Phys II - Motor Control

What part of the brain is responsible for conscious control by higher brain centers and voluntary actions?

Primary motor cortex

What controls learned patterns of movement?

Basal nuclei/ganglia

What controls maintenance of posture and muscle tone?

Extrapyramidal tracts and muscle spindles

What coordinates involuntary reflexes?

Spinal cord

Where are coordinated actions that are reliant in the sensory motor integration processed?

Cerebellu

What is the origin of the corticospinal (pyramidal) tracts?

Primary

Where are upper motor neurons found?

primary motor cortex

What is the function of the cerebellum?

coordination of smooth motor activity

What is the function of the basal nuclei?

coordinate inhibition/activation of the motor cortex

What is the function of the pre-motor and supplementary motor cortex?

prepare patterns of movement for primary motor cortex

planning and sequential movements

Where does the pre-motor and supplementary motor cortex receive information from?

Basal nuclei and cerebellum via thalamus

What is the function of the s

Where is the primary motor area located?

pre-central gyrus of the frontal lobe

What Brodmann’s area makes up the primary motor cortex?

BA 4

What is half of the primary motor cortex devoted to?

Muscles controlling hands, face, and speech

What are the output cells of the primary motor corte

What tract are Betz cells involved in?

Corticospinal (pyramidal) tract

What occurs with surgical removal of the primary motor cortex?

loss of discrete control of movement in distal extremities

T/F: Gross movement is spared when even without the primary motor cortex.

True

Where do corticospinal tract fibers originate?

Pre/supplementary motor cortex (30%)

Primary sensory cortex (40%)

Describe the giant Betz cells.

Very large myelinated fibers

3% of fibers in corticospinal tracts

97% of fibers contribute to ‘background tonic signals’

What are the other output cells of the primary motor cortex?

Corticobulbar cells

Inferior olivary nucleus and pontine nuclei

Extrapyramidal

Where do the inferior olivary nucleus and pontine nuclei output to (from the primary motor cortex)?

Cerebellum

What are the incoming sensory pathways to the motor cortex?

Subcortical fibers from:

• adjacent areas of cortex

• somatic sensory areas (via thalamus)

• Visual and auditory cortex (via thalamus)

• Opposite hemisphere which pass through the corpus callosum

Where do nuclei of thalamus coordinate function between?

Motor cortex, basal ganglia, and cerebellum

Where do incoming sensory fibers come from that go to the motor cortex?

Intralaminar nuclei of thalamus

What is the starting point of voluntary motor control pathways?

Motor cortex

What is the major pathway for controlled/precise output from the motor cortex?

Corticospinal (pyramidal) tract

Where are the axons of the Betz cells found?

internal capsule

What kind of stimuli guides the premotor area?

External stimuli

What is the function of the premotor area?

mirror neurons (mimic m

What function does the supplementary motor area have?

learning and planning (mental rehearsal)

Which region does the supplementary motor area work with to provide positional movement for the body?

premotor area

What area provides the background for find motor control of the arms and hands by primary motor cortex?

Supplementary motor area

What area is damaged if a patient presents with the inability to smile evenly when asked BUT can smile when told a joke?

Supplemental area

Function of Broca’s area

motor production of speech

What does motor apraxia cause?

inability to perform fine hand movements if the hand skills area is damaged

What is Wernicke’s area responsible for?

language comprehension

Where is Wernicke’s area located?

left temporal lobe

What does damage to Broca’s area cause?

non-fluent aphasia

What does damage to Wernicke’s area cause?

fluent aphasia

Which tracts make up the pyramidal tracts?

Lateral and anterior corticospinal

What is the function of the pyramidal tracts?

modulate (inhibit) unintended movement

Where do the signals from the pyramidal tracts go?

Descend to directly influence lower motor neurons

Where do the corticospinal tracts cross?

point where spinal cord begins

What kind of neurons make up the lateral AND ventral corticospinal tracts?

upper motor neurons

What is the function of the lateral corticospinal tract?What

appendicular muscle control

What is the function of the ventral corticospinal tract?

axial muscle control (ends in mid thoracic)

What kind of control does the lateral corticospinal tract have?

Fine

What kind of control does the ventral corticospinal tract have?

Gross

T/F: All fibers cross in the lateral corticospinal tract.

True

Where do fibers from the lateral corticospinal tract cross?

junction where medulla becomes spinal cord

How many of the ventral corticospinal tracts corss?

50%

Where do the ventral corticospinal tracts cross?

What is the result of an upper motor neuron lesion?

spastic, hyper-reflexia

What is the result of a lower motor neuron lesion?

Flaccid paralysis, hypo-reflexia

What does damage of the primary motor cortex result in?

Stimulatory function: loss of voluntary control

Inhibitory function: loss of inhibition of unintended movements

Result of lesion of the motor cortex

Loss of voluntary control

Loss of inhibition

Result - spastic paralysis

Where do outgoing cortical motor signals go on the indirect pathway from the motor cortex?

Brainstem nuclei (extrapyramidal)

Basal ganglia and cerebellum

What is the extrapyramidal control of motor function by the brainstem?

Posture

Gross extensors and flexors

What kind of centers does the brainstem have?

repetitive movement and equilibrium

What do the vestibular nuclei and tracts activate?

anti-gravity and extensors (ipsilateral)

What do the pontine-reticular nuclei and tracts activate?

anti-gravity and extensors (ipsilateral)

What do the red nuclei and rubrospinal tract activate?

anti-extensors (flexor dominant) (contralateral)

What extremities are primarily activated in the red nuclei and rubrospinal tract?

Upper extremity

What is activated by the medullary-reticular nuclei and tract?

Anti-extensors (flexor dominant) (bilateral)

What happens when the vestibular and pontine reticular nuclei are unopposed?

produce extension

What tracts do the vestibular and pontine reticular nuclei activate and send signals down?

Lateral vestibulospinal and pontine-reticulospinal

Where does the rubrospinal tract cross?

midbrain

In the rubrospinal tract, where do primary motor cortex fibers synapse?

Red nucleus

What is the rubrospinal tract a strong stimulatorof?

m

What does the rubrospinal tract inhibit?

Antigravity activation of pontine reticulospinal tract

What functions does the rubrospinal tract have?

postural and fine motor control

What can some primates use for fine motor control after injury to corticospinal tracts?

Rubrospinal tract

What signals does the medullary reticular nuclei transmit?

inhibitory signals to antigravity muscles thru medullary (lateral) reticulospinal tract

What is the origin of the tectospinal tract?

Superior colliculus of midbrain (tectum)

What pathways is the tectospinal

What reflexes is the tectospinal tract involved in?

visual, auditory, and startle

Where is the tectospinal tract found?

ONLY in cervical spine

What does the tectospinal tract contribute to?

neck movement in response to visual stimuli

Where does the tectospinal tract cross?

brainstem (dorsal tegmentum)

What tone is increased with a decorticate injury?

flexor tone

How does a decorticate injury occur?

damage between cortex and red nucleus

loss of cortical inhibition of red nucleus produces upper extremity flexion

What tone is increased with a decerebrate injury?

Extensor tone

How does a decerebrate injury occur?

damage between red nucleus and vestibular/pontine-reticular nucleus

loss of rubrospinal inhibition of vestibular/pontine-reticulospinal tracts

What are interneurons used for?

Reflexes

Pain modulation

What are gamma motor neurons associated with?

Muscle spindles

Where do descending motor fibers synapse?

Lower motor neuron within ventral gray horn of cored

What do large alpha motoneurons supply?

extrafusal fibers/large movement-producing muscle fibers

What do smaller gamma motoneruons supply?

Intrafusal fibers and muscle spindles.

What cell bodies are found in the lateral gray horn from T1-L2?

Cell bodies for pre-ganglionic sympathetic fibers

What cell bodies are found in the lateral gray horn from S2-S4?

cell bodies for pre-ganglionic parasympathetic fibers

What are some features of intrinsic reflexes?

Involuntary and predictable

What is another name for the deep tendon reflex?

stretch reflex

What are some examples of intrinsic reflexes?

Deep tendon reflexes

Golgi tendon reflex

Pain withdrawal

What are some features of acquired reflexes?

involuntary, learned only after repetition

Ex: athletic movements, driving car

What five components do reflexes require?

1. Sensory receptor

2. Sensory neuron

3. Interneuron(s) within spinal cord gray

4. Motor neuron

5. Effector: skeletal muscle (somatic) or gland (visceral)

What kind of responses are produced from the stretch reflex?

Dynamic response

Static response

Describe a dynamic response

Quick stretch on nuclear bag (muscle spindle) triggers quick contraction of muscle)

Describe a static response

static stretch on muscle spindle triggers sustained contraction of muscle

from muscle spindle - nuclear chain fibers and Type II afferents