Chapter 11 (Part 4) Flashcards
why doesn’t the parasympathetic nervous system use the sympathetic chain?
presynaptic synapses directly with the target organs. you want a more 1-on-1 type of regulation, or one on few. it goes slower, because time is less critical.
why is it possible that the vascular and sweat gland systems can function using only the SNS? in other words, why isn’t the PNS needed to work against the SNS? (2)
vascular: always contracted, always needs pressure. you don’t need an opposing force because the heart is always contracted.
sweat: always making sweat, which is fine as long as the sweat gland isn’t making sweat too fast. the long part of the sweat gland can reabsorb it.
how is it possible that epinephrine (adrenaline can have the opposite effect on smooth muscle of the lung bronchial airways and blood vessels in muscle verses the smooth muscle of the intestinal vasculature?
depends on receptor. specificity is in the receptor. (40:00)
the lung bronchial airways contain more b receptors which cause bronchiole dilation when epinephrine is bound. the intestinal vasculature contains more a receptors which causes vasoconstriction when epinepherine is bound.
how do neuron to gland and neuron to muscle synapses differ from neuron to neuron synapses and why?
N-G + N-M: we want to hit an area, not just one cell. if we stimulate others simultaneously through gap junctions
N-N: presynaptic to specific neuron. contact point, 1 cell, it’s specific.
what is a muscle fiber?
multiple muscle cells fuse to form a muscle fiber. muscle fibers can’t replicate, regenerate, or divide.
a motor neuron can innervate multiple muscle fibers but muscle fibers are only innervated by one motor neuron. why?
troops and officers. you want everybody following the same orders.
in other words, you don’t want to send conflicting signals to the same fiber.
what is a skeletal muscle motor unit composed of?
motor neuron and all muscle fibers that it innervates
motor neurons release the NT ____ onto a motor end plate and this may/always depolarizes the muscle fiber to contract
acetylcholine
always
what is the function of acetylcholinesterase at the neuromuscular juncion?
brea down excess Ach to acetate and choline
how does black widow spider venom affect a motor neuromuscular junction?
trigger massive release of acetylcholine from terminal bouton
how does botulism toxin affect a motor neuromuscular junction?
destroys terminal boutons
what is curarae?
reversible competitive inhibitor of nicotinic cholinergic receptors
how does organophosphates in pesticides affect a motor neuromuscular junction? (2)
inhibit/interfere with acetylcholinesterase and prevent inactivation of acetylcholine
how do myasthenia gravis autoantibodies affect a motor neuromuscular junction?
autoantibodies bind to nicotinic cholinergic receptors on the motor end plate
