ANS review Flashcards
What are the two major subdivisions of the autonomic nervous system?
Parasympathetic nervous system and the sympathetic nervous system
Which ANS subdivision is known for rest and digest?
parasympathetic NS
What are the effects of the parasympathetic NS?
- increase in salivation - increase digestion- slows heart rate - decreases blood pressure- decrease respiration - empties the bladder and rectum
Which subdivision of the ANS is known for “fight or flight”?
sympathetic NS
What are the effects if the sympathetic NS?
- increase HR - Increase BP- stimulates secretion of epinephrine - increases blood flow to muscles - causes bronchioles to dilates and pupils to dilate
preganglionic fibers of the PSNS exit from the ________ and _______ nerves
cranial and sacral
Preganlionic fibers of the PSNS are _______ and ________ in ganglia
long and synapse
Post ganglionic fibers of the PSNS are ________ and synapse with ___________
short and effector organ
what is the primary function of the PSNS?
fine tune and exert specific organ and homeostatic control (Rest and digest)
Preganglionic fibers of the SNS exit from the _______ and ________ area
thoracic and lumbar spinal
preganglionic fibers of SNS are _______ and _______ at a ganglia
Short and synapse at a ganglia
The post ganglionic fibers of SNS are _______ and synapse with ________
long synapse with effector organ
The the ganglia for PSNS where are they located?
very close or sometimes in the effector organ
Post-ganglionic neurons of SNS can branch many times meaning they can have a ____________
diffuse response
Functions of the SNS are?
The four F’s: 1. Fight–physical stress or injury 2. Flight–exercise or your fleeing from something 3. Fright–mental stress 4. sex
What do most effector organs work as for the two systems?
they work as functional antagonists. The net effect reflects integrated influences of both systems
Some effector organs are under pre-dominant control of only one of the systems for PSNS its what?
Glands within the GI tract
Some effector organs are under pre-dominant control of only one of the systems, for SNS its what organs?
sweat glands adrenal medulla most blood vessels
somatic nervous system
the division of the peripheral nervous system that controls the body’s skeletal muscles
A somatic motor neuron is _______ _______ that releases what at the muscle?
one neuron that releases acetylcholine
What receptor do skeletal muscles have for acetylcholine?
nicotinic receptors (Nm)
for PSNS, The sacral neuron release ACh acts that nicotinic receptor (Nn)_______ the post ganglionic neuron
Activates
In PSNS, the post ganglionic neuron when activated release ACh to where?
Muscarinic receptors (M)
Nicotinic receptors are located where?
skeletal muscle, ganglia of PSNS and SNS
Alpha and Beta receptors are located where?
effector organs
What is the effect of activation of SNS on the HR?
increase
What is the effect of activation of SNS on heart contractile force?
increase
What is the effect of activation of the SNS on blood sugar?
increase
What is the effects of the activation of the SNS on bronchiole size?
increase
What is the effect of the activation of the SNS on gastrointestinal activity?
decrease
What is the effect of the activation of the SNS on the pupil size?
increase
What is the effect of the activation of the SNS on the secretion of sweat glands?
increase
if SNS is activated, which organs would vasodilation occur?
skeletal muscles
if SNS is activated, which organs would vasoconstriction occur?
Visceral organs such as GI tract
For each of the following scenarios, describe what system is involved. Challenge yourself and cite which receptor and neurotransmitter is involved at the end organ: A sudden and frightening sight causes a person to describe their reaction as their heart is about to leap out of their chest.
activation of the SNS causes release of Epi and NE from the adrenal gland and SNS nerve endings. Epi and NE act on B1 receptors to increase heart rate and force of contraction
A person’s skin feels cold and clammy.
skin is cold because of less blood flow == vasoconstriction -alpha receptors and NE (SNS)
A person has diarrhea from eating spoiled food.
activation of the PSNS causes increased GI activity–muscarinic receptors and ACh
A drug causes your eyes to dilate. Note, there are two ways this can happen.
anticholinergic–blocking ACh/ muscarinic at the iris OR alpha agonist activating the alpha receptor in the iris
A person took a drug with a side effect that blocks the ability to sweat and then goes to a hot yoga class. How and where is the drug acting to produce this effect? How will the person’s skin appear? Warm or cold?
an anticholinergic because the sweat glands, although on SNS side, the NT is Ach and receptor is muscarinic at gland/organ end. Warm and very dry. warm because skin is vasodilating to get rid of heat
what do most visceral organs have?
dual innervation between both SNS and PSNS
what does dynamic anatognism allow for?
precise control of visceral activity
SNS plays the major role of controlling blood pressure even at rest this is because of what?
because blood vessels are almost entirely innervated by sympathetic neurons with little PSNS neuron innervation
What is vascular tone?
the amount of constriction of a blood vessel
PSNS does innervate the heart, what does this effect?
it has significant effects on heart rate and contractility.
What are baroreceptors?
stretch receptors located in the carotid arteries and aortic arch
what NS does the baroreceptor reflex use to maintain blood pressure within normal limits?
SNS and PSNS
Cholinergic nerve fibers synthesize and release what as a neurotransmitter?
acetylcholine
All preganglionic nerve fibers are what?
cholinergic
All parasympathetic postganglionic nerve fibers are what?
cholinergic
What few sympathetic postganglionic nerve fibers are cholinergic?
sweat glands one
Adrenergic nerve fibers synthesize and release what as the neurotransmitter?
norepinephrine
No ____ are adrenergic
preganglionic nerve fibers
Almost all post ganglionic nerve fibers are adrenergic except what?
sweat glands are the exception
What is the first step in synaptic transmission?
synthesis of the NT (presynaptic)
What is the second step in synaptic transmission?
storage of the NT (presynaptic)
What is the third step in synaptic transmission?
release of the NT (presynaptic) -calcium dependent
What is the fourth step in the synaptic transmission?
binding of the NT to receptor (pre- or postsynaptic)
What is the fifth step in the synaptic transmission?
post-synaptic response
What is the sixth step in the synaptic transmission?
termination of the NT action
AcetlyCoA + choline –> ________
Ach
where does the reaction synthesizing Ach occur?
in the cytoplasm of the nerve terminal
what is ChAT?
the enzyme choline acetyletransferase is synthesized in the cell. body and transported down the axon to the nerve terminal. ChAT is found only in cholinergic neurons- no other place in the body. therefore a marker for cholinergic neurons
where does choline come from?
our diet
where is choline actively transported?
into the nerve terminal
what can block the active transport of choline?
hemicholinium
where is ACh actively transported and stored after synthesized?
vesicles
what can block the active transport of Ach into the vesicle?
Vesamicol
what causes an influx of Ca++ into the nerve terminal?
depolarization of the nerve terminal
what does Ca++ cause?
fusion of vesicles to the wall of the nerve terminal which then allows it to dump the contents into the synaptic cleft
What does the botulinum toxin block?
blocks the proteins that are needed to cause vesicles to fuse and then release Ach
what are the actions of Ach terminated by?
the enzyme acetylcholinesterase (AChE)
how does AChE work?
it acts very rapidly allowing Ach to act for only milliseconds
Choline is recycled through what?
it is recycled through reuptake
AChE inhibitors work where to block the destruction of Ach?
where choline is recycled through reuptake
what is the major NT for the SNS?
Norepinephrine (NE)
What are also NT’s for SNS in different areas of the body?
Dopamine and Epinephrine
If DA is the NT then the neuron does no have what?
Dopamine β- hydroxylase (DβH)
If epi if the NT then the neuron has what?
all of the enzymes plus Phenyelthanolamin-N-methyltransferase (PNMT)
how is tyrosine obtained?
from diet
What is the rate limiting step in the synthesis of adrenergics?
Tyrosine hydroxylase (TH)
what serves as a negative feedback on TH?
Catecholamines
Low levels or high firing rate increases expression of what?
TH
DA is actively transported into a vesicle and converted into what? what is in the vesicle?
NE; DβH is in the vesicle
what is the purpose of storage of NE in the vesicle?
provides a mechanism of release and protects NE from being metabolized by monoamine oxidase (MAO)
reserpine inhibits what?
vesicular monoamine transporter (VMAT)
What can reserpine cause?
depletion of NE store in sympathetic neurons
How is the release of NE similar to Ach?
Ca++ dependent mechanism that causes the vesicles to fuse to the membrane and release the NT
What is different about the release of NE from Ach?
The co-transmitters ATP and neuropeptide Y (NPY) are also released. ATP, NPY and NE interact with presynaptic receptors to decrease further release of NTs
what is the major mechanism of terminating effect of NE?
through reuptake
What effect does the reuptake inhibitor cocaine have on synaptic transmission?
the termination effects of NE would be blocked. So NE would keep having effects.
What are the Cholinergic receptors?
nicotinic and muscarinic
what are nicotinic receptors activated by?
nicotine, an alkaloid from tobacco
what is the structure of a nicotinic receptor? how many subunits?
pentameric structure consisting of 5 subunits.
the subunits of a nicotinic receptor come in four different forms named what? can they have subtypes? can they occur in a large number of combinations of subunits?
α, β, γ, δ; yes they can have subtypes; yes they can.
function of nicotinic receptors
ionotropic. activated when Na+ influx and depolarization
neuronal nicotinic receptors (Nn) are located where?
at the ganglia of SNS and PSNS (ganglionic receptors) and at the adrenal medulla
where are skeletal muscle nicotinic (Nm) receptors located?
on the skeletal muscle
what are muscarinic receptors activated by?
muscarine an alkaloid form of amanita muscaria
what is the structure of muscarinic receptors?
Metatropic and operate through G-proteins
what is the function of muscarinic receptors?
metabotropic = linked to secondary messengers
Where are muscarinic receptors located?
on the end organs of the PSNS (parasympathetic post-ganglionic receptors) Ex: cardiac muscle, smooth muscle, glands
M1 and M3 are coupled to what? What does this then activate?
coupled to Gq which activates phospholipase C leading to 2nd messengers
What leads to increased intracellular Ca++ levels?
IP3 and DAG
what are M3 majors effects?
increased secretions from glands, increased contractions of GI, Bladder and bronchial smooth muscle.
where are M1 receptors?
nerves in the CNS
What is M2 couple to? what does it inhibit?
Gi or Go which inhibits adenylate cyclase (cAMP formation). this inhibits voltage gated Ca++ channels and activates K+ channels
what are the major effects of M2?
to slow heart rate and contraction
what are the two classifications of adrenergic receptors?
alpha and beta
what is the major function of alpha 1 in the periphery?
to cause basal constriction (urogenital system and heart)
what are all alpha 1 receptors linked to?
Gq proteins and couple to enzymes phospholipase C and A to produce second messengers IP3, DAG and arachidonate.
is Alpha 1 pre or post-synaptic?
post-synaptic
is alpha 2 pre or post synaptic?
primarily pre-synaptic
what is the major function of alpha 2 in the periphery?
activation causes negative feedback to further decrease NE release
What are all alpha 2 receptors linked to?
Gi proteins and coupled to adenylate cyclase to inhibit the second messenger cAMP
all β receptors are linked to what?
Gs proteins which are coupled to adenylate cyclase to produce the second messenger cAMP
what is the major function of β1?
to act in the heart to increase heart rate and force of contraction
what is the major function of β2?
to cause relaxation of smooth muscle–blood vessels, bronchioles, GI tract and eye
what is the major function of β3?
may be in lipolysis and thermogenesis
