Chapter 9

MUSCLE AND MUSCLE TISSUE

I.Overview of Muscle Tissue

· Most distinguished functional characteristic of muscle??

A. Muscle Types

a. General Characteristics

· Muscle fibers

· Myofilaments

b. 3 types of muscle

c. Muscle function

· Performs important functions

B. Functional Characteristics of Muscle

· Have specific functional properties that assist in performing duties.

II. Skeletal Muscle (summarized in Table 9.1, pg. 250)

A. Gross Anatomy

Basic Features

1. Connective tissue wrappings

2. Nerve and Blood supply

1. Nerve

2. blood

3. Attachments

a.origin

b.insertion

· Muscle's , moves movable bone toward the immovable bone, the muscle's .

c. Attachment can be

(1)

(2)

B. Microscopic Anatomy of a Skeletal Muscle Fiber

1. Basic Features

2. Myofibrils

a. Characteristics

(1)

(2)

(3)

b. Striations, Sarcomeres and Myofilaments (also refer to Figure 9.2, pg. 264)

(1) Striations

c. Ultrastructure and Molecular Composition of Myofilaments

1) Thick filament

· Main component

(2) Thin filament

· Main component

· Regulatory proteins

3. Sarcoplasmic Reticulum and T Tubules (Figure 9.4, pg. 254)

· Intracellular tubules that assist in regulation of muscle contractions.

a. Sarcoplasmic Reticulum (SR)

b. T tubules, or transverse tubule

C. Contraction of a Skeletal Muscle Fiber

1. Regulation of Contraction

· For contraction, what must occur?

· An event linking the electrical signal and contraction is?

a. Neuromuscular junction and nerve stimulus

(1) Neuromuscular junction

(2) Nerve stimulus

b. Generation of action potential across sarcolemma

· Event at sarcolemma:

· Action potential, involves three steps

· Once intiated, action potentials will not stop, referred to as

b. Roles of ionic Ca in muscle contraction

(1) Ca levels in sarcoplasm are kept low; why??

c. Destruction of Ach

· Enzyme involved?

d. Excitation-contraction coupling

· Defined as

· Events of excitation-contraction coupling

2. Sliding filament mechanism

a. Described as

b. During contraction will observe 4 steps:

(1)

(2)

(3)

(4)

c. Mechanism by which filaments slide

· Involves cross bridges (myosin heads)

· Events of sliding actin filaments during contraction

D. Contraction of Skeletal Muscle

1. Motor unit

2. Muscle twitch and development of muscle tension

Muscle twitch, defined as

a. Has 3 distinct phases

(1)

(2)

(3)

3. Graded muscle responses

1. In general, muscle contraction can be graded in two ways

(1)

(2)

2.

Wave summation and tetanus

3. Multiple motor unit summation, or recruitment

(1) Involves:

—

4. Treppe

5. Muscle tone

6. Isotonic and isometric contractions

a. Muscle tension

b. Two main categories of contraction

(1) Isotonic contraction

(2) Isometric contraction

c. Important points

(1)

(2)

E. Muscle metabolism

1. Providing energy for contraction, achieved from:

2. Muscle fatigue

3. Oxygen debt

a. Defined as

4. Heat production during muscle activity

F. Force, Velocity and Duration of Muscle Contraction

1. Force of contraction, affected by:

2. Velocity and duration of Contraction

· Influenced by:

a. Load, or resistance

b. Muscle fiber type

· Three basic types dependent on speed, size and endurance:

(1)

(2)

(3)

NOTE: All muscle fibers associated with a particular motor unit are of the same type.

III. Smooth Muscle

A. Arrangement of Smooth Muscle fibers and Microscopic Structures

1. Basic characteristics

2. Characteristics of Myofilaments

B. Contraction of Smooth Muscle

1. Mechanism and Characteristics

a. Coordinated contraction accomplished via

b. Rhythmic contractions achieved by

c. Modification of rate and intensity of contraction accomplished by

d. Mechanism involves:

· Events that parallel skeletal

(1)

(2)

(3)

· Unique to smooth muscle

(1) Ca available from and .

(2) Troponin lacks , thus is always

e.Series of events:

(1)

(2)

(3)

f. Smooth muscle tone

2. Regulation of Contraction

· Activation by neural stimluli identical to skeletal muscle, but:

C. Types of Smooth Muscle

1. Two major types: