A&P Unit 5: Nervous System, Senses, Motor and Sensory Pathways

difference between general and special senses

general senses are widespread and simple while special senses are localized and complex

olfactory epithelium

olfactory receptor, supporting, and basal cells

function of olfactory receptor cells

odor detection

structure of olfactory receptor cells

bipolar neurons with cilia

how many odorant molecules are needed to stimulated smell

only a few molecules

what properties must an odorant have

it must be volatile and lipid-soluble

how does smelling produce an action potential

odorants bind to receptors causing depolarization

does smell adapt quickly or slowly

it adapts rapidly

olfactory pathway

receptors → bulb → tract → cortex

location of gustatory receptors

taste buds on the tongue

what cells form taste buds

gustatory, supporting, and basal cells

structure of gustatory cells

they have microvilli that detect chemicals

4 types of papillae

filiform, fungiform, circumvallate, and foliate

5 basic tastes

sweet, sour, salty, bitter, and umami

how does taste create an action potential

chemicals open ion channels causing depolarization

what produces bitter, sour, salty, and sweet tastes

poisons, acids, minerals, and sugar

does taste adapt quickly or slowly

tastes adapts slowly

gustatory pathway

taste buds → cranial nerves → thalamus → cortex

three senses that affect taste

smell, temperature, and texture

anosmia

loss of the sense of smell

palpebral conjunctiva

lines the eyelids

bulbar conjunctiva

covers the eyeball

cause of bloodshot eyes

dilated blood vessels

gland that produces tears

lacrimal gland

what do tears contain

water, salts, antibodies, and lysozyme

function of extrinsic eye muscles

they move the eyeball

three layers of the eye

fibrous, vascular, and neural layers

pathway of light through the eye

cornea → pupil → lens → retina

what area gives greatest visual acuity

fovea centralis

what are rods used for

dim-light and black-and-white vision

what are cones used for

color and sharp vision

blind spot

optic disk

the three types of cones

red, green, and blue

function of the lens

it focuses light onto the retina

location of aqueous humor

anterior cavity

location of vitreous body

vitreous chamber

glaucoma

increased eye pressure

refraction

the bending of light

accommodation

the lens changing shape to focus

what is the near point of vision

the closest clear distance of vision

presbyopia

age-related loss of accommodation

what is an emmetropic eye

a normal eye

myopia

nearsightedness

hyperopia

farsightedness

astigmatism

uneven curvature of the eye

why do humans have binocular vision

our eyes face forward

convergence

eyes turning inward for near vision

photopigments

light-sensitive molecules in rods and cones

how does light bleach photopigment

it separates retinal from opsin

what is the visual pathway

retina → optic nerve → thalamus → visual cortex

function of the external ear

collects sound waves

function of the middle ear

amplifies sound

function of the inner ear

converts sound to nerve signals and controls balance

structures that make up the external ear

auricle and auditory canal

structures that make up the middle ear

malleus, incus, and stapes

function of auditory tube

equalizes pressure

perilymph

fluid in the bony labyrinth

endolymph

fluid in the membranous labyrinth

function of the cochlea

detects sound

what determines pitch

sound frequency

what determines loudness

sound amplitude

cause of a nerve impulse in hearing

hair cell movement in the cochlea

sensation

conscious or subconscious awareness of changes in external or internal environment

process of sensation

sensation occurs when a stimulus activates a sensory receptor, is converted into a nerve impulse, transmitted through sensory neurons to the CNS, and interpreted by the somatosensory cortex as a conscious sensation

general senses

somatic sensations and visceral sensation

special senses

smell, taste, vision, hearing, and equilibrium or balance

exteroreceptors

located near external surface and responds to external stimuli

interoreceptors

located in blood vessels, organs, and nervous system; not consciously percieved

proprioceptors

located muscles, tendons, joints, and inner ear; provide information about body position and joint movement

mechanoreceptors

respond to pressure, touch, motion, sound, vibration, and gravity; sensitive to deformation

thermoreceptors

detect changes in temperature; respond to heat, cold, infrared radiation

nociceptors

detect chemicals released in response to tissue damage due to intense thermal , mechanical, or chemical stimuli

photoreceptors

activated by light

chemoreceptors

detect chemicals in mouth, nose, and body fluids

osmoreceptors

detect osmotic pressure (concentration of solutes that cannot readily cross cell membrane) of body fluids

types of receptors that are rapidly adapting

receptors that detect pressure, touch, and smell

types of receptors that are slowly adapting

receptors that detect pain, body position, and chemical composition of the blood

parts of somatic sensations

sensory receptors in the skin (cutaneous sensations), muscles, tendons, joints, and in the inner ear

modalities of somatic sensations

tactile, thermal, pain, and proprioceptive sensations

proprioceptive sensations

allows perception of position and movement of body parts

visceral senses

provide information about conditions within internal organs

sustained stimulation results in

decreased amplitude of generator or receptor potential

even though stimulus persists,

frequency of nerve impulses to cerebral cortex decreases and perception fades

tactile sensations

touch, pressure, vibration, itch, and tickle

tactile receptors in the skin

Meissner corpuscles, hair root plexuses, Merkel discs, Ruffini corpuscles, pacinian corpuscles, and free nerve endings

hair root plexuses

rapidly adapting touch receptors found in the hairy skin that detect movements on skin surface that disturb hairs

thermal sensations

cold receptors and warm receptors

slow pain

chronic, burning, aching, or throbbing pain that gradually increases in intensity; occurs slowly because nerve impulses travel along small diameter unmyelinated fibers

fast pain

acute, sharp, or pricking pain that occurs rapidly because nerve impulses travel along medium diameter myelinated fiber

referred pain

pain is felt in or just deep to the skin that overlies the stimulated organ or in a surface area far from the stimulated organ

superficial somatic pain

pain from stimulation of nociceptors in the skin

deep somatic pain

pain from stimulation of nociceptors in skeletal muscles, joint, tendons, and fascia

visceral pain

pain from stimulation of nociceptors in visceral organs

weight discrimination

the ability to judge how heavy an object is to help determine the amount of muscular force needed to life an object

three types of proprioceptors

muscle spindles, tendon organs, and joint kinesthetic receptors

where are muscle spindles located

interspersed among skeletal muscle fibers and aligned parallel to them

structure of a muscle spindle

several slowly adapting sensory nerve endings wrapped around 3–10 specialized muscle fibers enclosed in a connective tissue capsule

what do muscle spindles measure

changes in muscle length

muscle spindles are involved in

the stretch reflex

what role do muscle spindles play in muscle tone

they help maintain a small amount of contraction when the muscle is at rest