chapter 18 - specialized sensory receptors - taste smell vision

- 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