Mammalian Nervous System (Cambridge O Level Biology)

Complete the five sentences about the eye and the nervous system.

Structures in the eye change the shape of the lens so that the eye can focus on near and distant objects. This is called ............................................... .

The radial and circular muscles in the iris of the eye are a pair of .............................................. muscles that work against each other.

Muscles in the eye are controlled by the nervous system.

The .............................................. nervous system contains only sensory and motor neurones.

The .............................................. nerve from the eye contains sensory neurones that conduct impulses to the ............................................... .

Transmission of impulses relies on the flow of ions through the cell membranes of neurones down their concentration gradients. Active transport is responsible for maintaining the concentration gradients of ions across the membranes of neurones.

Explain how ions are moved across membranes by active transport.

Fig. 1 shows the junction between two neurones.

Fig. 1

Many drugs interfere with the action of neurotransmitters at the junctions between neurones.

Two drugs that influence the transmission of impulses between neurones are atropine and eserine. The actions of these drugs are shown in Table 1.

Table 1

Explain the effects of these two drugs on the nervous system using the information in Fig. 1 and Table 1.

Define the term sensitivity.

Fig. 1 shows the reflex arc involved in a simple reflex action.

Fig. 1

On Fig. 1, use label lines to identify and name the three types of neurone shown. 

A reflex is an involuntary action.

Explain what is meant by the term involuntary action.

[1]

[3]

When a body senses danger, more adrenaline is secreted from the adrenal glands.

Describe two ways in which the hormone adrenaline affects the body in preparation for action.

State one difference between nervous and hormonal control systems.