Chapter 17– The Endocrine
System
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Ch. 17 Endocrine-- Study Guide
1. Critically read
– pp. 638-658 before “Hormones and Their
Actions” section
– pp. 668-677 “Endocrine Disorder” section
2. Do Before You Go On and Think About It
questions in the textbook
3. Do Testing Your Recall— 1-4, 6, 8, 11, 13,
15-18
4. Do True or False– 1, 3-10
5. Do Testing Your Comprehension-- none
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17.1. Overview of the
Endocrine System
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Fig. 17.1-Endocrine
glands
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§ Overview of Cell Communications
• Necessary for integration of cell activities
• Mechanisms
– gap junctions
• pores in cell membrane allow signaling chemicals to move
from cell to cell; Example--
– Neurotransmitters (Fig. 17.2 (a))
• released from neurons to travel across gap to 2nd cell;
Examples--
– Paracrine (local hormones)
• secreted into tissue fluids to affect nearby cells
– Hormones (strict definition)
• chemical messengers that travel in the bloodstream . . .
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Figure 17.2a– A neuron has a long fiber
that delivers its neurotransmitter.
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§ Endocrine System Components
• Endocrine system
– endocrine organs (thyroid, pineal, etc)
– hormone producing cells in organs (brain, heart
and small intestine)
• Endocrine glands
– produce hormones
• Hormone
– chemical messenger secreted into
bloodstream, stimulates response in another
tissue or organ (Fig. 17.2b); How?
• Target cells
– have receptors for a specific hormone
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Figure 17.2b– Endocrine cells secrete
a hormone into the bloodstream.
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§ Comparison of Nervous & Endocrine
Systems I (major differences)
1. Communication
– nervous sys.- both electrical and chemical
– endocrine sys.2. Speed and persistence of response
– nervous sys.- reacts quickly (1 - 10 msec), stops
quickly
– endocrine sys.3. Adaptation to long-term stimuli
– nervous sys.- response declines (adapts quickly)
– endocrine sys.- response persists
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§ Comparison of Nervous & Endocrine
Systems II (Similarities)
1. Several chemicals function as both hormones and
neurotransmitters
– NE and ADH
2. Some hormones secreted by neuroendocrine cells
(neurons)
– oxytocin
3. Both systems with overlapping effects on same
target cells
– NE and glucagon cause glycogen hydrolysis in liver
4. Systems regulate each other
– neurons trigger hormone secretion
– hormones stimulate or inhibit neurons
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§ Endocrine vs. Exocrine Glands
• Exocrine glands
– ducts carry secretion to a surface or organ cavity
– extracellular effects (food digestion)
– Example--
• Endocrine glands
– no ducts;
– intracellular effects, alter target cell
metabolism
– Example
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17.2A. The Hypothalamus
and Pituitary Gland
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§ Hypothalamus
• Shaped like a flattened funnel, forms floor and
walls of third ventricle (Fig. 14.12b)
• Regulates primitive functions from water
balance, sex drive, . . .
• Regulate many functions carried out by
pituitary gland
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Pineal
gland
Pituitary gland
(b) Hypothalamus
Hypothalamic Nuclei
Anterior nucleus
Thirst; thermoregulation
Arcuate nucleus
Regulates appetite: secretes
leaves hormones that
releasing
regulate anterior pituitary
Dorsomedial nucleus
Rage and other emotions
Mammillary nuclei
Relay between limbic system
and thalamus; involved in longterm memory
Paraventricular
nucleus
Produces oxytocin (involved
in childbirth, lactation, orgasm);
controls posterior pituitary
Posterior nucleus
Functions with periaqueductal
gray matter of midbrain in
emotional, cardiovascular, and
pain control
Preoptic nucleus
Hormonal control of reproductive
functions
Suprachiasmatic
nucleus
Biological clock; regulates
circadian rhythms and female
reproductive cycle
Supraoptic nucleus
Produces antidiuretic hormone
(involved in water balance);
controls posterior pituitary
Ventromedial nucleus
Satiety center (suppresses
hunger)
§ Pituitary Gland (Hypophysis)
• Suspended from hypothalamus by stalk
(infundibulum)
• Location and size
– housed in sella turcica of sphenoid bone
– 1.3 cm diameter
• Adenohypophysis (________ pituitary)
– arises from hypophyseal pouch (outgrowth of
pharynx); Fig. 17.3
• Neurohypophysis (________ pituitary)
– arises from brain
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§ Hypothalamic-hypophyseal portal system--1
1. (Anatomy)--Hypothalamic hormones travel in
portal system from hypothalamus to anterior
pituitary (Fig. 17.4 and x)
– Primary capillaries--?
– Secondary capillaries--?
2. (Physiology) Hypothalamic hormones regulate
hormones secretion by anterior pituitary
• Example— Gonadotropin-releasing hormone
(GnRH) and FSH/LH
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


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Neurosecretory
neurons
Hypothalamus
Hypophysiotropic H.:
●●
1
Systemic
arterial
inflow
2
Anterior pituitary
Hypothalamic-hypophyseal
portal system
3
System 6
venous
outflow
4
Posterior pituitary
5
Anterior pituitary hormones:
•
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§ Hypothalamic-hypophyseal portal system--2
3. Advantages (of this portal system)—
• Almost all the blood supplied to the anterior
pituitary must first pass through the
__________________________
• Releasing/inhibiting hormones then can
directly deliver to the anterior pituitary in what
fashion ? ____________________________
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Check Point Questions-A. Besides hormones, give another way for
intercellular communication.
B. Give an example of a hormone. Why
does your example qualify as a
hormone? (hint: definition of hormone)
C. Give an example of a hypothalamic
hormone.
D. What is the target tissue of a
hypothalamic hormone secreted into the
hypothalamic-hypophyseal portal
system?
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§ Hormones secreted by anterior pituitary
1. FSH (follicle stimulating hormone)
2. LH (luteinizing hormone)
The above two are called gonadotropins
3. TSH (thyroid stimulating hormone)
4. ACTH (adrenocorticotropic hormone)
5. GH (growth hormone)
6. PRL (prolactin)
• Tropic hormones-- target other
endocrine glands to release their own
hormones; which ones above? (Fig. 17.6)
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3.
2.
1.
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§ The Posterior Pituitary
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§ Posterior Pituitary Hormones
• OT (oxytocin) and ADH
– produced in hypothalamus
– transported by hypothalamohypophyseal tract to posterior lobe
(stores/releases hormones)
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Hormone Actions: Posterior Lobe
• ADH (Antidiuretic Hormone)
– Target organ/tissue-- ?
•  water retention, reduce urine
– also functions as neurotransmitter
• Oxytocin
– labor contractions, lactation (milk ejection)
– possible role in
• sperm transport . . .
• emotional bonding
• Table 17.4 on p. 645 is important
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Regulation of Posterior Pituitary
• Posterior lobe control - neuroendocrine reflexes
– hormone release in response to nervous
system signals
• suckling infant stimulates nerve endings
 hypothalamus  posterior lobe 
oxytocin  milk ejection
– hormone release in response to higher
brain centers
• milk ejection reflex can be triggered by a
baby's cry
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17.2B. Control of Pituitary
Secretion
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§ Negative feedback
1. Principle– Def. The body senses a
change and activates mechanisms that
negate it;
•
(On pituitary hormones) target organ
hormone levels inhibits release of tropic
hormones
2. Example– TRH-TSH-thyroid hormones
(see next slide; Fig. 17.7)
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(▬)
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§ Positive feedback—1
1. Definition– change in a factor triggers
a physiological response that
AMPLIFIES an initial change
2. Example— in the birth of a baby; how?
Fig. 1.12
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§ Positive feedback—2
3. Details of birth of a baby
– 1. Uterine contractions push the fetus
against the cervix
– 2. The stretching of the cervix
(RECEPTOR/SENSOR is the nerve cells
here) triggers nerve impulses to the brain
– 3. Brings about oxytocin secretion
– 4. The hormone oxytocin causes even
STRONGER powerful contractions of the
uterus (EFFECTOR is muscles in wall of
uterus)
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17.3. Other Endocrine
Glands
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§ A--Pineal Gland
I. Where is it?
II. Peak secretion ages 1-5; by puberty 75%
lower
III. Produces serotonin by day, converts it to
__________ at night
IV. May regulate timing of puberty in humans
V. Melatonin  in SAD;  by phototherapy
– Symptoms of SAD: depression . . .
– More SAD patients in Alaska or Florida?
– Premenstrual syndrome (PMS) similar to SAD
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§ B--Thymus
I.
Location-mediastinum,
II. Involution after
puberty
III. Its hormones-thymopoietin and
thymosins;
IV. Functions– on Tlymphocytes
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§ C--Thyroid Gland-1
I.
Largest
endocrine
gland; high
rate of blood
flow
II. Location-Anterior and
lateral sides
of trachea
Fig. 17.9a
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Thyroid Gland-2
III. Histology—
A. Thyroid follicles (Fig. 17.9, Fig. x )
– Filled with colloid and lined with simple
cuboidal epithelial (follicular cells) that
secretes two thyroid hormones (TH),
•
Triiodothyronine
Thyroxine
– Control of TH secretion is in response to
another hormone from the pituitary called
____________
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Thyroid Gland--3
IV. Functions of thyroid hormone
A.  or ↓ (circle one) body’s metabolic
rate and O2 consumption
B. Calorigenic effect –
C.  or ↓ (circle one) heart rate and
contraction strength
D.  respiratory rate
E. stimulates appetite and breakdown
CHO, lipids for fuel
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Thyroid Gland--4
V. C (calcitonin or parafollicular) cells
A. Where are they located? Fig. x
B. Produce __________
C. Target organ--?
D. Function--  blood Ca2+, promotes
Ca2+ deposition and bone formation
especially in children
– Osteoblasts more active
– Osteoclasts are inhibited
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§ D--Parathyroid Glands--1
I. Location—
II. Secretion— parathyroid hormone (PTH)
III. Target organs--?
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§ Parathyroid Glands--2
IV. Functions of PTH-–  or ↓ (circle one) blood Ca2+ levels
– promotes synthesis of calcitriol which:
• +/-- absorption of Ca2+
• +/-- urinary excretion
• +/-- resorption of bone matrix
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§ E— The Pancreas-1
I. Location— in relation to the stomach (Fig.
17.12a-b, Fig. x)
II. Endocrine secretion— by pancreatic islets
–
–
–
–
Only constitute about ____ of the pancreas
Including insulin, glucagon, and somatostatin
Which one is hyperglycemic hormone and which
one is hypoglycermic hormone?
98% is exocrine digestive gland
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1
2
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§ E— The Pancreas-2
III. Endocrine secretion—
A. Insulin– secreted by beta cells; in response
to rises of glucose and amino acids
•
•
•
Effects of insulin–
promoting glycogen, fat, and protein synthesis
Enhances cell growth and differentiation
B. Glucagon— secreted by alpha cells; in
response to concentration falls of blood
glucose
•
•
•
Effects of glucagon—
In the liver– gluconeogenesis, glycogenolysis
In adipose tissue—fat catabolism, release fatty acids
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17.7. Endocrine Disorders
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§ Endocrine Disorders
• Hyposecretion – inadequate hormone release
– Causes--tumor or lesion destroys gland
• Ex--head trauma affects pituitary gland’s ability to
secrete ADH (hyposecretion)
– Results-- diabetes insipidus (tasteless in urine)
• Hypersecretion – excessive hormone release
– Causes--tumors or autoimmune disorder
• Ex—autoantibodies mimic effect of TSH on the
thyroid-- toxic goiter (graves disease)
– Results– High TH in the blood; elevated
metabolic/heart rate etc.
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§ Pituitary Disorders
• Hypersecretion of growth hormones
– Acromegaly– In adults; thickening of the bones
and soft tissues
– problems in childhood or adolescence
• __________ if oversecretion
• dwarfism if hyposecretion
Which disease did she have?
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§ Diabetes mellitus-1
I. Causes– hyposecretion or inaction of
insulin
II. Symptoms– including three polys:
– Polyurea
– Polydipsia
– Polyphagia
– Hyperglycemia
– Glycosuria
– Ketonuria
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§ Diabetes mellitus-2
III.Type I (10%)– Insulin-dependent
diabetes mellitus; juvenile diabetes
–
–
Cause– the destruction of beta cells
by autoantibodies
Treatment– meal planning, exercise, the
self-monitoring of blood glucose level, periodic
insulin injections (or delivery by a pump)
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§ Diabetes mellitus-2
IV.Type II (90%)– Non-insulin-dependent
diabetes mellitus; Adult-onset DM
–
–
–
Cause– Insulin resistance;
Three major risk factors- heredity, age,
and obesity
Treatment– weight-loss program of diet and
exercise, oral medications
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