EX 2 Lecture 7: ANS Flashcards
What is the difference between a preganglionic and postganglionic neuron?
Preganglionic starts in CNS, only has Ach for its NT- releases Ach as neurotrasnmitter
Postganglionic cell body in autonomic ganglia, can use nictonic (Ach), muscarinic (Ach), or adrenergic (epi/norepi)
contains nicotinic receptor to which the Ach binds
neuron pathway
sympathetic start in CNS and have a short preganglionic neuron that synapses with postganglionic neurons nicotinic receptor the long post ganglionic nueron then goes to target where it will synapse at muscarinic receptor for sweat glands, releasing ACh and at adrenergic receptors releasing Epi or Norepi for all other autonomic functions
parasympathetic start in CNS and have a long preganglionic neuron that synapses with postganglionic neuron nicotinic receptor releasing Ach, post ganglionic neuron then travels to target and synapses at muscarinic receptor and releases Ach
somatic has one motor nerve that synapses at target muscle via nicotinic receptor releasing Ach
what is the PNS
nerves that extend from the spinal cord to the organs and extremities
autonomic and somatic
afferent neuron
incoming
internal and external environment TO THE CNS
efferent neuron
exit/outgoing
CNS to body
control and integration of visceral function necessary for life/ CO, blood flow distribution, digestion
what does the autonomic nervous system require
requires pre and post ganglionic interaction to influence target organ, unlike somatic system
describe myelination of autonomic nerves
lightly myelinated preganglionic axons
unmyelinated postganglionic axons
what does the somatic system require
only ONE neuron to influence target organ
afferent nerves from environment to CNS and efferent nerves from CNS to muscle
heavily myelinated axons
autonomic nervous system (motor neurons) are for….
involuntary movements
somatic nervous system neurons are for
voluntary movements
all preganglionic neurons (sympathetic and parasympathetic are)
cholinergic ( release ACh at nicotinic receptor)
all parasympathetic postganglionic neurons are
cholinergic (release ACh at muscarinic receptor)
all sympathetic postganglionic neurons are____ except ____ which are ______
noradrengeric, sweat glands, cholinergic
role of ANS
maintain homeostasis
“autonomic takes care of automatic function”
- cardiovascular system (HR, CO, tone vasculature or constricting when dehydrated)
- smooth muscle for GI tract
- glandular function (adrenal, sweat,bladder)
What is the function of the sympathetic nervous system and its other name?
Catabolic, fight or flight response
Thoracolumbar system
What is the function of the parasympathetic nervous system and its other name?
Anabolic, rest and digest
Craniosacral system
What is the key difference in response for the sympathetic and parasympathetic? Why does it occur?
Sympathetic is generally more widespread
Parasympathetic is localized
Sympathetic fibers are located farther from their target organ lateral to the spinal column, while parasympathetic postganglionic neurons are right next to a target organ instead of along vertebral column
What is the primary NT secreted by postganglionic fibers of the sympathetic NS? What is the exception?
Norepi (which interacts with a variety of receptors)
The exception is the adrenal medulla, which is 80% epi & 20% norepi
What are the differences between epi and norepi?
Norepi is faster acting but has lower response in regards to beta stimulation.
what does ACh interact with at the target organ in parasympathetics
muscarinic receptors
process of acetylcholin
- acetyl coA + choline synthesized by ChAT into Ach
- Ach transported from cytoplasm into vesicles by vessicle associated transporter VAT
- action potential arrives at terminal and activated volt. gated Ca++ channels
- influx of Ca++ triggers release of Ach from vesicle into nerve terminal (synaptic cleft influx)
- acetylcholinesterase in synaptic celft breaks up Ach to choline and acetate (inactive)
half life of Ach
fraction of a second
What breaks down Ach?
Acetylcholinesterase
What are the monoamines?
Catecholamines, such as dopamine, epinephrine, and norepinephrine
synthesis pathways of monoamines
all linked by common synthesis pathway
tyrosine-> dopa->DA-> NE-> Epi
What happens in the terminal pathway (release) of monoamine creation?
Formation and release of EPI and NE to take action in the ANS
How are NE effects stopped/removed?
Stopped mostly by reuptake of neuron it was secreted from.
Can also be inactivated by liver and brain enzymes.
what is COMT /what does it do
liver enzyme that metabolizes endogenous and exogenous EPI and NE
what is MOA/ what does it do
enzyme that degrades EPI and NE
What is the amino acid origin of dopamine?
Tyrosine
monoamine synthesis pathway
- synthesized from tyrosine to dopamine by tyrosine hydroxylase (TH)in nerve terminal
- dopamine transported from cytoplasm to vesicles by vesicular monoamine transporter (VMAT)
- dopamine covnerted to NE
- action potential arrives at terminal, influx CA++ from volt gate channels
- influx of Ca++ triggers release of monoamines
- action termination by reuptake, diffusion, degradation, feedback mechanism
Where do I find muscarinic and nicotinic receptors?
Muscarinic(M1,2,3,4,5): GI tract, myocardium, blood vessels, exocrine glands, cerebral vasculature
Nicotinic(Nn, Nm): Skeletal muscle, adrenal medulla
norepinephrine receptors
alpha (a1,a2)
beta (b1,b2,b3)
where are a1 and a2 receptors in the body
a1- smooth muscle (vasculature-BP)
a2- platelets, lipocytes, smooth muscle
where are b1, b2, b3 receptors in the body
b1- heart
b2-lungs, skeletal vasculature (vasculature going to muscles)
b3- adipose tissue
receptors for dopamine and where they are located in the body
D1- brain, renal vascular bed
D2- brian, smooth muscle
D3- brain
D4- brain, cardiovascular system
What are the effects of a cholinergic agonist?
Eye: Miosis (pupil contraction)
Heart: Bradycardia
Respiratory: bronchial constriction + increased secretions
GI: increased motility
GU: relaxation of sphincters and bladder wall contraction
Glands: increased secretions