Spinal Mechanisms of Gait- Wilson Flashcards
How do we apply eccentric contraction to sitting in chair? What is the prime mover for sitting (what is controlling the action of sitting)? Which muscle controls sitting?
body weight is heavier than the force generated by the muscle= eccentric contraction
weight =mg (physics)
-what is causing the person to sit?
- gravity begins the lowering of the body to sit but
- major extensor of the hip: gluteus maximus (antagonist to gravity) pushes against the gravity to allow you to sit ???
-iliopsoas does flexion at the hip joint but is NOT the one that allows you to sit
What is concentric action?
muscle shortens because load is less than contraction force
-insertion gets closer to the origin
What is isometric action?
muscle length remains the same because load equals contraction force
- muscle contracts but there is no movement
- often occurs around joint where agonist and antagonist muscles contract at the same time
What is eccentric action?
muscle lengthens because the load is greater than contraction force
-muscle is contracting but the amount of force the muscle can generate is less than the load so the muscle is being stretched
Describe the gait cycle.
is from heel strike to heel strike
- starts with heel strike
- foot goes from anterior to posterior position ???
How does the musculoskeletal system work?
contract (shortening of distance of origin and insertion)
What are the 3 contractions skeletal muscle?
- concentric
- isometric
- eccentric
What muscle overcomes gravity to allow you to sit lower?
gluteus maximus: which is the major extensor the hip and undergoes eccentric contraction
it is the antagonist to gravity
What accounts for 60% and 40% of the gait cycle?
stance phase: (limb on the ground) –>60%
swing phase: limb off the ground –> 40%
Within the stance phase what accounts 40% and 10% on opposite ends?
single support: 40% (the opposite leg is in swing phase or the limb is off the ground)
double support: 10% on opposite sides (both limbs are on the ground)
What is the segmental motor and sensory innervation of the lower limb?
both skeletal muscle and dermis is derived from somite which has segmental organization
-each somite is innervated by a particular section of the neural tube that will become the SC
Sensory innervation to skin has a segmental organization called what?
dermatome
The segmental innervation to the muscles of the lower limb is organized how?
proximal-distal gradient
- higher segments of SC innervate proximal structures
- lower segments of SC innervates distal structures
Describe the swing phase of walking.
- flexion of hip
- extension of knee
- extension of ankle
during the swing phase the opposite leg is in the stance phase which ends with “push off “with toes
What parts of the SC control flexing hip, extending knee, and extending ankle?
- flexion of the hip: L2, L3
- extension of the knee: L3, L4
- extension of the ankle: L4, L5
Describe the stance phase of walking.
- extension of hip
- flexion of knee
- flexion of ankle
What parts of the SC control extending hip, flexing knee, and flexing ankle?
- extension of hip: L5, S1
- flexion of knee: L5, S1
- flexion of ankle: S1, S2
Describe gait in general.
- cyclic and repetitive
- largely autonomic
- stereotypic (one step is like the next)
- alternating, reciprocal activity between the limbs
What study did Dr. Wilson use in class to support his hypothesis?
Hypotheisis: The study of gait reveals the fundamental structure, organization and function of the CNS (spinal cord).
Cats can still walk a treadmill following spinal cord transection.
A lesion was placed proximal to the nerves supporting the hind limbs.
Why is the spinal cord called the pattern generator?
The only thing connected to the lower limb is the SC.
- the basic circuits of gait (alternating the limb back and forth making gait possible) are found in the SC
- you don’t need higher upper parts of your brain to say “move”
Describe the reflex that occurs when an individual steps on a the nail.
- flex the thigh and leg of the limb that stepped on nail
- extend the other limb to help you keep balanced
-The flexor withdrawal reflex (cross extensor reflex with the flexor reflex) is a basic circuit underlying alternating movements of the limbs.
When the extensors are active in one limb but the flexors are quiet in the other limb. Vice versa.
SC contains pattern generators for gait.
you don’t need higher upper parts of your brain to say “move”
What are the simplest types of movements?
reflexive responses such as monosynaptic movements
What are the basic movement types?
- reflexive responses: simplest type of movement; limited in what it can do (i.e. patellar reflex)
- rhythmic motor patterns such as walking, running, and chewing: make these movements largely using reflexive responses but you START these movements voluntarily and modify them voluntarily; combine reflexive and voluntary movements
voluntary movements: purposeful and goal directed (i.e. playing the piano)
Describe reflexive movements.
- automatic
- stereotypic
- fast
What is the simplest circuit for modeling how the brain works?
monosynaptic reflex: input output