Sensory Physiology

Sensation

is the process by which information about the environmental stimuli is received by a sensory receptor and then converted to action potentials that are sent to the brain.

Perception

involves the brain receiving and interpreting the action potentials such that we are consciously aware of the sensation.

Exteroceptor

Are sensitive to stimuli arising outside the body, and most are near or at the body surface

Interoceptor

respond to stimuli within the body

Mechanoreceptor

a sensory receptor that responds to mechanical stimuli such as touch, pressure, and vibration.

Proprioceptor

a sensory receptor found in muscle, joint, and tendon tissue that detects changes in body position or movement.

Thermoreceptor

a sensory receptor that responds to changes in temperature. 

Photoreceptor

a sensory receptor that detects light or changes in light, found only in the eyes.

Chemoreceptor

a sensory receptor that responds to chemicals in solution.

Nociceptor

a sensory receptor that responds to stimuli that are harmful to the body.

Reflex arcs

The body can respond to some stimuli in a rapid, predictable pattern called

receptor, integration center, effector organ

A reflex arc requires 3 components…

Motor response

how the body's muscles react to a command or a stimulus, carried out by the effector organ

Intrinsic reflex

a rapid, predictable motor response to a stimulus. It is unlearned, unpremeditated, and involuntary, and is built into our neural anatomy.

Spinal reflex arc

associated with very rapid movement of skeletal muscle tissue. In this type of reflex, the integration center is the spinal cord (rather than the brain). Occurs without the direct involvement of higher brain centers.

Pupil

the open space at the center of the iris, the colored portion of the eye, that allows light to enter the eye and strike the retina.

Dilator pupillae muscle

when it contracts, it causes the pupil to become wider

Sphincter pupillae muscle

when it contracts, it causes the pupil to become narrower

Consensual reflex

when the stimulus is applied to only one side of the body, but the response (or output) is observed on both sides of the body.

Lens

a structure inside the eye that helps to focus light directly on the retina by bending light as it enters the eye, allowing for clear vision.

Pupil accommodation

the size of the pupil changes according to the distance of the object requiring focus to adjust the amount of light entering the eye

Lens accommodation

the lens can change shape to change the ability to refract (or bend) light to focus it on the retina.

Refraction

the bending of light as it passes through the cornea and lens so that images focus sharply onto the retina

Refractive power

the measure of the cornea and lens's ability to bend (refract) light rays so they focus cleanly on the retina. Ultimately determined by how scattered light rays are as they enter the eye.

The more round the lens (or the more it bulges), the

stronger refractive power

The flatter the lens, the

less refractive power

Convergence

the process of both eyes moving (or pointing) inward to focus on an object. This action requires the use of the medial and lateral rectus muscles of the eyes

Tendon Reflexes

are any reflex arc that occurs when a tendon is tapped. This causes a rapid and predictable contraction of the muscle associated with the tendon.

Knee-jerk reflex

also called the patellar reflex, occurs when the patellar tendon just below the patella (or kneecap) is stretched when it is tapped by a reflex hammer

Jendrassik’s maneuver

alters the patellar reflex by forcing the individual to focus their attention somewhere else in the body, rather than thinking about the patellar reflex being performed on them

Ankle-jerk reflex

is also called the achilles; occurs when the Achilles tendon on the back of the ankle is tapped

Antagonistic muscle

pairs usually have opposing action on a part of the body. Important for the tendon reflexes and allows the muscle that contracts during the reflex to do so in a strong, smooth, and coordinated pattern. Without this feature, the contracting muscle will not be able to produce as much force, and the movement will be more “sloppy,” potentially causing injury.

Ciliospinal reflex

 is a response mediated by the sympathetic nervous system (the “fight or flight” response) in response to pain.

Babinski’s reflex

An automatic muscular response that occurs when the sole of the foot is firmly stroked. Abnormal and indicates damage to the pyramidal tract fibers, a tract of nerve fibers that allows for voluntary movement

Palpate

examine by touch

Plantar reflex

a reflex that protects the sole of the foot when a painful stimulus is applied to the sole

Plantar flexion

The toes can either bend (or curl) downward in a movement called

Dorsiflexion

the big toe can point upward in a motion

Inner ear

receptors here respond to changes in head position during linear acceleration and rotational movement. Plays a role in hearing and in equilibrium. In the equilibrium role, the inner ear helps to orient the body during movement to maintain equilibrium (in this case, balance) by making automatic adjustments to muscle and eye movements during and after movement

Semicircular canals

three fluid-filled tubes in the inner ear that contribute to balance and equilibrium while moving by aiding in visual fixation on moving objects.

Nystagmus

a reflexive movement of the eyes

Anterior semicircular canal

stimulated by forward and backward head movements

Posterior semicircular canal

is stimulated by movement causing the head to tilt to the side

Lateral semicircular canal

is stimulated by movement where the head spins or moves side-to-side

Fast phase nystagmus

rapid, corrective eye movement (a saccade) that snaps the eye back toward its intended target. The direction of nystagmus is designated as that of the _____.

Slow phase nystagmus

the initial, involuntary drift of the eye away from a visual target, named for the speed at which the eyes move during nystagmus

Rotary nystagmus

can be observed during movement when the fluid in the semicircular canal moves (or flows), stimulating receptors in the inner ear.

Post-rotary nystagmus

where the eyes continue to move reflexively after movement has stopped. The fast phase and slow phase of post- rotary nystagmus is opposite that of rotary nystagmus.

Spatial orientation

the ability to maintain the body’s position and posture in relation to our surroundings. It allows us to move around objects rather than bump into them and allows us to move our own body parts in a coordinated fashion.

Proprioceptors

this sensory receptor monitors information such as joint position and stretch, joint angles, tendon tension, and muscle stretch. This information concerning the position and movement of our body parts allows the brain to produce smooth, coordinated body movements without needing to visually monitor the movement.

Photoreceptors

receptors in the eyes provide visual information to the brain. This allows the brain to understand how body parts are positioned relative to one another and the body and to be aware of our external environment (objects that surround us, etc)

Mechanoreceptor

 responsible for the sensation of touch. This type of sensory receptor is found in the skin and is stimulated by the physical deformation of the receptor.

Two-point threshold

the smallest distance at which two points of contact can be felt The smaller the receptive area, the more sensitive the skin will be to touch because it provides specific information about which mechanoreceptor has been stimulated in the skin.

Sensory adaptation

if a stimulus is applied for a prolonged period without change, the rate of receptor discharge will slow, and conscious awareness of the stimulus will decline or be lost (until some stimulus change occurs. This is called

Conduction deafness

results from damage to structures from the tympanic membrane to the auditory ossicles (malleus, incus, and stapes). Damage to these structures prevents transmission of sound to the inner ear.

Nerve deafness

is a form of deafness that occurs when the auditory nerve or brain is damaged such that action potentials relating to sound are either not produced by the auditory nerve or cannot be interpreted by the brain.

Condition: No hearing loss. What is the Weber Test Result?

No lateralization

Condition: No hearing loss. What is the Rinne Test Result?

Sound perceived longer by air conduction

Condition: Conduction deafness. What is the Weber Test Result?

Lateralization to the poorer ear

Condition: Conduction deafness. What is the Rinne Test Result?

Sound perceived as long or longer by bone conduction

Condition: Nerve Deafness: What is the Weber Test Result?

Lateralization to the better ear

Condition: Nerve Deafness: What is the Rinne Test Result?

Sound perceived longer by air conduction

Near point

the closest point at which an object can be placed from the face and still form a focused image within the eye’s accommodation range. This test is used to demonstrate the elasticity of the lens and its ability to accommodate when viewing an object up close.

Presbyopia

loss of near focusing ability. As we age, the lens becomes less flexible and the accommodation becomes less effective

Optic Disc

sometimes called the “blind spot,” is an area at the back of the eye on the retina where there are no photoreceptors for visual reception. There are no photoreceptors here.

Visual acuity

the sharpness of vision, involving the ability to discern letters or numbers at a given distance according to a fixed standard.

Snellen Test

The overall idea of this test is that for a “normal” eye (i.e., an eye with normal vision), letters of different sizes should be seen clearly at different distances.

Myopia

nearsightedness, is caused by the eyeball being misshapen such that light cannot be correctly focused on the retina. Individuals with myopia can see objects up close, while objects farther away are blurry or unclear

Hyperopia:

farsightedness, is also an issue caused by the shape of the eyeball and light not being focused directly on the retina. But here, individuals can see objects far away clearly while nearby objects are blurry or unfocused

Young-Helmholtz theory of Color Vision

theory that states that the human retina contains three distinct types of photoreceptor cells (cones) that respond to different wavelengths of light: short (blue), medium (green), and long (red)

Cone

One type of photoreceptor in the eye that allows for color vision.

Color blindness

an abnormality that is transferred genetically, resulting from a lack of a particular gene on the X chromosome. Being a recessive trait, an individual with XY chromosomes has a higher likelihood of being color blind if the recessive trait is present on the X chromosome.

Red-green color blindness:

the person lacks either the red or the green cones in the retina.

Ishihara Test

Testing for colorblindness. This type of test consists of collections of differently colored dots arranged on a plate. People with color vision can see numbers formed by the differently colored dots, while those who are colorblind can see the dots but cannot recognize a number.

Sweet

elicited by sugars, saccharin, alcohols and some amino acids.

Salty

 elicited by metal ions (sodium chloride is especially “salty”). 

Sour

elicited by acids releasing their hydrogen ions in solution. 

Bitter

elicited by alkaloids like quinine, nicotine, caffeine, morphine.

Umami

elicited by the amino acids glutamate (of MSG—the tasty food additive) and aspartate.