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Autonomic Nervous System (ANS), Sympathetic Nervous System (SNS)…
Autonomic Nervous System (ANS)
Sympathetic Nervous System (SNS)
Preganglionic nerves originate from central spine (thus shorter)
Responses are slower and more diffuse (ie full body - fight or flight)
Parasympathetic Nervous System (PSNS)
Preganglionic nerves originate from cranial and sacral parts of spine (thus longer)
Responses are rapid and more precise (ie specific organ)
Two types of Synapses in ANS
Cholinergic
release ACh.
Adrenergic
release E and NE
Two receptor types
Alpha (a)
stimulated primarily by NE, promote smooth muscle constriction.
Beta (b)
Two types, B1 and B2
B1
stimulation causes cardioacceleration, increased myocardial strength and lipolysis.
B2
stimulation causes vasodilation, intestinal relaxation, uterine relaxation, bronchodilation, glycogenolysis, bladder relaxation.
B2 agonists
are Black Cohosh and Guelder rose, thus uterine antispasmodics.
Inhibited by
beta blockers
. if non-specific (inhibits 1 and 2) there can be side effects such as bronchoconstriction
Effects of N and NE are determined by receptor types, if B-receptors then epinephrine will be a stimulant, if there are a and B receptors then effects will be less.
After binding with receptor site ACh degrades into
acetic acid and choline under influence of AChE
Choline pumped back into presynaptic neuron, recycled into ACh
Two receptor types
Nicotinic
located in brain, smooth muscle, heart, glands.
upregulation of autonomic functions
named as such because nicotine stimulates both sympathetic and parasympathetic postganglionic nerves.
Muscarinic
located in brain, sweat glands, blood vessels. Promotes parasympathetic responses
sweating, salivation, decreased heart rate, hypotension, peristalsis
. Also associated with learning, memory, posture, temp regulation. Called as such due to
*amanita muscaria mushroom
stimulates PNS responses.
All preganglionic nerves in SNS and PNS are Cholinergic
Postganglionic nerves in PNS are Cholinergic
Most postganglionic nerves in SNS are Adrenergic.