Muscular Dysgeny A case study nervous and muscular physiology You are a research
ID: 35918 • Letter: M
Question
Muscular Dysgeny
A case study nervous and muscular physiology
You are a research scientist interested in finding the cause of the cellular defect associated with the genetic disease Muscular dysgeny. You already know it is a lethal recessive, genetic disease of mice that is caused by a mutation in the mdg gene. Animals with this mutation die shortly after birth. You are interested in finding the exact defect associated with this mutation.
You surgically remove a single motor unit from a normal mouse fetus and a dysgenic mouse fetus. You place the neuron/muscle fiber unit in an experimental chamber in order to study abnormalities.
1. Define each of the following:
motor neuron
synapse
synaptic knob (endbulb)
sarcolemma
t-tubules
sarcoplasmic reticulum
motor end plate.
2. Place the following steps for an action potential in the correct order:
1. Voltage gated Na+ channels open
2. Na+ rushes in
3. Potential moves toward and above zero to + 30 mV
4. Voltage gated K+ channels open
5. K+ rushes out
6. Na+/K+ pump restores RP
7. Graded potential reaches TP
8. Potential moves toward RP and past to
Explanation / Answer
1.
Motor Neuron:
The neuron whose cell body is located in the spinal cord and whose axon projects outside the spinal cord in to the effector organs like muscles and glands is known as Motor neuron. They receive the signals from the spinal cord and carry them to the effector organs.
Synapse:
The junction or the point where the signals pass from one neuron to the other neuron is known as synapse.
Synaptic knob:
The termination of sensory nerve fiber is known as synaptic knob.
Sarcolemma:
Sarcolemma is cell membrane of striated muscle fiber. The plasma membrane of sarcolemma is a lipid bilayer with a thin polysaccharide.
T-tubule:
T-tubules are known as transverse tubules. The extensions of the sarcolemma into the center of cardiac and skeletal muscle cells are known as t-tubules. They contain the proteins that act as ion channels and allow electrical impulses along the sarcolemma.
Sarcoplasmic reticulum:
The endoplasmic reticulum present in the muscle cells is known as the sarcoplasmic reticulum. This is a membrane bound structure. They maintain the calcium levels in the cells.
Motor end plate:
The terminal by which the axon of a motor neuron establishes a synaptic contact with striated muscle is known as motor end plate.
2.
The correct order of action potentials is:
7. Graded potential reaches TP
1. Voltage gated Na+ channels open
2. Na+ rushes in
3. Potential moves toward and above zero to + 30 mV
4. Voltage gated K+ channels open
5. K+ rushes out
8. Potential moves toward RP and past to
6. Na+/K+ pump restores RP
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