Peripheral Nervous System

Peripheral Nervous System

PERIPHERAL NERVOUS SYSTEM Link between the CNS and the rest of the body, consisting of the cranial, spinal nerves, and the ganglia. Divided into two divisions: Sensory Division which transmits impulses from the sense organs to the CNS. Motor Division which transmits impulses from the CNS to the muscles or glands. Somatic Nervous System

Regulates activities that are under conscious control. Reflex arc: Quick response to stimuli using the receptor, sensory, and motor neurons with the effector. Fig. 37-22 Autonomic Nervous System Fig. 37-23 Regulates activities that are automatic or involuntary Sympathetic: Fight/flight system http://www.henry.martinez.net/misc/whatswrong.htm Parasympathetic: calmer functions such as digestion Work as a team, they complement each other

THE SENSES - 1 VISION: THE EYE Three layers: Outer layer consisting of the sclera and cornea Middle layer consists of the choroid, ciliary body, and the iris Inner layer consists of the retina Sclera- white of the eye, maintains shape of the eye and place for muscles to attach. In front of the eye, the sclera forms a transparent layer called the cornea in which light enters.

Aqueous humor- inside the cornea, small chamber filled with fluid. Choroid- back of the aqueous humor, contains the blood vessels which eventually form the iris- the colored part of your eye. Pupil- small opening in the middle of the iris for light to enter, regulated by tiny muscles to open and close depending of light needs. Lens- behind the iris, contains crystalin, is slightly bent for focusing DISORDERS OF THE EYE

Astigmatism: Uneven curvature of the cornea, cant bend light Nearsightedness (myopia): horizontal axis is longer than the vertical axis, or when the ciliary muscle contracts too strongly. Focus is in front of the retina. Farsightedness (hyperopia): vertical is longer than horizontal. Image is focused behind the retina. Glaucoma: Excess aqueous humor accumulates inside the eye ball. Blood vessels collapse and cause pressure.

Cataracts: Gradual clouding of the lens Blind spot: The optic disk, where the nerve fibers stream to the outside behind the eyeball, is w/o rods and cones. THE SENSES - 2 Photoreceptors- layer of the retina, converts light energy into impulses that are carried to the CNS, contains cones and rods Contain rhodopsin which enables the eye to respond to wavelengths

Rods are sensitive to all colors, but cant distinguish between them Cones are less sensitive, but are able to distinguish colors. The impulses leaves the eye by way of the optic nerve, which carries the signal to the optic lobe of the brain. HEARING AND BALANCE FIG. 37-26 THE EAR! What is sound???? Fleshy, visible, external part funnels sounds into the auditory canal The auditory canal stops at the eardrum (tumpanum) (Middle ear) From eardrum sound is transmitted through three tiny bones:

malleus (hammer), incus (anvil), and stapes (stirrup) The stapes vibrates the oval window, transmits sound to the cochlea THE SENSES - 3 Cochlea begins the inner ear which is a snail shaped fluid-filled cavity. When the fluid vibrates, hair cells are pushed back-n-forth, which provides the stimulation for nerve impulses, which are carried to the acoustic nerve.

BALANCE: 3-Semicircular canals & 2 tiny sacs: Just above the cochlea, filled with fluid and lined with ciliated hair cells Embedded in a gelatin-like substance with tiny grains of calcium carbonate and protein (otoliths) which roll back-n-forth due to gravity, acceleration, and deceleration. SMELL-NOSE (fig. 37-28) chemoreceptors Upper part of the nasal cavity, has cilia that react to

chemicals in the air, how it works is not completely understood. SENSES - 4 Taste Also has chemoreceptors stimulated by chemicals located on the tongue Taste buds are also located on the roof of mouth, lips, & throat Four main kinds: sweet, sour, salty, & bitter Works with smell to detect flavors in food

Touch & Related Senses Largest sense organ is your skin Receptors include two for heat & cold, two for touch, one for pain Heat & cold scattered below skin surface; ratio 3-4:1 (W:C) Touch range in concentration, more fingers, toes, lips Pain located throughout, sensations range from prickling pain (fast pain) to burning & aching pain (slow pain)

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