Lecture 71 Flashcards
Intro to the Autonomic and Somatic Nervous Systems
organization of the nervous system
- CNS: brain and spinal cord
- PNS: neurons outside brian and spinal cord; enter CNS (afferent) or leave CNS (efferent)
- efferent subdivided into: somatic neurons (voluntary functions) and autonomic neurons (functions outside of conscious control)
pg 1842
autonomic vs somatic efferent neurons
Autonomic
- have ganglia (NT → acetylcholine, receptor → Nn (neuronal))
- post-ganglionic neurotransmitter and receptor varies depending on sympathetic vs parasympathetic
Somatic
- NO ganglia
- NT: acetylcholine
- Receptor: Nm (muscle)
pg 1844
structure of the efferent neuron
- autonomic: preganglionic and postganglionic neuron
- somatic: 1 neuron from CNS to muscle
pg 1845
sympathetic vs parasympathetic neuron
Sympathetic
- short pre-ganglionic neuron (branched), long postganglionic neuron
- 1st NT → acetylcholine, 1st receptor → Nn
- 2nd NT → norepinphrine/noradrenaline, 2nd receptor → α/β adrenergic receptor
- ganglion in sympathetic chain, close to spinal cord
Parasympathetic
- long pre-ganglionic neuron, short post-ganglionic neuron
- 1st NT → acetylcholine, 1st receptor → Nn
- 2nd NT → acetylcholine, 2nd receptor → muscarinic receptor
- ganglion very close to or within the organ
pg 1847
sympathetic innervation to adrenal medulla
- adrenal medulla thought of as a modified ganglion
- has nicotinic receptor for acetylcholine from preganglionic neuron
- releases epinephrine/adrenaline that travels in the blood to go where needed (and act on adrenergic receptors)
pg 1849
sympathetic nervous system
- fight, fright or flight response
- increases all heart functions
- vasoconstricts BVs in skin and splanchnic, vasodilates skeletal BVs
- decreases GI motility and secretions, contracts sphincters
- bronchodilation, decreased respiratory secretions
- bladder relaxation, urinary sphincter contracts
- pupil dilation, accommodation for far vision
pg 1860
parasympathetic nervous system
- rest and digest response
- opposite functions as sympathetic nervous system
pg 1860
dual innervation
- received by most organs
- relationship between two components of ANS is dynamic and continuously fine tuned to achieve homeostasis
pg 1864
neurotransmission at cholinergic neurons
- synthesis of acetylcholine
- uptake into storage vesicles
- release of neurotransmitter
- binding to the receptor
- degradation of acetylcholine
- recycling of choline
pg 1866
cholinergic receptors
- bind to acetylcholine → cholinergic receptors
- further classified into nicotinic and muscarinic
pg 1867
muscarinic recptors
- found in effector organs receiving parasympathetic innervation
- GPCRs
- M1 through M5
pg 1868
nicotinic receptors
- Nn found in ganglia and adrenal gland
- Nm found in skeletal muscle
- ion channel-linked receptors
pg 1868
distribution of muscarinic receptor subtypes
- M2 found in heart
- M3 in glands and smooth muscle
- Nm found in skeletal muscle neuromuscular junction
- Nn found in postganglionic cell body
pg 1869
examples of actions mediated by cholinergic (muscarinic) receptor stimulation
- rest and digest actions
- bronchoconstriction, lung secretion, increased GI motility, etc…
pg 1870
acetylcholinesterase (AChE)
responsible for termination of acetylcholine action at nerve terminals by breaking down acetylcholine (important drug target to elicit a parasympathetic response)
pg 1872
