ANS- INTRO INFO Flashcards
NEUROTRANSMISSION & RECEPTORS
CNS vs. PNS
- includes what structures/nervous system divisions
central vs peripheral
CNS- brain, spinal cord, integrates all body activities
PNS- Somatic and Autonomic nervous system
- ANS further divides–> Parasymp and Symp
Somatic Nervous system
- what actions
- neurons and where they go
activates skeletal muscle contraction
- motor and sensory neurons
- sensory/afferent go TO the CNS
- motor/efferent go FROM CNS to skeletal muscle
VOLUNTARY
Autonomic nervous sytem
- divisions
- actions
- neurons and where they go
PNS and SNS
- regulates activity of smooth muscle, exocrine glands, cardiac tissue, metabolic activities
- sensory FROM smooth muscle and cardiac muscle TO the CNS
- motor TO glands, smooth and cardiac muscle FROM CNS
INVOLUNTARY
Enteric nervous system (ENS)
- innervation from where
- actions
autonomic nerves in gut wall
- SNS and PSNS innervation
- regulates GI motility and secretions
- responds to neurotransmitters (peptides and nitric oxide)
ANS neurotransmission
- preganglionic and post ganglionic neurons originate/go where
preganglionic neuron- cell body in CNS, axon extends out
postganglionic- innervates effector tissue outside the CNS
- what is a ganglion
- synapses are where
ganglion- small mass of nerve tissue cotnaining cell bodies of neurons
synpase- space between pre and post OR post and effector where NT is released
SNS and PSNS primary neurotransmitters
SNS: norepinephrine (NE)
aka noradrenaline (NA)
PSNS: acetylcholine (ACh)
where is ACh released vs. NE
ACh- released at all autonomic ganglia (PSNS + SNS), at PNS neuroeffector junction, somatic neuromuscular junction, and some SNS nej
NE- released at most SNS nej
where is epinephrine vs. dopamine released
Epi- released from adrenal medulla in response to SNS activation
Dopamine (DA)- released at several peripheral SNS fibers (important in CNS)
ANS neurotransmission- sympathetic innervation of adrenal medulla
preganglionic neuron releases ACh–> ACh (the ganglionic transmitter) binds to nicotinic receptor on adrenal medullla—> releases epi in blood (neuroeffector transmitter) —–> epi binds to adrenergic receptor on the effector organ and causes effect accordingly
ANS neurotransmission- SNS
symp nervous system releases ACh—> ACh binds to nicotinic receptor in ganglia (this a postganglionic neuron)—> releases NE/norepi (neuroeffector transmitter)—> NE binds to adrenergic receptor on effector organ
short preganglionic nerve–> releases ACh binds to nicotinic receptor which stim post ganglionic nerve—> releases NE on adrenergic receptor on effector organ
ANS neurotransmission- PSNS
parasymp releases ACh (pregang neuron)–> ACh binds to nicotinic receptor (post gang neuron) and then releases more ACh—> which binds to muscarinic receptor on effector organ
long pre ganglionic nerve–> releases ACh and synapse with short post ganglionic nerve–> releases more ACh which binds to muscarinic receptor on effector organ
neurotransmission at cholinergic neurons (ACh)
6 steps
1- choline comes in with Na+ and choline acetyltransferase synthesizes ACh (from choline and AcCoA)
2- uptake ACh into storage vesicles
3- release ACh
4- ACh bindto post synaptic receptor for intracellular response, AND presynpatic rceptor for negative feedback (controls amt of release)
5- degrade ACh by aceytlcholinesterase in synaptic cleft, acetate waste product
6- recycle choline back in
what are things that can block or cause further release chlonergic neurotransmission
- release of ACh into synaptic cleft can be BLOCKED by botox (botulinum toxin)
- spider venom can inc RELEASE of ACh
- choline reuptake can be BLOCKED by hemicholinium
- cholinergic agonists or antagonists
neurotransmission at adrenergic neurons
6 steps
1- tyrosine and Na+ in and synthesized by rate limiting step
2- made into DOPA–into dopamine which enters vesicle–then converted into NE in vesicle
3- influx calcium triggers exocytosis of vesicle, releases NE into synapse
4- NE binds to post synaptic receptor and pre for neg feedback
5- NE either taken back into neuron (reuptake) or…
6- NE metabolized/degraded by COMT and oxidized by MAO
what can block or inc release of NE in adrenergic neurotransmission
- transport of dopamine into vesicle can be BLOCKED by reserpine
- release of NE can be blocked by guanethidine
- reuptake is BLOCKED by SNRIs, cocaine, and impiramine (TCA)
- MAO inhibitors
- adrenergic agonists or antagonists
other neurotransmitters
ANS- non adrenergic noncholinergic neurons (NANC)
- found in enteric NS of gi tract, genitourinary tract, airways, and some BVs
- peptides, ATP, GABA, substance P, nitric oxide, serotonin
PSNS general effects
SPECIFIC responses
- rest & digest
- miosis (constrict)
- INC gi motility/salivation
- INC urination/defecation
- DEC HR
- bronchoCONSTRICT
- erection (point/para)
SNS general effects
DIFFUSE responses
- fight or flight
- mydriasis (dilate)
- DEC gi motility/salivation
- DEC urination/defecation
- INC HR
- bronchodilate
- ejaculate (shoot/symp)
Cholinergic receptors- Muscarinic
- located at PSNS nej, SNS nej for sweat glands, CNS, and autonomic ganglia
- activated by ACh and muscarine
post gang neurotrans. activates muscarinic recep. on effector organs
Muscarinic receptors- effects
- smooth muscle contraction (except sphincter)
- gland secretion
- dec HR
- bronchoconstrict
- periph vasodilation
- miosis
SLUDGE: salivation, lacrimation, urination, defecation, gi motility, ereciton
Cholinergic receptors- nicotinic
- activated by ACh and nicotine
- located on autonomic ganglia, when activates causes neurotransmission
- some located at neuromusc junction an when activated mediates muscle contraction
at synapse between post and pregang neuron in SNS, PSNS, and ON the adrenal medulla (pregang and effector organ synapse)
adrenergic receptors- a1
location and effects
(NE and Epi)
- vasoconstrict vasc smooth muscle
- constrict BV (hypertension)
- mydriasis
- inc basal metabolic rate
- located at SNS nej effector
alpha constrict, beta dilate (ABCD)
also inc closure bladder sphincter/hold pee
adrenergic receptors- a2
location and effects
- inhibit NE release at pre synaptic post gang neuron (neg feedback)
- inhibit ACh release
- located on some postsynaptic tissue and blood platelets
also inhibit insulin release ?
adrenergic receptors- b1
location and effects
- INC HR and contractility (tachycardia)
- INC lipolysis
- INC renin release
located on SNS effector
b1 is heart
adrenergic receptors- b2
location and effects
- vasodilation
- smooth muscle relaxation
- bronchodilate
- inc muscle and live glycogenolysis
- located on SNS effector
also relax uterine smooth muscle
drugs affecting autonomic transmission can….
can exert effects on any step of neurotransmission depending on classification
PSNS and SNS agonist (direct or indirect)
PSNS and SNS antagonist (direct or indirect)
Direct vs. indirect agonists
direct- activate post synaptic receptors
indirect- stim release of NT, inhibit reuptake of NT, inhibit metabolism of NT
direct vs. indirect antagonists
direct- block postsynaptic receptors
indirect- inhbit synth of NT, prevent storage of vesicular NT, inhbit release of NT
