Autonomic Nervous System Flashcards
two divisions of motor division of PNS:
somatic
autonomic
somatic NS
- AP comes from lateral gray horn of SC & is carried by myelinated neuron
- excitatory response in skeletal muscle, never inhibitory
- at effector, NT released is acetylcholine, causes muscle to contract
autonomic NS
- AP comes from anterior gray horn of SC (cell body is in lateral horn or brainstem)
- 2 neuron system:
preganglionic neuron synapses w postganglionic neuron at autonomic ganglion - effectors are smooth muscle, cardiac muscle, glands
preganglionic neuron
- has origins in CNS
- myelinated
- releases acetylcholine at autonomic ganglion
postganglionic neuron
- extends from synapse at ganglion outside of CNS to the effector/ target tissue
- unmyelinated
- NT released is either acetylcholine or norepinephrine
divisions of the ANS
2 main:
- sympathetic
- parasympathetic
also enteric division
sympathetic division
aka thoracolumbar division - origins in lateral horn of SC from T1-L2, exit through ventral root - uses 2 types of ganglia: sympathetic trunk ganglia/chain ganglia prevertebral/collateral ganglia
sympathetic trunk ganglia/chain ganglia
chains of ganglia close to SC
form 2 chains on either side of SC
prevertebral ganglia/collateral ganglia
closer to effectors or target tissues
there are 4 routes of sympathetic axons; tell me about the 1st
- preganglionic leaves CNS w spinal nerve, synapse in chain ganglion, postganglionic nerve re-joins spinal nerve at anterior ramus
target: skin of neck, trunk limbs
there are 4 routes of sympathetic axons; tell me about the 2nd
- exit CNS w spinal nerve, synapse in chain ganglion, post ganglionic neuron called a sympathetic neuron and goes directly to target tissue
target: heart & lungs
there are 4 routes of sympathetic axons; tell me about the 3rd
- preganglionic neuron passes through chain ganglion w/o synapse and instead synapses in collateral ganglion
- after preganglionic nerve leaves sympathetic chain ganglion, it is called the splanchnic nerve
target: abdominopelvic organs
there are 4 routes of sympathetic axons; tell me about the 4th
- preganglionic neuron bypasses both chain ganglion and collateral ganglion ad synapses w cells of adrenal medulla. this stimulates them to release epinephrine and norepinephrine into the blood where they act as hormones
parasympathetic division
aka craniosarcal division
- cell bodies assoc w nuclei of cranial nerves III, VIII, IX, X and also lateral gray horn of SC S2-S4
terminal ganglia
where preganglionic axons synapse w postganglionic axons in the parasympathetic NS
pelvic splanchnic nerves
supply smooth muscle and gland control of colon, bladder and reproductive organs
cranial nerve III is responsible for
ciliary muscles, sphincter pupillae
cranial nerve VII is responsible for
glands for tears and nasal secretions
cranial nerve IX is responsible for
parotid salivary gland
cranial nerve X is responsible for
- has many branches
- heart, pulmonary, GI systems
NT secreted by sympathetic preganglionic and postganglionic neurons
pre: cholinergic
post: adrenergic
NT secreted by parasympathetic preganglionic and postganglionic neurons
pre: cholinergic
post: cholinergic
cholinergic receptors
- acetylcholine can be either excitatory or inhibitory, depending on which receptors them bind to
2 classes: nicotenic and muscarinic
nicotenic receptors
- excitatory only
- open Na+ channels
- located on cell bodies of postganglionic neurons in both sympathetic and parasympathetic
- also found on muscle cell plasma membranes at the neuromuscular junction
muscarinic receptors
- excitatory or inhibitory response
- found on effector cells that respond to acetylcholine from postganglionic neurons (smooth muscle, cardiac muscle, glands)
adrenergic receptors
- bind w epinephrine & norepinephrine
- found in most sympathetic NS effectors bc postganglionic symp neurons release norepinephrine
2 classes: Alpha receptors (A1, A2) and Beta receptors (B1, B2)
A1, B1 are for excitation
A2, B2 are for inhibition
diverse actions, dependant on receptor and tissue
baroreceptors
receptors in walls of large arteries that detect stretch and changes in BP
generalizations of the ANS
- both divisions produce stimulatory and inhibitory effects
- most organs receive dual innervation
- divisions usually have opposing effects
- produce cooperative effects (can stimulate several organs in a system to cooperate)
- general (symp bc of adrenal hormones) vs. local (parasymp) effects
- rest (parasymp: SLUDD) vs action (symp)
SLUDD
salivation lacrimation urination digestion defecation
enteric division of ANS (sort of)
has nervous plexuses located in walls of digestive tract that contain nerve cell bodies vs just axons
- there are 3 points of nervous input into the GI tract
3 points of nervous input into GI tract:
- digestive info goes to CNS
- ANS motor neurons connect CNS to digestive tract for control of smooth muscle, gland secretions
- Enteric neurons are controlled through autonomic reflexes
3 major types of enteric neurons
sensory
motor
interneurons
enteric sensory neurons
detect stretch and chemical composition of contents
enteric motor neurons
stimulate or inhibit smooth muscle and control gland secretions
enteric interneurons
connect sensory & motor neurons
- help create reflex loops to allow for rapid response to info that has been detected
