Reflexes

What is a receptor?

Detects stimulus and creates an action potential in the sensory neurone

What do sensory neurones do?

Carried impulses to spinal cord

What do relay neurones do?

Connect the sensory neurones in to the motor neurone within the spinal cord or brain

What do motor neurones do?

Carried impulse to the effector to carry out the appropriate response

What is the spinal cord?

Column of nervous tissues running up the back. It is surrounded by the spine for protection. At interval along the spinal cord pairs of neurones emerge

What is the stimulus in the knee jerk reflex?

Stretching of the quadriceps muscle caused by pressure on the ligament by the hammer

What is the receptor in the knee jerk reflex?

Stretch receptors in the quadriceps muscle

What is the coordinator in the knee jerk reflex?

Spinal cord

What is the effector in the knee jerk reflex?

Quadriceps muscle

What is the response in the knee jerk reflex?

Contraction of quadriceps muscle

What is a spinal reflex?

Neural circuit only goes up to the spinal cord, not the brain

What is the 1st step of knee jerk reflex?

When the leg is tapped below the kneecap, it stretches the patellar tendon and acts as a stimulus. This initiates a reflex arc that caused the extensor muscle on top of the thigh to contract

What happens at the same time as step 1?

At the same time a relay neurone inhibits the motor neurone of the flexor muscle. causing it to relax. This contraction causes the leg to kick

What is the next step?

After the tap of a hammer, the leg is normally extended once and comes to rest.

What may the absence of this reflex suggest?

Nervous problems and multiple oscillations of the leg may be a sign of cerebullar disease

What ones this show about reflexes?

This show why reflexes are fast and automatic

Nerve impulses are delayed by synapses - signals only have to cross a single synapse which allows for a rapid response

What is the blinking reflex caused by?

Something travelling towards the eye, contacting cornea or drying the cornea nervous pathway of this reflex goes by the brain

What is the 1st step of the blinking reflex?

Irritation/drying of the cornea sends impulses down the trigeminal sensory nerve to the medulla of the brain, where it connects with other neurones to transmit the signal to the effector muscles

What is the 2nd step of the blinking reflex?

Relay neurones involved in transmission of impulses to the effectors in the lower eyelid

What is the 3rd step of the blinking reflex?

Effectors of blinking reflex include superior lavatories palpebrae muscle which lowers the upper eyelid, and the orbicullaris oculi muscle which pulls the eyelid inwards and helps to close them