Hypothalamic-pituitary Axis (week 1)

Question 1

What is the hypothalamic-pituitary axis and what does it do

Answer 1

It is the most dominant part of the entire endocrine system system

The HPA regulated function of the thyroid, adrenal gland and reproductive glands and controls somatic growth, lactation, milk secretion and water metabolism

Question 2

How is the pituitary gland sat in the brain

Answer 2

It is sat in a depression

Question 3

What is the infundibular recess

Answer 3

Commonly illustrated as a v-shaped hollow in the sagital view is recognised as a small a extension of the third ventricle into the pituitary stalk

Question 4

What are the 2 main compartments of the pituitary gland

Answer 4

Posterior and anterior pituitary gland

Question 5

Explain the primary and secondary plexus

Answer 5

Blood supply and lymphatics

The superior hypophseal portal system form the primary plexus

This plexus supplies blood to the median eminence. The blood from the median eminence would then drain via the hypophyseal portal veins in a secondary plexus.

Question 6

What is the name of the stalk between the hypothalamus and the posterior pituitary gland

Answer 6

Infundibulum

Question 7

Which pituitary gland is directly connected to the hypothalamus

Answer 7

The posterior

Question 8

How does the hypothalamus communicate with the anterior pituitary gland

Answer 8

Hypophyseal system

Question 9

How does the hypothalamus communicate with the posterior pituitary gland

Answer 9

Nerve impulses

Question 10

Which hormones are secreted from the (neurohypophysis) posterior pituitary gland

Answer 10

ADH
Oxytocin

Question 11

Which hormones are secreted from the (adenohypophysis) anterior pituitary gland

Answer 11

FSH
LH
ACTH
Prolactin
GH

Question 12

And ANT and POST pituitary gland develop from the same tissue or not

Answer 12

No they don’t

Question 13

What is neuropophysis

Answer 13

Downgrowth of the forebrain - posterior

Question 14

What is adenohypophysis

Answer 14

Oral ectoderm of the roof of stomatodeum

Question 15

What is the primary plexus important for

Answer 15

Anterior pituitary gland

Question 16

What is the secondary plexus important for

Answer 16

It is important for both anterior and posterior pituitary gland

Question 17

adenohypophysis cells

Answer 17

endocrine tissue with distinct cell types responsible for releasing different hormones
- somatotropes - produces growth hormone
- Corticotropes - secrete adrenocorticotropic hormone (ACTH), stimulates adrenal gland to release cortisol
- Thyrotropes - produces thyroid stimulating hormone
- Gonadotropes - produces Luteinizing hormone (LH) and follicle- stimulating hormone (FSH)
- Lactotropes - secretes prolactin

Question 18

neurohypophysis cells

Answer 18

neural tissue which is responsible for transport and storage of secretory granules of hormones in the hypothalamus

Question 19

what is ADH secretion stimulated by

Answer 19

increased plasma osmolality
decrease in blood pressure
stress
pain

Question 20

physiological effects of ADH

Answer 20

increases permeability of the collecting ducts and distal convoluted tubule allowing for better water reabsorption from the urine back into the blood stream

in presence of ADH urine flow decreases and urine osmolality increases where as in the absence of ADH urine flow increases and urine osmolality decreases.

maintaining blood pressure: can cause vasoconstriction, can cause narrowing of the blood vessels. In conditions where blood volume is reduced, such as during dehydration, ADH secretion is increased to help maintain blood pressure.

Question 21

what can abnormally high ADH lead to

Answer 21

high urine osmolality
oedema (due to high plasma volume
low plasma osmolality

Question 22

what can abnormally low ADH lead to

Answer 22

diabetes insipidus - inability of the kidneys to concentrate urine properly, can result in excretion of high volumes of dilute urine leading to dehydration.

Question 23

what does oxytocin do

Answer 23

stimulates secretion of breast milk from lactating females
may also contribute to parturition of a foetus

Question 24

oxytocin secretion

Answer 24

secretion of oxytocin is stimulated by
-suckling
-vaginal/ cervical stimulation
-crying
-during social event
-during hugging, kissing

Question 25

oxytocin physiological effects

Answer 25

It stimulates the contraction of the cells around the mammary glands, causing the milk to be ejected from the breasts. This helps ensure an adequate milk supply for nursing infants.

reduction in stress

Question 26

summary of the adenohypophysis hormones

Answer 26

parvicellular neuronal cell bodies in the hypothalamus –> adenohypophysis (anterior pituitary gland) —-> end organ or peripheral endocrine gland

Question 27

TSH

Answer 27

regulates thyroid function via the TSH receptor in the thyroid epithelial cells.
stimulates the release of T3 and T4 to support tropic effects on growth and metabolism

Question 28

FSH and LH

Answer 28

regulate the function of the gonads in both males and females via the FSH and LH receptors on the gonads

Question 29

ACTH

Answer 29

adrenocorticotropic hormone, responsible for stimulating the adrenal cortex via the MC2R receptor. This induces upregulation of circulating cortisol and adrenal androgen. The released cortisol negatively feeds back to inhibit ACTH secretion in the anterior pituitary

Question 30

GH

Answer 30

regulates metabolism via the GH receptor in the liver. The resulting insulin like growth factor 1 (IGF-1) produced negatively feeds back on the production and secretion of GH. This negative feedback is due to the direct effects of IGF-1 and release of somatostatin from the hypophysiotropic hormone somatostatin

Question 31

prolactin

Answer 31

stimulates manufacture of breast milk via the reduced release of dopamine from the parvicellular hypothalamic neurons

Question 32

what is a key feature of HPA

Answer 32

the ability of tropic hormones to provide negative feedback upon the system thanks to the hormones they induce release of in their target organs/ endocrine glands.