Muscle and Bone Function Quiz

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Questions and Answers

What physiological change contributes to the increased risk of falls and fractures in older adults?

Enhanced ATP production in muscle cells

Increased muscle fiber density

Replacement of lean body mass with fat (correct)

Improved circulation to muscle tissues

What is a significant factor causing muscle cramps during exercise or at night?

Increased blood flow to the muscles

Shortening of the muscle under tension (correct)

Enhanced neural activation of motor units

Lack of muscle relaxation

Which of the following statements is true regarding Golgi tendon organs?

They have no effect on muscle injury prevention.

They enhance muscle contraction during high intensity training.

They increase the firing rate of motor neurons in all training phases.

They monitor and inhibit excessive muscle contractions. (correct)

Which age-related factor affects muscle healing and recovery?

Reduced circulation Signup and view all the answers

What is the primary reason older adults experience fatigue more quickly during physical activity?

Decreased muscle fiber size and organization Signup and view all the answers

What type of joint movement describes lifting the toes upward?

Dorsiflexion Signup and view all the answers

Which of the following describes the characteristic of a sphincter muscle?

Decreases the size of an opening Signup and view all the answers

Which term describes a muscle that flexes the elbow joint?

Flexor Signup and view all the answers

What is the primary structural unit of muscle cells that allows for contraction?

Myofibril Signup and view all the answers

What is the role of tropomyosin in muscle contraction?

It inhibits the binding of myosin heads to actin in the absence of calcium Signup and view all the answers

What physiological mechanism is responsible for stopping a muscle cramp when stretched?

Inhibition from the golgi tendon organ Signup and view all the answers

What common type of hernia occurs primarily in the inguinal area?

Inguinal hernia Signup and view all the answers

Which statement best describes convulsions?

They are violent and involuntary contractions of muscle groups due to stimulated motor neurons. Signup and view all the answers

Which characteristic differentiates muscles that are named according to their origin and insertion?

They are named based on their attachment points on the skeleton. Signup and view all the answers

Which of the following statements about T tubules is correct?

They are involved in the conduction of action potentials. Signup and view all the answers

What is a primary characteristic of fibrillation in muscle tissues?

Uncoordinated contractions of individual muscle fibers Signup and view all the answers

Which of the following is a symptom commonly associated with Myasthenia Gravis?

Drooping eyelids and easy fatigue Signup and view all the answers

What population is most commonly affected by Myasthenia Gravis?

Women aged 20-50 years Signup and view all the answers

What role do muscles primarily play in the movement of bones across joints?

Muscles pull and act as levers. Signup and view all the answers

Which of the following best describes the term 'insertion' in muscle anatomy?

The distal point of attachment. Signup and view all the answers

Which of the following types of movements decreases the angle between body parts?

Flexion Signup and view all the answers

In which movement does the sole of the foot turn inward?

Inversion Signup and view all the answers

What is the term for the muscle that acts as the primary mover during an action?

Agonist Signup and view all the answers

Which type of joint movement involves a circular motion combining various movements?

Circumduction Signup and view all the answers

Which muscles must work in opposition to create movement?

Opposing pairs and functional groups Signup and view all the answers

What is hyperextension in the context of joint movement?

Extension beyond the normal range of motion Signup and view all the answers

What is the primary function of muscle tone?

To maintain the body in a state of readiness for activity. Signup and view all the answers

Which statement correctly describes hypotonia?

It is characterized by decreased or lost muscle tone. Signup and view all the answers

What triggers the involuntary contractions associated with muscle tone?

Activation of stretch receptors in muscles and tendons. Signup and view all the answers

What leads to muscle atrophy?

Disuse of muscles or neurogenic conditions. Signup and view all the answers

Which characteristic is true about smooth muscle compared to skeletal muscle?

Smooth muscle has a lower concentration of actin and myosin. Signup and view all the answers

What causes muscle mass and strength to decline as one ages?

Reduced effectiveness of the nervous system to stimulate muscles. Signup and view all the answers

Which factor contributes to prolonged contraction in smooth muscle?

Poorly developed sarcoplasmic reticulum and slow calcium transport. Signup and view all the answers

What happens to muscle fibers during disuse atrophy?

Muscle fibers start to atrophy within a few days. Signup and view all the answers

Study Notes

Bones and Muscles

Bones function as levers and fulcrums in movement.
Most skeletal muscles are bundled, attaching to two bones across a joint.
Muscles pull, not push, requiring coordinated muscle groups for movement.
Muscle attachments include the origin (proximal, less mobile) and insertion (distal, more mobile).
Intramuscular injections are often administered in muscles with thick bellies for slower absorption.

Muscle Function Principles

Muscle movement necessitates coordination of several muscles.
Opposing muscle pairs work together: prime movers (agonists), synergists (including fixators), and antagonists.

Types of Body Movements

Flexion/extension: Decreasing/increasing the angle between bones; hyperextension exceeds anatomical position.
Supination/pronation: Rotating outward/inward (e.g., forearm).
Adduction/abduction: Movement toward/away from the body's midline.
Levator/depressor: Upward/downward movement.
Rotation/circumduction: Rotation occurs in hips and shoulders; circumduction involves circular movement combining flexion/extension and abduction/adduction.
Eversion/inversion: Turning the sole outward/inward.
Dorsiflexion/plantarflexion: Toes up/down.
Other movements include tensing (increasing rigidity) and sphincter actions (decreasing opening size).

Naming Skeletal Muscles

Muscle names indicate fiber direction (rectus, transverse, oblique), location, size, origin/insertion, number of origins, shape, and action.

Hernia

Weaknesses in the body wall can cause hernias, where visceral organs protrude through openings.
Pressure on abdominal viscera forces peritoneum and intestine through weak spots (e.g., heavy lifting).
Inguinal hernias are common; diaphragmatic and umbilical hernias also occur.

Muscle Cell Anatomy

T-tubules: Infoldings of the sarcolemma extending into the muscle cell, surrounding the sarcoplasmic reticulum (SR), facilitating action potential transmission.
Myofibrils: Fill most of the muscle cell, containing overlapping filaments (in striated muscle), surrounded by the SR and T-tubules.

Myofibril Components

Thick filaments (myosin): Hundreds of myosin molecules shaped like golf clubs, with heads projecting outward.
Thin filaments (actin, troponin, tropomyosin): G-actin contains active sites; tropomyosin has a calcium-binding troponin molecule attached.

Muscle Contraction and Relaxation

In the absence of Ca²⁺, tropomyosin prevents myosin-actin binding.
Rising Ca²⁺ levels bind to troponin, shifting tropomyosin and initiating contraction.
Relaxation occurs when Ca²⁺ levels decrease, restoring tropomyosin's blocking position.

Kinds of Muscle Contraction

Isotonic: Muscle length changes (concentric – shortening; eccentric – lengthening).
Isometric: Muscle length remains constant (tension increases).
Tetanus: Sustained contraction due to rapid stimulation.

Muscle Tone

Muscle tone is maintained by alternating motor unit activation.
Hypotonia is decreased muscle tone; atrophy is muscle wasting.
Hypertrophy is increased muscle fiber diameter.
Muscle tone loss occurs rapidly with disuse or denervation, potentially leading to irreversible degeneration.

Smooth Muscle

Involuntary muscle controlled by the autonomic nervous system.
Nonstriated, lacking organized sarcomeres.
Actin and myosin are present but irregularly arranged.
Smooth muscle contractions are slow, prolonged, and stimulated by neurotransmitters, hormones, and local chemical changes.

Smooth Muscle vs. Skeletal Muscle Characteristics

Smooth muscle has less actin and myosin, fewer mitochondria, and slower contractions.
Lacks T-tubules and has poorly developed SR, leading to slower Ca²⁺ transport and longer contractions.

Effects of Aging on Muscles

Muscle strength and mass peak in the 20s and decline significantly with age.
Lean body mass is replaced by fat, reducing strength and endurance.
Reduced circulation slows muscle healing.
Motor units have fewer muscle fibers, decreasing acetylcholine production.

Abnormal Muscle Contractions

Spasm: Brief, involuntary muscle twitch due to chemical imbalance.
Cramp: Sustained, painful contraction, often occurring when the muscle is shortened (little tendon pull).
Convulsions: Violent, involuntary contractions of muscle groups, a nervous, not muscular disorder.
Fibrillation: Uncoordinated contraction of individual muscle fibers.

Golgi Tendon Organs

Inhibit muscle contraction to prevent injury.
Stretching activates Golgi tendon organs, relieving cramps.

Myasthenia Gravis

Weakness in skeletal muscles, especially in the face and neck.
Immune system attacks acetylcholine receptors, impairing muscle contraction.
Symptoms include fatigue, weakness, drooping eyelids, and double vision.

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Description

Test your knowledge on the functions and principles of muscles and bones. This quiz covers topics including muscle coordination, body movements, and the mechanics of skeletal muscles. Perfect for students studying anatomy or physiology.