A&P Chapter 15: Sensory pathways and the SNS
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What is the difference between sensation and perception?
- 1. Sensation: the activation of senses, arriving information from the senses
- 2. Perception: conscious awareness of a sensation, activation of the sensory cortex
How do we detect stimuli?
- 1. Receptor specificity: each receptor has a characteristic sensitivity (to temp, pain, touch, etc.)
- 2. Receptive field: The area monitored by a single receptor cell, the larger the field, the more difficult to localize the stimulus
How can receptive field and number of sensory neurons affect our sensitivity?
- 1. Receptive field: the smaller the field, the easier it is to localize the stimulus, receptors in the fingers have a very small receptive field the receptors of the back have a large receptive field
- 2. Number of sensory neurons: the more neurons in an area, the more likely a very small or faint stimulus will activate the receptor cell
What is adaptation?
- 1. Reduction in sensitivity to constant stimulus
- 2. Sensory neurons eventually stop sending action potentials if stimulus is constant and non painful
- 3. We don't need to be consciously aware of our clothing touching our skin
What are the classes of general sensory receptors?
- 1. Nociceptors: pain receptors, fast or slow pain depends on the size/type of axon
- 2. Thermoreceptors: temp receptors that are free nerve endings
- 3. Mechanoreceptors: tactile receptors provide sensations of touch and vibration, baroreceptors detect pressure changes in walls of blood vessels and proprioreceptors monitor the positions of joints and muscles
What are the 3 ascending somatic sensory pathways and what information do they carry?
- 1. Spinothalamic pathway: from spine to thalamus, sensation of crude touch, pressure, pain, and temp
- 2. Posterior column pathway: from spine to thalamus, sensation of fine touch, pressure, vibration and proprioception
- 3. Spinocerebellar pathway: from spine to cerebellum, proprioreceptive information about position of joints, tendons and skeletal muscles
What is the difference between the anterior and lateral spinothalamic tracts?
- 1. Anterior spinothalamic tract: carries crude touch and pressure sensations
- 2. Lateral spinothalamic tract: carries crude pain and temperature sensations
What is referred pain?
- 1. Referred pain is when you feel pain in an uninjured part of your body when the pain originates in another location
- 2. Strong visceral pain arriving at a segment of the spinal cord can stimulate interneurons that are part of the spinothalamic pathway which leads to stimulus on the primary sensory cortex
What are the 3 somatic motor pathways and what information do they carry?
- 1. Corticospinal pathway: from cortex to spine, conscious motor control of skeletal muscles
- 2. Medial pathway: from cortex to spine, controls muscle tone and gross movement of the neck, trunk and proximal limb muscles
- 3. Lateral pathway: from cortex to spine, controls muscle tone and precise movements of distal portion of the limps
What are the sensory and motor humunculus?
- 1. Sensory homunculus: map of the body on the post central gyrus (primary sensory cortex), cortex surface area associated with each part of the body is determined by the number of sensory receptors on that part of the body
- 2. Motor homunculus: map of the body on the pre central gyrus (primary motor cortex), cortex surface associated with each part of the body is determined by the number motor units involved in that region's control
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