Reflexes Overview

Question 1

are automatic stimulus-response reactions. They involve a sequence of steps:

Answer 1

Reflexes

Question 2

detect a change in the environment

Answer 2

Receptors

Question 3

transmit this information to the central nervous system.

Answer 3

Sensory neurons

Question 4

processes the information.

Answer 4

The central nervous system

Question 5

send signals to effectors, such as skeletal muscle.

Answer 5

Motor neurons

Question 6

produce a response appropriate to the situation.

Answer 6

Effectors

Question 7

reflexes that cause muscle contraction after the muscle is stretched. These are local reflex arcs that are used for body posture and movement and do not rely on cerebral input for function.

Answer 7

Myotatic Reflex

Question 8

simple spinal reflex involving only two neurons.

A sensory axon synapses directly with a motor neuron, triggering muscle contraction.

This reflex helps maintain upright posture.

Answer 8

Myotatic Reflex

Question 9

Myotatic Reflex example

Answer 9

the knee-jerk reflex.
Striking the patellar ligament stretches the quadriceps muscle, stimulating sensory receptors

Question 10

A more complex reflex involving multiple neurons.

examples, miosis and consensual light reflex

Answer 10

Pupillary Light Reflex

Question 11

Light entering the eye causes the pupillary sphincter muscle in the iris to constrict, reducing the pupil’s diameter

Answer 11

miosis

Question 12

This reflex involves withdrawing a limb from a painful stimulus.

Stimulation of pain sensory neurons leads to stimulation of flexor muscles and reciprocal inhibition of extensor muscles.

Answer 12

Flexion Withdrawal Reflex

Question 13

In Flexion Withdrawal Reflex, the opposite limb reacts in an opposite manner to enhance postural support, which is known as the

Answer 13

crossed extension reflex.

Question 14

Voluntary reactions are more complex than reflexes and involve higher-level brain functions.

refers to the reaction time when there is only one stimulus and one response.

Answer 14

Reaction Time

Question 15

The main delay in reaction time occurs at the

Answer 15

synapses between neurons.

Question 16

Typical reaction times for college-age individuals:

Answer 16

Visual stimuli: ~190 ms
Auditory stimuli: ~150 ms
Touch: ~155 ms

Question 17

Some Factors Affecting Reaction Time

For both males and females, reaction time shortens from infancy into late
20s, then increases slowly until the 50s and 60s, and then ___________
as the person gets into his 70s and beyond.

Answer 17

lengthens faster

Question 18

Some Factors Affecting Reaction Time

Reaction time is fastest with an ________ level of arousal, and deteriorates when the subject is either too relaxed or too tense.

Answer 18

intermediate

Question 19

Some Factors Affecting Reaction Time

increase reaction time significantly, especially in younger individuals

Answer 19

Distractions

Question 20

Some Factors Affecting Reaction Time

which gender has a faster reaction time

Answer 20

males

Question 21

Some Factors Affecting Reaction Time

Practice at a task ________ reaction time

Answer 21

decreases

Question 22

Some Factors Affecting Reaction Time

When a volunteer makes an error (like pressing the button before thestimulus is presented), subsequent reaction times are

Answer 22

slower likely due to the subject being more cautious

Question 23

Some Factors Affecting Reaction Time

Shocking a subject when he reacts slowly does

Answer 23

shorten reaction time

Question 23

Some Factors Affecting Reaction Time

Reaction time deterioration due to fatigue is more marked when the task is __________ than when it is _________. Mental fatigue, especially ________, has the greatest effect.

Answer 23

complicated
simple

sleepiness

Question 24

Some Factors Affecting Reaction Time __________ tend to decrease reaction times to a point, but see arousal above. ____________often increase reaction times

Answer 24

Stimulants Depressants

Question 25

Some Factors Affecting Reaction Time Generally, reaction times are ___________ when the subject has been warned that a stimulus will arrive soon

Answer 25

faster

Question 26

are automatic, rapid responses to specific stimuli that occur without conscious thought, serving as the body's built-in defense mechanisms.

Answer 26

Reflexes

Question 26

is the interval between the presentation of a stimulus and the initiation of a response. It provides insights into the efficiency of neural processing and can vary among individuals and in different situations.

Answer 26

Reaction time

Question 27

pupillary dilatation is called

Answer 27

mydriasis

Question 27

which involves four neurons that connect the retina to the midbrain and then convey information back to the ciliary muscle. When light is focused upon the eye, the pupillary sphincter muscle in the iris constricts reducing the aperture (diameter) of the pupil

Answer 27

“direct light” reflex

Question 28

At the same time, the pupillary sphincter muscle of the other eye constricts too after “direct light” reflex

Answer 28

consensual light reflex

Question 29

is innervated by the dendrite of a sensory neuron whose cell body is in the dorsal root ganglion and whose axon enters the spinal cord where it synapses with the axon and the dendrite of the lower motor neuron (LMN) in the anterior horn

Answer 29

muscle spindle

Question 30

efferent limb of the arc consists of the

Answer 30

LMN, the muscle synapse, and the muscle fibers of the motor unit.

Question 31

When the descending motor pathway (the pyramidal tract) in the spinal cord is injured above the level of the reflex arc, normal cortical inhibition is lost, producing a

Answer 31

hyperactive or spastic reflex.

Question 32

These reflex arcs have receptor organs in the skin rather than in muscle fibers. Their adequate stimulus is stroking, scratching, or touching. If there is no response, a painful stimulus should be tried.

Answer 32

SUPERFICIAL (SKIN) REFLEXES

Question 33

The superficial reflexes are lost in disease of the

Answer 33

pyramidal tract

Question 34

Hyperactive, very brisk, rhythmic oscillations (clonus), this is abnormal and indicative of a disorder

Answer 34

4

Question 35

More brisk or active than normal, but not indicative of a disorder

Answer 35

3

Question 36

Normal, usual response

Answer 36

2

Question 37

Decreased, less active than normal

Answer 37

1

Question 38

No response

Answer 38

0

Question 39

The presence of an extensor plantar response is called

Answer 39

Babinski sign

Question 40

In disease of the pyramidal tract, this reflex (Babinski sign) results, with some or all of four components:

Answer 40

dorsiflexion of the great toe, fanning of all toes, dorsiflexion of the ankle, and flexion of the knee and thigh.