SI3107- Hypothalamus-Pituitary Axis

Paracrine Hormones

acts on neighbouring cells ie clotting factors

Autocrine

acts on the same cell that secreted them

Juxtacrine

Contact between cells, ligand on one cell surface binds to the receptor on the other cell

Intracrine

hormone acts inside a cell

When hormones involve a 2nd messenger what type of hormone are they usually?

Amino acid-based hormones that act on GCPR

cAMP signalling cascade

-ligand binds

-Activation G, conformational change, GTP

-alpha subunit activates effector ie adenylate cyclase

-cAMP generation

-cAMP activates protein kinase A

IP3 signalling

• ligand binds, conformational change

• GTP- aq subunit, energy to go to effector

• phospholipase C, liberation of DAG and IP3 from PIP2

• IP3 ^ Ca2+ levels, DAG+Ca2+ = activate PK C

Hormone signalling

• unbound hormones diffuse into the cell

• bind to receptor in cytoplasm/nucleus (sometimes membrane)

• receptor-hormone complex binds to DNA and activates 1< genes

• creation of mRNA- moves out into the cytoplasm

• Translation of new proteins

functions of hypothalmus

• endocrine regulation

• hormone production

• ANS regulation

• circadian rhythm regulation

• limbic system interaction

• temp regulation

• thirst centres

How is it connected to the pituitary gland?

infundibulum

What’s another word for anterior pituitary gland

adenohypophysis

What’s another name for the posterior pituitary

neurophypophysis

How is the anterior pituitary gland connect to the hypothalamus

hypophyseal portal system

How is the posterior pituitary connected to the hypothalamus?

hypophyseal tract- neurons

is is the p.p. not considered an endocrine gland?

Because it doesn’t actually produce hormones it just stores and releases ADH and OXT that the hypothalamus produces

Why is the portal systems one-way system effective?

As it allows the hypothalamic hormones to be transported to the anterior pituitary first without entering the systemic circulation

Where is ADH produced?

Supraoptic nucleus

Where is OXT produced?

Paraventricular nucleus

herring bodies?

terminal axons, storage site for hormones

Trophic hormone?

Hormone that stimulates another endocrine gland

Name the cells of the Anterior pit.+ what they secrete

• Somatotrophs( hGH)

• Thyrotrophs(TSH/ thyrotropin)

• Gonadotrophs(FSH/LH)

• Lactotrophs(Prolactin)

• Corticotrophs(ACTH/MSH/corticotropin)

What stimulates hGH?

• exercise

• fasting

• Oestrogen + testosterone

• first 2hr of sleep

• trauma/injury

hGH release

Stimulated by - GHRH

which stimulates both cAMP and IP3 pathways in anterior pit

Inhibition of hGH

GHIH

Gi= decrease cAMP

What is it effects mediated by

somatomedins

-insulin-like growth factors

IGF-1- adults/ children

IGF-2 - in utero

Control of Thyroid Hormone Release

• TRH

• TSH

Calmodulin

Ca++ binds to it, then it interacts with other proteins,

signal transducer

What signalling pathway does GHRH stimulate?

cAMP and IP3- think peptide

What does GHIH stimulate

Gi

What type of receptors do GH and prolactin bind to?

Cytokine receptors