The Nervous System

Question 1

What is the nervous system?

Answer 1

A collection of interconnected neurons that transmit messages as electrical signals to different parts of the body.

Question 2

Why do large organisms need a nervous system?

Answer 2

To coordinate behaviour and respond to stimuli in their environment.

Question 3

Give the function and adaptations of neurons. (4)

Answer 3

1. Function: carry electrical impulses
2. Adaptations:
   - Long, thin shape
   - Axon branched endings connect to other neurons
   - Myelin sheath (insulating layer that helps to transmit electrical impulses quickly and efficiently along nerve cells)

Question 4

Explain how nerves transmit electrical signals to each other. (3)

Answer 4

1. Nerve impulses cannot cross synapses, so information is sent by neurotransmitters.
2. When a presynaptic neuron receives an electrical impulse, it stimulates the release of neurotransmitters from the end of the presysnaptic neuron from the synaptic vesicle.
3. These then diffuse across the synapse and bind with the receptor molecules on the postsynaptic neuron’s membrane, which stimulates a new nerve impulse in the postsynaptic neuron for the process to repeat.

Question 5

What is the central nervous system made up of?

Answer 5

Brain and spinal cord.

Question 6

How does the CNS work?

Answer 6

1. Receives information (e.g. changes in temperature, levels of CO2 in blood) from sensory neurons that carry information from receptors to the CNS
2. Then the CNS sends electrical impulses back into the body through motor neurons to effectors (e.g. muscles (to contract), glands (to release hormones))

Question 7

What is a reflex arc?

Answer 7

Nerve pathway that controls a reflex

Question 8

What is the benefit of reflexes?

Answer 8

They are rapid and automatic, so we can respond to stimuli quickly

Question 9

Explain how a reflex arc works.

Answer 9

1. A stimuli is detected by receptor cells in the skin which then stimulates a sensory neuron that will carry an electrical impulse from the location of the stimuli to the spinal cord
2. The impulse is then transferred to a relay neuron in the spinal cord
3. It is then passed on to a motor neuron, where it travels back to the body to an effector that will contract and respond in some way to the stimulus