Sensory Pathway and SNS Flashcards
sensory pathways
-series of nuerons that relays sensory information from receptors to CNS
sensory receptors
specialized cells or cell processes that monitor specific conditions
-in the body or the external environment
-when stimulated a redeptor generates action potential that are sent along the sensory pathway
-processes of specialzied sensory nuerons
-or cells monitored by sensory nuerons
Afferent division of the nervous system
-somatic and visceral sensory pathways
efferent dividsion of the nervous system
-somatic motor portion
-carries out somatic motor commands that control peripheral effectors
-commands travel from motor centers in brain along somatic motor pathway
sensation
arrivign information
perception
conscious awareness of a sensation
general senses
-temperature
-pain
-touch
-pressuree
-vibration
-proprioreception
special senses
olfaction
-gustation
-vision
-equilibrium
-hearing
special sensory receptors
-provide sensations of special senses
-located in sense organs such as eye or ear
-protected by surrounding tissuesf
factors of detection of stimuli
-receptor specificity - each receptor has a characteritisc sensitivity
-receptive field - area montiored by a single receptor cell, the larger the receptive field the more difficult itis to localize timulus
-transduction - conversion of an arriving stimulus into an action potential by a sensory receptor
how do taste hearing equilibrium and vision communicate with sensory nuerons
across chemical synapses
interpretation of sensory information
-stimulus reaches cortical nuerons via labeled line
-each labeled line carries info about one modality
-frequency and pattern of action potential contain info
-your perception of nature of a stimulus depends on the path it takes in CNS
classification of sensory receptors
-exteroreceptors - provide info about external environemnt
-proprioreceptors - report posituions of skeletal muscles and joints
-interoreceptors - visceral organ and functions
receptor classification based on nature of stimulus
-nociceptors - pain
-thermoreceptors - temp
-mechanoreceptors - physical distortion
-chemoreceptors - chemical concentration
nociceptors
-free nerve endins with large receptive fields
-common in superficial portions of skin, in joint capsules and within the periostea of bones, around walls of blood vessels
-sensitive to temperature extremes, mechanical damage, dissolved chemicals
myelinated Type A fibers
-nociceptors
-carry out sensations of fast pain such as that caused by injection or deep cut
-sensations reach CNS quickly and often trigger somatic reflexes
-relayed to primary somatosensory cortex and thus conscious attention
unmyelinated Type C fibers
-nociceptors
-carry sensations of slow pain
-sensations cause generalized activation of reticular formation and thalamus
-you become aware of the pain but only have a general idea of the area affected
thermoreceptors
-free nerve endings located in dermis, skeletal muscles, liver hypothalamus,
-sensations are conducted along same pathways that carry pain receptors (reticular formation, thalamus, and the primary somatosensory cortex)
mechanoreceptors
sensitive to physical stimli that distort their plasma membrane
-membranes contain mechanically gated ion channels that open or close in response to stretching, compression, twisting
three classes of mechanoreceptors
-tactile
-baroreceptors
-proprioreceptors
tactile receptors
provide sensations of touch, pressure, vibrations
baroreceptors
detect pressure changes in blood vessels and in digestive, respiratory, and urinary tracts
proprioceptors
monitor positions of joints and skeletal muscles
fine touch and pressure receptor -tactile receptors
-extremely sensitive
-narrow receptive field
-provide detailed info about source of info
crude touch and pressure receptors -tactile receptors
large receptive fields
-provide poor localization
-give little info about stimulus
six types of tactile receptors in the skin
-free nerve endings
-root hair plexus
-tactile discs
-bulbous corpuscle
-lamellar corpuscle
-tactile corpuscle
free nerve endings
situated between epidermal cells, tonic receptors with small receptibe fields provide sensations
root hair plexus
monitor distortions and movements across body surface wherever hair are located
-adapt rapidly so are best at detecting initial contact and subsequent movement
tactile discs
extremeley sentive tonic receptors
-sensitive to shape and texture
-very small receptive fields
-
bulbous corpuscle
sensitive to pressure and distortion of the deep dermis
lamellar corpuscle
-sensitive to deep pressure and high frequency vibration
-single dendritie lies within a series of concentric layers of collagen fibers
tactile corpuscle
sensitive to fine touch, presure and low freuqency vibration
-most abundant in eyelids lips fingertips nipples and external genetalia
baroreceptors
monitor change in pressure in an organ
-free nerve endings that branch within elastic tissues
-respond immediately to change in pressure but adapt rapidly
baroreceptors in the body
–carotid sinus and aortic sinus
-lung
-digestive tract
-colon
-bladder wall
proprioception
-somatic sensation
-no proprioceptors in visceral organs of thoracic and abdominopelvic cavities
-proprioreceptors are found in joints, tendons and ligaments, muscles
three major groups of proprioceptors
-muscle spindles
-golgi tendon organs
-receptors in joint capsules
muscle spindles
-proprioceptors
-monitor skeletal muscle lenght
-trigger stretch reflexes
golgi tendon organs
-at junction between skeletal muscle and its tendon
-monitor tension during muscle contraction
receptors in joint capsules
-proprioceptors
-free nerve endings that detect pressure, tension and movement at the joint
chemoreceptors
-respond to water and lipid soluble substances that are dissolved in body fluids
-echbit peripheral adaptation in secnds
-monitor pH carbon dioxide and oxygen levels in arterial blood at carotid bodies and aortic bodies
function and location of chemoreceptors photo
first, second and third order nueron
-first - sensory nueron that delivers sensations to CNS
-second - internuerons in SC or brainstem that reieved info from first order nueron, corsses to oppsoite side of CNS (decussation)
-third order - nueron in thalamus that must recieve info from second order nueron for sensation to reach awareness
major somatic sensory pathways
-spinothalamic pathway
-posterior column pathway
-spinocerebellar pathway
spinothalamic pathway
-carries sensations of crude touch pressure pain and temp
-first order nuerons enter spinal cord and synapse within posterior horns
-second order nuerons cross to opposite side of spinal cord before ascending
-third order nuerons in ventral nuceli of thalamus
tracts of the spinothalamic pathway
-anterior spinothalamic tract
-lateral spinothalamic tract
results of abnormality in spinothalmic pathway
-painful sensations that are not produced where they are percieved to originate
-phantom limb syndrome
-referred pain - feeling pain in an uninjured part of body when pain originates at another location
-visceral pain can manifest as pain in body surface (heart attack is freqeuntly felt in left arm)
posterior column pathway
carries sensations of fine touch vibration pressure and proprioreception
spinocerebellar pathway
-conveys information about position of muscles tendons and joints from spinal cord to cerebellum
-this information does not reach our awareness
visceral sensory pathways
visceral sensory info is collected by interoreceptors monitoring visceral tissues and organs
-interoreceptors include nociceptors, baroreceptors, thermoreceptors, tactile receptors and chemoreceptors
-cranial nerves V VII IX and X carry sensory info
solitary nucleus
-part of the visceral sensory pathway
-large nucleus on each side of medulla oblongata
-major processing and sorting center for visceral sensory info
-extensive connections with cardiovasicular and repsiratory centers and reitcular formation
somatic motor pathways always involve
-atleast two motor nuerons: upper motor nueron and lower motor nueron
upper motor nueron
-cell body lies in a CNS processing center
-synapses on lower motor nueron
-activity may facilitate or inhbit lower motor nueron
lower motor nueron
-cell body lies in a nuclues of brainstem or spinal cord
-innervated a single motor unit in a skeletal muscle
-activation triggers contraction in innervated muscle
-damage eliminates voluntary and reflex control over innervated motor unit
conscious and subconscious motor commands
-control skeletal muscles by travelling over three integrated motor pathways: corticospinal pathway, medial pathway, lateral pathway
role of cerebrum, diencephalon, and brainstem of somatic motor pathways
-may issue somatic motor commands in response to subconscious processing
-medial pathway helps control gross movements of trunk and proximal limb muscles
-lateral pathway helps control distal limb muscles that perform precise movements
basal nucelu and cerebellum of somatic motor pathway
-responsible for coordination and feedback control over muscle contractions
-consciously or subconsciously directed
cerebellum monitors
-proprioceptibe sensations
-visual information from the eyes
-vestibular sensations from internal ear
-patterns of cerebellar activity are learned by trial and error over many repitiions
