Hypothalamus-Pituitary-target Organ Axes: Feedback Control 1

Question 1

What are the sites of control of hormone production and secretion?

Answer 1

Hypothalamus and Pituitary Gland

Question 2

What are the hypothalamus and Pituitary glands responsible for and what do they regulate the function of?

Answer 2

They are responsible for somatic growth, lactation, and milk secretion.
They regulate the function of the Thyroid, Adrenal, and Reproductive Glands

Question 3

Where is the hypothalamus located?

Answer 3

Below the thalamus and above the pituitary on either side of the third ventricle in the brain

Question 4

How large is the Hypothalamus with relation to the total brain mass?

Answer 4

Less than 1%

Question 5

What areas of the brain and spinal cord are connected to the hypothalamus?

Answer 5

The limbic system and autonomic brain stem areas

Question 6

What are the external and internal signals that the hypothalamus receives?

Answer 6

External: Sensory pathways conveying info on external environment
Internal: Internal receptors conveying body temperature, Osmolarity, pressure, volume, glucose concentration, and hormone concentration.

Question 7

True or False: The hypothalamus is an interface between the internal and external environment

Answer 7

True

Question 8

What are the external responses governed by the hypothalamus?

Answer 8

Emotional, instinctual, appetite

Question 9

External responses have connections with which part of the nervous system?

Answer 9

Central Nervous System CNS

Question 10

Where are internal homeostasis responses produced?

Answer 10

ANS and endocrine system

Question 11

What is the endocrine link of the hypothalamus?

Answer 11

It is the Hypothalamic Pituitary axis

Question 12

True or False: The anterior and posterior are physiologically distinct portions that result from different sources embryonically AND are linked differently to the hypothalamus

Answer 12

True

Question 13

Where is the pituitary gland located?

Answer 13

It lies in the Sella Turcica in a bone cavity at the base of the base

Question 14

Compare and contrast the Anterior and Posterior Pituitary with regards to their origin and nature of cells.

Answer 14

Anterior pituitary: Arises from an upward and outward pouching from the epithelium of the phalanx (Rathke’s Pouch). Epitheloid nature of cells

Posterior Pituitary: Arises from a neural tissues outgrowths from the hypothalamus (extension of the hypothalamus). Glial-type cells found.

Question 15

What is Rathke’s pouch

Answer 15

It is the part of the epithelium of the pharynx where the anterior pituitary pouches from

Question 16

Briefly describe the connection of the pituitary to the hypothalamus

Answer 16

The posterior pituitary connects to the hypothalamus via a neutral pathway
The anterior pituitary connects via a unique vascular link

Question 17

Describe the structure and function of the posterior pituitary gland

Answer 17

The posterior pituitary gland forms a neuroendocrine system consisting of neuro secretory neurons whose cell bodies lie in two well defined clusters located in the hypothalamus. These clusters are the Supraoptic and the paraventricular nuclei. Axons of these neurons pass through the stalk and terminate at the capillaries within the posterior pituitary. The posterior pituitary does not produce its own hormones but it is the nuclei of the neurosecretory neurons.

Question 18

What are the clusters related to the posterior pituitary and where are they found?

Answer 18

Supraoptic and paraventricular

They are found in the hypothalamus

Question 19

What does each cluster of the posterior pituitary produce?

Answer 19

Supraoptic produces vasopressin (ADH)

Paraventricular produces Oxytocin

Question 20

Where are the hormones of the posterior pituitary produced?

Answer 20

Supraoptic and paraventricular nuclei of the neurosecretory neurons in the hypothalamus

Question 21

What are the two hormones secreted by the posterior pituitary gland?

Answer 21

Vasopressin and oxytocin

Question 22

Trace the path of vasopressin or ADH

Answer 22

Vasopressin is produced in the cell bodies of the supraoptic nuclei. They then travel down the stalk to the nerve endings in the posterior pituitary gland where they are stored. To be transported that must combine with carrier proteins called Neurophysins. When needed, it will be released to circulation (towards kidney)

Question 23

How long does it take for hormones to be transported from the cell body in the hypothalamus to the posterior pituitary

Answer 23

Several days (slow)

Question 24

True or False: The paraventricular nuclei can synthesize ADH

Answer 24

True, now fuck off
Okay so each nuclei can synthesize 1/6 as much of the second hormone as of its primary hormone => not exclusively produced in either nuclei

Question 25

How is the hormone stored in the pituitary gland and how does it change when it is secreted?

Answer 25

The hormone is stored combined with neurophysins. When secreted through exocytosis, they separate immediately.

Question 26

What are the carrier proteins that bind to the hormones in the Hypothalamic-posterior pituitary stalk

Answer 26

Neurophysins

Question 27

True or False: Does the Anterior pituitary synthesize its own hormones

Answer 27

True

Question 28

What are all the hormones that are synthesized by the anterior pituitary and state which are tropic

Answer 28

``` Growth Hormone (Somatotropin) Adrenocorticotropin Hormone (ACTH) Thyroid-stimulating Hormone (TSH) Follicle Stimulating Hormone (FSH) Leutinizing Hormone (LH, ICSH) Prolactin All tropic except prolactin ```

Question 29

Another name for Growth hormone

Answer 29

Somatotropin

Question 30

Define Tropic hormones

Answer 30

Hormones that stimulate the secretion of another hormone

Question 31

What hormone(s) produced by the posterior pituitary gland are non-tropic

Answer 31

Oxytocin and Vasopressin | Lol

Question 32

What hormone(s) produced by the anterior pituitary are non-tropic?

Answer 32

Prolactin

Question 33

What hormone does ACTH leads to secrete?

Answer 33

Cortisol

Question 34

What are the different cell types of the anterior pituitary and what does each produce? List them in order of most to least prevalent

Answer 34

``` Somatotropes -> GH (30-40%) Corticotropes -> ACTH (20%) Gonadotropes -> FSH and LH Lactotropes -> Prolactin Thyrotropes -> TSH Gonadotropes and Lactotropes can switch in order ```

Question 35

How does the anterior pituitary know when to secrete hormones? Discuss the mechanism including the vascular link.

Answer 35

The hypothalamus releases Hypothalamic releasing and Hypothalamic inhibitory hormones (or factors). They are secreted within the hypothalamus through the vascular link in a system called the Hypothalamic Hypophyseal Portal System. It begins in the base of the hypothalamus called the Median Eminence. A group of capillaries recombine into small portal vessels and pass down the stalk. Portal vessels then branch to form most of the anterior pituitary capillaries before draining into the systemic venous system.

Question 36

Does the blood first pass through the hypothalamus or the anterior pituitary? Why?

Answer 36

Almost all blood supplied to the anterior pituitary must first pass through the hypothalamus. This is due to the fact that blood must flow in that direction to move the hormones => immediate delivery AND this allows the hormones to bypass general circulation.

Question 37

Where does the hypothalamic hypophyseal portal start and end

Answer 37

Starts when the capillaries join and ends when the capillaries branch.

Question 38

What are the 2 factors that regulate anterior pituitary hormone secretion?

Answer 38

Hypothalamic hypophysiotropic hormones | Feedback by target gland hormones

Question 39

What type of hormones are the hypothalamic hypophysiotropic hormones?

Answer 39

(Small) Peptide hormones

Question 40

True or False: A Hypothalamic Hypophysiotropic Hormone can have more than one effect AND a single pituitary hormone may be regulated by two or more hypothalamic hypophysiotropic Hormone. Oh, and when you’re done state an example if any part (or both or none) are true

Answer 40

True Example 1: PIH is identical to Dopamine; GHIH inhibits the release of GH and TSH Example 2: Growth Hormone is regulated by GHRH and GHIH (Releasing and inhibitory).

Question 41

State the effect of the following hormones on the Anterior Pituitary Gland. In the end state what the hormones I mentioned are called and another name for number 5 and another hormone that has the same role as number 6 :) 1. Thyrotropin-releasing hormone (TRH) 2. Corticotropin-releasing hormone (CRH) 3. Gonadotropin-releasing hormone (GnRH) 4. Growth hormone releasing hormone (GHRH) 5. Growth hormone inhibiting hormone 6. Prolactin inhibiting hormone (PIH) 7. Prolactin Releasing Hormone

Answer 41

1. Stimulates the release of TSH (thyrotropin) and Proline 2. Stimulates release of ACTH (corticotripin) 3. Stimulates release of FSH and LH 4. Stimulates release of GH 5. Inhibits release of GH and TSH 6. Inhibits release of Prolactin 7. Stimulates release of Prolactin For number 5 another name is somatostatin For number 6 Dopamine

Question 42

Distinguish between Ultrashort, short, and long feedback loops. Give an example of a long feedback loop.

Answer 42

Ultrashort = Hypothalamic hormones inhibit their own secretion via autocrine effects Short = Pituitary hormones inhibit the release of hypothalamic hormones Long = Hormones from peripheral endocrine glands inhibit the release of hypothalamic and pituitary hormones An example of a long one is cortisol.

Question 43

Where do the capillaries of the anterior pituitary directly drain into

Answer 43

The systemic venous system