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Questions and Answers
What covers myosin binding sites?
What covers myosin binding sites?
- Myosin
- Actin
- Tropomyosin (correct)
- Troponin
What is the refractory period?
What is the refractory period?
When a muscle fiber receives enough stimulation to contract, it temporarily loses its excitability and cannot respond for a time.
What is wave summation?
What is wave summation?
When a second stimulus occurs after the refractory period of the first stimulus is over but before the skeletal muscle fiber has relaxed, resulting in a stronger contraction.
What type of contraction occurs in your neck muscles while you are walking?
What type of contraction occurs in your neck muscles while you are walking?
What is hypotonia?
What is hypotonia?
What is flaccid paralysis?
What is flaccid paralysis?
What is hypertonia?
What is hypertonia?
What is spasticity?
What is spasticity?
What is spastic paralysis?
What is spastic paralysis?
What does rigidity refer to in muscle tone?
What does rigidity refer to in muscle tone?
What disease is caused by Clostridium tetani?
What disease is caused by Clostridium tetani?
What is isotonic contraction?
What is isotonic contraction?
What is isometric contraction?
What is isometric contraction?
What type of smooth muscle is more like cardiac muscle?
What type of smooth muscle is more like cardiac muscle?
What part of a somite differentiates into skeletal muscle?
What part of a somite differentiates into skeletal muscle?
What does the myotome form?
What does the myotome form?
What does the dermatome form?
What does the dermatome form?
What does the sclerotome give rise to?
What does the sclerotome give rise to?
What type of muscle develops from mesodermal cells that migrate to and envelop the developing heart?
What type of muscle develops from mesodermal cells that migrate to and envelop the developing heart?
What type of muscle develops from mesodermal cells that migrate to and envelop the developing gastrointestinal tract and viscera?
What type of muscle develops from mesodermal cells that migrate to and envelop the developing gastrointestinal tract and viscera?
What is the outer layer encircling the entire muscle called?
What is the outer layer encircling the entire muscle called?
What connective tissue coat surrounds groups of muscle fibers, separating them into fascicles?
What connective tissue coat surrounds groups of muscle fibers, separating them into fascicles?
What penetrates the interior of each fascicle and separates individual muscle fibers?
What penetrates the interior of each fascicle and separates individual muscle fibers?
What term describes the built-in rhythm of the heart?
What term describes the built-in rhythm of the heart?
What are the ringlike bands of smooth muscle called that prevent outflow of the contents of a hollow organ?
What are the ringlike bands of smooth muscle called that prevent outflow of the contents of a hollow organ?
What process describes heat production due to muscle contractions?
What process describes heat production due to muscle contractions?
What are the electrical signals produced by muscle and nerve cells called?
What are the electrical signals produced by muscle and nerve cells called?
What type of connective tissue lines the body wall and surrounds muscles?
What type of connective tissue lines the body wall and surrounds muscles?
What attaches muscle to the periosteum of a bone?
What attaches muscle to the periosteum of a bone?
What is the broad, flat sheet of connective tissue that extends from the muscle called?
What is the broad, flat sheet of connective tissue that extends from the muscle called?
What chronic disorder affects the fibrous connective tissues of muscles?
What chronic disorder affects the fibrous connective tissues of muscles?
What is the plasma membrane of a muscle cell called?
What is the plasma membrane of a muscle cell called?
What term describes the functional unit of a myofibril?
What term describes the functional unit of a myofibril?
What are the proteins that hold thick filaments together in the center of a sarcomere called?
What are the proteins that hold thick filaments together in the center of a sarcomere called?
What happens to the I band and H zone during muscle contraction?
What happens to the I band and H zone during muscle contraction?
What is oxygen debt?
What is oxygen debt?
What is the role of ATP in muscle contraction?
What is the role of ATP in muscle contraction?
What happens if ATP suddenly were not available after the sarcomere had started to shorten?
What happens if ATP suddenly were not available after the sarcomere had started to shorten?
What is the effect of the size of a motor unit on its strength of contraction?
What is the effect of the size of a motor unit on its strength of contraction?
The contraction of skeletal muscle occurs due to thick and thin filaments sliding past one another.
The contraction of skeletal muscle occurs due to thick and thin filaments sliding past one another.
What do synaptic end bulbs at the tips of axon terminals contain?
What do synaptic end bulbs at the tips of axon terminals contain?
What separates a somatic motor neuron and a skeletal muscle fiber?
What separates a somatic motor neuron and a skeletal muscle fiber?
Study Notes
Connective Tissue of Muscles
- Epimysium: Dense irregular connective tissue that surrounds the entire muscle.
- Perimysium: Encases groups of 10 to 100 muscle fibers, forming bundles known as fascicles.
- Endomysium: Surrounds individual muscle fibers within fascicles, composed of mostly reticular fibers.
Muscle Properties
- Autorhythmicity: The heart's intrinsic rhythm.
- Sphincters: Smooth muscle bands controlling the outflow from hollow organs.
- Thermogenesis: Heat production as a result of muscle contraction.
Muscle Fiber Structure
- Sarcolemma: Plasma membrane of a muscle cell housing multiple nuclei.
- Sarcoplasm: Cytoplasm of muscle fibers containing glycogen and myoglobin for ATP synthesis.
- Myofibrils: Contractile organelles densely packed within muscle fibers.
Filaments and Contraction Mechanism
- Thin Filaments: Primarily composed of actin and anchored at Z-discs.
- Thick Filaments: Composed of myosin; thick filaments are essential for muscle contraction through cross-bridge formation.
- Sarcomeres: Basic functional units of myofibrils, defined by Z-discs, A-bands, I-bands, H-zones, and M-lines.
Muscle Contraction
- Sliding Filament Mechanism: Shortening occurs as thin filaments slide over thick filaments without changing their lengths.
- Calcium Role: Increased Ca2+ levels initiate contraction, while decreased levels cause relaxation.
- ATP Functions: Hydrolyzes to activate myosin, detach myosin from actin, and power calcium pumps in the SR.
Muscle Contraction Phases
- Latent Period: Initial stage when muscle potential is generated and calcium ions are released.
- Contraction Period: Calcium binds to troponin, exposing myosin-binding sites for cross-bridge formation.
- Relaxation Period: Calcium is transported back into the SR, detaching myosin heads and reducing tension.
Neuromuscular Junction
- Nerve-Muscle Interaction: Synapse where motor neurons communicate with muscle fibers through neurotransmitters.
- Acetylcholine's Role: Triggers muscle action potentials leading to contraction.
Muscle Responses
- Wave Summation: Increased tension from stimuli occurring before relaxation is complete.
- Motor Units: Composed of a motor neuron and the muscle fibers it stimulates; larger units produce more force.
Muscle Tone and Disorders
- Hypotonia: Reduced muscle tone resulting in flaccidity.
- Hypertonia: Increased muscle tone, seen in conditions like spasticity and rigidity.
- Tetanus: A serious bacterial infection causing severe muscle spasm and stiffness.
Specialized Muscle Proteins
- Titin: Provides elasticity and stabilizes thick filaments.
- Myoglobin: Oxygen-binding protein facilitating ATP production during muscle contraction.
- Dystrophin: Links sarcomeres to the muscle fiber membrane, essential for muscle structure and function.
Key Facts
- Muscle fibers are multinucleated and can regenerate through myoblast fusion.
- Mitochondria are crucial for ATP production in muscle fibers.
- Calcium release from the SR is key for initiating muscle contraction following nerve impulses.
Muscle Contractions
- Isotonic Contraction: Muscle tense and shortens, allowing body movements and object manipulation while maintaining constant force.
- Isometric Contraction: Muscle generates tension but does not change length due to resistance, thus not moving the object.
Types of Smooth Muscle
- Visceral Smooth Muscle: More similar to cardiac muscle than skeletal muscle, characterized by gap junctions enabling action potentials to spread between cells.
Muscle Development
- Hyperplasia: Refers to the increase in the number of muscle fibers.
- Myotome: A structure within a somite that differentiates into skeletal muscle, forming muscles in the head, neck, and limbs.
- Dermatome: A region of a somite that develops into connective tissues, including the dermis of the skin.
- Sclerotome: The part of a somite responsible for giving rise to vertebrae.
Developmental Origins of Muscle Types
- Cardiac Muscle: Forms from mesodermal cells that migrate to surround the developing heart in the form of endocardial heart tubes.
- Smooth Muscle: Develops from mesodermal cells migrating to envelop the developing gastrointestinal tract and other viscera.
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Explore key terms related to muscular tissue with these flashcards. Each card defines essential components such as epimysium, perimysium, and endomysium, helping you solidify your understanding of muscular anatomy. Perfect for students studying muscle structure and function.
