LAB EXAM: Human Sensory Physiology

Question 1

____ provide input to the brain on the degree to which muscles are contracted, the amount of TENSION on the tendons, and the positions of hte joints.

Answer 1

proprioceptors

Question 2

Muscle tone is large extensor muscles and trunk postural muscles is continuously regulated by ____ ____.

Answer 2

stretch reflexes and propriocepetion

Question 3

_____ also allow weight discrimination.

Answer 3

proprioceptors

Question 4

a large amount of sensory receptors are located in the ___.

Answer 4

eyes

Question 5

sense that takes up the most cortical space

Answer 5

vision

Question 6

light is refracted by the ___ and ___ of the eye

Answer 6

lens and cornea

Question 7

process by which the lens becomes more curved in order to cause greater refraction of the light rays

Answer 7

accomodation.

Question 8

two types of photo receptors

Answer 8

rods and cones

Question 9

when testing the patellar reflex, contraction of the ___ muscle occurs because the ___ nerve is stimulated

Answer 9

when testing the patellar reflex, contraction of the QUADRICEP muscle occurs because the SCIATIC nerve is stimulated

Question 10

what do you expect to happen when the subject’s attention is diverted away from watching the reflex happening?

Answer 10

a higher muscle jerk occurs when the subject is not focused on the reflex, resulting in less cerebral inhibition

Question 11

a reflex caused by tapping a tendon may be regarded as resulting in a sudden increase in the ____ ____

Answer 11

muscle tonus

Question 12

what is muscle tonus

Answer 12

continuous and passive partial contraction of the muscles, or the muscle’s resistance to passive stretch during resting state.

Question 13

why can distraction cause the magnification of a reflex

Answer 13

because the cerebrum is no longer inhibiting the reflex. when focused on the reflex, the subjects brain is paying attention to inputs that may be happening to the reflex region, resulting in cognitive attempts to decrease the sensitivity to that area.

Question 14

in order to elicit a bicep reflex, you tap the bicep tendon in the ___ ___. If the reflex is normal, the bicep twitch is due to stimulation of the _____ nerve.

Answer 14

in order to elicit a bicep reflex, you tap the bicep tendon in the ANTECUBITAL FOSSA. If the reflex is normal, the bicep twitch is due to stimulation of the MUSCULOCUTANEOUS (stemming from C5 and C6) nerve.

Question 15

A tricep is elicit by stimulating the ___ nerve.

Answer 15

radial

Question 16

What effect would destruction of the ventral horn cells have on the patellar reflex?

Answer 16

motor neurons, which are responsible for the contraction of the quad muscles, are found to ORIGINATE in the ventral horn of the spinal cord. Axons of the motor neurons travel through the ventral nerve root tof the spinal cord to the effector muscle it innervates. The axon is relatively long because it needs to reach muscles in the periphery of the body.

If the ventral horn cells are damaged, it is likely that the motor neurons, but NOT the afferent sensory neurons which enter through the dorsal root horn, would be compromised. Therefore, it may be possible that the muscle spindle receptors on the afferent neuron would detect a stretch change in the quad muscle, but because the ventral root horn is destroyed, the sensory neuron could not convey the response to the motor neuron.

Because destruction of the ventral horn cells results in destruction of efferent motor neurons, no physical reflexive response could be intitiated. Thus, in a person with poliomyeltis, the patellar reflex would most likely not be seen.

Question 17

Does the magnitude of the reflex vary directly or indirectly as the degree of background tonus when the block of styrofoam is used?

Answer 17

Although it varies, most individuals find that the background tension in their muscle has a direct effect on the magnitude of their reflex.

Reflexes should be EXAGGERATED in an excitable state, and minimized in a relaxed state. There is a magnified reflex response in hysteria (ex/ mass strength when trying to lift a car off your child)

Many people find that the threshold for a knee jerk is higher after physically working.

Question 18

Usually, the ____ the stimulus and the longer its ____ on the receptors, the longer the after discharge.

Answer 18

Usually, the stronger the stimulus and the longer its action on the receptors, the longer the afterdischarge.

Question 19

adaptation

Answer 19

receptor adjustment in the PNS

Question 20

habituation

Answer 20

modification in synaptic effectiveness in the CNS

Question 21

what is the normal response to plantar flexion?

Answer 21

associated with a downward movement of the toes and withdrawal of the foot by the nervous system.

Question 22

normally, plantar flexion results in the downward movement of the toe. What is it called with there is an upward movement of the big toe and the splaying of the other toes?

Answer 22

babinsky sign

Question 23

Is the babinski sign normal in adults? What happens in adults that elicit this sign?

Answer 23

babinski sign is not normal in adults. it indicates that there is a disease in the pyramidal system of the central nervous system.

Question 24

Is swallowing under concious control? Where are the receptors that initiate the swallowing reflex located

Answer 24

The act of swallowing has voluntary and involuntary components. The preparatory/oral phase (USING YOUR TONGUE TO PUSH FOOD TO THE BACK OF THE THROAT) is voluntary, whereas the pharyngeal and esophageal phases are mediated by an involuntary reflex called the swallowing reflex

The pressure of the bolus in the pharynx stimulates PHARYNGEAL pressure receptors, which send afferent impulses to the swallowing center located in the MEDULLA. This center then reflexly activates, in the appropriate sequence, the muscles that are involved in swallowing.

The ability to swallow is both volunteer At times, you can choose to initiate swallowing, but swal- lowing is an example of a sequentially programmed all-or- none reflex in which multiple responses are triggered in a specific timed sequence; that is, a number of highly coordinated activities are initiated in a regular pattern over a period of time to accomplish the act of swallowing. Once initiated, SWALLOWING CANNOT BE STOPPED

Question 25

Romberg test evaluates the maintenance of ___ ___

Answer 25

static equilibrium.

Question 26

what is static equilibrium?

Answer 26

the sense of head position in space or the sense of linear acceleration.

Question 27

what portions of the inner ear detect changes in static equilibrium?

Answer 27

the UTRICLE and SACCULE of the inner ear.

Question 28

How does the use of visual information affect bodily equilbrium? How does a blind person compensate for the absense of visual input?

Answer 28

Vision is important for the development of POSTURAL REFLEX. It provides depth cues and an increased sense of where an individual is located relative to their environment. Visual input also enables the development of coordination, and provides constant input to what is happening in the environment so that the body can activate aspecific motor neurons and properly distribute its weight.

Blind people rely more on proprioceptor input in order to maintain static equilibrium, as they do not get any postural cues from vision. They also rely more on sound perception and are keener to sound vibrations and air movement to cue in on environment.

Question 29

HOw could the observations of a Rhomberg sway test be tested?

Answer 29

test someone with true blindness and someone with their eyes opened and close, and measure their degree of sway. If a person with “true” blindness is better balanced than someone who has their eyes closed, the blind person most likely has mechanisms in place to compensate for the fact that there is no visual input to help him reference his location to the environment or to contribute to his idea of static equilibrium

Question 30

stimulation of a receptor alters the membrane’s:

Answer 30

permeability to selective ions.

Question 31

Examples of tonic receptors. Do they adapt to stimuli?

Answer 31

ex/ muscle stretch proprioceptors and joint proprioceptors. They DO NOT adapt to a stimulus.

Question 32

Phasic receptors. Do they adapt to stimuli?

Answer 32

Touch receptors in the skin. They adapt rapidly and stop responding to a maintained stimulus (ex/ you don’t feel the clothes you’re wearing)

Question 33

What results in the after discharge after a large stress stimulation.

Answer 33

Typically due to residual neurotransmitter still left in the synaptic cleft. After a large amount of acute physical exertion (ex/ pushing on a door frame),, there is still a large amount of acetyl choline left in the synapse prior to being degraded by acetylcholinesterase, resulting in muscle contraction after stimlus is no longer being applied.

Question 34

the first part of swallowing is concious, but becomes unconcious act one its hits the ____ ___ ___, which activates the ___ ___ in the medulla and initiates the swallowing reflex.

Answer 34

the first part of swallowing is concious, but becomes unconcious act one its hits the PHARYNGEAL PRESSURE RECEPTORS, which activates the SWALLOWING CENTER in the medulla and initiates the swallowing reflex.

Question 35

the ability to discriminate between hand held weights of unequal value involves which receptors?

Answer 35

the touch and pressure receptors in the skin of the palms as well as prioprioceptors in the joints an d muscle spindles that respond to movement and stretch.

Question 36

in order to gauge the weight of an object, is moving your hand or keeping your hand stationery while holding the weight more accurate? Why?

Answer 36

movement of hands make it more accurate. It uses GOLGI TENDON ORGANS and involves more PROPRIOCEPTORS AND JOINTS. It uses more receptors in the joints such as the wrist and elbow and shoulder, and it uses more tactile receptors in the hand itself. More info is also received with respect to gravity.

Question 37

Why can’t you swallow multiple times when your mouth is dry?

Answer 37

your body needs TACTILE stimulus (bolus of spit or food) in order to trigger the pharyngeal receptors and activate the medulla’s swallowing center.

Question 38

Equation for difference threshold

Answer 38

difference threshold (%) =(final wt. -reference wt) / Reference weight .x 100

Question 39

What is the “upper limit” difference threshold?

Answer 39

the heaviest LIGHTER weight that can be differentiated from the reference weight. Ex/ if someone was able to detect that there was a change, and that the 65g weight was actually lighter than the 66g weight (v sensitive), then his difference threshold is 1.5% –> can detect a stimulus that differs by reference by only 1.5%

Question 40

What is the benefit to having phasic receptors and the abiltiy to become habituated to touch and pressure stimuli?

Answer 40

Sensory adaptation AVOIDS SENSORY OVERLOAD. It allows new stimuli to stand out to initial “background,” making it easier to evaluate potential threats.

Question 41

describe the ciliospinal reflex

Answer 41

the ciliary muscle and the iris are controled by a CERVICAL REGION (CRANIAL NERVE) which also receives impulses from receptors in the skin of the neck. Therefore, by stimulating the back of the neck, you can trigger pupil dilation.

Question 42

Describe the consensual reflex response of the eye.

Answer 42

A consensual response is any reflex observed on one side of the body when the other side has been stimulated.

For example, if an individual’s right eye is shielded and light shines into the left eye, constriction of the right pupil will occur, as well as the left.

Question 43

Name the afferent and efferent nerves involved in the control of the iris muscle in response to LIGHT conditions. Where would you expect the reflex centre to be located?

Answer 43

In the light, the pupil CONSTRICTS. This is mediated by the PARASYMPATHETIC SYSTEM.

The primary parasympathetic nerve involved is the cranial (OPTIC) nerve

The optic nerve carries the light stimuli ( in the form of an action potential) to the PRETECTAL AREAS of the midbrain. These pretectal areas sens the signals to the Westphal Nucleus, which houses the PREGANGLIONIC PARA SYMP AXONS (THE OCULORMOTOR NERVE)

The preganglionic Oculomotor nerves synapses with the post ganglionic CILIARY GANGLION, which synapses with circular IRIS TISSUE and CONSTRICTS THE EYE

Therefore:
Afferent Nerves: Optic (Cranial nerve), Optic Chiasm and optic tract.

Efferent Nerves: Posterior Commisure, preganglionic oculomotor nerve, post ganglionic ciliary ganglion.

Question 44

Epinephrine causes ____ of the pupil

Answer 44

dilation.

Question 45

two types of muscle on the iris:

Answer 45

1) circular smooth muscle; Causes pupil constriction (parasympathetic nervous system via Ach)
2) radial smooth muscle: stimulus of sympathetic nervous system (NE) = dilation

Question 46

Outline the pupillary dARK reflx neural circuit:

Answer 46

In the dark, the retina and optic tract fibers convey the lack of light activity to the HYPOTHALAMUS.

The hypothalamc neurons descend to the SPINAL CORD and end on the SYMPATHETIC PREGANG NEURONS in the LATERAL HORN in the THORACOLUMBA REGION (T1 to T3)

Sympathetic pregang neurons leave the spinal cord IN the SUPERIOR CERVICAL GANGLION and synapse with , POST GANG axons in the long CILIARY NERVE to the Iris dilator (RADIAL SMOOTH MUSCLE)

Question 47

the eye ____ for close vision by changing the shape of the lens

Answer 47

ACCOMMODATES

Question 48

What muscles control lens shape and what happens in order to focus on something that is close to us?

Answer 48

The iris sphincter is innervated by the postganglionic parasympathetic axons (short ciliary nerve fibers) of the ciliary ganglion.

The ciliary muscles are responsible for the lens accommodation response. They control the tension on the zonules/SUSPENSION LIGAMENTS, which are attached to the elastic lens capsule at one end and anchored to the ciliary body at the other end.

When looking at something close, the parasympathetic nervous system causes the CILIARY MUSCLES to contract, which causes the SUSPENSION LIGAMENTS to RELAX. The lens THICKENS and can focus on objects CLOSER to them.

Question 49

When the sympathetic nervous system is activated, what happens to the pupil? What happens to the lens and by which mechanism?

Answer 49

The pupil dilates due to radial muscle contraction.

The lens flattens, allowing for FURTHER vision. The Ciliary muscles RELAX, and the Suspension ligaments CONTRACT, causing the lens to THIN OUT and flatten.

Question 50

Lens accomodation increases the ____ of the lens

Answer 50

curvature

Question 51

the blind spot of the vision is where the ___ ___ is. Why is there no vision at this location?

Answer 51

blind spot is the optic disc. there are no rods or cones (PHOTORECEPTORS), hence, nothing can be seen.

Question 52

What is a positive afterimage? Why does this occur?

Answer 52

Is a temporary lingering of an image that is seen in LIGHT conditions once the light has been removed. It appears as the same color as the original image.

possibly reflects PERSISTING activity in the brain when the retinal photoreceptor cells continue to send neural impulses to the occipital lobe. Retinal photoreceptors have a surprisingly LONG and SLOW response to light.

Question 53

the sensitivity of retinal photoreceptors _____ gradually while they are being stimulated by light.

Answer 53

DECREASES.

Question 54

What is negative afterimage? What is it caused by?

Answer 54

Caused by the photoreceptors adapting to overstimulation by LOSING sensitivity.

Repeated stimulation of the same cones by staring at the same colored subject for a long period of time will result in temporary photoreceptor exaughstion. When you look at a blank pieace of paper, an after image lingers because photoreceptors have a slow response to light, but because the specific cones are worn out, OPPONENT process cones now fire instead. You will see the OBJECT, but it will be in the OPPOSITE COLOR.

Question 55

blood vessels of the retina lie in front of the ___ and ____ layers

Answer 55

neural and photosensitive layers.

Question 56

T/F: the center of the visual field has no blood vessels passing across it.

Answer 56

TRUE. Vessels appraoch in a radial direction from OUTER parts of the field instead.

Question 57

Where do blood vessels originate from?

Answer 57

you can see the vessels branching from the OPTIC DISK just right of the center.

Question 58

Which 2 spinal nerve pairs are involved in the bicep reflex?

Answer 58

activates the stretch receptors inside the biceps brachii muscle which communicates mainly with the C(CERVICAL) 5 spinal nerve and partially with the C6 spinal nerve to induce a reflex contraction of the biceps muscle and jerk of the forearm.

The musculocutaenous nerve (stimulated by the tapping of cubital fossa) has its fibers derived from C5 and C6

Question 59

Which spinal nerve pairs are involved in the tricep reflex

Answer 59

the Cervical spinal nerve 7 and 6. (C6 and C7). The radial nerve that acts as the MOTOR NERVE inneravates the tricep and carries fibers from the VENTRAL ROOTS (efferent) of the C6 and C7 spinal cord vertebra (and C5, C8 and T1)

Question 60

What is the brachioradalis reflex? what nerve carries this reflex? What spinal level is this nerve?

Answer 60

By striking the BRACHIORADLIS TENDON near the thumb, the reflex is carried by the RADIAL NERVE, which runs to the spinal level of C6 and C7 (also responseible for tricep reflex).