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Endocrine System
Chapter 36
Nervous vs Endocrine
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Nervous
 immediate
 acts thru electrical impulses and neurotransmitters
 effect is localized and short duration
Endocrine
 acts thru chemicals – hormones
 effect is generalized and long term duration
Impacts, Issues Video
Hormones in the Balance
Endocrine System
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Main Sources
pituitary gland
adrenal glands
thyroid gland
parathyroid glands
pineal gland
thymus gland
hypothalamus
(part of the brain)
pituitary gland,
anterior lobe
pituitary gland,
posterior lobe
pineal gland
thyroid gland
parathyroid glands (four)
thymus gland
adrenal gland (one pair)
medulla
pancreatic islets
ovaries
(one pair of
female gonads)
testes
(one pair of
male gonads)
Endocrine System
Mechanism of a steroid hormone
Hormones
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Classified as
 protein or protein derivative
 bind to receptor on cell membrane
 steroid
 receptors are located within the cytoplasm of the cell
 react with receptor site on selected cells
secreted by endocrine glands, endocrine cells, and certain neurons
travel through the bloodstream to nonadjacent target cells
chemical signal
 communication between cells, body parts
Hormones
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prostaglandins
 local hormone
 not carried by blood
 affects neighboring cells
 promotes pain and inflammation
growth hormones
 local hormone
 promotes cell division
Hormones
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pheromones
 affect metabolism
 influence the behavior of another individual
 active between animals not humans
Feedback Mechanisms
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negative feedback
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helps to maintain homeostasis
positive feedback
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enhances an already existing response
Stimulus
Blood level of thyroid
hormone falls below
a set point.
Response
+
Hypothalamus
–
TRH
–
Anterior Pituitary
TSH
Thyroid Gland
Thyroid hormone
is secreted
Rise in the blood
level of thyroid
hormone inhibits
secretion of TRH
and TSH.
Hormone Action
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activation of receptor
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transduction of signal
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functional response
Action of Hormones
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wide range of effects
induce target cells
2 ways hormones can influence cell metabolism
 1.) peptide hormone
 peptides, proteins, glycoproteins, modified amino acids
 Glucagon, ADH, oxytocin, TRH, insulin, somatotropin,
prolactin, FSH, LH, TSH
Action of Hormones
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ex.) muscle cells
 epinephrine binds to a receptor in the plasma membrane
 leads to the breakdown of glycogen to glucose
 never enters the cell
 1st messenger hormone
 2nd messenger sets metabolic machinery into motion
* activates protein kinase as well as other
enzymes
* cascade effect which allows for many
molecules of glycogen to be broken down
which in turn enters the blood stream
Protein Hormone
Mechanism of a peptide hormone
Protein Hormone
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hormone binds to a receptor at
cell surface
binding triggers a change in
activity of enzymes inside the cell
glucagon
glucagon receptor
cyclic AMP + Pi
ATP
cAMP activates
protein kinase A
Protein kinase A converts phosphorylase
kinase to active form and inhibits an
enzyme required for glucagon synthesis.
Action of Hormones
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2.) steroid hormone
 act more slowly
 action lasts longer
 limited to adrenal cortex, ovaries and testis
 Estrogens, progestins, androgens, cortisol, aldosterone
 derived from cholesterol
 enters the cell because they are lipids
 binds with DNA
 activates transcription
 inhibits transcription
Steroid Hormones
Mechanism of a steroid hormone
The Hypothalamus
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region in the forebrain
regulates internal environment
contains hormone-secreting cells
 produces and releases
 ADH, Oxytocin
interacts with pituitary
 contains releasing hormones
hypothalamus
pituitary gland
Pituitary Gland
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pea-sized gland at base of hypothalamus
two lobes
 posterior lobe
 stores and secretes hormones synthesized in the hypothalamus
 antidiuretic hormone (ADH)
 released in response to blood being concentrated
 goes to kidney
* causes water to be reabsorbed
 negative feedback
Pituitary Gland
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Oxytocin
 uterine contractions
 milk letdown
 positive feedback
Pituitary Gland
Posterior pituitary function
Pituitary Gland
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anterior pituitary
 affecting other glands
 thyroid stimulating hormone (TSH)
 Triiodothyronine / tyroxine
* both regulate metabolism and growth
rate increases
Pituitary Gland
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adrenocorticotropic hormone (ACTH)
 adrenal cortex
 release of cortisol
 raises blood sugar levels
 counteracts inflammation
gonadotropic hormone
 follicle stimulating (FSH)
 luteinizing hormone (LH)
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stimulates ovaries and testis to produce gametes
Pituitary Gland
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not affecting other glands
 meloncyte stimulating hormone (MSH)
 skin color changes
 prolactin (PRL)
 milk production
 carbohydrate / fat metabolism
 growth hormone
 skeletal and muscular growth
 increases the rate of amino acids entering cells to
produce proteins
Pituitary Gland
Anterior pituitary function
Pituitary Gland
Hypothalamus and pituitary
Thyroid Gland
epiglottis
thyroid cartilage
(Adam’s apple)
pharynx
thyroid gland
trachea
(windpipe)
anterior
parathyroid
gland
posterior
Thyroid/Parathyroid
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located in the neck
largest gland
stimulates all cells to metabolize faster
 more glucose broken down, more energy used
contains
 triiodthyronine (T3) / thyroxine (T4)
 regulates metabolism and growth rate
Thyroid/Parathyroid
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lack of iodine can result in a simple goiter
 hypothyrodism
 minimal production
 cretinism
 failure of thyroid to develop properly
 results in stunted growth
 myxedema
 adults
 lethargy, weight gain, loss of hair, slower pulse rate,
lowered body temperature
Thyroid/Parathyroid
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hyperthyroidism
 overproduction
 exophthalmic goiter
 eyes protrude due to swelling of the muscles that
moves the eyes
Parathyroid Gland
Parathyroid hormone action
Calcium Regulation
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calcium levels high
 calcitonin
 regulates calcium levels in the blood
 secreted by thyroid gland in response to high levels
 causes calcium to be deposited in the bone tissue
 osteoblasts
 reduces the activity and number of osteoclasts
 cell that causes the erosion of bone
Calcium Regulation
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parathyroid glands
 calcium levels too low
 PTH
 released in response to low calcium levels
 promotes the activity of osteoclasts
 promotes the reabsorption of calcium by the kidneys
 activates vitamin D
 stimulates the absorption of Ca from the intestine
Calcium Regulation
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hyperparathyrodism
 Ca levels too high
 results in tetany
 body shakes from continuous muscle contractions
 brought about by increased excitability of nerves
hypoparathyrodism
 Ca levels too low
 bones become soft and fragile
Adrenal Glands
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sit atop the kidneys
consists of
 adrenal medulla
 inner portion
 produces epinephrine and norepinephrin
 brings about bodily changes
 emergency
 responsible for fight-flight response to stress and
excitement
 effects are short term
Adrenal Glands
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adrenal cortex
 outer portion
 secretes cortisol
 maintains glucose levels in the absence of food
 inhibits blood glucose uptake by muscle and other tissues
 causes breakdown of proteins to amino acids and
conversion to glucose
 causes degradation of adipose tissue to fatty acids for use as
energy source
Adrenal Glands
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feedback control of cortisol secretion
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hypothalamus senses rise in glucose and secretes less releasing
hormone (CRH)
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anterior pituitary responds by secreting less ACTH
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corticotropin-releasing hormone
adrenocorticotropic hormone
adrenal cortex slows its secretion of cortisol
Adrenal Cortex
Control of cortisol secretion
Adrenal Glands
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mineralocorticoids
 regulate salt and water balance
 leads to an increase in blood volume and blood
pressure
Control of Glucose Metabolism
Hormones and glucose metabolism
Pancreatic Hormones
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lies between the kidney and near the duodenum
secretes
 insulin
 high blood glucose (sugar)
 stimulates uptake of glucose by
 liver cells
 adipose cells
 muscle cells
 stored as glycogen
 lowers blood sugar
Pancreatic Hormones
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glucagon
 low blood glucose
 major target are the liver and adipose tissue
 stimulates liver to break down glycogen
 uses fat and protein in preference to glucose as energy
 adipose tissue cells break down fat to glycerol and fatty
acids
 liver then takes these up and uses them as substrates
for glucose formation
Diabetes Mellitus
Excess glucose accumulates
Type 2
Type 1
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autoimmune disease
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usually appears in childhood
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insulin injections
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target cells don’t respond
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usually appears in adults
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diet, drugs