Motor System Flashcards
What are the major regions of the cortex involved in descending motor control? Describe their major roles and responsibilities
.primary motor cortex: on button
- premotor cortex: what we choose to do
- supplementary motor area: coordination and execution (quality)
Describe how lateral and medial components of the premotor cortex differ.
lateral components regard external cues (ex. how you reach for a fastball vs slow pitch); mirror motor neurons in this category
medial regard internal cues (gauging force)
What tracts make up the lateral motor systems in the spinal cord?
lateral corticospinal tract
rubrospinal tract
What tracts make up the medial motor systems in the spinal cord?
anterior corticospinal tract
Reticulospinal tract
tectospinal tract
Vestibulospinal tract
What specific aspect of motor control is the lateral corticospinal tract tasked with?
movement of the extremities–especially rapid dexterous movements at digits or joints, modulates myotatic reflexes
What is the internal capsule and what is it known for?
major highway for both ascending and descending pathways (ALL white matter)
What are the borders of the internal capsule?
grey matter borders:
medial: thalamus and caudate
lateral: global pallidus and putamen
What are the different regions of the internal capsule
anterior limb
genu
posterior limb
Describe the basic organization of motor control. What major structures are involved?
Primary Motor cortex (precentral gyrus)
gets things started> supplementary motor area and premotor cortex
What is the function of the anterior limb of the internal capsule?
info from thalamus and brainstem > prefrontal and parietal regions
both ascending somatosensory form SC and assoc w/ emotion, motivation, cog processing, decision-making
what is the function of the posterior limb of the internal capsule?
descending motor fibers from frontal lobe>brainstem and SC
SOMATOTOPICALLY ORGANIZED
what is the purpose of the anterior corticospinal tract?
controls bilateral axial and girdle muscle
what are the primary functions of the rubrospinal tract?
controlling movement of extremities
- modulating flexor tone
- inhibition of anti-gravity muscles (extensors)
- modulation of reflex (think flexor-withdrawal)
what is the function of the reticulospinal tract?
automatic posture and gait-related movements
- pontine: inhibit limb flex and excite ext
- medullary: excite flex and inhibit ext
what is the function of the tectospinal tract? (remember “tectum”)
ctrls coordination of head and eye movement
What is the general distribution of LCST vs ACST within the general Corticospinal Tract?
LCST: 85%
ACST:15%
What types of motor neurons exit the spinal cord and head to the periphery for motor innervation?
alpha motor neurons
What types of motor neurons exit the spinal cord and head to the periphery for motor innervation?
alpha motor neurons
What are the major motor plexi found exiting the spinal cord and where can they be found?
cervical plexus (C3-C5) brachial plexus (C5-T1) lumbar plexus (L1-S4)
what is a myotome?
a group of muscles innervated by a single nerve root
What are the component of the neuromuscular junction (NMJ)
synaptic bouton, cleft, motor end plate
presynaptic cell, cleft, postsynaptic cell
What is the primary neurotransmitter involved in neuromuscular junction function? what breaks it down?
ACh; acetylcholinesterase
List the major steps involved in synaptic transmission at the neuromuscular junction
- AP triggers ACh release into the cleft
- ACh binds to receptors, Na+ channel opens for depolarization
- EPSP causes AP to travel to fiber for contraction
- ACh broken down
what is a motor unit and what are the 3 types?
alpha motor neurons and their assoc muscle fibers; Type 1A(slow), 2A (fast and fatigue-resistant), Type 2b (fast and fatigable)
