Reflex physiology and reaction time - Lab quiz 1

What are somatic reflexes?

skeletal muscle contractions

When testing the patellar reflex, what should occur?

Knee extension

When counting backward while testing for the patellar reflex, does the reflex increase or decrease in amplitude?

Increase reflex amplitude

With the increase in reflex amplitude for the patellar reflex, is this effect caused by an increase or decrease in cortical inhibition?

Decrease in cortical inhibition

When testing the patellar reflex with the Jendrassik maneuver (clenching fist and pulling arms apart), does the reflex increase or decrease in amplitude?

Increase in reflex amplitude

With the increase in reflex amplitude (Jendrassik maneuver) when testing for the patellar reflex, what caused this effect, an increase or decrease in cortical facilitation (excitation)?

Increase in cortical facilitation

When tapping the Achilles tendon on the back of the ankle using the reflex hammer. What ankle motion occurs?

Ankle Plantar flexion

When testing the biceps brachii tendon reflex. What elbow or forearm motion occurs?

-Elbow flexion

-Forearm supination

When testing the triceps brachii tendon reflex. What elbow motion occurs?

Elbow extension

Testing these reflexes is a rapid way to assess the....

function of the spinal cord

Babinski reflex is an example of a...

superficial cord reflex

Superficial reflexes are initiated by...

stimuli to the skin or mucous membrane

What is the normal negative Babinski response?

flexion of the toes, especially the large toe

What is the abnormal positive Babinski response?

extension of the big toe, and flaring of the other toes

When do you get the abnormal positive Babinski response?

-newborn (whose motor pathways are incompletely myelinated)

-someone with damage to the corticospinal tract

Why might one do the Babinski test in a well-child checkup?

To check for the completion of myelination

Why might one do the Babinski test in an adult neurological checkup?

to check for damage or disease in the central nervous system, specifically the corticospinal tract

What type of reflex is the glabellar-blink reflex

superficial somatic reflex

What is the glabellar-blink reflex mediated through...

the cranial nerves and brainstems rather than through the spinal nerves and spinal cord

Absence of a blink reflex is an ominous sign and usually indicates...

compression of the brainstem from a tumor or trauma

What is the response of tapping the forehead just above each eye?

Eyes should blink

What is the purpose or function of the blink reflex?

For protection

Reflex is mediated through two cranial nerves. Sensory input utilizes the major sensory nerve of the face, which is ________ nerve, while the outer motor output is carried by the ______nerve.

1. CN V - Trigeminal

2. CN VII - Facial nerve

When briefly shining a light into a person's left eye only. What happens to the size of the left pupil?

Constricts

What happens to the size of the right pupil while shining the light into the left pupil?

Constricts

What can you say about the pathways involved if you see this type of response (pupillary light reflex)?

Consensual reflex: The pupil of the other eye shrinks at the same time, even though no light is shining directly into it.

What is the function of the pupillary light reflex?

Protecting the retina from too much light

What cranial nerve controls this motor function (pupillary light reflex)?

CN III - Oculomotor

When testing the pupillary accommodation reflex, having a person focus on a pen close to their face, what is the response?

-Pupil constriction

-Eyes converge

-Lens becomes short and fat

When testing the ciliospinal reflex, stroking the skin on the left side of the back of the neck at the hairline, what is the response?

-Pupil dilation ipsilateral (same side)

-eyes diverge to normal

-the lens becomes long and flat

Pupillary constriction gives less visual information and is used for close vision. Constriction is mediated by the ________ division of the autonomic nervous system while pupillary dilation is mediated by the ________ division of the autonomic system

1. parasympathetic

2. sympathetic

What takes longer, reflexes or reactions?

Reactions

Based on the average responses across both subjects, which mode of presentation resulted in shorter reaction time: Random interval or Fixed interval?

Fixed interval

Why was the fixed interval faster than the random interval?

We are able to anticipate when the next sound will come

Why do we get faster at reacting to fixed intervals from the first sound to the last sound?

We are able to practice and train our thumbs to get faster.

Why does using your dominant hand result in a quicker reaction time?

Frequent use of dominant builds stronger and more efficient neural pathways

What is faster, reflexive or voluntary movements?

Reflexive

When reaction times to visual and auditory stimuli are measured repeatedly, the response to an auditory stimulus is faster than the response to a visual stimulus. How might you explain this difference, neurologically?

The number of synapses is fewer. More synapses result in longer times.