13.8 Reflexes

Question 1

What is a reflex action?

Answer 1

involuntary response

to a sensory stimulus

Question 2

Outline the steps of a reflex arc:

Answer 2

1. RECEPTOR - detects stimulus & induces action potential in sensory neurone
2. SENSORY NEURONE - carries impulse to spinal cord
3. RELAY NEURONE - connects sensory neurone to motor neurone in brain/spinal cord
   
   1. MOTOR NEURONE - carries impulse to effector.

Question 3

What is a spinal reflex?

Answer 3

action in which the CNS part of the neural circuit

is in the spinal cord & not the brain

Question 4

What is a cranial reflex?

Answer 4

action in which the CNS part of the neural circuit

is in the brain & not the spinal cord

Question 5

What type of reflex is the knee-jerk reflex?

Answer 5

spinal reflex

Question 6

What type of reflex is the blinking reflex?

Answer 6

cranial reflex

Question 7

Outline the series of steps which occur to initiate the knee-jerk reflex:

Answer 7

1. tapped below kneecap
2. stimulus - stretching of tendon, causes muscle to contract.
3. induces action potential in sensory neurone
4. carried to relay neurone in spinal cord
5. relay neurone inhibits motor neurone of flexor muscle, causing relaxation.

Question 8

How do reflexes increase the chances of survival?

Answer 8

• INVOLUNTARY
  
  • decision-making regions of brain are not involved
  • prevents brain from being overloaded with information
• NOT LEARNT
  
  • provide immediate protection
• FAST
  
  • short reflex arc, only 2 synapses which are the slowest step
• reflexes include everyday functions e.g digestion & balance