The Skin Example Skin Receptors: Free nerve ending; Pacinian corpuscles; Ruffini endings; Hair...
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Transcript of The Skin Example Skin Receptors: Free nerve ending; Pacinian corpuscles; Ruffini endings; Hair...
The Skin
Example Skin Receptors: Free nerve ending; Pacinian corpuscles; Ruffini endings; Hair follicle ending; Meissner corpuscle; Merkel’s disk
Light touchPressureVibrationTemperaturePainHair movement
The Skin
Example Skin Receptors: Free nerve ending; Pacinian corpuscles; Ruffini endings; Hair follicle ending; Meissner corpuscle; Merkel’s disk
Different types of skin receptors
Spinal Cord
Spinal Cord
Monosynaptic Reflex
Disynaptic Reflex
1. Sensory neurons
2. Neurons in the spinal cord
3. Motor neurons which control muscle contraction
Why does the reflex occur before perception takes place? Answer:
• The sensation of heat reaches our perception only after the reflexive withdrawal took place, because the somatosensory information can travel very quickly to the spinal cord and then back down to the motor neurons, whereas it takes a longer time for this information to reach the higher areas of the brain, where it yields to perception.
SKIN
Spinal Cord Brain
BRAIN
Somatosensory pathway
Spinal Cord Brain
Cerebral Cortex
Thalamus
Medulla Note crossing!
Spinal Cord
The Thalamus: Anatomy
The thalamus: Functions
The major role of thalamus is to gate and otherwise modulate the
flow of sensory information to cortex.
The Thalamus: Functions
The thalamus also play an important role in regulating states of sleep and
wakefulness.
Sensory processing hierarchy
Thalamus
Cortex
Sensor
Sensory processing is different areas of the brain
The full somatosensory pathway
Touch on left finger
Heat on right finger
The “Homunculus”
The cortical representation of sensory information is not uniform, but emphasizes certain sensory parts of the body, such as the lips and fingers.
Somatosensory - Brain
CNS preserves the peripheral body map.
Amount of CNS tissue is proportional to the distribution of peripheral receptors.
Homunculus: Other Animals
Brain MappingFinding out what each part of the brain does
Brain Areas are Specialized for Different Functions
Demo: how many picks?• Use a fork for the following experiment.• Gently pressure your neighbor’s fingertip with 1, 2, or 3 of
the fork’s picks. Can he tell (without looking) how many picks are touching his fingertip?
• Now do the same on other body area, such as inside the arm, on the legs, on the lips, or on the back of the body. Can you still tell how many picks? Where?
Somatosensory discrimination varies throughout the body surface
Somatosensory - Brain
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Somatosensory - Brain| |
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Site Threshold DistanceFingers 2-3 mm
Upper Lip 5 mmCheek 6 mmNose 7 mmPalm 10 mm
Forehead 15 mmFoot 20 mmBelly 30 mm
Forearm 35 mmUpper arm 39 mm
Back 39 mmShoulder 41 mm
Thigh 42 mmCalf 45 mm
Influence of:IceDistractionSound
Pain!
Gate Control Theory
Proprioception
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