13.8 Reflexes Flashcards
What is a reflex action?
An involuntary response to a stimulus.
Describe the reflex arc.
Receptor- detects stimulus
Sensory neurone
Relay neurone- in spinal cord or brain
Motor neurone
Effector- usually a muscle
Appropriate response carried out
Is the knee-jerk reflex spinal or cranial?
Spinal
How is the knee jerk reaction stimulated?
The leg is tapped just below the patella, this stretches the patella tendon.
Describe the reflex arc for the knee jerk reaction.
The extensor muscle on top of the thigh contract.
At the same time, the relay neutrons inhibits the motor neurone of the flexor muscle.
This causes the leg to kick.
What does the absence of the knee-jerk reaction indicate?
Nervous problems
When tapped just below the patella, a patient’s leg kicks multiple times, what does this indicate?
A cerebellar disease.
What is the knee jerk reflex used to do?
To help maintain posture and balance.
Why do we have the blinking reflex?
Keeps cornea safe from damage due to foreign bodies.
What is the optical reflex?
Blinking due to over bright light.
Is the blinking reflex spinal or cranial?
Cranial
Describe the reflex arc for the blinking reflex.
Cornea irritated
Impulse sent along sensory neurone
Relay neurone
Motor neurone
Eyelids close
The blinking reflex is a consensual response, what does this mean?
Both the eyes close at the same time.
What does the presence of the blinking reflex in an unconscious patient indicate?
That the lower brain stem is functioning.
How can reaction time be measured?
Measuring how long it takes for a person to catch a falling object.
