Download File - Physiology At Large

ENDOCRINE SYSTEM
Corrected by Dr. C.Gerin
From Marieb
08/29/16
Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings
The Endocrine System
Anatomy: “ana” = separate from; “tomy”= cut open => dissection
Physiology: “logy” = study; “physio” =related to natural functioning
=>study of living organism
Copyright © 2006
Pearson
Inc., publishing
as Benjamin Cummings
8/26/13
Dr.
C.Education,
Gerin,
Anat227
Introduction

The nervous system and the endocrine
system work together: neuro-endocrine
system

The nervous system: produces short-term,
very specific responses

The endocrine system: produces long-lasting,
more general responses
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Pearson
Inc., publishing
as Benjamin Cummings
8/26/13
Dr.
C.Education,
Gerin,
Anat227
3
Major Endocrine Organs
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Figure 16.1
Autocrines and Paracrines



Autocrines – chemicals that exert effects on the
same cells that secrete them
Paracrines – locally acting chemicals that affect
cells other than those that secrete them
These are not considered hormones since
hormones are long-distance chemical signals
Copyright © 2006
Pearson
Inc., publishing
as Benjamin Cummings
8/26/13
Dr.
C.Education,
Gerin,
Anat227
Introduction

The endocrine system releases chemicals
called hormones : protein or lipids (steroid)

Secreted by a gland or gland-like structure

Travel in bloodstream

target organ or tissue distant

Therefore, response = distant site in the
body
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Inc., Anat227
publishing as Benjamin Cummings
8/26/13
Dr.Pearson
C. Education,
Gerin,
6

The main endocrine organs are:$$$$$

Epiphysis = Pineal gland (pine cone; melatonine)

Hypothalamus

Pituitary gland = Hypophysis

Thyroid gland

Parathyroid glands

Thymus gland

Suprarenal glands

Pancreas

Reproductive glands
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An Overview of the Endocrine System

Other endocrine tissues are:

Heart

Kidney

Adipose cells

Digestive tract
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The Endocrine System$$$$$$
RH
Hypothalamus
Pineal Gland= epiphysis
Production of ADH,
oxytocin, and regulatory
hormones SRH IRH
Melatonin
Parathyroid Glands
(on posterior surface of
thyroid gland)
Hypophysis=Pituitary Gland
SH
Pars distalis (anterior lobe):
ACTH, TSH, GH, PRL,
FSH, LH, and MSH
Neurohypophysis
(posterior lobe):
Release of oxytocin
and ADH
Parathyroid hormone (PTH)
Heart
Natriuretic peptides:
Atrial natriuretic
peptide (ANP)
Brain natriuretic
peptide (BNP)
Thyroid Gland
H
Thyroxine (T 4)
Triiodothyronine (T 3)
Calcitonin (CT)
Kidney
Erythropoietin (EPO)
Calcitriol
(Chapters 19 and 26)
Thymus
(Undergoes atrophy
during adulthood)
Adipose Tissue
Thymosins
KEY TO PITUITARY HORMONES
ACTH
TSH
GH
PRL
FSH
LH
MSH
ADH
Leptin
Resistin
Suprarenal Glands
Each suprarenal gland is
Adrenocorticotropic hormone
subdivided into:
Thyroid-stimulating hormone
Medulla:
Growth hormone
Epinephrine (E)
Prolactin
Norepinephrine (NE)
Follicle-stimulating hormone
Cortex:
Luteinizing hormone
Cortisol, corticosterone,
Melanocyte-stimulating hor*mone
aldosterone, androgens
Antidiuretic hormon (= AVP=Vasopressine
Digestive Tract
Numerous hormones CCK,…
(detailed in Chapter 25)
Pancreatic Islets
Testis
Insulin, glucagon
Gonads
Testes (male):
Androgens (especially
testosterone), inhibin
Ovaries (female):
Estrogens, progestins,
inhibin
Ovary
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Figure Gross Anatomy and Histological Organization of the Pituitary Gland and Its Subdivisions$$$$$
Mamillary
body
Third
Median
ventricle eminence
HYPOTHALAMUS
Optic chiasm
Infundibulum
Diaphragma
sellae
Pars
tuberalis
Adenohypophysis
(anterior lobe)
Pars
distalis
Neurohypophysis
(posterior lobe)
Pars
intermedia
Sphenoid
(sella turcica)
Relationship of the pituitary
gland to the hypothalamus
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Figure 19.2 Hypothalamic Control over Endocrine Organs
HYPOTHALAMUS
Secretion of
regulatory hormones
to control activity of
pars distalis (anterior
lobe) of pituitary gland
Production
of ADH and
oxytocin
Control of (sympathetic)
output to suprarenal
medullae
Preganglionic
motor fibers
Suprarenal gland
Medulla
Neurohypophysis
(posterior lobe)
of pituitary gland
Pars distalis
(anterior lobe)
of pituitary gland
Hormones secreted
by pars distalis of
pituitary gland
control other
endocrine organs
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Release of
ADH and
oxytocin*
Secretion of
epinephrine and
norepinephrine
11
An Overview of the Endocrine System

The Hypothalamus (RH)


Secretes regulatory hormones (RH)

Stimulating releasing hormones (SRH)

inhibiting releasing hormones (IRH)
Acts as an endocrine organ


Releases antidiuretic hormone (ADH)= arginine
vasopressine (AVP) and oxytocin to the pituitary
gland
Contains autonomic nervous system
centers
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
Exerts control over t
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The Pituitary Gland = HYPOPHYSIS

The Adenohypophysis = SH

Consists of five different cell types

Thyrotropes: release thyroid-stimulating
hormone (TSH)

Corticotropes: release adrenocorticotropic
hormone (ACTH) and melanocytestimulating hormone (MSH)

Gonadotropes: release follicle-stimulating
hormone (FSH) and luteinizing hormone
(LH), prolactin* (PRL)
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Insulin-like growth factor 1 (IGF-1), also called somatomedin C
=> IGH => role in childhood growth and continues to have
anabolic effects in adults.
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The Pituitary Gland

The Hypophyseal Portal System

Within the infundibulum is a plexus of
capillaries

Capillaries are fenestrated

Regulatory hormones leave the
hypothalamus and pass through the portal
vessels to the adenohypophysis
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Figure The Pituitary Gland and the Hypophyseal Portal System$$$$$$
Supraoptic Paraventricular
nuclei
nuclei
Mamillary
body
HYPOTHALAMUS
Optic
chiasm
Superior hypophyseal artery
Capillary
Beds
ADENOHYPOPHYSIS
OF PITUITARY GLAND
Infundibulum
Portal veins = BRIDGE between
the neural release
from the hypothalamic n.
AND the anterior hypohysis
Inferior hypophyseal artery
NEUROHYPOPHYSIS
OF PITUITARY GLAND
Endocrine cells
Hypophyseal veins
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Figure 19.4 Pituitary Hormones and Their Targets$$$$
Hypothalamus
Direct Control
by Nervous
System
KEY TO PITUITARY HORMONES
Direct Release
of Hormones
Indirect Control Through Release
of Regulatory Hormones
Sensory Osmoreceptor
stimulation stimulation
Regulatory hormones are released into
the hypophyseal portal system for delivery
to the anterior lobe of the pituitary
Medulla
Adenohypophysis of
pituitary gland
ACTH
TSH
GH
PRL
FSH
LH
MSH
ADH
Adrenocorticotropic hormone
Thyroid-stimulating hormone
Growth hormone
Prolactin
Follicle-stimulating hormone
Luteinizing hormone
Melanocyte-stimulating hormone
Antidiuretic hormone
Posterior lobe
of pituitary gland
ADH
Suprarenal
gland
ACTH
Cortex
TSH
Epinephrine and
norepinephrine
Liver
Thyroid
gland
Kidneys
GH
Oxytocin
MSH
PRL
FSH
Males: Smooth
muscle in ductus
deferens and
prostate gland
LH
Somatomedins
Females: Uterine
smooth muscle and
mammary glands
Glucocorticoids
(cortisol,
corticosterone)
Bone, muscle,
other tissues
Mammary
glands
Ovaries
of female
Testes
of male
Melanocytes (uncertain
significance in healthy
adults)
Thyroid
hormones (T3, T4)
Inhibin
Testosterone
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Estrogen
Progesterone
Inhibin
17
CONCLUSION

NERVOUS SYSTEM:


LOCAL RELEASE and LOCAL ACTION
ENDOCRINE SYSTEM:

Gland SECRETION , BLOOD TRANSPORT,
DISTANT ACTION

Epiphyseal Gland= Pineal Gland

Hypothalamus =RH (RHLH=GnRH)

Anterior Hypophysis = SH (FSH)

Target Organ: Gonades
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Figure 17.8 Autonomic Distribution of the Parasympathetic Output
Pterygopalatine ganglion
N III
Lacrimal gland
Eye
Ciliary ganglion
PONS
N VII
Salivary glands
Submandibular
ganglion
N IX
Otic ganglion
N X (Vagus)
Heart
Lungs
Autonomic plexuses
(see Figure 17.9)
Liver and
gallbladder
Stomach
Spleen
Pancreas
Large intestine
Pelvic
nerves
Small intestine
Rectum
Spinal
cord
S2
Kidney
S3
S4
KEY
Preganglionic neurons
Ganglionic neurons
Uterus
Ovary
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Penis Scrotum
19
Urinary bladder
Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers
Eye
PONS
Salivary
glands
Sympathetic nerves
Superior
Cervical
sympathetic
ganglia
Middle
Heart
Inferior
Gray rami to
spinal nerves
T1
T1
T2
T2
T3
T3
T4
T4
T5
T5
T6
T6
T7
T7
T8
T8
T9
T9
T10
T10
T11
Postganglionic fibers
to spinal nerves
(innervating skin, blood
vessels, sweat glands,
arrector pili muscles,
adipose tissue)
Lung
Celiac ganglion
Superior
mesenteric
ganglion
Liver and
gallbladder
Stomach
T11
T12
L1
L1
L2
L2
Lesser
splanchnic
nerve
L4
L5
S1
S2
S3
S4
S5
Spleen
Pancreas
Large intestine
Lumbar
splanchnic nerves
L3
L3
L4
Sympathetic
chain ganglia
Greater
splanchnic
nerve
T12
L5
S1
S2
S3
S4
S5
Cardiac and
pulmonary
plexuses
Small intestine
Inferior
mesenteric
ganglion
Suprarenal
medulla
Sacral
splanchnic
nerves
Kidney
Spinal cord
KEY
Preganglionic neurons
Ganglionic neurons
Coccygeal
ganglia (Co1)
fused together
(ganglion impar)
Uterus
Ovary
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Penis Scrotum
20
Urinary bladder
Figure The Regulation of Thyroid Secretion
Hypothalamus
releases TRH
Homeostasis
Disturbed
Decreased T3 and
T4 concentrations
in blood or low
body temperature
TRH
Anterior
lobe
Pituitary
gland
HOMEOSTASIS
Anterior
lobe
Normal T3 and T4
concentrations,
normal body
temperature
Adenohypophysis
releases TSH
TSH
Homeostasis
Restored
Increased T3 and
T4 concentrations
in blood
Thyroid
gland
Thyroid follicles
release T3 and T4
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NOW

GROSS ANATOMY DISSECTION

MODEL OBSERVATION

DESCRIPTION

LAB EXERCISES
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Hormones


Hormones – chemical substances secreted by cells
into the extracellular fluids to the blood stream

Regulate the metabolic function of other cells

Have lag times ranging from seconds to hours

Tend to have prolonged effects

Are classified as amino acid-based hormones, or
steroids
Eicosanoids – biologically active lipids with local
hormone–like activity
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Hormone Action

Hormones alter target cell activity by one of two
mechanisms


Second messengers:

Regulatory G proteins

Amino acid–based hormones
Direct gene activation


Steroid hormones
The precise response depends on the type of the
target cell
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Mechanism of Hormone Action

Hormones produce one or more of the following
cellular changes in target cells

Alter plasma membrane permeability

Stimulate protein synthesis

Activate or deactivate enzyme systems

Induce secretory activity

Stimulate mitosis
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Amino Acid-Based Hormone Action:
cAMP Second Messenger

Hormone (first messenger) binds to its receptor,
which then binds to a G protein

The G protein is then activated as it binds GTP,
displacing GDP

Activated G protein activates the effector enzyme
adenylate cyclase

Adenylate cyclase generates cAMP (second
messenger) from ATP

cAMP activates protein kinases, which then cause
cellular effects
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Amino Acid-Based Hormone Action: cAMP
Second Messenger
Extracellular fluid
Hormone A
Adenylate cyclase
Hormone B
1
1
2
GTP
3
GTP
GTP
Receptor Gs
GTP
GTP
2
Gi
GDP
GDP
ATP
Catecholamines
ACTH
FSH
LH
Glucagon
PTH
TSH
Calcitonin
3
4
Receptor
GTP
cAMP
5
Inactive
protein
kinase A
Active
protein
kinase A
Triggers responses of target
cell (activates enzymes,
stimulates cellular
secretion, opens ion
channels, etc.)
Cytoplasm
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Figure 16.2
Amino Acid-Based Hormone Action:
PIP-Calcium
 Hormone binds to the receptor and activates
G protein

G protein binds and activates phospholipase

Phospholipase splits the phospholipid PIP2* into
diacylglycerol (DAG) and IP3 (both act as second
messengers)

DAG activates protein kinases; IP3 triggers release of
Ca2+ stores

Ca2+ (third messenger) alters cellular responses**
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Amino Acid-Based Hormone Action:
PIP Mechanism
Extracellular fluid
Hormone
DAG
1
4
2
GTP
3
GTP
5
Receptor Gq
GTP
Catecholamines
TRH
ADH
GnRH
Oxytocin
GDP
IP3
Phospholipase C
5
Endoplasmic
reticulum
Cytoplasm
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Active
protein
kinase C
PIP2
Inactive
protein
kinase C
Triggers responses
of target cell
6
Ca2+ Ca2+- calmodulin
Figure 16.3
Steroid Hormones

This interaction prompts DNA transcription to
produce mRNA

The mRNA is translated into proteins, which bring
about a cellular effect
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Steroid
hormone
Cytoplasm
Steroid Receptorhormone
chaperonin
complex
Receptor-hormone
complex
Molecular
chaperones
Binding
Hormone
response
elements
Chromatin
Transcription
mRNA
mRNA
Nucleus
Ribosome
Translation
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New protein
Figure 16.4
Target Cell Specificity

Hormones circulate to all tissues but only activate
cells referred to as target cells

Target cells must have specific receptors to which
the hormone binds

These receptors may be intracellular or located on
the plasma membrane
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Target Cell Specificity

Examples of hormone activity

ACTH receptors are only found on certain cells of
the adrenal cortex

Thyroxin receptors are found on nearly all cells of
the body
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Target Cell Activation



Target cell activation depends on three factors

Blood levels of the hormone

Relative number of receptors on the target cell

The affinity of those receptors for the hormone
Up-regulation – target cells form more receptors in
response to the hormone
Down-regulation – target cells lose receptors in
response to the hormone
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Hormone Concentrations in the Blood

Hormones circulate in the blood in two forms –
free or bound

Steroids and thyroid hormone are attached to
plasma proteins*

All others are unencumbered
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Hormone Concentrations in the Blood


Concentrations of circulating hormone reflect:

Rate of release

Speed of inactivation and removal from the body
Hormones are removed from the blood by$$$$$:

Degrading enzymes

The kidneys

Liver enzyme systems
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Interaction of Hormones at Target Cells

Three types of hormone interaction



Permissiveness – one hormone cannot exert its
effects without another hormone being present
Synergism – more than one hormone produces the
same effects on a target cell
Antagonism – one or more hormones opposes the
action of another hormone
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Control of Hormone Release


Blood levels of hormones:

Are controlled by negative feedback systems

Vary only within a narrow desirable range
Hormones are synthesized and released in response
to:

Humoral stimuli (blood)

Neural stimuli

Hormonal stimuli
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Humoral Stimuli


Humoral stimuli – secretion of hormones in direct
response to changing blood levels of ions and
nutrients
Example: concentration of calcium ions in the
blood

Declining blood Ca2+ concentration stimulates the
parathyroid glands to secrete PTH (parathyroid
hormone)

PTH causes Ca2+ concentrations to rise and the
stimulus is removed
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Humoral Stimuli
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Figure 16.5a
Neural Stimuli

Neural stimuli – nerve
fibers stimulate hormone
release

Preganglionic
sympathetic nervous
system (SNS) fibers
stimulate the adrenal
medulla to secrete
catecholamines* NA, A

http://upload.wikimedia.org/wikipedia/commons/8/89/Nor
adrenalin_-_Noradrenaline.svg

http://upload.wikimedia.org/wikipedia/commons/3/36/Adr
enalin_-_Adrenaline.svg
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Figure 16.5b
Hormonal Stimuli

Hormonal stimuli – release of hormones in
response to hormones produced by other endocrine
organs

The hypothalamic hormones stimulate the anterior
pituitary

In turn, pituitary hormones stimulate targets to
secrete still more hormones
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Hormonal Stimuli$$$$
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Figure 16.5c
Nervous System Modulation

The nervous system can override normal endocrine
controls

For example, control of blood glucose levels

Normally the endocrine system maintains blood
glucose

Under stress, the body needs more glucose

The hypothalamus and the sympathetic nervous
system are activated to supply ample glucose
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Major Endocrine Organs: Pituitary Gland
(Hypophysis)
 Pituitary gland – two-lobed organ that secretes
nine major hormones

Neurohypophysis – posterior lobe (neural tissue)
and the infundibulum


Receives, stores, and releases hormones from the
hypothalamus
Adenohypophysis – anterior lobe, made up of
glandular tissue

Synthesizes and secretes a number of hormones
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Major Endocrine Organs: Pituitary Gland
(Hypophysis)
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Figure 16.6
Pituitary-Hypothalamic Relationships:
Posterior Lobe
 The posterior lobe is a downgrowth of
hypothalamic neural tissue

Has a neural connection with the hypothalamus
(hypothalamic-hypophyseal tract)

Nuclei (of what?) of the hypothalamus synthesize
oxytocin and antidiuretic hormone (ADH)
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Pituitary-Hypothalamic Relationships:
Anterior Lobe
 The anterior lobe of the pituitary is an
outpocketing of the oral mucosa

There is no direct neural contact with the
hypothalamus
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Pituitary-Hypothalamic Relationships:
Anterior Lobe

There is a vascular connection, the hypophyseal
portal system, consisting of:

The primary capillary plexus

The hypophyseal portal veins

The secondary capillary plexus
PLAY
InterActive Physiology ®: The Hypothalamic Pituitary Axis
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Pituitary-Hypothalamic Relationships:
Anterior Lobe
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Figure 16.6
Adenophypophyseal Hormones


The six hormones of the adenohypophysis:

Abbreviated as GH, TSH, ACTH, FSH, LH, and
PRL

Regulate the activity of other endocrine glands
In addition, pro-opiomelanocortin (POMC):

Has been isolated from the pituitary

Is split into ACTH, opiates, and MSH
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Activity of the Adenophypophysis

The hypothalamus sends a chemical stimulus to the
anterior pituitary

Releasing hormones stimulate the synthesis and
release of hormones

Inhibiting hormones shut off the synthesis and
release of hormones
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Activity of the Adenophypophysis

The tropic hormones that are released are:

Thyroid-stimulating hormone (TSH)

Adrenocorticotropic hormone (ACTH)

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)
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Growth Hormone (GH)


Produced by somatotropic cells of the anterior lobe
that:

Stimulate most cells, but target bone and skeletal
muscle

Promote protein synthesis and encourage the use of
fats for fuel
Most effects are mediated indirectly by
somatomedins
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Growth Hormone (GH)

Antagonistic hypothalamic hormones regulate GH

Growth hormone–releasing hormone (GHRH)
stimulates GH release

Growth hormone–inhibiting hormone (GHIH)
inhibits GH release
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Metabolic Action of Growth Hormone

GH stimulates liver, skeletal muscle, bone, and
cartilage to produce insulin-like growth factors

Direct action promotes lipolysis and inhibits
glucose uptake
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Metabolic Action of Growth Hormone
(GH)$$$$
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Figure 16.7
Thyroid Stimulating Hormone (Thyrotropin)

Stimulates the normal development and secretory
activity of the thyroid

Triggered by hypothalamic peptide thyrotropinreleasing hormone (TRH)

Rising blood levels of thyroid hormones act on the
pituitary and hypothalamus to block the release of
TSH
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Adrenocorticotropic Hormone (Corticotropin)

Stimulates the adrenal cortex to release
corticosteroids

Triggered by hypothalamic corticotropin-releasing
hormone (CRH) in a daily rhythm

Internal and external factors such as fever,
hypoglycemia, and stressors can trigger the release
of CRH
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Gonadotropins

Gonadotropins – follicle-stimulating hormone
(FSH) and luteinizing hormone (LH)

Regulate the function of the ovaries and testes

FSH stimulates gamete (egg or sperm) production

Absent from the blood in prepubertal boys and
girls

Triggered by the hypothalamic gonadotropinreleasing hormone (GnRH) during and after
puberty
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Functions of Gonadotropins

In females

LH works with FSH to cause maturation of the
ovarian follicle

LH works alone to trigger ovulation (expulsion of
the egg from the follicle)

LH promotes synthesis and release of estrogens
and progesterone
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Functions of Gonadotropins

In males

LH stimulates interstitial cells of the testes to
produce testosterone

LH is also referred to as interstitial cell-stimulating
hormone (ICSH)
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Prolactin (PRL)

In females, stimulates milk production by the
breasts

Triggered by the hypothalamic prolactin-releasing
hormone (PRH)

Inhibited by prolactin-inhibiting hormone (PIH)

Blood levels rise toward the end of pregnancy

Suckling stimulates PRH release and encourages
continued milk production
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The Posterior Pituitary and Hypothalamic
Hormones
 Posterior pituitary – made of axons of
hypothalamic neurons, stores antidiuretic hormone
(ADH) and oxytocin

ADH and oxytocin are synthesized in the
hypothalamus

ADH influences water balance

Oxytocin stimulates smooth muscle contraction in
breasts and uterus

Both use PIP-calcium second-messenger
mechanism
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