Sympathetic

[nr6unhH]

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[FONT=맑은 고딕]Sympathetic: norepinephrine .
[FONT=맑은 고딕]“flight or fight”:
increase heart rate, raises blood glucose, raises blood pressure, dilates the pupils, opens up the trachea and bronchi, and shunts blood away from the GI track to skeletal muscles, brain, and heart (muscular vasodilation).
[FONT=맑은 고딕]Flushing and sweating, constipation (bc of inhibited GI peristalsis), increased respiratory rate.


this is what i had down for result of sympathetic system. from ek bio 1001 book

however, pg. 107 from just regular ek bio book, it says "epinephrine and norepinephrine are vasoconstrictors (they constrict blood vessels) of most ineternal organs and skin, but are vasodilators of skeletal muscle (they increase blood flow).

can someone elaborate on general concept of vasodilation/vasoconstrictions and why certain parts and what not

thanks

 

[GRod18]

the whole concept behind this is that Epi and nor-Epi could vasocontrict the none vital organs inorder to shunt more blood to muscles that are important in the so called fight or flight scenarios ie increase cardiac output by vasocontricting the veins or vasocontricting arteries in the skin so more will be shunted to the skeletal muscles. They accomplish this by binding to various receptors. you need to remember that it is the type of receptor that governs what effect the hormones have on the organs, not the type of hormone. There are alpha and beta receptors that they can bind to, but this is probabaly beyond the scope of the MCAT and will be explained in the passage.

http://en.wikipedia.org/wiki/Adrenergic_receptor I used this while studying for my Human physiology class, we had to memorize some of those receptors which is not required for the MCAT.

 

[da8s0859q]

the whole concept behind this is that Epi and nor-Epi could vasocontrict the none vital organs inorder to shunt more blood to muscles that are important in the so called fight or flight scenarios ie increase cardiac output by vasocontricting the veins or vasocontricting arteries in the skin so more will be shunted to the skeletal muscles. They accomplish this by binding to various receptors. you need to remember that it is the type of receptor that governs what effect the hormones have on the organs, not the type of hormone. There are alpha and beta receptors that they can bind to, but this is probabaly beyond the scope of the MCAT and will be explained in the passage.

http://en.wikipedia.org/wiki/Adrenergic_receptor I used this while studying for my Human physiology class, we had to memorize some of those receptors which is not required for the MCAT.

This, basically, but don't get caught up in the receptor thing for now.

OP, epi and NE are found in, among other times, fight/flight scenarios (epinephrine = adrenaline, remember?). If your body -- your sympathetic nervous system -- wants you to get your ass in gear because there's a big tiger coming to eat you, it's going to want to do a couple of things, right then and there:

1. Shunt blood away from your intestines and other non-vital organs that aren't immediately needed to make that blood available elsewhere (that bacon cheeseburger, while delicious, can wait to be digested, but your legs are needed right now to run);

2. Shunt blood to your skeletal muscle and other places you mentioned to provide for suddenly increased metabolic demand. Skeletal muscle, the brain, and the heart all have a big role to play during an adrenaline dump, so that's why they take priority when it comes to blood circulation in situations like this.

Vasodilation / vasoconstriction are just changes in the diameter of the "tube" carrying the blood, according to the target organ's need. Bigger tube diameter equals bigger flow capacity -- hence vasodilation in muscle beds, and vasoconstriction to the GI tract.