Stimuli, both internal and external, are detected and lead to a response (A-level only)：练习题

• a.The channels actively pump sodium ions out of the neurone to create a resting potential.
• b.The channels open in response to a neurotransmitter binding to a receptor.
• c.The channels close to prevent the loss of potassium ions from the axon.
• d.The channels deform, allowing sodium ions to diffuse into the neurone.

• a.The reflex is voluntary and involves the processing of information in the cerebral cortex.
• b.The impulse bypasses the spinal cord and travels directly from the receptor to the effector muscle.
• c.The speed of the response is slow because it relies on the diffusion of hormones through the blood.
• d.The impulse travels through a sensory neurone, an intermediate neurone in the spinal cord, and a motor neurone.

• a.It delays the electrical impulse to allow the ventricles to fill completely before contracting.
• b.It contains chemoreceptors that detect changes in blood carbon dioxide levels.
• c.It conducts electrical impulses rapidly down the septum to the apex of the heart.
• d.It acts as a pacemaker by sending out regular waves of electrical activity to the atrial walls.

• a.Each rod cell connects to a single bipolar cell for high acuity; multiple cone cells share a bipolar cell for high sensitivity.
• b.Several rod cells share a single bipolar cell, resulting in low acuity; each cone cell connects to its own bipolar cell, resulting in high acuity.
• c.Cone cells are linked in groups to one bipolar cell to ensure spatial summation, which increases acuity in low light.
• d.Both rod and cone cells share bipolar cells, but rod cells have more rhodopsin which increases acuity in bright light.

先自己写一遍答案，再对照解题步骤。

先自己写一遍答案，再对照解题步骤。