ANS 1 Flashcards

Question

When SNS is activated, describe changes in Muscarinic receptors

Answer 1

Pheochromocytoma – neoplasms (tumors) of the adrenal medulla that secrete excessive amounts of norepinephrine (most common), epinephrine, or both resulting in sustained hypertension, and other effects (e.g., cold hands and feet, sweating and feeling hot) . Rare, observed in age range 40's - 50's, & in both men & women. Treatment = excise tumor. To treat the symptoms, give α1 and β1-adrenergic antagonists.

Answer 2

Symptoms due to SNS problem = PAM is Horny. On the affected side of the face, there is ptosis (drooping eyelid), anhydrosis (dryness of face), miosis (partial constriction of pupil). 1st order lesion - brainstem lesions interrupting descending tracts e.g. stroke 2nd order lesion - preganglionic sympathetic cell bodies or fibers supplying eye synapse in superior cervical ganglion 3rd order lesion – postganglionic sympathetic cell bodies or fibers

Answer 3

inositol 1,4,5 -triphosphate (IP3) and causing a subsequent increase in intracellular [Ca2+].

Answer 4

adenylate cyclase and increasing the production of cyclic adenosine monophosphate (cAMP).

Answer 5

cholinergic

Answer 6

nicotinic cholenergic Then epinephrine and, to a lesser extent, norepinephrine are released into the circulation.

Answer 7

β2 receptors on vascular smooth muscle produce vasodilation. α receptors on vascular smooth muscle produce vasoconstriction. Because β2 receptors are more sensitive to epinephrine than are α receptors, low doses of epinephrine produce vasodilation, and high doses produce vasoconstriction.

Answer 8

The best answer for local control of blood flow is the cerebral circuit. Most other circulations listed all are under the significant sympathetic adrenergic control.

Answer 9

local vasodilation in skeletal muscle--The vasodilation and increased blood flow to exercising muscle is mainly via the local production of vasodilatory metabolites. Circulating epinephrine will stimulate β2 receptors to contribute to the vasodilation. There is only a small increase in stroke volume during exercise, and cardiac parasympathetic stimulation would tend to decrease cardiac output and flow to the periphery.

Answer 10

local metabolites on skeletal muscle arterioles--During exercise, local metabolites accumulate in the exercising muscle and cause local vasodilation and decreased arteriolar resistance of the skeletal muscle. Because muscle mass is large, it contributes a large fraction of the total peripheral resistance (TPR). Therefore, the skeletal muscle vasodilation results in an overall decrease in TPR, even though there is sympathetic vasoconstriction in other vascular beds.

Answer 11

A negative inotropic effect is one that decreases myocardial contractility. Contractility is the ability to develop tension at a fixed muscle length. Factors that decrease contractility are those that decrease the intracellular [Ca2+]. Increasing heart rate increases intracellular [Ca2+] because more Ca2+ ions enter the cell during the plateau of each action potential. Sympathetic stimulation and norepinephrine increase intracellular [Ca2+] by increasing entry during the plateau and increasing the storage of Ca2+ by the sarcoplasmic reticulum (SR) [for later release]. Cardiac glycosides increase intracellular [Ca2+] by inhibiting the Na+-K+ pump, thereby inhibiting Na+-Ca2+ exchange (a mechanism that pumps Ca2+ out of the cell). Acetylcholine (ACh) has a negative inotropic effect on the atria.

Answer 12

Increased sympathetic stimulation of the heart increases heart rate, atrial contractility, and ventricular contractility and also increases norepinephrine release at the ventricular sympathetic nerve endings. It does not release acetylcholine. It does cause an increased sodium permeability of the A-V node, which increases the rate of upward drift of the membrane potential to the threshold level for self-excitation, thus increasing heart rate.

Answer 13

The cutaneous and renal vessels have a more pronounced vasoconstrictor response to the stimulation of adrenergic neurons than do the vessels of skeletal muscle and the lungs. The cerebral and coronary circulatory systems are among the least sensitive systems in the body to the constrictor actions of norepinephrine.

Answer 14

decreases contractility of the atria (negative inotropic effect) force of contraction of the ventricles (positive inotropic effect)

Answer 15

decreases heart rate (negative chronotropic effect) increases both the heart rate (positive chronotropic effect)

Answer 16

In contrast to the large-diameter/fast conducting myelinated motor neurons innervating skeletal muscle: preganglionic axons are small-diameter/slower conducting myelinated fibers. Postganglionic axons are primarily small diameter/slower conducting unmyelinated fibers.

Answer 17

Increased sweating and piloerection via activation of muscarinic and alpha-1 adrenergic receptors, respectively.