A Beka Biology Chapter 8
Terms in this set (79)
a special glial cell which produce layers of myelin sheathing that acts much like the insulation of an electrical wire.
multiple sclerosis (MS)
a disease of the brain and spinal cord that occurs when the body's immune system attacks the glial cells that provide myelin sheaths for nerve cell axons.
the inability of the muscles to move.
when a neuron is triggered to fire, a brief pulse of positive charge sweeps through the neuron and races down the axon like the fuse of a firecracker. this wave is called
an enclosed junction between the axon of one neuron and the dendrites or cell body of another.
the chemical caused when the action potential reaches the synapse.
affects the patient's control of posture and movement; it is characterized by tremors and stiffness of the limbs.
a quick, automatic response.
the simplest nerve pathway.
a form of partial or complete hearing loss due to repeated or prolonged exposure to excessively loud sounds.
a scientific measure of loudness.
rapid eye movement.
one of the most commonly abused drugs in the world today.
a nervous disorder that causes degeneration and inflammation of the nerves.
a condition characterized by pain in the lower back and the back of the thigh, is caused by a pinching of the sciatic nerve of the lower spinal cord.
the most common serious injury of the nervous system.
a period of paralysis of the central nervous system accompanied by a short period of unconsciousness.
a loss of memory.
commonly known as lockjaw because severe spasms of the jaw muscles make it hard to open the mouth.
a disturbance of the brain caused by physical illness elsewhere in the body.
the disorder which results from the slow process of natural nerve cell loss.
caused by the death of brain cells.
a disease that has symptoms similar to dementia but more severe.
a common neurological disorder where brain cells fire rhythmically.
living sensors devoted to processing information that your senses provide.
include all the senses of your skin (primarily touch and temperature).
sight, hearing, smell, taste, and balance.
intricately designed organs that provide the special senses.
a bare dendrite that reacts to a certain type of strong stimulus (pain).
the sensory receptors responsible for sensations of touch and pressure.
receptors that respond to temperature changes.
receptors in your skin react to temperatures above normal body temperature.
receptors that are sensitive to temperatures below normal body temperature.
the senses of taste and smell.
located on the tongue and in the nose, acts as the stimulation for chemical senses.
the organs responsible for the sense of taste.
the nose's sensory receptors are located in the upper part of the nasal cavity and are connected to the brain by the
a taut membrane stretched across the ear canal like the surface of a drum.
malleus (hammer), incus (anvil), and stapes (stirrup)
three tiny bones in the middle ear that relay sound vibrations to the inner ear.
the actual organ of hearing.
a coiled tube in the inner ear resembling a snail's shell.
carries electrical messages to the brain where they are translated into meaningful sounds.
located in the inner ear is an assembly of three, fluid-filled tubes, which serve as balance-sensors.
a type of hearing where the inner ear also receives vibrations from the jawbones.
ringing in the ears.
a balancing pressure in the middle ear when the outside air pressure changes.
provides a surrounding protection of heavy bone.
closes reflexively to keep foreign objects from entering the eye.
produced by tear glands (lacrimal glands).
(tear glands) located under the upper eyelid on the side away from the nose.
an enzyme in tears which destroys bacteria.
attached to each eye is a set of six muscles which serve to move the eye.
sclera and cornea
the outermost layer of the eye consists of the opaque
often called the white of the eye, and the
the middle layer of the eye, includes (in order from front to back) the iris, the ciliary body, and the choroid.
the innermost layer of the eye.
the tough outer layer of tissue which provides protection and the supporting frame for the interior portions of the eye.
the transparent portion of the eye through which light enters the eye.
a layer of connective tissue rich in blood vessels, which provides most of the eye's nourishment.
the involuntary muscles of this serve to adjust the lens so that it will focus on objects at varying distances.
the colored portion of the eye.
the opening in the eye through which light enters.
long, thin cells in the light-sensitive layer of the retina. These help us to see light.
slightly shorter and thicker than the rods and have tips shaped somewhat like an ice-cream cone. These are located in the light-sensitive layer of the retina. These are responsible for our ability to see color.
the area of the eye that produces the clearest vision.
a large bundle of individual nerves, each of which carries nerve impulses from a specific region of the retina to the brain.
the point on the retina where the optic nerve leaves the eyeball. At this point there are no light-sensitive cells to receive visual messages.
the substance in rod cells that absorbs light.
persistence of vision
a phenomenon where the image or picture of the object on the retina persists about a tenth of a second after the object is gone.
a clear fluid produced from blood circulating in the ciliary body, located between the cornea and the iris and lens.
the part of the eye that focuses the rays of light which pass through it.
the increase in the curvature of the lens to focus on nearby objects.
between the lens and the rear of the eye is a transparent, jellylike substance that is about 98% water called
the ability to see only near objects clearly.
when the eye is too short or the lens is too flat, objects are brought to focus at a point which would lie behind the retina.
usually the result of an asymmetrically curved cornea, which causes light rays entering the eye to be bent incorrectly.
when the eye's lens becomes less elastic (usually with age), and it is difficult to focus on nearby objects.
people who cannot distinguish one or more of the primary colors of light (red, blue, or green).
when some people's eyes do not become adjusted to darkness, remaining almost totally blind in dimly lit places.
a common cause of blindness is
, a condition in which the pressure of the fluid inside the eye becomes much higher than normal.
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