Lower Motor Neurons and NM Junction

What is an efferent neuron of the peripheral nervous system that connects the central nervous system with the muscle or gland to be innervated?

Lower Motor Neuron

What are the two components of the Lower Motor Neuron?

-Somatic Motor

-Visceral Motor

Which component of the Lower Motor Neuron is considered a traditional motor neurons and directly innervate skeletal muscle?

Somatic Motor Neuron

1 multiple choice option

Which component of the Lower Motor Neuron is considered a component of the ANS and regulates smooth muscles and glands?

Visceral Motor Neuron

1 multiple choice option

T/F: The entire function of the CNS is manifested through the lower motor neuron.

True

1 multiple choice option

LMNs are located in the...

Ventral Gray Matter of the spinal cord

LMNs are found in all cranial nerves except for...

-I

-II

-VIII

The axons of LMNs in the ventral gray matter of the spinal cord leaves through the...

Ventral Root

The axons of LMNs in cranial nerves leave through the...

Skull

Since LMNs provide their own efferent signals what does this allow?

-Constant Muscle Tone

-Reflexive movements without brain involvement

T/F: LMNs can function even when the signal from the brain is completely damaged or interrupted.

True

1 multiple choice option

What spinal nerves are in the cervical subdivision of the spinal cord?

C1-C5

3 multiple choice options

What spinal nerves are in the thoracic limb subdivision of the spinal cord?

C6-T2

3 multiple choice options

What spinal nerves are in the thoracolumbar subdivision of the spinal cord?

T3-L3

3 multiple choice options

What spinal nerves are in the pelvic limb subdivision of the spinal cord?

L4-S1

3 multiple choice options

What spinal nerves are in the sacrocaudal subdivision of the spinal cord?

S1-S3

3 multiple choice options

What 3 subdivisions of the spinal cord are considered part of the LMN system?

-Thoracic Limb

-Pelvic Limb

-Sacrocaudal

What 2 subdivisions of the spinal cord are considered part of the UMN system?

-Cervical

-Trunci/Thoracolumbar

The upper motor neuron is located within the...

CNS

What part of the lower motor neuron is the alpha motor neuron and the extrafusal fibers it supplies?

Motor Unit

What is the synapse between the axons of motor neurons and skeletal muscle fibers?

Neuromuscular Junction

What triggers the release of Ach by exocytosis from the active zone of the axon terminal?

Influx of Ca++

What causes the influx of Ca++ into the presynaptic axon terminal?

Action potential travels down the presynaptic motor axon terminal

What causes the phenomenon of End Plate Potential?

Increase in permeability of postjunctional Na+ and K+

What drug sompetes with ACh to bind to postsynaptic nicotinic receptors, causing the animal to become paralyzed?

Curare

What are the nicotinic signs of organophosphate toxicity?

-Tremors progressing to paralysis

-Neuromuscular weakness

-Seizures

What are the muscarinic signs of organophosphate toxicity?

-Excessive salivation

-increased defecation/diarrhea

-Vomiting

-Bradycardia

-Bronchospasm

What diseases are considered disorders of the NM junction?

-Myasthenia gravis

-Botulism

-Tick Paralysis

What disease has antibodies form against the nicotinic ACh receptors causing a diminished NM conduction?

Myasthenia gravis

What disease interferes with docking proteins by blocking one or more of the synaptic vesicle proteins causing a diminished NM conduction and weakened muscles?

Botulism

Which disease is caused by decreased calcium entry and consequently interferes with vesicular exocytosis and NT release?

Tick Paralysis