Muscular System
Warm-up:
• What are some functions of the muscular
system? Be prepared to explain each
function (You must come up with 2 functions)
• Hint: types of muscle include: skeletal,
cardiac, and smooth
Warm-up:
• Skeletal:
• Cardiac
• Smooth:
Types of Muscle
●Skeletal – striated & voluntary
●Skeletal and smooth muscle cells are
elongated (muscle cell = muscle fiber)
The word
“striated” means
striped. Skeletal
muscle appears
striped under a
microscope.
Types of Muscle
Skeletal:
• Most are attached by tendons to bones
• Cells are multinucleate
The word
“striated” means
striped. Skeletal
muscle appears
striped under a
microscope.
Types of Muscle
• Contraction of muscles is due to the movement
of microfilaments
• All muscles share some terminology
Prefixes myo and mys refer to “muscle”
Prefix sarco refers to “flesh”
Types of Muscle
●Smooth – involuntary
- Lacks striations
-Spindle-shaped cells
-Single nucleus
The word
“striated” means
striped. Skeletal
muscle appears
striped under a
microscope.
Types of Muscle
●Cardiac – heart
-Striations
-Usually has a single nucleus
-Branching cells
The word
“striated” means
striped. Skeletal
muscle appears
striped under a
microscope.
Types of Muscle
●Cardiac – heart
-Joined to another muscle cell at an intercalated disc
Muscles and Muscle Fiber Structure
Muscles are composed of many FIBERS that
are arranged in bundles
called FASCICLES
Individual muscles are separated by FASCIA,
which also forms tendons
-Connective tissue, mainly collagen
EPIMYSIUM = outermost layer, surrounds
entire muscle.
PERIMYSIUM = separates and surrounds
fascicles (bundles of muscle fibers)
ENDOMYSIUM
= surrounds
each individual
muscle fiber
This model of the muscles uses
straws to represent fibers.
Green = endomysium
Yellow = perimysium
Blue = epimysium
Muscle Layers
Muscle Fiber
Endomysium
Perimysium
Epimysium
Epimysium
Perimysium
Endomysium
1. Threshold Stimulus
Minimal strength required to cause a contraction
Motor neuron releases enough acetylcholine to
reach threshold
2. All-or-None Response
Fibers do not contract partially, they either do or
don't
Threshold Stimulus Virtual Lab
http://www.mhhe.com/biosci/genbio/virtual_labs/BL_21/BL_21
.html
Microscopic Anatomy of Muscle Fiber
Muscles / Cells
Sarcolemma =
Sarcoplasm =
Sarcoplasmic Reticulum Myofibrils =
Nucleus
Sarcolemma
Mitochondrion
Sarcoplasm
Myofibril
Microscopic Anatomy of Muscle Fiber
Myofibrils are made of
ACTIN =
MYOSIN =
Myofilaments ACTIN (thin) and MYOSIN (thick)
-- form dark and light bands
 A band = dArk • thick (myosin)
 I band = lIght • thIn (actin)
Sarcomere:
Components of Sarcomere:
M-line:
Z-line:
Components of Sarcomere:
H-zone:
It is important to remember the hierarchy
fasicles
myofibrils
myofilaments
actin
myosin