Reflex Actions Flashcards
What is the knee jerk reflex?
A reflex action that straightens the leg when the tendon below the knee cap is tapped.
What is a reflex action?
A response that does not involve any processing by the brain.
They are responses to changes in the environment that do not involve any processing in the brain to coordinate the movement.
What do most reflex pathways consist of?
Sensory neurone to relay neurone to motor neurone
Why might a reflex action be used?
To get out of danger, to avoid damage to part of the body, or it may be used to maintain balance. They are used for survival reasons.
what is the blinking reflex?
Causes temporary closure to the eyelids to protect the eyes from damage.
What is a cranial reflex?
When the nervous pathway for the reflex passes through part of the brain.
What is it called when the receptor and effector are in the same place?
A reflex arc
Give examples of sudden changes in the environment for the blinking reflex.
A foreign object touching the eye (corneal reflex)
Sudden bright light (optical reflex)
Loud sounds
Sudden movements close to the eye
How does the corneal reflex work?
The reflex is mediated by a sensory neurone from the cornea, which enters the pons. A synapse connects the sensory neurone to the relay neurone, which passes the action potential to the motor neurone. The motor neurone passes back out of the brain to the facial muscles causing the eyelid to blink. It usually causes both eyes to blink even if only one has been effected.
Why is the corneal reflex very rapid?
It is a very short and direct pathway. It takes about 0.1 seconds.
How does the corneal reflex inform the brain that the action has taken place?
The sensory neurone passes the action potential to myelinated neurones in the pons. These myelinated neurones carry the action potential to the sensory region in the cerebral cortex, to inform the higher centres of the brain that the stimulus has occurred.
How can the inhibitory action potentials override the corneal reflex?
They can be overridden by conscious control due to the fact that it passes from the brain into the cerebral cortex informing it that it has occurred. The myelinated neurones in the cerebral cortex are much faster than the non-myelinated neurones in the corneal reflex. Therefore, the inhibitory action potentials can prevent the formation of an action potential in the motor neurone.
What does the optical reflex do?
It protects the light sensitive cells of the retina from damage.
How does the optical reflex protect the retina?
The stimulus is detected by the retina and the reflex is mediated by the optical centre in the cerebral cortex.
What kind of reflex is the knee jerk reaction?
A spinal reflex
