Somatic Motor Pathways

Question 1

Motor portions of cerebral cortex

Answer 1

Initiate and control precise movements

Question 2

Basal ganglia

Answer 2

Establish muscle tone and integrate semivoluntary automatic movements

Inhibits unwanted movement

Question 3

Cerebellum

Answer 3

Smooth out movements; maintain posture and balance

Question 4

Lower motor neurons

Answer 4

Extend from brain stem or spinal cord, through spinal or cranial nerves, to skeletal muscles
AKA final common pathway

Question 5

Why are LMNs also called Final Common Pathways

Answer 5

Because many regulatory mechanisms converge on these peripheral neurons

Question 6

How to UMNs extend from brain to LMNs?

Answer 6

Direct and indirect pathways

Question 7

Direct pathway

Answer 7

AKA pyramidal pathways
Cerebral cortex through spinal cord and out to muscles
Voluntary

Question 8

Indirect pathways

Answer 8

Provide input from basal nuclei, cerebellum, and cerebral cortex

Question 9

Four components of Somatic Motor Pathways

Answer 9

1. local circuit neurons
2. upper motor neurons
3. basal nuclei neurons
4. cerebellar neurons

Question 10

Local Circuit Neurons

Answer 10

Interneurons.
Receive input from somatic sensory receptors and from higher centres in brain.
Help coordinate rhythmic activity in specific muscle groups

Question 11

Upper Motor Neurons

Answer 11

Communicate with both local circuit neurons (mostly) and LMNs
UMN from cerebral cortex essential for voluntary movements
Others originate in motor centres of the brain stem

Influenced by basal nuclei and cerebellum

Question 12

Motor centres of brain stem

Answer 12

Red nucleus
Vestibular nucleus
Superior colliculus
Reticular formation

Question 13

UMNs from the brain stem regulate

Answer 13

Muscle tone
Postural muscles
Balance
Orientation of the head and body

Question 14

Basal nuclei neurons

Answer 14

Assist movement by providing input to UMN
Interconnected with cerebral cortex (via thalamus) and brain stem.
Initiation and termination of movements
Suppress unwanted movements
Establish muscle tone

Question 15

Cerebellar Neurons

Answer 15

Control activity of UMN
Interconnected with cerebral cortex (via thalamus) and brain stem
Monitors difference between intended movements and actual movements, then corrects
–> coordinates movements and helps maintain posture and balance

Question 16

What percentage of fibres decussate at pyramid?

Answer 16

90%

Question 17

Lateral Corticospinal Tract

Answer 17

The 90% of Corticospinal fibres that decussate.

Control muscles for fine precise and highly skilled movement.

Synapse with LMN in anterior grey horn

Question 18

Anterior Corticospinal Tract

Answer 18

10% of the axons that don’t decussate in the medulla.

Movement of neck and trunk
Coordination of axial movement

Cross over at level of LMN synapse

Synapse with LMN or internet ribs in anterior grey horn

Question 19

Corticobulbar Tract

Answer 19

Control skeletal muscles of head

Cerebral cortex –> descend through internal capsule of cerebrum and cerebral peduncle of midbrain –> motor nuclei of CN 3, 4, 5, 6, 7, 9, 10, 11, 12.

Control precise, voluntary movement of eye, tongue, neck; swallowing, chewing, facial expression, speech.

Some decussate. Some don’t.

Question 20

Primary Motor Cortex

Answer 20

Precentral gyrus

Plan and initiate voluntary movement

Question 21

Flaccid paralysis

Answer 21

Damage to LMN
Voluntary movement
Ipsilateral
No reflex action

Question 22

Spastic paralysis

Answer 22

Damage to UMN
Contralateral
Exaggerated reflex

Question 23

Indirect pathways

Answer 23

All somatic motor tracts except corticobulbar and corticospinal

Involve motor cortex, basal ganglia,thalamus, cerebellum, RAS

Question 24

Five indirect tracts

Answer 24

Rubrospinal
Tectospinal
Vestibulospinal
Lateral reticulospinal
Medial reticulospinal

Question 25

Rubrospinal tract

Answer 25

Extrapyramidal/indirect tract Red nucleus --> CL skeletal muscle Precise movements of distal upper limb; muscle tone.

Question 26

Tectospinal tract

Answer 26

Indirect/extrapyramidal Superior colliculus --> CL skeletal muscle Movement of head and eyes in response to visual stimuli.

Question 27

Vestibulospinal Tract

Answer 27

Indirect/extrapyramidal Vestibular nucleus (CN VIII) in medulla to ipsilateral muscles Balance in response to head movement

Question 28

Lateral reticulospinal

Answer 28

Extrapyramidal/indirect RAS --> increase flexor reflexes, inhibit extensor reflexes, decrease axial and proximal limb muscle tone

Question 29

Medial reticulospinal

Answer 29

Extrapyramidal/indirect RAS --> increase extensor reflexes, inhibit flexor reflexes, increase axial and proximal limb muscle tone

Question 30

Final response of skeletal muscle determined by

Answer 30

Sum total of inhibitory and excitatory signals coming from all the UMN.

Question 31

Sleep and wakefulness are controlled by

Answer 31

Reticular activating system

Question 32

RAS is activated by what types of | I put

Answer 32

All sensory except olfaction.

Question 33

Circadian rhythm is determined by the

Answer 33

Hypothalamus

Question 34

Sleep has how many stages

Answer 34

Five | Four nonREM/slow wave + one REM

Question 35

Stage 1 of sleep

Answer 35

Drifting to sleep | Hypnic jerk occurs then

Question 36

Stage 2 of sleep

Answer 36

Fragments of dream | Eyes roll side to side

Question 37

Stage 3 of sleep

Answer 37

Very relaxed. Moderately deep. BP and T° drop.

Question 38

Stage 4 of sleep

Answer 38

Deep sleep Bedwetting, sleep walking

Question 39

REM sleep

Answer 39

Most neural activity and O2 use. | Most dreams occur

Question 40

Plasticity

Answer 40

The capacity for the brain to change with learning.

Question 41

Intermediate memory

Answer 41

Recall for a few seconds

Question 42

Short term memory

Answer 42

Seconds to hours | Electrical and chemical

Question 43

Long term memory

Answer 43

Days to years | Anatomical and biochemical changes

Question 44

Anterograde amnesia

Answer 44

Inability to create new memories

Question 45

Retrograde amnesia

Answer 45

Inability to recall memories from before the event.

Question 46

Damage to basal ganglia

Answer 46

Uncontrollable abnormal body movement Possible muscle rigidity and tremors Parkinson's. Huntington.

Question 47

Cortex --> basal ganglia --> thalamus --> cortex circuit

Answer 47

Initiates and terminates movement.

Question 48

Basal ganglia --> reticular formation

Answer 48

Reduces muscle tone

Question 49

Four aspects of cerebellar function.

Answer 49

1. Monitoring movement intent (command signals from motor cortex and BN via pons) 2. Monitoring actual movement (sensory info) 3. Comparing 1 & 2 4. Correcting as necessary (via thalamus to cerebral cortex)