Exam 2 Somatic sensory Flashcards
What is sensitive to many kinds of stimuli? -including pressure, position of joints and muscles, temperature of the limbs and pain
Somatosensory system
How is the somatosensory system is different from other sensory systems?
- Its receptors are distributed throughout the body rather than being concentrated at small, specialized locations.
- Receptors are found in the skin, body wall, muscles, tendons, ligaments, connective tissue of the joints, and internal organs.
- The somatosensory system is a group of at least 4 senses rather than one:
–These include touch, temperature, body position, pain and various subdivisions of these senses.
What are some examples of modality vs sub modality and sub sub modality
In afferent axons how does size affect speed?
Smaller the diameter the slower the speed
What are the two pathways of Somatic Sensation?
Dorsal column-medial lemniscal pathway
Spinothalmaic pathway
What is the dorsal column medial lemniscal pathwya responsible for?
and what dorsal root axons does it use?
Touch, vibration, two-point discrimination, proprioception
Aa(alpha)
Ab(beta)
Ad
What is the spinothalamic pathway responsible for?
What dorsal root axons does it use?
Pain, temperature, and some touch
- Ad
- C
What are most of the sensory receptors in the skin?
-These receptors are sensitive to physical distortion such as bending or stretching
Mechanoreceptors
What are these examples of?
–Hair receptor
–Pacinian corpuscle
–Ruffini ending
–Meissner corpuscle.
–Merkel disk receptor, the only sensory receptor cell type in the somatosensory system
Mechanoreceptors
What sensory field is bigger? Those of Pacinian corpuscles or Meissners
Pacinian
This type of adapting mechanoreceptors respond quickly at first then stop firing even though the stimulus continues.
–Best suited to represent time varying (e.g., vibrating or moving) stimuli.
Rapidly
This type of adapting mechanoreceptors generate a more sustained response during a long stimulus.
–Best suited to represent static stimuli
Slowly adapting
Is the pacinian corpuscles rapid or slow adapting?
Rapid
•The capsule makes the Pacinian corpuscle exquisitely sensitive to vibrating, high-frequency stimuli, and almost unresponsive to steady pressure.
-Acting as a filter to modify the stimulus, if there is no capsule there is not much change
What are some characteristics of mechanoreceptors?
- Which thermoreceptor begins firing above 30oC and stop firing above 45oC.
- Which thermoreceptor fires faster over a broad range of skin temperatures from about 30oC down to 10oC.
Warm
Cold
Explain this image
- At the horizontal arrow, one cannot tell if the temperature is cold or warm because both cold and warm receptors are activated equally.
- At the vertical arrow, one may sense cold, even though the temperature is high because cold receptors are activated more than warm receptors.
- Which thermoreceptors fire faster during reductions in temperature (blue arrow).
- Which thermoreceptors fire faster during increases in temperature (red arrow).
Cold
Warm
What is the purpose of pain?
–Protective mechanism for the body
- Occurs in response to tissue damage
- Causes individual to react to remove stimulus.
What are the four categories of nociceptors based on function (free, branching, unmyelinated nerve endings that signal that body tissue is being damaged or is at risk of being damaged).
Mechanionociceptors
Thermal nociceptors
Chemically sensitive, mechanically sensitive nociceptors
Polymodal
Which pain receptor responds to intense mechanical stimulation (pinching, cutting, stretching)
Mechanociceptors
Which nociceptors respond to burning heat (>45oC, tissue proteins become denatured and damage occurs) or extreme cold.
Thermal
Which nociceptors respond to a variety of agents from the environment or from the tissue itself.
•Examples include potassium, extremes of pH, neuroactive substances such as histamine and bradykinin and various irritants.
Chemically sensitive, mechanically insensitive
What nociceptors respond to high intensity stimuli that are combinations of mechanical, thermal and chemical stimuli.
•They are present in most body tissues except the brain.
Polymodal
What are some characteristics of slow and fast pain?
Which type of pain is transmitted by relatively thicker (and therefore faster conducting) nerve fibers (Adelta fibers)
and
Which type of pain is transmitted by very thin nerve fibers (C fibers)
Fast pain
Slow Pain
What type of pain is
labor pain,
pain starting after fast pain from an injury
Chemical burn
Slow Pain
What type of pain is pain from a surgical incision
Fast pain
–Pain referred from area of damage to another area.
•Example: kidney pain might feel like lower back pain
Referred Pain
–Pain of a missing limb.
Phantom Pain
What type of pain comes from
–Alcohol
•Toxicity of alcohol itself irritates the meninges.
–Constipation
•From absorbed toxic products or changes in circulatory system resulting from loss of fluid in the gut.
Intracranial headache
What type of pain comes from:
–Muscle spasm
- Emotion/tension causes muscles of the head to become spastic.
- Pain is referred to overlying areas of the head.
–Sinus headache
- Pain from mucous membranes of nose and nasal sinuses
- Pain is referred behind the eyes or forehead or face.
–Eye disorders
- Difficulty focusing stresses ciliary muscles and can cause spasms in facial and extraocular muscles.
- Excessive irradiation by light rays (especially UV) causes irritation of the membranes around the eye.
Extracranial headache
What is the Gate theory of pain?
–Pain can be modified by nonpainful sensory input and by neural activity from various nuclei within the brain.
- Pain evoked by activity in nociceptors (Adelta and C fibers) can be reduced by simultaneous activity in low-threshold mechanoreceptors (Aalpha and Abeta fibers).
- This explains why it feels good to rub the skin around your shin when you bruise it.
