GCSE Biology- Structure and Function of the Nervous System

What is a reflex?

A reflex is a rapid, involuntary movement in response to a stimulus. Reflexes are usually protective, preventing serious harm to the body and reducing tissue damage.

Examples of reflexes

Knee Jerk, Blinking, Baby gripping, Shivering, Sneezing, withdrawing your hand from a hot object

What is the CNS?

The CNS, or Central Nervous System is comprised of the brain and spinal cord.

What is the Peripheral Nervous System?

The Peripheral Nervous System contains cranial nerves, spinal nerves and peripheral (everything else) nerves.

What is the difference between a nerve cell (neurone) and a nerve?

A nerve is a bundle of neurones, whereas a neurone is a single cell.

What is the function of a sensory neurone?

To carry electrical nerve impulses from the receptor towards the CNS.

What is the function of a relay neurone?

To transmit the electrical impulse from the sensory neurone to the motor neurone. Relay neurones carry impulses within the CNS.

What is the function of a motor neurone?

To carry electrical nerve impulses from the CNS and relay neurone to the effector.

What is a reflex arc and why is the word 'arc' used?

A reflex arc is a nerve pathway. It is called an arc because the pathway goes into the CNS and back out again.

What is a synapse?

A synapse is a gap between two neurones. It is very small, only a few nanometres in length. Electrical impulses cannot cross the gap. Instead, chemicals called neurotransmitters cross the gap to transfer the signal.

Why are synapses important?

Synapses are important in controlling where electrical impulses are sent (from receptors to processing centres and then effectors to cause different responses)

How do electrical impulses travel through synapses? (1)

An electrical impulse reaches the end of neurone A. This is the axon terminal of the pre-synaptic neurone.

How do electrical impulses travel through synapses? (2)

This signals vesicles (small bubbles) containing a neurotransmitter to move to the cell membrane and fuse with it.

How do electrical impulses travel through synapses? (3)

The neurotransmitter (chemical) is released into the synapse and diffuses across the gap from high concentration to low concentration.

How do electrical impulses travel through synapses? (4)

The neurotransmitter then binds to a complementary receptor on the cell membrane of neurone B (the post-synaptic neurone)

How do electrical impulses travel through synapses? (5)

If sufficient neurotransmitter bings to the receptor then an electrical impulse is induced in the neurone and the impulse continues to move along the dendrite of that neurone.

How do drugs such as paracetamol affect the reflex arc?

Drugs such as paracetamol can stop a neurotransmitter related to pain stimuli from binding with its complimentary receptor and so the pain signal (electrical impulse) does not carry on from the sensory neurone to the processing centre (brain and spinal cord) so the pain is not recognised.

At GCSE level, what do muscles always respond by doing?

Contracting or Relaxing

At GCSE level, what do ligaments always respond by doing?

Tightening and Slackening (Loosening)

What are the steps in a reflex arc?

stimulus, receptor, sensory neurone, synapse, relay neurone, synapse, motor neurone, effector (often a muscle), response

What are the ways in which nervous communication differs from hormonal communication?

Nervous communication is sent via electrical impulses, whereas hormonal communication is via chemical signals.

Nervous communication travels through neurones, whilst normal communication travels through blood.

Nervous communication is often faster and short lasting, however hormonal communication is often slow and long lasting.