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Questions and Answers
What indicates that muscle control develops in a structured manner?
What is the effect of regular exercise on the muscular system?
What occurs to muscles as a person ages?
What happens to muscles when there is a lack of exercise?
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How does extremely vigorous exercise affect muscles?
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Which muscle group is primarily responsible for hip movement?
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What is the primary function of the superficial muscles of the leg?
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Which muscles are located on the anterior surface of the body?
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Which muscle group is most active during knee flexion?
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Which of the following correctly identifies a type of muscle in the thigh?
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What is a primary role of the pelvic muscles?
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Which of these muscles would primarily assist in extending the hip?
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Which of the following muscles is located on the posterior surface of the body?
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Study Notes
Muscular System
- The muscular system consists of skeletal, smooth, and cardiac muscle tissues. These are all responsible for body movements.
Skeletal Muscle Tissue
- Attached to bones and skin
- Responsible for voluntary movements, such as walking and talking
- Contain striations, which give them a striped appearance
Skeletal Muscle Organization
- Muscle fascicles: Bundles of muscle fibers (cells)
- Muscle fibers: Long, cylindrical cells with multiple nuclei
- Myofibrils: Contractile units within muscle fibers, made up of myofilaments
- Myofilaments: Thin (actin) and thick (myosin) protein filaments responsible for muscle contraction
Muscle Attachments
- Origin: Attachment site of a muscle that remains stationary during contraction.
- Insertion: The structure that moves during muscle contraction, usually a bone, that moves.
Smooth Muscle Tissue
- Found in the walls of hollow organs, such as the stomach and blood vessels
- Responsible for involuntary movements, such as digestion and blood pressure regulation
- Lack striations, contributing to their smooth appearance
Cardiac Muscle Tissue
- Found only in the heart
- Responsible for pumping blood throughout the body
- Contains striations, similar to skeletal muscle.
- Involuntary, and under the control of the nervous system.
Muscle Functions
- Movement: Skeleton muscles facilitate movement of the body, with skeletal muscles responsible for most of the movement.
- Maintaining posture: Skeletal muscles continuously contract to help maintain posture and stabilize joints.
- Stabilizing joints: Skeletal muscles support and stabilize joints, preventing dislocation and injury. Muscle tension helps maintain joint integrity.
- Generating heat: Muscle contractions generate heat which helps regulate body temperature
Muscle Fiber Contraction
- Sliding filament theory: Muscle contraction occurs when thin (actin) filaments slide past thick (myosin) filaments.
- Role of calcium (Ca2+): Calcium ions bind to troponin, which initiates the uncovering of binding sites on actin, allowing myosin to bind and pull.
Muscle Contraction & Relaxation
- Neurotransmitter (acetylcholine) at neuromuscular junction: The nerve impulse stimulates the release of acetylcholine, a neurotransmitter, at the neuromuscular junction.
- Action potential in muscle fiber: Acetylcholine binds to receptors, triggering an action potential in the muscle fibers.
- Calcium (Ca2+) release: The action potential travels through the muscle fiber, causing the release of calcium ions (Ca2+) from the sarcoplasmic reticulum.
- Sliding filament mechanism: Calcium ions bind to troponin, exposing myosin-binding sites on actin. Myosin heads bind to actin, initiating the sliding of filaments.
- Muscle relaxation: When the nerve impulse stops, acetylcholine is broken down, Ca2+ is pumped back, and the myosin-binding sites are covered again, ending muscle contraction.
Muscle Energy Sources
- ATP: Directly fuels muscle contraction.
- Creatine phosphate: Short-term reserve of energy that can be used to quickly regenerate ATP.
- Glycogen: Stored glucose that can be used to produce ATP through anaerobic glycolysis.
- Aerobic respiration: Primary energy source for sustained muscle activity, requiring oxygen to produce ATP.
Muscle Fatigue and Oxygen Debt
- Muscle fatigue: The inability of a muscle to contract forcefully after prolonged or strenuous activity.
- Causes: Accumulation of lactic acid, depletion of ATP, and disruption of electrolyte balance.
- Oxygen debt: The amount of oxygen that is needed to restore muscle cells to their pre-exercise state after strenuous activity
Types of Muscle Contractions
- Isometric contractions: Muscle tension increases, but muscle length stays the same. Example: Holding a heavy object.
- Isotonic contractions: Muscle tension remains constant, but muscle length changes. Example: Lifting a weight.
- Concentric contractions: Muscle shortens as it contracts. Example: Curling a dumbbell.
- Eccentric contractions: Muscle lengthens as it contracts. Example: Lowering a dumbbell.
Types of Muscle Fibers
- Slow-twitch (type I) fibers: Red muscle fibers that are fatigue-resistant, use aerobic metabolism and are designed for endurance activities.
- Fast-twitch (type IIa) fibers: Pink muscle fibers that are fast-twitch and fatigue resistant, use both aerobic and anaerobic metabolism.
- Fast-twitch (type IIb) fibers: White muscle fibers that are fast, powerful, and easily fatiguable, use anaerobic metabolism.
Factors Affecting Muscle Tension
- Number of muscle fibers: More muscle fibers involved, the stronger the contraction.
- Size of muscle fibers: Larger muscle fibers generate more force.
- Frequency of stimulation: Increased frequency of stimulation results in stronger contractions.
- Length-tension relationship: Muscle fibers contract most forcefully at their optimal length.
Muscle Movements
- Flexion: Decreases the angle between two bones.
- Extension: Increases the angle between two bones.
- Abduction: Movement away from the midline of the body.
- Adduction: Movement toward the midline of the body.
- Rotation: Turning a bone around its longitudinal axis.
- Circumduction: Movement in a circular motion.
- Pronation: Turning the palm of the hand downward.
- Supination: Turning the palm of the hand upward.
- Inversion: Turning the sole of the foot inward.
- Eversion: Turning the sole of the foot outward.
- Dorsiflexion: Bending the foot upward.
- Plantar flexion: Bending the foot downward.
Muscle Naming Criteria
- Location: Based on the region of the body where the muscle is located. Example: Pectoralis muscle, located in the chest.
- Size (large, small, long, short) Examples: Gluteus maximus, a large muscle in the buttocks, Sartorius, a long muscle in the thigh.
- Shape: Based on the muscle's shape. Examples: Deltoid, triangular shaped muscle in the shoulder, Trapezius, trapezoid shaped muscle in the back.
- Number of Origins: Based on the number of attachment points that the muscle has. Example: Biceps brachii, has two heads, or origins
- Direction of Fibers: Based on the direction of muscle fibers, such as rectus for straight. Example: Rectus abdominis, a straight muscle in the abdomen.
- Action: Based on the primary movement that the muscle performs. Example: Flexor digitorum superficialis, a muscle that flexes the fingers.
Skeletal Muscle Groups
- Head and neck: Muscles responsible for facial expressions, chewing, and head movement.
- **Trunk: ** Muscles responsible for movements of the spine, ribs, and abdomen.
- Upper limb: Muscles responsible for movements of the shoulder, arm, forearm, and hand.
- Lower limb: Muscles responsible for movements of the hip, leg, and foot.
Muscles of the Head and Neck
- Facial muscles: Control facial expressions. Examples: Frontalis, Orbicularis oculi, Zygomaticus major.
- Chewing muscles: Control the movement of the jaw.
- Neck muscles: Control head movements, posture, and swallowing.
Muscles of the Trunk
- Back muscles: Responsible for posture, extension, and lateral flexion of the spine. Examples: Trapezius, Latissimus dorsi, Erector spinae.
- Chest muscles: Responsible for breathing, pushing, and lifting. Examples: Pectoralis major, Pectoralis minor, Intercostal muscles.
- Abdominal muscles: Responsible for trunk flexion, rotation, and maintaining the abdominal cavity. Example: Rectus abdominis, External oblique, Internal oblique.
Muscles of the Upper Limb
- Shoulder: Muscles responsible for movement of the shoulder joint. Examples: Deltoid, Supraspinatus, Infraspinatus, Teres minor, Subscapularis.
- **Arm: ** Muscles responsible for movements of the elbow and forearm. Examples: Biceps brachii, Triceps brachii, Brachialis.
- Forearm: Muscles responsible for movements of the wrist and hand. Example: Flexor carpi radialis, Extensor carpi radialis, Flexor digitorum superficialis.
- Hand: Muscles responsible for fine motor movements of the fingers.
Muscles of the Lower Limb
- Hip: Muscles responsible for movement of the hip joint. Examples: Gluteus maximus, Gluteus medius, Gluteus minimus, Iliopsoas, Adductor muscles.
- Thigh: Muscles responsible for movements of the knee joint. Examples: Quadriceps femoris (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius), Hamstring muscles (biceps femoris, semitendinosus, semimembranosus).
- Leg: Muscles responsible for movements of the ankle and foot. Examples: Gastrocnemius, Soleus, Tibialis anterior.
Developmental Aspects of the Muscular System
- Muscle development: Muscle control progresses in a superior to inferior and proximal to distal direction.
- Peak muscle development: Muscle growth peaks during mid-adolescence.
- Muscle atrophy: Muscles decrease in size and strength with lack of exercise
- Muscle hypertrophy: Muscles increase in size and strength with vigorous exercise.
- Aging: Muscles lose mass and strength with age. Exercise helps retain muscle mass and strength.
Muscle Disorders
- Muscle strain
- Muscle cramps
- Myalgia
- Tendinitis
- Fibromyalgia
- Muscular dystrophy
- **Amyotrophic lateral sclerosis (ALS) **
- Botulism
- Tetanus
- Myasthenia gravis
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Description
This quiz covers the essential components of the muscular system, including skeletal, smooth, and cardiac muscle tissues. Learn about the organization of skeletal muscle and the significance of muscle attachments in body movement. Test your understanding of muscle structure and function.
