CH 11: efferent division - autonomic and somatic motor control Flashcards
What type of neuron carries out commands from the CNS to the muscles and glands of the body? How can it be further divided?
- Efferent neurons
- Further divided into:
- Somatic motor neurons: control skeletal muscles, mostly voluntary
- Autonomic neurons: control smooth muscle, cardiac muscle, glands, and some adipose tissue, mostly involuntary
***Diaphragm controlled by both!
What does the sympathetic branch of the autonomic system do?
fight or flight
What does the parasympathetic branch of the autonomic division do?
rest and digest
What type of control is primarily used in the autonomic division? (agonist, antagonist, mixed, etc)?
- antagonistic
- one branch is (sympathetic) excitatory and the other one (parasympathetic) is inhibitory
- some exceptions (sweat glands & BV only by sympathetic & rely on tonic [up regulation] control)
- sometimes they can work together and have different functions
- neurotransmitter receptor often determines response in the target tissue
What is a ganglion?
- a cluster of neuronal cell bodies outside the CNS
- equivilant in CNS is nucleus
- act as mini-integration centers
Is the autonomic ganglion closer to the CNS or the target tissue in parasympathetic?
target tissue (or more in the middle)
What neurotransmitter does the preganglionic neuron release in the parasympathetic division and what receptor on the ganglion does it bind to?
- acetylcholine
- binds to nicotinic receptors
Is the autonomic ganglion closer to the CNS or the target tissue in sympathetic?
CNS (close to preganglioninc neuron)
What neurotransmitter does the preganglionic neuron release in the sympathetic division and what receptor on the ganglion does it bind to?
- acetylcholine
- binds to nicotinic receptors
Where are the ganglions in the sympathetic and parasympathetic pathways (CNS or PNS)?
PNS
What neurotransmitter does the postganglionic neuron release in the parasympathetic division and what receptor on the target cell does it bind to?
- acetylcholine
- binds to muscarinic receptor (GPCRs —> second messenger changes)
What neurotransmitter does the postganglionic neuron release in the sympathetic division and what receptor on the target cell does it bind to?
- norepinephrine
- adenergic receptors
What is the preganglionic neuron?
- first neuron in chain with cell body in CNS
- projects from CNS to an autonomic ganglion outside the CNS
- synapses with postganglionic neuron
what is the postganglionic neuron?
- second neuron in the chain with cell body located in the autonomic ganglion
- projects from an autonomic ganglion to the target tissue
- synapses with target cell
Look at slide 13 & 14
What is the neuroeffector junction?
synapse between postganglionic autonomic neuron and target cell
What is varicosity?
- swelling in regions of axon – represents end of postganglionic neuron (looks like beading)
- have neurotransmitters and APs cause cause them to be released (throuhg large area, not just 1 small)
Can the release of autonomic neurotransmitters be modulated?
Yes
Where are autonomic neurons synthesized?
in the axon
What is the neuromuscular junction?
the synapse between somatic motor neuron and skeletal muscle
What is the adreanal medulla (type of tissue, neurotransmitters released, pre & post synaptic ganglion, etc)?
- has modified nerve cells
- secreats norepinephrine and epinephrine neurohormones
- neuron doctrine tissue
- Innervated by sympathetic pregangionic fibers
- post-ganglionic neuron lacks axon (chromaffin cells)
- PG neuron secretes epinephrine (neurohormone) into blood
How does norepinephrine get released and removed at the varicosity?
- AP arrives at varicosity
- Depolarization opens voltage gated Ca2+ channels
- Ca2+ entry triggers exocytosis of synaptic vesicles
- NE binds to andrenergic receptor on target
- Receptor activation ceases when NE diffuses away from the synapse
- NE is removed from the synapse
- NE can be taken back into synaptic vesicles for re-release
- NE is metabolized by monoamine oxidase (MAO)
Where are autonomic neurotransmitters synthesized?
in the axon
Does every autonomic receptor have the same affinity for neurotransmitters?
No! some prefer NE, 1 prefers E (b2), and 1 is equal (b1)
What is a catecholamine?
a hormone released from the adrenal medulla
Where does the somatic motor pathways originate & facts about?
- In the CNS (brain or ventral horn of spinal cord)
- myelinated, very long, always excitatory
- terminal branches close to target
- each terminal innervated single target
What kind of receptors are in the neuromuscular junction?
nicotinic
What is a motor end plate?
- a series of folds that look like shallow gutters to increase surface receptors
- on postsynaptic side of neuromuscular junction
- on skeletal muscle cell membrane
- have SEVERAL ACh receptors
What enzyme is in the neuromuscular junction to break down neurotransmitters?
achetylcholinesterase (AChE)
What channels are on skeletal muscles?
- nAChR channels of skeletal muscle (NM subtype)
- similar to NN ACh receptors
- Chemically-gated channels with 2 binding sites for ACh
- Always excitatory (muscle contraction)
What receptors are on neurons?
- NN ACh receptors
What are the components of the neuromuscular junction?
axon terminals, motor end plates on muscle membrane, and schwann cell sheaths
Look at figure 11.10 ©-(e)
