the brain’s processing of sensory input & motor output is cyclical rather than linear...

The brain’s processing of sensory input & motor output is cyclical rather than linear

Sensations: stimulus to the brainPerceptions: interpretation of sensory info

Sensor Receptors:

• Exteroreceptors- detect stimuli outside the body- Heat- Light- Pressure- Chemicals

• Interoreceptors- detect stimuli within the body- Blood pressure- Body position

Sensory receptors transduce stimulus energy transmit signals to

the nervous system

• Sensory Transduction• Amplification• Transmission• Integration

• Chemoreception- Taste- Smell

• Electromagnetic receptors- Photoreceptors- Infrared receptors - Lateral line - Electroreception

• Nocioceptors• Mechanoreceptors:

- Hearing- Balance

• Thermoreceptors

respond to chemicals in an aqueous solutionfood dissolved in salivaairborne chemicals dissolved in mucous membrane

Taste and smell are involved with specific receptor cells called chemoreceptors

Chemoreception: Taste

Salty- metallic ions

Sweet- sugarSweet- sugar

Sour- HSour- H++

Bitter- alkaloidBitter- alkaloid

Why are they important?

Gustatory pathway:Facial nerve (afferent) 2/3 anterior portion of tongueGlossophyngeal posterior 1/3 of tongueVagus nerve- few taste buds on epiglottis an pharynxThese afferent fibers synapse in medullathalamusgustatory cortex in parietal lobes and fibers to hypothalamus in limbic system

• Find a mate• Detect food

Moth Chemosense

male

Jacobson’s organ: • The tongue flicks out, picking up odors

and carrying them to the roof of the mouth into contact this sensory receptor

Heat receptor:

• heat-detecting sensors concentrated as two large pits between their nostril and eyes

• Found in pit vipers, as well as some boas and pythons

• Detects small differences in temperature (as slight as 0.02 oC)

• Used to locate and capture warm-blooded prey at night.

Sensory receptors are categorized by the type of energy they transduce

A diversity of photoreceptors has evolved among invertebrates

• Eye cups are among the simplest photoreceptors– Detect light intensity and direction — no image

formation.– The movement

of a planarian is integrated with photoreception.

• Image-forming eyes.

– Compound eyes of insects and crustaceans.• Each eye consists

of ommatidia, each with its own light-focusing lens.

• This type of eye is very good at detecting movement.

• Single-lens eyes of invertebrates such as jellies, polychaetes, spiders, and mollusks.

– The eye of an octopus works much like a camera and is similar to the vertebrate eye.

Vertebrates have single-lens eyes

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• Is structurally analogous to the invertebrate single-lens eye.

Fig. 49.9

Fibrous tunic- sclera and cornea (outer most layer)

Composed of dense avascular connective tissue

Vascular tunic- uvea: choroid, cilliary body, iris, pupil (middle layer)

Choroid- rich vascular nutritive layer; contains a dark pigment

that prevents light scattering within the eye

Cilliary body- lens is attached; contains muscles that change the

lenses shape

Iris- pigmented ring of muscular tissue composed of circular

and radial muscles

• reflex contraction of circular muscle in bright light (small dia of pupil)

• reflex contraction of radial muscle in dim light (large dia of pupil)

Pupil- central hole in iris

Sensory tunic- retina (inner most layer)

Photoreceptors:

• rods (dim light, contains pigment rhodopsin) and

• Cones (color vision, not evenly distributed, concentrated in fovea)

Optic disc- blind spot because its where optic nerve leaves the eyeball (no rods or cones)

Macula lutea- yellow spot, area of high cone

Fovea centralis- in center of macula lutea, contains only cones, area of greatest visual acuity

Vitreous humor- behind lens, gel-like substance with fine collagenic fibrils imbedded in as viscous ground substance- binds with water

• transmits light• supports the posterior surface of the lens and

holds the neural retina firmly against pigmented layer

• contributes to intraoccular pressure, helping to counter act the pulling force of the extrinsic eye muscles

Aqueous humor- in front of lens, anterior segment, watery fluid

• Supplies cornea and lens with nutrients• Helps to maintain the shape of the eye• Produced and renewed every 4 hrs by the

cilliary body

Lens- transparent biconvex structure, flexible• Attached by suspensory ligaments to cilliary

body• focuses image onto retina• changes lens thickness to allow light to be

properly focused onto retina

Coarse Fixed FocusingCoarse Fixed Focusing• Cornea ShapeCornea Shape

AccommodationAccommodation- adjust configuration of- adjust configuration of • Lens ShapeLens Shape• Pupil SizePupil Size

refraction

Focusing on a Near Object

Focusing on a Far Object

• Photoreceptors of the retina.

– About 125 million rod cells.• Rod cells are light sensitive but do not distinguish

colors.

– About 6 million cone cells.• Not as light sensitive as rods but provide color

vision.• Most highly concentrated on the fovea – an area of

the retina that lacks rods.


The light-absorbing pigment rhodopsin triggers a signal-transduction pathway


• Rhodopsin (retinal + opsin) is the visual pigment of rods.

• The absorption of light by rhodopsin initiates a signal-transduction pathway.

Fig. 49.13

• Color reception is more complex than the rhodopsin mechanism.

– There are three subclasses of cone cells each with its own type of photopsin.• Color perception is based on the brain’s

analysis of the relative responses of each type of cone.

– In humans, colorblindness is due to a deficiency, or absence, of one or more photopsins.• Inherited as an X-linked trait.


The retina assists the cerebral cortex in processing visual

information


• Visual processing begins with rods and cones synapsing with bipolar cells.

– Bipolar cells synapse with ganglion cells.

• Visual processing in the retina also involves horizontal cells and amacrine cells.


Fig. 49.15

• Vertical pathway: photoreceptors bipolar cells ganglion cells axons.


• Lateral pathways:

– Photoreceptors horizontal cells other photoreceptors.• Results in lateral inhibition.

– More distance photoreceptors and bipolar cells are inhibited sharpens edges and enhances contrast in the image.

– Photoreceptors bipolar cells amacrine cells ganglion cells.• Also results in lateral inhibition, this time of the

ganglion cells.


• The outer ear includes the external pinna and the auditory canal.

– Collects sound waves and channels them to the tympanic membrane.

The mammalian hearing organ is within the ear


• From the tympanic membrane sound waves are transmitted through the middle ear.

– Malleus incus stapes.

– From the stapes the sound wave is transmitted to the oval window and on to the inner ear.

– Eustachian tube connects the middle ear with the pharynx.


external auditory

canal

tympanic membrane

eustachian tube

malleus

incus

stapes

round window

oval window

• The inner ear consists of a labyrinth of channels housed within the temporal bone.

– The cochlea is the part of the inner ear concerned with hearing.• Structurally it consists of the upper vestibular

canal and the lower tympanic canal, which are separated by the cochlear duct.

• The vestibular and tympanic canals are filled with perilymph.


Biology 100Biology 100Human BiologyHuman Biology

cochlea

saccule

utricle

semicircular canals

auditory nerve

– The cochlear duct is filled with endolymph.

– The organ of Corti rests on the basilar membrane.• The tectorial membrane rests atop the hair

cells of the organ of Corti.


• From inner ear structure to a sensory impulse: follow the vibrations.

– The round window functions to dissipate the vibrations.

• Vibrations in the cochlear fluid basilar membrane vibrates hair cells brush against the tectorial membrane generation of an action potential in a sensory neuron.



Fig. 49.18

• Pitch is based on the location of the hair cells that depolarize.

• Volume is determined by the amplitude of the sound wave.


• Behind the oval window is a vestibule that contains the utricle and saccule.

– The utricle opens into three semicircular canals.

The inner ear also contains the organs of equilibrium


Static Balance – utricle and sacule

Dynamic Balance- semicircular canals

(semicircular canal)

cupula

hair cells

Endolymph fluid

Vestibular nerve fibers

(semicircular canal)

The effect of gravitational pull on the macula receptor cell in the utricle

• Fishes and amphibians lack cochleae, eardrums, and openings to the outside.

– However, they have saccules, utricles, and semicircular canals.

A lateral line system and inner ear detect pressure waves in most fishes and aquatic amphibians


• Statocysts are mechanoreceptors that function in an invertebrates sense of equilibrium.

– Statocysts function is similar to that of the mammalian utricle and saccule.

Many invertebrates have gravity sensors and are sound-sensitive

Fig. 49.21

• Sound sensitivity in insects depends on body hairs that vibrate in response to sound waves.– Different hairs respond to different frequencies.

• Many insects have a tympanic membrane stretched over a hollow chamber.


Fig. 49.22

pores

Detects weak magnetic fields produced by other fish

the brain’s processing of sensory input & motor output is cyclical rather than linear...

Documents

taste slide

sensory receptor slide

limbic system slide

sensory receptors

eye cilliary body lens

type of eye

body heat

invertebrate singlelens