Motor output

Motor activity integration levels

1. Precommand

2. Projection

3. Segmental

Precommand level

The highest level

Cerebellum and basal nuclei

Programs, unconsious planning, and instructions that are modified by feedback

Ex). Start movements that is then coordinated with postureare

Projection level

The middle level

Motor cortex and brain stem

Highest level of motor consciousnessConveys

Convey instructions to the SC motor neurons, executre action, and sends a copy of that info to higher levels

Segmental level

The lowest level

SC

Contains CPG’s

Reflexes

CPG

Central pattern generators

Ex). Breathing, walking, or swimming

Descending pathways

CNS → Muscles

Characteristics: Decussation, relay, somatotopy, and symmetry

Direct (Pyramidal) descending pathways

Fast, fine, and voluntary movements

Upper + lower motor neurons

Originate in primary motor cortex

Decussate in medulla (lateral) or SC (anterior)

Injury to right motor cortex = paralysis of left side of body

Indirect motor pathways

Regulation of balance and posture

Modify and control SC

Originate in brain stem

Does not decussate or decussates in the midbrain or medulla

Somatic motor output

Innervating skelatol muscle ONLY

Damage to the dorsal root or sensory tracts

Loss of sensation or paresthesias (abnormal sensations)

Damage to the ventral regions or motor tracts

Paralysis

Flaccid paralysis

Damage to the lower motor neurons

Nerve impulses can’t reach muscle

↓ muscle tone

↓ reflexes

Muscle atrophy

Spastic paralysis

Damage to the upper motor neurons

No voluntary movement, but reflex activity continues

↑ muscle tone

↑ reflexes

Babinski +

Quadriplegia

Loss of movement and sensation in all 4 limbs

Cervical region

Paraplegia

Loss of movement and sensation in the lower half of the body

T1 and L1

Amyotrophic lateral sclerosis (ALS)

A progressive neurodegenerative disease where there is no muscle nourishment