Chapter_14&15.txt

describes the appearance of the lower end of the spinal cord and its spinal nerve as a horse’s tail

swelling in the dorsal root of each spinal nerve

supplies somatic motor and sensory fibers to smaller nerves that innervate the muscles and skin of the posterior surface of the head, neck and trunk

splitting and rejoining of autonomic fibers

are complex networks formed by the ventral rami of most spinal nerves (not T2 through T12) subdividing and then joining together to form individual nerves

region of skin surface area supplied by afferent (sensory) fibers of a given spinal nerve

skeletal muscle or muscles supplied by efferent (motor) fibers of a given spinal nerve

axons of sensory and motor neurons

mainly axons of motor neurons only

mainly axons of motor neurons and a small number of sensory fibers (proprioceptors)

either contraction of smooth or cardiac muscle or secretion by glands

contraction of skeletal muscles

center of reflex arc is in the spinal cord

center of reflex are is in the brain

action that results from a nerve impulse passing over a reflex are; predictable response to a stimulus

includes all voluntary motor pathways outside the central nervous system

reflexes deviate from normal in certain diseases, and reflex testing is a valuable diagnostic aid

extension of the lower leg in response to tapping the patellar tendon; tendon and muscles are stretched, stimulating muscle spindles and initiating conduction over a two-neuron reflex arc

center of reflex are located in spinal cord gray matter

mediating impulses enter and leave at the same cord segment

mediating impulses come from and go to the same side of the body

result of type of stimulation used to evoke reflex

produced by extensors of the lower leg

tapping tendon is stimulus that elicits reflex

result of deep location of receptors stimulated to produce reflex

extension of the foot in response to tapping the Achilles tendon; tendon reflex and deep reflex mediated by two-neuron spinal arcs; centers lie in first and second sacral segments of the cord

flexion of all toes and a slight turning in and flexion of the anterior part of the foot in response to stimulation of the outer edge of the sole

Extension of great toe, with or without fanning of other toes, in response to stimulation of outer margin of sole of foot; present in normal infants until approximately 1 ½ yrs of age and then becomes suppressed when corticospinal fibers become fully myelinated

winking in response to the cornea being touched; mediated by reflex arcs with sensory fibers in the ophthalmic branch of the 5th cranial nerve, center in the pons, and motor fibers in the 7th cranial nerve

drawing of the abdominal wall in response to stroking the side of the abdomen; superficial reflex; mediated by arcs with sensory and motor fibers in T9 – T12 and centers in these segments of the cord

efferent neuron with which a preganglionic neuron synapses within autonomic ganglion

conducts impulses from the central nervous system to an autonomic ganglion

short branch by which some postganglionic axons return to a spinal nerve

cell bodies are located in nuclei in the brainstem or lateral gray columns of the sacral cord; extend a considerable distance before synapsing with postganglionic neurons

dendrites and cell bodies are located in parasympadendrites and cell bodies are located in parasympathetic ganglia which are embedded in or near autonomic effector

release norepinephrine; axons of postganglionic sympathetic neurons

release acetylcholine; axons of preganglionic sympathetic neurons and of preganglionic

enzyme that breaks up neurotransmitter molecules taken back up by the synaptic knobs

enzyme that breaks down the remaining neurotransmitter

slows heartbeat and acts to promote digestion and elimination

responds to stimuli by converting them to nerve impulses

a graded response and develops when adequate stimuluscacts on receptor; when threshold is reached, an action potential is triggered

a functional characteristic of receptors; receptors potential decreases over time in response to a continuous stimulus, which leads to a decreased rate of impulse conduction and a decreased intensity of sensation

small, with less tightly coiled dendritic endings within their capsule; involved in touch, low-frequency vibrations

relatively large and superficial in placement; mediates touch and low frequency vibration; large numbers in hariless skin areas, such as niples, fingertips, and lips

six types; all have connective tissue capsules and are mechanorecptors;

activated when "deformed" to generate receptor potential

activated by amount or changing concentration of certain chemicals, e.g. taste and smell; finite system

activated by changes in temperature

activated by intense stimuli that may damage tissue; sensation produced in pain; deep in finger or cutenous

found only in the eye; respond to light stimuli if the intensity is great enough to generate a receptor potential

concentrated in the hypothalamus; activated by changes in concentration of electrolytes (osmolarity) in extracellular fluids

have a flattened capsule and are deeply located in the dermis; mediate crude and persistent touch; may be secondary temperature receptors for heat (85 - 120)F

large mechanoreceptors that respond quickly to senstaion of deep pressure, high-frequency vibration, and stretch; found in deep dermis and in joint capsules; they adapt quickly, and sensations they evoke seldom last for long periods

two types; operate to provide body with information concerning muscle length and strength of muscle contraction

composed of 5 to 10 intrafusal fibers lying between and parallel to regular (extrafusal) muscle fibers

located at juction between muscle tissue and tendon; made up of encapsulated neuron endings associated with collagen bundles

located on olfactory sensory neurons that touch the olfactory epithelium lining the upper surface of the nasal cavity

chemoreceptors; gas molecules or chemicals dissolved in the mucus covering the nasal epithelium stimulate the olfactory cells

located in most superior portion of the nasal vavity

extremely sensitive and easily fatiged

when the level of odor-producing chemicals reaches a threshold level

sense organs that respond to gustatory or taste stimuli; associated with papillae

sensory cells in taste buds

the visible portion of the ear

tube leading from the auricle into the temporal bone and ending at the tympanic membrane

Tiny, epithelium-lined cavity hollowed out of the temporal bone

attached to the inner surface of the tympanic membrane

attached to the malleus and stapes

attached to the incus

opening into inner ear; stapes fits here

opening into inner ear; covered by a membrane

made up of the vesibule, cochlea, and semicircular canals

made up of utricle and saccule inside the vestibule, cochlear duct inside the cochlea, and membranous semicircular ducts inside the bony semicircular canals

organs involved with balance

involved with hearing; bony labyrinth;

clear, potassium-rich fluid filling the membranous labyrinth

similar to cererospinal fluid, surrounds the membranous labyrinth, filling the space between the membranous tunnel and its contents and the bony walls that surrounds it

rests on the basilar membrane; consists of supporting cells and hair cells; also called spiral organs

floor of the cochlear duct

lies inside the cochlea; only part of the internal ear concerned with hearing; shaped like triangular tube

cone-shaped core of bone that houses the spiral ganglion, which consists of cell bodies of the first sensory neuronsin the auditory relay

the roof of the cochlear duct

created by vibration

the central section of the bony labrinth; the utricle and saccule are the membranous structures within the what?

found in each temporal bone

ability to sense the position of the head relative to gravity or to sense acceleration or deceleration

muscular response to restore the body and its parts to their normal position when they they have been displaced; caused by stimuli of a macula and impulses from proprioceptors and from the eyes

needed to maintain balance when the head or body is rotated or suddenly moved; able to detect changes both in direction and rate at which movement occurs

gelatinous cap in which the hair cells of each crista are embedded

give some protection against foreign objects entering they eye; cosmetic purpose

consist of voluntary muscle and skin with tarsal plate

opening between the eyelids

where the upper and lower eyelids join

structures that secrete tears and drain them from the surface of the eyeball

size and shape of a small almond; located at the upper, outer margin of each orbit; approximately a dozen small ducts lead from each gland; drain tears onto the conjuctiva

small channels that empty into lacrimal sac

located in a groove in the lacrimal bone

small tubes that extend from the lacrimal sac into the inferior meatus of the nose

skeletal muscles that attach to the outside of the eyeball and to the bones of the orbit

smooth muscles located within the eye

regulates size of pupil; amount of light; colored part of the eye; consists of circular and radial smooth muscle fibers that form a doughnut shaped structure; attaches to the ciliary body

contros the shape of the lens

the outer layer of the eyeball

tough, white fibruos tissue of the eyeball

the transparent anterior portion that lies over the iris; no blood vessels found in the cornea or in the lens of the eye

ring shaped venous sinus found deep within the anterior portion of the sclera at its juction with the cornea of the eye

pigmented membrane lining more than two thirds of the posterior fibrous out coat of eye

thickening of choroidd, fits between anterior margin of retina and posterior margin of iris; ciliary muscle lies in anterior part of ciliary body; ciliary processes fold in ciliary body

attached to the ciliary processes and blends with the elastic capsule of the lens, to hold it in place

space anterior to the iris and posterior to the cornea

lies in from of the lens; has two subdivisions

critical to normal visual function

second cranial nerve (CN II) extends from the eyeball to the brain

all axons of these neurons extend back to the optic disk; part of the sclera, which contains perforations through which the fibers emerge from the eyeballs as the optic nerve

less nermerous than rods; most densely concentrated in the fovea centralis in the macula lutea; low light

absent from the fovea and macula; increased in density toward the periphery of the retina; regular light

visual receptors, sensitive to light rays

Made up of an outer layer of pigmented epithelium (pigmented retina) and an inner layer of nervous tissue (sensory retina)

movement of the two eyeballs inward so that their visual axes come together at the object view

pupil constricts in bight light

constriction of pupil that occurs with accommodation of the lens in near vision

muscles of iris are important to formation of a clear retinal image

increase in curvature of the lens to achieve the greater refraction needed for near vision

deflection, or bending of light rays produced by light rays passing obilquely from one transparent medium into anothe of different optical density

small space posterior to the iris and anterior to the lens

larger than the anterior cavity; occupies all the space posterior to the lens, suspensory ligament, and ciliary body

fills both chambers of the anterior cavity; clear, watery fluid that oftens leaks out when the eye is injured; formed from blood in capillaries located in the ciliary body

fills the posterior cavity; semi-solid material; helps to maintain sufficient intraocular pressure, with aqueous humor, to give the eyeball its shape