14.3- A REFLEX ARC

Question 1

What is the simplest type of nervous response to a stimulus?

Answer 1

reflex arc

Question 2

What are the two major divisions of the nervous system?

Answer 2

central nervous system (CNS)

peripheral nervous system (PNS)

Question 3

What is the central nervous system made up of?

Answer 3

brain + spinal cord

Question 4

What is the peripheral nervous system made up of?

Answer 4

pairs if nerves that originate from either brain or spinal cord

Question 5

What is the peripheral nervous system divided into? (2)

Answer 5

sensory neurones

motor neurones

Question 6

What do sensory neurones do?

Answer 6

carry nerve impulses (electrical signals) from receptors towards CNS

Question 7

What do motor neurones do?

Answer 7

carry nerve impulses away from CNS to effectors

Question 8

How can the motor nervous system be further subdivided? (2)

Answer 8

voluntary nervous system

autonomic nervous system

Question 9

What does the voluntary nervous system do?

Answer 9

carries nerve impulses to body muscles + under voluntary (conscious) control

Question 10

What does the autonomic nervous system do?

Answer 10

carries nerve impulses to glands, smooth muscle + cardiac muscle + not under voluntary control, it’s involuntary (subconscious)

Question 11

What is the spinal cord?

Answer 11

column of nervous tissue that runs along back + lies inside vertebral column for protection

Question 12

How are reflex actions described to be?

Answer 12

rapid, short-lived, localised + totally involuntary

Question 13

What is the pathway of neurones involved in a reflex known as?

Answer 13

reflex arc

Question 14

How many neurones do reflex arcs involve?

Answer 14

3 neurones

Question 15

Where is one of the neurones from the reflex arc and so what is this type of reflex called?

Answer 15

in spinal cord + so this type of reflex also called spinal reflex

Question 16

Main stages of spinal reflex arc:

Answer 16

stimulus -> receptor -> sensory neurone -> coordinator -> motor neurone -> effector -> response

Question 17

Why reflex actions important- involuntary

Answer 17

involuntary + so don’t require decision-making power of brain, so leaving it free to carry out more complex responses

some impulses nevertheless sent to brain, so it’s informed of what’s happening + can sometimes override reflex if necessary

Question 18

Why reflex actions important- protection

Answer 18

protect body from harm + don’t have to be learnt

Question 19

Why reflex actions important- they’re fast

Answer 19

fast as neurone pathway short with very few, typically one or two, synapses where neurones communicate with each other
important in withdrawal reflexes

Question 20

Why reflex actions important- absence of decision-making process

Answer 20

action rapid