Podcast
Questions and Answers
What percentage of body weight does skeletal muscle constitute?
What percentage of body weight does skeletal muscle constitute?
Which type of muscle is under voluntary control?
Which type of muscle is under voluntary control?
What is the connective tissue sheath surrounding each skeletal muscle called?
What is the connective tissue sheath surrounding each skeletal muscle called?
Smooth muscle is primarily found in which of the following?
Smooth muscle is primarily found in which of the following?
Signup and view all the answers
Which of the following statements about cardiac muscle is TRUE?
Which of the following statements about cardiac muscle is TRUE?
Signup and view all the answers
What term is used for groups of muscle cells within a skeletal muscle?
What term is used for groups of muscle cells within a skeletal muscle?
Signup and view all the answers
Which muscle type can be found in the heart?
Which muscle type can be found in the heart?
Signup and view all the answers
The presence of transverse bands, or striations, is a characteristic of which muscle type?
The presence of transverse bands, or striations, is a characteristic of which muscle type?
Signup and view all the answers
What is the connective tissue covering that surrounds each fascicle?
What is the connective tissue covering that surrounds each fascicle?
Signup and view all the answers
What does the endomysium do?
What does the endomysium do?
Signup and view all the answers
Which of the following is NOT a functional property of muscles?
Which of the following is NOT a functional property of muscles?
Signup and view all the answers
What role does the perimysium serve in muscles?
What role does the perimysium serve in muscles?
Signup and view all the answers
What is the primary function of contractility in muscle tissue?
What is the primary function of contractility in muscle tissue?
Signup and view all the answers
The connective tissue layers in muscles merge at their ends to form which structure?
The connective tissue layers in muscles merge at their ends to form which structure?
Signup and view all the answers
What is excitability in the context of muscle function?
What is excitability in the context of muscle function?
Signup and view all the answers
Which layer of connective tissue surrounds each muscle fiber?
Which layer of connective tissue surrounds each muscle fiber?
Signup and view all the answers
What initiates the opening of Na+ channels in the sarcolemma?
What initiates the opening of Na+ channels in the sarcolemma?
Signup and view all the answers
What role does Ca2+ play in muscle contraction?
What role does Ca2+ play in muscle contraction?
Signup and view all the answers
What maintains the muscle contraction cycle as long as it is present?
What maintains the muscle contraction cycle as long as it is present?
Signup and view all the answers
Where does the action potential travel after it moves down the sarcolemma?
Where does the action potential travel after it moves down the sarcolemma?
Signup and view all the answers
What is primarily responsible for providing energy for muscle contractions?
What is primarily responsible for providing energy for muscle contractions?
Signup and view all the answers
Which of the following best describes the process when myosin heads bend?
Which of the following best describes the process when myosin heads bend?
Signup and view all the answers
What occurs at the neuromuscular junction?
What occurs at the neuromuscular junction?
Signup and view all the answers
What is the role of synaptic vesicles in muscle contraction?
What is the role of synaptic vesicles in muscle contraction?
Signup and view all the answers
What is a synapse?
What is a synapse?
Signup and view all the answers
What characterizes the inside of the cell membrane compared to the outside?
What characterizes the inside of the cell membrane compared to the outside?
Signup and view all the answers
What encompasses a motor unit?
What encompasses a motor unit?
Signup and view all the answers
What is the synaptic cleft?
What is the synaptic cleft?
Signup and view all the answers
What is the role of ion channels in the cell membrane?
What is the role of ion channels in the cell membrane?
Signup and view all the answers
What type of channel allows the slow leak of ions down their concentration gradient?
What type of channel allows the slow leak of ions down their concentration gradient?
Signup and view all the answers
What is acetylcholine's primary role?
What is acetylcholine's primary role?
Signup and view all the answers
Why is the phospholipid bilayer described as impermeable to ions?
Why is the phospholipid bilayer described as impermeable to ions?
Signup and view all the answers
Study Notes
Types of Muscles
- Skeletal muscles are attached to bones, are striated, and are voluntarily controlled
- Cardiac muscles are located in the heart, are striated, and are involuntarily controlled
- Smooth muscles are located in blood vessels and hollow organs, are non-striated, and are involuntarily controlled
Whole Skeletal Muscle Anatomy
- Skeletal muscle (striated muscle) comprises about 40% of body weight
- Many skeletal muscles attach to the skeletal system, or sometimes to skin or connective tissue
- Skeletal muscle is composed of muscle, nerve, and connective tissue
Connective Tissue Coverings
- Each skeletal muscle is encased in a connective tissue sheath called the epimysium
- Muscle bundles are called fascicles and are surrounded by the perimysium
- Individual muscle fibers (cells) are surrounded by endomysium
- The connective tissues blend to form tendons that attach muscles to bone
Skeletal Muscle Fiber Anatomy
- Skeletal muscle fibers range in size from 1 mm to 4 cm in length
- Muscle fibers have multiple nuclei located at their periphery
- Alternating light and dark bands give muscle fibers a striated appearance
- Muscles enlarge due to fiber size increases, not an increase in number of fibers
Electrical Component Structure
- The sarcolemma (cell membrane) contains transverse tubules (T tubules) that extend into the center of the muscle fiber
- T tubules are associated with enlarged portions of the smooth endoplasmic reticulum (sarcoplasmic reticulum), called terminal cisternae
- The terminal cisternae and associated T tubules form a triad
- The sarcoplasmic reticulum's high Ca2+ concentration plays a crucial role in muscle contraction
Mechanical Component Structure
- Myofibrils, bundles of actin and myosin myofilaments, make up skeletal muscle
- Actin (thin filaments), and myosin (thick filaments) are arranged in repeating units called sarcomeres
- Sarcomeres provide the mechanical basis for muscle contraction
- Z disks are protein fiber networks that anchor actin myofilaments and separate sarcomeres
- Actin and myosin myofilaments slide past each other which shortens the sarcomeres causing the muscle to contract
Neuromuscular Junction
- A motor neuron stimulates muscle cells at a neuromuscular junction, a synapse
- A synapse is a junction between a nerve cell (neuron) and another cell (muscle, gland)
- A motor unit is a group of muscle fibers stimulated by a single motor neuron
- The presynaptic terminal is the axon terminal end
- The postsynaptic membrane is the sarcolemma (muscle fiber membrane)
- Neurotransmitters stimulate/inhibit postsynaptic cells: acetylcholine stimulates skeletal muscles
Action Potentials
- Resting membrane potential is the resting state of a cell where the inside is negative compared to the outside
- Action potentials are rapid changes in membrane charge
- The entry of Na+ causes the inside of the cell to become more positive (depolarization)
- The exit of K+ returns the cell to its resting state (repolarization)
- An action potential triggers the release of acetylcholine at the neuromuscular junction, stimulating muscle contraction
Muscle Contraction
- Sliding filaments model: actin and myosin filaments slide past each other, shortening the sarcomere
- Muscle action potential triggered by acetylcholine released at neuromuscular junction,
- Ca++ released from sarcoplasmic reticulum bind to troponin to expose myosin-binding sites on actin
- ATP hydrolysis provides energy for myosin head power stroke and subsequent cross-bridge cycle
Muscle Relaxation
- Acetylcholine is no longer released at the neuromuscular junction
- Ca++ is actively transported back into the sarcoplasmic reticulum
- Tropomyosin blocks myosin-binding sites on actin
- The muscle relaxes
Muscle Twitch
- A muscle twitch is a single contraction in response to a stimulus
- Phases include latent phase, contraction phase, and relaxation phase
Types of Contractions
- Isometric contractions: tension increase, no length change
- Isotonic contractions: tension increase, length change (muscle shortens or lengthens)
Muscle Tone
- Muscle tone is a constant tension maintained by muscles over time, which is important for posture, stability, etc
Types of Skeletal Muscle Fibers
- Slow-twitch fibers are fatigue-resistant, use aerobic respiration, are dark in color, and used for endurance activities
- Fast-twitch fibers tire quickly, use anaerobic respiration, are light in color, used for quick bursts of activity
Muscle Fatigue
- Fatigue is a temporary state of reduced work capacity
- Mechanisms include acidosis, ATP depletion, oxidative stress, and local inflammation
Muscle Soreness
- Muscle soreness often follows intense exercise, lasting several days
- It's a result of inflammatory chemicals affecting muscle fibers
Muscle Exercises
- Exercise regimens are important in tissue repair
- Oxygen deficit occurs when the body starts exercising and breathes heavily
- Excess postexercise oxygen consumption (EPOC): the time required for breathing to return to a pre-exercise rate
Muscle Names:
- Muscles are named based on location, size, shape, orientation, origin, insertion, and function.
- Examples of muscle names and functions are given.
Muscles of Mastication
- Muscles involved in chewing: temporalis, masseter, and pterygoids
Thoracic Muscles
- External intercostals elevate ribs, important for breathing
- Internal intercostals depress ribs, crucial during forced breathing
- Diaphragm moves during breathing
Abdominal Wall Muscles
- Rectus abdominis, external abdominal oblique, and internal abdominal oblique compress the abdomen
- Important in posture and movement
Pelvic Diaphragm Muscles
- Located in the pelvic floor
Upper Scapular Muscles and Limbs
- Trapezius, pectoralis major, serratus anterior, and deltoid are muscles involved in shoulder and upper back movements.
Upper Limb Muscles
- Triceps brachii, biceps brachii, brachialis, latissimus dorsi
Muscles of the Hips and Thighs
- Iliopsoas, gluteus maximus, gluteus medius, and muscles of the upper leg (rectus femoris, vastus lateralis, vastus medialis)
Muscles of the Lower Leg
- Tibialis anterior, gastrocnemius, and soleus are lower leg muscles essential for movement and stability.
Muscle Excitation
- Details on muscle excitation and how energy from ATP powers this process are provided.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
