Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neurobiology > Motor Neurons/ Motor Units/ Neuromuscular synapses > Flashcards

Motor Neurons/ Motor Units/ Neuromuscular synapses Flashcards

1
Q

ACH (Acetylcholine NT)

A

Synthesis (precursor enzymes):

  • Enzymes
  • Cell body
  • Acetyl CoA & Choline
  • in terminal

Storage & Release:

  • Small clear vesicles

Effect:

  • Nicotinic
  • EPSP
  • Can also be muscarinic

Removal:

  • AChE reputake by Choline
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Dopamine (DA)

A

Synthesis (precursor & enzymes)

  • Tyrosine hydroxylase & Tyrosine

Effect:

  • EPSP on metabotropic

Removal:

  • Reuptake- neuron or glia by NET/DET
  • Diffusion, inactivation (COMT) Enzymes MAO , COMT
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Norepinephrine (NE)

A

Synthesis (precursor enzymes):

  • Tyrosine hydroxylase, tyrosine

Effect:

  • EPSP on metabotropic

Removal:

  • Reuptake- neuron or glia by NET/DET
  • Diffusion, inactivation (COMT) Enzymes MAO , COMT
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Glutamate

A

Synthesis (precursor enzymes):

  • Glutamine in terminal

Storage & release:

  • Small, clear vesicles

Effect:

  • EPSP on metabotropic and ionotropic

Removal:

  • Reuptake by neuron & glia, recycled, enzymes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

GABA

A

Synthesis (precursor enzymes):

  • Glucose to glutamate

Storage & release:

  • Small, clear vesicles

Effect:

  • IPSP on metabotropic and ionotropic

Removal:

  • Reuptake by neuron & glia, recycled, enzymes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Neuropeptides

A

Synthesis (precursor enzymes):

  • Prepropeptide made in cell body, processed in mature terminal

Storage and release:

  • Large dense vesicles

Effect:

  • Metabotropic

Removal:

  • Peptidases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Lower Motor Neurons

(Commanded by the muscle to move in the CNS)

A

Somatic Motor Neurons (2 types):

  • Alpha motor neurons
    • Innervate skeletal muscles- main force generating muscles
    • Referred to LMN–> final command
  • Gamma motor neurons
    • Innervate the stretch sensing organ within a muscle

Visceral motor neurons:

  • Input from CNS (cell bodies in spinal cord & brain stem) to organs, cardiac muscle and smooth muscle)
  • Autonomic nervous system telling the gut how to contract
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Motor Unit (LMN)

A
  • Single alpha motor neuron that has multiple terminals that synapse on individual muscle cells
  • Called a motor unit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Muscle cells

A
  • Muscle fibers (myofibers/myocytes)
  • 1 muscle cell is ONLY innervated by 1 motorneuron
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Motor Unit:

A
  • 1 Motor neuron innervates multiple muscle cells = myofibers/myocytes
  • A muscle cell contails mutiple myofibrils (actin/myosin)
  • 1 motor neuron has multiple terminals which synapse on individual muscle cells
  • Single axon branches innervate multiple muscle cells
    • Fibers are scattered over a large area of muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Motor neuron pool refers to:

A

All the alpha motor neurons (motor units) that innervate a single muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Motor Unit to Skeletal Muscle

A
  • 1 alpha motor neuron with multiple
  • terminals which synapse on
  • individual muscle cells = muscle fibers (myofibers/myocytes) which contain
  • myofibrils
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

The cell bodies of Alpha motor neurons are located:

A

in the ventral horn of the spinal cord

Sensory Afferent

Motor Efferent

(SAME)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Motor Units & Integration

A
  • Alpha motor neurons are integrators
  • Inputs to alpha motor neurons
    • Receive many synapses from multiple sources both excitatory and inhibitory
  • Large neurons
  • Lengthy, branched dendrites
  • Synapses on muscle fibers (one neuron to many fibers)

ONLY generate AP in the muscle after a voltage threshold is exceeded!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q
A
17
Q

CNS: Activation of Movement via Muscle Contraction

A
  • Inputs from alpha motor neurons
  • ONLY pathway for CNS to activate movement via muscle contraction
    • Synapse with Smooth and Cardiac Muscle
      • Mutiple cells/synapse (2 neuron chain to reach smooth muscle, ANS)
      • Can have Gap Junction Coupling
      • Norepinephrine (NE) major transmitter
      • Ach, seretonin, and others too
    • Synapse with skeletal muscle
      • 1 alpha motor neuron/muscle cell
      • Ach is the only NT
18
Q

Neuromuscular Junction: Basics

CHEMICAL SYNAPSE!

A
  • Location where alpha motor neuron terminals synapse on skeletal muscles
  • Model for synaptic action
  • Synaptic structure is similiar to neuron-neuron synapse
    • Presynaptic Axon
    • Presynaptic Membrane
    • Synaptic Cleft
    • Postsynaptic membrane
      • Muscle Cell
19
Q

Neuromuscular Junction Logistics:

A

Motor end-plate: muscles post-synaptic membrane which motor neuron innervates

  • 1 motor neuron can innervate multiple muscle fibers
  • Motor axon loses its myelin sheath and then it branches to synapse on multiple cells at the motor-end plate region
    • Junctional folds in motor end-plate region and a cleft filled with mucopolysaccharide “glue”
  • Varicosities (contact from alpha motor neuron) covered by Schwann cells- each acts as a synaptic bouton
  • Ach released from presynaptic boutons
  • Ligand gated ion channels
  • Voltage gated Na+ channels
    *
20
Q

Neuromuscular Junction- Synaptic Cleft

A
  • Within the synaptic cleft, basement membrane is present
    • Basement membrane holds the neuron to the muscle fiber
    • Collagen and ECM proteins
    • Forms an anchor for acetylcholinesterase (recycles Ach)
  • ​Junctional folds on postsynaptic cell = Ach receptors & voltage gated channels
21
Q

Muscle Receptor at Neuromuscular Junction

A
  • Ach released at NMJ
  • Nicotinic, Ionotropic receptor
  • Very fast transmission
  • Muscle receptors located in the crests of the folds
    *
22
Q

Nicotinic Receptors

A
  • Neuromuscular Junction
  • Found in muscle
  • Curare (antagonist)
  • Ach = only muscles
23
Q

Electrical Events at Neuromuscular Junctions

(Initiating an AP in Muscle)

A

Alpha motor neurons excite muscle by opening channels at the endplate - Na+ ligand-gated channels on muscle cell

  • AP travels down motor neuron axon to terminal
  • Voltage gated Ca2+ channels open
  • Ca2+ enters the terminal causing Ach release via exocytosis
  • Ach diffuses across the synaptic cleft and binds Ach receptors on the muscle cell
  • ACH binding causes ligand-gated cation channels to open
  • Na+ enters muscle fiber & K+ leaves the muscle fiber

Net influx of Na+ into muscle fiber= membrane potential less (-)

  • Acetylcholinesterase breaks down Ach into choline and acetate- channels close
  • Reuptake of Ach @ presynaptic membrane

Threshold reached = AP propagates along sarcolemma

  • 70 mV depolarization
  • EPP (way more dramatic than EPSP)

** Caused by ionic current through Ach channel

24
Q

EPP vs. EPSP

A

Endplate Potential (EPP): Always Excitatory

  • Multiple synapses on endplate
  • Input from only 1 cell
  • Dramatic
  • Large synaptic potential
  • Endplate potential = 70 mV depolarization
  • ALWAYS EXCITATORY- Ach used
  • Refers to a change in membrane charge that causes the initiation of an action potential –> that propagates down the muscle fiber
  • Non-integrating after motor neuron integrates

Excitatory Post-Synaptic Potential (EPSP):

  • NT causes change in postsynaptic cell membrane potential (Vm)
  • Input from 1000’s of neurons
  • Functional diversity: excitatory and inhibitory–> NT diversity
  • Small post-synaptic potential
  • Small amount of NT released
  • Integrating = summation
  • Depolarization
  • Increased Vm
  • Moves toward threshold
25
Q

What happens at NMJ when motor neuron is damaged?

A

Happens in skeletal muscle, smooth muscle, glands

Alpha motor neuron was secreting trophic growth factors that kept it healthy and Ach receptors localized at the end plate

Axon destroyed= dismantling of NMJ

Damage results in the receptors spreading further away from the endplate region

Don’t have a mechanism to get rid of the Ach

26
Q

Properties of EPP

A
  • Synaptic potential
    • increases rapidly, decreases slowly
    • rapid rise b/c of flood of Ach into cleft
    • Ach diffuses through cleft to receptors on endplate
    • Not all Ach reaches endplate
  • Removed by
    • diffusion out of cleft
    • inactivation via hydrolysis
27
Q

EPP is NOT ALL OR NONE

A
  • Stimulate motor axons
  • Spreads passively
  • Membrane potenntial falls with distance from motor end plate

Neurobiology (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions