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Physiology 215 Chapter 8
Terms in this set (81)
What are the three muscle types?
Skeletal, cardiac, smooth
What types of muscle are striated?
Skeletal and cardiac
What types of muscle are unstriated?
What types of muscle are voluntary?
What types of muscle are involuntary?
Cardiac and Smooth
What is a single skeletal muscle cell called?
What are the characteristics of skeletal muscle?
2. Large, elongated, and cylindrically shaped
3. Fibers extend entire length of muscle
What are muscle fibers composed of?
What is a component of thick filament?
What is a component of thin filament?
What is the functional unit of skeletal muscle?
What defines the boundary of the sarcomere and attaches thin filaments?
What is made up of thick filaments along with portions of thin filaments that overlap?
What is the lighter area within the middle of A band where thin filaments do not reach?
What extends vertically down the middle of A band within center of H zone?
What consists of remaining portion of thin filaments that do not project into A band?
Protein consists of two identical subunits:
- tail ends are intertwined
- globular heads project out at one end
- heads form cross-bridges between thick and thin filaments
In myosin what are the two important binding sites in a cross-bridge?
Actin-binding site and myosin ATPase site
-Interacts with the myosin cross-bridges
-In relaxed muscle, they prevent cross-bridge interaction.
What are the two proteins that lay across the surface of actin?
Tropomyosin and troponin
- Lies alongside groove of actin spiral
- Covers actin sites blocking cross-bridge binding
- Made of 3 polypeptide units:
- One binds to tropomyosin
- One binds to actin
- One binds to calcium
Calcium is released into the cytosol to produce contraction by...
What is regulated by calcium release?
Sliding filament mechanism
In the sliding filament mechanism calcium binds to _______, so ________ moves out of its blocking position.
What leads to cross-bridge power stroke?
Binding of actin to a myosin cross bridge
What refers to the events linking muscle excitation to muscle contraction?
What is the link between excitation and contraction?
What promotes release of Calcium into cytosol?
- Run perpendicularly from surface of muscle cell membrane to central portions of muscle fiber.
- Spread of action potential down a T tubule triggers release of Calcium from sarcoplasmic reticulum into cytosol
- Modified endoplasmic reticulum
- Consists of fine network of interconnected compartments that surround each myofibril
-Stores and release calcium to promote muscle contraction
-Binds to myosin head and detaches it from actin
- Hydrolysis transfers energy to myosin head and reorients it.
- Reenergized head now capable of another power stroke
- Depends on calcium reuptake into sarcoplasmic reticulum
- Acetylcholinesterase breaks down ACh at neuromuscular junction
Connective tissue extends beyond ends of muscle to form what?
What is the series-elastic component?
Noncontractile elastic tissue of muscle is in series with the contractile component.
What are the three primary types of muscle contraction?
Isotonic, Isokinetic, and isometric
The load remains constant as the muscle changes length.
Velocity remains constant as the muscle changes length
The muscle length remains constant as tension increases
A rigid structure capable of moving around a pivot point known as a fulcrum
What acts as levers?
What acts as fulcrums?
The varying strength contractions of a whole are called?
What are the two primary factors that can be adjusted to produce graded contractions?
Number of muscle fibers contracting, tension developed by each contracting fiber
One motor neuron that muscle fibers innervate
Increasing the number of motor units contracting is called?
Motor unit recruitment
What takes place to delay or prevent fatigue?
What are the 4 factors that influence whole muscle tension?
1. Frequency of stimulation
2. Length of the fiber at the onset of contraction
3. Extent of fatigue
4. Thickness of the fiber
What is the increase in tension accompanying repetitive stimulation of a muscle fiber?
What is muscle tetanus?
A smooth, sustained contraction of maximal strength.
When does muscle tetanus occur?
Occurs if muscle fiber is stimulated so rapidly that it does not have a chance to relax between stimuli.
Where is optimal muscle length?
Where maximal tension is developed
What limits muscle shortening and lengthening?
Attachment of muscle to bones
What do the four steps in the excitation, contraction, and relaxation processes require?
Muscle fibers have what pathways for forming new ATP?
Creatine phosphate to ADP
-The energy released from the hydrolysis of ________ can be donated directly to ADP to form ATP
-_________ is the first source for supplying additional ATP when exercise begins
-_________ can supply ATP for up to the first minute of exercise
-Slow process of making ATP
-Produces large amounts of ATP
-Supports aerobic or endurance-type exercise
-Occurs when oxygen delivery or oxidative phosphorylation can't keep pace with ATP demand.
-Can produce ATP quickly and under anaerobic conditions
What occurs when an exercising muscle can no longer respond to stimulation with the same degree of contractile activity?
What occurs when the CNS no longer adequately activates motor neurons?
What is the need for elevated oxygen uptake during exercise recovery?
Excess post-exercise oxygen consumption
What are the three types of skeletal muscle fibers?
-Slow-oxidative (type I) fibers
-Fast-oxidative (type IIa) fibers
-Fast-glycolytic (Type IIx) fibers
Do fast or slow fibers have higher myosin ATPase?
Motor movement depends on what three types of inputs?
1. Afferent neurons
2. Primary motor cortex
3. Brain stem
What are the two types of muscle receptors?
Muscle spindles and Golgi tendon organs
What monitors muscle length?
What detects changes in tension?
Golgi tendon organs
Spindles consist of collections of specialized muscle fibers known as?
What lie within spindle-shaped connective tissue capsules parallel to?
What contains both afferent and efferent nerve fibers and plays a key role in stretch reflex?
-In muscle tendons
-Respond to changes in muscle's tension
-Reaches the level for conscious awareness
Golgi tendon organ
-Contains actin and myosin but not troponin, and tropomyosin
-Does not form myofibrils and not arranged into sarcomeres
-When stretched, develops tension and yet can inherently relax
-Slow and economical (latch phenomenon)
Cross bridge stays attached for more time (8x longer than skeletal muscle); latches onto
What is mediated by calcium binding with calmodulin?
Smooth muscle cross-bridges
- Phasic or tonic
- Multiunit or single-unit
- Neurogenic or myogenic
Smooth muscle types
Contracts in bursts
Triggered by action potentials that lead to increased cytosolic calcium
Phasic smooth muscle
Usually partially contracted at all times
Tonic smooth muscle
-Found in walls of large blood vessels
Multiunit smooth muscle
-Found in walls of hollow organs
-Myogenic, can initiate its own contraction
-Pacemaker and slow-wave potentials
Single unit smooth muscle
Fibers of interconnected muscle cells that function electrically and mechanically are known as?
What causes your foot to "fall asleep"?
Parathesia, compression of certain nerves.
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