Chapter 12 Muscle Physiology Flashcards
What are the three types of muscle Tissue?
- Skeletal
- Cardiac
- Smooth
What is the purpose, function and structure of each of the three types of muscle tissue?
- Skeletal:
- Skeletal muscle is attached to bones by tendons
- Contraction causes movement of skeleton
- Striated, many peripheral nuclei, voluntary - Cardiac:
- Skeletal muscle is attached to bones by tendons
- Contraction causes movement of skeleton Striated, many peripheral nuclei, voluntary - Smooth: Skeletal muscle is attached to bones by tendons
- Contraction causes movement of skeleton
- Striated, many peripheral nuclei, voluntary
How do skeletal muscles work?
- When a muscle contracts, it shortens
- This pulls tendons which move bone at joint
How does the antagonist paring of muscles work?
- Flexors and extensors are antagonistic and allow force in two opposite directions
- Contracting muscle can only move in 1 direction
What is the anatomy of a skeletal muscle? Describe each part.
- Sarcolemma: Plasma membrane of muscle cell
- T-tubule: Tunnel of sarcolemma
- Sarcoplasmic Reticulum (SR): stores Ca2+ ions
How does Excitation-contraction coupling work?
- T-tubules bring AP into skeletal muscle fibers
- Wave of depolarization stimulates SR to release calcium ions
- Extensive SR assures that Ca2+ ions can readily diffuse to all troponin sites
What is a myofibril? What is it made of?
- Muscles contain many muscle fibers
- Muscle fibers contain many myofibrils
- Myofibrils contain many sarcomeres
- Sarcomeres contain many myofilaments
How does a muscle contract?
- Myosin heads (crossbridges) bind to actin
- Myosin head rotates on its hinge, sliding actin filaments past it (powerstroke)
- The thick myosin filament has a flexible cross-bridge with binding sites for both ATP and actin
- Contraction causes sarcomeres to shorten
- Z-lines are pulled closer together
Explain the filament mechanism of muscle contraction.
- Myosin filaments bind to and move actin filaments, causing muscle contraction in skeletal, smooth, and cardiac muscles
- In all three types of muscle, myosin and actin are regulated by the availability of calcium ions
- Changes in the membrane potential of muscles are linked to internal changes in calcium release
- Neurons influence the contraction of muscles by causing changes in muscle membrane potential
*Refer to book for visual!
How does Tropomyosin and Troponin act as regulators?
- Tropomyosin physically blocks cross bridges
- Contraction occurs when Ca2+ ions bind to troponin and the complex pulls tropomyosin away from the cross-bridge binding site
- Myosin can now bind actin
Excitation Contraction Coupling!
Refer to book for visual!!
Describe the process of how a muscle fiber is excited in a neuromuscular junction.
- Incoming AP (Na+) from somatic motor neuron
- Ca2+ enters NMJ through voltage-gated channels
- ACh release from axon terminal, diffuses across synapse, binds to receptors on motor end plate
- Na+ enters muscle cell causing AP along sarcolemma
Define:
- Sarcomere
- Tension
- Motor Unit
- Muscle twitch
- Tetanus
- Fatigue
- Sarcomere: Myofibrils contain many sarcomeres. Sarcomeres contain many myofilaments
- Tension
- Motor unit: A motor unit is a motor neuron and all muscle fibers it controls. All muscle fibers contract together
- Muscle twitch: the response of a skeletal muscle to a single stimulation (or action potential)
- Tetanus: If a muscle fiber is stimulated so rapidly that it does not relax at all between stimuli, a smooth, sustained contraction called tetanus occurs
- Fatigue: is the decline in ability of a muscle to generate force. After a period of maximum contraction, the nerve’s signal reduces in frequency and the force generated by the contraction diminishes
What is a motor unit?
A motor unit is a motor neuron and all muscle fibers it controls
All muscle fibers contract together
How does summation work?
- Refer to diagram or book
1. Complete dissipation of tension between stimuli S1 and S2
2. S4 occurred before the dissipation of tension from S3
3. S6 occurred prior tothe dissipation of ANY tension from S5
What is Tetanus?
- Increasing the frequency of electrical shocks decreases the relaxation time between twitches leading to incomplete tetanus
- At a certain frequency, there will be no relaxation causing complete tetanus
What is the Length tension relationship?
- Tension is maximal when sarcomeres are at normal resting length
- Increasing or decreasing sarcomere length decreases muscle tension due to fewer myosin actin interactions
What function does Phosphocreatine play?
- ATP may be used up faster than it can be created through cellular respiration
- ADP is combined with Pi from phosphocreatine
-Creatine is produced by the liver and kidneys
-Phosphocreatine stores are replenished at rest
What are the three Skeletal Muscle types?
- Not all skeletal muscle fibers (cells) are identical
- As it turns out there are 3 different types of skeletal muscle fibers
SLOW (Oxidative)
INT/FAST (Oxidative-Glycolytic)
FAST (Glycolytic)
What are the characteristics of each type of Skeletal Muscle?
- SLOW-OXIDATIVE skeletal muscle
for ENDURANCE – repetitive stimulation without fatiguing - INTERMEDIATE (OXID-GLYCOLYTIC)
skeletal responds quickly and to repetitive stimulation without fatigue - FAST-GLYCOLYTIC skeletal muscle
is used for quick bursts of POWER
What are the characterisitics of Dark vs White meat?
What are the characteristics of smooth muscle?
- No sarcomeres
- Thick and thin filaments interact to cause contraction
What is the difference between Single unit and Multi unit smooth muscle?
- Single-unit (a) : gap junctions, neighboring cells act as unit
-Most smooth muscle single-unit - Multi-unit (b) : require individual nerve innervation
-Few or no gap junctions
-Arrector pili in skin and ciliary muscles in eyes
