4 - Locomotion and Movement

What is a moment (torque) and how is it calculated

A moment is a rotational force around a joint

M=F*r

M = moment (Nm)

F = force (in Newtons)

r = moment arm (the perpendicular distance from the axis of rotation to the line of action of the force) (In metres)

What is a motor unit (again)

A motor unit consists of one motor neuron, its motor axon and all muscle fibres it innervates

What is motor control and what are the multiple brain regions

Motor control is voluntary movement that begins through activity in multiple brain regions

PRIMARY MOTOR COTREX : initiates/executes movements

• initiation/execution of motor plans by developing a program of commands for lower motor neurons

• ~60% of upper motor neurons originate here

PREMOTOR CORTICES : plans/selects complex movements

• Planning complex movements

• Selecting movements

• Postural preparation

• Processing visual information

SUPPLEMENTARY MOTOR AREA : plants movement sequences

• helps plan sequence of muscle contractions

• Plans extent of contractions required for movement

POST PARIETAL CORTEX : sensory/body-environment map

• uses sensory information to create a conscious map of the body and its relationship with its surroundings

What are the three main descending motor pathways

CORTICOSPINAL PATHWAY : motor cortex → spinal chord

mainly controls - voluntary movement of trunk and limbs

CORTICOBULBAR PATHWAY : motor cortex → brainstem

Controls - voluntary movement of face and head

EXTRAPYRAMIDAL PATHWAYS : brainstem → spinal chord

Important for - posture, balance, muscle tone

What are the steps to a corticospinal pathway?

1. Command begins at primary motor cortex

2. Signal travels to upper motor neurons through brainstem

3. Most fibres cross over at the pyramids

4. Fibres continue in the lateral or anterior corticospinal tracts

5. Upper motor neurons synapse with lower motor neurons

6. Lower motor neurons directly activate skeletal muscles

What are the lateral and anterior tract of the corticospinal tracts

LATERAL TRACT (90% of CORTICOSPINAL tract)

• innervates the limbs

ANTERIOR TRACT (10% of the CORTIOSPINAL tract)

• innervates axial muscles (neck, thoracic and abdominal)

Describe the different stages of the gait cycle

GAIT CYCLE

• measured from initial contact → next initial contact

• Foot contact or heel strike

TOE OFF : foot leaves the ground

STANCE PHASE : the limb of interest is on the ground

SWING PHASE : the limb of interest is off the ground

DOUBLE SUPPORT : both feet on the ground

SINGLE SUPPORT : one foot on the ground

What are central pattern generators

A central pattern generator is a neural circuit within the spinal chord

Generates rhythmic motor patters without requiring continuous cortical input

What is the difference between Cortical control and central pattern generators

COTRICAL CONTROL

• generates voluntary movement

• Requires conscious intention

• Cortex = Driver

CENTRAL PATTERN GENERATORS

• generates rhythmic locomotion

• Can operate largely automatically

• CPG = engine

What are the main differences between walking and running gait cycle

• In running, we do not benefit from the exchange of forward kinetic energy and gravitational potential energy, but instead store and release elastic potential energy in our muscles and tendons as they stretch and recoil

• Running has support phase + flight phase (no double support)