Most sensory receptors function by producing depolarising potentials. Which of the following function by hyperpolarization rather than depolarization ?

1. proprioceptors
2. nociceptors
3. olfactory receptors
4. rods and cones

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.

When a neuron is an resting state, ie, not conducting any impulse, the axonal membrane

is

1. equally permeable to both Na⁺ and K⁺ ions

2. impermeable to both Na⁺ and K⁺ ions

3. comparatively more permeable to K⁺ ions and nearly impermeable to Na⁺ ions

4. comparatively more permeable to Na⁺ ions and nearly impermeable to K⁺ ions

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

Neurons are excitable cells because