Locomotion

Question 1

What is locomotion?

Answer 1

Movements of an organism from one place to another, often by the action of appendages such as flagella, limbs or wings.

Question 2

How can a humans locomote at a wide range of velocities such as 45km/h

Answer 2

Appropriate biomechanics and highly adaptive motor patterns

Question 3

Humans are the only mammals to primarily rely on bipedalism to locomote, how did this come about?

Answer 3

We became bipedal to fulfill locomotor needs and to intimidate predators et .

Question 4

What are the three main parts of the motor control loop?

Answer 4

Control

Sensory

Mechanics

Question 5

What is the limb controller and what does it do?

Answer 5

Acts as an individual control mechanism, provides intra-limb coordination and major characteristics of the step cycle

A spinal mechanism that controls stepping

Question 6

Where is the limb controller located?

Answer 6

Located in spinal cord and generates a number of rhythmical movements

Question 7

How do controlled stepping movements occur??

Answer 7

Occur due to coordination between the controllers due to mutual influences.

Question 8

What is the locomotor automatism?

Answer 8

The motor centres located in the spinal cord, brainstem and cerebellum constitute a control system (LA) which is capable of governing locomotion in simple environmental conditions

Question 9

Van Holst (1938) believed each limb is driven by its individual control mechanism, what evidence is there for this?

Answer 9

Forssberg et al (1980) stated that under conditions, the rhythms of stepping may differ across limbs (e.g., when climbing obstacles)

Question 10

Can rhythmic activity be generated in the absence of sensory feedback?

Answer 10

Yes, rhythmic activity with an efferent motor pattern similar to stepping for each of the hind limbs (cat), with bilateral alternation can be generated in spinal cord in absence of sensory feedback.

Question 11

Where are human limb controllers located?

Answer 11

Basic nervous mechanisms constituting the limb controller are located in the lumbsacral spinal cord

Question 12

What did Vilensky (1992) state about paraplegic patients?

Answer 12

That these patients with a complete/almost rupture of the spinal cord are unable to generate spontaneous/sensory stimulated stepping behaviours.

Question 13

What does the limb controller consist of?

Answer 13

Primarily a structure known as the central pattern generator (CPG)

Located in spinal cord enlargements

Question 14

What are the two main parts of the step cycle?

Answer 14

Stance phase (support) - starts when the limb reaches the anterior extreme position (AEP) - 62%

Swing phase (transfer) - starts when the limb reaches the posterior extreme position (PEP) - 32%

Question 15

What are the two ways of increasing speed?

Answer 15

Increasing the stepping frequency

Increase the stride length

Question 16

In cats, which muscles consist with the phases?

Answer 16

Stance phase mainly extensors

Swing phase mainly flexors

Question 17

Obviously the step cycle is much shorter at higher speeds, why is this?

Answer 17

Mainly due to shortening of the stance phase

Question 18

What did Nilsson and thorstensson find when looking at the step cycle in humans?

Answer 18

They found that step cycle and step length both reduce with speed meaning an increase in frequency. Also found that hip and knee angles increase with speed which means an increase in stride length

Question 19

What is gait?

Answer 19

A definitive phase pattern

Question 20

What are the two basic types of coordination observed at the hip and shoulder girdle?

Answer 20

1) strict alternation - limbs are out of phase
2) in-phase coordination - limbs work together

1 tends to occur at slower speeds and type 2 occurs at higher speeds

Question 21

What affects inter-limb coordination??

Answer 21

Postural stability needs to be maintained

At low speeds - static stability (centre of mass is maintained within a base of support)

At high speeds - dynamic stability (at any point in time stability might not be maintained)

Question 22

How is movement initiated (how is spinal network activated)??

Answer 22

Activation of spinal network primarily caused by an excitatory drive by a population of neurons from the reticulospinal tract

Question 23

The locomotor system can be activated via two inputs, what are they??

Answer 23

Mesenphalic and subthalamic locomotor regions

Also can be stimulated without RS involvement.

Question 24

Broadly, what are the 4 key roles of the cerebellum?

Answer 24

Mediation of sensory feedback

Mediation of internal feedback

Optimisation of the motor pattern

Organisation of interactions between the spinal limb controller and supraspinal motor centre

Question 25

What is the role of the motor cortex??

Answer 25

Does not play a role in simple locomotion

But, it very important in visually controlled gait modifications and other forms of gait coordination

Question 26

What can spinal rhythm generators cause in corticospinal and cortical neurons??

Answer 26

Can cause rhythmical bursting