9 Flashcards
Allows organism to sense the body and environment
much of it is unconscious
Sensory systems
Sensory info from the skin and musculoskeletal
Somatosensory systems
Skin sensations include
touch
pain
temp
Musculoskeletal sensations include
proprioception and pain
Provides info regarding stretch of muscles, tension on tendons, positions of joints, and deep vibration
includes both static joint position and kinesthetic sense
Proprioception
Each type is specialized, responding only to a specific type of stimulus, the adequate stimulus, under normal conditions
located at the distal ends of peripheral neurons
receptors
Types of receptors
Mechanoreceptors
Chemorecpetors
Thermoreceptors
receptor that responds to mechanical deformation of the receptor by touch, pressure, stretch , or vibration
Mechanoreceptors
receptors that respond to substances released by cells
Chemoreceptors
receptors that respond to heat or cold
Thermoreceptors
A subset of each type of receptor that is preferentially sensitive to stimuli that damage or threaten to damage tissue
results in a sensation of pain
Nociceptors
The area of skin innervate by a single afferent neuron
receptive field
proximal relation of receptor fields
smaller distally and larger proximally
greater density distally than proximally
Skin innervate by axons from single dorsal root
dermatome
axons from dorsal root innervating specific parts of the limbs regrouped to form
peripheral nerve
Large myelinated Ia
receptors: muscle spindles
stimulus muscle stretch
Large myelinated Ib
receptor: golgi tendon, stimulus: tendon tension
Receptor ligament receptors, stimulus: ligament tension
Medium myelinated II
receptors:muscle spindles, muscle stretch
receptor paciniform and ruffini type receptors in joint capsules, stimulus: joint movement
A beta receptors
Meissners Pacinian Ruffinis Merkels Hair follicle
meissners stimulus
Touch, vibration (superficial fine touch)
pacinian stimulus
Touch, vibration
ruffinis stimulus
skin stretch
Markels stimulus
pressure (superficial fine touch)
hair follicle stimulus
pressure
A alpha receptors
Free nerve ending
A alpha free nerve ending stimulus
tissue damage, temp, and course touch
C receptors
Free nerve endings
C free nerve ending stimulus
Tissue damage, temp, itch, tickle
Sensory organ embedded in skeletal “extrafusal” muscle, consists of muscle fibers, sensory endings, and motor endings
Muscle spindle
What do sensory endings in muscle spindles respond to
muscle stretch
changes in muscle length and velocity of length change
Quick and tonic stretch of spindle registered by
Ia afferents
Tonic stretch monitored by
II afferents
______ adjust spindle fiber length via specialized muscle fibers so spindle is responsive through physiologic range of muscle length
small efferent fibers
Relay info about tension in tendons in both active contraction and passive stretch
Golgi tendon organs
Golgi tendon organs info transmitted by
Ib afferents
Peripheral sensory neurons have two axons
distal axons
Proximal axons
Conduct messages from receptor to the cell body
Distal axons
Project from the cell body into the spinal cord or brainstem
Proximal axons
Where are the cell bodies of most peripheral sensory neurons located
outside the spinal cord in the dorsal root ganglia or outside the brain in cranial nerve ganglia
Primary afferent fiber and ganglia classified according to axon diameter (largest to smallest)
C A alpha II or A beta Ib Ia
Types of somatosensory pathways
Conscious relay
Divergent
Unconscious relay
anatomic name for conscious relay
dorsal column/medial lemniscus
spinothalamic
Anatomic name for divergent pathways
spinomesencephalic
spinoreticular
spinolimbic
Anatomic name for unconscious relay
spinocerebellar
info conveyed by the dorsal column/medial lemniscus
Discriminative touch and conscious proprioception
Termination of dorsal column/medial lemniscus
Primary sensory area cerebral cortex
info conveyed by the spinothalamic pathway
discriminative pain and temp
termination of spinothalamic
Primary sensory area cerebral cortex
info conveyed by the divergent pathways
slow, aching pain
termination of the spinomesencephalic
midbrain
termination of the spinoreticular
reticular formation
termination of the spinolimbic
amygdala, basal ganglia, many areas of cerebral cortex
Info conveyed by the spinocerebellar
movement related info
termination of the spinocerebellar
cerebellum
Touch and proprioception info from limbs enters spinal cord via
A beta or I/II afferents
Dorsal column pathway
ascends in dorsal column to ipsilateral lower medulla
Synapse in nucleus cuneatus (UE) or gracilis (trunk or LE) of medulla
Crosses spinal cord and ascends in medial lemniscus to contralateral thalamus
Synapse in VPL of thalamus
Ascends to primary somatosensory cortex
Lateral pain system
spinothalamic pathway
Pain and temp info from limbs enters spinal core via
A alpha or C afferents and synapses in dorsal horn
Spinothalamic pathways
A alpha or C afferents synapses in dorsal horn crosses to contralateral spinal cord Ascends in spinothalamic tract synapses in VPL thalamus ascends to primary somatosensory cortex
Somatosensory systems
Primary sensory cortex
Secondary sensory cortex
Sensory association cortex
somatosensory system that registers receptor activation (maps)
primary sensory cortex
somatosensory system that processes info from that sensory system alone
patterns of activity and anticipation
secondary sensory cortex
somatosensory systems that integrates related activity of different sensory systems
Sensory association cortex
Receive sensory info directly from thalamus
each discriminates among different intensities and qualities of one type of input
Primary sensory areas
discriminates shape, texture, or size of objects
primary somatosensory
Conscious discrimination of loudness and pitch of sounds
primary auditory
distinguishes intensity of light, shape, size and location of objects
primary visual
discriminates among head positions and head movements
primary vestibular
Stereognosis and memory of the tactile and spatial environment
secondary somatosensory
Analysis of motion, color: control of visual fixation
secondary visual
classification of sounds
secondary auditory
Primary sensory areas
somatosensory
auditory
visual
vestibular
Secondary sensory areas
somatosensory
visual
auditory
Primary somatosensory cortex
S1: 3, 1, 2
secondary somatosensory cortex
S2: 5,7
Sensory association area
SAA: 39, 40`
transmits proprioceptive info to cerebellum
unconscious proprioception
critical for adjusting moveements and posture
spinocerebellar
