Efferent Division Flashcards
The sympathetic nervous branch of the autonomic nervous system is characterized by what types of fibers?
Short cholinergic pre-ganglionic fibers synapsing with
Long adrenergic post-ganglionic fibers
The parasympathetic nervous branch of the autonomic nervous system is characterized by what types of fibers?
Long cholinergic pre-ganglionic fibers synapsing with short cholinergic post-ganglionic fibers
In the autonomic nervous system, what type of neurotransmitter is released by the cholinergic fibers?
acetylcholine
In the autonomic nervous system, what type of neurotransmitter is released by the adrenergenic fibers?
norepinephrine
collateral ganglia vs terminal ganglia
collateral ganglia: A cluster of cell bodies residing outside of the sympathetic chain where some longer pre-ganglionic sympathetic fibers synapse with long post fibers.
terminal ganglia: lie near the effector organ in which the long pre-ganglionic parasympathetic fibers synapse with post fibers.
What are the three anatomical pathway for neurons in the SNS? (region where the pre-G synapse with the post-G)
- sympathetic chain adjacent to the spinal cord
- collateral ganglia
- chromaffin cell in the adrenal medulla
What is the neuronal pathway of the sympathetic pre-ganglionic neuron in the sympathetic chain?
sympathetic post ganglionic neuron pathway?
The pre ganglionic neuron exits the spinal cord via the ventral root –> to spinal nerve to –> white ramus and synapses with the post neuron in the sympathetic chain.
The post ganglionic neuron leaves the sympathetic chain via the grey ramus back to the spinal nerve and out to the effector organ.
What is the origin of parasympathetic fibers?
Brain stem and sacral region (lower end of the spinal cord)
The parasympathetic preganglionic neurons include which cranial nerves?
CN 3 - oculomotor
CN 7 - fascial
CN 9 - glossopharyngeal
CN 10 - vagus nerve
Which catecholamine hormones do the sympathetic fibers of the adrenal medulla secrete?
20% norepinephrine
80% epinephrine
small amounts of dopamine
What are the 3 layers of the adrenal medulla cortex?
From outer to inner layer:
zona gomerulosa
zona fasciculata
zona reticularis
What type of receptors do norepinephrine bind to?
In the SNS, norepinephrine are released from the post -G neuron and binds to adrenergic receptors on the effector organ or cell
What type of cholinergic receptors do cholinergic neurotransmitters bind to?
In the ANS, all preganglionic neurons are cholinergic and releases ACh which binds to nicotinic cholinergic receptors on the post G neurons
Where are muscarinic receptors found?
on the effector cell membrane and bind with acetylcholine released from the post ganglionic cell
The function of nicotinic receptor?
binds to acetylcholine released from the post ganglionic fiber and triggers the opening of ion gates in which more Na+ enters the cell as K+ exits. –> depolarization
What are muscarinic receptors and its function?
are G-protein coupled receptors located on the effector organs or tissues. They receive PNS post ganglionic neurotransmitters
Which region of the brain is the control center for cardiovascular, respiratory and digestive activity (including swallowing and vomiting)
Medulla Oblongata in the lower part of the brain stem
Where is the origin of pre ganglionic fibers from the sympathetic nervous system?
sympathetic ganglion chain near spinal cord or collateral ganglia about halfway between spinal cord and effector organ.
Where is the origin of post ganglionic fibers from the PNS?
terminal ganglia (in or near effector organs)
What type of receptors do the SNS have to receive post ganglionic neurotransmitters?
adrenergic a1,a2, b1,b2
where are nicotinic receptors found?
post ganglionic cell bodies in all autonomic ganglia
Most arterioles and veins are innervated by
a. sympathetic fibers
b. parasympathetic fibers
parasympathetic input
Most sweat glands are innervated by ________ (sympathetic fibers/parasympathetic fibers). The post ganglionic fibers of these nerves secrete ________ (acetylcholine/norepinephrine)
Sympathetic fibers.
These fibers are unusual because they secrete ACh rather than NE
What is the neuroeffector junction
refers to the synapse between the post ganglionic neuron and the effector organ
What are varicosity
are modified axon endings of sympathetic post gang. neurons located at the neuroeffector junction that releases norepinephrine
What is the difference between the events that occur at a neuroeffector junction and a cholinergic neuroeffector junction.
Cholinergic neuroeffector junction is where a PNS neuron synapses with the effector organ.
An adrenergic neuroeffector junction is where SNS neuron synapses with the effector organ
In both cases, the action potential propagated down the post ganglionic axon triggers the voltage gated ca2+ to open. The influx of ca2+ causes the neurotransmitter to be released and diffuses across the synapse. In the PNS, the post neurons are cholinergic which releases ACh that binds to the muscarinic receptors coupled G protein on the effector organ. In addition, ACh binds to an ACh enzyme that degrades ACh into acetate and choline. Choline is reuptake into the axon for reuse.
The SNS contains adrenergic post-G neurons which primarily releases norepinephrine, and epinephrine which binds to nicotinic receptors on the effector organs.
What is a neuromuscular junction
A neuromuscular junction refers to the synapse between a motor neuron and a skeletal muscle fibre in the somatic nervous system.
White vs grey rami
The grey and white rami communicantes are responsible for conveying autonomic signals, specifically for the sympathetic nervous system. Their difference in coloration is caused by differences in myelination of the nerve fibres contained within,
White vs grey rami
The grey and white rami communicantes are responsible for conveying autonomic signals, specifically for the sympathetic nervous system. Their difference in coloration is caused by differences in myelination of the nerve fibres contained within,
The white rami exist only at the levels of the spinal cord and are responsible for carrying preganglionic nerve fibres from the spinal cord to the sympathetic ganglia.
The grey rami exist at every level of the spinal cord and are responsible for carrying postganglionic nerve fibres from the sympathetic ganglia to their effector organs.
What is the difference between the autonomic and somatic division in terms of the type of neurotransmitter used at the effector organs
Autonomic nervous system:
Often is acetylcholine in the parasympathetic terminals
Often is norepinephrine in the sympathetic terminals
Somatic nervous system:
Only uses acetylcholine in the terminals
Where is the site of origin of the autonomic nervous system vs somatic
ANS: brain and lateral horn of the spinal cord
SNS: ventral horn of the spinal cord for most; those supplying muscles in head originate in brain
What type of receptors do motor neurons bind to?
nicotinic receptors on the skeletal muscle cells
Motor end plates
specializes muscle membranes
terminal bouton
the end of the axon terminal of motor nerves where action potential arrives to
What’s an end plate potential
End-plate potential (EPP), chemically induced change in electric potential of the motor end plate of the membrane of the muscle. An EPP leads to depolarization of skeletal muscle fibers resulting in muscle contraction
Acetylcholinersterase
an enzyme that degrades acetylcholine into choline for reuptake by the terminal bouton
What is latroxin and its effects?
a black widow spider toxin - stimulates the release of acetylcholine, thereby resulting in undesirable muscle contractions, spasms, and rigidity.
What are the effects of rattlesnake toxin crotoxin and butulinum toxin?
inhibits the effects of acetylcholine in the neuromuscular junction causing muscle weakness, fatigue….
What is organophosphates and how does it act on the neuromuscular junction?
Organophosphate are found in pesticides and nerve gas. It inhibits the enzyme acetycholinersterase to prevent the breakdown of acetylcholine.
