HBS Notes

Bones and Their Functions

  • Functions of Bones:

    • Produce blood cells.

    • Enable movement.

    • Store minerals such as calcium.

    • Provide support and protection for organs.

Muscle Contraction Mechanism

ATP Cycle

  • ATP: Adenosine triphosphate; produced by mitochondria.

    • Structure:

      • Three phosphate groups.

      • One sugar (ribose).

      • One adenine.

  • Process:

    • ATP undergoes hydrolysis to become ADP (adenosine diphosphate) releasing energy.

    • Hydrolysis requires water; dehydration synthesis is the removal of water.

  • Essential components for muscle contraction:

    • ATP, water, and ions (especially calcium).

Sliding Filament Theory

  • Actin and Myosin:

    • Actin: thin filament.

    • Myosin: thick filament.

  • Myosin head pulls actin to contract muscle.

Rigor Mortis

  • Occurs due to the absence of ATP, leading to stiffness in muscles.

Muscle Contraction Steps

  1. Detachment: ATP binds to myosin, causing detachment from actin.

  2. Hydrolysis: ATP splits into ADP, reorienting myosin to a ready position.

  3. Cross Bridge Formation: Myosin head attaches to actin, forming a cross bridge.

  4. Power Stroke: Myosin pulls actin, losing ADP in the process.

Types of Muscle Tissue

  1. Skeletal Muscle:

    • Characteristics: Striated, tubular, voluntary.

    • Function: Attached to the skeleton, facilitating movement.

  2. Smooth Muscle:

    • Characteristics: Non-striated, spindle-shaped, involuntary.

    • Location: Walls of internal organs.

  3. Cardiac Muscle:

    • Characteristics: Striated, branched, involuntary.

    • Location: Walls of the heart.

Muscle Insertion and Origin

  • Muscle Insertion vs. Origin:

    • Insertion moves; origin remains stationary.

  • Notable Muscles:

    • Pectoralis Minor: Attaches to ribs 3-5, rotates shoulder forward.

    • Pectoralis Major:

      • Abdominal head: ribs 5-7, helps pull arms down (as in a volleyball strike).

      • Sternal head: ribs 1-5, adducts arm across the chest (as in a sidemen pitch).

      • Clavicular head: Facilitates underarm motion (like bowling).

    • Brachialis: Assists with flexion at the elbow.

    • Triceps Medial Head: Primary extensors of the arm.

    • Intercostal Muscles: Assist with respiration.

    • Temporalis: Origin at temporal bone, inserts at mandible.

    • Orbicularis Oculi: Controls movements of the eyebrows.

Quiz Review

  • Causes of Muscle Cramps:

    • Lack of water, calcium, or ATP.

  • Rigor Mortis: Stiffening of muscles due to ATP depletion.

  • Six Muscle Rules:

    • Each muscle has at least two attachments and crosses at least one joint.

    • Muscles always function by pulling.

    • Insertion moves while origin remains fixed.

    • Flexors decrease joint angle; extensors increase it.

    • Muscles work in opposing pairs (like quadriceps and hamstrings).

    • Muscle striations indicate direction of pull and attachment points.