The hypothalamo-adenohypophysial axis

Question 1

Where does the pituitary gland/ hypophysis lie?

Answer 1

Sella Turcica (bony dip at base of brain)

Question 2

Diagram of brain, pituitary gland, hypothalamus and other structures
Slide 3, lecture 2

Answer 2

-

Question 3

Diagram of adenohypohysis

Slide 4, lecture 2

Answer 3

-

Question 4

Diagram of hypothalamic- hypophysial portal circulation

Slide 5, lecture 2

Answer 4

-

Question 5

Hypothalmic nucleus definition

Answer 5

Collection of neuronal cell bodies

Situated in hypothalamus

Question 6

Hypothalmic neurone start+ possible terminations
Property?
Neurotransmitter fate?

Answer 6

Neurone starts in hypothalamus from hypothalamic nuclei
Leaky
Can go to posterior hypothalamus or:
Median eminence, lie on primary capillary plexus= hypothalamus controls anterior pituitary function
Neurones release neurosecretion which get into the blood flowing through primary capillary plexus+ transported to secondary capillary plexus anterior pituitary+ stimulate release of anterior pituitary hormones from secretory cells only responsive to particular neurosecretion

Question 7

Somatotrophs produce?
What regulates it?
Target cells?
Stimulated by?

Answer 7

Growth hormone (Somatotrophin)

Growth hormone releasing hormone (GHRH), also called somatotrophin releasing hormone= stimulatory
Stomatostatin= inhibitory

General body tissues, particularly liver

Fasting
Exercise
Oestrogens
Stress
Sleep

Question 8

Adenohypophysial cells

Answer 8

Somatotrophs
Lactotrophs
Thyrotrophs
Gonadotrophs
Corticotrophs

Question 9

Lactotrophs produce?
What regulates it?
Target cells?

Answer 9

Prolactin

Dopamine= inhibitory (increased hormone= decreased prolactin)
Thyrotrophin releasing hormone (TRH)

Breasts (lactating women)

Question 10

Thyrotrophs produce?
What regulates it?
Target cells?

Answer 10

Thyroid Stimulating Hormone (TSH)
Other name= thyrotrophin

Thyrotrophin releasing hormone (TRH)= stimulatory

Thyroid

Question 11

Gonadotrophs produce?
What regulates it?
Target cells?

Answer 11

Luteinising Hormone (LH)
Follicle Stimulating Hormone (FSH)

Gonadotrophin Releasing Hormone (GnRH)= stimulatory

Testes (Men)
Ovaries (Women)

Question 12

Corticotrophs
Hormone acts on?
What regulates it?
Target cells?

Answer 12

Adrenocorticotrophic Hormone (ACTH)
Also named Corticotrophin
Acts on adrenal cortex

Corticotrophin releasing hormone (CRH)= stimulatory
Vasopressin (VP)= stimulatory

Adrenal Cortex

Question 13

Where are adenohypophysial hormones stored?

Answer 13

Secretory granules

Released by exocytosis

Question 14

Protein hormones

Answer 14

Growth hormone (somatotrophin)
Prolactin
Both quite big

Question 15

Glycoprotein hormones

Answer 15

Thyroid Stimulating Hormone (Thyrotrophin)
2 gonadotrophins
Leuteinising Hormone (LH)
Follicle Stimulating Hormone (FSH)
both have same α subunit, have different β subunits

Question 16

Polypeptide hormones

Answer 16

Adrenocorticotrophic Hormone (Corticotrophin) (ACTH)
smaller than protein hormones

Question 17

Action of GH

Negative feedback loops?

Answer 17

Adenohypophysis- stomatotrophs→ Growth Hormone→Body tissues+ metabolic actions→ growth+ development

Adenohypophysis- somatotrophs → Growth hormone→ Liver (hepatocyte receptors)→ Somatomedins (IGF1+ IGF II (more relevant in foetus))→ body tissues+ metabolic actions→ growth+ development

Somatomedins negative feedback on hypothalamic nuclei= decreased GHRH+ increased SS, also on secretory cells releasing GH
GH negative feedback on hypothalamic nuclei= decreased GHRH

Question 18

Metabolic effects of GH

GH excess?

Answer 18

Stimulation of amino acid transport into cells+ protein synthesis
Increased gluconeogenesis (diabetes in excess)
Lipolysis stimulation= increased fatty acid production
Increased cartilaginous growth+ somatic cell growth (predispose to malignancy in excess)

Question 19

Milk production

Answer 19

Suckling= stimulation of tactile receptors → afferent neural pathway→ suppression of hypothalamic dopaminergic neurones→ less dopamine produced→more prolactin secreted → efferent endocrine pathway→ milk production