Did you ever go to a doctor and seen him tapping on your knee with a rubber mallet? Your leg kicks forward on its own. This is called knee jerk reflex. The tap makes your quadriceps muscle to contract and coordinates with the relaxation of the antagonistic flexor hamstring muscle to bring your lower leg forward. This is a reflex of proprioception, which helps maintain posture and balance.
Let us think of another example. When you fall, reflexes automatically command your hands and arms to reach out and break your fall. When you pull your hand away from something hot, that is a reflex.
Did you know that humans are born with most reflexes?
A reflex is an involuntary and nearly instantaneous movement in response to a stimulus.
What is a reflex arc?
The path taken by the nerve impulses in a reflex is called a reflex arc. This is from the stimulus to sensory neuron to motor neuron to reflex muscle movement.
What is a primitive reflex?
Primitive reflexes are involuntary motor responses that are present after birth in early child development and disappear as the child grows. If you put your finger into a baby’s hand, the baby automatically grips it. This is an example of a primitive reflex called the palmar reflex.
Types of reflex arcs:
Autonomic
Autonomic reflexes are unconscious motor reflexes relayed from the organs and glands to the central nervous system.
They are generally far less apparent than somatic reflexes, given the unconscious nature within which they manage vital internal functions.
Somatic
Somatic reflexes involve unconscious skeletal muscle motor responses.
Reflex arcs that contain only two neurons, a sensory and a motor neuron, are considered monosynaptic.
Most reflex arcs are polysynaptic including multiple interneurons or relay neurons that interface between the sensory and motor neurons in the reflex pathway.
Let us look at some of the examples
* Abdominal reflex is stim-ulated by stroking around the abdomen, which helps in determining the level of CNS (central nervous system) lesion.
* Cremastic reflex is elicited when the inner part of thigh is stroked in males. This helps in evaluation of acute scrotal pain and assessing for testicular torsion (associated with loss of reflex).
* Corneal reflex is elicited by gentle stroking on the cornea with a cotton swab. This reflex helps in knowing the damage to nerves.
* Biceps reflex is a jerking of the forearm when the biceps brachii tendon is struck with a tendon hammer
* Triceps reflex is a jerking of the forearm when the triceps tendon is hit with a tendon hammer,
* Brachioradialis reflex is a jerking of the forearm when the brachioradialis tendon is hit with a tendon hammer while the arm is resting
* Pupillary light reflex is a reduction of pupil size in response to light.
* Pupillary accommodation reflex is a reduction of pupil size in response to an object coming close to the eye
* Cough reflex is a rapid expulsion of air from the lungs after sudden opening of the glottis, and usually following irritation of the trachea.
* Babinski reflex is seen in infants up to one year of age and in older individuals with neurological damage. This reflex is in response to stroking the side of the foot resulting in a spreading of the toes and extension of the big toe.
Hyper reflexes
Hyperreflexia is defined as overactive or overresponsive reflexes. This can result in twitching or severe spasms. Hyperreflexia can be indicative of a motor neuron disease. They are also called exaggerated reflexes.
Dysfunctional reflexes
Dysfunctional reflexes could be a result of a trauma, an underlying disease, damage to the nerves, blockage of neural pathways, neurological disorder or may have congenital causes. This would need medical attention and it is very important to seek your doctor’s advice.
Athletes and reflexes
Studies show that athletes have a faster visual reaction and anticipation time response compared to non-athletes.
Reflexes and age
Reflexes do slow with age. Physical changes in nerve fibres slow the speed of conduction. The parts of the brain involved in motor control lose cells over time. But the effect of age on reflexes and reaction time varies greatly from person to person. You can slow down or even reverse the effects of ageing by staying physically active and doing regular exercises.
How can you improve your reflexes?
* Take up a sport like table tennis or badminton. Such sports must be played with rapid reflexes due to the small playing area, the size of the ball and the rapid movements involved to win the game.
* Getting regular exercise is directly linked to a faster reaction time.
* Make sure to get good sleep to prevent feeling sluggish. Ensure a balanced diet.
* Hydration is very important. Even just a couple of hours without water can significantly slow your reaction time.