Exam 2 Study Guide Flashcards
Where are cell bodies of UMN?
- cerebral cortex
- brainstem
Where do UMN axons travel?
in pyramidal tracts
UMN axons synapse with
- interneurons
- LMN
in brainstem or SC
LMN cell bodies are located here (big picture)
- spinal cord
- brainstem
alpha LMNs innervate
extrafusal fibers
gamma LMNs innervate
intrafusal fibers
coactivation of alpha and gamma LMN
maintain stretch on intrafusal fibers while extrafusal fibers contract
mechanisms of sensory contribution to motor systems
- feedback
- feedforward
feedforward
anticipatory use of sensory info to prepare for movement
feedback
use of sensory info during or after movement to make corrections to ongoing movement or future movements
When does neural transmission to a muscle fiber stop?
when ACH is removed from the synaptic cleft
How does ACH removal occur?
- diffusion away from the synapse
- broken down by acetylcholinesterase to acetic acid and choline
sequence of events that converts APs in a muscle fiber to a contraction
excitation contraction coupling
2 terminal cisternae + 1 t-tubule
triad
motor pathway overall
- decision from frontal cortex
- motor planning areas
- control circuits
- UMN conducts signals to LMN and interneurons
- LMN » skeletal muscles
amount of tension in a muscle at rest
OR
amount of resistance to passive stretch exerted by a resting muscle
tone
How is tone acquired?
- weak actin-myosin bonds
- titin
- active contraction
How do muscles adapt to changes in length?
They are plastic/adaptable. When contracted or extended for a period of time, they either lose or gain sarcomeres
What happens to someone who has had their arm in a cast or sling for 6 weeks?
- contracture
- greater resistance to stretch
What happens to someone who suffers from spasticity (as in CP)?
- muscle more difficult to stretch
- spastic co-contraction makes it hard to walk
How does the spinal region contribute to movement?
- reflexes
- stepping pattern generators
- inhibitory interneuron circuits
Activation of ceruleospinal and raphespinal tracts produces
produce a generalized increase in activity of
- spinal interneurons
- motor neurons
contribution of ceruleospinal and raphespinal tracts overall
may contribute to poorer motor performance when anxiety is high
ceruleopinal and raphespinal tracts (example)
Climbers on a high wall move more slowly, make more exploratory movements, and use each hold longer than those on a lower climbing wall
What reduces the rate of postural adjustments?
fear
paresis
partial loss of voluntary movements
paralysis
total loss of voluntary movements
muscle atrophy
loss of muscle bulk
2 types of atrophy
- disuse
- neurogenic
disuse atrophy
lack of muscle use
neurogenic atrophy
damage to nervous system
spasm
sudden, involuntary contraction of muscle fibers
cramp
severe, painful muscle spasm
fasciculations
- quick twitches of muscle fibers of single motor units
- visible on surface of skin
hypotonia caused by
- LMN lesions
- acute UMN lesions
hypertonia caused by
chronic UMN lesions
hyperreflexia
UMN problem
- loss of inhibitory corticospinal input
- excessive interneuron and LMN activity
hyporeflexia
LMN problem
