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Somatosensation

Terms in this set (25)

Soma defintion
Sensation definition
Somatosensation definition
Soma: Body
Sensation: Perception associated with stimulation
Somatosensation: Sensory information from the skin and musculoskeletal systems (muscles, bones, tendons, and joints)
Somatosensation is initiated by a variety of sensory receptors collectively called ___ ___.
These receptors respond to:
Somatic receptors;
Sense of posture and movement (proprioception), touch and pressure, temperature, pain
Proprioception receptor type and axon type
Touch receptor type and axon type
Pain, temp. Receptor type and axon type
pain, temp, itch receptor type and axon type
Sensory Function: Proproception receptor type: muscle spindle afferent axon. type: Ia, II (Group I, A alpha)
Sensory function: Touch: receptor type: Merkel, Meissner, Pacinian, and Ruffini cells. Type: A Beta (Group II)
Sensory function: Pain, temp. Receptor type: free nerve endings. Type: A delta (Group III)
Sensory function: Pain, temp, itch. Receptor type: free nerve endings (unmyelinated) Type: C (Group IV)
Muscle spindles (type Ia & II) respond to ___
Golgi tendon organs (type Ib afferents) respond to __.
Joint receptors (type Ib, II, C afferents) respond to __.
Changes in muscle length and the velocity of length change;
Tension in the tendons; GTO responds to muscle over-contraction by causing muscle to relax
Mechanical deformation of the capsule and ligaments
Touch and pressure
Receptive field - relationship with spatial acuity. __ receptive field: high spatial resolution (__ and ___)
__ receptive field: low spatial resolution (__ and ___)

Adaptation speed (response to sustained indentation)
relationship with motion detection
Rapid adaptation- good at _______
Slow adaptation - insensitive to ____
Small; (Merkel and Meissner)
Large; (Pacinian and Ruffini)
Good at motion detection; (Meissner and Pacinian)
Insensitive to motion (Merkel and Ruffini)
Rapidly adapting
Superficial (small RF): Meissner
Deep (large RF): Pacinian
Slowly adapting
Superficial (small RF): Merkel
Deep (large RF): Ruffini
Pain and Temperature (receptors)
Thermoreceptors have a __ threshold; ___
Nociceptors have a __ threshold; ___
Pain- Nociceptor
Temperature- Thermoreceptor
Thermoreceptors have a low threshold; saturate (low magnitude of afferent response A. Potentials per second)
Nociceptors have a high threshold; not saturate (high magnitude of afferent response a potentials per second)
Definition of Pain

Pain is the ___ of bodily sensations reflecting the presence of ____ stimulation combined with a feeling of ___ or other __ __.
Perception; tissue damaging; unpleasantness; negative emotion
Pain transmission
Periphery: Pain stimulus —> Nociceptor —> Afferent pain Fiber (C and A Delta fibers). CNS: Substance P or glutamate released —> Thalamus —> Somatosensory cortex
First and second pain
A Delta: first pain
C: longer lasting pain
Hyperalgesia Definition
Increased sensitivity to painful stimuli. The pain can last for hours after the original stimulus is over.
Common region of referred pain
Heart
Referred Pain definition
Pain that is perceived to occur at a site other than where the stimulus occurs .
Convergence of visceral and somatic afferent neurons- common ascending pathway
Inhibition of pain
Analgesia defintion
The selective suppression of pain without effects on consciousness or other sensations
How is analgesia done
Drugs (morphine, anti-convulsants, anti-inflammatory, etc)
Electrical stimulation ( TENS), Acupuncture, Distraction, Placebo, Yoga, Music
Descending Pain Modulation
From Lecture: Example: Morphine. Will compete with neurotransmitters that are normally released from the neurons. Will compete with opiate receptors specifically, decrease those and there will be less neurotransmitters binding to second neuron and therefore will decrease propagation up to the somatosensory cortex. Competitive Inhibition occurs with certain drugs. Catecholamines, epinephrine and norepinephrine can also compete with binding sites and decrease pain.
Spinal cord pain modulation
Gate control theory of pain
Stimulation of non-pain, low threshold afferent fibers (A Beta fiber)
Activate inhibitory local circuit neuron
Reduced activity of pain projection neuron
Pain relief
How does TENS work?
"close the gate" so that you don't feel pain, electrical stimulations blocks thalamus from responding from pain from below

Open the gate

From Lecture: recruits mechanoreceptors that are neighboring the nociceptors - results in activation of neurons that then connect with interneurons and then inhibit some neurons that are linked with nociceptors.
TENS kind of inhibits pain respoinse
TENS =Transcutaneous electrical nerve stimulation
Dorsal Column/Medial Lemniscus System
Touch and Proprioception
Anterolateral (also called Spinothalamic) system
Pain and temperature
Dorsal Colum/Lemniscus System (order neurons)
First order neuron: from receptors to medulla
second order neuron: from medulla to thalamus
third order neuron: from thalamus to somatosensory cortex

* Cross the midline at the medulla
Anterolateral System (order neurons)
First order neuron: from receptor to dorsal horn of spinal cord
Second order neuron: from dorsal horn to thalamus
third order neuron: from thalamus to somatosensory cortex

* Cross the midline at spinal cord
The somatosensory cortex

The more __ innovated, the __ areas in the somatosensory cortex
Densely; Larger
Accident severed half of a person's spinal cord at the mid-thoracic level, but other half remained intact, what pattern of sensory deficits would occur?
Dorsal column system: Loss of touch and proprioception of same side as lesion (ipsilesional)
Anterolateral system: Loss of pain and temperature of contralateral side
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