The Sensory System Flashcards
Sensory Unit
Components necessary for sensation.
Receptor
Converts the environment change into action potentials
Neural Pathways
Conducts the APs from the sensory receptor to the interpreting centers of the brain.
Specific Route
Is precise, straight through from a single receptor
Non-specific Route
Input from many types of receptors
Exteroceptors
Respond to changes in the external environment
Visceroceptors (Enteroceptors)
Respond to changes within the body
Proprioreceptors
Respond to information about body position or movement
Transducers
Convert one type of energy to a different type of energy
Adaptation
A constant level stimulus results in a reduction in sensitivity
Peripheral Adaptation
The receptor or sensory neuron reduces the level of activity
Central Adaptation
Involves the CNS, the sensors respond, but the CNS centers do not respond.
Specificity (Law of specific energies)
Each receptor has a specific type of energy to which it responds best.
General (cutaneous) senses
Senses largely associated with the skin although pain and temperature receptors are located in other areas as well. Embedded in the skin and detect changes in the external environment.
Encapsulated Nerve Ending
Nerve ending with one or morel layers of membranes surrounding it.
Nerve Endings Associated With Touch
Meissner’s corpuscles, Merkel’s disks, and the end of organs of Ruffini.
Pacinian Corpuscle
Detect pressure and vibrations
Free Nerve Endings:
Pain Reception
Nociceptors, respond to anything that may cause tissue damage.
Free Nerve Endings:
Touch
Certain free endings wrap around a hair shaft forming a sensitive lever system for touch.
Free Nerve Endings:
Temperature
It’s thought that certain populations of nerve endings can detect temperature
Neural Pathways of the Cutaneous Receptors
A chain of three neurons, which cross over from one side of the nervous system to the other. Consequently, cutaneous sensation from the right side of the body is interpreted by the left side of the brain.
Proprioreceptors
Receptors which provide information as to the status of the muscles in terms of contraction and the position of the body.
Tendon Receptors
Detect the amount of contraction, measured by the stretch of the tendon
Muscle Spindle
Inside the muscle, parallel to the fibers. Detects the amount of relaxation
Joint Receptors
Measure the angle of the joint and therefore permit knowledge of limb positions. This is the only one that works at a conscious level.
Taste and Smell Senses
Chemical senses, respond to chemicals in the environment.
Taste buds
Receptors located in mounds of tissue on the tongue. Each has a gustatory pore and microvilli. Are replaced every 10 days
Gustatory Pore
Permits the saliva containing the dissolved particles to enter the bud and come in contact with the sensory cells which are then activated.
Taste receptros respond to:
5 classes of chemicals: sweet, sour, bitter, salty, and umami.
Taste
A result of taste receptors, olfactory, receptors, and touch receptors.
Sense of Smell
Respond to thousands of different odors. The cells are very sensitive and can detect very low amount of molecules as long as they are in the gaseous state.
Smell sensory cells
Embedded in stratified epithelium about 1 in squared with one section in each nostril. Part of it is on the septum, the other part is on the lateral wall.
Smell Adaptation
The olfactory receptors adapt readily. More readily than any other type of receptor.
Three Layers of the Eye
1) Sclera
2) Choroid Layer
3) Retina
Sclera
Tough outer layer made of white connection tissue. Has a curved, clear portion, the cornea, Is covererd by a mucus membrane, the conjunctiva. Where the muscles are attached.
Anterior Chamber of the Sclera
The cavity behind the cornea, but in front of the iris.
Posterior chamber of the Sclera
Behind the iris, but in front of the lens.
Aqueous Humor
An aqueous fluid which nourishes the lens and the cornea and keeps the proper intraocular pressure.
Choroid Layer
The middle layer, heavily pigmented and full of blood vessels
Ciliary Body
A muscular ring, which suspends the lens from the edges of it’s center hole. The contraction of this body is what changes the shape of the lens and the focus of the eye
Iris
A muscular structure with a hole in the center known as the pupil. Contraction of it’s muscles changes the size of the pupil , and therefore the amount of light that enters the eye. It also gives the eye it’s color.
Lens
A transparent structure enclosed in an elastic membrane. Along with the cornea, it is responsible for proper eye focus.
Vitreous bod
Has a jelly-like fluid which fills the vitreous cavity behind the lens.
Retina
The 3rd layer of the eye. Consists of 3 layers.
1) Photoreceptors - rods and cones
2) Bipolar neurons
3) Ganglion cells
Optic Disk
A spot where the optic nerves converge and exit the eye. There are no receptor cells and therefore a blind spot
Rods
a) Used in black and white vision only
b) Function in low light only
c) Serve in low acuity vision only
Cones
a) Responsible for color perception (red, green, blue)
b) Active in bright light only
c) Serve in high acuity or detailed vision only.
Dark Adaptation
It takes about 30 minutes of darkness for all the rhodopsin to regenerate from being bleached and for the eyes to become dark adapted.
Eyebrows and Eyelashes
There for protection, it’s important to blink the eye every 3-7 seconds to moisten the eye.
Extrinsic Muscles
Superior Rectus Inferior Rectus Lateral Rectus Medial Rectus Superior Oblique Inferior Oblique
Lacrimal Apparatus
Produces and drains tears
Tears
A fluid produced by lacrimal glands. Contain Igs, lysozymes, and a dilute saline solution
Ear
The organ which is the site of both equilibrium and sound detection.
3 Ear Regions
Outer
Middle
Inner
Outer Ear
Ear flat which extends to the tympanic membrane. Contains wax and hair for protection.
Middle Ear
The tympanic membrane and the air filled cavity behind it. Contains the ear ossicles, the malleus, incus, and stapes.
Inner Ear
Includes the vestibule, semicircular canals, and cochlea.
Cochlea
The auditory portion, it resembles a snail shell. It’s divided into 3 chambers.
Organ of Corti
Located on the basilar membrane of the scala media. Hairs located on this structure bend and produce action potentials that are perceived as sound.
Semicircular Canals
Three of them, located at right angles to each other. They detect movement and play a key role in dynamic equilibrium.
Vestibule
consists of the uticle and the saccule. Contains otoliths which are responsible for static equilibrium.
Myopia
Nearsightedness. Able to see close up but not at a distance. The eyeball is too long, so the image is focused in front of the retina. It can be corrected by a concave lens.
Hyperopia
Farsightedness. Able to see well at a distance, but not close up. The eyeball is too short, so the image is focused behind the retina. It can be corrected by a convex lens
Presbyoptia
Farsightedness in old age. The lens loses it’s elasticity, happens around 40-50 yrs old.
Astigmatism
Unequal thickness in the cornea or lens. Can be corrected by special cylindrical lenses
Glaucoma
Results from abnormally high pressure in the eye due to the failure of the aqueous humor to drain properly. Can lead to blindness
Cataracts
Clouding over the lens, it can become opaque. Due to the breakdown of the capsule of the lens.
Deafness
This is a lack of hearing or at least a significant loss of hearing.
Sensorineural Deafness
Impairment of the cochlea, some component of the neural pathway, or the interpreting center of the brain.
Conduction Deafness
There is a problem in the middle ear.
Vertigo
Sensation of motion. Due to inner ear disturbances, a central nerve disorder or may be psychogenic.
Motion Sickness
Seems to be a mismatch in the equilibrium information. Eyes fix on a position and give information, but the ear gives different information, the conflict between the eye and the ear is the motion sickness
Dementia
State of consciousness characterized by difficulties of spacial orientation, memory, language, and changes in personality.
Night Blindness
Due to a vitamin A deficiency. There is a degeneration of rods.
Parkinsons
Inadequate dopamine levels in the brain.
Pathway of Sound Through the Ear
Tympanic Membrane —-> Malleus —-> Incus—-> Stapes —-> Oval Window —-> Perilymph —-> Vestibular Membrane —-> Endolymph —-> Hair cells of the organ of Corti.
