anatomy 2020: chapter 14 somatic nervous system

somatic nervous system and special senses

special senses

complex anatomical structures, has a specialized receptor cell, includes olfaction, gustation, vision, hearing, linear acceleration, gravity, rotation

general senses

no complicated anatomical structures, uses free nerve endings or encapsulated endings, includes touch, pain, temperature, pressure, vibration, proprioception

chemoreceptors

respond to chemicals

mechanoreceptors

Sensory receptors stimulated by movement

photoreceptors

respond to light

olfaction

sense of smell or detection of odorants

olfactory organ

olfactory epithelium lining the superior portion of nasal cavity

olfactory sensory neurons

highly modified neurons that contain odorant binding receptors on their dendrites, extend into the nasal cavity, their axons form olfactory nerve (I), can regenerate

olfactory epithelium

supports the olfactory sensory neurons, produces mucus to help trap odorants

odorants

airborne chemicals that are detected as odors

processing centers for olfaction include

olfactory cortex, hypothalamus, and limbic system

olfactory nerve (I)

sensory neuron, transmits olfaction to olfactory cortex, hypothalamus, and limbic system

G-protein coupled receptors

A signal receptor protein in the plasma membrane that responds to the binding of a signaling molecule by activating a G protein. Also called a G protein-linked receptor.

G protein

a protein coupled to a receptors, acts as a bridge between the 1st messenger and 2nd messenger

second messenger

acts as a signal molecule in the cytoplasm, often cAMP or calcium ion

first messenger

the chemical messenger that binds to the receptor

gustation

sense of taste (sour, salty, bitter, sweet, umami, and oleogustus) or detection of tastants

sour

hydrogen ions enter ion channels and depolarize gustatory sensory neurons

salty

sodium ions enter ion channels and depolarize gustatory sensory neurons

sweet

monosaccharides bind to G-protein coupled receptors on gustatory sensory neurons

bitter

alkaloids bind to G-protein coupled receptors on gustatory sensory neurons and can depolarize or hyperpolarize the cell

umami

"savory" the amino acid L-glutamate binds to G-protein coupled receptors on gustatory sensory neurons

Oleogustus

the taste of rancid fats

lingual papillae

rough projections that provide friction and can be involved in taste reception (if they contain taste buds)

filiform papillae

located on the tip of the tongue, provides friction (gets food into the mouth)

fungiform papillae

located middle of the tongue, contain 5 taste buds, has dual function of friction and taste

Vallate papillae (circumvallate)

located at the back of the tongue, contain 100 taste buds - taste is primary function

foliate papillae

on side walls of tongue and contain taste buds

taste buds

located on fungiform, foliate, and circumvallate papillae, contain gustatory receptor cells, transitional cells, and basal (stem) cells

gustatory cells

located on taste buds, have microvilli to increase contact with tastants, synapse onto sensory neurons, replaced about every 10 days

salt and sour receptors

chemically-gated ion channels

sweet, bitter, and umami

G protein coupled receptors sensitive to certain molecules

cranial nerves involved in gustation

VII, IX, and X

processing center for gustation

gustatory cortex (insula lobe)

ceruminous glands

located lining the external auditory canal, produce cerumen (ear wax)

Perilymph

fluid around bony labyrinth, stimulates auditory hair cells (hearing)

endolymph

fluid inside membranous labyrinth, stimulates hair cells in the ampulla (rotation)

hair cells

mechanoreceptor cells of the inner ear involved in sensing hearing, rotation, linear acceleration, and gravity

spiral organ (organ of corti)

located in the cochlear duct, contains hearing receptor cells

tectorial membrane

part of the spiral organ, hair cells bump up against the tectorial membrane when pressure waves move through the perilymph

basilar membrane

part of the spiral organ, moves in response to pressure waves in the perilymph, bumps hair cells against the tectorial membrane causing a signal to be sent to the sensory neurons

tympanic membrane

eardrum

round window

located just below the oval window; equalize pressure in the inner ear

auditory ossicles

malleus, incus, stapes - transmit vibrations and amplify the signal from tympanic membrane to inner ear

oval window

stapes of the auditory ossicles bump against the oval window which then converts sound waves into pressure waves in the perilymph

frequency

or pitch, determined by where the cochlear duct is stimulated

intensity

or volume, determined by how many hair cells are stimulated

semicircular canals

contains the ampullae, detects rotation

ampulla

located in the semicircular canals, contains hair cells that are displaced by endolymph triggering rotation information to be sent to sensory neuron

vestibule

contains maculae, detects linear acceleration and gravity

maculae

located in the vestibule, contains hair cells that are displaced by the otolith triggering linear acceleration and gravity information to be sent to the sensory neuron

vestibulocochlear nerve (VIII)

sends auditory, linear acceleration, gravity, and rotation information to the brain for processing

iris

pupillary muscle, controls the amount of light entering the eye

aqueous humor

circulates within the chambers of the eye providing nutrients, oxygen, and waste removal

ciliary body

circular muscle that controls the shape of the lens for focusing

ciliary zonule (suspensory ligament)

connect the ciliary body to the lens

lens

focuses photons (light) onto retina

vitreous humor

gelatinous mass located in the posterior cavity, stabilizes the shape of the eye and holds the retina in place

accommodation

changing the shape of the lens in order to focus the image

for close vision

ciliary muscle contracts > ciliary zonule are loose > lens has round shape > more refractive power (bend light)

for distance vision

ciliary muscle relaxes > ciliary zonule are tight > lens has flat shape > less refractive power

retina

neural tunic, contains photoreceptor cells, and neurons

photoreceptor cells

rod and cone cells that respond to photons of different wavelengths based on different opsin pigments

rod cells

black and white vision, peripheral vision, contain rhodopsin

cone cells

color vision, most accurate vision, concentrated in the fovea centralis

cranial nerve involved in vision

optic nerve (II)

processing center for vision

visual cortex in the occipital lobe

steps of "vision" in a rod cell

1. photon triggers retinal to be linear and opsin to activate
2. opsin activation triggers influx of Na+, causing the rod cell to stimulate the sensory neurons
3. bleaching occurs

bleaching

1. opsin and retinal separate (rod can't be stimulated again)
2. retinal converts back to bent shape
3. retinal is recombines with opsin and rhodopsin (the rod cell) is ready to be stimulated