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Summary BBS2052 Neuromuscular Control of Movement
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Summary BBS2052:Neuromuscular Control of
Movement
Case 01: The Rhythm of Walking + Lecture 03: How the Brain Makes Us Move + Lecture 04:
Neuromechanics and Energetics of Walking and Running
The gait cycle
Stance phase
1. Initial contact
- Heel strike at 25-degree angle in neutral position dorsiflexion tibialis anterior
- Knee 0-5 degree extended quadriceps
- Hip flexion of 30 degrees
2. Loading response
- Acceptance of body weight in a manner that ensures limb stability and permits
progression
- Ankle drops in 10 degrees of plantar flexion, pretibial muscles make forefoot contact
gradual
- Knee flexion of 15 degrees increased quadriceps activity and no hamstring
activity
- Hip flexion gluteus maximus and adductor magnus
3. Midstance
- Advancement of the body and limb over a stationary
foot
- Ankle gradually dorsiflexes: -5 to +5 soleus and
gastrocnemius
, - Knee flexion of 18 degrees quadriceps activity declines
- Decline in hip flexion passive; hip abductor muscles
4. Terminal stance
- Forward fall to generate a propulsive force
- Ankle 10 degrees of dorsiflexion becomes 5 degrees of plantar flexion soleus and
gastrocnemius
- Maximum extension between 0 and -5 degrees passive
- Hip: passive extension end of stance: 10 degrees of hyperextension
5. Pre-swing
- Preparation of the limb for swing
- Rapid passive flexion to 40 degrees quadriceps may restrain flexion
- Hip flexion: recovery from hyperextension to neutral iliacus
- Ankle plantar flexion: 20 degrees passive
Swing phase
6. Initial swing
- Recovering from a trailing posture
- Ankle dorsiflexes to 10 degrees of plantar flexion tibialis anterior
- 60 degrees of knee flexion sartorius, biceps femoris, and graciliis
- Hip flexes to 20 degrees iliacus, sartorius, gracilis, adductor longus
7. Mid-swing
- Ankle dorsiflexion to neutral is accomplished and maintained tibialis
anterior
- Knee extends passively because flexor muscles relax
- Maximum flexion to 30 degrees is reached iliacus
8. Terminal swing
- Ankle might go into slight plantar flexion (3-5 degrees) slight tibialis anterior action
- Knee from extension to neutral (0 or -5 degrees) quadriceps provide extensor force,
hamstrings decelerate hip flexion and prevent knee hyperextension
- Hip flexion of 30 degrees hamstrings prevent further motion
Gait cycle running
Control of the gait cycle
1. Control of the limb and body movements that generate propulsive forces
2. Control of where you are going: direction, speed, altitude and landing, and route finding
3. Control of posture and orientation
Three specific locomotor regions regulate gate
1. Mesencephalic locomotor region (MLR)
, o Input from premotor cortex, limbic system, cerebellum, hypothalamus and parts
of the brainstem
o Neurons connect to neurons in mesencephalic reticular formation descends
via the ventrolateral funiculus to spinal locomotor networks
2. Subthalamic locomotor region (SLR)
o Part of the hypothalamus
o Activates the spinal locomotor networks directly and via the MLR
3. Cerebellar locomotion region (CLR)
o Activates reticulospinal locomotor pathway directly and indirectly
Cerebral cortex is required for skilled motor skills information is transmitted to the SMA
and premotor area
Cerebellum
o Responds to abnormalities in posture in order to coordinate proper movement
o Receives sensory information and compares it to the intended pattern
o Sends signals to cerebral cortex and brain stem
o Efferent signals go to spinal cord and regulate balance, limb movement and head
position and movement
Spinal cord
o Generates the rhythm of locomotion and ensures postural stability
o Stretch reflex and non-recipocal inhibition
o Transmitted via spinothlamic, spinoreticular and spinocerebellar tracts
Ascending pathways
Receive signals, process signals, plan reactions/movements
Posterior column pathway
o Joint position, vibration, fine discriminative touch
o End in primary somatosensory cortex
Anterolateral pathway (spinothalamic)
o Pain, temperature, crude discriminative touch
o End in primary somatosensory cortex
Descending pathways
Activating movement
Corticospinal tract
o Efferent innervation of skeletal muscles
o Lateral corticospinal tract limbs (crosses over)
o Anterior corticospinal tract balance, trunk muscles (does not cross over)
o Stroke gives most often problems with the limbs and not with balance
Central pattern generator (CPG)
Two requirements
1. Two or more processes that interact such that each process sequentially increases and
decreases
2. As a result of this interaction, the system repeatedly returns to its starting condition
There are four basic muscle synergies, which indicates that walking is regulated by central
pattern generators
How to measure forces and movement – EMG, kinematics, kinetics
EMG
Electrodiagnostic medicine technique for evaluating and recording the electrical activity
produced by skeletal muscles
Performed using an electromyograph to produce an electromyogram
, Electromyograph detects the electric potential generated by muscle cells when these are
electrically or neurologically activated
Limitations:
o Electrode placement can be difficult depends on muscle size
o Proper needle placement is needed for an accurate representation of the muscle of
interest more effective on superficial muscles as it is unable to bypass the action
potentials of superficial muscles and detect deeper muscles
o The more body fat an individual has, the weaker the EMG signal
Kinematics
Describes the motion of points, bodies, and systems of the bodies without considering the
forces that cause them to move
Problem begins by describing the geometry of the system and declaring the initial conditions
of any known values of position, velocity, and/or acceleration of points within the system
How forces act on the body falls within kinetics
Motion analysis
Measuring kinematics with markers and infrared cameras
Kinetics
Branch of classical mechanics that is concerned with the relationship between motion and its
causes, specifically, forces and torques
Case 02: To Stand Despite All Options to Fall + Lecture 05: Static and Dynamic Balance + Lecture 07:
The Vestibular System
Vestibular system
Structure
Three interconnected bony tube-like structures: horizontal (lateral), superior (anterior) and
posterior semi-circular canals
Anterior (superior) semi-circular canal
o Movement in the sagittal plane: splits the body into left and right
o Movement around the y-axis from year to ear (perpendicular to sagittal plane)
Posterior semi-circular canal
o Coronal plane: splits the body in front and back
o Movement around the x-axis nose to back of the head
Lateral (horizontal) semi-circular canal
o Movements in a transverse (horizontal) plane: splits the body in top and bottom
o Movement around z-axis from top to bottom
Vestibule
o Lies anterior to the semi-circular canals, posterior to the cochlea and medial to the
tympanic cavity
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