44 Questions
What is the location of the cell body of a motor neuron?
Spinal cord or brainstem
What is the function of a motor neuron in relation to skeletal muscle fibers?
To control the contraction of muscle fibers
What is the term for the specialized synapse between a motor nerve ending and a muscle fiber?
Neuromuscular junction
How many motor endplates are typically present on a single muscle fiber?
One
What is the direction of transmission of electric impulses at the neuromuscular junction?
Unidirectional
What is the term for a motor nerve axon ending with up to 50 synaptic knobs/boutons?
Motor unit
What is the primary function of a motor unit?
To control the contraction of multiple muscle fibers
What characteristic of motor units allows for precise adjustments in force?
Recruitment and gradation of motor units
What is unique about the motor units responsible for extraocular muscle function?
They have a small number of myofibers
What happens when a motor neuron is activated?
All of the innervated muscle fibers contract simultaneously
What is the primary factor determining the size of a motor unit?
The number of myofibers innervated
What is the functional difference between motor units in the quadriceps muscle and those in extraocular muscles?
Quadriceps motor units are larger and control powerful movements
What is the main component of the synaptic vesicles in the presynaptic terminal?
Acetylcholine
What is the function of the active zone in the presynaptic terminal?
Holds synaptic vesicles in the right place
What is the consequence of the binding of ACh to nicotinic receptors in the postsynaptic membrane?
Depolarization of the muscle fiber membrane
What is the enzyme responsible for the degradation of ACh in the synaptic cleft?
Acetylcholinesterase
What is the clinical sign of botulism in animals?
Progressive motor paralysis
What is the effect of organophosphate toxicosis on acetylcholinesterase?
Irreversible inactivation
What is the role of the synaptic cleft in the neuromuscular junction?
Contains extracellular fluid and matrix molecules
What is the consequence of the abnormal reduction in the number of Ach receptors on the neuromuscular endplate?
Exercise-induced weakness
What is the function of the voltage-gated calcium channels in the presynaptic terminal?
Allow calcium to enter the presynaptic terminal
What is the role of SNARE proteins in the neuromuscular junction?
Promote docking, fusion, and release of ACh by exocytosis
What is the main function of a motor neuron in relation to muscle fibers?
To control the contraction of muscle fibers
What is the term for the area of the muscle fiber membrane where a synapse occurs with a motor nerve axon?
Motor endplate
What is the typical number of motor endplates present on a single muscle fiber?
One
What is the role of acetylcholine in the neuromuscular transmission?
To facilitate the transmission of electric impulses
What is the characteristic of the transmission of electric impulses at the neuromuscular junction?
Unidirectional
What is the term for the group of muscle fibers that can be controlled by a single motor neuron?
Motor unit
What is the primary factor that determines the strength of muscle contraction?
Frequency of motor unit activation
Which of the following muscles has motor units with a large number of myofibers?
Quadriceps muscle
What is the characteristic of motor units that allows for precise adjustments in force?
Recruitment and gradation of force
What is the consequence of activating a motor neuron?
All innervated muscle fibers contract simultaneously
What is the functional difference between motor units in the quadriceps muscle and those in extraocular muscles?
Size of motor units
What is the purpose of varying the number of motor units activated?
To make precise adjustments in force
What is the shape of the presynaptic terminal at the neuromuscular junction?
Button-like
Which proteins are responsible for holding the synaptic vesicles in the right place at the active zone?
Specific proteins
What is the role of mitochondria in the presynaptic terminal?
To provide energy for the production and release of Acetylcholine
What is the name of the receptors that bind to Acetylcholine and nicotine in the postsynaptic membrane?
Nicotinic receptors
What is the result of the binding of Acetylcholine to its receptors in the postsynaptic membrane?
Depolarization of the muscle fiber
What is the purpose of the subneural clefts in the synaptic cleft?
To increase the surface area for neurotransmitter binding
What is the effect of botulinum toxin on the neuromuscular junction?
It destroys SNARE proteins
What is the clinical sign of organophosphate toxicosis in animals?
All of the above
What is the effect of the abnormal reduction in the number of Ach receptors on the neuromuscular endplate?
Exercise-induced weakness
What is the role of Acetylcholinesterase in the synaptic cleft?
To break down Acetylcholine
This quiz covers the components of a neuromuscular junction, motor units, and the role of acetylcholine in neuromuscular transmission. It also explores the effects of Botulinic toxin, Organophosphate/Carbamate pesticides, and Myasthenia Gravis on neuromuscular transmission.
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