Name: ________________________________________________
Chapter 5
Muscular System
5.1 Muscle Tissue Categories and Functions
A. Muscle Categories – 3 different types of muscle fibers - Skeletal, Smooth, Cardiac
1. Skeletal Muscle - attaches to bone, primarily for body movement
a. also known as striated muscle or voluntary muscle
b. stimulated by consciously directed nerve activity
c. STRUCTURE of the muscle fibers– thread like shape, multi-nucleated
1. length and diameter differ
2. number of fibers in a person’s muscle is genetically determined
3. number of fibers does not change with age, only injury
4. fibers grow in length and diameter from birth to adult – you can increase
diameter of the fibers with exercise
- Sarcolemma is the cell membrane of a muscle fiber.
- Endomysium is a connective tissue covering over each Sarcolemma
- Perimysium is a fibrous membrane that bundles groups of fibers together.
- Fascicle is a bundled unit of muscle fibers.
- Epimysium is the tough connective tissue that encloses all of the fascicles
It connects both ends of the muscle with tendons or flat, sheet like
tissue known as Aponeurosis.
- Each muscle is connected by a tendon or aponeurosis to another bone,
cartilage or other connective tissue.
2. Smooth Muscle
a. also known as visceral muscle or involuntary muscle
b. found in the walls of many of the internal organs: stomach, intestines, bladder
c. STRUCTURE: cell are small, spindle-shaped, single nucleus, non-striated
1. cells are in layers: one layer surrounds the organ, another is oriented
lengthwise
2. alternating contracting and relaxing of these layers changes the shape of
the organ
a. Peristalsis is a process of symmetrical squeezing of these layers of
smooth muscle
- movement of food through the digestive tract
- emptying of the urinary bladder
- constriction and dilation of blood vessels
- swallowing food or drink
3. smooth muscle is controlled by the autonomic nervous system (automatic)
- unlike striated muscle, smooth muscle can maintain contractions for
longer periods of time without fatiguing
Name: ________________________________________________
3. Cardiac Muscle
a. located only in the walls of the heart
b. STRUCTURE: branched, cross striated, single nucleus, involuntary
1. arranged in interconnected network of figure-eight or spiral-shaped
bundles
2. bundles join together at the intercalated discs
3. bundle arrangement allows for simultaneous contraction of neighboring
bundles to produce the heart beat.
See Chart on page 159 of text.
Striated (Skeletal) Muscle
Smooth Muscle
Cardiac Muscle
Name: ________________________________________________
B. Muscle Functions
1. Behavioral Properties (all muscles share 4 characteristics)
a. extensibility – the ability to be stretched
b. elasticity – the ability to return to normal length after a stretch
c. irritability – the ability to respond to a stimulus (it can be internally from a
nerve signal or externally by a blow or electrical shock)
- the response to all forms of stimuli is a muscle contraction
d. contractility – the ability to contract (shorten)
- tendons usually attach to bone on both ends of the muscle, when
the muscle contracts it pulls on the bone – this pulling force is
known as tensile force
2. Tension and Types of Skeletal Muscle Contraction
a. not all muscles shorten when they develop tension, they can do 1 of 3 things
1. shorten (concentric contraction)
2. nothing (isometric contraction)
3. lengthen (eccentric contraction)
b. Shortening example in a muscle group:
- Bicep moves your arm upward – when stimulated, tension is developed and
the bicep is shortened (concentric contraction). This is known as the
agonist, or prime mover muscle
- the Tricep, the opposing muscle group, is the antagonist. It may relax or
develop a slight tension.
c. Lengthening example of a muscle:
- when you have too much weight to lift and your muscle can not handle the
load. Your muscle would lengthen (eccentric contraction)
d. No change in muscle length example:
- flex your muscle, tension develops but no shortening or lengthening occurs
3. Production of Heat
a. Working muscles generate heat, but even when not exercising muscles
generate heat to help regulate normal body temperature
b. Total body is typically 40% muscle
c. Muscles need ATP to work, the breakdown of ATP releases energy for work
but also heat.