The Nervous System and Responding to Stimuli and Reflexes

Question 1

How do organisms respond to their environment to survive?

Answer 1

-they respond to changes in their EXTERNAL environment eg by avoiding places that are too hot or too cold.

Question 2

What is the role of RECEPTORS and EFFECTORS?

Answer 2

RECEPTORS detect STIMULI and EFFECTORS produce a RESPONSE.

Question 3

What are RECEPTORS?

Answer 3

RECEPTORS in the sense organs are a group of CELLS that detect EXTERNAL STIMULI.

Question 4

Give 5 examples of sense organs.

Answer 4

Eyes, ears, nose, tongue and skin.

Question 5

Give an example of RECEPTOR cells and their function.

Answer 5

Rod and cone cells in the eye detect changes in light.

Question 6

Give an example of EFFECTOR cells.

Answer 6

They include muscle cells and cells found in glands eg the pancreas.

Question 7

Give an example of a response that is produced by EFFECTOR cells

Answer 7

EFFECTORS respond in different ways - muscle cells CONTRACT and glands SECRETE HORMONES.

Question 8

How do RECEPTORS communicate with EFFECTORS?

Answer 8

RECEPTORS communicate with EFFECTORS via the NERVOUS SYSTEM, the HORMONAL SYSTEM or sometimes both.

Question 9

What is the nervous system made up of?

Answer 9

neurones (nerve cells)

Question 10

What are the 3 main types of neurones?

Answer 10

Sensory, relay and motor neurones

Question 11

What does the central nervous system consist of?

Answer 11

BRAIN and SPINAL CORD only

Question 12

What do RECEPTORS do when they detect a stimulus?

Answer 12

They send electrical impulses along SENSORY NEURONES to the CNS

Question 13

What does the CNS do?

Answer 13

It’s job is to co ordinate responses.

Question 14

What do EFFECTORS do when they get a message from a MOTOR NEURONE?

Answer 14

They respond accordingly

Question 15

What do co ordinated responses always need?

Answer 15

STIMULUS, RECEPTOR and EFFECTOR

Question 16

How is the nervous system able to bring about very rapid responses

Answer 16

Because neurones transmit information using high speed electrical impulses

Question 17

What is the connection between two neurones called?

Answer 17

A SYNAPSE (a gap)

Question 18

How does a SYNAPSE work?

Answer 18

The nerve signal is transferred by CHEMICALS called NEUROTRANSMITTERS which diffuse across the gap. These CHEMICALS then set off a new ELECTRICAL signal in the next neurone

Question 19

Why do organisms respond to changes in their environment?

Answer 19

It increases their chance of survival

Question 20

What is a stimulus?

Answer 20

A change in the INTERNAL or EXTERNAL environment

Question 21

How are STIMULI detected?

Answer 21

By the RECEPTOR CELLS

Question 22

Give two types of EFFECTOR and how they respond

Answer 22

MUSCLE contracts or GLAND secretes a hormone

Question 23

What is the purpose of a reflex action?

Answer 23

They are automatic responses not a conscious decision. They reduce the chance of being injured

Question 24

Describe how a reflex arc works.

Answer 24

Candle burns finger, stimulation of the pain RECEPTOR,
Impulses travels along the SENSORY NEURONE, impulses are passed long a RELAY NEURONE, VIA a SYNAPSE, impulse sent along MOTOR NEURONE via a synapse, impulse reach muscle, it CONTRACTS, and moves hand away from candle.

Question 25

Why is the REFLEX ARC quicker acting than a normal response?

Answer 25

Because the message in the neurones goes through the spinal cord or the unconscious part of the brain and it’s not a conscious decision. This makes a much quicker response.