Musculoskeletal system

What are the three types of muscle tissue?

Skeletal, Cardiac, Smooth.

What is the main function of skeletal muscle?

Voluntary movement (e.g., locomotion, facial expression).

What is the main function of cardiac muscle?

Involuntary blood propulsion in the heart.

What is the main function of smooth muscle?

Involuntary propulsion of substances (e.g., food, urine) in hollow organs.

What is a sarcomere?

Contractile unit of skeletal muscle, between two Z lines, containing actin and myosin.

What triggers muscle contraction at the neuromuscular junction?

Acetylcholine (ACh) binds to sarcolemma receptors, opening Na⁺ channels.

What role does Ca²⁺ play in muscle contraction?

Binds to troponin, exposing actin binding sites for myosin cross bridges.

What is isometric contraction?

Muscle tension increases without movement (e.g., standing, posture).

What is isotonic contraction?

Muscle shortens to produce movement (e.g., walking).

What are the key structural features of cardiac muscle?

Branching, striated, 1-2 nuclei, intercalated discs.

What is the role of the sarcoplasmic reticulum?

Stores and releases Ca²⁺ for muscle contraction.

What are thick and thin filaments made of?

Thick: Myosin; Thin: Actin (with tropomyosin and troponin).

What are the two divisions of the skeletal system?

Axial (skull, spine, ribs) and Appendicular (limbs, girdles).

What are the six functions of bone?

Support, protection, movement, mineral storage, blood cell production, fat storage.

What is the role of red bone marrow?

Produces red/white blood cells and platelets.

What is the role of yellow bone marrow?

Stores fat (chemical energy).

Name the two types of bone tissue.

Compact (dense) and Spongy (porous, contains marrow).

What are the four bone shapes?

Long, Short, Flat, Irregular.

What are osteoblasts and osteoclasts?

A: Osteoblasts form bone; osteoclasts break down bone.

: What is the embryonic skeleton made of?

Hyaline cartilage, later replaced by bone.

What is the hyoid bone’s unique feature?

Does not articulate with any other bone; supports tongue.

Name the three types of joints.

Fibrous (immovable), Cartilaginous (slightly movable), Synovial (freely movable).

What is a synovial joint?

Freely movable joint with synovial fluid for lubrication.

What is a Class 1 lever?

Fulcrum between force and resistance (e.g., nodding head).

What are the three levels of motor control hierarchy?

Strategy (decision), Tactics (planning), Execution (muscle activation).

What are the two major descending spinal pathways?

Lateral (voluntary) and Ventromedial (posture/locomotion).

What is the function of the corticospinal tract?

Conscious control of limb muscles.

What happens in corticospinal lesions?

Impaired hand/arm dexterity, contralateral paralysis.

What is the role of the vestibulospinal tract?

Subconscious balance and head turning.

What does the primary motor cortex (M1, area 4) do?

Executes movements, encodes force/direction.

What is the role of area 6 (PMA and SMA)?

PMA: Sensory-guided movement; SMA: Intentional movement planning.

How does the limbic system aid skill acquisition?

mygdala (emotion), hippocampus (memory), thalamus (relays), hypothalamus (motivation).

What is the basal ganglia’s role in movement?

Selects and initiates willed movements via motor loop.

What are symptoms of Parkinson’s disease?

Bradykinesia, akinesia, rigidity, tremors.

What causes Huntington’s disease symptoms?

Loss of neurons in caudate, putamen, globus pallidus (less inhibition).

: What is the cerebellum’s role in movement?

Coordinates muscle sequences, calibrates smooth movements.

What is a motor unit?

One motor neuron and all muscle fibers it controls.

What is the motor unit ratio for eye muscles?

1:1 (high precision).

How is muscle force increased?

Recruit more motor units (amplitude) or increase firing rate (frequency).

What is proprioception?

Sense of body position and strength of effort.

What are the main sensory inputs for proprioception?

Vestibular organs, visual system, proprioceptors (muscle/joint receptors).

What is Henneman’s size principle?

Small, fatigue-resistant motor units recruited first, then larger units.

What does the muscle spindle sense?

Changes in muscle length.

What is the role of gamma motor neurons?

Maintain muscle spindle sensitivity by keeping intrafusal fibers taut.

What does the Golgi tendon organ sense?

Changes in muscle tension.

Where are Golgi tendon organs located?

In tendons, in series with muscle fibers

Name the four types of tactile mechanoreceptors.

Merkel disks, Meissner corpuscles, Ruffini cylinders, Pacinian corpuscles.

Which mechanoreceptors are slow-adapting?

Merkel disks, Ruffini cylinders (respond during stimulus).

Which mechanoreceptors are rapidly adapting?

Meissner corpuscles, Pacinian corpuscles (respond at stimulus onset/end).

What is the vestibulo-ocular system’s role?

Coordinates eye movements with head position to stabilize gaze.

What causes motion sickness?

Sensory mismatch between eyes (stillness) and inner ear (motion).

What is a simple reflex example?

Stretch reflex (muscle spindle → spinal cord → muscle contraction).

What is decussation in complex reflexes?

Sensory information crosses to opposite brain side (right body to left cortex).

What frequency range do mechanoreceptors respond to?

0.3 Hz (slow pressure) to 500 Hz (rapid vibration).

What is the difference between regeneration and healing?

Regeneration restores normal structure (intact scaffold); healing forms scars (damaged scaffold).

What are labile cells?

High turnover, strong regeneration (e.g., epithelia, hematopoietic cells).

What are stable cells?

Non-proliferative but regenerate post-injury (e.g., hepatocytes, osteoblasts).

What are permanent cells?

Cannot regenerate (e.g., neurons, cardiac/skeletal muscle).

What are the three phases of tendon healing?

Inflammation (0–7 days), Repair (3–60 days), Organisation (28–180 days).

When is a tendon weakest during healing?

7–10 days.

When does a tendon regain most strength?

21–28 days.

What is the effect of early mobilisation on tendon healing?

Increases ROM, may reduce repair strength if overstressed.

What is the effect of immobilisation on tendon healing?

Increases tendon strength, reduces ROM.

Why are NSAIDs problematic for healing?

Block inflammation (prostaglandins), delaying subsequent healing phases.

What is the POLICE strategy?

Protection, Optimal Loading, Ice, Compression, Elevation.

What are common fracture types in immature skeletons?

Buckle/Torus, Plastic deformation, Greenstick.

What is fibronectin’s role in tendon healing?

Forms scaffolding for collagen synthesis during inflammation.

What collagen type dominates early vs. late tendon repair?

Type 3 (early, random), Type 1 (late, force-aligned).