Chapter 5 - Reflexes

Question 1

The pathway of a reflex action through the nervous system is called the…

Answer 1

• reflex arc

Question 2

Match these keywords from start to finish to show what the pathway is:

• receptor
• effector(muscle)
• relay neuron in CNS
• motor neuron
• sensory neuron
• stimulus

Answer 2

Stimulus –> Receptor –> Sensory neuron –> Relay neuron in CNS –> Motor neuron –> effector(muscle)

1) Stimulus
2) Receptor
3) Sensory neuron
4) Relay neuron in CNS
5) Motor neuron
6) Effector(muscle)

Question 3

What is a simple reflex?

Answer 3

• Simple reflexes require no learning and happen from birth (they are automatic reflexes)

Question 4

Reflexes enable us to respond quickly to stimuli that could harm us. Give examples of simple reflexes in humans

Answer 4

• dropping a hot object, the knee jerk reflex, the pupil reflex (when a bright light is shone into your eye the pupil gets smaller)
• when a baby is born, newborn reflexes, e.g. stepping (taking steps when a baby is held under arms, with head supported), grasping (when a finger is placed into the baby’s palm), sucking (when a nipple or finger is placed in a baby’s mouth)

Question 5

Why are responses rapid?

Answer 5

-Responses are rapid because they use fixed pathways that do not involve the brain making a conscious decision (relay neurons are in the CNS, but the brain is not involved at all if the stimulus is below the neck)

Question 6

Relay neurons in the CNS connect with other neurons that run to the brain, so we:

Answer 6

• 1) know what’s happened after the reflex has occurred
• 2) can override an action, e.g. keeping hold of a hot object when you’d rather not drop it (the brain then sends a message to motor neurons, which changes the response of the muscles in your hand, so you keep hold of the object)

Question 7

What is a reflex?

Answer 7

A reflex is a simple response to a stimulus, e.g. removing your foot automatically if you step on a sharp object or a hot one