Lab 7
Muscles and Muscle Tissue
Gilbert R. Pitts, Ph.D., Joseph R. Schiller, Ph.D., and Amy L. Thompson, Ph.D.
Lab 7 Activities
1.
2.
3.
4.
5.
6.
7.
Review histology of skeletal, cardiac, and smooth muscle
(macerated and intact)
Identify structures of sarcomeres on electron micrographs
[ultrastructure]
Describe how the arrangement of fascicles in a muscle relates
to power and range of motion
Describe the classification of muscles into functional groups
Describe the conventions used in the naming of muscles
Identify the muscles and their actions on models and diagrams
Use PhysioEx Exercise 2--Skeletal Muscle Physiology to learn
basic concepts of muscle physiology: latent period, treppe,
multiple motor unit summation/recruitment, and temporal
summation (including tetany)
Some Muscle Terminology
Myology: the scientific study of muscle
muscle fibers = muscle cells
myo, mys & sarco: word roots referring to muscle
Three Types of Muscle:
skeletal, cardiac, and smooth
They differ in:
microscopic anatomy -- location --
regulation by the endocrine system and the nervous system
Characteristics of Skeletal Muscle
• Attached to bones
• Voluntary (conscious)
control (usually)
• Contracts quickly, tires
easily (fatigable)
• Undergoes graded
contraction
Skeletal Muscle Cells
• Long, cylindrical cells
• Striated (banded)
• Multinucleate
Striations /Sarcomeres
• Z discs (lines): the boundary
between sarcomeres; proteins
anchor the thin filaments
• A (anisotropic) band:
overlap of thick (myosin)
filaments & thin filaments
• I (isotropic) band: thin
(actin) filaments only
• Z line: bisects each I band
• H zone: thick filaments only
• M line: proteins anchor the
adjacent thick filaments
Sarcomeres
• Components of the muscle
fiber with myofilaments
arranged into contractile
units
• The functional unit of
striated muscle contraction
• Produce the visible banding
pattern (striations)
• The myofilaments between
two successive z discs
• Sliding filament
mechanism for contraction
Characteristics of Cardiac Muscle
• Forms most of heart wall
(myocardium)
• Involuntary (unconscious)
• Autorhythmicity (contracts
w/out external stimuli)
• Fast contraction, non-fatigable
• Intrinsic rhythm modified by
neural and hormonal signals
Cardiac Muscle Cells
•
•
•
•
Striated
Uninucleate
Branched
Intercalated discs
– gap junctions
– desmosomes
Characteristics of Smooth Muscle
• found in the walls of hollow
internal structures (digestive,
respiratory, reproductive tracts,
blood vessels)
• Arrector pili, pupil of the eye,
etc.
• Involuntary (unconscious) &
may be autorhythmic
• Long, slow contractions, nonfatigable
Smooth Muscle Cells
• Nonstriated = smooth
(no sarcomeres)
• Uninucleate
• May gap junctions
Smooth Muscle Cells
• Actin and Myosin
contractile proteins are
not organized into
sarcomeres; instead
the fibers attach to the
dense bodies under the
cell membrane
Connective Tissue Coverings of
Skeletal Muscle
• Superficial Fascia:
"hypodermis"
• Deep Fascia: lines body walls
& extremities; binds muscle
together, separating them into
functional groups
• Epimysium: wraps an entire
muscle
• Perimysium: subdivides each
muscle into fascicles, bundles
of 10-100 muscle fibers
• Endomysium: wraps
individual muscle fibers
Arrangement of Fascicles
• Range of motion: depends
on length of muscle fibers
(fascicles); long fibers =
large range of motion
– parallel and fusiform
muscles
• Power: depends on total
number of muscle fibers;
many fibers = great power
– convergent, pennate,
bipennate, multipennate
Attachments (to bone)
• Derived from connective tissue elements:
– insertion: the part of a muscle attached to the bone that
moves (relative to a particular motion)
– origin: the part of a muscle attached to the stationary
bone
– direct attachment: connective tissue coverings fused
directly to periosteum
– indirect attachment: connective tissue coverings
gathered into a tendon or aponeurosis that attaches to
periosteum
• tendon: cord (of dense regular connective tissue)
• aponeurosis: sheet (of dense regular connective tissue)
The
Neuromuscular
Junction
• Structure where motor neuron
communicates with skeletal
muscle fiber
• Two parts:
– Axon terminal
– Motor end plate
• Separated by synaptic cleft
Summary
of Muscle
Structure
Muscle Functional Groups
• Muscles are classified into functional groups
according to their role in producing a particular
movement:
– prime mover(s) (= agonists): the muscle(s) primarily
responsible for the movement
– antagonist(s): the muscle(s) that oppose (or reverse)
the movement caused by the prime mover.
– synergist(s): the muscle(s) that assist the prime mover
– fixator(s): the muscle(s) that immobilize the origin of
the prime mover
Naming Skeletal Muscles
•
•
•
•
•
•
•
Location of the muscle
Shape of the muscle
Relative Size of the muscle
Direction/Orientation of the muscle fibers/cells
Number of Origins
Location of the Attachments
Action of the muscle
• Know the muscle names as described in Lab
Manual Lab 7 (pp. Lab 7-1 to Lab 7-24)
Muscles Named by Location
• Epicranius (around
cranium)
• Tibialis anterior
(front of tibia)
tibialis
anterior
Naming Skeletal Muscles by Shape
• Deltoid (triangle)
Trapezius
• Trapezius (trapezoid, 2
Deltoid
parallel sides)
• Serratus (saw-toothed)
• Rhomboideus
(rhomboid, 4 parallel
sides)
• Orbicularis and
sphincters (circular) Serratus anterior
Rhomboideus
major
Muscles Named by Size
• Maximus (largest)
• Minimis (smallest)
• Longus (longest)
• Brevis (short)
• Major (large)
• Minor (small)
Psoas
minor
Psoas
major
Muscles Named by Direction of Fibers
• Rectus (straight)
- parallel to the
body’s long axis
rectus
abdominis
• Oblique
external
oblique
transversus abdominis
Transverse – at right angles
to the body’s long axis
Muscles Named for Number of Origins
• Biceps (2)
• Triceps (3)
• Quadriceps (4)
biceps
brachii
Muscles Named for Origin and Insertion
insertion
Sternocleidomastoid
originates from sternum
and clavicle and inserts
on mastoid process of
temporal bone
origins
Muscles Named for Action
• Flexor carpi radialis (extensor
carpi radialis) –flexes wrist
• Abductor pollicis brevis
(adductor pollicis) –flexes
thumb
• Abductor magnus – abducts
thigh
• Extensor digitorum – extends
fingers
adductor
magnus
Skeletal Muscles
Know the muscles, their origins and
insertions as described in your Lab
Manual 7.
Contraction of a Skeletal Muscle
• The Motor Unit = Motor Neuron + Muscle Fibers to
which it connects (Synapses)
Myogram: The Recording of Electrical
Activity During Muscle Contraction
• Stimulus: nerve impulse or
electrical charge
• All or none rule: all the
muscle fibers of a motor
unit contract all the way
• Twitch: a single contraction
of all the muscle fibers in a
motor unit (one nerve
signal)
Components of the Myogram
• 1. latent period: delay between
stimulus and response
• 2. contraction phase: tension
or shortening occurs
• 3. relaxation phase: relaxation
or lengthening
• refractory period: time
interval after excitation when
muscle will not respond to a
new stimulus
Contraction of a Skeletal Muscle
• Graded muscle responses - moving a load
• Force of muscle contraction varies depending
on needs - how much tension is needed?
• Twitch does not provide much force
• Contraction force can be altered in 3 ways:
1. changing the frequency of stimulation
2. changing the force of stimulation
3. changing the muscle’s length
Graded Muscle Responses
• Twitch: a single contraction
• Wave (temporal) summation: contractions repeated
before complete relaxation, leads to progressively
stronger contractions
Graded Muscle Responses
• Unfused (incomplete) tetanus: frequency of
stimulation allows only incomplete relaxation
• Fused (complete) tetanus: frequency of stimulation
allows no relaxation
Graded Muscle Responses
Treppe: the staircase effect
• “warming up” of muscle
Multiple Motor Unit Summation
( Recruitment)
The stimulation of
more motor units
leads to more
forceful muscle
contraction
Contraction of a Skeletal Muscle
• Isometric Contraction = Muscle does not shorten
• Tension increases
Contraction of a Skeletal Muscle
• Isotonic Contraction = tension does not change
• Length shortens
Force of Contraction
1. Number of muscle fibers contracting
(recruitment)
2. Size of muscle
3. Series elastic elements
4. Degree of muscle stretch
PhysioEx MAP First Screen
Select: Exercise 2: Skeletal Muscle Physiology
PhysioEx MAP Next Screen
5
Complete Activities 1-4 and 6;
Exercise 2: Skeletal Muscle Physiology: Activity 1-3:
[The Muscle Twitch and Latent Period]
We suggest you read the Overview and Introduction and take the Pre-lab
Quiz before conducting the Experiment and take the Post-lab Quiz after
conducting the Experiment for each of the 5 Activities. You do not need
to print out or turn in any of the 5 Pre- and Post-lab quizzes.
Exercise 2: Skeletal Muscle Physiology: Activity 1-3:
[The Muscle Twitch and Latent Period]
Follow the
detailed PhysioEx
instructions on
pages 7-25 to 7-32
in your manual
and record data
in the charts in
those pages and
answer the
questions on the
pages as you go.
Exercise 2: Skeletal Muscle Physiology: Activity 4:
[The Effect of Stimulus Frequency …]
• Notice the frequency of the stimuli (stimuli/sec) can be
adjusted as indicated by the multiple stimuli button
Exercise 2: Skeletal Muscle Physiology: Activity 6:
[The Skeletal Muscle Length-Tension Relationship]
PhysioEx Homework to Turn In
You will have four tables of data to print from
PhysioEx: Activities 2, 3, 4, & 6 to turn in.
You will have 9 questions to answer about the
PhysioEx Activities on pp. 7-33 & 7-34 in the
Lab Manual to turn in.
End Lab 6 Presentation
Antagonists of the Forearm
Antagonists of the Thigh
Antagonists of the Foot