Biology 30 - Chapter 14

sensory receptors

supply CNS with info about the environment.

located on the dendrites of sensory neurons

detect stimulus then converts stimulus to action potentials and info is sent to cerebrum to be interpreted

sensory adaptation

receptor has become accustomed to the stimulus and the neurons stop firing

taste receptors

located on taste buds. stimulated by dissolving chemicals which then bind to receptors and stimulate an AP in a sensory neuron. chemicals are then interpreted by the parietal lobe as a taste

smell receptors

located in your nose. stimulated when chemicals in the air dissolve in mucus and bind to the receptor which then triggers an AP and sens a message to the olfactory centre.

mechanical receptors

detect touch or pressure on the skin

proprioreceptors

sense stretching and pressure inside the body. in vessels they respond to blood pressure and signal the medulla oblongata

sensing temperature (warm and cold receptors)

warm receptors respond to temperatures above 25 C. cold receptors responds to temperatures between 10 and 20 C.

sensing pain (pain receptors/nocireceptors)

stimulated when tissues are damaged and are responsive to temp and chemicals. they do not adapt. they can become more sensitive.

Three separate layers of the eye

1. sclera

2. choroid

3. retina

sclera

tough, white outmost layer. protective layer

choroid

middle layer of tissue, contains many blood vessels that nourish the retina

retina

contains photoreceptors which have pigment molecules that absorb light.

path of light

1. cornea

2. aqueous humour

3. lens

4. vitreous humour

the cornea

front transparent part of the sclera. bends light towards the pupil. absorbs oxygen from gases dissolved in tears

aqueous humour

clear watery liquid. supplies cornea with nutrients and removes wastes, provides the lens with oxygen and protects it

iris

thin circular muscle, controls the size of the pupil and the amount of light that enters the eye. gives eyes its characteristic color

lens

focuses the image on the retina, changes shape when viewing objects. it is flat when objects are far away. bent when objects are close. ciliary muscles and ligaments cause it to bend.

vitreous humour

jelly like liquid, maintains the eyeball and scatters light onto the retina

retina

contains two types of photoreceptors and the fovea centralis

photo receptors

detect light stimulus (rods or cones)

rods

stimulated in low intensity light and by movement. detects black and white. contains rhodopsin ‘visual purple’ which is made from vitamin a.

cones

are stimulated in bright light and detect colour

fovea centralis

cones are densely packed together. center of the visual field.

blind spot

where the optic nerve is attached, contains no rods or cones

when does action potential begin in the eye?

AP begins when the rods and cones are hit with light. stimulus is sent to bipolar cells then to the optic nerve then to the optic chiasma then to the thalamus then to the occipital lobe.

1. rods and cones hit with light

2. bipolar cells

3. optic nerve

4. optic chiasma

5. thalamus

6. occipital lobe

visual field

created by the brain interpreting impulses. right occipital interprets left side of visual field. the left interprets the right.

accomodation

ability of the lens to bend, decreases with age as lens becomes harder

when viewing close objects:

1. ciliary muscles contract

2. lens bends causing a greater degree of bending the light

3. the pupil constricts

when viewing objects far away:

1. ciliary muscles relax

2. lens becomes flat

3. pupil dilates

afterimages

produced after you have looked at something. there are two different types.

1. positive: when you look at a bright light

2. negative: bright colours for a period of time

color blindness

occurs when the cones lack one of the opsins. genetic

glaucoma

caused by the build up of excess aqueous humour, pressure builds up causing vision loss. surgery can remove the fluid.

cataracts

lens becomes cloudy and vision is reduced. surgery can replace the lens and fix it.

astigmatism

caused by an irregularly shaped cornea or lens. requires specially ground assymetrical lens

hyperopia

far sightedness. distant objects are clear, but close is blurred. eye is too short so image is brought into focus behind the retina. biconvex lens to fix

myopia

near sightedness. near objects are clear while distant is blurred. eye is too long, image is brought into focus in front of the retina. biconcave lens.

two primary functions of the ear

hearing and equilibrium

three sections of the ear

outer, middle, inner

outer ear consists of…

pinna and auditory canal

pinna

external ear flap, collects sound

auditory canal

carries sound to the tympanic membrane

middle ear consists of the …

tympanic membrane, ossicles, oval window, eustachian tube

tympanic membrane (eardrum)

semi-transparent membrane. vibrates when sound waves strike it

ossicles

three bones:

1. hammer (malleus)

2. anvil (incus)

3. stirrup (stapes)

   transfers sound waves from tympanic membrane to the oval window. stapes strikes the oval window.

oval window

oval shaped membrane that covers a hole

eustachian tube

permits the equalization of air pressure

inner ear consists of the …

cochlea, semicircular valves, vestibule

cochlea

converts fluid waves to electrical impulses, fluid waves press into the basilar membrane

organ of corti

converts fluid waves to electrical impulses (same as cochlea). everytime a hair cell bends, a sensory neuron depolarizes. they bend when they are pushed against a tectorial membrane

semicircular canals

info about your body position when moving, involved in dynamic equilibrium. contains hair cells that bend when fluid inside canals moves causing an AP which is then sent to cerebellum for interpretation.

vestibule

head position (static equilibrium) which is sent to the cerebellum for interpretation. consists of saccule and utricle. the hair cells are in a gelatinous material and bend when the gel moves

If the head is tilted…

otoliths move causing cilia to bend and hair cells to depolarize

two types of hearing loss

conductive and sensorineural

conductive hearing loss

result of build up wax, ear infection, punctured ear drum. it can be corrected.

sensorineural hearing loss

result of damaged auditory nerve, dead hair cells, damaged hair cells.

cochlear implants

restore hearing, are for sensorineural hearing loss. converts sound waves into electrical impulses

hearing aids

amplify sound