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sensation
a state of awareness of internal or external conditions
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perception
conscious registering of a stimulus/sensation
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a sensation requires
- 1) stimulus
- 2) receptor/sense organ
- 3) conduction
- 4) translation
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conduction
get the stimulus to the brain
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translation
convert stimulus into a sensation
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characteristics of sensation
- projection
- modality
- adaptation
- afterimage
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projection
the brain can put a location on its origin
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modality
sensations can be distinguished/separated from one another
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adaptation
reduction/dissapearance of a sensation, even though the stimulus is still being applied
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afterimage
persistance of a sensation, even after the stimulus is removed
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sensory receptors
can be classified by location, type of stimulus, or complexity
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location
extero, intero, viscero receptors
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proprioreceptor
change in body part position
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mechanoreceptors
- change in shap of receptor or nearby cells
- respond to physical deformation-
- ex. baroreceptors - blood vessels
- hair cells- hearing & equilibrium
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nociceptors
pain (free nerve endings)
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chemoreceptors
changes in chemical levels (taste & smell)
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general senses
- simple receptors & pathways:
- touch
- pressure
- heat
- cold
- pain
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special senses
taste, smell, vision, hearing, equilibrium
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12 pair
- 10 originate in the brain stem
- 1 originates in olfactory mucosa
- 1 originates in retina of eye
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motor:
oculomotor, accesory, trochlear, hypoglossal, abducens
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sensory:
olfactory, optic, and vestibulochochlear
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mixed:
trigeminal, facial, glossopharyngeal, vagus
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spinal nerves
- 31 pair, all are mixed
- 2 roots
each branches shortly after leaving vertebrae
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dorsal root
sensory; has ganglion containing cell bodies of sensory neurons
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anterior/ventral
motor (no ganglion)
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rami, ramus (singular)
branches of spinal nerves
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dorsal rami
innervate the deep muscles and skin of the back
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ventral rami
innervate everything else, but dont go directly to areas they innervate- they first form plexuses
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plexuses
networks with adjacent nerves
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cervical plexus
- involves C1-C4 and part of C5
- innervates head, neck, upper shoulder
- has motor fibers to diaphragm
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brachial plexus
involves C5-C8; part of T1
innervates upper extremities & rest of shoulders
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lumbar plexus
involves L1- L4(part)
innervates wall of abdomen, skin of external genitalia, part of lower extremities
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sacral plexus
involves L4-L5, S1-S4
innervates buttocks, perineum, most of lower extremities
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thoracic nerves
- generally do not form plexuses
- innervate the intercostals, chest wall, armpit, part of the arm & part of abdominal muscles
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dermatomes
specific segments of skin innervated by specific spinal nerves
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reflex
automatic, unlearned motor response to a stimulus
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component of reflex arc
- 1) receptor
- 2) sensory neuron
- 3) integration center
- 4) motor neuron
- 5) effector
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stretch reflex
- monosynaptic
- receptor muscle spindle
- ipsilateral
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ipsilateral
both sensory & motor impulses originate on the same side of the cord
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reciprocal activation
we relax the muscle that is the antagonist of the one that contracts
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tendon reflex
- polysynaptic
- receptor
- ipsilateral
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flexor reflex
- withdrawl
- polysynaptic
- receptor = nociceptor
- ipsilateral
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crossed extensor reflex
- polysynaptic
- contralateral
- receptors: various proprioceptors
- ex: shifting weight to avoid a fall
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contralateral
sensory impulses on one side of the cord bring about motor responses from the other side
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motor impulse resulting in flexion are sent to stimulated area; motor impulses resulting in extension are sent to the opposite side of the body
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