A & P - Motor nervous system Flashcards
what does the motor nervous system consist of?
cerebral motor centres
upper motor neurones (UMN)
lower motor neurones (LMN)
in which direction is afferent information sent?
from muscles and sensors to CNS (sensory nervous system)
in which direction is efferent information sent?
from the CNS to muscles (motor nervous system)
what are the functions of the cerebral motor centres?
involved in planning, initiation and regulation of movement
name the cerebral motor centres
primary motor cortex (+ pre-motor) basal ganglia cerebellum brainstem spinal cord
where are upper motor neurones located?
cell body of neurone is in primary motor cortex and synapse onto LMN in spinal cord
where are lower motor neurones located?
cell body in grey matter of spinal cord synapse with muscle
what function does the cerebellum have in the motor nervous system?
balance posture locomotion makes adjustments to movement manual dexterity
what function do the pre-motor areas have in the motor nervous system?
plan complex movement
coordinates movement
what function does the primary motor cortex have in the motor nervous system?
initiates voluntary muscle movement
skilled movements
somatotopic
what function does the basal ganglia have in the motor nervous system?
associated movements
facilitates wanted movements
suppresses unwanted movements
what is the function of the UMNs?
transmit commands from motor cortex to LMNs
UMNs form descending tracts, where?
in white matter of spinal cord
what do UMNs do in the spinal cord?
decussate (cross over) to the opposite side
which part of the motor nervous system can be found in the grey matter of the spinal cord?
cell bodies of MN
interneurons
neuroglia
which part of the motor nervous system can be found in the white matter of the spinal cord?
myelinated and unmyelinated axons organised into ascending and descending tracts
under what control are the motor neurones in the descending tracts of the spinal cord?
somatic
autonomic
which tracts form the cortico-bulbar tract?
lateral cortio-spinal tract
anterior cortio-spinal tract
which tract is involved in he cortio-spinal pathway and what is its function?
cortico-bulbar tract
conscious control of skeletal muscle
where are the cell bodies of the UMNs in the cortio-spinal pathway located and what is their destination?
cell bodies : primary motor cortex
destination : spinal cord LMNs
where in the spinal cord are the cell bodies of LMNs found?
grey matter (ventral horn)
describe the journey of an impulse from along the LMN to the muscle fibre
- myelinated axon exits spinal cord via ventral root
- travels to muscle via peripheral nerve
- On entry to muscle axon splits and synapses with muscle fibre at NMJ
what does a motor unit consist of?
single LMN and all the muscle fibres it innervates
what do small motor units allow for?
fine control movement (eg. eye)
what do large motor units allow for?
strength
how many muscle units innervate 1 muscle fibre?
1
up to how many LMNs can innervate a single muscle?
100
what clinical assessments might be used to judge motor neurological functioning?
observation - posture, symmetry
coordination, balance, proprioception
muscle strength - resistance to applied force
muscle tone - resistance when joints moved passively
deep and superficial reflexes
what is clonus?
rhythmic, involuntary muscle contractions when stretching
how is muscle strength regulated and which is the most important?
- number of active motor units - recruitment
- frequency of action potential - reduced frequency (brief force, twitching)/ increased frequency (sustained increased force (tetani)
RECRUITMENT is most important
what is the ‘simple’ tendon jerk reflex?
single, fast monosynpatic reflex
can the ‘simple’ tendon jerk reflex persist after spinal cord section?
yes
what modulates the ‘simple’ tendon jerk reflex?
higher cerebral centres
what is reciprocal inhibition?
during the stretch reflex the antagonist muscle is often inhibited.
how can the withdrawal reflex be tested?
plantar reflex
Babinski sign
what is the withdrawal reflex?
complex poly-synaptic reflex with longer latency
when is the withdrawal reflex seen?
in response to pain stimulus
what is the withdrawal reflex sometimes accompanied by?
cross extension of extensor muscles in contralateral leg (avoids fall)
what is the withdrawal reflex modulated by?
stimulus intensity
what can nervous motor system lesions cause?
muscle weakness - loss of power/strength
paralysis - complete or partial
what does the following terms mean? hemiplegia, quadriplegia, paraplegia?
hemiplegia - one sided paralysis
quadriplegia - all four limb paralysed
paraplegia - lower body paralysis
what is the difference between myopathy and neuropathy?
myopathy - affects muscle fibres
neuropathy - LMN axon and/or cell body
where can LMN lesions be found?
muscle fibres
LMN axon and/or cell body
what are the symptoms of LMN lesions?
muscle weakness/loss of function
muscle wasting
fasciculation
reduced muscle tone and reflexes
what is fasciculation?
involuntary muscle movements
give an example of a muscle fibre disease (myopathy)
muscular dystrophy
given an example of motor neurone disease
amyotrophic lateral sclerosis
what is Bell’s Palsy?
inflammation of the peripheral nerves
what is Sciatica?
compression of peripheral nerves
where can UMN lesion be found?
axons in descending tract of spinal cord
cell bodies in motor area of brain
what are the symptoms of UMN lesions?
increased muscle tone muscle paralysis/weakness no muscle wasting increased stretch reflexes no fasciculation contralateral signs
