Untitled Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What components make up a motor unit?

Somatic motor neuron and cardiac muscle fibers

Somatic motor neuron and skeletal muscle fibers (correct)

Sensory neuron and skeletal muscle fibers

Somatic motor neuron and smooth muscle fibers

How does motor unit recruitment contribute to muscle contractions?

By ensuring all motor units fire simultaneously for maximum strength

By limiting the activation of larger motor units for precision

By firing motor units asynchronously for smooth contractions (correct)

By activating all motor units only during heavy lifting

What characterizes muscle tone?

The voluntary contraction of all motor units

The involuntary contraction of a large number of motor units

The relaxation of all muscle fibers

The involuntary contraction of a small number of motor units (correct)

In what way are large motor units utilized during muscle contractions?

When large tension is required Signup and view all the answers

What is a primary function of muscle tone?

To maintain posture and keep the body upright Signup and view all the answers

Which factor does NOT contribute to muscle fatigue?

Excessive calcium in neurons Signup and view all the answers

What are the two sources of oxygen for muscle tissue during aerobic activity?

Blood and released myoglobin Signup and view all the answers

What is oxygen debt primarily associated with?

Elevated O2 use after exercise Signup and view all the answers

Which of the following describes central fatigue?

A protective mechanism against overexertion Signup and view all the answers

What is the primary function of the aerobic system during prolonged activity?

Production of ATP using oxygen Signup and view all the answers

What type of muscle tissue is characterized as non-striated and involuntary?

Smooth muscle Signup and view all the answers

Which connective tissue sheath surrounds an entire muscle?

Epimysium Signup and view all the answers

What is the smallest contractile unit of a muscle called?

Sarcomere Signup and view all the answers

What role do satellite cells play in mature muscle tissue?

Regenerating new muscle cells Signup and view all the answers

Which components make up myofilaments in muscle tissue?

Actin and myosin Signup and view all the answers

What function does the sarcoplasmic reticulum serve in muscle fibers?

Stores and regulates calcium levels Signup and view all the answers

What structure within a muscle fiber carries action potentials deep into the cell?

T-tubules Signup and view all the answers

Which of the following is not a part of the connective tissue sheaths surrounding muscle fibers?

Sarcomere Signup and view all the answers

Which proteins are primarily responsible for muscle contraction?

Myosin and Actin Signup and view all the answers

What role does Troponin play in muscle contraction?

Covers the myosin-binding site on actin during relaxation Signup and view all the answers

How do Z Discs contribute to muscle contraction?

By coming toward each other during contraction Signup and view all the answers

Which protein helps align thin filaments and is inelastic?

Nebulin Signup and view all the answers

What is the function of Titin in muscle fibers?

Provides recovery from muscle stretching Signup and view all the answers

What occurs immediately after Ca++ binds to Troponin?

Troponin moves tropomyosin away from actin Signup and view all the answers

What initiates the process of excitation-contraction coupling in muscle cells?

Motor neuron excitation at the NMJ Signup and view all the answers

Which protein connects thin filaments to the sarcolemma?

Dystrophin Signup and view all the answers

What role does acetylcholinesterase (AchE) play at the muscle end-plate?

It removes acetylcholine from the synaptic cleft. Signup and view all the answers

Which statement correctly describes what occurs during cross-bridge cycling cessation?

Active transport pumps calcium back into storage. Signup and view all the answers

What effect does botulinum toxin have on neuromuscular function?

It prevents acetylcholine release. Signup and view all the answers

Which source provides immediate ATP supply in muscles?

Phosphagen system. Signup and view all the answers

What is the primary by-product of anaerobic respiration when oxygen is not available?

Lactic acid. Signup and view all the answers

Which of the following statements about creatine phosphate is true?

It provides a rapid source of ATP in muscles. Signup and view all the answers

Neostigmine has what function related to acetylcholine?

It inhibits acetylcholinesterase activity. Signup and view all the answers

Which factor primarily determines the efficiency of energy production in aerobic vs anaerobic respiration?

The availability of oxygen. Signup and view all the answers

What is the first step in the contraction cycle?

Cross bridge formation Signup and view all the answers

What process allows the thick and thin filaments to move past each other during muscle contraction?

Presence of Ca+2 ions Signup and view all the answers

What occurs during the power stroke of muscle contraction?

Myosin head pivots and pulls the actin Signup and view all the answers

What is rigor mortis a result of after death?

ATP synthesis has ceased Signup and view all the answers

Which component is NOT part of the neuromuscular junction (NMJ)?

Sarcoplasmic reticulum Signup and view all the answers

What happens to the myosin head during the reset phase of the contraction cycle?

It hydrolyzes ATP to ADP + P Signup and view all the answers

What structure is responsible for releasing acetylcholine during nerve stimulation of skeletal muscle?

Synaptic vesicles Signup and view all the answers

How long does rigor mortis typically last after death?

3-4 hours Signup and view all the answers

Which of the following events directly follows the attachment of myosin to actin?

ADP and P are released Signup and view all the answers

What is the function of the synaptic cleft in the neuromuscular junction?

Facilitates the release of neurotransmitters Signup and view all the answers

Study Notes

Muscle Tissue Overview

Chemical energy is converted to mechanical energy, generating force, performing work, and producing movement.
Myology is the study of muscle.
Prefixes "myo," "mys," and "sarco" all relate to muscle.

Functions of Muscle Tissue

Muscle tissue enables body movement.
It maintains posture.
It protects and supports various body parts.
It stores and moves materials within the body.
It generates heat.

Special Properties of Muscle Tissue

Excitability
Conductivity (action potentials)
Contractility
Extensibility
Elasticity

Types of Muscle Tissue

Skeletal Muscle

Attaches to bone, skin, or fascia.
Striated appearance.
Voluntary control of contraction and relaxation.

Cardiac Muscle

Striated.
Involuntary.
Autorhythmic (pacemaker).

Smooth Muscle

Non-striated.
Involuntary.
Found in arrector pili and walls of hollow organs.

Gross Anatomy of Skeletal Muscle

A muscle is an organ.
Fascia is connective tissue surrounding a muscle.
Connective tissue sheaths (epimysium, perimysium, endomysium) surround the muscle, bundles of fibers, and individual fibers, respectively.
Tendons connect muscle to bone.

Skeletal Muscle Nerve and Blood Supply

Skeletal muscle is supplied by nerves, arteries, and veins.
Somatic motor neurons form the neuromuscular junction.

Fusion of Myoblasts into Muscle Fibers

Mature muscle is derived from more than 100 myoblasts.
Mature muscle cells cannot divide further.
Satellite cells retain the ability to regenerate new cells.

Muscle Fiber or Myofibers

Sarcolemma is the muscle fiber membrane.
Sarcoplasm is filled with myofibrils and myoglobin.

Sarcomere

The sarcomere is the smallest contractile unit of a muscle.
Located between two successive Z discs.
Composed of overlapping myofilaments (actin and myosin).

Myofibrils & Myofilaments

Myofibrils are separated by the sarcoplasmic reticulum (SR).
Myofilaments are the contractile proteins within muscle tissue.

Sarcoplasmic Reticulum (SR)

System of tubular sacs (smooth ER) enveloping myofibrils.
Regulates calcium (Ca2+) levels.
Stores Ca2+ in relaxed muscle.
Releases Ca2+ during contraction via voltage-gated channels.

Transverse Tubules (T-tubules)

Invaginations of the sarcolemma into the cell.
Filled with extracellular fluid.
Carry action potentials into the cell interior.
Mitochondria are located near muscle proteins that use ATP.

Filaments & Sarcomere

Striations are produced by the arrangement of thick and thin filaments within a sarcomere (the I-band and A-band).
Overlap region: thick and thin filaments overlap.
Supporting proteins: M line, titin, Z disc anchor thick and thin filaments in place.

Regions of a Sarcomere of a Myofibril

Regions include the Z disc, M line, H zone, I band, and A band.

Proteins of Muscle

Myofibrils contain three types of proteins:
- Contractile: Myosin and actin
- Regulatory: Troponin and tropomyosin
- Structural: Titin, myomesin, nebulin, and dystrophin.

Thick Filaments

Composed of myosin.
Myosin heads are responsible for binding to actin.

Thin Filaments

Composed of actin, tropomyosin, and troponin
Myosin-binding site is typically covered by tropomyosin in relaxed muscles, preventing interaction with myosin.
Thin filaments are held in place by Z lines.

Other Structural Proteins

Titin anchors thick filaments to both the M line and Z disc.
M line (myomesin) connects adjacent thick filaments and titin.
Nebulin aligns thin filaments.
Dystrophin links thin filaments to the sarcolemma and transmits tension to tendons.

Sliding Filament Mechanism of Contraction

Myosin cross-bridges pull on thin filaments, causing them to slide inward.
Z discs move closer together, shortening sarcomeres.
Shortening of sarcomeres causes the entire muscle fiber to shorten.

Muscle Gross Anatomy Summary

Parts of a muscle (tendon, epimysium, perimysium, endomysium, fascicle, myofibril, myofilament, organelle, and muscle fiber).

Muscle Scale

Parts of a muscle (endomysium, perimysium, epimysium, fascicle, skeletal muscle—organ, tendon, bone, actin myofilament, myosin myofilament, sarcomere, nuclei, capillary, mitochondrion, muscle myofibrils).

Nerve Stimulus of Skeletal Muscle

Motor neurons in the somatic nervous system innervate muscle cells.
Motor neurons branch and form neuromuscular junctions with single muscle fibers.
The neuromuscular junction is formed by axonal endings, the motor end plate of a muscle, and the synaptic cleft.

Synaptic Region

Synaptic end bulbs contain synaptic vesicles (acetylcholine).
The motor end plate has acetylcholine receptors.

Excitation of Skeletal Muscle Fiber

Nerve signals trigger the release of acetylcholine (ACh) from synaptic vesicles.
ACh binds to receptors on the sarcolemma.
This leads to an action potential in the sarcolemma.
The action potential travels down the T-tubules.
This triggers the release of calcium (Ca2+) from the sarcoplasmic reticulum (SR).

Excitation-Contraction Coupling

Depolarization of muscle fibers.
Propagation of action potentials along the sarcolemma and T-tubules.
Release of Ca2+ from the SR.

Overview of Skeletal Muscle Contraction

Excitation of the muscle fiber (neuromuscular junction).
Propagation of action potential along the sarcolemma and T-tubules.
Release of Ca2+ from the sarcoplasmic reticulum.
Cross-bridge cycling, sliding of thin filaments, and muscle shortening.

Relaxation-Acetylcholinesterase

Enzyme acetylcholinesterase removes acetylcholine (ACh).
Muscle action potentials cease.
Sodium ions are pumped out of the cell.
Cross-bridge cycling ceases as Ca2+ is transported back into the sarcoplasmic reticulum;
tropomyosin recovers the binding site on actin.

Pharmacology of the NMJ

Botulinum toxin prevents acetylcholine (ACh) release.
Curare blocks ACh receptors.
Neostigmine is a reversible acetylcholinesterase inhibitor.

Muscle Metabolism

Muscle uses ATP during activity.
Sources of ATP production include immediate, short-term, and long-term.

Immediate Supply of ATP: Phosphagen System

ATP is produced using ATPase, myokinase, and creatine kinase.

Short-Term Supply of ATP: Anaerobic Cellular Respiration

Pyruvic acid is converted to lactic acid.
Lactic acid can return to the liver and be converted back to pyruvic acid when oxygen is available.

Long-Term Supply of ATP: Aerobic Cellular Respiration

ATP production in mitochondria from pyruvic acid, fatty acids, and amino acids.

Creatine Phosphate

Excess ATP produced in resting muscle is utilized to create creatine phosphate.
Quick breakdown of creatine phosphate releases energy for muscle contraction.
Creatine supplementation decreases innate production.

Fermentation: Anaerobic Cellular Respiration

If oxygen is not present, pyruvic acid is converted into lactic acid.
Lactic acid returns to the liver when oxygen is available and converted to pyruvic acid.

Anaerobic vs Aerobic Cellular Respiration

Comparison of anaerobic and aerobic respiration for energy production.

Aerobic Cellular Respiration

ATP production in mitochondria from pyruvic acid, fatty acids, and amino acids.

Muscle Fatigue

Central fatigue (protective mechanism).
Factors that contribute to muscle fatigue: Insufficient oxygen or glycogen, build-up of lactic acid and phosphates, insufficient release of acetylcholine (ACh) from motor neurons, and sodium and potassium imbalances in the cell.

Oxygen Consumption After Exercise

Muscle tissue uses two sources of oxygen: diffusion from blood and release from myoglobin inside muscle fibers.
Aerobic systems require oxygen to produce ATP needed for prolonged activity; elevated oxygen use is called oxygen debt.
Factors include hemoglobin, myoglobin, glycogen stores, and ATP/creatine phosphate stores.
Lactic acid is converted back to pyruvic acid.
Body temperature increases.

Skeletal Muscle Fiber Types

Three fiber types (slow oxidative, fast oxidative, fast glycolytic) are present, differing in their ATP production capacity, and function. Knowledge of each type's characteristics is crucial for understanding whole-fiber properties.

The Motor Unit

Motor unit = somatic motor neuron and skeletal muscle fibers it stimulates.
Total strength of contraction depends on the number of motor units activated.

Motor Unit Recruitment

Motor units are recruited asynchronously to produce smooth muscular contractions.
Precise movements require smaller motor units.
Larger motor units are recruited when greater tension is needed.

Muscle Tone

Involuntary contraction of a small number of motor units keeps muscles firm; essential for posture and maintaining blood pressure.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.