Reflexes

Question 1

What s a reflex?

Answer 1

Reflex is the response to a peripheral stimulation that occurs without our consciousness. (a subconscious stimulus response)
It is an involuntary response and a type of protective mechanism

Question 2

Outline the reflex arc

Answer 2

A reflex arc is a neural pathway that mediates a reflex action. It has five components namely;
1. Receptor: This is the site of the stimulus
2. Afferent Nerve: These nerves transmits sensory impulses
3. Center: The center receives the sensory impulses and generates appropriate motor impulses. Processes information
4. Efferent nerve: These nerves Transmit motor impulses from the center to the effector organ
5. Effector organ: These are organs such as muscles or glands that respond to the stimulus

Question 3

How are reflexes classified?

Answer 3

1. Development includes whether the reflex is innate or is an acquired reflex.
2. Response includes the nature of resulting motor response whether the reflex is somatic or autonomic (visceral). Somatic is further categorized into deep and superficial Reflexes.
3. Complexity includes whether the reflexes are monosynaptic or polysynaptic.
4. Processing site includes where the information is being processed, whether it is the spinal cord or the brain

Question 4

Describe monosynaptic reflexes

Answer 4

Most rapid, simple reflex with a single synapse between the afferent and efferent neurons
e.g patellar reflex

Question 5

Describe polysynaptic reflexes

Answer 5

Produce a more complex response
Involves (1) interneurons which can be inhibitory or excitatory ; (2) distribution to more than one segment of the spinal cord ; (3) reciprocal inhibition

Question 6

Describe superficial reflexes

Answer 6

Superficial reflexes are reflexes which are elicited from the surface of the body.
These reflexes are motor responses to for example scraping of the skin.
These are initiated by stimulating appropriate receptors of the skin or mucous membranes.
They are usually multi-synaptic or poly-synaptic.

Question 7

Describe the types of superficial reflexes

Answer 7

(1) Corneal reflex : Touching cornea with cotton wisp = Closure of the eye (blinking)
(2) Conjunctival reflex : Touching conjunctiva with cotton wisp = Closure of the eye
(3) Nasal reflex (sneezing reflex) : Irritating the nasal mucosa with a cottin wasp = Sneezing
(4) Planter reflex : Stroking the sole = Planter flexion and adduction of toes

Question 8

Describe deep reflexes

Answer 8

Deep reflexes are elicited from deeper structurers beneath the skin.
-They are also known as tendon reflexes.
For example: For skeletal muscles to perform normally, proprioceptors (GTO) on tendons respond to the change in the force or tension developed in the skeletal muscle during contraction.
Stretch reflexes are initiated by muscle spindles and must maintain healthy muscle tone
Excited motor neurons of the spindle causing the muscle to contract. Afferent impulse from the spindle leads to inhibition of the antagonist

Question 9

Describe the types of deep reflexes

Answer 9

(1) Jaw jerk : Tapping the middle of the chin with slightly opened mouth = Closure of mouth.
(2) Bicep jerk : Trapping the biceps tendon = Flexion of forearm
(3) Triceps jerk : Trapping the triceps tendon = Extension of forearm
(4) Knee jerk or patellar tendon reflex : Trapping the patellar tendon = Extension of knee due to quadracips muscle
(5) Ankle jerk or achilles tendon reflex : Trapping the achilles tendon = Planter flexion of foot

Question 10

Describe how spinal injuries can impact reflexes

Answer 10

Below the damage level, reflexes may be unaffected or have minor effects. These reflexes may have normal or slightly decreased responses relative to pre-injury levels. Reflexes like the patellar reflex and the Achilles reflex may still be present and elicit-able.
Spinal shock can cause a temporary loss of reflexes at the injury level, resulting in diminished activity. As spinal shock subsides, reflexes may eventually return, although they may be altered or hyperactive due to disruptions in descending inhibitory circuits. Above the injury level, reflexes may become hyperactive or exaggerated due to loss of descending inhibitory control from higher centres in the central nervous system.
Upper motor neurons symptoms, such as hyper-reflexia and stiffness, can be seen in muscles innervated by spinal cord segments above the damage site
Autonomic Reflexes: Spinal cord injuries can also affect autonomic reflexes such as the bulbo-cavernosus reflex and the anal reflex, leading to disturbances in bowel, bladder, and sexual function