nervous system

Question 1

What do animals and plants need to respond to?

Answer 1

Changes in their internal and external environment

Examples include changes in temperature or pH.

Question 2

What are the two communication systems in mammals that transfer information for homeostasis?

Answer 2

• Nervous system
• Endocrine system

Question 3

Which parts of the brain are involved in maintaining homeostasis?

Answer 3

Brain stem and spinal cord

Question 4

What are the components required for a coordinated response?

Answer 4

• A stimulus
• A receptor
• A coordination centre
• An effector

Question 5

What is the speed of information transmission through the nervous system?

Answer 5

Up to 100 metres per second

Question 6

compare nervous and endocrine system

Answer 6

Question 7

What is the structure of the human nervous system?

Answer 7

• Central nervous system (CNS) - brain and spinal cord
• Peripheral nervous system (PNS) - all of the nerves in the body

Question 8

What is the pathway through the nervous system summarized as?

Answer 8

Stimulus → sensory neurone → relay neurone → motor neurone → effector → response

Question 9

What occurs at a synapse?

Answer 9

Neurotransmitters transfer signals between neurones.

Question 10

What is the synaptic cleft?

Answer 10

The small gap between two neurones at a synapse.

Question 11

What are neurotransmitters?

Answer 11

Chemical signalling molecules used to transfer the signal between neurones at a synapse.

Question 12

What does a reflex response involve?

Answer 12

It does not involve the conscious part of the brain.

Question 13

What is a reflex arc?

Answer 13

The pathway of a reflex response taken by electrical impulses as they travel along neurones.

Question 14

What is the role of the retina in the eye?

Answer 14

It contains receptor cells that detect light.

Question 15

What are the two types of receptor cells in the retina?

Answer 15

• Rods (sensitive to light)
• Cones (detect colour)

Question 16

What is the function of ciliary muscles?

Answer 16

To change the shape of the lens for focusing.

Question 17

What happens to the lens when an object is close up?

Answer 17

Ciliary muscles contract, suspensory ligaments loosen, and the lens becomes fatter.

Question 18

What happens to the pupil in dim light?

Answer 18

The pupil dilates (widens).

Question 19

What is the pupil reflex in bright light?

Answer 19

The pupil constricts (narrows).

Question 20

What is the function of the optic nerve?

Answer 20

It carries impulses between the eye and the brain.

Question 21

What is the central nervous system linked to?

Answer 21

It is linked to the peripheral nervous system.

The central nervous system (CNS) consists of the brain and spinal cord.

Question 22

What does the central nervous system consist of?

Answer 22

It contains all the nerves in the body.

Nerves are made up of long chains of neurones.

Question 23

What are the three types of neurones?

Answer 23

• Sensory
• Relay
• Motor

Question 24

How does the nervous system work to carry out a response?

Answer 24

A stimulus is received by sensory neurones. The sensory neurone produces an electrical signal which travels to the co-ordinator. The electrical impulse is transferred to a relay neurone, which links to a motor neurone, leading to the effector.

This describes the pathway for an involuntary coordinated response.

Question 25

Why are neurotransmitters needed?

Answer 25

Neurones do not come into direct contact; the junction is called a synapse. The electrical impulse is converted into a chemical messenger called a neurotransmitter to cross the gap. ## Footnote This process is crucial for communication between neurones.

Question 26

How do electrical impulses pass from neurone to neurone?

Answer 26

An electrical impulse passes down the axon, triggering neurotransmitter release. They diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane to generate a new electrical impulse. ## Footnote Receptors have a complementary shape to neurotransmitters, which is exploited by drugs.

Question 27

What is the cornea and what is its function?

Answer 27

The cornea is a transparent lens that guards the eyes and refracts light as it enters the eye.

Question 28

What is the iris and what is its function?

Answer 28

The iris is the coloured part of the eyeball that controls the shape of the pupil to regulate light entry.

Question 29

What is the lens and what is its function?

Answer 29

The lens is a transparent shield that changes shape to focus light onto the retina, creating a sharper image. ## Footnote The ciliary muscle changes the shape of the lens and is connected by suspensory ligaments.

Question 30

What is the retina and what is its function?

Answer 30

The retina is a thin layer of tissue at the back of the eye containing receptor cells. Cone cells detect colour and rod cells detect light intensity. ## Footnote The fovea is the part of the retina with the highest density of receptor cells.

Question 31

What is the optic nerve and what is its function?

Answer 31

A sensory neurone that carries electrical impulses stimulated by light to the brain.

Question 32

What is the pupil and what is its function?

Answer 32

A hole in the iris that lets light in.

Question 33

How does the eye change when focusing on objects which are close up?

Answer 33

The ciliary muscles contract, suspensory ligaments loosen, and the lens becomes fatter/thicker to refract more light.

Question 34

How does the eye change when focusing on objects which are far away?

Answer 34

The ciliary muscles relax, suspensory ligaments tighten, and the lens becomes thinner to refract less light.

Question 35

How does the eye change when we are in a low-light environment?

Answer 35

Photoreceptors detect the change. Radial muscles contract, circular muscles relax, and the pupil dilates to allow more light in.

Question 36

How does the eye change when we are in a light-abundant environment?

Answer 36

Photoreceptors detect the change. Radial muscles relax, circular muscles contract, and the pupil constricts to reduce light entry.

Question 37

What are the four things which a co-ordinated response requires?

Answer 37

Coorindated responses can be to maintain homeostasis or to voluntarily coordinate a response such as moving a A stimulus (e.g. change in body temperature) A receptor (e.g. receptor cells) A co-ordination centre (e.g. brain or spinal chord which receives and processes information from receptors An effector (e.g. muscle shivering) which brings about the response