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Human ANATOMY AND PhySiology II

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Title: Human ANATOMY AND PhySiology II


1
Human ANATOMY AND PhySiology II
  • Part A

2
CASE STUDY
  • Chief Complaint 8 year old girl with excessive
    thirst, frequent urination, and weight loss
  • History History Cindy Mallon, an 8-year-old
    girl in previously good health, has noticed that,
    in the past month, she is increasingly thirsty.
    She gets up several times a night to urinate, and
    finds herself gulping down glassfulls of water.
    At the dinner table, she seems to be eating twice
    as much as she used to, yet she has lost 5 pounds
    in the past month. In the past three days, she
    has become nauseated, vomiting on three
    occasions, prompting a visit to her pediatrician.

3
CASE STUDY
  • At the doctor's office, blood and urine samples
    are taken. The following lab results are noted
  • blood glucose level 545 mg/dl (normal 50-170
    mg/dl)
  • blood pH level 7.23 (normally 7.35-7.45)
  • urine tested positive for glucose and ketone
    bodies (normally urine is free of glucose and
    ketone bodies)

4
The diabetes epidemic
5
Endocrine System Overview
  • Acts with nervous system to coordinate and
    integrate activity of body cells
  • Influences metabolic activities via hormones
    transported in blood
  • Response slower but longer lasting than nervous
    system
  • Endocrinology
  • Study of hormones and endocrine organs

Slide 1
6
Endocrine System Overview
  • Controls and integrates
  • Reproduction
  • Growth and development
  • Maintenance of electrolyte, water, and nutrient
    balance of blood
  • Regulation of cellular metabolism and energy
    balance
  • Mobilization of body defenses

Slide 2
7
Endocrine System Overview
  • Exocrine glands
  • Nonhormonal substances (sweat, saliva)
  • Have ducts to carry secretion to membrane surface
  • Endocrine glands
  • Produce hormones
  • Lack ducts

Slide 3
8
Endocrine System Overview
  • Endocrine glands pituitary, thyroid,
    parathyroid, adrenal, and pineal glands
  • Hypothalamus is Neuroendocrine organ
  • Some have exocrine and endocrine functions
  • Pancreas, gonads, placenta
  • Other tissues and organs that produce hormones
  • Adipose cells, thymus, and cells in walls of
    small intestine, stomach, kidneys, and heart

Slide 4
9
Figure 16.1 Location of selected endocrine
organs of the body.
Pineal gland
Hypothalamus
Pituitary gland
Thyroid gland
Parathyroid glands (on dorsal aspect of thyroid
gland)
Thymus
Adrenal glands
Pancreas
Gonads
Ovary (female)
Testis (male)
Slide 5
10
Chemical Messengers
  • Hormones long-distance chemical signals travel
    in blood or lymph
  • Autocrines chemicals that exert effects on same
    cells that secrete them
  • Paracrines locally acting chemicals that affect
    cells other than those that secrete them
  • Autocrines and paracrines are local chemical
    messengers not considered part of endocrine
    system

Slide 6
11
Chemistry of Hormones
  • Two main classes
  • Amino acid-based hormones
  • Amino acid derivatives, peptides, and proteins
  • Steroids
  • Synthesized from cholesterol
  • Gonadal and adrenocortical hormones

Slide 7
12
Mechanisms of Hormone Action
  • Though hormones circulate systemically only cells
    with receptors for that hormone affected
  • Target cells
  • Tissues with receptors for specific hormone
  • Hormones alter target cell activity

Slide 8
13
Mechanisms of Hormone Action
  • Hormone action on target cells may be to
  • Alter plasma membrane permeability and/or
    membrane potential by opening or closing ion
    channels
  • Stimulate synthesis of enzymes or other proteins
  • Activate or deactivate enzymes
  • Induce secretory activity
  • Stimulate mitosis

Slide 9
14
Mechanisms of Hormone Action
  • Hormones act at receptors in one of two ways,
    depending on their chemical nature and receptor
    location
  • Water-soluble hormones (all amino acidbased
    hormones except thyroid hormone)
  • Act on plasma membrane receptors
  • Act via G protein second messengers
  • Cannot enter cell

Slide 10
15
Mechanisms of Hormone Action
  • 2. Lipid-soluble hormones (steroid and thyroid
    hormones)
  • Act on intracellular receptors that directly
    activate genes
  • Can enter cell

Slide 11
16
Plasma Membrane Receptors and Second-messenger
Systems
  • cAMP signaling mechanism
  • Hormone (first messenger) binds to receptor
  • Receptor activates G protein
  • G protein activates adenylate cyclase
  • Adenylate cyclase converts ATP to cAMP (second
    messenger)
  • cAMP activates protein kinases that phosphorylate
    proteins

Slide 12
17
Plasma Membrane Receptors and Second-messenger
Systems
  • cAMP signaling mechanism
  • Activated kinases phosphorylate various proteins,
    activating some and inactivating others
  • cAMP is rapidly degraded by enzyme
    phosphodiesterase
  • Intracellular enzymatic cascades have huge
    amplification effect

Slide 13
18
Figure 16.2 Cyclic AMP second-messenger
mechanism of water-soluble hormones.
Recall from Chapter 3 that G protein signaling
mechanisms are like a molecular relay race.
Hormone (1st messenger)
Receptor
G protein
Enzyme
2nd messenger
Hormone (1st messenger) binds receptor.
1
Extracellular fluid
Adenylate cyclase
G protein (Gs)
cAMP activates protein kinases.
5
cAMP
GTP
Receptor
GTP
ATP
Active protein kinase
Inactive protein kinase
GDP
GTP
Triggers responses of target cell
(activates enzymes, stimulates cellular
secretion, opens ion channel, etc.)
Cytoplasm
2
3
4
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Adenylate cyclase converts ATP to cAMP
(2nd messenger).
Slide 14
19
Figure 16.2 Cyclic AMP second-messenger
mechanism of water-soluble hormones.
Recall from Chapter 3 that G protein signaling
mechanisms are like a molecular relay race.
Hormone (1st messenger)
Receptor
G protein
Enzyme
2nd messenger
Hormone (1st messenger) binds receptor.
1
Extracellular fluid
Receptor
Cytoplasm
Slide 15
20
Figure 16.2 Cyclic AMP second-messenger
mechanism of water-soluble hormones.
Recall from Chapter 3 that G protein signaling
mechanisms are like a molecular relay race.
Hormone (1st messenger)
Receptor
G protein
Enzyme
2nd messenger
Hormone (1st messenger) binds receptor.
1
Extracellular fluid
G protein (Gs)
Receptor
GTP
GDP
GTP
Cytoplasm
2
Receptor activates G protein (Gs).
Slide 16
21
Figure 16.2 Cyclic AMP second-messenger
mechanism of water-soluble hormones.
Recall from Chapter 3 that G protein signaling
mechanisms are like a molecular relay race.
Hormone (1st messenger)
Receptor
G protein
Enzyme
2nd messenger
Hormone (1st messenger) binds receptor.
1
Extracellular fluid
Adenylate cyclase
G protein (Gs)
GTP
Receptor
GTP
GDP
GTP
Cytoplasm
2
3
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Slide 17
22
Figure 16.2 Cyclic AMP second-messenger
mechanism of water-soluble hormones.
Recall from Chapter 3 that G protein signaling
mechanisms are like a molecular relay race.
Hormone (1st messenger)
Receptor
G protein
Enzyme
2nd messenger
Hormone (1st messenger) binds receptor.
1
Extracellular fluid
Adenylate cyclase
G protein (Gs)
cAMP
GTP
Receptor
GTP
ATP
GDP
GTP
Cytoplasm
2
3
4
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Adenylate cyclase converts ATP to cAMP
(2nd messenger).
Slide 18
23
Figure 16.2 Cyclic AMP second-messenger
mechanism of water-soluble hormones.
Recall from Chapter 3 that G protein signaling
mechanisms are like a molecular relay race.
Hormone (1st messenger)
Receptor
G protein
Enzyme
2nd messenger
Hormone (1st messenger) binds receptor.
1
Extracellular fluid
Adenylate cyclase
G protein (Gs)
cAMP activates protein kinases.
5
cAMP
GTP
Receptor
GTP
ATP
Active protein kinase
Inactive protein kinase
GDP
GTP
Triggers responses of target cell
(activates enzymes, stimulates cellular
secretion, opens ion channel, etc.)
Cytoplasm
2
3
4
Receptor activates G protein (Gs).
G protein activates adenylate cyclase.
Adenylate cyclase converts ATP to cAMP
(2nd messenger).
Slide 19
24
Plasma Membrane Receptors and Second-messenger
Systems
  • PIP2-calcium signaling mechanism
  • Involves G protein and membrane-bound effector
    phospholipase C
  • Phospholipase C splits PIP2 into two second
    messengers diacylglycerol (DAG) and inositol
    trisphosphate (IP3)
  • DAG activates protein kinase IP3 causes Ca2
    release
  • Calcium ions act as second messenger

25
Plasma Membrane Receptors and Second-messenger
Systems
  • Ca2 alters enzyme activity and channels, or
    binds to regulatory protein calmodulin
  • Calcium-bound calmodulin activates enzymes that
    amplify cellular response

26
Other Signaling Mechanisms
  • Cyclic guanosine monophosphate (cGMP) is second
    messenger for some hormones
  • Some work without second messengers
  • E.g., insulin receptor is tyrosine kinase enzyme
    that autophosphorylates upon insulin binding ?
    docking for relay proteins that trigger cell
    responses

27
Intracellular Receptors and Direct Gene Activation
  • Steroid hormones and thyroid hormone
  • Diffuse into target cells and bind with
    intracellular receptors
  • Receptor-hormone complex enters nucleus binds to
    specific region of DNA
  • Prompts DNA transcription to produce mRNA
  • mRNA directs protein synthesis
  • Promote metabolic activities, or promote
    synthesis of structural proteins or proteins for
    export from cell

28
Figure 16.3 Direct gene activation mechanism of
lipid-soluble hormones.
Steroid hormone
Extracellular fluid
Plasma membrane
The steroid hormone diffuses through the
plasma membrane and binds an intracellular
receptor.
1
Cytoplasm
Receptor protein
Receptor- hormone complex
The receptor- hormone complex enters the
nucleus.
2
Receptor Binding region
Nucleus
3
The receptor- hormone complex binds a
specific DNA region.
DNA
Binding initiates transcription of the gene
to mRNA.
4
mRNA
The mRNA directs protein synthesis.
5
New protein
29
Figure 16.3 Direct gene activation mechanism of
lipid-soluble hormones.
Steroid hormone
Extracellular fluid
Plasma membrane
The steroid hormone diffuses through the
plasma membrane and binds an intracellular
receptor.
1
Cytoplasm
Receptor protein
Receptor- hormone complex
Nucleus
30
Figure 16.3 Direct gene activation mechanism of
lipid-soluble hormones.
Steroid hormone
Extracellular fluid
Plasma membrane
The steroid hormone diffuses through the
plasma membrane and binds an intracellular
receptor.
1
Cytoplasm
Receptor protein
Receptor- hormone complex
The receptor- hormone complex enters the
nucleus.
2
Nucleus
31
Figure 16.3 Direct gene activation mechanism of
lipid-soluble hormones.
Steroid hormone
Extracellular fluid
Plasma membrane
The steroid hormone diffuses through the
plasma membrane and binds an intracellular
receptor.
1
Cytoplasm
Receptor protein
Receptor- hormone complex
The receptor- hormone complex enters the
nucleus.
2
Receptor Binding region
Nucleus
3
The receptor- hormone complex binds a
specific DNA region.
DNA
32
Figure 16.3 Direct gene activation mechanism of
lipid-soluble hormones.
Steroid hormone
Extracellular fluid
Plasma membrane
The steroid hormone diffuses through the
plasma membrane and binds an intracellular
receptor.
1
Cytoplasm
Receptor protein
Receptor- hormone complex
The receptor- hormone complex enters the
nucleus.
2
Receptor Binding region
Nucleus
3
The receptor- hormone complex binds a
specific DNA region.
DNA
Binding initiates transcription of the gene
to mRNA.
4
mRNA
33
Figure 16.3 Direct gene activation mechanism of
lipid-soluble hormones.
Steroid hormone
Extracellular fluid
Plasma membrane
The steroid hormone diffuses through the
plasma membrane and binds an intracellular
receptor.
1
Cytoplasm
Receptor protein
Receptor- hormone complex
The receptor- hormone complex enters the
nucleus.
2
Receptor Binding region
Nucleus
3
The receptor- hormone complex binds a
specific DNA region.
DNA
Binding initiates transcription of the gene
to mRNA.
4
mRNA
The mRNA directs protein synthesis.
5
New protein
34
Target Cell Specificity
  • Target cells must have specific receptors to
    which hormone binds, for example
  • ACTH receptors found only on certain cells of
    adrenal cortex
  • Thyroxin receptors are found on nearly all cells
    of body

35
Target Cell Activation
  • Target cell activation depends on three factors
  • Blood levels of hormone
  • Relative number of receptors on or in target cell
  • Affinity of binding between receptor and hormone

36
Target Cell Activation
  • Hormones influence number of their receptors
  • Up-regulationtarget cells form more receptors in
    response to low hormone levels
  • Down-regulationtarget cells lose receptors in
    response to high hormone levels

37
Control of Hormone Release
  • Blood levels of hormones
  • Controlled by negative feedback systems
  • Vary only within narrow, desirable range
  • Endocrine gland stimulated to synthesize and
    release hormones in response to
  • Humoral stimuli
  • Neural stimuli
  • Hormonal stimuli

38
Humoral Stimuli
  • Changing blood levels of ions and nutrients
    directly stimulate secretion of hormones
  • Example Ca2 in blood
  • Declining blood Ca2 concentration stimulates
    parathyroid glands to secrete PTH (parathyroid
    hormone)
  • PTH causes Ca2 concentrations to rise and
    stimulus is removed

39
Figure 16.4a Three types of endocrine gland
stimuli.
Humoral Stimulus
Hormone release caused by altered levels of
certain critical ions or nutrients.
Capillary (low Ca2 in blood)
Thyroid gland (posterior view)
Parathyroid glands
Parathyroid glands
PTH
Stimulus Low concentration of Ca2 in capillary
blood.
Response Parathyroid glands secrete parathyroid
hormone (PTH), which increases blood Ca2.
40
Figure 16.4a Three types of endocrine gland
stimuli.
Humoral Stimulus
Hormone release caused by altered levels of
certain critical ions or nutrients.
Capillary (low Ca2 in blood)
Thyroid gland (posterior view)
Parathyroid glands
Parathyroid glands
41
Figure 16.4a Three types of endocrine gland
stimuli.
Humoral Stimulus
Hormone release caused by altered levels of
certain critical ions or nutrients.
Capillary (low Ca2 in blood)
Thyroid gland (posterior view)
Parathyroid glands
Parathyroid glands
PTH
Stimulus Low concentration of Ca2 in capillary
blood.
Response Parathyroid glands secrete parathyroid
hormone (PTH), which increases blood Ca2.
42
Hormonal Stimuli
  • Hormones stimulate other endocrine organs to
    release their hormones
  • Hypothalamic hormones stimulate release of most
    anterior pituitary hormones
  • Anterior pituitary hormones stimulate targets to
    secrete still more hormones
  • Hypothalamic-pituitary-target endocrine organ
    feedback loop hormones from final target organs
    inhibit release of anterior pituitary hormones

43
Figure 16.4c Three types of endocrine gland
stimuli.
Hormonal Stimulus
Hormone release caused by another hormone (a
tropic hormone).
Hypothalamus
Anterior pituitary gland
Thyroid gland
Adrenal cortex
Gonad (Testis)
Stimulus Hormones from hypothalamus.
Response Anterior pituitary gland
secretes hormones that stimulate other endocrine
glands to secrete hormones.
44
Figure 16.4c Three types of endocrine gland
stimuli.
Hormonal Stimulus
Hormone release caused by another hormone (a
tropic hormone).
Hypothalamus
Anterior pituitary gland
Thyroid gland
Adrenal cortex
Gonad (Testis)
45
Figure 16.4c Three types of endocrine gland
stimuli.
Hormonal Stimulus
Hormone release caused by another hormone (a
tropic hormone).
Hypothalamus
Anterior pituitary gland
Thyroid gland
Adrenal cortex
Gonad (Testis)
46
Figure 16.4c Three types of endocrine gland
stimuli.
Hormonal Stimulus
Hormone release caused by another hormone (a
tropic hormone).
Hypothalamus
Anterior pituitary gland
Thyroid gland
Adrenal cortex
Gonad (Testis)
Stimulus Hormones from hypothalamus.
Response Anterior pituitary gland
secretes hormones that stimulate other endocrine
glands to secrete hormones.
47
Neural Stimuli
  • Nerve fibers stimulate hormone release
  • Sympathetic nervous system fibers stimulate
    adrenal medulla to secrete catecholamines

48
Figure 16.4b Three types of endocrine gland
stimuli.
Neural Stimulus
Hormone release caused by neural input.
CNS (spinal cord)
Preganglionic sympathetic fibers
Medulla of adrenal gland
Capillary
Stimulus Action potentials in preganglionic sympa
thetic fibers to adrenal medulla.
Response Adrenal medulla cells
secrete epinephrine and norepinephrine.
49
Figure 16.4b Three types of endocrine gland
stimuli.
Neural Stimulus
Hormone release caused by neural input.
CNS (spinal cord)
Preganglionic sympathetic fibers
Medulla of adrenal gland
Capillary
50
Figure 16.4b Three types of endocrine gland
stimuli.
Neural Stimulus
Hormone release caused by neural input.
CNS (spinal cord)
Preganglionic sympathetic fibers
Medulla of adrenal gland
Capillary
Stimulus Action potentials in preganglionic sympa
thetic fibers to adrenal medulla.
Response Adrenal medulla cells
secrete epinephrine and norepinephrine.
51
Nervous System Modulation
  • Nervous system modifies stimulation of endocrine
    glands and their negative feedback mechanisms
  • Example under severe stress, hypothalamus and
    sympathetic nervous system activated
  • ? body glucose levels rise
  • Nervous system can override normal endocrine
    controls

52
Hormones in the Blood
  • Hormones circulate in blood either free or bound
  • Steroids and thyroid hormone are attached to
    plasma proteins
  • All others circulate without carriers
  • Concentration of circulating hormone reflects
  • Rate of release
  • Speed of inactivation and removal from body

53
Hormones in the Blood
  • Hormones removed from blood by
  • Degrading enzymes
  • Kidneys
  • Liver
  • Half-lifetime required for hormone's blood level
    to decrease by half
  • Varies from fraction of minute to a week

54
Onset of Hormone Activity
  • Some responses immediate
  • Some, especially steroid, hours to days
  • Some must be activated in target cells

55
Duration of Hormone Activity
  • Limited
  • Ranges from 10 seconds to several hours
  • Effects may disappear as blood levels drop
  • Some persist at low blood levels

56
Interaction of Hormones at Target Cells
  • Multiple hormones may act on same target at same
    time
  • Permissiveness one hormone cannot exert its
    effects without another hormone being present
  • Synergism more than one hormone produces same
    effects on target cell ? amplification
  • Antagonism one or more hormones oppose(s) action
    of another hormone

57
The Pituitary Gland and Hypothalamus
  • Pituitary gland (hypophysis) has two major lobes
  • Posterior pituitary (lobe)
  • Neural tissue
  • Anterior pituitary (lobe) (adenohypophysis)
  • Glandular tissue

58
Pituitary-hypothalamic Relationships
  • Posterior pituitary (lobe)
  • Downgrowth of hypothalamic neural tissue
  • Neural connection to hypothalamus
    (hypothalamic-hypophyseal tract)
  • Nuclei of hypothalamus synthesize neurohormones
    oxytocin and antidiuretic hormone (ADH)
  • Neurohormones are transported to and stored in
    posterior pituitary

59
Figure 16.5a The hypothalamus controls release
of hormones from the pituitary gland in two
different ways (1 of 2).
Paraventricular nucleus
1
Hypothalamus
Hypothalamic neurons synthesize oxytocin or
antidiuretic hormone (ADH).
Posterior lobe of pituitary
Optic chiasma
Supraoptic nucleus
Infundibulum (connecting stalk)
2
Oxytocin and ADH are transported down the
axons of the hypothalamic- hypophyseal tract to
the posterior pituitary.
Inferior hypophyseal artery
Hypothalamic- hypophyseal tract
Axon terminals
3
Oxytocin and ADH are stored in axon
terminals in the posterior pituitary.
Posterior lobe of pituitary
4
When hypothalamic neurons fire, action
potentials arriving at the axon terminals cause
oxytocin or ADH to be released into the blood.
Oxytocin ADH
60
Figure 16.5a The hypothalamus controls release
of hormones from the pituitary gland in two
different ways (1 of 2).
Paraventricular nucleus
1
Hypothalamus
Hypothalamic neurons synthesize oxytocin or
antidiuretic hormone (ADH).
Posterior lobe of pituitary
Optic chiasma
Supraoptic nucleus
Infundibulum (connecting stalk)
Inferior hypophyseal artery
Hypothalamic- hypophyseal tract
Axon terminals
Posterior lobe of pituitary
61
Figure 16.5a The hypothalamus controls release
of hormones from the pituitary gland in two
different ways (1 of 2).
Paraventricular nucleus
1
Hypothalamus
Hypothalamic neurons synthesize oxytocin or
antidiuretic hormone (ADH).
Posterior lobe of pituitary
Optic chiasma
Supraoptic nucleus
Infundibulum (connecting stalk)
2
Oxytocin and ADH are transported down the
axons of the hypothalamic- hypophyseal tract to
the posterior pituitary.
Inferior hypophyseal artery
Hypothalamic- hypophyseal tract
Axon terminals
Posterior lobe of pituitary
62
Figure 16.5a The hypothalamus controls release
of hormones from the pituitary gland in two
different ways (1 of 2).
Paraventricular nucleus
1
Hypothalamus
Hypothalamic neurons synthesize oxytocin or
antidiuretic hormone (ADH).
Posterior lobe of pituitary
Optic chiasma
Supraoptic nucleus
Infundibulum (connecting stalk)
2
Oxytocin and ADH are transported down the
axons of the hypothalamic- hypophyseal tract to
the posterior pituitary.
Inferior hypophyseal artery
Hypothalamic- hypophyseal tract
Axon terminals
3
Oxytocin and ADH are stored in axon
terminals in the posterior pituitary.
Posterior lobe of pituitary
63
Figure 16.5a The hypothalamus controls release
of hormones from the pituitary gland in two
different ways (1 of 2).
Paraventricular nucleus
1
Hypothalamus
Hypothalamic neurons synthesize oxytocin or
antidiuretic hormone (ADH).
Posterior lobe of pituitary
Optic chiasma
Supraoptic nucleus
Infundibulum (connecting stalk)
2
Oxytocin and ADH are transported down the
axons of the hypothalamic- hypophyseal tract to
the posterior pituitary.
Inferior hypophyseal artery
Hypothalamic- hypophyseal tract
Axon terminals
3
Oxytocin and ADH are stored in axon
terminals in the posterior pituitary.
Posterior lobe of pituitary
4
When hypothalamic neurons fire, action
potentials arriving at the axon terminals cause
oxytocin or ADH to be released into the blood.
Oxytocin ADH
64
Pituitary-hypothalamic Relationships
  • Anterior Lobe
  • Originates as out-pocketing of oral mucosa
  • Vascular connection to hypothalamus
  • Hypophyseal portal system
  • Primary capillary plexus
  • Hypophyseal portal veins
  • Secondary capillary plexus
  • Carries releasing and inhibiting hormones to
    anterior pituitary to regulate hormone secretion

65
Figure 16.5b The hypothalamus controls release of
hormones from the pituitary gland in two
different ways (2 of 2).
Hypothalamus
Hypothalamic neurons synthesize GHRH, GHIH,
TRH, CRH, GnRH, PIH.
Anterior lobe of pituitary
Superior hypophyseal artery
1
When appropriately stimulated, hypothalamic
neurons secrete releasing or inhibiting hormones
into the primary capillary plexus.
2
Hypothalamic hormones travel through portal
veins to the anterior pituitary where they
stimulate or inhibit release of hormones made in
the anterior pituitary.
Hypophyseal portal system
Primary capillary plexus
A portal system is two capillary plexuses (beds)
connected by veins.
3
In response to releasing hormones, the
anterior pituitary secretes hormones into the
secondary capillary plexus. This in turn empties
into the general circulation.
Hypophyseal portal veins
Secondary capillary plexus
GH, TSH, ACTH, FSH, LH, PRL
Anterior lobe of pituitary
66
Figure 16.5b The hypothalamus controls release of
hormones from the pituitary gland in two
different ways (2 of 2).
Hypothalamus
Hypothalamic neurons synthesize GHRH, GHIH,
TRH, CRH, GnRH, PIH.
Anterior lobe of pituitary
Superior hypophyseal artery
1
When appropriately stimulated, hypothalamic
neurons secrete releasing or inhibiting hormones
into the primary capillary plexus.
Hypophyseal portal system
Primary capillary plexus
A portal system is two capillary plexuses (beds)
connected by veins.
Hypophyseal portal veins
Secondary capillary plexus
GH, TSH, ACTH, FSH, LH, PRL
Anterior lobe of pituitary
67
Figure 16.5b The hypothalamus controls release of
hormones from the pituitary gland in two
different ways (2 of 2).
Hypothalamus
Hypothalamic neurons synthesize GHRH, GHIH,
TRH, CRH, GnRH, PIH.
Anterior lobe of pituitary
Superior hypophyseal artery
1
When appropriately stimulated, hypothalamic
neurons secrete releasing or inhibiting hormones
into the primary capillary plexus.
2
Hypothalamic hormones travel through portal
veins to the anterior pituitary where they
stimulate or inhibit release of hormones made in
the anterior pituitary.
Hypophyseal portal system
Primary capillary plexus
A portal system is two capillary plexuses (beds)
connected by veins.
Hypophyseal portal veins
Secondary capillary plexus
GH, TSH, ACTH, FSH, LH, PRL
Anterior lobe of pituitary
68
Figure 16.5b The hypothalamus controls release of
hormones from the pituitary gland in two
different ways (2 of 2).
Hypothalamus
Hypothalamic neurons synthesize GHRH, GHIH,
TRH, CRH, GnRH, PIH.
Anterior lobe of pituitary
Superior hypophyseal artery
1
When appropriately stimulated, hypothalamic
neurons secrete releasing or inhibiting hormones
into the primary capillary plexus.
2
Hypothalamic hormones travel through portal
veins to the anterior pituitary where they
stimulate or inhibit release of hormones made in
the anterior pituitary.
Hypophyseal portal system
Primary capillary plexus
A portal system is two capillary plexuses (beds)
connected by veins.
3
In response to releasing hormones, the
anterior pituitary secretes hormones into the
secondary capillary plexus. This in turn empties
into the general circulation.
Hypophyseal portal veins
Secondary capillary plexus
GH, TSH, ACTH, FSH, LH, PRL
Anterior lobe of pituitary
69
Posterior Pituitary and Hypothalamic Hormones
  • Oxytocin and ADH
  • Each composed of nine amino acids
  • Almost identical differ in two amino acids

70
Oxytocin
  • Strong stimulant of uterine contraction
  • Released during childbirth
  • Hormonal trigger for milk ejection
  • Acts as neurotransmitter in brain

71
ADH (Vasopressin)
  • Inhibits or prevents urine formation
  • Regulates water balance
  • Targets kidney tubules ? reabsorb more water
  • Release also triggered by pain, low blood
    pressure, and drugs
  • Inhibited by alcohol, diuretics
  • High concentrations ? vasoconstriction

72
ADH
  • Diabetes insipidus
  • ADH deficiency due to hypothalamus or posterior
    pituitary damage
  • Must keep well-hydrated
  • Syndrome of inappropriate ADH secretion (SIADH)
  • Retention of fluid, headache, disorientation
  • Fluid restriction blood sodium level monitoring

73
Anterior Pituitary Hormones
  • Growth hormone (GH)
  • Thyroid-stimulating hormone (TSH) or thyrotropin
  • Adrenocorticotropic hormone (ACTH)
  • Follicle-stimulating hormone (FSH)
  • Luteinizing hormone (LH)
  • Prolactin (PRL)

74
Anterior Pituitary Hormones
  • All are proteins
  • All except GH activate cyclic AMP
    second-messenger systems at their targets
  • TSH, ACTH, FSH, and LH are all tropic hormones
    (regulate secretory action of other endocrine
    glands)

75
Growth Hormone (GH, or Somatotropin)
  • Produced by somatotropic cells
  • Direct actions on metabolism
  • Increases blood levels of fatty acids encourages
    use of fatty acids for fuel protein synthesis
  • Decreases rate of glucose uptake and metabolism
    conserving glucose
  • ? Glycogen breakdown and glucose release to blood
    (anti-insulin effect)

76
Growth Hormone (GH, or Somatotropin)
  • Indirect actions on growth
  • Mediates growth via growth-promoting proteins
    insulin-like growth factors (IGFs)
  • IGFs stimulate
  • Uptake of nutrients ? DNA and proteins
  • Formation of collagen and deposition of bone
    matrix
  • Major targetsbone and skeletal muscle

77
Growth Hormone (GH)
  • GH release chiefly regulated by hypothalamic
    hormones
  • Growth hormonereleasing hormone (GHRH)
  • Stimulates release
  • Growth hormoneinhibiting hormone (GHIH)
    (somatostatin)
  • Inhibits release
  • Ghrelin (hunger hormone) also stimulates release

78
Homeostatic Imbalances of Growth Hormone
  • Hypersecretion
  • In children results in gigantism
  • In adults results in acromegaly
  • Hyposecretion
  • In children results in pituitary dwarfism

79
Figure 16.6 Growth-promoting and metabolic
actions of growth hormone (GH).
Hypothalamus secretes growth hormonereleasing hor
mone (GHRH), and GHIH (somatostatin)
Inhibits GHRH release
Feedback
Stimulates GHIH release
Anterior pituitary
Inhibits GH synthesis and release
Growth hormone (GH)
Direct actions (metabolic, anti-insulin)
Indirect actions (growth- promoting)
Liver and other tissues
Produce
Insulin-like growth factors (IGFs)
Effects
Effects
Fat metabolism
Carbohydrate metabolism
Skeletal
Extraskeletal
Increases, stimulates
Reduces, inhibits
Initial stimulus
Increased protein synthesis, and cell growth
and proliferation
Increased cartilage formation and skeletal growth
Increased fat breakdown and release
Increased blood glucose and other anti-insulin
effects
Physiological response
Result
80
Figure 16.7 Disorders of pituitary growth
hormone.
81
Thyroid-stimulating Hormone (Thyrotropin)
  • Produced by thyrotropic cells of anterior
    pituitary
  • Stimulates normal development and secretory
    activity of thyroid
  • Release triggered by thyrotropin-releasing
    hormone from hypothalamus
  • Inhibited by rising blood levels of thyroid
    hormones that act on pituitary and hypothalamus

82
Figure 16.8 Regulation of thyroid hormone
secretion.
Hypothalamus
TRH
Anterior pituitary
TSH
Thyroid gland
Thyroid hormones
Stimulates
Target cells
Inhibits
83
Adrenocorticotropic Hormone (Corticotropin)
  • Secreted by corticotropic cells of anterior
    pituitary
  • Stimulates adrenal cortex to release
    corticosteroids

84
Adrenocorticotropic Hormone (Corticotropin)
  • Regulation of ACTH release
  • Triggered by hypothalamic corticotropin-releasing
    hormone (CRH) in daily rhythm
  • Internal and external factors such as fever,
    hypoglycemia, and stressors can alter release of
    CRH

85
Gonadotropins
  • Follicle-stimulating hormone (FSH) and
    luteinizing hormone (LH)
  • Secreted by gonadotrophs of anterior pituitary
  • FSH stimulates gamete (egg or sperm) production
  • LH promotes production of gonadal hormones
  • Absent from the blood in prepubertal boys and
    girls

86
Gonadotropins
  • Regulation of gonadotropin release
  • Triggered by gonadotropin-releasing hormone
    (GnRH) during and after puberty
  • Suppressed by gonadal hormones (feedback)

87
Prolactin (PRL)
  • Secreted by prolactin cells of anterior pituitary
  • Stimulates milk production
  • Role in males not well understood

88
Prolactin (PRL)
  • Regulation of PRL release
  • Primarily controlled by prolactin-inhibiting
    hormone (PIH) (dopamine)
  • Blood levels rise toward end of pregnancy
  • Suckling stimulates PRL release and promotes
    continued milk production
  • Hypersecretion causes inappropriate lactation,
    lack of menses, infertility in females, and
    impotence in males
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