B9 Coordination and response - 1 & 2

Question 1

What is a nerve impulse?

Answer 1

A nerve impulse (information) is an electrical signal that passes along nerve cells called neurones. -

Question 2

What does the human nervous system consist of?

Answer 2

The human nervous system consists of the:
-central nervous system (CNS) - brain and spinal cord
-peripheral nervous system (PNS) - all of the nerves in our body.

Question 3

What does the human nervous system allow us to do?

Answer 3

It allows us to:
-Make sense of our surroundings and respond to them.
-Coordinate and regulate body functions.

Question 4

What is a nerve?

Answer 4

A nerve is a bundle of neurones.

Question 5

What do nerves do?

Answer 5

Nerves send electrical impulses around the body. They receive information from receptors and send instructions out to effectors.

Question 6

What is the central nervous system?

Answer 6

The central nervous system is the brain and spinal cord and acts as a coordinator for the rest of the nervous system.

Question 7

What is the peripheral nervous system?

Answer 7

The peripheral nerve system are the nerves with sensory and motor neurones.

Question 8

What is a voluntary response?

Answer 8

A voluntary response is one where you make a conscious decision to carry out a particular action therefore it starts with your brain.
-Often take longer as we consider what the consequences might be before doing it.

Question 9

What is an involuntary (or reflex) response?

Answer 9

An involuntary (or reflex) response does not involve the brain as the coordinator of the reaction and you are not aware you have completed it until after you have carried it out.
-Tend to be rapid and an automatic response to a stimulus.

Question 10

What are the three main types of neurones?

Answer 10

Sensory, relay
and motor neurones.

Question 11

What is the function of sensory neurones?

Answer 11

Sensory neurones carry impulses from sense organs to the CNS.

Question 12

What is the function of relay neurones?

Answer 12

Relay neurones are found inside the CNS and connect sensory and motor neurones.

Question 13

What is the function of motor neurones?

Answer 13

Motor neurones carry impulses from the CNS to the effectors.

Question 14

What does a sensory neurone look like?

Answer 14

A sensory neurone is very long and has a cell body branching off in the middle of the axon.

Question 15

What does a relay neurone look like?

Answer 15

A relay neurone is short and has a small cell body at one end with MANY dendrites bracing off it.

Question 16

What does a motor neurone look like?

Answer 16

A motor neurone is long and has a large cell body at one end with long dendrites branching off.

Question 17

Why is a reflex response so rapid?

Answer 17

A reflex response does not involve the brain and is therefore quicker than any other type of nervous response. This helps to minimise the damage to the body.

Question 18

What is the reflex arc?

Answer 18

The reflex arc is the sequence of neurones that the impulse passes along in order to trigger the reflex response.

Question 19

What is the reflex arc sequence?

Answer 19

Stimulus => Receptor => Sensory neurone => Relay neurone => Motor neurone => Effector => Response.

Question 20

What is a reflex action?

Answer 20

A reflex action is a means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands).

Question 21

What is the stimulus?

Answer 21

The stimulus is the trigger of the reflex. - touch, light or sound.

Question 22

What is the receptor?

Answer 22

The receptors are a group of specialised cells that detect a change in the environment and stimulate electrical impulses in response. Once the receptor cell in the sense organ has been stimulated, it generates an electrical impulse which is passed on to a sensory neurone and so on.

Question 23

What is the effector?

Answer 23

The effector is what carries out the response. It may be a muscle or gland.

Question 24

What is the eye?

Answer 24

The eye is a sense organ containing receptor cells that are sensitive to light (rod) and colour (cone).

Question 25

What is the function of the cornea?

Answer 25

The corner is the transparent lens that refracts (bends) light as it enters the ye.

Question 26

What is the function of the iris?

Answer 26

The iris controls how much light enters the pupil.

Question 27

What is the function of the lens?

Answer 27

The lens is the transparent disc that can change shape to focus light onto the retina.

Question 27

What is the function of the retina?

Answer 27

The retina contains light receptor cells - rods (detect light intensity) and cones (detect colour).

Question 28

What is the function of the optic nerve?

Answer 28

The optic nerve is a sensory neurone that carries impulses between the eye and brain.

Question 29

What is the pupil reflex?

Answer 29

The pupil reflex is a mechanism that allows control over the amount of light entering the eye in different environments.

Question 30

What happens to the pupil in dim light?

Answer 30

In dim light, the pupil dilates (becomes larger) to allow more light to enter the ye to improve vision.

Question 31

What happens to the pupil in bright light?

Answer 31

In bright light, the pupil constricts (gets smaller) to allow less light to enter the eye to protect the retina from damage.

Question 32

What are antagonistic muscles?

Answer 32

Antagonistic muscles are two muscle that work together to achieve movement in two directions. This is necessary because muscles can only contract and relax, not push.

Question 33

What are the antagonistic muscles in the iris called?

Answer 33

The antagonistic muscles in the iris are called radial muscles and circular muscles. When one set of muscles contracts, the other relaxes.

Question 34

What happens to the antagonistic muscles when it is dark? - What causes the pupil to dilate?

Answer 34

When it is dark and the pupil dilates (larger), this is caused by the radial muscles contracting and the circular muscles relaxing. This allows more light to enter to improve vision.

Question 35

What happens to the antagonistic muscles when it is light? - What causes the pupil to constrict?

Answer 35

When it is light and the pupil constricts (smaller), this is caused by the circular muscles contracting and the radial muscles relaxing. This prevents damage to the retina.

Question 36

What is accommodation?

Answer 36

Accommodation allows the eye to focus on objects that are chose or far away from the eye.

Question 37

How does the eye achieve accommodation?

Answer 37

The eye achieves accommodation by changing the shape of the lens.

Question 38

How can the shape of the lens change?

Answer 38

The lens is elastic and its shape can be changed when the suspensory ligaments attached to it become tight or loose.

Question 39

What are the changes of the lens brought about by?

Answer 39

The changes are Brough about by the contraction or relaxation of the ciliary muscles.

Question 40

What happens when an object is close up?

Answer 40

When an object is close up:
-The ciliary muscles contract
-This causes the suspensory ligaments to loosen.
-This stops the suspensory ligaments from pulling on the lens, which allows the lens to become fatter.
-Light is refracted more.

Question 41

What happens when an object is far away?

Answer 41

When an object is far away:
-The ciliary muscles relax.
-This causes the suspensory ligaments to tighten.
-The suspensory ligaments pull on the lens, causing it to become thinner.
-Light is refracted less.

Question 42

What happens to the light entering the eye? - during accommodation.

Answer 42

The light entering the eye is refracted by the lens so it focuses correctly on the rods and cone cells of the retina. However, light needs to be refracted differently according to where it has entered the eye - from what location such as close up or far away.

Question 43

What is accommodation controlled by?

Answer 43

Accommodation is controlled by the ciliary muscles and suspensory ligaments.