Lecture 11-12 Flashcards
1
Q
definition of motor unit
A
- motor unit = motor neuron + innervated fibers
- each muscle fiber is innervated by only one motor neuron
- a single motor neuron can innervate many muscle fibers
2
Q
individual muscle fibers contract in what type of response
A
“all-or-nothing”
3
Q
describe process of motor unit recruitment
A
- recruitment: progressive activation of additional motor units to increase contractile strength of muscle
- under voluntary conditions- not all motor units are activated at one time
4
Q
isometric contraction
A
- muscle develops tension but does not shorten
- NO movement
5
Q
isotonic contraction
A
- muscle shortens
- tension remains constant
- movement
6
Q
Passive vs active tension
A
- Passive tension: due to stretching muscle
- active tension: force developed due to cross-bridge cycling
7
Q
role of Fascia
A
- fibrous connective tissue that binds muscle into a functional unit
- all connective tissue sheaths are continuous with each other and with tendon
- force is transfered through these connective tissues to tendon and then bone
8
Q
What the length-tension relationship?
A
- tension developed at a particular length is proportional to the number of cross-bridges formed
- only myosin heads within the zone of overlap can bind to actin
9
Q
what is the force-velocity relationship of muscle contraction
A
- force generated by muscle is a function of velocity
- at slower velocities more cross-bridge binding can occur
10
Q
muscle twitch
A
- response to a single threshold stimulus
11
Q
twitch summation
A
- increased frequency of stimulation = successive contractions with increasing force: “piggyback”
- muscle fiber does not have time to fully relax
- high frequency stimulation keeps cytosolic Ca2+ levels high
- a fused maximal contraction (tetanus) can occur
12
Q
when was tissue sampling introduced? When was it re-introduced?
A
- 1868
- 1962
- hollow need inserted into muscle to retrieve a sample
13
Q
Can the fiber type composition of a muscle be changed?
A
- yes, fiber type concentration of a muscle can be changed with training, but, to some extent, is limited by genetics
14
Q
Charactertistics of Type I muscle fiber
A
- High aerobic (oxidative) capacity: MARATHON RUNNER
- lots of mitochondria, myoglobin, and capillary system -> endurance
- slow contractile velocity
- s_mall diameters than type IIa fibers_
15
Q
Characteristics of Type II fibers
A
- high anaerobic (glycolytic) capacity
- rich in enzymes for anaerobic metabolism, high SR content, high ATPase activity
- designed for power and speed but fatigue easily
- fast contractile velocity
18
Q
Name the Neural factors that occur early in training.
A
- increased motor unit recruitment = increased strength
- increased motorneuron output = increased rate of torque development
19
Q
When does muscle hypertrophy occur in training
A
later in training
25
Q
organization of tendon
A
- each unit is held together by connective tissue sheaths
- comprised predominantly of collagen
