Locomotion on legs

Question 1

Locomotion

Answer 1

the controlled act of moving the body as a whole from one place to another

Question 2

when locomotion is self-propelled, three components of control can be distinguished

Answer 2

1. control of the limb and body movements that generate propulsive forces
2. control of where you are going
3. control of posture and orientation

Question 3

stance phase

Answer 3

the part of the locomotor movement cycle of one leg during which some parts of the foot is in contact with the ground, starts when the foot first contacts the ground, and ends with the moment it breaks contact - 60%

Question 4

swing phase

Answer 4

the part of the locomotor movement cycle of one leg during which no part of the foot is in contact with the ground. Starts when the foot breaks contact with the ground, and ends the moment it makes contact

Question 5

stride

Answer 5

one movement cycle of a single leg, consisting of a stance phase and a swing phase - two events of the same limb

Question 6

walking and running are both examples of

Answer 6

diff gaits

Question 7

walking

Answer 7

=bipedal: mode of legged locomotion in which the legs move in antiphase, one foot or the other is in contact with the ground at all times, and both feet are on the ground at the same time for a short period (double limb support) - 20%

Question 8

run

Answer 8

=bipedal - a gait in which both legs move in an antiphase, both feet are never on the ground at the same time, but there are periods during which both feet are off the ground (flight phase)

Question 9

during locomotion, muscles are activated …

Answer 9

in a rhythmic, cyclical pattern

Question 10

what are the hip and leg muscles doing during locomotion? -6

Answer 10

1. providing the force needed for forward progression
2. supporting the weight of the body during stance
3. moving the leg from one position on the ground to the next during the swing phase
4. keeping the foot clear of the ground during the swing phase
5. absorbing the force of impact at footfall
6. maintaining the upright posture throughout the movement cycle

Question 11

intralimb coordination

Answer 11

diff joints of a single leg

Question 12

interlimb coordination

Answer 12

movements of diff legs

Question 13

central pattern generator

Answer 13

a grouping of neurons or neural circuits within the spinal cord or brainstem that, when activated, can generate, coordinated, rhythmic muslce activity, leading to rhythmic oscillatory behaviours such as locomotion, flying, swimming without afferet fdbk.

Question 14

scratch reflex

Answer 14

first demo of rhythmicity: sherrington cervical transection
- rhythmic movements of limbs used to remove annoying stimulus, rhythmic movement of limbs occurs independent of a rhyming input stim - your dog sratches in a diff rhythm then your scratch on them

Question 15

as stim intensity increases - 3

Answer 15

reflex latency decreases, strength of muscle contraction increases. duration of response increases (outlasts stim because of reverberating circuit - allows the first neuron to keep sending neurons)

Question 16

rhythmic afferent input from moving limb may drive

Answer 16

rhythmicity of motor output

Question 17

to remove afferent fdbk

Answer 17

cut dorsal spinal roots

Question 18

circuits responsible for thythmic alteration of flexion and extension are

Answer 18

intrinsic to spinal cord and surpass inputs of peripheral fdbk and independent of dorsal spinal root transaction

Question 19

Brown, 1914 demoed rhythmic stepping in spinal animals after

Answer 19

half center - half centre model of spinal circuitry organization

Question 20

Headless chicken CPG

Answer 20

enables basic homeostatic functions to be carried out in absence of higher brain structures - brainstem needed to initiate pattern.

Question 21

CPGs for locomotion from Sten Grillner (1976) - what did they do? - 4

Answer 21

thoracic transaction to isolate hind limbs
confirmed brown’s work
demoed that spinal circuits act as CPGs from stepping
each limb controlled by independent half centre
limbs show alternating stepping with rhythmic and physic bursts of muscle activity appropriate to locomotion

Question 22

criticism of Grillners’ cats

Answer 22

locomotion in Grillnercats is passive - initiated and maintained by treadmill motion - so is it due to spinal circuitry or reflexive response to the stretched muscle?

Question 23

solution to criticism of Grillners’ cats

Answer 23

walking slow and less coordincated - appropriate locomotor movements observed - alternation of flexor/extensor muscles

Question 24

How doesnt the original half centre model fit with recent results - 3

Answer 24

inhib synaptic transmission blocked by chemical agents
rhymic activation of flexor and extensor MN still evoked
two rhythm generators coupled in mutually inhib fashion

Question 25

how can descending activity be produced artificially in an experimental animal - 1-3

Answer 25

electrically or chemically stimulating a number of diff brain locations - subthalamic locomotor region - midbrain, mesencephalic locomotor region - midbrain (human) diencephalic locomotor region - thalamus/hypothalamus

Question 26

locomotor region

Answer 26

circumscribed region of the brain containing neurons that when stimulated sufficiently strongly produce descending signals that activate the spinal locomotor CPG circuits and cause them to generate locomotor patterns

Question 27

shik, severin, orlovsky 1966 - initiation of of locomotion through electrical stim of \_\_\_ in decerebrate cats
locomotor rhythm (walk/trot/gallop) dependent on

Answer 27

mesencephalic locomotor region

stim intensity - high stim - hind limbs begin to move together

Question 28

brains roles in locomotor control - 5

Answer 28

initiating and terminating CPG activity -
controlling the level of CPG activation and hence the speed of locomotion and gait - increased speed from increased intensity
adapting the level of CPG activation and hence the speed of locomotion and gait
coordination locomotor activity with concurrent excecuted activities - multitasking
maintaining postural equilibrium during locomotion

Question 29

Evidence that spinal CPG is likely the basis for locomotor pattern generation in people in cliniclaly complete spinal cord injury/transection:

Answer 29

no sensory/motor function detectable below the level of the lesion and no sensory cortical evoked potentials (measured from scalp electrodes) recorded in response to response to stim of the lower leg but epidural stims - something is still present

Question 30

Evidence that spinal CPG is likely the basis for locomotor pattern generation in people - young infants

Answer 30

stepping reflex - if an infant is held upright with their feet touching the ground, the legs may make repeated stepping movements as if the infant is trying to walk - closely resemble the stepping patterns of the hind legs of spinal cats and other mammals - resonable to conclude that reflex stepping is generated by a similar mechanism - they dont have cortical control - that myelination does not complete until 2yrs old

Question 31

A spinal CPG is likely the basis for locomotor pattern generation in people - 3

Answer 31

evident that some locomotor movements can be produced in humans following SCI
but considerably less effective than those demoed in animals
current hypothsis is that the inherent requirements for bipedal stance (i.e. postural control) are greater than those that can be accommodated by spinal cord circuitry

Question 32

Grass - could change locomotor activity after treadmill training in subjects with incomplete spinal cord injury - 3

Answer 32

induced stepping movements - increases in amount and decrease in duration of EMG activity of specific muscles associated with functional recovery of walking skills following injury - some positivity,