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38 terms

Ch16: Sensation

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Sensation
-conscious or subconscious awareness of changes in the internal or external environment.
- each unique one has its own modality
-there are general and special types
Perception
the process of organizing and interpreting sensory information by the cerebral cortex of the brain
Generator Potential
sensationlarge enough to reach threshold and initiate an action potential
Receptor Potential
graded potential which are affected by neurotransmitters.
Free Nerve Endings
-bare dendrites of sensory receptors.
-transmit the feeling of pain,temperature,tickling, itch and touch
Encapsulated Nerve Endings
-Dendrites enclosed in a CT capsule
-transmit sensation of pressure,vibration,and touch
Exterceptors
located on the external surface of the body
Interoceptors
located in blood vessels, visceral organs, muscles and nervous system
Proprioceptors
-located in muscles, tendons, inner ear, and joints
-allow the body to know its position even when moving
Mechanoreceptors
-sensitive to deformation, stretching, and bending of cells
-function in touch, pressure, vibration, proprioception, hearing and equilibrium
Thermoceptors
sensitive to temperature
Nociceptors
sensitive to chemicals that register pain
Photoreceptors
sensitive to light
Chemoreceptors
sensitive to chemicals in the mouth, nose, and body fluids
Osmoreceptors
sensitive to osmotic pressure in body fluids
Tactile
refers to the sense of touch, pressure, vibration, itch, tickle etc.
Touch
result from stimulation of tactile receptors in skin or subcutaneous
Pressure
sustained sensation over a larger area than touch; receptors adapt rapidly
Vibration
rapid repeating impulses from tactile receptors (Meissner/Pacinian Corpuscles)
Itch
chemical stimulation of free nerve endings
Tickle
stimulation of free nerve endings
Cold
Thermal sensation who's receptors react to 50-105 F; most abundant; adapt rapidly
Warm
Thermal sensation who's receptors react to 90-118 F; adapt rapidly
Pain
-Sensation necessary for survival
-In all tissues of the body except the brain
-React to chemicals released from damaged tissue as well as excessive stretching, muscle spasms and ischemia.
ischemia
insufficient blood flow to an area of the body
Fast Pain
very precisely located surface sensation; impulse moves rapidly
Slow Pain
wide spread and deeper sensation; movement of impulse is slow and persistent
Referred Pain
regions of the body sense pain on the surface from an internal source
ex) pain in left arm during a heart-attack
First-order Neurons
conduct impulses from the body to the CNS
Second-order Neurons
conduct impulses from the brain and spinal cord to the thalamus
Third-order Neurons
conduct impulses from the thalamus to the primary somatosensory area of the cerebral cortex
Lemniscus Pathway
Impulses of touch,pressure,vibration,conscious perception of limbs, trunk,neck and posterior head ascend to the cerebral cortex.
Anteriolateral (Spinothalamic) Pathway
Sensory input for pain,temperature,itch and tickle ascend to the cerebral cortex
Trigeminothalmic Pathway
Nerve impulses for most somatic sensations
Direct (Pyramidal) Pathway
1)Corticospinal pathway from motor cortex to skeletal muscles in limbs and trunk

2)Corticobulbar connect the motor cortex to muscles in the head
Indirect (Extra Pyramidal) Pathway
-Travel from cerebral cortex through nuclei of cell bodies
-include rubrospinal, tectospinal, vestibulospinal, lateral reticulospinal, and medial reticulospinal pathways
Basal Ganglia
-Influence muscle tone as well as sensory,limbic,cognitive and linguistic functions.
-Function in the initiation and termination of movements
Cerebellar Function
-Monitors intentions for movements
-monitors actual movements
-compares intentions with actual movements
-corrects incorrect movements