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The larger the receptive field, the
harder it is to locate the exact point of stimulation
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The CNS interprets information entirely on the basis of the
line over which sensory information arrives
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The area of sensory cortex devoted to a body region is relative to the
number of sensory receptors in the area of the body
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Receptors that are normally inactive, but become active for a short time whenever there is a change in the condition that they monitor
Phasic receptors
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Identify 6 types of tactile receptors located in the skin, and describe their sensitivities
- 1) free nerve endings-touch and pressure
- 2) root hair plexus: distortions and movements across the body surface
- 3) tactile discs: fine touch and pressure
- 4) tactile corpuscles-fine touch and pressure
- 5) lamellated corpuscles-pulsing or vibrationg (deep pressure)
- 6) Ruffini corpuscles: pressure and distortion of skin
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What 3 types of mechanoreceptors respond to streching, compression, twisting, or other distortions of the plasma membrane
- 1) tactile receptors
- 2) baroreceptors
- 3) proprioceptors
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What are they three major somatic sensory phatways, and what is the function of each pathway
- 1) posterior column pathway: provides conscious sensations of highly localized (fine) touch, pressure, vibration, and proprioception
- 2) spinothalamic pathway: provides conscious sensations of poorly localized (crude) touch, pressure, pain, and temperature
- 3) spinocerebellar pathway: carries proprioceptive information about the position of skeletal muscles, tendons, and joints to the cerebellum
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What three pairs of descending tracts make up the corticospinal pathway
- 1) corticobulbar
- 2) lateral corticospinal tracts
- 3) anterior corticospinal tracts
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Which three motorpathways make up the medial pathways
- 1) vetibulospinal pathway
- 2) tectospinal pathway
- 3) reticulospinal pathway
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What are the two primary functional roles of the cerebellum
- 1) integrates proprioceptive sensations with visual information from the eyes and equilibrium-related sensations from the inner ear
- 2) adjusts the activities of the voluntary and involuntary motor centers on teh basis of sensory information and the stored memories of previous experiences
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The corticospinal tract
carries motor commands from the cerebral cortex to the spinal cord
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What three steps are necessary for transduction to occur
- 1) arriving stumulus alters the transmembrane potential of the receptor membrane
- 2) receptor potential directly or indirectly affects a sensory neuron
- 3)action potentials travel to the CNS along an afferent fiber
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Differentiate between a tonic receptor and a phasic receptor.
- Tonic: always active
- phasic: normally inactive and bbecomes active only when a change occurs in the condition being monitored
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What is a motor homunculus? How does it differ from a sensory homunculus?
- motor homunculus-a mapped out area of th eprimary motor cortex, provides an indication of the degree of fine motor control available.
- sensory homunculus-indicates the degree of sensitivity of peripheral sensory receptors
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Describe the relationship among the first-, second-, and third-, order neurons
- First: sensory neuron that delivers sensations to the CNS
- second: an interneuron located in the spinal cord or brain stem
- third: in thalamus, synapse on neurons of the primary snensory coretx of the cerebral hemispheres.
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Damage tot he posteiro spinocerebellar tract on the left side of the spinal cord at the L1 level would interfere with the coordinated movement of which limb(s)
left leg
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What effect does injury to the primary motor cortex have on peripheral muscles?
ability to exert fine control over motor units. Gross movements are still possiblbe because they are controlled by basal nuclei that use the reticulospinal or rubrospinal tracts.
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By which structures and in which part of the brain is the level of muscle tone in the body's skeletal muscles controlled? How is this control exerted?
Muscle tone is controlled by the basal nuclei, cerebellum, and red nuclei through commands distributed by the reticulospinal and rubrospinal tracts
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Explain the phenomenon of "referred paon" in terms of labeled line s and organization of sensory tracts and pathways
Strong pain sensations arriving at a particular segment of the spinal cord can cause stimulation of the interneurons of the spinothalamic pathway.--this is interpreted by the sensory cortex as originating in the region of the body surface associate with the origin of the same pathway
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