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Part A. Human ANATOMY AND PhySiology II. Chief Complaint: 8 year old girl with excessive thirst, frequent urination, and weight loss

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Part a

Part A

Human ANATOMY AND PhySiology II


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.

CASE STUDY


Case study1

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)

CASE STUDY


The diabetes epidemic

The diabetes epidemic


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

Endocrine System: Overview

Slide 1


Endocrine system overview1

  • 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

Endocrine System: Overview

Slide 2


Endocrine system overview2

  • Exocrine glands

    • Nonhormonal substances (sweat, saliva)

    • Have ducts to carry secretion to membrane surface

  • Endocrine glands

    • Produce hormones

    • Lack ducts

Endocrine System: Overview

Slide 3


Endocrine system overview3

  • 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

Endocrine System: Overview

Slide 4


Human anatomy and physiology ii

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


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

Chemical Messengers

Slide 6


Chemistry of hormones

  • Two main classes

    • Amino acid-based hormones

      • Amino acid derivatives, peptides, and proteins

    • Steroids

      • Synthesized from cholesterol

      • Gonadal and adrenocortical hormones

Chemistry of Hormones

Slide 7


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

Mechanisms of Hormone Action

Slide 8


Mechanisms of hormone action1

  • 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

Mechanisms of Hormone Action

Slide 9


Mechanisms of hormone action2

  • Hormones act at receptors in one of two ways, depending on their chemical nature and receptor location

    • Water-soluble hormones (all amino acid–based hormones except thyroid hormone)

      • Act on plasma membrane receptors

      • Act via G protein second messengers

      • Cannot enter cell

Mechanisms of Hormone Action

Slide 10


Mechanisms of hormone action3

2.Lipid-soluble hormones (steroid and thyroid hormones)

  • Act on intracellular receptors that directly activate genes

  • Can enter cell

Mechanisms of Hormone Action

Slide 11


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

Plasma Membrane Receptors and Second-messenger Systems

Slide 12


Plasma membrane receptors and second messenger systems1

  • 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

Plasma Membrane Receptors and Second-messenger Systems

Slide 13


Figure 16 2 cyclic amp second messenger mechanism of water soluble hormones

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

1

Hormone (1st messenger) binds receptor.

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


Figure 16 2 cyclic amp second messenger mechanism of water soluble hormones1

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

1

Hormone (1st messenger) binds receptor.

Extracellular fluid

Receptor

Cytoplasm

Slide 15


Figure 16 2 cyclic amp second messenger mechanism of water soluble hormones2

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

1

Hormone (1st messenger) binds receptor.

Extracellular fluid

G protein (Gs)

Receptor

GTP

GDP

GTP

Cytoplasm

2

Receptor activates G protein (Gs).

Slide 16


Figure 16 2 cyclic amp second messenger mechanism of water soluble hormones3

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

1

Hormone (1st messenger) binds receptor.

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


Figure 16 2 cyclic amp second messenger mechanism of water soluble hormones4

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

1

Hormone (1st messenger) binds receptor.

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


Figure 16 2 cyclic amp second messenger mechanism of water soluble hormones5

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

1

Hormone (1st messenger) binds receptor.

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


Plasma membrane receptors and second messenger systems2

  • 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

Plasma Membrane Receptors and Second-messenger Systems


Plasma membrane receptors and second messenger systems3

  • Ca2+ alters enzyme activity and channels, or binds to regulatory protein calmodulin

  • Calcium-bound calmodulin activates enzymes that amplify cellular response

Plasma Membrane Receptors and Second-messenger Systems


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

Other Signaling Mechanisms


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

Intracellular Receptors and Direct Gene Activation


Figure 16 3 direct gene activation mechanism of lipid soluble hormones

Steroid

hormone

Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones.

Extracellular

fluid

Plasma

membrane

1

The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.

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

4

Binding initiates transcription of the gene to mRNA.

mRNA

The mRNA directs protein synthesis.

5

New protein


Figure 16 3 direct gene activation mechanism of lipid soluble hormones1

Steroid

hormone

Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones.

Extracellular

fluid

Plasma

membrane

1

The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.

Cytoplasm

Receptor

protein

Receptor-

hormone

complex

Nucleus


Figure 16 3 direct gene activation mechanism of lipid soluble hormones2

Steroid

hormone

Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones.

Extracellular

fluid

Plasma

membrane

1

The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.

Cytoplasm

Receptor

protein

Receptor-

hormone

complex

The receptor-

hormone complex enters the nucleus.

2

Nucleus


Figure 16 3 direct gene activation mechanism of lipid soluble hormones3

Steroid

hormone

Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones.

Extracellular

fluid

Plasma

membrane

1

The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.

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


Figure 16 3 direct gene activation mechanism of lipid soluble hormones4

Steroid

hormone

Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones.

Extracellular

fluid

Plasma

membrane

1

The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.

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

4

Binding initiates transcription of the gene to mRNA.

mRNA


Figure 16 3 direct gene activation mechanism of lipid soluble hormones5

Steroid

hormone

Figure 16.3 Direct gene activation mechanism of lipid-soluble hormones.

Extracellular

fluid

Plasma

membrane

1

The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor.

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

4

Binding initiates transcription of the gene to mRNA.

mRNA

The mRNA directs protein synthesis.

5

New protein


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

Target Cell Specificity


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

Target Cell Activation


Target cell activation1

  • Hormones influence number of their receptors

    • Up-regulation—target cells form more receptors in response to low hormone levels

    • Down-regulation—target cells lose receptors in response to high hormone levels

Target Cell Activation


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

Control of Hormone Release


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

Humoral Stimuli


Human anatomy and physiology ii

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+.


Human anatomy and physiology ii

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


Human anatomy and physiology ii

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+.


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

Hormonal Stimuli


Human anatomy and physiology ii

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

Gonad

(Testis)

Adrenal

cortex

Stimulus: Hormones from hypothalamus.

Response: Anterior pituitary gland secretes

hormones that stimulate other endocrine glands to secrete hormones.


Human anatomy and physiology ii

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

Gonad

(Testis)

Adrenal

cortex


Human anatomy and physiology ii

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

Gonad

(Testis)

Adrenal

cortex


Human anatomy and physiology ii

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

Gonad

(Testis)

Adrenal

cortex

Stimulus: Hormones from hypothalamus.

Response: Anterior pituitary gland secretes

hormones that stimulate other endocrine glands to secrete hormones.


Neural stimuli

  • Nerve fibers stimulate hormone release

    • Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines

Neural Stimuli


Human anatomy and physiology ii

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

sympathetic fibers to adrenal medulla.

Response: Adrenal medulla cells secrete

epinephrine and norepinephrine.


Human anatomy and physiology ii

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


Human anatomy and physiology ii

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

sympathetic fibers to adrenal medulla.

Response: Adrenal medulla cells secrete

epinephrine and norepinephrine.


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

Nervous System Modulation


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

Hormones in the Blood


Hormones in the blood1

  • Hormones removed from blood by

    • Degrading enzymes

    • Kidneys

    • Liver

      • Half-life—time required for hormone's blood level to decrease by half

        • Varies from fraction of minute to a week

Hormones in the Blood


Onset of hormone activity

Some responses ~ immediate

Some, especially steroid, hours to days

Some must be activated in target cells

Onset of Hormone Activity


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

Duration of Hormone Activity


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

Interaction of Hormones at Target Cells


The pituitary gland and hypothalamus

  • Pituitary gland (hypophysis) has two major lobes

    • Posterior pituitary (lobe)

      • Neural tissue

    • Anterior pituitary (lobe) (adenohypophysis)

      • Glandular tissue

The Pituitary Gland and Hypothalamus


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

Pituitary-hypothalamic Relationships


Human anatomy and physiology ii

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).

Paraventricular nucleus

Hypothalamus

1

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


Human anatomy and physiology ii

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).

Paraventricular nucleus

Hypothalamus

1

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


Human anatomy and physiology ii

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).

Paraventricular nucleus

Hypothalamus

1

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


Human anatomy and physiology ii

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).

Paraventricular nucleus

Hypothalamus

1

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


Human anatomy and physiology ii

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2).

Paraventricular nucleus

Hypothalamus

1

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


Pituitary hypothalamic relationships1

  • 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

Pituitary-hypothalamic Relationships


Human anatomy and physiology ii

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


Human anatomy and physiology ii

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


Human anatomy and physiology ii

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


Human anatomy and physiology ii

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


Posterior pituitary and hypothalamic hormones

  • Oxytocin and ADH

    • Each composed of nine amino acids

    • Almost identical – differ in two amino acids

Posterior Pituitary and Hypothalamic Hormones


Oxytocin

Strong stimulant of uterine contraction

Released during childbirth

Hormonal trigger for milk ejection

Acts as neurotransmitter in brain

Oxytocin


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

ADH (Vasopressin)


Human anatomy and physiology ii

  • 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

ADH


Anterior pituitary hormones

Growth hormone (GH)

Thyroid-stimulating hormone (TSH) or thyrotropin

Adrenocorticotropic hormone (ACTH)

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)

Prolactin (PRL)

Anterior Pituitary Hormones


Anterior pituitary hormones1

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)

Anterior Pituitary Hormones


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)

Growth Hormone (GH, or Somatotropin)


Growth hormone gh or somatotropin1

  • 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 targets—bone and skeletal muscle

Growth Hormone (GH, or Somatotropin)


Growth hormone gh

  • GH release chiefly regulated by hypothalamic hormones

    • Growth hormone–releasing hormone (GHRH)

      • Stimulates release

    • Growth hormone–inhibiting hormone (GHIH) (somatostatin)

      • Inhibits release

  • Ghrelin (hunger hormone) also stimulates release

Growth Hormone (GH)


Homeostatic imbalances of growth hormone

  • Hypersecretion

    • In children results in gigantism

    • In adults results in acromegaly

  • Hyposecretion

    • In children results in pituitary dwarfism

Homeostatic Imbalances of Growth Hormone


Human anatomy and physiology ii

Figure 16.6 Growth-promoting and metabolic actions of growth hormone (GH).

Hypothalamus

secretes growth

hormone–releasing

hormone (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

Carbohydrate

metabolism

Fat

metabolism

Skeletal

Extraskeletal

Increases, stimulates

Reduces, inhibits

Initial stimulus

Increased protein

synthesis, and

cell growth and

proliferation

Increased

fat breakdown

and release

Increased blood

glucose and other

anti-insulin effects

Increased cartilage

formation and

skeletal growth

Physiological response

Result


Human anatomy and physiology ii

Figure 16.7 Disorders of pituitary growth hormone.


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

Thyroid-stimulating Hormone (Thyrotropin)


Human anatomy and physiology ii

Figure 16.8 Regulation of thyroid hormone secretion.

Hypothalamus

TRH

Anterior pituitary

TSH

Thyroid gland

Thyroid

hormones

Stimulates

Target cells

Inhibits


Adrenocorticotropic hormone corticotropin

Secreted by corticotropic cells of anterior pituitary

Stimulates adrenal cortex to release corticosteroids

Adrenocorticotropic Hormone (Corticotropin)


Adrenocorticotropic hormone corticotropin1

  • 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

Adrenocorticotropic Hormone (Corticotropin)


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

Gonadotropins


Gonadotropins1

  • Regulation of gonadotropin release

    • Triggered by gonadotropin-releasing hormone (GnRH) during and after puberty

    • Suppressed by gonadal hormones (feedback)

Gonadotropins


Prolactin prl

Secreted by prolactin cells of anterior pituitary

Stimulates milk production

Role in males not well understood

Prolactin (PRL)


Prolactin prl1

  • 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

Prolactin (PRL)


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