
• Secrete Glucagon
• Raises blood sugar
• Beta Cells
• Secrete Insulin
• Lowers blood sugar
Glucagon
• Secreted by Alpha Cells
• Increases blood sugar when it falls below normal
ranges
• Main target tissue is the liver
• Accelerates the conversion of glycogen into
glucose (glycogenolysis)
• Promotes the formation of glucose from lactic
acid (lactate) and certain amino acids
(gluconeogenesis)
• Suppresses appetite
Insulin
•
Secreted by the Beta Cells
•
Decreases blood glucose levels if it gets too high
•
Accelerates the transfer of glucose from the blood into the body’s cell
•
Accelerates the conversion of glucose to glycogen (glycogenesis)
•
Accelerates the entry of amino acids into cells and the synthesis of proteins
•
Accelerates the conversion of glucose or other nutrients into fatty acids (lipogenesis)
•
Inhibits glycogenolysis
•
Inhibits gluconeogenesis
•
Primarily influenced by blood glucose levels
•
Also influenced by increased levels of certain amino acids and hormones
•
hCG and ACTH stimulate insulin release
Blood Glucose
Regulation
• Insulin
• Decreases blood
glucose
• Glucagon
• Increases blood
glucose
Pineal Gland
Pineal Gland
• Behind the 3rd ventricle in between the two
hemispheres of the cerebrum
• Named because of its shape
• “Pine cone”
• Function is linked to the light detection function
of the eye
• Light sensitive in sub-mammals (frogs, fish, birds)
• Sometimes called “the third eye”
• Some believe it’s the gate to higher consciousness
• What is actually does:
• Produces melatonin
Melatonin
• Helps maintain circadian rhythm (sleep cycles)
• Helps regulate reproductive hormones
• Derivative of the amino acid tryptophan
• Production of melatonin is influenced by the
detection of light and dark by the retina
• Inhibited when retina detects light
• Stimulated in the absence of light
Thymus
Thymus
• Located behind the sternum and between the
lungs
• Only active until puberty
• Important for T-cell production (immune
system)
• Lymphatic AND Endocrine function
• Produces thymosin
Thymosin
• Stimulates and controls the production and
maturation of T-cells
• White blood cells pass through the thymus
where thymosin triggers the transformation
into T-cells
Gonads
• Ovaries
• Produce estrogen
• Testes
• Produce testosterone
Metabolic Diseases
and Disorders of
the Endocrine
System
Diabetes Mellitus
• A group of disorders that leads to an elevation
of blood glucose (hyperglycemia)
• Symptoms include:
• polyuria
• polyphagia
- polydipsia
- glucosuria
• Two Types or Categories of Diabetes
• Type I Diabetes - Insulin Dependent Diabetes
Mellitus (IDDM)
• Type II Diabetes - Non Insulin Dependent
Diabetes Mellitus (NIDDM)
Type I Diabetes (IDDM)
• Pancreas does not produce insulin due to the
destruction of beta cells in the Islets of
Langerhans
• Requires regular injections of insulin to prevent
death
• Most commonly develops in individuals younger
than 20 years old (Juvenile Onset Diabetes
Mellitus)
• Appears to be an autoimmune disorder
Complications from
Diabetes
•
atherosclerosis
•
heart disease
•
peripheral vascular disease
•
severe kidney damage
•
Glaucoma and/or blindness
•
gangrene
•
ketoacidosis
•
weight loss
•
neuropathy
Treatments for Diabetes
• Regular insulin injections
• Artificial pancreas
• Transplantation of the pancreas
• transplantation of clusters of islet cells
• Injection of fetal islet cells
Type II Diabetes (NIDDM)
• Also called Maturity Onset Diabetes
• Much more common type of Diabetes (over 90%
of Diabetes cases)
• Most often occurs in individuals over 40, but
seeing more often now in children
• Most individuals are overweight or clinically obese
• Blood glucose levels can usually be controlled by
medications, diet, exercise, and weight loss and
control
High and Low Blood Sugars
Dwarfism
• Caused by a hyposecretion of hGH during the
growth years resulting in a small person who
has a body frame of normal proportions
• Slow bone growth
• Epiphyseal plates close before normal height is
reached
• Other organs of the body may also fail to grow
and develop
• Treatment requires administration of hGH
during childhood
Dwarfism
Giantism
• Due to a hypersecretion of hGH during
childhood resulting in a person who grows to a
very large size
• Abnormal increase in bone length and size of
other organs
• The person is very tall with normal body
proportions
Giantism
Acromegaly
• Caused by hypersecretion of hGH in adulthood
• May be caused by steroid and hGH use
• Bones of hands, feet, and skull thicken
• Eyelids, lips, and tongue enlarge
• Skin thickens and develops furrows
• Prominent forehead and large nose are typical
features
Acromegaly
Cretinism
• Caused by hyposecretion of thyroid hormones
during fetal development, infancy, and childhood
• Low metabolism
• Retarded growth
• Individuals usually are severely mentally
impairments
• Exhibit dwarfism because the skeleton fails to grow
• Delayed/slowed sexual development
• Yellowish skin color
• Treated with synthetic hormones which prevent
the onset of symptoms
Cretinism
Myxedema
• Caused by hypothyroidism during the adult years
• Causes facial tissue to swell and look puffy
• About 5 times more common in females
• Other symptoms:
•
•
•
•
•
•
•
•
Bradycardia
Lethargy
Dry skin and hair
Sensitivity to cold
Low body temperature
Muscle weakness
Easily gains weight
Hypersensitive to medications
Myxedema
Graves’ Disease
• Caused by hyperthyroidism
• An autoimmune disorder resulting in:
•
•
•
•
•
•
•
Increased metabolism
Increased sweating
Weight loss
Tremors of hands
Heat intolerance
Insomnia
Nervousness
• May have a slightly enlarged thyroid gland (goiter)
• Causes eyes to protrude (exophthalmos)
Graves’ Disease
Goiter
Exophthalmos
Cushing’s Syndrome
• Occurs when your body is exposed to high
levels of the hormone cortisol for a long time.
• Overuse of glucocorticoid medications
• Prednisone
• Dexamethasone
• Prednisolone
• Body’s own overproduction of cortisol
• Cushing’s disease
• Tumor of the adrenal gland
• Tumors that produce ACTH
Cushing’s Syndrome
• Signs and Symptoms
• Round, red, full face (moon face)
• Slow growth rate in children
• Weight gain with fat accumulation on the trunk
(central obesity)
• Fat accumulation in the shoulders (buffalo hump)
• Fat loss from the arms, legs, and buttocks
• Striae (stretch marks) on abdomen, thoughs,
breasts
• Thin skin with easy bruising
• Bone pain and tenderness
• Excessive hair growth in women
Cushing’s Syndrome
Hyperparathyroidism
• Too much PTH
• Most patients do not have symptoms when diagnosed
• Possible symptoms and dangers
•
•
•
•
Osteoporosis
Kidney stones
Peptic ulcers
Insomnia
Hyp0parathyroidism
• Too little PTH
• Rare
• Symptoms:
•
•
•
•
Tingling in hands, fingers, and around mouth
Muscle cramps
Tetany (severe muscle cramping of the entire body)
Convulsions