Dr. Johnson & Dr. Hayward's lectures Flashcards
relationship btw spinal cord and vertebral column
there is a mismatch. there is one more cervical spinal segment than vertebral segment (8 vs 7). the spinal cord ends after vertebral L6, then the dorsal and ventral roots form the cauda equina
divergence
• Divergence: one presynaptic neuron may synapse with a few to many thousand postsynaptic neurons
convergence
• Convergence: neurons can have input from several other neurons
withdrawl (nociceptive) reflex vs. acute pain perception
- with acute pain the patient will turn their head, cry out, or try to bite
- the withdrawl/nociceptive reflex is only dependent on the completion of the reflex arc in the spinal cord.
- a pain response REQUIRES that the information travels to the CEREBRAL CORTEX
A-beta receptors
myelinated, convey touch - cutaneous receptors
A-delta receptors
myelinated, convey pain, touch, and temp - cutaneous receptors
C receptors
unmyelinated, convey pain - cutaneous receptors
spinal pathway - upper body
DRG>cuneate funiculus>cuneate nucleus (synapse here)>internal arcuate fibers>medial lemniscus>VCL>internal capsule>somatosensory cortex
spinal pathway - lower body
DRG>gracile funiculus>gracile nucleus (synapse here)>internal arcuate fibers>medial lemniscus>VCL>internal capsule>somatosensory cortex
test for conscious proprioception
tactile placing response
-when an animal’s foot is placed on the dorsal surface it will lift the foot and plant the palmar surface on the ground. requires intact CORTEX and consciousness
pain
a sensory perception of a nociceptive event (consciousness/cerebral cortex)
pain - sensory type
discriminative
pain - motivational type
affective dimension
nociception
encoding and processing of harmful stimuli in the nervous system (the ability of a body to sense potential harm)
nociceptors
have free nerve endigns in skin and viscera
nociceptor fibers
A delta and C
T/F: nociceptors have high activation thresholds, increase their response magnitude throughout noxious range
True
spinal -descending pathway
somatic sensory cortex>midbrain periaqueductal gray>dorsal horn of spinal cord>ascending nociceptive pathways
parasympathetic division of ANS
craniosacral origin, rest & digest, postganglionic neurotransmitter is ACh
sympathetic division of ANS
thoracolumbar origin, fight or flight, postganglionic neurotranmitter is ANS-division specific
visceral pain
poorly localized, blockage in a hollow organ, stretch of capsule in a solid organ
referred pain
due to overlying serosal inflammation of viscerosomatic convergence
rheobase:
the lowest possible stimulus that will elicit an AP
chronaxie:
2x rheobase (the minimum time required for an electric current double the strength of the rheobase to stimulate a muscle)
absolute refractory period
time during which an AP can be generated with a greater than normal stimulus
If you shift concentrations of Na+ in
depolarization
If you shift concentrations of Na+ out
hyperpolarization
If you shift concentrations of K+ in
hyperpolarization
If you shift concentrations of K+ out
depolarization
axon conduction velocity
dependent on axon membrane capacitance and internal resistance
salutatory conduction
made possible by properties of the lipid material in the myelin sheath
action potential vs. general potential
- action potential is “all or nothing”
- generator potential is graded, increasing in amplitude with increasing stimulus intensity, no refractory period
The influx of ______ triggers the release of quanta into the synaptic cleft
Ca2+
EPSP:
the neurotransmitter acts by briefly increasing the permeability of the post synaptic membrane primarily to Na+ and K+
IPSP:
inhibitory neurotransmitters bind to receptors that increase the permeability of the post synaptic membrane to Cl-; Cl- flows into the cell, hyperpolarizing the local membrane
excitatory post synaptic potentials
inward flux of Na+ is greater than the outward flux of K+ , leadng to a breif depolarization,
inhibitory post synaptic potentials
associated with the presynaptic release of inhibitory neurotransmitters that results in a transient hyperpolarization of the post synaptic membrane
