MDS PREP
Which of the following statements about the sensory neurons and their pathways in the spinal cord is correct?
1) All sensory neurons synapse with motor neurons in the ventral horn to form spinal reflex arcs
2) Only pain and temperature sensations ascend to the brainstem for conscious perception
3) The axons of sensory neurons from the dorsal root ganglion may directly synapse with motor neurons or ascend to the brain
4) Sensory neurons only project to the reticular formation and thalamus for nonspecific arousal
The axons of sensory neurons from the dorsal root ganglion can follow three routes: forming spinal reflexes by synapsing with motor neurons, ascending to the brainstem for conscious perception, or relaying through the reticular formation and thalamus for general arousal.
What is the role of ghrelin in the control of food intake?
1) It stimulates the release of growth hormone
2) It suppresses the secretion of gastric acid
3) It inhibits food intake
4) It increases the sensation of hunger
Ghrelin increases the sensation of hunger, stimulating appetite and food intake, particularly before meals.
What is the primary inhibitory neurotransmitter in the central nervous system?
1) Dopamine
2) GABA (gamma-aminobutyric acid)
3) Glutamate
4) Acetylcholine
GABA is the main inhibitory neurotransmitter in the central nervous system, playing a crucial role in reducing the excitability of neurons and contributing to the regulation of neural circuits and synaptic plasticity.
MCQ: The physiological capacity of the bladder, at which micturition is normally effected, ranges between:
1) 150 ml - 250 ml
2) 250 ml - 450 ml
3) 450 ml - 750 ml
4) 750 ml - 1000 ml
The physiological capacity of the bladder, at which micturition is normally effected, ranges between 250 ml - 450 ml, indicating the volume at which the urge to urinate is felt.
What is the role of the acrosome in sperm penetration of the egg during fertilization?
1) It produces energy for the sperm's movement
2) It contains enzymes that help dissolve the egg's outer layers
3) It transfers genetic material to the egg
4) It has no role in the penetration process
The acrosome in sperm contains enzymes that help dissolve the egg's outer layers, facilitating sperm penetration during fertilization.
What is the significance of the blood-brain barrier being absent in the circumventricular organs?
1) Allows free passage of hormones and neurotransmitters to the cerebrospinal fluid (CSF)
2) Enables direct interaction with the hypothalamus for osmoregulation
3) Facilitates the entry of pathogens and drugs into the brain
4) Necessary for the synthesis of neurotransmitters in these areas
The absence of the blood-brain barrier in circumventricular organs allows for the unimpeded movement of substances between the blood and the CSF, which is crucial for the regulation of various physiological processes, including osmoregulation.
What type of sleep is associated with sleep spindles and K complexes?
1) Stage 1 NREM
2) Stage 2 NREM
3) Stage 3 NREM
4) REM sleep
While sleep spindles and K complexes are prominent in Stage 2 NREM sleep, they can also be present in the transition between wakefulness and sleep, which is considered part of Stage 1 NREM sleep.
What is the primary effect of excitatory postsynaptic potentials (EPSPs) on the excitability of a neuron?
1) Depolarization
2) Hyperpolarization
3) No change in excitability
4) Initiation of an action potential
Answer: 1) DepolarizationExplanation: EPSPs occur when the neurotransmitter binds to postsynaptic receptors that open sodium channels, allowing sodium ions to flow into the neuron and causing the membrane to depolarize. This increases the excitability of the neuron, bringing the membrane potential closer to the threshold for action potential firing.