Somatosensory System Flashcards
Division of Nervous System
Afferent (Sensory)
Efferent (Motor)
Afferent Division of Nervous System
Sensory Division:
transmits nerve pulses from peripheral organs to CNS
responsible for detecting stimuli
Efferent Division of Nervous System
Motor Division:
transmits nerve impulses from CN to peripheral organs
What is the Somatosensory System?
responsible for sensations that arise from tissues, other than specialised sense organs (e.g. Eye, ear, nose)
What organs are involved in somatosensory system?
skin, viscera, muscles, and joints
What are the three major components of the Somatosensory System?
- Cutaneous Sensation
- Interoreception
- Proprioception
Cutaneous Sensation of Somatosensory System
arise from the skin
Interoreception of Somatosensory System
arise from the viscera, muscles, and joints which are not related to movement
Proprioception of Somatosensory System
arise from viscera, muscles, and joints which are related to movement
structural components of the somatosensory system and where these are located in both the peripheral and central nervous system
- 3 neural pathway
- stimulus activates primary sensory neurone & releases APs which travel through pathway
- APs reach cerebral cortex
- stimulus is perceived
Transduction
he mechanisms by which stimulation of the peripheral tissues produces an action potentials in the primary sensory neuron (receptor)
Frequency Encoding:
The way in which the nervous system encodes the size of a peripheral stimulus.
The size of a peripheral stimuli is encoded by the frequency of what?
Action Potentials
i.e. Low frequency of APs = smaller stimulus
Receptive Field:
the skin area that produces action potentials in that particular neuron/ The area of the skin that when stimulated it produces action potentials.
Innervation Density:
he extent to which a particular peripheral tissue is able to detect as stimulus is directly related to the number of neurons that innervate a particular unit area which is referred to as innervation density.
The higher the innervation density the more neurons terminate in each cm2 of that tissue.
E.g. Finger Tips: ~140 pressure receptors in each cm2
Back: <1 pressure receptors in each cm2
Adaptation:
the way an individual primary sensory neuron responds to a sustained stimulus.
Slowly Adapting:
action potentials begin when stimulus is applied, continue throughout the duration of the stimulus, and stop one stimulus is removed. Response doesn’t change throughout the duration of the stimulus.
Rapidly Adapting:
same stimulus & duration but after a few seconds the neurons adapt and stop producing action potentials.
three major classes of sensations from stimulation of the skin.
- Low Intensity Mechanical Stimuli
- Low Intensity Thermal Stimuli
- High Intensity Stimuli
Low Intensity Mechanical Stimuli:
non-painful three sensations: 1. pressure 2. touch 3. vibration
the three sensations of low intensity mechanical stimuli is referred to as what?
Mechanoreception
Describe the sensation of pressure:
the degree of skin indentation
Describe the sensation of touch:
the rate at which a skin indentation is applied
Describe the sensation of vibration:
the frequency of a vibratory stimulus
Low Intensity Thermal Stimuli:
do not produce damage to the skin and are non-painful
Two Types:
1. Cold receptors
2. Warm receptors
Collectively Cold and Warm receptors are referred to as what?
thermoreception
High Intensity Stimuli:
produces damage to the skin and the sensation of pain.
Two Types:
1. Sharp Pain
2. Burning Pain
Describe Sharp Pain Sensation & an example:
occurs shortly after a mechanical injury i.e. Paper cut
Describe Burning Pain Sensation & an example:
a few seconds after sharp pain we experience a burning sensation. We can also elicit burning pain from high temperatures or pain-producing chemicals (e.g. Acids).
Sharp & Burning Pain Sensation is collectively referred to as what?
nociception
Primary Sensory Neurone responsible for Mechanoreception
Low Threshold Mechanoreceptors
