Download Chapter 11 - Tribiana.com

Chapter 11
Endocrine Glands:
Secretion and
Action of Hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-1
Endocrine Glands
 Are
ductless and secrete
hormones into bloodstream
 Hormones go to target cells
that contain receptor
proteins for it
 Neurohormones are
secreted into blood by
specialized neurons
 Hormones affect
metabolism of targets
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-5
Chemical Classification of Hormones
 Amine
hormones are derived from tyrosine or tryptophan
Include
NE, Epi, thyroxine, melatonin
 Polypeptide/protein hormones
are chains of amino acids
 Include ADH, GH, insulin, oxytocin, glucagon, ACTH, PTH
 Glycoproteins include LH, FSH, TSH
 Steroids are lipids derived from cholesterol
 Include testosterone, estrogen, progesterone and cortisol
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-7
Hormone Interactions
A tissue
usually responds to # of hormones
2 hormones are synergistic if work together to produce an
effect
Produce a larger effect together than individual effects
added together
A hormone has permissive effect if it enhances
responsiveness of a target organ to 2nd hormone
If action of 1 hormone inhibits effect of another, it is
antagonistic
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-13
Hormone Levels and Tissue Responses
Half-life
is time required for blood level to be reduced by
half
Ranges from mins to hrs for most (days for thyroid
hormones)
Normal tissue responses are produced only when hormones
are in physiological range
High (pharmacological) doses can cause # of side effects
Probably by binding to receptors of other hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-14
Anterior Pituitary
 Secretes
6 trophic
hormones that
maintain size of
targets
 High blood levels
cause target to
hypertrophy
 Low levels
cause atrophy
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-39
Anterior Pituitary continued
 Growth
hormone (GH) promotes growth, protein synthesis, and
movement of amino acids into cells
 Thyroid stimulating hormone (TSH) stimulates thyroid to produce and
secrete T4 and T3
Adrenocorticotrophic hormone
(ACTH) stimulates adrenal
cortex to secrete cortisol, aldosterone
Follicle stimulating hormone (FSH) stimulates growth of
ovarian follicles and sperm production
Luteinizing hormone (LH) causes ovulation and secretion of
testosterone in testes
Prolactin (PRL) stimulates milk production by mammary
glands
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-40
Anterior Pituitary continued
 Releasing and
inhibiting
hormones from
hypothalamus are released
from axon endings into
capillary bed in median
eminence
 Carried by hypothalamohypophyseal portal
system directly to
another capillary bed in
A. Pit.
 Diffuse into A. Pit.
and regulate secretion
of its hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-42
Feedback Control of Anterior Pituitary
 Involves
short feedback loop
in which retrograde flow of
blood and hormones from A.
Pit. to hypothalamus inhibits
secretion of releasing
hormone
 Involves negative feedback
of target gland hormones
 And during menstrual cycle,
estrogen stimulates “LH
surge” by positive feedback
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-43
Higher Brain Function and Anterior Pituitary
Secretion
Hypothalamus
receives input from higher brain centers that
can affect A. Pit. secretion
E.g. emotional states and psychological stress can affect
circadian rhythms, menstrual cycle, and adrenal
hormones
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-44
Posterior Pituitary
Stores
and releases 2 hormones produced in hypothalamus:
Antidiuretic hormone (ADH/vasopressin) which
promotes H2O conservation by kidneys
Oxytocin which stimulates contractions of uterus during
parturition
And contractions of mammary gland alveoli for milkejection reflex
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-45
Adrenal Glands
Medulla
synthesizes and secretes 80% Epi and 20% NE
Controlled by sympathetic
Cortex is controlled by ACTH and secretes:
Cortisol which inhibits glucose utilization and
stimulates gluconeogenesis
Aldosterone which stimulate kidneys to reabsorb Na+
and secrete K+
And some supplementary sex steroids
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-49
Adrenal Cortex
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-50
Adrenal Medulla
Hormonal
effects of Epi last 10X longer than NE
Innervated by preganglionic Symp fibers
Activated during "fight or flight" response
Causes:
Increased respiratory rate
Increased HR and cardiac output
General vasoconstriction which increases venous
return
Glycogenolysis and lipolysis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-51
Stress and the Adrenal Gland
 Stress
induces a nonspecific response called
general adaptation
syndrome (GAS)
 Causes ACTH and
cortisol release
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-52
Stress and the Adrenal Gland
Chronic
stress can induce high levels of cortisol that cause a
number of negative effects:
atrophy of hippocampus (involved in memory)
reduced sensitivity of tissues to insulin (insulin
resistance)
inhibition of vagus nerve activity
suppression of growth hormone, thyroid hormone, and
gonadotropins
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-53
Thyroid Gland
Is
located just below the
larynx
Secretes T4 and T3 which
set BMR and are needed
for growth, development
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-55
Diseases of the Thyroid - Goiter
 In
absence of sufficient dietary
iodide, T4 and T3 cannot be
made and levels are low
 Low T4 and T3 don’t
provide negative feedback
and TSH levels go up
 Because TSH is a
trophic hormone,
thyroid gland grows
 Resulting in a goiter
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-58
Diseases of the Thyroid - Hypothyroidism
People
with inadequate T4 and T3 levels are hypothyroid
Have low BMR, weight gain, lethargy, cold intolerance
And myxedema = puffy face, hands, feet
During fetal development hypothyroidism can cause
cretinism (severe mental retardation)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-59
Diseases of the Thyroid - Hyperthyroidism
Goiters
are also produced by Grave's disease
Autoimmune disease where antibodies act like TSH and
stimulate thyroid gland to grow and oversecrete =
hyperthyroidism
Characterized by exopthalmos, weight loss, heat
intolerance, irritability, high BMR
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-60
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-61
Parathyroid Glands
Are
4 glands embedded in
lateral lobes of thyroid
gland
Secrete Parathyroid
hormone (PTH)
Most important
hormone for control of
blood Ca2+ levels
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-62
Parathyroid Hormone
 Release
stimulated by
decreased blood Ca2+
 Acts on bones, kidney, and
intestines to increase blood
Ca2+ levels
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-63
Islets of Langerhans
11-64
Islets of Langerhans continued
Alphas
secrete glucagon in response to low blood glucose
Stimulates glycogenolysis and lipolysis
Increases blood glucose
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-66
Islets of Langerhans continued
 Betas
secrete insulin in
response to low blood
glucose
 Promotes entry of
glucose into cells
 And conversion of
glucose into glycogen
and fat
 Decreases blood glucose
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-67
Pineal Gland continued
SCN
is primary timing center for circadian rhythms
Reset by daily light/dark changes
Melatonin is involved in aligning physiology with
sleep/wake cycle and seasons
Secreted at night and is inhibited by light
Inhibits GnRH (antigonadotropic) in many animals
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-70
Thymus
 Is
located around
trachea below thyroid
 Produces T cells of
immune system and
hormones that stimulate
them
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-71
Sex and Reproductive Hormones
Gonads
(testes and ovaries) secrete steroid hormones
testosterone, estrogen, and progesterone
Placenta secretes estrogen, progesterone, hCG, and
somatomammotropin
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-72
Prostaglandins (PGs)
 Are
produced in almost every organ
 Belong to eicosanoid family -- all derived from arachidonic acid of
plasma membrane
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-75
Prostaglandins (PGs) continued
Have
wide variety of functions
Different PGs may exert antagonistic effects in tissues
Some promote smooth muscle contraction and some
relaxation
Some promote clotting; some inhibit
Promotes inflammatory process of immune system
Plays role in ovulation
Inhibits gastric secretion in digestive system
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-76
Prostaglandins (PGs) continued
 Cyclooxygenase
(COX) 1 and 2 are involved in PG synthesis (Fig
11.34)
 Are targets of a number of inhibitory non-steroidal antiinflammatory drugs (NSAIDs)
 Aspirin, indomethacin, ibuprofen inhibit both COX 1 and 2
thereby producing side effects
 Celebrex and Vioxx only inhibit COX 2 and thus have few side
effects
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
11-77