L2: Hypothalamus and Pituitary Gland Phys

Question 1

The interface between the nervous and endocrine systems?

Answer 1

Hypothalamus

Question 2

Main endocrine function of the hypopthalamus? (7)

Answer 2

• growth
• fertility and reproduction
• osmoregulation (water balance)
• metabolism (thermoregulation)
• energy balance
• stress response
• lactation

Question 3

Connections between the hypothalamus and Pituitary Gland?
Morphology and Function of each?

Answer 3

Magnocellular Neruons (large, long)
–large cell bodies with long axons projecting down to (posterior) pituitary
–oxytocin and vasopressin (ADH) released into systemic circulation

Parvocellular Neurons (small, short)
–small cell bodies w/ shorter axons projecting to top of pituitary stalk (infundibulum)
–6 hormones (hypophysiotropic hormones) released into Portal Circulation

Question 4

Hormones secreted by Parvocellular Neurons?

Answer 4

Question 5

Posterior Pituitary is made of __________ tissue

Answer 5

Pituitary gland is made of NEURAL tissue

Question 6

Collection of axonal projections from the hypothalamus that serve as a site for the secretion of neurohypophysial hormones directly into the blood?

Answer 6

Posterior Pituitary

Question 7

_____________: Unmyelinated nerve axons of neurons cells whose cell bodies are located in hypothalamus

Answer 7

Neurohypohysis (aka. Posterior Pituitary): Unmyelinated nerve axons of neurons cells whose cell bodies are located in hypothalamus

Question 8

Another name for glial cells?

Answer 8

Pituicytes

Question 9

______________: Secretory granules containing oxytocin and vasopressin in terminal region of axon of Posterior Pituitary

Answer 9

Herring bodies: Secretory granules containing oxytocin and vasopressin in terminal region of axon

Question 10

Vasopressin is released from the _____________

Answer 10

Vasopressin is released from the Posterior Pituitary

Question 11

Vasopressin’s physiological effects? (V1 vs. V2)

Answer 11

V1 receptors:
□ abundant in vascular smooth muscle cells
□ activation of V1 receptors => VSMC contraction (‘vasopressin’)

V2 receptors:
□ abundant in renal tubule epithelial cells
□ activation of V2 receptors => increased renal H2O reabsorption

Question 12

___________ plays essential role in maintaining water balance in kidney

Answer 12

Vasopressin

Question 13

How does Vasopressin (ADH/AVP) Function to regulate water balance?

Answer 13

Plasma osmolality of > 280mOsm/kg => AVP release

AVP acts on renal epithelial cells to promote reabsorption of H2O

Plasma volume is increased and its osmolality decreased
Urine volume is decreased and its osmolality is increased

Independently, thirst centers in the hypothalamus are activated increasing the urge to consume H2O

Question 14

What 3 stimuli control Vasopressin Release?

Answer 14

• Blood Osmolality > 280mOsM (sensed by hypothalamus osmoreceptors)
• Hypovolemia (decreased atrial stretch receptor activation)
• Hypotension ( decreased carotid and aortic baroreceptor activation

Question 15

ADH Action on Kidney Tubule Epithelia?

Answer 15

ADH acts on renal epithelial cells V2 receptors to promote reabsorption of H2O

Leads to water channels (Aquaporin II ) insertion on apical membrane => allows water to enter cell and be returned to vasculature=> Smaller volume of more concentrated urine secreted

Question 16

Inability of kidney to reabsorb H2O =>excretion of large volumes of dilute urine (25l/day)?

Answer 16

DIabetes Insipidus (ADH Deficiency)

Question 17

Types of Diabetes Insipidus?

Answer 17

NEURAL (cranial) DI (hypothalamus/pituitary lesion)

NEPHROGENIC DI (renal ‘resistance’ to ADH)

• Inherited -mutations in V2 receptor (X-linked) or aquaporin 2 (autosomal)
• acquired -drug-induced (amphotericin B)

Question 18

Diagnosis of Diabetes Insipidus?

Answer 18

Water deprivation test (DI individual will not concentrate urine)

Question 19

Treatment of Diabetes Insipidus?

Answer 19

Desmopressin (Synthetic Vasopressin)
NOT Appropriate to treat nephrogenic DI - resistant to vasopressin!!

Question 20

Which drug can induce Diabetes Insipidus?

Answer 20

Amphotericin B

Question 21

Excess ADH usually caused by GI/Pulmonary tumors that secrete ADH in unregulated function?

Answer 21

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

Question 22

Physiological Role of Oxytocin?

Answer 22

Weak antidiuretic action (similarity to AVP)

Parturition (Childbirth)- Stimulates uterine contractions, can induce labor

Lactation- Milk letdown reflex

Social/mating/emotional behaviour (Love Hormone)

Question 23

______________ triggers myoepithelial contractions to expel milk from mammary alveoli into ducts/collecting chamber. This is known as __________

Answer 23

Oxytocin triggers myoepithelial contractions to expel milk from mammary alveoli into ducts/collecting chambers. This is known as the milk letdown reflex

Question 24

One of the few areas of the brain where the blood-brain barrier is compromised?

Answer 24

Hypothalamus/pituitary is one of the few areas of the brain where the blood-brain barrier is compromised because of fenestrated capillaries

Question 25

All the hormones released by the anterior pituitary are ________

Answer 25

All are **peptide hormones**

Question 26

Hormones that have other endocrine glands as their target?

Answer 26

Trophic Hormone: Triggers release of other hormones

Question 27

Only major Anterior pituitary hormone that is NOT trophic

Answer 27

Prolactin

Question 28

_Regulation of Prolactin_ * ________________ increases release ( ie. during pregnancy) * ________________ inhibits prolactin release (suckling reflex)

Answer 28

_Regulation of Prolactin_ * **Estrogen/progesterone** increases release ( ie. during pregnancy) * **Dopamine** inhibits prolactin release (suckling reflex)

Question 29

Physiological roles of Prolactin

Answer 29

**Lactation (Primary)** - Breast Development/milk production in pregnancy **Immune tolerance**: Prevents body from reacting to fetus **Behavioral**: nurturing instinct/broodiness

Question 30

High levels of ________ inhibits fertility by lowering GNIH => reduction of FSH and LH

Answer 30

High levels of PROLACTIN inhibits fertility by lowering GNIH => reduction of FSH and LH

Question 31

What mediates the Anabolic (growth promoting) effects of Growth Hormone. Where is it produced?

Answer 31

Anabolic (growth promoting) effects mediated by IGF-1 Produced in the liver in response to GH

Question 32

______ is a contrainsulin hormone

Answer 32

Growth hormone is a contrainsulin hormone Insulin lowers plasma glucose, GH increases plasma glucose

Question 33

_______ has insulin like metabolic actions

Answer 33

IGF-I has insulin-like metabolic actions despite being stimulated from the liver by Growth Hormone that is a contra insulin hormone

Question 34

Normal age-related decline in GH (and IGF-I) of ~ _____% between the ages of 20-60?

Answer 34

Somatopause => ~50% decline Linked to signs of aging

Question 35

Growth Hormone Regulation?

Answer 35

Hypoglycemia/Grehlin => Increased GH Exercise: vigorous exercise => Increased GH Somatopause: age-related decline in GH (and IGF-I) ~ 50%

Question 36

_________________ of GH Secretion is essential for normal growth

Answer 36

Pulsatile and circadian pattern of GH Secretion

Question 37

When does the majority of GH secretion occur?

Answer 37

70% daily GH secretion coincides with the onset of deep sleep (REM4)

Question 38

What causes GH Deficiency in Children?

Answer 38

head trauma infections (eg, encephalitis, meningitis), cranial irradiation systemic diseases (eg. leukemia)

Question 39

Symptoms of GH Deficiency in Children?

Answer 39

short stature low growth velocity for age/pubertal stage increased amount of fat around the waist delayed tooth development delayed onset of puberty

Question 40

Main Causes of Adult Onset GH Deficiency?

Answer 40

* pituitary tumors that impair somatotroph function * head trauma * vascular abnormalities of hypophyseal circulation

Question 41

Symtoms of Adult Onset GH Deficiency?

Answer 41

metabolic abnormalities DECREASE lean body mass, INCREASE adiposity osteoporosis psychological disorders

Question 42

________ is important in the maintenance of skeletal muscle and bone and in glucose homeostasis

Answer 42

**Growth Hormone** is important in maintenance of skeletal muscle and bone and in glucose homeostasis

Question 43

Consequences of GH Hypersecretion (Congenital vs Adult)

Answer 43

_Congenital_ (GH excess prior to fusion of epiphyseal growth plate)=> **Acromegalic Gigantism** _Adult Acquired_ (Growth plates fused)=> **Acromegaly** * bone thickening (not lengthening) * metabolic abnormalities similar to type 2 diabetes * increased risk of cardiovascular disease, cancer