A2. Nervous Communication

Question 1

Receptors and effectors
Receptors detect ____________- they can be cells, or __________on cell surface membranes. There are loads of different types of receptors that detect different stimuli, e.g. ________________are a type of receptor that detect changes in blood pressure, but receptors are specific to one type of stimulus

Answer 1

Receptors detect stimuli-they can be cells, or proteins on cell surface membranes. There are loads of different types of receptors that detect different stimuli, e.g. baroreceptors are a type of receptor that detect changes in blood pressure, but receptors are specific to one type of stimulus

Question 2

Effectors are cells that bring about a response to a stimulus, to produce an effect. Effectors include _________cells and cells found in _______, e.g. the pancreas. Receptors communicate with effectors via the nervous system or the hormonal system, or sometimes using both.

Answer 2

Effectors are cells that bring about a response to a stimulus, to produce an effect. Effectors include muscle cells and cells found in glands, e.g. the pancreas. Receptors communicate with effectors via the nervous system or the hormonal system, or sometimes using both.

Question 3

Sensory neurones

Answer 3

transmit electrical impulses from receptors to the central nervous system (CNS)—the brain and spinal cord.

Question 4

Motor neurones

Answer 4

transmit electrical impulses from the CNS to effectors.

Question 5

Relay neurones

Answer 5

(also called intermediate neurones, interneurones or association neurones) transmit electrical impulses between sensory neurones and motor neurones.

Question 6

Nervous Communication
A ___________ is detected by __________cells and an electrical impulse is sent along a sensory neurone. When an electrical impulse reaches the end of a neurone chemicals called ____________________take the information across the gap (called a __________) to the next neurone, where another electrical impulse is generated. The CNS (the coordinator) processes the information and sends impulses along ________neurones to an effector

Answer 6

A stimulus is detected by receptor cells and an electrical impulse is sent along a sensory neurone. When an electrical impulse reaches the end of a neurone chemicals called neurotransmitters take the information across the gap (called a synapse) to the next neurone, where another electrical impulse is generated. The CNS (the coordinator) processes the information and sends impulses along motor neurones to an effector

Question 7

Figure 1: The pathway of nervous communication

Answer 7

Question 8

Tip: The electrical impulses sent along neurones are also called nerve impulses or ________ ___________

Answer 8

Tip: The electrical impulses sent along neurones are also called nerve impulses or action potentials

Question 9

The nervous response
When an electrical impulse reaches the end of a neurone, chemical messengers called _________________are secreted directly onto cells (e.g. muscle cells)—so the nervous response is localised. Neurotransmitters are quickly _________once they’ve done their job, so the response is _______-lived. Electrical impulses are really fast, so the response is usually rapid -this allows animals to react quickly to _________.

Answer 9

When an electrical impulse reaches the end of a neurone, chemical messengers called neurotransmitters are secreted directly onto cells (e.g. muscle cells)—so the nervous response is localised. Neurotransmitters are quickly removed once they’ve done their job, so the response is short-lived. Electrical impulses are really fast, so the response is usually rapid -this allows animals to react quickly to stimuli.

Question 10

Tip: The cells that neurotransmitters are released onto are called ________cells-they have specific __________for the neurotransmitters

Answer 10

Tip: The cells that neurotransmitters are released onto are called target cells-they have specific receptors for the neurotransmitters

Question 11

Simple reflexes
A simple reflex is a ______, _____________response to a stimulus. The pathway of communication goes through the _______cord but not through conscious parts of the brain, so the response happens ______________. Because you don’t have to spend time deciding how to respond, information travels really fast from receptors to effectors.
Simple reflexes are _____________ - they help organisms to avoid damage to the body because the response happens so quickly.

Answer 11

A simple reflex is a rapid, involuntary response to a stimulus. The pathway of communication goes through the spinal cord but not through conscious parts of the brain, so the response happens automatically. Because you don’t have to spend time deciding how to respond, information travels really fast from receptors to effectors.
Simple reflexes are protective - they help organisms to avoid damage to the body because the response happens so quickly.

Question 12

The reflex arc
The pathway of neurones linking receptors to effectors in a simple reflex is called a reflex arc. Three neurones are involved - a __________neurone, a _______neurone and a ________neurone

Answer 12

The pathway of neurones linking receptors to effectors in a simple reflex is called a reflex arc. Three neurones are involved - a sensory neurone, a relay neurone and a motor neurone

Question 13

Figure 2: The pathway of nervous communication in a simple reflex arc.

Answer 13

Question 14

A real-life example of a simple reflex is the hand-withdrawal response
to heat
___________- you touch a hot surface.
______________-thermoreceptors (heat receptors) in your skin detect the heat stimulus. A sensory neurone carries the impulse to the CNS.
____-a relay neurone in your spinal cord carries the impulse to a motor neurone.
___________- the motor neurone carries the impulse to muscle cells in your biceps.
____________- your biceps muscle contracts to pull your hand away from the heat source and stop your hand from being damaged.

Answer 14

Stimulus - you touch a hot surface.
Receptors -thermoreceptors (heat receptors) in your skin detect the heat stimulus. A sensory neurone carries the impulse to the CNS.
CNS-a relay neurone in your spinal cord carries the impulse to a motor neurone.
Effectors - the motor neurone carries the impulse to muscle cells in your biceps.
Response - your biceps muscle contracts to pull your hand away from the heat source and stop your hand from being damaged.