Which of the following minerals reduces the excitability of nerves and muscles?
1. Potassium
2. Sodium
3. Magnesium
4. Manganese
Node of Ranvier occurs where
(1) nerve is covered with myelin sheath
(2) neurolemma is discontinuous
(3) neurolemma and myelin sheath are discontinuous
(4) myelin sheath is discontinuous
During the propagation of a nerve impulse, the action potential results from the movement of
1. K+ ions from extracelular fluid to intracellular fluid
2. Na+ ions from intracellular fluid to extracellular fluid
3. K+ ions from intracellular fluid to extracellular fluid
4. Na+ ions from extracellular fluid to intracellular fluid
Consider the following statements:
I. Acetylcholine is released at the electric synapse.
II. Electric synapses are faster.
III. It is more difficult to regulate an electric synapse with respect to a chemical synapse.
Which of the above statements are true?
1. I and II only
2. I and III only
3. II and III only
4. I, II, and III
Consider the following statements:
I: | The resting axonal membrane is nearly impermeable to sodium ions. |
II: | Depolarization of the axonal membrane is due to the influx of sodium ions. |
III: | The size of the action potential, if produced, does not depend on the strength of the stimulus. |
Which of the above statements are true?
1. I and II only
2. I and III only
3. II and III only
4. I, II and III
Consider the following statements:
I. Somatic neural system relays impulses from CNS to skeletal muscles.
II. Autonomic neural system transmits impulses from CNS to involuntary organs and smooth muscles.
III. Unmyelinated nerve fibres are commonly found in spinal and cranial nerves.
Which of the above statements are true?
1. I and II only
2. I and III only
3. II and III only
4. I, II, and III
In a chemical synapse, when an impulse arrives at the axon terminal, it:
1. leads to the opening of the calcium channels at the post-synaptic membrane.
2. Stimulates the fusion of synaptic vesicles towards the pre-synaptic membrane.
3. causes the binding of the neurotransmitter of its receptors on the post-synaptic neuron.
4. activates the opening of the potassium channels in the axon terminal.
Immediately after an action potential has peaked, which cellular gates open?
1. Sodium
2. Chloride
3. Calcium
4. Potassium
Neuron cannot perform which of the following functions?
(1) Detection of stimuli
(2) Receiving stimuli
(3) Transmitting different kinds of stimuli
(4) Giving nutrition to neuroglial cells
Which of the following does not has brain?
(1) Hydra
(2) Insects
(3) Vertebrates
(4) Earthworm