Chapter 9

Report
The Endocrine System
Chapter 17 – Lecture Notes
to accompany
Anatomy and Physiology: From Science to Life
textbook by
Gail Jenkins, Christopher Kemnitz, Gerard Tortora
1
Chapter Overview
17.1 Endocrine System Overview
17.2 Hormone Secretion/Pos. & Neg. Feedback
17.3 Hypothalamus and Anterior Pituitary
17.4 Posterior Pituitary
17.5 Thyroid Gland
17.6 Parathyroid Glands
17.7 Adrenal Cortex
17.8 Pancreas
17.9 Gonads
17.10 Pineal Gland
2
Essential Terms
hormone
 chemical mediator that helps maintain
homeostasis
target cell
 cell with a receptor that responds to the
presence of a hormone
3
Concept 17.1
Endocrine System Overview
4
General Characteristics




Glands that secrete chemical
signals (hormones) into
circulatory system
Hormone characteristics
 Produced in small quantities
 Secreted into intercellular
space
 Transported some distance in
circulatory system
 Acts on target tissues
elsewhere in body
Regulate activities of body
structures
Ligands: more general term for
chemical signals
5
Endocrine System Functions








Metabolism and tissue maturation
Ion regulation
Water balance
Immune system regulation
Heart rate and blood pressure regulation
Control of blood glucose and other nutrients
Control of reproductive functions
Uterine contractions and milk release
6
Endocrine Glands
exocrine glands secrete products onto a
surface
endocrine glands secrete products into the
body fluids
hormones are carried to target tissues
where activity is carried out
pituitary, thyroid, parathyroid, adrenal,
pineal
Other hormone secreting structures






hypothalamus, thymus, pancreas, ovaries,
testes, kidneys, stomach, liver, small intestine,
skin, heart, adipose tissue, placenta
7
Figure 17.1
8
Regulation of Activities:
Comparison of Endocrine
and Nervous Systems



Endocrine: amplitude modulated
signals.

Amount of hormone determines
strength of signal

Onset within minutes of secretion
of hormone
Nervous: frequency-modulated
signals.

Frequency of action potentials
produced by neurons determines
strength of signal.

Onset within milliseconds
Two systems actually inseparable

Nervous system secretes
neurohormones into circulatory
system

Nervous system uses
neurotransmitters and
neuromodulators as ligands

Some parts of endocrine system
innervated directly by nervous
system
9
Intercellular Chemical Signals






Hormones: type of intercellular signal. Produced by cells of
endocrine glands, enter circulatory system, and affect distant
cells; e.g., estrogen
Autocrine: released by cells and have a local effect on same cell
type from which chemical signals released; e.g., prostaglandin
Paracrine: released by cells and affect other cell types locally
without being transported in blood; e.g., somatostatin
Pheromones: secreted into environment and modify behavior
and physiology; e.g., sex pheromones
Neurohormone: produced by neurons and function like
hormones; e.g., oxytocin
Neurotransmitter or neuromodulator: produced by neurons
and secreted into extracellular spaces by presynaptic nerve
terminals; travels short distances; influences postsynaptic cells;
e.g., acetylcholine.
10
Functional Classification of
Intercellular Chemical Signals
11
Functional Classification of
Intercellular Chemical Signals
12
Control of Secretion Rate


Most hormones controlled by negative feedback
systems
Most hormones are not secreted at constant rate,
but their secretion is regulated by three different
methods
1.
2.
3.
The action of a substance other than a hormone on an
endocrine gland.
Neural control of endocrine gland.
Control of secretory activity of one endocrine gland by
hormone or neurohormone secreted by another endocrine
gland
13
Positive and Negative Feedback
•
•
•
•
POSITIVE
During the menstrual cycle, before
ovulation, small amounts of
estrogen are secreted from the
ovary.
Estrogen stimulates the release of
gonadotropin-releasing hormone
(GnRH) from the hypothalamus
and luteinizing hormone (LH)
from the anterior pituitary
GnRH also stimulates the release
of LH from the anterior pituitary
LH causes the release of additional
estrogen from the ovary. The
GnRH and LH levels in the blood
increase because of this positivefeedback effect.
14
Positive and Negative Feedback
•
•
•
NEGATIVE
During the menstrual cycle,
after ovulation, the ovary
begins to secrete
progesterone in response to
LH.
Progesterone inhibits the
release of GnRH from the
hypothalamus and LH from
the anterior pituitary.
Decreased GnRH release
from the hypothalamus
reduces LH secretion from
the anterior pituitary. GnRH
and LH levels in the blood
decrease because of this
negative-feedback effect.
15
Table 17.1
16
Concept 17.2
Hormone Secretion
17
Receptors




hormones only affect target cells
water soluble hormone receptors on
outside surface and trigger response
inside the cell
lipid soluble hormone receptors on
inside of cell and trigger response
inside cell
target cells generally have between
2,000 and 100,000 receptors for a
given hormone
18
Chemical Classes of Hormones
water soluble

amino acid based

lipid soluble

steroids
thyroid hormones
nitric oxide
transported in blood by transport proteins






slow rate of loss in kidneys
ready reserve of hormone in blood stream
19
Table 17.2 pt 1
20
Table 17.2 pt 2
21
Hormone Action




variable depending on hormone and
target cell
various targets respond differently to
same hormone
some hormones activate synthetic or
stimulatory processes
others activate degradation or
inhibitory processes
22
Figure 17.2
23
Figure 17.3
24
Hormone Interactions
permissive effects


one hormone allows the other to function
synergistic effects


one hormone intensifies the effects of the
other
antagonistic effects


one hormone inhibits or reduces the
effects of the other
25
Control of Hormone Secretion
hormones secreted in bursts
as stimulation increases bursts
increase in frequency
in absence of stimulation, bursts are
minimal or inhibited
regulated by







neural signals
chemical changes in blood
other hormones
26
Concept 17.3
Hypothalamus &
Pituitary Gland
27
Hypothalamus



controls the activity of the pituitary
gland
major integrating link between the
nervous and endocrine systems
hormones that stimulate anterior
pituitary are all either releasing
hormones or inhibiting hormones
28
Releasing and Inhibiting Hormones



Tropins or tropic hormones: hormones that regulate the hormone
secretions of target endocrine tissues. All anterior pituitary hormones are
tropins.
Releasing hormones:
 GHRH. Growth hormone-releasing hormone. Causes the anterior
pituitary to release growth hormone.
 TRH. Thyroid-releasing hormone. Causes the anterior pituitary to
release thyroid-stimulating hormone (TSH).
 CRH. Corticotropin-releasing hormone. Causes anterior pituitary to
produce adrenocorticotropic hormone.
 GnRH. Gonadotropin-releasing hormone. Causes anterior pituitary to
produce FSH (follicle stimulating hormone) and LH (luteinizing
hormone).
 PRH. Prolactin-releasing hormone. Causes the anterior pituitary to
release prolactin.
Inhibiting hormones:
 GHIH. Growth hormone-inhibiting hormone, somatostatin. Causes
the anterior pituitary to decrease release of growth hormone.
 PIH. Prolactin-inhibiting hormone. Causes the anterior pituitary to
decrease release of prolactin.
29
Figure 17.4
30
Pituitary Gland
two lobes
anterior lobe




stimulated by tropic hormones from
hypothalamus
hypophyseal portal system
posterior lobe



neural tissue that releases hormones
produced in the hypothalamus
neurosecretory cells
31
Table 17.3
32
Figure 17.5
33
Figure 17.6
34
Figure 17.11
35
FSH & LH
released by the anterior pituitary
triggered by GnRH
target tissue gonads
FSH






in females initiates development of ovarian
follicles
in males stimulates sperm production
LH



in females triggers ovulation
in males triggers testosterone secretion
36
PRL
released by the anterior pituitary




trigger is PRH and PIH from
hypothalamus
initiates and maintains milk secretion
and production by mammary glands in
females
in males can cause erectile
dysfunction
37
ACTH
secreted by anterior pituitary
triggered by CRH
also triggered by stress
controls production and secretion of
hormones called glucocorticoids






cortisol from adrenal cortex
cause negative feedback regulation of
CRH and ACTH release
38
Figure 17.16
39
MSH





secreted by anterior pituitary
function unknown in humans
presence of MSH receptors in brain
suggests it may influence brain activity
excessive CRH stimulates MSH
release
PIH inhibits MSH release
40
Table 17.4 pt 1
41
Table 17.4 pt 2
42
Concept 17.4
Posterior Pituitary
43
Posterior Pituitary




AKA neurohypophysis
store and release two hormones
produced by hypothalamus
ADH
OT
44
Figure 17.4
45
OT
oxytocin
targets uterus and mammary glands during
and after delivery
uterus contracts
milk ejection (“let down”)
function in non-reproducing women and in
men is unknown







animal studies seem to indicate parental
caretaking behavior toward offspring
sexual pleasure during and after intercourse
46
ADH
antidiuretic hormone
decreases urine production
kidneys return water to blood
decreases sweating
causes constriction of arterioles







increases blood pressure
AKA vasopressin
47
Figure 17.8
48
Table 17.5
49
Concept 17.5
Thyroid Gland
50
TSH
follicular cells produce

thyroxine (T4)
triiodothyronine (T3)


parafollicular cells produce

calcitonin



involved in calcium homeostasis
brings calcium levels down when too high
51
Figure 17.11
52
Actions of Thyroid Hormones


thyroxine and triiodothyronine
regulate oxygen use and BMR
53
Abnormal Thyroid Conditions
54
Concept 17.6
Parathyroid
55
PTH



parathyroid hormone
major regulator of calcium,
magnesium, and phosphate ions in
blood
PTH brings blood levels of calcium up
when too low
56
Figure 17.13
57
Table 17.7
58
Causes and Symptoms of
Hypersecretion and Hyposecretion
of Parathyroid Hormone
59
Concept 17.7
Adrenal Gland
60
Adrenal Cortex
divided into three zones
each secretes its own hormone





mineralocorticoids
glucocorticoids
androgens
61
Figure 17.15
62
Figure 17.16
63
Figure 17.5
64
Glucocorticoid Functions






Protein breakdown
Glucose formation
Triglyceride breakdown
Resistance to stress
Anti-inflammatory effects
Depression of immune responses
65
Adrenal Medulla



modified sympathetic ganglion of ANS
epinephrine
norepinephrine
66
Figure 17.8
67
Figure 17.17a
68
Figure 17.17b
69
Figure 17.17c
70
Figure 17.17d
71
Symptoms of Hypersecretion and
Hyposecretion of Adrenal Cortex Hormones
72
Concept 17.8
Pancreas
73
Blood Glucose Level Regulation
glucagon released when


blood glucose is low
insulin released when


blood glucose is high
74
Figure 17.18
75
Table 17.9
76
Concept 17.9
Gonads
77
FSH & LH




estrogens
progesterone
testosterone
androgens
78
Table 17.10
79
Concept 17.10
Pineal Gland
80
Pineal Gland




hormone secreted is melatonin
contributes to setting the body’s
biological clock
promotes sleepiness in small doses
in animals with breeding seasons,
melatonin inhibits reproductive
functions outside the season
81
End Chapter 17
82

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