Wk Lec 1 Muscle cells I

Introduction to Muscle Cells

• Course: BIOM2011 - Integrative Cell and Tissue Biology

• Lecture by Professor Bradley Launikonis

• Focus on muscle cell biology and physiology.

Historical Context: Sidney Ringer’s Contribution

• Sidney Ringer (1880-1883): Discovered that frog hearts perfused with London city water lasted longer than those with distilled water.

  • Hypothesis: Calcium ions played a crucial role.

• Composition of Lactated Ringer's Solution:

  • 130 mEq of sodium ion (Na+) = 130 mmol/L

  • 109 mEq of chloride ion (Cl-) = 109 mmol/L

  • 28 mEq of lactate = 28 mmol/L

  • 4 mEq of potassium ion (K+) = 4 mmol/L

  • 3 mEq of calcium ion (Ca2+) = 1.5 mmol/L

Hypertension and Cardiac Physiology

• Importance of understanding the cardiovascular system for hypertension treatment.

  • Merely knowing the gross anatomy is insufficient; understanding functional mechanisms is crucial.

  • Verapamil: A calcium channel blocker used in treatment; requires understanding of its mechanism of action for effective use.

Muscle Fatigue

• Factors contributing to fatigue in skeletal muscle.

  • Exercise-induced lactate accumulation impacts muscle performance.

Lecture Plan

1. The Heart

   • Electrical and mechanical activity.

   • Excitation-contraction coupling.

2. Skeletal Muscle

   • Electrical activity and calcium regulation.

   • Excitation-contraction coupling.

3. Revision and Exam Preparation

Assumed Knowledge for Cardiovascular Physiology

• Understanding the circuits of systemic and pulmonary blood flow.

• Gross structure of the heart:

  • Chambers and valves; pathways of blood movement.

• Distribution and pressure changes in the cardiovascular system (CVS).

Cardiac Output

• Cardiac output (CO) increases dramatically during exercise (up to 20-30 L/min).

• At rest:

  • CO = heart rate (HR) x stroke volume (SV)

  • Example: HR = 70 beats/min, SV = 70 mL/beat = about 5 L/min total.

Ion Channels, Pumps, and Exchangers

• Composition of lactated Ringer's solution re-emphasized for relevance in muscle physiology.

Ion Channels

• Types of ion channels:

  • Voltage-dependent channels: Selectively allow specific ions through based on electrical and chemical gradients.

  • Pumps: ATP-dependent proteins that move ions against gradients.

  • Exchangers: Move different ion species, affecting chemical/electrical gradients.

Types of Ion Channels in the Heart

1. Ca2+ Channels

   • L-type and T-type.

2. K+ Channels

   • At least 15 varieties.

3. Na+ Channels

   • One major type identified.

Voltage-Activated Ion Channels

• Ion channels have three states:

  • Reprimed: Ready to activate.

  • Activated: Open and allowing current.

  • Inactivated: Closed to current flow, even under depolarization.

Role of Pumps in the Cardiovascular System

• Key examples include Na+-K+ pump and Ca2+ pump.

  • These use ATP energy to maintain ion gradients essential for cardiovascular stability.

Na+-Ca2+ Exchanger Mechanism

• Allows the exchange of sodium (Na+) to move calcium (Ca2+) ions against their gradient without ATP.

• Important for regulating intracellular calcium levels.

Conclusion

• Next Lecture: Examination of the heart's electrical activity.