Hypothalamic Pituitary Axis, GH

Question 1

Where is the pituitary found?

Answer 1

Beneath the hypothalamus in a socket of bone: sella turcica

Question 2

Describe the structure of the pituitary gland

Answer 2

2 parts =

Anterior: primitive gut tissue (upward growth).

Posterior: primitive brain tissue (down growth from brain)

Question 3

What is the name of the pituitary stalk?

Answer 3

Infundibulum

Question 4

What is the neurocrine function of the posterior pituitary?

Answer 4

Oxytocin, ADH (vasopressin)

prod by supraoptic and paraventricular nuclei of hypothalamus –

Transported down nerve cell axons

stored and secreted by PP

Question 5

What is the process of the anterior pituitary releasing hormones

Answer 5

Hormones synthesised in hypothalamus, 
transported down axons, 
stored in median eminence, 
released into hypophyseal portal system  (blood),
effecting release of hormones from AP

Question 6

Name the hormones produced by the hypothalamus (7+2)

Answer 6

ANTERIOR
TRH Thyrotropin releasing hormone,
(PRH) Prolactin releasing hormone = TRH (minor +ve control on prolactin),
PIH Prolactin release-inhibiting hormone (Dopamine),
CRH Corticotropin releasing hormone,
GnRH Gonadotropin releasing hormone,
GHRH Growth hormone releasing hormone,
GHIH Growth hormone-inhibiting hormone (Somatostatin).

POSTERIOR
OT oxytocin,
ADH antidiuretic hormone

Question 7

What is the diff between tropic and trophic?

Answer 7

Tropic = affects release of other hormones in target tissue.

Trophic = affects growth

Question 8

Briefly describe the biological roles of hormones prod by the hypothalamus

Answer 8

6 tropic hormones effect release of anterior pituitary hormones.

2: OT/ADH prod to be released by posterior pit

Question 9

Name the hormones produced by the anterior pituitary gland (6)

Answer 9

TSH Thyroid stimulating hormone, 
ACTH Adrenocorticotropic hormone, 
LH Luteinising hormone, 
FSH Follicle stimulating hormone, 
PRL Prolactin, 
GH Growth hormone

Question 10

What is the role of TSH?

Answer 10

Secretion of thyroid hormone from thyroid gland

Question 11

Outline the function of ACTH: adrenocorticotropic hormones

Answer 11

Secretion of hormones from adrenal cortex

Question 12

What is the role of LH - luteinising hormone?

Answer 12

Ovulation and secretion of sex hormones

Question 13

Describe the function of FSH: follicle stim hormone?

Answer 13

Devel of eggs and sperm

Question 14

What is the function of PRL: prolactin?

Answer 14

Mammary gland devel and milk secretion

Question 15

What is the function of GH?

Answer 15

Prod by anterior pit – stim liver/skeletal muscle to prod IGFs = stim bone/cartilage growth, stim long bone growth.

Adults – GH/IGFs = maintain muscle/bone mass, healing, tissue repair, modulates metabolism

Question 16

What are the pathways of the hypothalamic and anterior pituitary regulated by?

Answer 16

-ve feedback loops

Question 17

What factors influence growth?

Answer 17

Genetics, nutrition, environment, hormones

Question 18

Describe the factors controlling GH secretion

Answer 18

CNS inputs into hypothalamus controlling levels:

GHRH = increase secretion.

Somatostatin = decreased secretion.

Increase = deep sleep, stress, exercise, low glucose/FA, fasting.

Decrease = REM sleep, high glucose/FA, obesity

Question 19

Describe the long and short loop –ve feedback that controls GH

Answer 19

Long loop: mediated by IGFs

Short loop: mediated by GH

Question 20

Describe how GH exerts its effects on cells directly?

Answer 20

Activate janus kinases = activation of signalling pathways = transcription factor activation and IGF prod

Question 21

How does GH exert its effect indirectly through Insulin like growth factors?

Answer 21

IGF1 (adult growth))/IGF2 (foetal growth) – binding proteins modulate their availability = paracrine/autocrine/endocrine.

Activation of IGF receptors modulate: hypertrophy, hyperplasia protein synthesis, lipolysis

Question 22

Which hormones are on -ve control?

Answer 22

GH, LH/FSH, TSH, ACTH

Question 23

Which hormones are on +ve control?

Answer 23

Prolactin

Question 24

What is +ve feedback vs -ve?

Answer 24

-ve feedback = rate of process decreases as conc of product increases.

+ve feedback = rate of a process increases as conc of product increases

Question 25

What are the nuclei of the hypothalmus?

Answer 25

Suprachiasmatic = biological clock

Arcuate = regulate appetite

Paraventricular = oxytocin

Supraoptic = ADH

Question 26

Which hormone inhibits the release of GH?

Answer 26

Somatostatin = GH inhibiting hormone