Senses lab quiz Flashcards
What are the 3 components of a reflex mechanism?
- Receptor organ
- Communications network (connects the receptor and effector organs)
- Effector organ
Reflexes are initiated by
An input stimulus
Reflexes result in
An output response. For some reflexes, the appropriate response to the stimulus has been programmed into the nervous system
Spinal reflex
When an individual experiences a painful stimulus (burning their hand), the spinal reflex causes rapid withdrawal of the hand from the painful stimulus. The spinal reflex requires transmission from the periphery to the spinal cord and back to the effector organ- no action is required by the brain.
Which reflexes involve centers of the brain?
Eye reflexes and labyrinth reflexes. The response is determined after multiple different inputs are evaluated.
Jendrassik’s Maneuver
The Jendrassik maneuver is a medical maneuver wherein the patient interlocks their fingers together. The tendon below the patient’s knee is then hit with a reflex hammer to elicit the patellar reflex.
Palpate
To examine by touch
Ipsilateral
Same side
Which division of the nervous system controls the ciliospinal reflex?
The sympathetic nervous system, occurs in response to a painful stimulus
Ciliospinal reflex
If the skin on the nape of the neck is pinched, the pupil of the eye on the same side will dilate
Plantar reflex
When the sole of the foot is scratched or stroked on the inner side, the toes flex downward. This is a normal adult reflex.
Babinski reflex
When the sole of the foot is scratched or stroked on the inner side, the toes fan out and the big toe flexes dorsally (upward). This is normal reflex in children under one year of age because their nerves are still undergoing myelination.
When the Babinski reflex occurs in adults, what does this indicate?
It is often associated with damage to the pyramidal tract fibers (efferent nerve fibers that carry signals from the cerebral cortex to the brainstem or spinal cord).
What is a function of the semicircular canal mechanism?
To aid visual fixation on moving targets
Nystagmus
If the semicircular canals are stimulated under experimental conditions, reflex response results in a movement
of the eyes
What are the 2 components of nystagmus?
Fast and slow phases. The direction of nystagmus is designated as that of the fast phase (nystagmus will change direction after a certain amount of time).
Rotary nystagmus
If a person is angularly accelerated in one direction, their eyes will move very slowly in one direction as though to maintain fixation on a moving target, then very rapidly swing back in the other direction. The initial direction is opposite the direction of rotation, then the eye jerks back toward the direction of rotation
What causes rotary nystagmus
The acceleration of fluid in the semicircular canals which stimulates the cristae in the ampullae and produces the sensation of turning
Post rotary nystagmus
The same phenomenon as rotary nystagmus, occurs after suddenly stopping a spinning person- eyes will move very slowly in one direction as though to maintain fixation on a moving target, then very rapidly swing back in the other direction
Knowledge of changes in our environment depends on
The sensory nervous system and its receptors
5 senses
- Sight
- Hearing
- Touch
- Taste
- Smell
Exteroreceptors
Receptors which receive stimuli from outside the body- usually located on the surface of the body.
Interoceptors
Detect changes within the body, located deep within tissues like muscles and tendons.
Which areas of the body have a greater sense of tactile discrimination (feel)
Areas of the body that have many touch receptors, such as the fingers
The number of sensory impulses transmitted by sensory receptors change with
Intensity of the stimulus and the length of time the stimulus is applied
Adaptation
If a stimulus is applied for a prolonged
period of time without movement, the rate of receptor discharge will slow and conscious awareness of the stimulus will decline or will be lost (until some stimulus change occurs)
Nerve deafness
A defect in the auditory nerve or cochlear apparatus.
Weber test
The subject holds the vibrating fork against the bridge of their nose. A person with normal hearing will localize the sound as coming from the midline position. A person with conduction deafness will hear the sound better in that ear
Conduction deafness
Defective middle ear function
Why can a person with conduction deafness hear a vibrating fork better in the deaf ear with the weber test?
In a normal ear, the sound of the fork is partially masked by environmental noise that the deaf ear is less sensitive to. Also, in the normal ear the sound is dampened by the tensor tympani and stapedius muscles that prevents the full amplitude of vibration of the auditory ossicles. This reflex is less effective or absent with conduction deafness.
During the weber test, what would cause a person to better hear the vibrating fork with the normal ear?
A defect in the auditory nerve or cochlear apparatus- this is because neural activity is essential for hearing
Rinne test
A tuning fork is placed on the subject’s mastoid process at the level of the upper portion of the ear canal. When the sound is no longer audible, the tuning fork is placed in front of the auditory canal.
What do the results of the Rinne test indicate?
A person with normal hearing will hear the sound conducted through air a few seconds longer than sound conducted through bone.
The person with conduction deafness will hear as long or longer by bone conduction
The person with nerve deafness will
hear longer by air conduction, but usually requires a louder sound to hear at all
Blind spot/optic disc
an area on the retina where the optic nerve and blood vessels enter and leave the retina and hence there are no rods or cones for visual reception.
Visual acuity
The power to discriminate details
Snellen test
The letter chart tested at physicals- the letters on certain lines should be able to be read easily at certain distances if a person has normal visual acuity
What is the visual acuity formula?
V= d/D
d is the distance at which the patient can read the letters
D is the distance at which a normal eye can read the letters.
Someone with 10/20 vision, for example, has subnormal vision because they can only read the letters at 10 feet when they should be visible 20 feet away.
Color blindness
A genetic condition linked to the X chromosome. Red green colorblindness is the most common type- the person lacks either red or green cones in the retina. A person who lacks red cones will perceive red as green- the red wavelengths will stimulate primarily red cones
Isihara test
A color blindness test. Charts consist of various color dots arranged into a picture. A person with normal color vision will see one figure, a person without normal color vision will perceive a different number or figure.
Pupillary reflex
When one eye is exposed to light, both pupils will constrict. The response of the pupil in the stimulated eye is the direct response, and the pupil of the contralateral pupil (which is not stimulated) is the consensual response.
Pupillary reflex receptor and effector
The receptors are the photoreceptors of the retina and the effector is the smooth muscle of the iris.
Accommodation reflex
This reflex is required for near vision. A few things occur:
- Pupillary constriction (to sharpen the image on the retina)
- Convergence of the optic axis- both eyes move medially. Keeps object focused on foveae
- Increased convexity of the lens to increase its refractive power
What happens within the eye when viewing near and far objects?
The curvature of the lens is controlled by ciliary muscles. When viewing near objects, the ciliary muscles contract. The suspensory ligaments loosen, which causes the lens to become rounder/bulge outward. This gives the lens higher refractive power. For far objects, the muscles relax and the lens is flat.
Patellar reflex
Knee jerk response when the patellar tendon is tapped with a reflex hammer. This is caused by stretching of the patellar tendon and contraction of the quadriceps muscle.
What happens to the patellar reflex when the Jendrassik maneuver is performed?
The patellar reflex is exaggerated. The maneuver activates the fight or flight response so everything is “primed”. That way, a lighter tap has a stronger response. Distraction of the individual will also a play a role
Achilles reflex
When the Achilles tendon (between the foot and leg) is tapped with a reflex hammier, you observe the ankle jerk reflex. The contraction of the gastrocnemius muscle causes plantar flexion of the foot.
What happens to the Achilles reflex when the subject is grasping the back of a chair?
The reflex should be stronger, just like the Jendrassik maneuver makes the Patellar reflex stronger. It activates the sympathetic nervous system and is related to distraction in the patient.
Which muscles would contract if you pushed down on a table?
Triceps
Which muscles would contract if you tried to lift a table?
Biceps
Which semicircular canal is stimulated when the head touches the shoulder?
Posterior semicircular canal
Which semicircular canal is stimulated when the head is moving up and down?
Superior semicircular canal
Which semicircular canal is stimulated when moving the head from side to side?
Lateral semicircular canal
How would a person’s ability to do the past pointing test be altered by spinning?
The person would point in the direction of the previous rotation. If the previous rotation was clockwise, they will consistently point to the right of the target.
What is the purpose of adaptation?
Prevents sensory overload- we no longer consciously perceive a routine stimulus to focus on other aspects of our environment.
Accommodation
Accommodation is the adjustment of the optics of the eye to keep an object in focus on the retina as its distance from the eye varies.
Which muscles of the eye are involved in accommodation?
The ciliary muscles are involved in the change in lens shape. The sphincter pupillae constricts the pupil, and the medial rectus muscles contract so the eyes will converge
Presbyopia
“Farsightedness”- loss of the eyes’ ability to focus on nearby objects. It is caused as the lens becomes less flexible with age and can no longer change shape to focus on nearby objects. Could potentially be corrected by convex shaped corrective lenses.
Myopia
Nearsightedness- difficulty seeing things that are far away. This is caused by an elongated eyeball shape (past the focal point of the retina). Correction- concave shaped corrective lenses
Young-Helmholtz theory of color vision
a theory to explain color vision in terms of components or processes sensitive to three different parts of the spectrum, corresponding to the colors red, green, and blue. According to this theory, other colors are perceived by stimulation of two of the three processes, whereas light that stimulates all three processes equally is perceived as white.
