BIOA 2006 - Lecture 14: HPA axis

The paired glands are

adrenal glands

adrenal glands are located at

craniomedial ends of each kidney

Adrenal cortex produces

steroid hormones

The adrenal cortex in made of three layers (out to in)

Glomerulosa, fasciculata, retiuclaris

glomerulosa produces

mineralocorticoids (electrolyte balance)

fasciculata produces

glucocorticoids

reticularis produces

androgens

the adrenal medulla is derived from the

neural tube, Symp NS

the adrenal medulla produces

epinephrine and norepinephrine, stimulated by the SNS

epinephrine and norepinephrine are inactivated in the ____________ and excreted in _______________

liver, urine

Cells of adrenal cortex take up _____________from plasma to synthesize the steroids. This is catalyzed by the enzyme _______________

cholesterol, P-450scc

P-450scc is regulated by

ACTH

Mineralocorticoids are important for ionic balance (Na +, K +) and secreted primarily regulated by

the kidney

______________ are weak in comparison to gonadal steroids, and relatively unimportant. Released in response to ACTH along with GC's.

adrenal androgens

dominant glucocorticoids are

cortisol in mammals and corticosterone in rodents, birds, fish

Glucocorticoids are aka

stress hormones

effects of Glucocorticoids

-permissive for other hormone actions

-increase plasma glucose, prevent glucose uptake and stimulating gluconeogenesis

-mobilizes FAs and AAs

-inhibits DNA synth

-inhibit immune function

-lung maturation of fetus

glucocorticoids are anti-_________________________ steroids

inflammatory

Deficiency of GCs causes

addison's disease

Addison's disease is common in

human and dogs

Addison's is associated with high levels of

ACTH

Addison's symptoms

reduced ability to deal with stress, weakened immune system; low blood glucose

Excess GCs causes

Cushing's

Cushing's is common in

dogs, cats, horses, humans

tumours where can cause Cushing's

pituitary tumour of corticotropes, or by adrenal cortical tumour

Cushing's symptoms

high cortisol

overeating/drinking

poor coat & skin

muscle weakness

osteoporosis, diabetes

increased risk of infection

large abdomen, fat pad on back of neck (& round face in humans)

autoimmune destruction of adrenal cortical cells is associated with

Addison's or GC deficiency

ACTH has a slight releasing effect on

sex hormones

Why is plasma control used as an indicator of stress

Stress causes CRH release, causing increased plasma control

CRH / ACTHRH

corticotropin releasing hormone

two glucocorticoids

cortisone & corticosterone

ACTH is controlled by the

Hypothalamus via CRH

ACTH stimulates growth and development of

adrenal cort and adrenal glands and stimulates glucocorticoid and androgen synthesis from adrenal cort

the secretion of CRH is

episodic, pulses every 1-3 hours

Curcadian rythm helps dictate CRH-ACTH-GC levels such that they rise

in the last few hours of sleep and peak after awakening shortly

The production of GCs is regulated by the ______ axis

HPA

CRH (Hypothalamus) - ACTH (Ant pit) - Cortisol (Cortex of adrenal gland)

The production of gonadotropin hormones is regulated by the _____ axis

HPG axis

GnRH (Hypothalamus) - FSH&LH (Ant pit) - Sex hormones (gonads)

2 gonadotropins

FSH and LH

Gonadotropins produces in the

the anterior pituitary gland in cells called gonadotropes

gonadotropins are

trophic (cause growth of gonads)

secretion of gonadotropins is either

pulsatile or seasonal

most sex steroids negative feedback/inhibit GnRH production and LH/FSH from hyp and ant pit, with the exception of

estrogen (pos feed back prior to ovulation)

FSH Stimulates follicle development in females and what in males

maturation of sperm

FSH stimulates production of

inhibin

inhibin negatively deeds back on

FSH

In males, LH stimulates

testosterone production

in females, estrogen stimulates

estrogen from follicles or progesterone from CL

Surges in LH cause

ovulation

Cells are _____________ in response to LH

luteinized (forming CL, maintains preg)

the granulosa cells of ovulated follicles form the

CL

CL secretes

progesterone and estradiol

In testes, LH binds to receptors on

leydig cells

Theca cells are in the

ovary

Theca cells respond to LH by

secreting testosterone

testosterone secreted by theca cells is converted into

estrogen by granulosa cells in the developing follicle

The androgen with high biological activity that is anabolic to skeletal muscle and the male repro tract is

testosterone

The dominant estrogen in mammals that is anabolic to skeletal muscle & female reproductive tract

estradiol 17beta

A member of progestin family of steroids that is involved in preparation & maintenance of pregnancy

progesterone