reflex actions

reflex action

-a rapid, automatic, involuntary response to a stimulus

-does not involve conscious part of the brain

features of the reflex action that help organisms survive

-rapid

-involuntary [does not require complex decision-making]

-innate [no learning required]

examples of reflex test

-knee jerk reflex test

-blink reflex test

Knee-jerk reflex

-tapping the patellar tendon stretches the quadriceps muscle

-Stretch receptors detect this

-nerve impulse passes along sensory neurone to spinal cord

-the impulse is passed directly to a motor neurone

-the motor neurone carries impulse to the quadricep muscle [effector]

-the quadriceps contract, causing the lower leg to move forward

[no relay neurone used]

during knee-jerk reflex, what does multiple kicks and no response indicate?

multiple kicks indicate cerebellar disease

no response indicate damage to sensory or motor neurone

blink reflex test [does use relay neurone. if diagram in q shows relay neurone, mention it]

-cornea is stimulated by e.g. touch, bright light

-nerve impulse passes along sensory neurone to CNS

-Relay neurone passes impulse to motor neurone

-the motor neurone carries impulse to eyelid muscle [effector]

-eyelid muscle contracts, causing the eyelids to close

Describe the reflex response a person would make if an object touches their eye and explain the advantage of this response.

-rapidly blink

→protects eye from damage