1. Muscles and Excitable tissues Sharmeen Asad

2. Muscles Muscles: Muscles are special type of tissues of human body that possess the ability of contraction and relaxation. They can contract actively thus producing force for different body movements. Types of Muscle Skeletal Muscle Striated, under voluntary control, found attached to skeleton, produce major movements of body parts. Smooth Muscle Non striated, not under voluntary control, found in soft organs of body, responsible for processes like digestion of food etc. Cardiac Muscle Striated, involuntary, present exclusively in heart, responsible for pumping activity of heart, very strong and tough

4. Functions of muscles MOVEMENTS OF BODY PARTS: Skeletal muscles are responsible for all voluntary movements of human body parts. They provide the force by contracting actively at the expense of energy. In other words, muscles are motors of body where chemical energy of food is converted into mechanical work. STABILITY AND POSTURE: Skeletal muscles stabilize human skeleton and give a proper posture to human beings. Some joints of human body are weak and they require the support of muscular system to achieve stability. Skeletal muscles are very important for such joints. HEAT PRODUCTION: A large share of body’s energy is used by muscular system. As a result of high metabolic rate, muscles produce great amount of heat in the body. Heat produced by muscles is very important in cold climates. CIRCULATION: Cardiac muscles provide the main force for circulation of blood throughout human body. The regular pumping of heat keeps the blood in motion and nutrients are readily available to every tissue of human body. HELP IN DIGESTION: Smooth muscles of organs like stomach and intestine help the digestive system in the process of digestion of food.

5. Excitable Tissues Excitable Tissues are the cells with the capability to generate action potentials, mostly are the nerve and muscle cells. Excitation: – Process of generating action potential. Components of Excitation: – Chemical – Physicochemical (Ion permeability) – Physical (Electric current, temperature) – Physiological (Change in function properties) Resting Membrane Potential (RMP) is the voltage (charge) difference across the cell membrane when the cell is at rest. Action Potential is the change in electrical potential associated with the passage of an impulse along the membrane of a muscle cell or nerve cell.

7. Muscle contraction mechanism

8. Muscle contraction mechanism Phase 1

9. Muscle contraction mechanism: Phase 2

10. Sample Questions 1.Define muscle. Illustrate the types of muscles with their functions. 2.Give the difference between Skeletal Muscle, Smooth Muscle and Cardiac Muscle. 3.What do you mean by excitable tissues and action potential? 4.Describe the mechanism of muscle contraction briefly.