Chapter 10 Flashcards
What is the primary function of skeletal muscles in terms of movement?
keletal muscles move the body by moving bones, enabling actions like facial expressions, speaking, breathing, and swallowing
How do skeletal muscles help with posture?
Skeletal muscles stabilize joints and maintain body position to help keep posture.
What role do skeletal muscles play in protecting and supporting the body?
Skeletal muscles package internal organs and hold them in place, offering protection and support.
How do skeletal muscles regulate elimination of materials from the body?
Circular sphincters in skeletal muscles control the passage of material at body orifices, such as the anus and urethra.
How do skeletal muscles contribute to maintaining body temperature?
Skeletal muscles produce heat during contraction, helping to regulate body temperature.
Elasticity
ability to return to original length following a
lengthening or shortening
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Extensibility
ability to be stretched
Contractility
exhibited when filaments slide past each other
what Enables muscle to cause movement
Contractility
conductivity
involves sending an electrical change down
the length of the cell membrane
excitability
ability to respond to a stimulus by changing
electrical membrane potential
What is the skeletal muscle considered in terms of anatomy?
A skeletal muscle is considered an organ made up of multiple tissue types working together: muscle fibers, connective tissue, blood vessels, and nerves
How are muscle fibers arranged within a muscle?
Muscle fibers are bundled together within a fascicle.
What is a fascicle in the context of skeletal muscle?
A fascicle is a bundle of muscle fibers, and a whole muscle contains many fascicles.
What is a muscle fiber?
A muscle fiber is a single muscle cell, which makes up the fascicles within a skeletal muscle.
What are the three concentric layers of connective tissue in skeletal muscle?
The three layers are the epimysium, perimysium, and endomysium
What is the epimysium?
The epimysium is a dense irregular connective tissue that wraps the entire skeletal muscle.
What is the perimysium and its function?
The perimysium is a dense irregular connective tissue that wraps each fascicle (bundle of muscle fibers). It houses many blood vessels and nerves.
What is the endomysium and its function?
The endomysium is a delicate layer of areolar connective tissue that wraps individual muscle fibers. It provides electrical insulation, supports capillaries, and binds neighboring muscle cells together.
What are the two types of muscle attachments to bone, skin, or other muscles?
Tendons and aponeuroses
What is a tendon?
A tendon is a cordlike structure made of dense regular connective tissue that attaches muscle to bone, skin, or other muscles.
What is an aponeurosis?
An aponeurosis is a thin, flattened sheet of dense irregular connective tissue that attaches muscle to bone, skin, or other muscles.
What is deep fascia and its function?
Deep fascia is dense irregular connective tissue located superficial to the epimysium. It separates individual muscles and binds muscles with similar functions together.
What is superficial fascia and its function?
Superficial fascia is made of areolar and adipose connective tissue, located superficial to the deep fascia. It separates muscles from the skin.
How are skeletal muscles vascularized?
Skeletal muscles are highly vascularized, with extensive blood vessels that deliver oxygen and nutrients while removing waste products
What type of neurons innervate skeletal muscles?
Skeletal muscles are innervated by somatic motor neurons.
How do somatic motor neurons communicate with skeletal muscle fibers?
The axons of somatic motor neurons branch and terminate at neuromuscular junctions, where they transmit signals to muscle fibers.
Why is skeletal muscle considered voluntary?
Skeletal muscle is considered voluntary because its contraction is consciously controlled.
What is the sarcoplasm of a muscle cell, and what does it contain?
The sarcoplasm is the cytoplasm of a muscle cell. It contains typical organelles as well as contractile proteins and other special structures necessary for muscle function.
what is unique about the nuclei of muscle cells?
Muscle cells (fibers) are multinucleated, meaning they contain multiple nuclei, which form when individual myoblasts fuse during embryonic development.
What are satellite cells, and what is their function?
Satellite cells are undifferentiated myoblasts located near muscle fibers. They provide support and repair muscle fibers after injury.
What is the sarcolemma, and what role does it play in muscle cell function?
The sarcolemma is the plasma membrane of a muscle cell. It contains voltage-gated ion channels that help conduct electrical signals necessary for muscle contraction.
What are T-tubules, and what is their function in muscle cells?
T-tubules (transverse tubules) are extensions of the sarcolemma that penetrate deep into the muscle cell. They contain voltage-sensitive calcium channels, which play a key role in muscle contraction by allowing calcium to enter the cell.
What are myofibrils in a muscle cell?
Myofibrils are bundles of myofilaments (actin and myosin) that are enclosed in the sarcoplasmic reticulum. A muscle cell can contain hundreds to thousands of myofibrils.
What is the function of the sarcoplasmic reticulum in muscle cells?
The sarcoplasmic reticulum is an internal membrane complex similar to the smooth endoplasmic reticulum. It stores and regulates calcium ions, which are crucial for muscle contraction.
What are myofilaments in muscle cells?
Myofilaments are contractile proteins within myofibrils that enable muscle contraction. There are two types: thick filaments and thin filaments.
What are thick filaments made of?
Thick filaments are made up of bundles of many myosin protein molecules. The myosin heads point toward the ends of the filament
What are thin filaments made of?
Thin filaments are twisted strands of actin. Each F-actin strand is composed of G-actin monomers.
What is the role of G-actin in muscle contraction
: G-actin has myosin-binding sites where the myosin heads attach during muscle contraction.
What regulatory proteins are associated with thin filaments?
Tropomyosin and troponin are regulatory proteins present on the thin filaments. They help control the interaction between actin and myosin during contraction.
What is a sarcomere?
A sarcomere is the repeating unit of a muscle fiber that contains overlapping thick and thin myofilaments.
What structure delineates the ends of a sarcomere?
The ends of a sarcomere are delineated by Z discs, which are specialized proteins that anchor the thin filaments
What is the function of the Z discs in a sarcomere?
The Z discs serve as anchors for the thin filaments and help define the boundaries of a sarcomere.
What do the positions of thin and thick filaments create in a sarcomere?
The arrangement of thin and thick filaments creates alternating light I-bands and dark A-bands in the sarcomere.
What do the I bands represent in a sarcomere?
The I bands are light-appearing regions that contain only thin filaments. They are bisected by the Z disc.
How do the I bands change during muscle contraction?
The I bands get smaller during muscle contraction and can disappear completely during maximal contraction.
What is the A band in a sarcomere?
The A band is the dark-appearing region of the sarcomere that contains thick filaments and overlapping thin filaments. It makes up the central region of the sarcomere.
What structures are found within the A band?
The A band contains the H zone (region with only thick filaments) and the M line (middle of the sarcomere where thick filaments are anchored).
What is the H zone in a sarcomere?
The H zone is the central portion of the A band, where only thick filaments are present, and there is no overlap with thin filaments.
how does the H zone change during muscle contraction?
The H zone disappears during maximal muscle contraction as the thin filaments slide over the thick filaments and overlap more.
What is the M line in a sarcomere?
The M line is located in the middle of the H zone and serves as the attachment site for thick filaments. It is composed of a protein meshwork structure.
Why do muscle fibers have abundant mitochondria?
Muscle fibers have abundant mitochondria to support aerobic ATP production, which is essential for sustained muscle contraction.
What role does myoglobin play in muscle cells?
Myoglobin within muscle cells stores oxygen, which is used for aerobic ATP production during muscle contraction.
What is glycogen, and how is it used by muscle cells?
Glycogen is a stored form of glucose in muscle cells. It provides a rapid source of fuel for ATP production when needed quickly during intense activity.
What is creatine phosphate, and how does it help muscle cells?
Creatine phosphate is a molecule that can quickly donate its phosphate group to replenish ATP supplies, providing an immediate source of energy for muscle contraction.
What is a motor unit in skeletal muscle?
A motor unit consists of a motor neuron and all the muscle fibers it controls.
How do motor neurons innervate skeletal muscle fibers?
Axons of motor neurons from the spinal cord (or brain) innervate multiple muscle fibers, forming motor units.
How does the number of muscle fibers innervated by a motor neuron vary?
The number of muscle fibers a motor neuron innervates can vary: small motor units innervate fewer fibers, while large motor units innervate thousands of fibers
What is the function of small motor units?
Small motor units, with fewer than five muscle fibers, allow for precise control of muscle force output.
What is the function of large motor units?
Large motor units, with thousands of muscle fibers, allow for the production of a large amount of force, but they do not provide precise control
How are the muscle fibers of a motor unit arranged in a muscle?
The muscle fibers of a motor unit are dispersed throughout the muscle, not located in a single, clustered compartment.
What is the neuromuscular junction?
The neuromuscular junction is the location where a motor neuron innervates a muscle fiber, allowing communication for muscle contraction.
Where is the neuromuscular junction typically located on a muscle fiber?
The neuromuscular junction is usually located at the mid-region of the muscle fiber.
What are the main components of the neuromuscular junction?
The neuromuscular junction consists of three main parts: the synaptic knob, the synaptic cleft, and the motor end plate.
What is the synaptic knob?
The synaptic knob is the expanded tip of the motor neuron axon at the neuromuscular junction. It plays a key role in transmitting signals to the muscle fiber.
What do synaptic vesicles in the synaptic knob contain?
Synaptic vesicles contain the neurotransmitter acetylcholine (ACh), which is released to communicate with the muscle fiber.
What role do Ca2+ pumps in the synaptic knob play?
Ca2+ pumps in the plasma membrane of the synaptic knob establish a calcium gradient, with a higher concentration of Ca2+ outside the neuron compared to inside.
What are voltage-gated Ca2+ channels, and what happens when they open?
Voltage-gated Ca2+ channels are located in the membrane of the synaptic knob. When these channels open, Ca2+ flows into the neuron, down its concentration gradient.
What is the motor end plate?
The motor end plate is a specialized region of the sarcolemma (muscle cell membrane) with numerous folds. It contains many acetylcholine (ACh) receptors.
What is the function of ACh receptors on the motor end plate?
The ACh receptors are plasma membrane protein channels that open when acetylcholine binds to them. This allows Na+ ions to enter the muscle cell and K+ ions to exit.
