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Medullary chromaffin cells synthesize catecholamines epinephrine (80%) and norepinephrine (20%)
fight or flight” mechanisms
Effects of catecholamines:
Vasoconstriction
Increased heart rate
Increased blood glucose levels
Blood diverted to brain, heart, and skeletal muscle
Epinephrine -
is more a stimulator of metabolic activities
Example: bronchial dilation, and blood flow to skeletal muscles and heart
Norepinephrine -
has more of an influence on peripheral vasoconstriction and blood pressure
Responses to stressors are brief, unlike adrenal cortical hormones
Hyposecretion -
Epinephrine and norepinephrine are not essential to life; therefore there are no problems associated with hyposecretion
Hypersecretion -
Leads to symptoms of uncontrolled sympathetic nervous system, such as:
Hyperglycemia, increased metabolic rate, rapid heartbeat, palpitations, hypertension, intense nervousness, and sweating
Can be due to pheochromocytoma, tumor of medullary chromaffin cells