Physiology of Hypothalamus and Pituitary gland

Hypothalamus and pituitary gland function in a ----- fashion

coordinated

The pituitary gland consists of an --- and --- lobe

anterior and posterior

The pituitary gland is the master gland and is also known as the ---

hypophysis

The anterior pituitary gland is also called the --

adenohypophysis

The posterior pituitary gland is also called the --

neurohypophysis

The hypothalamus is connected to the pituitary gland by a thin stalk called the ---

infundibulum

The --- nuclei of the hypothalamus releases vasopressin

supraoptic

The --- nuclei of the hypothalamus releases oxytocin

paraventricular

The posterior lobe of the pituitary gland is derived from --- tissue

neural

Vasopressin acts on blood vessels via ----

Vasopressin acts on the kidneys via ---

blood vessels = V1 receptors

kidneys = V2 receptors

--- is located in the supraoptic nuclei within the hypothalamus

vasopressin

--- is located in the paraventricular nuclei within the hypothalamus

oxytocin

The hypothalamus and anterior pituitary are linked directly by --- which will provide most of the blood supply of the anterior lobe

hypothalamic - hypophyseal portal blood vessels

The anterior pituitary gland secretes what 6 hormones?

• Thyroid-stimulating hormone (TSH)

• Follicle-stimulating hormone (FSH)

• Luteinizing hormone (LH)

• Growth hormone (GH)

• Prolactin (PRL)

• Adrenocorticotropic hormone (ACTH)

What kind of hormones does the anterior pituitary gland secrete?

peptide hormones

The portal vessels are both long and short. Capillary plexuses converge to form the ---

long hypophyseal portal vessels

What travels down the infundibulum to deliver blood flow to the anterior pituitary gland from the hypothalamus?

long hypophyseal portal vessels

What type of blood is delivered to the anterior pituitary gland?

venous blood

Which capillary plexuses are in the upper part of the infundibulum?

- long hypophyseal portal vessels

- short hypophyseal portal vessels

long hypophyseal portal vessels

Which capillary plexuses are in the lower part of the infundibulum?

- long hypophyseal portal vessels

- short hypophyseal portal vessels

short hypophyseal portal vessels

Both the long and short hypophyseal portal veins are ---

capillary plexuses

The --- are the main route for hypothalamic hormone delivery and blood flow supply to the anterior pituitary gland

long hypophyseal portal vessels

The ---- help integrate signals from nearby posterior pituitary areas or support local circulation needs

short hypophyseal portal vessels

The unique feature of the blood flow of is that most of the blood that supplies the anterior pituitary is --- blood

venous

True / False: The hypothalamic hormones will not appear in the arterial circulation in high concentrations.

True

Where do hypothalamic hormones appear in high circulation?

hypophyseal portal system (venous blood)

What are the 5 cell types of the anterior pituitary gland?

corticotrophs => ACTH

thyrotrophs => TSH

gonadotrophs => LH/FSH

somatrophs => GH

lactotrophs => prolactin

30-40% of anterior pituitary cells are ---

somatotrophs => GH

Lactotrophs stimulate prolactin production which functions in ---

milk production

Somatotropes stimulate body growth and the secretion of ---

insulin like growth factor

There are portions of the hypothalamus that are not protected by ---

the blood brain barrier

Why are portions of the hypothalamus not connected by the blood brain barrier?

to allow for hormonal feedback loops

What hormones are not controlled by the hypothalamus?

PIGC

PTH

Insulin

Glucagon

Calcitriol

True / False: There are both stimulatory and inhibitory hypothalamic hormones

true

What is the inhibiting hormone of prolactin?

dopamine

What is the inhibitory hormone of growth hormone?

somatostatin

Growth hormone inhibiting hormone is also called ---

somatostatin

Anterior pituitary is highly --- tissue

vascularized

The hypothalamus communicates with the anterior pituitary gland via ---

hypophyseal-hypothalamic portal system (venous blood)

The portal vessels of the hypothalamic - hypophyseal portal system are ---to allow for easy passage of releasing or inhibitory hormones

fenestrated

Flow of hormones into or out of portal systems is by --- and rate is governed by concentration gradients.

diffusion

Flow of hormones into or out of portal systems is by diffusion and rate is governed by ----

concentration gradients

Oxytocin and vasopressin are --- peptides

neuropeptides

Vasopressin is a neuropeptide hormone that is synthesized in the neuron cell bodies from a larger precursor molecule ----

prepropressophysin

Oxytocin is a neuropeptide hormone that is synthesized in the neuron cell bodies from a larger precursor molecule ----

preprooxyphysin

What assists in the axonal transport of vasopressin and oxytocin to the axon terminals in the posterior pituitary gland?

Neurophysins

Neurophysins are ---

carrier proteins

Vasopressin acts via V1 receptors to result in ----

vasoconstriction of endothelium

Vasopressin acts via V2 receptor to control ---

rate of water excretion / absorption

--- helps with milk let down from the mammary gland of the breast

oxytocin

Vasopressin release can be increased due to increased ---- and low --- / ----

increased plasma osmolarity

low blood pressure / low blood volume

Vasopressin enters systemic circulation and can bind to either --- or --- receptors

V1 receptors = blood vessels

V2 receptors = kidneys

The ---- is another region that can induce the secretion of AVP (outside of the posterior pituitary gland)

anteroventral region of the third ventricle (AV3V)

What does does angiotensin II act on to stimulate vasopressin secretion?

via anteroventral region of the third vesicle

AV3V stands for

anteroventral region of the third vesicle

Negative feedback loops can control the level of vasopressin activation at the level of the ---

hypothalamus

Osmoreceptors are sensitive to changes in ---

plasma osmolarity

Vasopressin secretion can occur only within --- increase in plasma osmolarity

1-2 mOsm

What do osmoreceptors stimulate when there is a change in plasma osmolarity ?

supraoptic nuclei of the hypothalamus to secrete vasopressin

True / False: vasopressin is secreted when there is a decrease in plasma osmolarity

false

What happens when there is an increase in plasma osmolarity?

blood becomes more concentrated = less water

What happens when there is a decrease in plasma osmolarity?

blood is less concentrated = more water

Maximum vasopressin secretion occurs at --- mOsm/L

295

---- in plasma osmolarity inhibits vasopressin release

decrease

SIADH

Syndrome of Inappropriate Anti-Diuretic Hormone secretion

What happens to vasopressin (anti-diuretic hormone) in SIADH?

vasopressin (anti-diuretic hormone) is high

In SIADH in tumors, feed-back inhibition is ---

lost

What happens to plasma osmolarity and sodium with SIADH?

low plasma osmolarity = too much water retention

low sodium = too much water dilutes salt

The absence of AVP can be --- diabetes insipidus or --- diabetes insipidus

central

nephrogenic

What happens to vasopressin (anti-diuretic hormone) in diabetes inspidus (central / nephrogenic)?

too little vasopressin (anti-diuretic hormone)

Central diabetes insidious is failure to release vasopressin at the level of the ---

pituitary gland

Nephrogenic diabetes insipidus is failure to respond to vasopressin at the level of the ---

kidneys

In which condition do patients have dilute urine and hyper osmotic plasma concentration?

- SIADH

- diabetes insipidus

- diabetes insipidus

In which condition do patients have concentrated urine and low osmotic plasma concentration?

- SIADH

- diabetes insipidus

- SIADH

In which condition will a patient have hypernatremia?

- SIADH

- diabetes inspidus

- diabetes inspidus

In which condition will a patient have hyponatremia?

- SIADH

- diabetes inspidus

SIADH

What can patients with central diabetes insipidus be treated with?

Desmopressin (AVP)

True / False: Women who are pregnant can develop gestational diabetes insipidus during the third trimester.

true

Women who are pregnant can develop gestational diabetes insipidus during the --- trimester.

third

What causes gestational diabetes insipidus?

placental vasopressinase

Destruction of the neurohypophysis or mutations in AVP results in ---

central diabetes insipidus

Renal resistance to AVP results in ---

nephrogenic diabetes insipidus

Decreased response to AVP results in --

nephrogenic diabetes insipidus

Excessive activity of placental vasopressinase results in ---

gestational diabetes insipidus

Patient with diabetes insipidus have a high risk of becoming --- and have a higher incidence of xerostomia --- increasing caries risk

dehydrated

Oxytocin stimulates --- contraction

smooth muscle

--- is the primary stimulus for lactogenesis in late pregnancy and the postpartum period

Prolactin

--- stimulates milk production and --- stimulates milk release / ejection

prolactin = milk production

oxytocin = milk release / ejection

Oxytocin induces smooth muscle contraction through --- to increase intracellular calcium

G-alpha-q-dependent pathway (GPCR)

What are the 3 functions of oxytocin?

smooth muscle contraction

milk let down / ejection

promotion of maternal and social bonding behavior

Oxytocin promotes --- and --- bonding behavior

maternal and social

What drug is an oxytocin against used for labor induction and as a uterotonic to decrease post part hemorrhage?

Pitocin

What is the difference in release between oxytocin and prolactin?

oxytocin = posterior pituitary

prolactin = anterior pituitary

Suckling inhibits the release of --- which removes the negative signaling

dopamine

Suckling is a --- feedback pathway

positive => stimulates continued release of oxytocin / prolactin

Secretion of prolactin is under negative control by ---

dopamine

---- are the most common anterior pituitary adenoma

prolactinoma

Hyperprolactiemia presents with ---

galactorrhea

Galactorrhea

inappropriate or spontaneous flow of milk or milk-like discharge from the breast unrelated to childbirth or nursing

Hyerprolactinemia can lead to ---

hypogonadism