Final Endo: CH. 11 Adrenal Medulla and Paraganglia

What is the adrenal medulla?
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Terms in this set (14)
inner portion of the adrenal gland
- "fight or flight"

located inside the adrenal cortex in the center of an adrenal gland

- associated with the sympathetic nervous system
BUT also,
- consists of sympathetic paraganglia made of chromaffin cells

- sympathetic paraganglion whose cells secrete neurotransmitters (epinephrine and norepinephrine into capillaries instead of synapses)

- produces "stress hormones," including adrenaline via neuronal stimulation

- affects available energy, heart rate, and metabolism

- secretes catecholamines including epinephrine, norepinephrine, and dopamine
1. Stimuli travel through the sympathetic nervous system by means of preganglionic nerve fibers that emerge from the thoracic spinal cord

2. Electrical impulses carried by the sympathetic nervous system are converted to a chemical response in the adrenal gland

3. Chromaffin cells contained in the adrenal medulla act as postganglionic nerve fibers that release this chemical response (catecholamines such as epinephrine & norepinephrine) into the blood as circulating messenger

4. The sympathoadrenal system can activate and discharge chemical messengers to activate an organism's "fight or flight" response

5. This "sympathoadrenal discharge" causes an increase in heart rate, cardiac output, blood pressure, and glucose levels

- adrenal medulla is in effect a sympathetic paraganglion
- cells secrete hormones when stimulated by the
preganglionic nerve fibers
What are the two main groups of adrenoreceptors?α and β Norepinephrine = α receptor agonist Epinephrine = mixed α & β agonist Dopamine = D receptor agonist (precursor of NE) alpha: > α1 (a Gq coupled receptor) > α2 (a Gi coupled receptor) beta: > β1, β2 and β3 > All 3 are coupled to Gs proteins - Gi (α2) and Gs (β) are linked to adenylyl cyclase - Gq (α1) linked to phospholipase C - Agonist binding thus causes a rise in the intracellular concentration of the second messenger (Gi inhibits the production of cAMP) - Downstream effectors of cAMP include cAMP-dependent protein kinase (PKA), which mediates some of the intracellular events following hormone bindingWhat are some actions of catecholamines?> Metabolism - o2 consumption; co2 production > Carbohydrate Metabolism - gluconeogenesis - glycogenolysis - insulin inhibition - glucagon (increases blood sugar) secretion - ACTH secretion > Lipid Metabolism - lipolysis (fat breakdown) > Heart (myocardium) - increase force and rate of contraction > CNS - alertness - anxiety - tremors > Blood vessel - increase blood pressure (vasoconstriction) - RBC supply - kidney (renin) > Respiration - Bronchial dilation (used for asthma) > Skin - arrector pili (hair on end) > Eyes - pupillary dilation > Relaxation - GI muscles - Salivary glandsWhat is pheochromocytoma?rare tumors that secrete catecholamines and affect the sympathoadrenal system - typically found inside the adrenal medulla - constantly in fight or flight? Symptoms: - headaches - sweating - palpitations - hypertension - hypoglycemia - anxiety, weight loss, fever, nausea, and cardiovascular complicationsHow is Pheochromocytoma treated?through blocking the effects of the secreted catecholamines - surgical removal of tumor - ideally, removal of the tumor is the preferred treatment for the best prognosis - If left untreated, it may lead to fatal consequences especially to the cardiovascular system