Test 3 Flashcards
What are the 3 routings of somatosensation?
conscious awareness - cerebral cortex
unconscious - cerebrum
emotional and autonomic - limbic
Is conscious awareness multi synaptic? Explain.
touch - discriminative
proprioception - “I know where I’ve been touched”
pain - describe and locate
temp - describe and locate
For the spinal cord tracts, where do sensations of touch and proprioception go?
Back of SC - dorsal columns
For the spinal cord tracts, where do sensations of pain and temperature go?
anterolateral SC
Where are discriminative touch and conscious proprioception located?
touch - SC –> dorsal column
proprioception –> brainstem –> medial lemniscus
Describe the 3 orders of discriminative touch and conscious proprioception.
1st order –> peripheral
sensory receptor
ascends SC into caudal medulla
2nd order –> where fx is contralateral
caudal medulla
crosses to other side
ends in thalamus
3rd order –> to consciousness
synapses in thalamus and heads to the post central gyrus of parietal lobe
Describe the 3 orders of pain and temperature.
1st order - Free N ending –> dorsal horn
synapse
cross
2nd order - dorsal horn - synapse –> thalamus
3rd order - thalamus to cerebral cortex
Describe the 3 orders of emotional &and autonomic pathway.
Divergent
can be a 2 or 3 neuron pathway
What are the three divergent pathways for autonomic and emotional responses?
spinoreticular
spinpmescencephalic
spinoemotional
spinoreticular
regulates arousal
AWAKE
spinomescencephalic
SC –> midbrain
- terminates in midbrain that turns head toward pain
- activates neurons that project from brainstem to SC to shut off pain pathway
spinoemotional
emotional and autonomic
reactionary
alerts autonomic system
Where are the divergent pathways located?
Anterolateral column
parieaqueduct
gray cells around ventricles that send messages back down to sc to modulate pain
What happens in peripheral sensitization?
sensitization of Free N endings
any injury creates a low threshold for AP
easily activated and slightly depolarized
What is the first neurotransmitter in the spinothalamic tract?
glutamate - fast
What is the first neurotransmitter in the divergent pathways?
Substance P
excitatory
prolonged - slow
Explain the 3 aspects of pain experience.
Sensory discriminative - spinothalamic - look, describe
motivational effective - limbic lobe - spino-emotional and spinoreticular - change mood, change emotion
cognitive-evaluative - experience - prefrontal lobes - cerebral cortex
Dorsal horn processing - normal
free N endings depolarized - passes along AP
Dorsal horn processing - suppressed
cannot pass AP as easily
Rubbing suppressed pain synapse
pharmacological
Dorsal horn processing - sensitized (temporary)
neuropathic
easier for temporary amount of time
Dorsal horn processing - reorganized - persistent
neuropathic
LTP - increases spines to increase availability to pass signal –> permanent
I. Periphery
Free N endings - pain receptors
reduce depolarization
stretch, mobilizations, anti-inflammatation, massage
II. Doral Horn (1st synapse of P pathway)
rub it where it hurts
E stim - depolarizes A-Beta
move to activate mechanoreceptors
III. Midbrain descending
signal that returns to site
IV. Hormonal - pituatary
autonomic - dumps chemicals into blood to spread to body
endogenous opioids
V. amygdala and cortex
can turn on inferior levels
THINK LESS PAIN
can turn on endogenous opioids
paresthesia
sensory massage that arises without stimulus of sensory receptors (non-painful)
dysesthesia - allodynia
unpleasant P, spontaneous/evoked
alodynia - unpleasant sensation in response to stimulus that is generally not painful (sunburn)
\
dysesthesia - secondary hyperalgesia
pain that is out of proportion to stimulus creating it
What causes neuropathic pain?
absence of stimulation in free N endings
What are the four mechanisms of neuropathic pain?
ectopic
ephatic
central sensitization
structural reorganization
Describe ectopic pain
stim. in one place put sensation in another
damage to myelination - peripheral axon is killed - injured axon calls for signal - will put ligand/modality gated channels to try and get axon - will now get stimulation inappropriately
Describe ephatic pain
short circuit
demyelination between sensation neuron and pain neuron allows a jump of AP
= stimulation on pain when sensation reaches threshold
Describe central sensitization.
Learns P
When there is a strong or long P signal body reorganizes cell to better receive/transmit P signal so P is increased
possible mechanism for hyperalgesia
maladaptive - feel pain inappropriately
Describe structural reorganization.
central axon backs off
of P neuron and away from synapse
2nd order pain neuron has lost input
touch neuron innervates/re-establishes synapse on P
How do central neurons generate Neuropathic P?
If an injured body part receives signal from collateral sprouting.
Phantom sensation and phantom pain
General process of Motor System
decision to move plan to move control to move motor tracts UMN -SC motor neurons LMN - peripheral
myofibril
elongated contractile material in the muscle
sarcomeres
contractors of m
z-line: structural end of m
m-line: where myosin hangs
titin: the rubber band that resists overstretch that may cause damage from one end of sarcomere to other
myofilaments
actin and myosin
actin climbs myosin by way of Ca 2+ to make m contract
How does an AP occur in the muscle
A-Alpha brings All- EPSP- cell is depolarized
if Ca is released- actin climbs myosin, all sarcomere shorten
What causes a contracture?
when titan will not let go of myosin
What may cause total m resistance to stretch?
*****
titin’s elasticity has reached it’s limit - active contraction
actin is continually pulling on myosin- cross-bridges form
Number of sarcomeres adapt to length
What does it mean if a muscle contraction is involuntary?
pathological
Where are motor neurons?
begin in cell body of spinal cord and synapse in m
Where are motor neurons located in the cell body?
the ventral horn
In the horizontal organization of motor neurons, what is medial? Lateral? Anterior? Posterior?
medial – axial and proximal Mm
Lateral – distal Mm
Anterior – extensors Mm
Flexors – Flexor Mm
How is the vertical organization of motor neurons coordinated?
all cell that contribute to a particular M –> cluster into a vertical pool
Which motor neuron contracts M?
A-Alpha
Which motor neuron keeps intrafusal muscle spindles sensitive?
A-gamma
What is the afferent axon from Mm spindles?
1a
What does a motor unit consist of?
1 LMN and all M fibers it connects to
Describe what a slow twitch fiber is? size? metabolism? tension? fatigue?
small A-Alpha
oxidative
low tension
fatigue resistent
Describe fast twitch muscle fibers size? metabolism? tension? fatigue?
large A-Alpha
glycolytic
high tension
fatigue in first few moments used
What is the order of recruitment for muscle fibers?
slow twitch first –> fast twitch only called if movement requires strength and power (Hennemans size principle)
Which muscle fibers are easiest to depolarize?
slow twitch small A-alphas
How come we can use fast twitch for more than a few moments if they fatigue so easily?
Our conscious brain changes the demand on which fast twitch muscle fiber is used so they are rotated to reduce fatigue
How does 1 alpha neuron receive information?
convergence
brain and sensory receptor
deep tendon pressure inhibits alpha 1 neurons
What is a muscle cramp?
no neural input leading to involuntary contraction
electrolyte
overworked
motor neuron dz - fewer motor units - fatigue
What is a fasciculation?
spontaneous depolarization of a motor neuron
myoclonus
whole body jerk
fibrillations
one single m fiber depolarization
paresis and paralysis
paresis - weak - SN
paralysis - inability - PN
disuse atrophy
small, no definition
denervation atrophy
wither away to nothing
hypotonic
loss of some
flaccidity
peripheral N loss - loss of all M tone
“flaccid paralysis”
loss of m tone and inability to contract, damage to motor neuron
