chapter 18 - specialized sensory receptors - taste smell vision

• sensory system

• sensory system

what is responsible for providing the brain with vital information regarding both the external and internal environment?

• general senses and special senses

what are the two divisions of the sensory system?

general senses

• a division of the sensory system

• includes touch, pressure, vibration, stretch, pain, and temperature

special senses

• a division of the sensory system

• includes vision, hearing, equilibrium, taste, and smell

sensory receptors

• responsible for monitoring the body's internal and external environment

stimulus

• a change in the environment that activates a sensory receptor

sensory neuron

• electrical signal (nerve impulse) that conveys the information to the spinal cord or brain where it is integrated and interpreted, and appropriate responses are initiated

• because they convert one type of energy (for example, light energy or thermal energy) and transduce it (changes it) into an electrical impulse (receptor potential or an action potential by a neuron)

why are sensory receptors often referred to as transducers?

chemoreceptors

• sensory receptors that detect the presence of specific chemicals

mechanoreceptors

• sensory receptors that are stimulated by changes in their shape which allows them to respond to touch, pressure, vibration, and stretch

thermoreceptors

• sensory receptors that detect changes in temperature

nociceptors

• sensory receptors that detect pain (they are stimulated by conditions that potentially harm the body)

special sense organs

• complex structures located on the head with a high concentration of sensory receptors designed to detect environmental conditions associated with these senses

filiform papilla

• smaller tufted papilla

• found over entire surface of the tongue

• no taste receptors but do have touch receptors

• tufted shape produces friction to help tongue push food

fungiform papilla

• smaller, mushroom shaped

• scattered over entire surface of tongue

• surrounded by a shallower depression

• most contain taste buds

circumvallate papilla

• large and blunt top like a pencil eraser

• in a row forming a V shape along posterior edge of tongue

• surrounded by a deep depression where dissolved molecules collect

• all have taste buds

taste buds

• chemoreceptors for taste

• embedded in wall of papilla facing depression

• four primary tastes: sweet, salt, sour, and bitter

• somewhat associated with specific regions of tongue

gustation

• sense of taste

umami

• additional taste sensation describe as the pleasant taste of savory foods, especially meat (savoriness)

• insula

what lobe of the brain perceives taste?

• slow adapting receptors

• are taste receptors slow or fast adapting?

gustatory pathway

...

olfactory tract

• neurons synapse with olfactory receptor neurons then carry sensory information to the brain

olfactory bulb

• above ethmoid bone within CNS

• location of synapses between sensory receptor neurons and olfactory tract neurons

olfactory nerve

• bundles of axons from olfactory receptor cells

• form CN 1

olfactory glands

• secrete mucus layer covering dendrites

olfactory receptor cells

• bipolar neurons located in the nasal epithelium

• chemoreceptor (which detect odor molecules dissolved in the mucus)

the sense of smell has what type of sensory receptor?

olfactory cilia

• projections extending out into mucus layer

• site of binding with dissolved molecules

olfactory epithelium

• area of nasal epithelium approximately the size of a postage stamp

• houses olfactory receptor neurons

olfaction

• sense of smell

• amygdala

what part of the limbic system in the brain is closely associated with the sense of smell?

• the olfactory cortex in the frontal and temporal lobes of the brain

where does the olfactory nerves convey the sensory information from the olfactory bulbs to?

lacrimal gland

• produced tears

lacrimal puncta

• two small openings in medial corner of eye

• tears collecting in the medial corner drain through it to enter the lacrimal canaliculi

lacrimal canaliculi

• two small canals

• receive tears from puncta and deliver them to lacrimal sac

lacrimal sac

• collects tears draining away from eye in lacrimal canaliculi

• empties into nasolacrimal duct

nasolacrimal duct

• receives tears from lacrimal sac

• tears drain into inferior meatus of nasal cavity

tear duct

• ducts from lacrimal gland

• carry tears to be released behind upper eyelid

• tears then flow across anterior eye from superior lateral corner to medial corner

eyes

• responsible for sense of vision

photoreceptors

• sensory receptors in the eyes (rods and cones)

• activated by light energy

• located in the retina

rods

• photoreceptor that is active in dim light

• perceives in shades of gray (no color) and images are not sharp (blurred)

cones

• photoreceptor that is active only in bright light

• perceives colors (red, green, and blue) and produces sharper images

connecting neurons

• several layers of neurons that connect photoreceptor cells to the optic nerve

• true

true or false? humans have binocular and stereoscopic vision and are capable of depth perception and distinguishing colors

• about 1/6th

how much of the eyeball is exposed?

tunic

• term meaning coat or covering

• the fibrous tunic, vascular tunic, and neural tunic

what are the three layers or tunics that makeup the wall of the eyeball?

fibrous tunic

• outer layer of the eye

• composed of the sclera and cornea

vascular tunic

• middle layer of the eye

• composed of the choroid, ciliary body, and iris

neural tunic

• innermost layer of the eye

• composed of the ora serrata and retina

eyebrow

• also called supercilia

• prevents sweat from flowing down face and into eye

upper and lower eyelid

• also called palpebra

• blinking spreads tears across conjunctiva and helps to remove fine particles like dust

• narrowing or shutting tightly protects eyeball from strong light and external environment

palpebral conjunctiva

• thin, transparent mucous membrane

• lines inner surface of each eyelid

• continues with bulbar conjunctiva to prevent dirt and dust particles from reaching eyeball

eyelashes

• these are short hairs, but may be also called cilia

• found along edges of both eyelids

• help to prevent debris from reaching the eyeball

bulbar conjunctiva

• thin, transparent mucous membrane

• covers and protects the anterior surface of eyeball

• continues with palpebral conjunctiva

accessory structures

• they function to protect the eyeball, but play no role in vision

tarsal or meibomian glands

• oil glands or sebaceous glands that secrete an oily substance that keeps eyelids from sticking to each other

• embedded at the base of eye lashes