A VERY brief intro to functional anatomy and biomechanics

Objectives

  How we move Neuro-MSK

  Sensorimotor

  Planes of motion, anatomical terms

  Centre of mass- Segment and System

  Lever mechanics à Moment Arm

  Force Vectors à Summative forces

Brief story of how we produce motion

  Motor cortex initiates signal à descending spinal cord tracts à Peripheral motor nerve à Motor point in muscle to initiate contraction (concentric/eccentric/isometric) à muscle acts through tendon to move or stabilize bone in adjacent segment

  Sensors exist in tendon/muscle/fascia àperipheral sensory nerve à ascending spinal cord tracts à sensory cortex/cerebellum

  3 Major types of sensorimotor control

Sensorimotor Control

  Levels of Sensorimotor Control

Sensorimotor Control

  Spinal Regulation

Sensorimotor Control

  Subcortical (below cortex)   Brain Stem, Thalamus, Hypothalamus, Vestibular and

Cerebellum

  Equilibrium, automatic postural righting/balance corrections

Subcortical Control

  Vestibular- Inner ear semicircular canals

  Cerebellar- spinocerebellar tracts relay subconscious info

  Brain Stem

  All relay info to cortical control as well

Cortical Level

  Highest level of control also the newest in evolutionary terms (most fragile)

  Initiate and control complex and voluntary movements

  Three Levels   Primary motor cortex- receives proprioception info

  Premotor- organizes and prepares movement

  Supplemental motor area- programs groups of muscles for complex movement

Sensorimotor Input

Motor Output

  Motor units- muscle fibres associated with a single motor neuron

  Alpha motor neurons- relay voluntary motor commands

  Gamma motor neurons- controlled by intrafusal muscle spindle afferents

  Efferent signal (outward) summative effect of inhibitory and excitatory signals to facilitate or inhibit (more of this to come)

Motor Ouput

Planes of Motion

Anatomical Direction

  Anterior (ventral)- front

  Posterior (dorsal)- back

  Superior (cranial)- top

  Inferior (caudal)- bottom

  Medial- towards midline

  Lateral- away from midline

  Proximal- closer to centre

  Distal- away form centre

Biomechanics

  Definition- science of the movement of the living body investigating the forces of the body generated and controlled by muscles, tendons, ligaments, skeletal system, fascia, osmotic affect and other

  Simplification often evaluates forces generated by levers and pulleys

Centre of Gravity- specific centre of mass

Segmental Centre of Mass

Forces and Levers

  A single force acting at a specific location is measured in newtons (N = 1 kg x 1 m/s2)

  Force of gravity (G) always considered- 9.8 m/s2

  Lever- summative effect of force production of biological tissue and external load

Pulley systems

  Biology also employs pulley systems for management of force

Axis of Rotation

  Force is calculated by how it acts around a specific axis of rotation, a point that is the centre to which rotation would occur in all directions in three dimensional space

Moment Arm/Torque

  The rotational force (torque) acting at the axis of rotation driven by the force (N) acting at a distance from the axis of rotation (m)

  Newton meters (Nm)

  Clockwise is positive value, Counterclockwise is negative value

Affect of joint position on Moment Arm

Measuring Biological Load

Mbicep = MFA + Mbook

Importance of moment arm

Importance of moment arm

Importance of moment arm

Importance of moment arm

Force Vector

  Different tissues contribute their varying force at different angles

  Force vectors around the system can be summed to a resultant force vector

Quadricep Force Vector and Patellar tracking

Joint Centration

  Force vectors need to be managed dynamically to stabilize joint in ideal position

  Imbalance results in joint sheer (slide) leading to wear and tear injury