Sensory System ppt 9-11 Flashcards
What are characteristic of sensory stimuli?
modality location intensity duration
What is modality?
General class of stimulus, General (somatic and visceral) Special (smell,tast etc.)
What are free nerve ending sensory receptors?
bare dendrites associated with pain, thermal, tickle, itch and some touch sensations PAIN TEMPERATURE throughout the skin
What are encapsulated nerve endings sensory receptors?
dendrites enclosed in connective ties. Pressure, vibration and some touch sensation
What type of stimulus do mechanoreceptors detect?
Mechanical stimuli. touch, pressure, vibration, proprioception. hearing and equilibrium. monitor stretch of blood ves.
What type of stimulus do thermoreceptors detect?
changes in temp
What type of stimulus do nociceptors detect?
painful stimuli from physical or chemical damage
What type of stimulus do photoreceptors detect?
direct light the strikes the retina of the eye
What type of stimulus do chemoreceptors detect?
chemicals in the mouth (taste), nose (small) and body fluids
What type of stimulus do osmoreceptors detect?
sense osmotic pressure of body fluids
Where are proprioceptors located? What to they relay?
in the muscles, tendons, joints and inner ear. provide information about position, movement and equilibrium.
What do messier corpuscles sense?
Dynamic, fine/light touch, position sense
What do Pacinian corpuscles sense?
Vibration and Pressure in the deep skin layers, ligaments and joints
What do Merkel discs sense?
Pressure, deep static touch, position sense. at the finger rips and superficial skin
What do Ruffini corpuscles sense?
pressure, slippage of objects, joint angle change at the the fingertips and joints.
What is the receptive field?
an area of the body that when stimulated results in a change in firing rate of a sensory neuron.
How to neighboring receptive field interact?
Receptive field of neighboring afferent neurons usually overlap. *Degree of over lap varies in different part of body.
What is acuity?
the precision of stimulus localization or the ability to distinguish fine details smaller field higher density less convergence overlap lateral inhibition
What is a lateral inhibition (sensory)?
capacity of an excited neuron to reduce the activity of its neighbors.
Two point discrimination
minimum distance between 2 caliper points , perceived as separate points of stimulation test the integrity of the dorsal column and proprioception.
What is spatial summation
intensity can be transmitted by increasing number of parallel fibers
What is temporal summation?
intensity can be transmitted by sending more ap along a single fiber
What is a receptor potential?
initial response of a receptor- voltage across the receptor membrane intensity determines the frequency of action potentials
SLOW adapting Receptors TONIC
Adapt very little over time and remain responsive during long stimuli. Pressure.
RAPIDLY adapting receptors PHASIC
Adapt very quickly and essentially detect only the onset of a stimulus. Vibration.
Dermatome Reflex mnemonic
s1-2 buckle my show l3-4 kick the the door c5-6 pick up sticks c7-8 lay them straight
What is the arrangement of neuron in the sensory pathway?
- from receptor to spinal cord (dorsal root ganglion) 2. first order to thalamus. (cross midline) 3. Thalamus to sensory cortex
What does the Fasciculus gracilis receive?
sensory from the ipsilateral lower limb
What does the fasiculus cuneatus receive?
sensory from ipsilateral upper limb
What does the spinothalamic tract receive?
pain and temp from the contralateral side of the body
What are the anterolateral pathways?
Anterior spinothalamic- crude touch Lateral spinothalamic- pain temp (lisseaur tract)
What does the Posterior column (Dorsal medial lemniscus) sense?
fine touch
vibration
tactile location/ discrimination
streognosis
proprioception
Medial Lemniscus Pathway
1.Axon enters to the fasiculus. 2. Terminate in the nuc gracilis or cuneatus. CROSS MIDLINE at MEDULLA 3. up medulla, pons and midbrain. 4. end in the VPL of the thalamus
Anterolateral (Spinothalamic) Pathways
- Axon enters the spinal cord in spinothalamic tract. CROSS MIDLINE in the SPINAL CORD.
- Anteriolatertract in medulla.
- up medulla, pons and midbrain.
- end in the VPL of the thalamus
Tract of Lissauer
Lie’s Hurt PAIN a spinal ganglion enters the spinal cord and before it synapse with gives fibers to the above and bellow segments
What is the first modulator of pain?
Substantia gelatinosa jello to relieve pain
Spinocerebellar Pathway
- Proprioceptive info enters spinal cord. Travels fascicles cutaneous. 1b. Clark Nuc L3-C8 2.Posterior Spino cerebellar tract brainstem, medulla 3. Ipsilateral cerebellum
Which spinocerebellar pathway crosses over twice?
ventral (anterior) spinocerebellar
Romber Sign
lesion in the dorsal columns
Which lesion affects only the spina cerebellar tract
Fridreich Ataxia
Aδ mechanical nociceptors
Myelinated axons respond to COLD fast paint
Polymodal C fiber Nociceptors
UNmyelinated Response to hot temp slow pain.
Vanilloid Receptors
VR-1 Capsaicin VRL temp >50*C
Mechanism of Pain
Breadykinin, 5HT, Prostaglandin and Histamine active nociceptors. Noci. releace Sub. P with causes more realest of histamine
What is the dual pathway for pain?
Paleospinothalamic (C fibers)- slow Neospinothalamic (Aδ fibers)- fast
Unmodulated Pain
Unmodulated pain- excitation of the second order neuron- inhibition of the inhibitory interneuron.- pain passes to thalamus
Gate theory of pain modulation
Aβ fibers carrying sensory information about mechanical stimuli help block pain transmission
Referred pain
painful sensation in site other than the injured one. Dermatome theory Convergence Theory
Hyperalgesia:
increased sensitivity and lower threshold to painful stimuli.
Hypoalgesia:
decreased sensitivity and raised threshold to painful stimuli.
Analgesia:
complete loss of pain sensation
Allodynia:
the state in which there is excessive response to even mild stimuli.
