reflex action Flashcards
what is a reflex action
a response to environmental stimulus, which is involuntary and doesnt require any processing by brain
why is it beneficial for the nervous pathway for reflex actions to be short
to ensure reflex is rapid
what are the three neurones involved in reflex actions
sensory
relay
motor
if a reflex enters the brain, but doesnt require brain processing to control the action, what is happening
the brain may be informed that the action is occuring
what is the aim of reflexes
Survival
- avoid danger, avoid damage, maintain balance
what is the blinking reflex
temporary closing of the eye to protect from damage
what are some examples of stimuli which stimulate the blinking reflex
foreign object touching ete
sudden bright light
loud sounds
sudden movement
what is the process of the corneal reflex
stimulus is detected by sensory receptor in the cornea, sensory neurone enters pons
synapse connects sensory neurone to relay neurone. which transmits action potential to the motor neurone, which passes out of brain to the facial/ eyelid muscles to stimulate blinking
the action potential from the sensory neurone is sent to the relay neurone, and where else
also sends to the myelinated neurones in the pons, which send action potentials to the sensory region in the celebral cortex to inform brain of this response
what does it mean if a reflex is overridden
inhibits the reflex, stops it from happening
how does the cerebral cortex override reflexes by conscious control
it can send inhibitory signals to the pons and prevent formation of an action potential
what does the optical reflex protect
protects the light sensitive cells of the retina from damage.
the knee jerk reflex is a spinal reflex what does this mean
the nervous pathway passes through the spinal cords not the brain
what is the difference between a cranial and spinal reflex
cranial- passes through the brain
spinal- passes through spinal CORD
Why do doctors use the knee jerk reflex
to test if the nervous system of a patient is working
what happens when you hit the knee cap with a specialised hammer
the leg will involuntarily straighten
what is the process of the knee jerk reflex
-stimuli- stretching of quadricep caused by pressure (pressure caused by hammer)
- stretch receptors (muscle spindles) detect stimuli
- sends action potential past the synapse in the spinal cord then to the motor neurone then to the effector (Quadricep muscle)
what is the effector in the knee jerk reflex
quadricep muscle
what receptor is used to detect stimuli in knee jerk reflex
stretch receptor/ muscle spindle-
sensitive to sudden muscle stretching
what are the neurones involved in the knee jerk reflex
sensory ]
motor
why is it beneficial for the absence of the relay neurone in the knee jerk reflex
nerve impulses are delayed by synapses. therefore it is rapid
describe the neurone pathway in the knee jerk reflex
sensory neurone
synapse in spinal cord
motor neurone
effector
why cant the knee jerk reflex be inhibited by the cerebral cortex inhibitory signals
due to the absence of the relay neurone, the reflex is to rapid. not enough delay for it to be inhibited by inhibitory action.
