HR Lesson 10: Adrenal Medulla

What hormone is primarily produced by the adrenal medulla?

Epinephrine

Where is the adrenal medulla located?

Inner portion of the adrenal gland, surrounded by the adrenal cortex

What is the adrenal medulla primarily made up of?

Chromaffin cells

What are chromaffin cells?

Modified postganglionic sympathetic neurons (no axon just body)

What is the main nerve innervation to the adrenal gland?

Pre-ganglionic sympathetic nerves

What is the adrenal medulla considered?

Specialized part of the sympathetic nervous system

How are the chromaffin cells organized?

Organized in cords that are richly vascularized to facilitate rapid hormone secretion

What stimulates epinephrine production?

Cortisol, chromaffin cells directly receive cortisol from the adrenal cortex through portal veins

What kind of hormone is epinephrine considered?

Amine because it comes from Tyrosine

What happens when there is too much noradrenaline?

Negative feedback loop tells tyrosine hydroxylase to stop making DOPA from Tyrosine

What is the main stimulus of catecholamine secretion?

Stress or sympathetic nervous system activation

What does the adrenal medulla do?

Works with the sympathetic nervous system to control the body’s response to ACUTE stress

Pathway of epinephrine secretion

Sympathetic NS stimulation or stress —> secretes ACTH to the adrenal medulla where cortisol stimulates epinephrine production

What are the metabolic effects of epinephrine secretion?

Increased glycogenolysis and glucose release into the bloodstream to provide immediate energy

What are the CV effects of epinephrine secretion?

Increased HR

Vasodilation in skeletal muscles

Vasoconstriction to skin, GI, and kidneys (restrict blood flow to non-essential organs during fight or flight)

What are the respiratory effects from epinephrine stimulation?

Bronchodilation to increase oxygen supply

Effect on vision from epinephrine stimulation?

Pupil dilation (mydriasis)

Are dysfunctions of the adrenal medulla common?

No, very rare.

What is a pheochromocytoma?

Catecholamine secreting tumors of chromaffin cells

More frequent in dogs then cats

What are some clinical signs of a pheochromocytoma?

Tachycardia and hypertension due to acting on alpha 1 and beta 1 adrenoreceptors

Clinical signs for dysfunction of the adrenal medulla?

Weight loss and muscle wasting due to increased metabolic rate and excessive breakdown of fat and muscle causing weight loss

Increased energy expenditure

Appetite suppression