16.4 Flashcards
lower motor neurons
all excitatory & inhibitory signals that control movement converge on these motor neurons that extend out of the brainstem & spinal cord to innervate skeletal muscles in the body
Where are the cell bodies located in lower motor neurons?
in the lower parts of the CNS ( brainstem and spinal cord)
from the brainstem, axons of LMNs extend through _____ to innervate skeletal muscles of the face & head
cranial nerves
from the spinal cord axons of LMNs extend through ____ to innervate skeletal muscles of the limbs & trunk
spinal nerves
why are the LMNs called the final common pathway?
Only LMNs provide output from the CNS to skeletal muscle fibers
input arrives at lower motor neurons from nearby interneurons called
local circuit neurons
where are local circuit neurons located>
close to the lower motor neurone cell bodies in the brainstem and spinal cord
what do local circuit neurons function
help coordinate rhythmic activity in specific muscle groups such as alternating flexion and extension of the lower limbs during walking
both local circuit neurons & lower motor neurons receive input from?
Upper motor neurons
Upper motor neurons are located where? 2 places
cerebral cortex - planning & execution of voluntary movements of body
motor centres of brainstem - help regulate posture, balance, muscle tone & reflective movements of the head and trunk
Which neurons assist with movement by providing input to upper motor neurons?
Basal nuclei neurons
Neural circuits interconnect the basal nuclei with motor areas of the cerebral cortex (via the thalamus) and brainstem. What do these circuits help with?
Initiating and terminating movements, suppress unwanted movements, and establish a normal level of muscle tone
Cerebellar neurons?
also aid movement by controlling the activity of upper motor neurons
neural cicuits interconnect the cerebellum with motor areas of the cerebral cortex (via the thalamus) and brainstem. A prime function of the cerebellum is to
monitor differences between intended movements & movements performed. Then it issues commands to UMN to reduce errors in movement
control of body movements involves motor pathways that begin in motor areas of the cerebral cortex. 2 areas are the?
Premotor area (area 6 in frontal lobe)
primary motor are (area 4 in the precentral gyrus of frontal lobe)
The role of the premotor area in body movements? steps
- desire to move a part of body generated in one or more cortical association areas (such as prefrontal cortex, somatosensory association are, auditory association area or visual association area)
- this info sent to basal nuclei which processes the info & sends to thalamus and then to premotor area where a motor plan is developed
- the plan identifies which muscle should contract, how much they need to contract and in which order.
- from the premotor are the plan is transmitted to the primary motor are for execution
which area is the major control region for the execution of voluntary movements?
the primary motor area
electrical stimulation of any point in the primary motor area causes>
contraction of specific muscles on opposite side of the body
motor homunculus
distorted muscle map of the body which is present in the primary motor area (each point within the area controls muscle fibres in different parts of the body)
which pathway provides input to the lower motor neurons via axons that extend directly from the cerebral cortex
direct motor pathways
which pathway provides input to the lower motor neurons from motor centres in the brainstem?
indirect motor pathways
action potentials for voluntary movements propagate from the cerebral cortex to lower motor neurons via ?
direct motor pathways
the direct motor pathways (also known as pyramidal pathways) consist of axons that descend from>
pyramidal cells of the primary motor area and premotor area
the main output cells of the cerebral cortex?
pyramidal cells (upper motor neurons that have pyramid shaped cell bodies)
direct motor pathways (2 types)
corticospinal pathways and corticobulbar pathway
which pathway conduct impulses for the control of muscles of the limbs and the trunk
corticospinal pathways
axons of upper motor neurons in the cerebral cortex form the?
corticospinal tracts –> which descend through the internal capsule of the cerebrum & the cerebral peddle of the midbrain
which corticospinal tract conveys nerve impulses from motor cortex to skeletal muscles on opposite side of body for precise voluntary movements of distal parts of limbs (ex buttoning a shirt)
lateral corticospinal tract
corticospinal axons that decussate in the medulla form the
lateral corticospinal tract in the lateral white column of the spinal cord
corticospinal axons that do not decussate in the medulla form the ___
anterior corticospinal tract in the anterior white column of the spinal cord
conveys nerve impulses from the motor cortex to skeletal muscles on opposite sides of the body for movements of trunk and proximal part of limbs
anterior corticospinal tracts
corticobulbar pathway
conducts impulses for the control of skeletal muscles in the head
axons of UMNs descend from the cortex into brainstem where some decussate & others do not. They provide input to lower motor neurons in the nuclei of the oculomotor (III), trochlear (IV), trigeminal (V), abducens (VI), facial (VII), glossopharyngeal (IX), vagus (X), accessory (XI), and hypoglassal (XII) nerves. which control?
voluntary movements of the eyes, tongue and neck, chewing, facial expression, and speech
the brainstem is another region important to motor control. It contains 4 major centres that help regulate body movements which are>
- vestibular nuclei - in the medulla & pons
- reticular formation - located throughout brainstem
- superior colliculus - in the midbrain
- red nucleus - in midbrain
The brainstem motor centres give rise too?
indirect motor pathways (also known as extrapyramidal pathways)
include all somatic motor tracts other than the corticospinal & corticobulbar tracts
the indirect motor pathways convey action potentials from the brainstem to cause what kind of movements
involvuntary movements that regulate posture, balance, muscle tone & reflective movements of the head and trunk
the vestibular nuclei play an important role in regulation of?
posture
Where do vestibular nuclei receive neural input from?
vestibulocochlear (VIII) nerve regarding the state of equilibrium of the body and neural input from the cerebellum
in response to the input, the vestibular nuclei generate action potentials along axons of the ______ tract which conveys signals to ____ muscles of the trunk and _____ parts of the limbs
vestibulospinal tract, skeletal, proximal
rubrospinal pathway
conveys nerve impulses from red nucleus (which receives input from the cerebral cortex and cerebellum) to contralateral skeletal muscles that govern precise voluntary movements of distal parts of upper limbs
which pathway Conveys nerve impulses from superior colliculus to contralateral skeletal muscles that reflexively move head, eyes, and trunk in response to visual or auditory stimuli.
tectospinal pathway
which pathway Conveys nerve impulses from vestibular nucleus (which receives input about head movements from inner ear) to ipsilateral skeletal muscles of trunk and proximal parts of limbs for maintaining posture and balance in response to head movements.
vestibulospinal pathway
which pathway Conveys nerve impulses from reticular formation to ipsilateral skeletal muscles of trunk and proximal parts of limbs for maintaining posture and regulating muscle tone in response to ongoing body movements.
lateral & medial reticulospinal pathways
Basal nuclei functions
initiation of movements
suppression of unwanted movements
regulation of muscle tone
regulation of non motor processes
