Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
29 Cards in this Set
- Front
- Back
|
What are the dark striations in regions containing the thick filaments?
|
-A Band
|
|
|
Light striations represent what regions?
|
-I Band attached to Z line
|
|
|
Thick filaments= _______
|
-Myosin
|
|
|
What does each myosin molecule contain?
|
-Two rod-like alpha helical supercoiled heavy chains
-One end of the heavy chains has a globular tertiary structure and is associated with a set of 2 light chains |
|
|
What do the globular myosin head contain?
|
-Actin and ATP binding sites
|
|
|
The crossbridges are flexible at two points, called _____, which allow for the movement during the contraction process.
|
-Hinges
|
|
|
3 Components of Thin Filaments
|
1. Actin
2. Tropomyosin 3. Troponin |
|
|
What is the backbone of the thin filament composed of?
|
-G-Actin subunits
|
|
|
Troponin: Complex Components
|
-Tn-C: strong affinity for calcium
-Tn-I: strong affinity for actin -Tn-T: strong affinity for tropomyosin |
|
|
The crossbridge cycle acts to couple_____ ____ to muscle contraction.
|
-ATP cleavage (chemical energy)
|
|
|
What happens upon muscle stimulation r?
|
-Intracellular calcium increases up to 100-fold
-Calcium bins to Tn-C |
|
|
Binding calcium to Tn-C
|
-Causes a conformation change in the troponin-tropomyosin complex that exposes the myosin binding sites on the actin filaments
-Enables M-ADP-Pi to bind to actin |
|
|
Central Principle of Muscle Mechanism
|
-The force generated by a muscle is directly proportional to the number of crossbridges actin in parallel
|
|
|
What is the force of the muscle dependent on? (4)
|
1. Recruitment of motor units
2. Muscle Length 3. Number of myofibrils 4. Temporal summation |
|
|
Why does the degree of active force generated by a muscle depend on muscle length?
|
-Muscle length affects sarcomere length (distance between Z disks), and the degree of overlap between thick and thin filaments
|
|
|
Each mammalian skeletal muscle cell is innervated by a single __ _______.
|
-Alpha-motoneuron
|
|
|
Motor Unit (def)
|
-a single alpha-motoneuron
-Axon -all of the muscle fibers that it innervates |
|
|
Recruitment (def)
|
-the process whereby increasing numbers of motor units are activated as a function of the level (frequency) of excitatory input from the CNS
|
|
|
Size Principle (def)
|
-partly determines a hierarchy for the recruitment of motor units
-states that the cell bodies of associated motoneuroons increase in size as the numbers of muscle fibers innervated by the motor unit increases |
|
|
Since increased cell body size correlates with a decreased level of neuronal excitability, recruitment of large motor units require....
|
-summation of multiple excitatory synaptic inputs
|
|
|
Size principle allows for ___ and ______ movements.
|
-Fine
-Gross |
|
|
Muscle Hypertrophy (def)
|
-increase in muscle mass
-increases number of myofibrils and crossbridges -increases muscle strength |
|
|
Muscle Atrophy (def)
|
-decay of myofibrils is faster than rate of replacement-->become replaced by fibrous fatty tissue
|
|
|
Contracture (def)
|
-takes place during denervation atrophy
-fibrous tissue has tendency to continually shorten |
|
|
How can the level of tension of a muscle be increased above the single twitch level?
|
-By delivering additional stimuli prior to the termination of the first stimulus
|
|
|
Temporal Summation (def)
|
-a 2nd contraction is partially added to the 1st, such that the total strength of contraction rises with an increases in stimulation frequency
-the contraction fuse together resulting in a smooth continuous tetanus |
|
|
2 Reasons Why Temporal Summation Occurs
|
1. Temporal Summation reduces the elastic work required to stretch the series elastic elements-->insufficient time for elastic recoil
2. A single twitch produces a submaximal level |
|
|
Series Elastic Elements
|
-the structural elements of muscle (connective tissue, tendons, and crossbridges) that must be stretched before the force of shortening is transferred
|
|
|
Does summation occur in cardiac muscle? Why or why not?
|
-No, summation does not occur in cardiac muscle because very long cardiac action potentials nearly overlap the tension transient
|
