The left side of the cerebrum controls skeletal muscles on the right side of the
ID: 3509376 • Letter: T
Question
The left side of the cerebrum controls skeletal muscles on the right side of the body because motor neurons cross from left to right in the:
precentral gyrus.
cerebellum.
medulla oblongata.
hypothalamus.
thalamus
Which of the following statements is CORRECT regarding dendrites?
They are processes extending from the axon
They can produce postsynaptic potentials
They pass chemical information to another neuron by forming synapses
They contain vesicles with neurotransmitters
Which of the following structures in the neuron is where the action potentials start?
Axon collaterals
Axon terminals
Axon hillock
Initial segment
None of the above
Explanation / Answer
Answer:
1) Medulla oblongata.
The pyramidal tracts are concerned with voluntary activities of the body. They are also called corticospinal tracts.
Pathway
Origin: from the nerve cells in the cerebral cortex of primary motor area; area 4, Premotor area; area 6, other parts of the frontal lobe and areas of the parietal lobe.
Course: They descend through the internal capsule, midbrain, and pons and on reaching the lower part of the medulla, 80% of these fibers decussate, that is, they cross to the opposite side and enter the spinal cord and terminate at the anterior gray horn cells here.
Due to the crossing over happening at the medulla, the skeletal muscles on the right side of the body is gets controlled by the left side of the cerebrum.
2) True regarding dendrites:
B) They can produce postsynaptic signals: When neurotransmitters are released into the synaptic cleft at the axon terminal, they bind to the receptors at the postsynaptic membrane on the dendrite. This leads to an influx of ions and this movement causes the development of postsynaptic signals within them which could be excitatory or inhibitory in nature.
option a is wrong because dendrites extend from the cell body or soma of a neuron and not the axon.
Option c is wrong because dendrites receive information and axons pass it to adjacent neurons at the synapse.
Option d is wrong because axons contain vesicles with neurotransmitters and not dendrites.
3) Where do action potentials begin?
Answer: option D; initial segment.
This is located between the axon hillock and where the axonal structure (node of Ranvier in myelinated nerves) begin. There are numerous specific voltage-gated channel here which helps in generating the action potential.
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