CH10 Flashcards
Characteristics of skeletal muscle
- Location: Skeletal, sphincter, urethra, anus
- Function: Moves bones, produces heat
- Appearance: multinucleated; striated
- Voluntary
Characteristics of cardiac muscle
- Location: Heart
- Function: pump blood
- Appearance: striated; one nucleus; intercalated disc (specialized junctions to connect cardiac muscle)
- Involuntary
Characteristics of smooth muscle
visceral
- Location: walls of hollow internal organs; vessels, airways, stomach, bladder, uterus
- Function: moves materials through organs
- Appearance: smooth; one nucleus
- Involuntary
Properties of muscular tissue
- Electrically excitable: produces electrical signals (action potentials) when stimulated
- Contractility: ability of muscle to shorten/lengthen and produce force in response to a stimulus
- Extensibility: the ability of a muscle to be stretched or extended without damage
- Elasticity: ability of muscles to return to their original length after being stretched or contracted
Function of muscular tissue
- Produce body movement
- Stabilize body positions
- Storing and moving body substances within the body
- Generating heat
Fascia
most superficial connective tissue of skeletal muscles and anchors muscles and other organs of the body
Fascicles
bundles of muscle fibers within skeletal muscles, covered by perimysium
Muscle fibers
the individual, elongated cells that make up muscle tissue, responsible for contraction and movement, gives striated appearance, covered by endomysium
Epimysium
- outer layer, covers skeletal muscle, overlies sarcolemma (muscle cell membrane)
- allows the muscle to contract and move powerfully while maintaining its structural integrity, and separates tissues
Perimysium
covers each fascicle and separates them
Endomysium
surrounds each fiber, contains extracellular fluid and nutrients to support muscle fiber
What tissues fuse muscle and tendon together?
Epimysium, perimysium, endomysium
Tendons
rope-like connective tissue anchors muscle to bone
Aponeurosis
- sheet-like (flat) connective tissues. Attached muscle to bone or muscle to muscle
- EX: latissiumus dorsi and linea alba
Cell parts (of muscle)
Sarcolemma
plasma membrane of muscle fibers
Cell parts (of muscle)
T tubules
extensions of the sarcolemma that go deeper into the muscle fiber and allows action potentials to reach further into the interior of the cell
transverse tubules
Cell parts (of muscle)
Action potential
a brief electrical signal that allows nerve cells (neurons) and muscle cells to transmit information
Cell parts (of muscle)
Sarcoplasm
cytoplasm
Cell parts (of muscle)
Sarcoplasmic reticulum
smooth endoplasmic reticulum, where Calcium is released
Cell parts (of muscle)
Myofibrils
specialized contractile organelles found within muscle fibers, made up of 3 proteins - contractile, regulatory and structural
Contractile proteins
generate force during muscle contraction (myosin and actin)
Regulatory proteins
determine when muscle contracts and relaxes (troponin and tropomyosin)
Structural proteins
keeps thick and thin filaments in alignment, links myofibrils to sarcolemma (titin, nebulin, alpha-actin, myomesin, dystropohn)
Sarcomere
- Functional unit of a skeletal muscle fiber; region from one Z-line to the next Z-line
- Linked together (end to end) creating myofibrils.
- Composed of actin (thin) filaments and the myosin (thick) filaments.
- Sarcomeres are divided into bands and zones depending on the area and contain thick filaments, thin filaments, or both.
Which part of the sarcomere is lighter and contains only thick filaments?
I Band: lighter; contains only thin filaments
What protein is recognized as thick filaments?
H zone: narrow area in the center of each A band that contains thick filaments
This region of the sarcomere is in the center of the H zone?
M line: region in the center of the H zone that contains proteins that hold thick filaments together at the center of the sarcomere
The z discs pass through which structure?
Z discs pass through the center of each I band; Z discs are the end of the sarcomere
What part of sarcomere creates darker striations
A Band: darker middle part includes the entire length of the thick filaments
What is muscle metabolism?
- Biochemical processes that provide enrgy for muscle contraction and function
- Involves the breakdown and synthesis of molecules to generate ATP
What occurs when oxygen is not available during muscle metabolism process?
- pyruvic acid is converted to lactic acid, which may contribute to muscle fatigue.
- This occurs during strenuous exercise when high amounts of energy are needed but oxygen cannot be sufficiently delivered to muscle
What is needed for contraction to happen?
calcium
What are the 4 steps for sliding filament mechanism?
- ATP hydrolysis.
ATP binds to myosin head, it is hydrolyzed (broken down) into ADP and a phosphate group. The energy released from this reaction is stored within myosin head to be used in later phases of the contraction cycle. - Cross-Bridge-
attachment of myosin to actin. Calcium ions are released into the SR which flood the sarcoplasm and bind to protein troponin. - Power stroke.
Once the cross-bridge has been formed, the myosin head utilizes the energy derived from the hydrolysis of ATP and pulls the actin filament towards the center of the sarcomere - which cause fiber to shorten - Detachment of myosin from actin.
A new ATP molecule binds to the myosin head, causing it to detach from the actin filament. In the absence of ATP, the myosin head will not detach from the binding site.
Neuromuscular Junction
responsible for transmitting electrical impulses from the nervous system to the muscles, triggering muscle contraction
Where does the neuromuscular junction take place at?
Occurs at the motor end plate
Motor end plate
specialized region of muscle fibers membrane that has receptors for the neurotransmitter
Twitch contraction
- a brief contraction of all muscle fibers in a motor unit in response to an action potential. EX: quick reflex
- Latent Period: delay following an action potential.
- Contraction Period: Calcium binds to troponin; peak contraction
- Relaxation Period: Calcium is transported back into the sarcoplasmic reticulum.
- Refractory Period: the period of lost excitability.
Wave summation
occurs when stimulations to muscle fiber is faster than it is able to completely relax
Tetanus
the stimulus frequency is so high that the relaxation phase disappears completely, the contractions become continuous. Ex: running
What are isotonic contractions?
- muscle length changes
- Eccentric: muscle elongates, ex: downward motion of bicep curl
- Concentric: muscle contraction
Isometric contractions
muscle length does not change. Ex: holding weight at 90º during bicep curl
Motor unit
- A motor unit consists of one motor neuron and all the muscle fibers it innervates.
- Every skeletal muscle fiber is supplied by a motor neuron
Motor Unit Recruitment
- takes place when the number of active motor units increases.
- weakest motor units are recruited first, followed by stronger motor units.
- motor units contract alternately in order to sustain a contraction (for longer periods of time).
Types of muscle fibers
Slow oxidative (SO) fibers
- endurance exercises; requires little force (numerous repetitions over a longer period)
- Angiogenesis: can occur (formation of capillary networks around the fiber)
- This increases the oxygen supply and waste removal to/from cells.
- Examples: Cross Country, marathon runner
Types of muscle fibers
Fast oxidative glycolytic (FOG) fibers
- Also known as intermediate fibers (have characteristics between fast fibers and slow fibers)
- They are oxidative because they produce ATP aerobically. (high amounts of mitochondria, and do not fatigue quickly)
- Not a significant amount of myoglobin
- Examples: soccer player
- More fatigue-resistant than fast glycolytic fibers.
aging with muscles
- skeletal muscle is replaced by fibrous connective tissue and adipose tissue
- Atrophy
- Decrease in strength leads to decrease in posture and mobility (balance).
- Reduced amount of motor units being stimulated
Types of muscle fibers
Fast Glycolytic (FG)
- FG fibers are used to produce rapid, forceful contractions to make quick, powerful movements.
- FG fibers fatigue rapidly (short periods) due to the lack of O2
- Example: shot putter
Sarcopenia
muscle atrophy with age (irreversible). As we age, muscle fiber die and are replaced with connective tissue (and adipose tissue)
