KeyPoint Muscle Physiology

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1 KeyPoint Muscle Physiology Muscle, what it s for and how it works, with mention of skeleton and adipose tissue BAB L7 Food Animal Biotechnology

2 3 types of muscle Skeletal. Striated, tubular, multinucleated fibres. Voluntary. Cardiac. Striated, branching, (uninucleated) fibres. Involuntary. Smooth. Non-striated, uninucleated fibres. Involuntary.

3 Muscle fibers/cells Terminology for cell structure The plasma membrane is called the sarcolemma The cytoplasm is called the sarcoplasm The SER of a muscle cell is called the sarcoplasmic reticulum and stores calcium Terminology for structure within a whole muscle Muscle fibers are arranged in bundles called fascicles Myofibrils are a bundle of myofilaments that run the length of a fiber Myofilaments are proteins (mainly actin and myosin) that are arranged in repeating units Sarcomeres are the repeating units of actin and myosin found along a myofibril

4 Structure of the sarcomere

5 What are the functions of skeletal muscles? 1. Support the body by allowing us to stay upright 2. Allow for movement by attaching to the skeleton 3. Help maintain a constant body temperature 4. Assist in movement Meat is postmortem vessels (skeletal) in the cardiovascular and lymphatic 5. Protect internal muscle organs and stabilize joints

6 Muscles at work Antagonistic Synergistic

released from the neurons and binds to the muscle fibers This binding

7 Making skeletal muscles work Nerve impulses (action potentials)travel down motor neurons to a neuromuscular junction Acetylcholine (ACh) is released from the neurons and binds to the muscle fibers This binding stimulates fibers (AP) causing calcium to be released from the sarcoplasmic reticulum

8 A motor unit consists of one motor neuron and all of the muscle fibers it controls. Motor units

9 Making skeletal muscles work

10 Muscle Contraction Myosin binds to actin, and slides it, pulling the Z-lines closer together, and reducing the width of the I-bands. Note that filament lengths have not changed.

1. The myosin-binding site on actin becomes available, so the energized cross-bridge binds. 4. Partial hydrolysis of the bound ATP energizes or re-cocks the bridge. 2.

11 1. The myosin-binding site on actin becomes available, so the energized cross-bridge binds. 4. Partial hydrolysis of the bound ATP energizes or re-cocks the bridge. 2. The full hydrolysis and departure of ADP + P i causes the flexing of the bound cross-bridge. The cross-bridge cycle requires ATP 3. Binding of a new ATP to the cross-bridge uncouples the bridge.

12 Cross-bridge formation

13 Length:tension relationship Short sarcomere: actin filaments lack room to slide, so little tension can be developed. Optimal-length sarcomere: lots of actin-myosin overlap and plenty of room to slide. Long sarcomere: actin and myosin do not overlap much, so little tension can be developed.

14 Temporal summation and tetanus

15 Muscle fatigue In skeletal muscle,repetitive stimulation leads to fatigue, evident as reduced tension. Rest overcomes fatigue, but fatigue will reoccur sooner if recovery time is inadequate.

are represented in a typical skeletal muscle, and, under tetanic

16 There are different types of muscle fibre Most muscles have a mixture of the three fibre types All three types of muscle fibers are represented in a typical skeletal muscle, and, under tetanic stimulation, make the predicted contributions to the development of muscle tension.

17 Characteristics differ

The Muscular System. Biology 105 Lecture 12 Chapter 6

The Muscular System. Biology 105 Lecture 12 Chapter 6 The Muscular System Biology 105 Lecture 12 Chapter 6 Outline I. Characteristics of muscles II. Three types of muscles III. Functions of muscles IV. Structure of skeletal muscles V. Mechanics of muscle