Somatosensation

Anatomy & Physiology 19 with Jaworski at University of Vermont

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By: Emily Mandara
Created: 2010-11-20
Size: 30 flashcards
Views: 23

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What are the 5 special senses?

Vision
Audition
Taste
Olfaction
Equilibrium (vestibular)

What are somatosensations?

Senses detected throughout the body
Superficial cutaneous senses- light touch and pressure, vibration, hot, cold, pain, itch, tickle
Deep senses- position sense, pain, intense pressure
Visceral senses- visceral pain, hunger, nausea, thirst

Receptors (4 main)

Nociceptors= pain and tissue damage
Thermoreceptors= temperature
Chemoreceptors= chemicals
Mechanoreceptors= 4 types

Superficial cutaneous
Deep cutaneous
Baroreceptors
Proprioceptors

Nociceptors

Free nerve endings sense tissue damage, chemical signals, temperature extremes; conveys pain
Anterolateral pain and temperature

Thermoreceptors

Free nerve endings sense temperature
Anterolateral pain and temperature

Chemoreceptors

Respond to chemicals in interstitial fluid

Mechanoreceptors

Most important!!
Superficial cutaneous- highly sensitive to fine touch and pressure for specific localization
Deep cutaneous- less sensitive to crude touch and pressure for less specific location (blood pressure, gut pressure)
Baroreceptors- detect internal pressure (blood vessels, bladder, GI)
Proprioceptors- monitor limb position
Spinocerebellar Cuneocerebellar unconscious sensation
Dorsal Column-Medial Lemniscal conscious sensation

Receptive Field

Part of the body from which the receptor can be stimulated (area of skin for touch sensation)
Small receptor fields can discriminate finer sensation
When receptors synapse in spinal cord many receptors converge- spinal cord neuron receptor fields are much more complex

Receptor Characteristics- Adaptation

Reduction in sensation with repeated stimulation
Some receptors adapt whereas others do not
Info comes from either slowly adapting receptors or rapidly adapting receptors
Slowly adapting receptors- respond throughout the stimulus duration
Rapidly adapting receptors- only respond at the beginning of the stimulus

Receptor Characteristics- Sensory Coding

Receptors code the quality and the quantity of the stimulation

Quality is determined by specific types of receptors activated
Quantity depends on the number of receptors activated and the firing rate

Receptor Potentials

Differ from action potentials
Are graded and summed
Amplitude is due to the intensity of the stimulation
Once of sufficient intensity the receptor fires an action potential
Action potential firing rate codes stimulus intensity

Superficial Cutaneous Mechanoreceptors

Monitor small areas of skill to detect very fine sensation
Meissner's Capsule- rapidly adapting, low frequency vibration
Merkel Cell- slowly adapting, pressure

Deep Cutaneous Mechanoreceptors

Monitor larger areas of skin to detect crude sensation
Pacinian Corpuscle- rapidly adapting, vibration
Ruffini Ending- slowly adapting, pressure

Muscle Receptor

Monitors muscle length and rate of change
Organized in parallel with extrafusal muscle fibers (bulk of muscle)

Extrafusal vs. Interfusal Muscle Fibers

Sensory receptor is associated with intrafusal muscle
Requires two types of motor neurons- Alpha motor neurons are innervate extrafusal muscle and Gamma motor neurons innervate intrafusal muscle.

Golgi Tendon Organ (GTO)

Joint receptor
Monitors muscle tension without change in length
Organized in series with etrafusal muscle fibers

What happens after a receptor is activated?

Slide 128 ????

Dorsal Spinocerebellar Pathway

Only for the legs
Function= Provides cerebellum with info about muscle length and tension (unconscious proprioception)- not directly to cerebrum
Receptors= Muscle spindles and Golgi tendon organs
Primary afferent neuron synapses within the dorsal horn gray matter
Second order neurons ascend in ipsilateral whit matter and enter cerebellum via inferior cerebellar peduncle
After synapsing in cerebellum, info exists to contralateral red nucleus and thalamus- info from this pathway crosses in cerebellum

Cuneocerebellar Pathway

Only for the arms
Receptors= Muscle spindles and Golgi tendon organs
Primary afferent neuron synapses within the dorsal horn gray matter
Second order neurons ascend in ipsilateral whit matter and enter cerebellum via inferior cerebellar peduncle
After synapsing in cerebellum, info exists to contralateral red nucleus and thalamus- info from this pathway crosses in cerebellum

Dorsal Column-Medial Lemniscus Pathway

Function= touch (pressure and vibration) and conscious proprioception
Goes to cortex without going to the hypothalamus
Receptors= cutaneous mechanoreceptors, muscle spindles, and golgi tendon organs
Primary afferent ascends in dorsal white matter without synapse in spinal cord, first synapse is in medulla

2 synapses- leg info synapses in gracilis and arm info synapses in cuneatus

Second order neurons synapses and crosses in thalamus
Info from this pathway crosses in medulla

Pain

Purpose= protection
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Ventral part of spinal cord

Nociceptive Pain

Normal pain associated with tissue damage
Substance P transmits pain from the peripheral to the spinal cord
There is a hyper-excessive pain zone around the site of the injury for protection

Acute Pain

Can localize
Derived from skin
2 components controlled by different afferents- sharp and localized initial pain and delayed pain
Neospinothalamic Tract

Neospinothalamic Tract

Function= acute pain, temperature, crude touch
Receptors= myelinated nociceptors
Primary afferent synapses in dorsal gray matter
Second order neurons crosses in spinal cord, then crosses in thalamus
Info crosses in the spinal cord (straight up to thalamus)

Chronic Pain

Not as easy to localize
Derived from muscle, bone, joints, or connective tissue
Dull pain which tends to radiate into surrounding tissues
Paleospinothalamic Tract

Paleospinothalamic Tract

Function= chronic pain, temperature, crude touch
Receptors= unmylinated nociceptors
Primary afferent synapses in dorsal gray matter
Second order neurons sends info to raphe nucleus and periaqueductal gray
Info from this pathway crosses in the spinal cord

Central Pain Modulation

??? slide 142

Neuropathic Pain

Pain that persists long after all tissue injury is healed
Hyperalgesia- an exaggerated painful response to a normally noxius stimulus
Allodynia- a painful response to a normally non-noxious stimulus (ex- clothes touching sunburned skin)

Referred Pain

Visceral pain

dull and diffused
can be produced by multiple stimulus
accompanied by autonomic responses

Axons carrying organ pain info and axons carrying skin pain info synapses on the same spinal cord neuron- the brian cannot distinguish where pain is coming from

Phantom Limb Pain

80% amputees have phantom sensation
Pain is neuropathic

About this deck

By: Emily Mandara
Created: 2010-11-20
Size: 30 flashcards
Views: 23

About StudyBlue

“I have used this website for three exams, and I see a huge difference in my test results.”
Naj