Final Flashcards
Definition of locomotion
Controlled act of moving the body as a whole from one place to another
What are the 3 components of control in locomotion?
- control of limb and body movements
- control of where you are going
- control of posture & orientation
Stance phase definition
Part of locomotor cycle (one leg) during which some part of the foot is on the ground
Begins at heel strike
Swing phase definition
Part of locomotion (one leg) where no part of the foot is in contact with the ground
Stride definition
One movement cycle of a single leg; consists of a stance and swing phase
Walk (bipedal) definition
Legged locomotion in which the legs move in antiphase
Run (bipedal) definition
Both feet never on the ground at the same time, but some flight periods; move in antiphase
Central pattern generator (CPGs)
Grouping of neurons (or circuits) within the spinal cord or brainstem that can generate coordinated rhythmic muscle activity
- leads to rhythmic oscillatory behaviour (locomotion, flying, swimming) without afferent feedback
Who first demonstrated rhythmicity (CPGs) and what reflex was it called?
Sherrington; scratch reflex
Scratch reflex
Rhythmic movements of limb used to remove annoying stimulus
How did spinalised animals respond (in terms of reflex latency) when stimulation intensity increases?
As stimulation intensity increases, reflex latency decreases
What occurs to muscle contraction when stimulation increases in the scratch reflex?
As stimulation intensity increases, the strength of muscle contraction increases
What occurs to the duration of response when stimulation intensity increases?
As stimulation intensity increases, duration of response increases and outlasts the stimulus
What is the rhythmic movement of extension and flexion independent of?
Supraspinal or peripheral feedback
Who demonstrated rhythmic stepping in spinal animals after dorsal spinal root transection?
Brown (1914)
What are half-centres?
A type of spinal circuitry organization that explains rhythmic stepping
- mutual inhibition
What is each limb controlled by?
An independent half-centre
What did Grillner confirm?
Confirmed Brown’s hypothesis about half-centres
What was the primary conclusion of Grillner’s work with spinalised cats?
Circuitry for locomotion is intrinsic to the spinal cord
What occurs when the inhibitory synapse is blocked in half-centres?
Rhythmic motion is still evoked
What are 3 motor regions that can be artificially stimulated to produce locomotor activity?
- subthalamic locomotor region
- mesencephalic locomotor region
- diencephalic locomotor region
Locomotor region definition
Region of the brain containing neurons that produce descending signals that activate spinal locomotor CPG circuits causing locomotion
What did Shik, Severin, and Orlovsky show about descending stimulation from the mesencephalic locomotor region?
Locomotion was dependent on the stimulus intensity of the MLR
What are the 5 jobs of the brain in locomotor control?
- initiating and terminating CPG activity
- controlling the speed of locomotion and gait
- adapting locomotion to the task
- coordinating locomotor activity with concurrent activities
- maintaining postural equilibrium during locomotion
What is a SCI?
Spinal cord injury; no sensory or motor function below the level of the lesion
AIS A vs AIS B
Sensory complete spinal cord injury; sensory incomplete spinal cord injury
What does epidural stimulation of spinal circuitry result in for completely paralyzed individuals?
Process sensory input to regain some voluntary control of paralyzed muscles
What is the stepping reflex? What does it provide evidence for?
An infant makes stepping motions when their feet touch the ground
Human evidence for CPGs and locomotion, present even in anacephalic infants with no descending control
What is the difference in evidence for CPGs and locomotion in animals vs humans?
Strong evidence for locomotion after SCI in animals, not as strong in humans
What are the 4 functions of the vestibular system?
- balance and equilibrium
- detect head motion
- determine gravitational vertical
- fixation of eyes while head moves
What are the 5 sensory organs of the vestibular system? How are they divided?
Three semicircular canals
- anterior
- posterior
- horizontal
Two otolith organs
- utricle
- saccule
What cranial nerve innervates the hair cells?
CN VIII: auditory
Where are the cell bodies of the vestibular system found?
Scarpa’s ganglion
Once information of the alignment of stereocilia is conveyed to the brainstem and cerebellum where does the info go? 2
- MNs to extraocular muscles
- MNs of antigravity muscles
On which side is the kinocilia in the hair cells of the right and left side?
Right, the kinocilia is on the right
Left, the kinocilia is on the left
When the kinocilia is deflected away from the midline what occurs?
Depolarization
When the kinocilia is deflected towards the midline what occurs?
Hyperpolarization
What does head tilt provide information on?
Acceleration (linear and angular changes in position)
What structure does the crista contain?
Hair cells
Where do the hair cells extend into?
Cupula; gelatinous mass
What do the semicircular canals detect?
Head rotation
What is the relationship of the direction of head turn and the direction of endolymph flow?
Endolymph flows opposite to the direction of the head
If one side of hair cells depolarize in relation to head movement, what occurs to the opposite side of hair cells?
If one side depolarize, the other side hyperpolarizes
Does the brain interpret direction of head turn from the hyperpolarized, or depolarized side of the hair cells?
Interprets direction from the depolarized side
Which plane does the utricle and saccule lie in?
Utricle: horizontal plane
Saccule: vertical plane
What 2 things are otolith organs specialized for?
- detecting linear acceleration of the head
- indicating static position of head relative to gravity
What does the otolithic membrane contain? Where in the membrane are they found?
Otoconia (calcium crystals) that overlay the hair cells
What is the function of the otoconia?
Increases the mass of the otolithic membrane, increased impact of gravity
What are otoliths?
The 2 organs of saccule and utricle
What are the type of afferent neurons that are primary from vestibular canals to the vestibular nuclei?
Bipolar neurons
What are the 4 nuclei that make-up the vestibular nuclei?
- lateral nucleus
- medial nucleus
- superior nucleus
- inferior nucleus
What 4 structures are the secondary connections formed with from the vestibular nuclei?
- spinal cord
- cerebral cortex
- cerebellum
- oculomotor nuclei
What is the LVST?
Lateral vestibulospinal tract
What is the primary function of the LVST and where does it’s axons synapse to achieve this?
- regulation of upright stance
- synapse on ipsilateral antigravity (extensor) muscles
What occurs when there is transection above the LVST?
- decerebrate rigidity; unopposed excitation of LVST
Aka there are no inhibitory inputs to regulate
What does the medial vestibulospinal tract (MVST) control? What is the name of the reflex?
- reflexive control of head movements to maintain stability
- vestibulo-colic reflex
Where does the vestibulo-ocular pathway project to? 3
- oculomotor nuclei CN III
- trochlear nuclei CN IV
- abducens nuclei CN VI
Which reflex allows the eyes and head to move in opposing directions?
Vestibulo-ocular reflex (VOR
Which 2 ocular muscles allow for the eyes to move in horizontally opposing directions to the head? Which reflex is this involved in?
Medial rectus muscle
Lateral rectus muscle
VOR reflex
What is the relationship between ipsilateral medial & lateral recti muscles for horizontal eye deviation?
What is the relationship between contralateral recti muscles?
Ipsilateral: medial and lateral recti muscles act as AG/ANT pair
Contralateral: medial and lateral recti muscles move synergistically
Do the eyes move in the direction that is consistent with the hyperpolarized or depolarized side?
Eyes turn towards the hyperpolarized side
What is nystagmus and what is its purpose?
Rapid eye movement; keeps images stable on the retina
When does nystagmus occur?
When VOR is not enough to maintain image on retina (too large of head rotations)
What are the 2 phases of visually induced (normal) nystagmus?
Pursuit: slow phase in one direction
Saccade: fast phase in opposite direction
What are the movement directions with a rightward nystagmus?
Slow movement of the eyes to the left (pursuit) and fast recovery to the right (saccade)
What is an example of nystagmus in daily life?
Tracking telephone poles with your eyes and they have to reset quickly
What are the 3 types of nystagmus?
- optokinetic nystagmus: tracking stimuli
- rotary nystagmus: head rotation
- caloric nystagmus: vestibular stimulation
What test is used to measure nystagmus?
Electronnystagmography (ENG)
- records eye movement in response to visually or vestibular-induced nystagmus
What does the irrigation of the inner ear do?
It mimics the movement of endolymph and can cause hyper or depolarization depending on the temperature of the water
What is the effect (hyperpolarization/depolarization) when irrigated with cold vs warm water?
Cold: that side is hyperpolarized
Warm: that side is depolarized
- eyes will turn to the hyperpolarized side
Postural control definition
Controlling the body’s position in space
Postural stability definition
Stabilizing the body’s CoG in relation to its BoS during movement
Centre of Gravity (CoG) definition
A single location of a physical object where gravity acts on the object
Base of support (BoS) definition
The area of support surface where the object and surface make contact
- drawn with straight lines
What is the ability to maintain balance dependent on?
The size of the base of support
Limit of stability definition
Maximum angle (vertically) that can be tolerated before balance is lost
Postural orientation definition
Maintain relationship b/w body segments & b/w body and environment when doing tasks
What 3 systems contribute to postural orientation?
- vision
- proprioception
- vestibular system
Postural muscle tone definition
Slight activation of many muscles of the neck, back, abdomen, and legs while standing
What is the purpose of postural muscle tone? 2
- opposes gravitational torque
- keeps legs, trunk, and head in alignment
What are the 2 requirements to maintain an upright posture?
- keeping the CoG above the BoS
- maintaining alignment of body segments
Quiet stance definition
Standing still with no disturbances and performing no tasks
Environmentally perturbed stance
Standing person is subject to externally disturbances
Action perturbed stance
Standing person performs actions that involve movements
What are 8 muscles that are involved in quiet stance?
Anterior (3) to posterior (5)
- abdominals
- quadriceps
- TA
- traps
- erector spinae
- glute med
- hams
- triceps surae
What is a stabilogram?
Graphical representation of movement of an individuals CoG
What are reactive postural adjustments?
Movement strategy that maintains CoG within BoS in response to an external disturbance
What are the 2 types of movement strategies in relation to reactive postural adjustments?
Feet-in-place strategy
Stepping strategy
What are the 2 strategies within the feet-in-place recovery strategy?
Ankle and hip strategy
What is the order of muscle activation in the ankle strategy?
Distal to proximal muscle activation
- gastroc then hams then erector spinae
Which sets of muscles (anterior/posterior) activate during a forward sway during feet-in-place recovery?
Forward sway, posterior muscles activate
Backward sway, anterior muscles activate
What is a postural set?
Multiple muscle groups that are connected and can be suppressed or activated in response to perturbation
What is the difference in order of muscle activation for the hip strategy compared to the ankle strategy?
Hip strategy activates muscles proximal to distal whereas ankle is the opposite
