Adrenal Medulla and Catecholamines

Question 1

What are some things that will trigger the hypothalamus to stimulate sympathetic neurons to act on the adrenal medulla to release epinephrine and norepinephrine?

Answer 1

Stress

Physical activity

Low blood glucose

Question 2

The adrenal medulla is like a […]

Answer 2

Sympathetic ganglion

Question 3

Preganglionic sympathetic nerves synapse on the adrenal medulla and release […] which binds to […] receptors on chromaffin cells casuing them to secrete […] or […] into the blood stream.

Answer 3

Ach

Nicotinic

Epi

NEpi

Question 4

True/false: most of the chromaffin cells in the adrenal medulla secrete epinephrine.

Answer 4

True - 80% release Epi and 20% release NE

Question 5

What are the embryological origins of the adrenal medulla and sympathetic ganglia?

Answer 5

Both derived from neural crest cells. During development, some of these neural crest cells commit to becoming sympathoadrenal lineage cells. Due to many transcription factors, some become sympathetic chain ganglia, others become adrenal medulla cells.

Question 6

Discuss the short term and long term bodily responses to stress and how the adrenal gland is involved in these responses.

Answer 6

Question 7

All pre-ganglionic neurons of the autonomic NS release […] onto […] receptors on post-ganglionic neurons.

Answer 7

Ach

Nicotinic

Question 8

PSNS pre-ganglionic neuron releases […] onto […] receptor on post-ganglionic neuron. Post-ganglionic neuron releases […] onto […] receptor on target tissue.

Answer 8

Ach

Nicotinic

Ach

Muscarinic

Question 9

SNS pre-ganglionic neuron releases […] onto […] receptor on post-ganglionic neuron. Post-ganglionic neuron releases […] onto […] receptor on target tissue. This is true for all tissues except […] and […] which instead have post-ganglionic neurons that release […] onto […] receptor.

Answer 9

Ach

Nicotinic

NE

Alpha and beta adrenergic

Sweat glands –> Ach onto muscarinic

Renal vascular smooth muscle –> dopamine onto D1 receptors

Question 10

Review the synthesis of NE.

Answer 10

Tyrosine is brought into neuron terminal –> converted to LDOPA by tyrosine hydroxylase –> converted to dopamine –> dopamine loaded into vesicles by VMAT –> inside vesicle it is converted to NE –> NE released

• Bind to a1, b1, or b2 receptors on target tissue
• Bind to a2 autoreceptor that binds and inhibits NE synthesis
• Be reuptaken into neuron by NE transporter and oxidized by MAO or put back into vesicles

Question 11

Describe the synthesis of Epi in chromaffin cells of the adrenal medulla.

Answer 11

Tyrosine –> LDOPA – (tyrosine hydroxylase) –> Dopamine –> VMAT moves dopamine from cytosol into chromaffin granule –> DA – (dopamine beta hydroxylase) –> NE

• In chromaffin cells that make NE, the NE is put into a storage complex for storage until it needs to be released
• In chromaffin cells that make Epi, the NE is pumped back out into cytosol via VMAT where NE – (PMNT) –> Epi and Epi is pumped back into graunle via VMAT again and then put into storage complex

Question 12

What are some of the ways that glucocorticoids and catacholamines work together to generate common effects?

Answer 12

Both mobilize fuel stores during stress

Both increase glycogenolysis, gluconeogenesis and lipolysis

Question 13

Complete the table.

Answer 13

Question 14

Alpha 1 and beta 2 receptors bind […] with greater potency.

Alpha 2 receptors bind […] with greater potency

Answer 14

Epi

NE

Question 15

Binding of Epi or NE to beta 1 receptor has what effect on heart?

Answer 15

Increased force and rate of contraction

Question 16

Binding of NE and Epi to alpha 1 receptors on vascular smooth muscle causes […]

Answer 16

Vasoconstriction

Question 17

Binding of Epi to Beta receptors in skeletal muscle and liver causes […]

Question 18

If the sympathetic NS releases NE directly onto target tissues that need to be stimulated, why do we need an adrenal medulla to put NE and Epi into bloodstream?

Answer 18

Epi helps the SNS signaling function more efficiently and is helpful for reduction of orthostatic hypotension

Question 19

• True/false: the adrenal medulla responds by secreting equal amounts of Epi and NE in response to challenges to homeostasis.
• True/false: the sympathetic and adrenal medulla response to the same stimulus are not always equivalent in magnitude.

Answer 19

• False
• True

Question 20

• Epi and NE are metabolized by […] and […] enzymes in the […], […], and […].
• The breakdown product of NE is […] and the breakdown product of Epi is […].
• These breakdown products are converted to […] which is excreted by the […] and […].

Answer 20

• MAO; COMT; Liver, kidney, adrenal medulla
• Normetanephrine; metanephrine
• VMA; liver and kidney

Question 21

Assays to check for circulating levels of NE and Epi tend to actually measure what?

Answer 21

Levels of their first breakdown product –> Normetanephrine and metanephrine

Question 22

True/false: chromaffin cells only secrete Epi and NE.

Answer 22

False

Question 23

How can the immune system affect the adrenal medulla?

Answer 23

Cytokines can cause chromaffin cells to release neuropeptides –> which then go to stimulate immune tissues

Question 24

What is pheochromocytoma?

Answer 24

Question 25

How can diabetes impact adrenal medulla?

Answer 25