DCAP Ch 14: Somatic Nervous System

sensation

the taking in of sensory input

integration

Thinking and deciding what to do next

response

What your muscles actually do (motor output)

Sensation (vs.)

The activation of sensory receptor cells at the level of the stimulus

Perception (vs.)

The central processing of sensory information into a meaningful pattern

Receptors

Cells of structures that detect sensations

What directly changes a receptor?

A stimulus

What detects changes and relay them?

Transmembrane proteins

What opens to relay the changes?

Ion channels

What is generated by transmembrane proteins?

Action potentials

ligand

a chemical that binds to a transmembrane receptor protein

Free nerve ending

dendrites embedded in tissue that would receive a stimulus (ex: pain, temperature)

encapsulated ending

sensory nerve ending is contained in connective tissue that enhances their sensitivity (ex: laminated corpuscles detector pressure and touch)

specialized receptor

has distinct components that intercept a specific type of stimulus (ex: photoreceptors detect light in retina)

exteroceptor

located near a stimulus in the external environment (ex: skin)

interoceptor

interprets stimuli from internal organs and tissues (ex: aorta walls detect bp)

proprioceptor

located near a moving part of the body (ex: muscle)

chemoreceptor

interprets chemical stimuli (ex: taste, smell)

osmoreceptor

responds to concentration of body fluids (ex: hypothalamus detects water balance)

thermoreceptor

reacts to special physical stimuli (heat or cold)

nociceptor

interprets the presence of chemicals from tissue damage (ex: pain, intensity)

mechanoreceptor

interprets physical stimuli (ex: balance, vibration, sound, pressure)

general sense

A type of sensory perception that includes sensations such as touch, temperature, pain, and proprioception, as opposed to special senses like vision and hearing.

proprioception

body position

kinesthesia

body movement

visceral sense

trunk organ sensations like ‘stomach fullness’

somatosensation

group of general senses which includes touch, proprioception, and interoception

Merkel’s discs

mechanoreceptors in the epidermal-dermal junction and mucosal membranes that detect low frequency vibrations

Ruffini’s corpuscle

a type of mechanoreceptor located in the dermis and joint capsules that responds to deep pressure and high frequency vibration; also referred to as a bulbous corpuscle

Pacinian corpuscle

a type of mechanoreceptor located deep in the dermis and subcutaneous tissue that detects high frequency vibrations and pressure; also called a lamellated corpuscle

Krause end bulb

a type of mechanoreceptor found in the dermis and mucous membranes that is sensitive to cold temperatures

Golgi tendon organ

Proprioceptor in line with tendons that detects stretchand tension in muscles, helping to prevent excessive force during contraction

muscle spindle

a type of proprioceptor located within muscles that detects changes in muscle length and the rate of stretch, playing a crucial role in the regulation of muscle tone and reflexes

interoceptors

in walls of visceral organs and vessels to detect internal changes, such as osmoreceptors, humoral receptors, and glucoreceptors that monitor internal conditions and physiological states, providing information about the body's internal environment.

Special senses

sensory modalities that provide information about the environment through specialized organs, including vision, hearing, taste, smell, and balance

Papillae

small projections on the tongue that contain taste buds and are involved in the sensation of taste.

taste buds

sensory receptors located within the papillae of the tongue that detect taste stimuli, allowing the perception of different flavors such as sweet, sour, salty, bitter, and umami

gustatory receptor cells

specialized sensory cells responsible for detecting taste stimuli and transmitting taste information to the brain.

taste nerves

facial, glossopharyngeal, vagus nerves

Olfactory epithelium

Layer the superior nasal cavity and contains bipolar sensory neurons

olfactory sensory neurons

nasal nerves that extend from the olfactory epithelium into the mucus lining

olfactory bulb

region in the brain where axons of the olfactory neurons lead

Auricle

the fleshy outer ‘ear’ structure

external acoustic meatus

auditory canal that funnels sound to the eardrum

tympanic membrane

the eardrum; vibrates in response to sound

Eustachian tube

Connects to the pharynx, equilibrates air pressure

ossicles

ear bones; malleus, incus, and stapes

cochlea

spiral-shaped, fluid-filled organ in the inner ear that plays a crucial role in converting sound vibrations into neural signals

spiral ganglia

cluster of sensory neurons in the inner ear that convey auditory information from the cochlea to the brain.

scala vestibuli

fluid-filled tube at the top of the cochlea

cochlear duct

center of the cochlea that contains the spiral ganglia, organs of Corti and the basilar membrane

organs of Corti

Structures in the cochlear duct of the inner ear containing hair cells that convert sound vibrations into electrical signals for the brain.

basilar membrane

A flexible membrane in the cochlea that converts sound vibrations into neural signals, supporting the organ of Corti with sensory hair cells and varying in width to respond to different sound frequencies.

scala tympani

the fluid-filled chamber in the cochlea below the cochlear duct that aids in sound transmission from the oval to the round window

tectorial membrane

A gelatinous structure in the cochlear duct that converts sound vibrations into electrical impulses by displacing hair cells.

stereocilia

tiny hair-like projections on sensory hair cells in the inner ear that convert mechanical sound vibrations into electrical signals, critical for hearing

vestibule

The vestibule is the central part of the inner ear between the cochlea and semicircular canals, involved in balance by detecting linear acceleration and gravitational forces through the utricle and saccule.

otolithic membrane

gelatinous layer located in the inner ear that contains tiny calcium carbonate crystals called otoliths; aids in balance by moving in response to head movements to help inform the brain about the body's position relative to gravity

semicircular canals

three ring-like extensions of the vestibule that sense head movement

ampulla

Enlarged base of each semicircular canal that contains hair cells

cupulla

Upper membrane of semicircular canals that moves stereocilia as the head rotates

vestibular ganglion

pathway for positional sensory information leaving the inner ear

vestibulocochlear nerve

nerve bundle that contains spiral ganglia and vestibular ganglia, transporting inner ear input to the brainstem

palpebral conjuctiva

thin membrane on the inner surface of each eyelid

lacrimal gland

produces tears

lacrimal duct

directs tears to flow over the conjuctiva

optic chasm

point in the visual system at which medial retina fibers cross to the other side of the brain; causes the left field of view of each eye to be processed on the right side of the brain and vice versa

fibrous tunic

outermost tissue layer of the eye, includes the sclera and cornea

vascular tunic

the middle layer of the eye that contains many blood vessels

choroid

highly vascularized connective tissue that supplies blood to the eyeball

lens

focuses light onto the retina

ciliary body

muscular structure attached to the lens by ligaments called Zonule fibers

iris

colored part of the eye, composed of smooth muscle; controls the opening and closing of the pupil

neural tunic

innermost layer of the eye; includes the retina

retina

contains nervous tissue responsible for photoreception

aqueous humor

Water fluid that fills the anterior cavity of the eye

vitreous humor

viscous fluid that fills the posterior cavity of the eye

rods

photoreceptors in the retina that contain rhodopsin; detect light at low levels

cones

contain pigments called opsins that detect red, green, and blue light

retinal ganglion cell

produces action potentials in response to visual stimuli

optic disc

where axons of the retinal ganglion cells connect to the leave eye as the optic nerve

blind spot

region of the retina where the optic nerve leaves the eye; possesses no photoreceptors

macula

exact center of the retina

fovea centralis

region of the retina that contains nothing but photoreceptors where visual acuity is the best

contralateral

descriptive term for the nerves on one side of the body being connected to the opposite side of the brain; applies to the spinal nerves

ipsilateral

descriptive term for the sensory nerves being controlled by the same side of the brain and body; applies to the nerves of the head and neck

ascending pathways

tracts that carry peripheral sensations (from below the neck) to the brain or spinal cord

dorsal column system

associated with fine motor touch and proprioception

nerve pathway of the dorsal column system

Axon 1 enters the dorsal root region and joins the dorsal column in the spinal cord, terminating in the medulla. Axon 2 ascends the brainstem bundled as the medial lemniscus. Axon 3 ends in the post central gyrus of the cerebral cortex.

spinothalamic tract

sensory pathway primarily associated with pain and temperature

nerve pathway of the spinothalamic tract

Axon 1 enters the dorsal root and extends into dorsal horn. Axon 2 starts in the spinal cord and connects to the thalamus. Axon 3 travels from the thalamus to the post central gyrus.

Trigeminal pathway

carries somatosensory information from the face, head, mouth, and nasal cavity

nerves of trigeminal pathway

Axon 1 enters the brainstem at the pons. Axon 2 travels one of three pathways but all end in the thalamus. Axon 3 ends in the primary somatosensory cortex of the cerebrum.

thalamus

serves as an important relay for communication between the cerebrum and the rest of the nervous system; required transfer point for sensory input except smell

sensory homunculus

a visual representation of the regions of the cerebral cortex that correlate to their somatosensory signals

executive functions

cognitive functions that lead to goal-directed behavior

working memory

higher cognitive processing that helps to organize and represent information that is not in the immediate environment

premotor cortex

aids in controlling movements of core muscles to maintain posture during movement

supplemental motor area

a region of the brain located in the frontal cortex that plans and coordinates movements

Betz cells

neurons located in the primary motor cortex that descend and synapse with lower motor neurons in the brainstem or spinal cord