Download Muscle Tone

ST110
Concorde Career College, Portland
Objectives
Define the term muscle.
 Describe the functions of the muscular
system.
 List and identify the structures of the
muscular system and describe the
function of each.
 Identify the types of muscle.

Objectives
Understand the physiology of muscle
contraction.
 Identify muscles according to their
action, location, number of divisions, or
according to the direction that the fibers
run.
 Describe the mechanism by which the
muscular system helps to maintain
homeostasis.

Objectives
Describe common diseases, disorders,
and conditions of the muscular system
including signs and symptoms,
diagnosis, and available treatment
options.
 Demonstrate knowledge of medical
terminology related to the muscular
system verbally and in the written form.

Three Types of Muscle
1. Skeletal
2. Smooth
3. Cardiac
Skeletal Muscle - Three Primary
Functions
1. Movement of the skeleton
2. Maintenance of posture
3. Generation of heat
Anterior View
Posterior View
Skeletal Muscle
Skeletal Muscle
Cardiac Muscle
Muscle Structure

Endomysium

Perimysium

Epimysium
Muscle Structure
Fascicles - bundles of muscle fibers
 Each bundle held together with
connective tissue
 Several bundles encased in tough
connective tissue called fascia

Microscopic Structure

Each skeletal muscle fiber is one muscle
cell.
 Sarcolemma- electrically polarized membrane
covering each fiber.
 Sarcoplasm- found underneath the sarcolemma
and contains the nuclei and mitochondria.

Each muscle fiber is further broken down
into myofibrils that are composed of
myofilaments.
 Myofibrils: further broken down into sarcomeres-
the functioning unit
Microscopic Structure

2 types of monofilaments:
 Myosin- thick filament
 Actin- thin filament, contains 2 proteins
○ Tropomysoin
○ Troposin

The 2 filaments produce striations in
skeletal and cardiac muscle.
 Striations are composed of:
○ I Band (light band)
○ A Band (dark band)
Microscopic Structure

Sarcoplasmic reticulum (SR): system of
tubules and sacs surrounding each
myofibril.
 Stores and releases calcium ions which
regulates the calcium ion concentration with
myofibrils.

Transverse tubules (T tubules) are
attached to surface of SR & have
openings to surface of skeletal muscle
fiber.
Microscopic Structure
Muscle Action
Skeletal muscle action is stimulated by
nerve impulses from the brain and spinal
cord.
 The point where the nerve and the muscle
fiber meet is called the neuromuscular
junction.
 A chemical called a neurotransmitter
(usually acetylcholine) is released from the
nerve stimulates muscle contraction.

Muscle Action







Dendrites
Synapse
Synaptic cleft
Vesicles
Motor end plate
Excitability
Action potential
Contraction
The capacity of muscle to shorten and
thicken is called contractility.
 Muscle fibers contain two types of
proteins

 Actin
 Myosin
Role of Calcium
Necessary for muscle contraction.
 Calcium is stored in the ER of the
muscle cell and is released into the
cytoplasm when the cell is stimulated.
 Calcium exposes the sites on the actin
where the crossbridges form with the
myosin to cause contraction.

ATP
Muscle contraction requires energy in
the form of ATP.
 ATP is produced in the cell by a process
called oxidation (“burning”) of nutrients.
 Oxygen and a nutrient (usually glucose)
are necessary to produce ATP.
 Myoglobin stores oxygen in the muscle.
 Glucose is stored in the form of
glycogen.

Muscle Contraction

Tone - A property of muscle in which a steady
or constant state of partial contraction is
maintained.

Isotonic contraction - Muscles become shorter
and thicker and tone remains the same
(movement)

Isometric contraction - Muscles remain at a
constant length while tension against the
muscle increases (no movement).
Smooth Muscle
Smooth muscle

The mechanism of smooth and cardiac
muscle contraction is the same as that
of skeletal muscles.
 The difference is in the structure and
function of the cells.
Smooth Muscle Fiber Structure
Cells are shorter and have single,
centrally located nucleus.
 The cells are elongated and taper at
both ends.
 Myofibrils contain actin and myosin &
are randomly arranged, not striated.

Smooth Muscle Fiber Structure

Visceral smooth muscle: most common
type, located in the walls of hollow
organs.
 2 layers:
○ Outer-fibers travel in longitudinal
○ Inner- fibers are arranged in a circular pattern
 The multi-layer arrangement of fibers allows
the organ to change in shape and size.
○ EXAMPLE: stomach after a meal (3 layers).
 Peristalsis- wavelike motion (like intestines)
Cardiac Muscle
Cardiac Muscle
aka myocardial muscle
The only smooth muscle that has
striations.
 Muscle cells are arranged end to end to
form fibers that are interconnected.
 Muscle cells have a centrally located
single nucleus and have actin & myosin
filaments.
 Endomysium-located between muscle
fibers & contains capillaries and
lymphatics.

Cardiac Muscle

Cells are joined at each end by
intercalated disk. This allows for rapid
transfer of impulses from cell to cell
 “all or nothing manner”
Myogenic: spontaneous, involuntary
contractions of the heart.
 The rate of contractions is controlled by
nerve impulses from the ANS.

Cardiac Muscle

Electrocardiogram (ECG)-records the
rhythmic patter of a heartbeat.
Attachments of Skeletal Muscles

Tendons - Attach muscle to bone

Aponeurosis - broad and flat tendon
Tendons & Ligaments

Tendons - attach
muscle to bone.

Ligaments - attach
bone to bone.
Tendons

Dense fibrous connective tissue.
Consists of parallel fibers held together
by tenosynovium. Fibers of the tendon
come together with the periosteum of
bone. This attatches muscle to bone.
Typically inserted at the distal end of
bone.
○ Tendinitis
○ Tenosynovitis
Tendon Structure
Ligaments

Fibrous connective tissue consisting of
parallel collagenous bundles that bind
bone to bone, forming joints.
Fascia

Aponeuroses: special type of fascia that
binds muscle to muscle.
 EXAMPLE: external abdominal oblique
muscle
Fascia

Fascia – fiberous connective tissue that
covers and supports muscle.
○ 3 types-
 Deep: surrounds muscle to hold them together and
provide support.
- Forms fascial compartments: contain groups of
muscles that have nerves and blood vessels.
- Compartment Syndrome
• Fasciotomy- surgical incision through a fascia
to relieve tension or pressure.
 Subcutaneous: continuous layer of connective
tissue over the entire body. Between skin and deep
fascia.
 Subserous: located between internal layer of deep
fascia and the serous membranes.
Attachments of Skeletal Muscles

Origin
 The more fixed and stationary attachment
that serves as a basis for action
 proximal

Insertion
 Movable attachment where effects of
contraction are seen
 distal
Terminology of Movement
Agonists - Perform the main action (also
called prime movers)
 Antagonists - Opposite action of the
agonist
 Synergists - Assist prime movers
 Flexion - Bending
 Extension - Straightening

Extension & Flexion
Extension & Flexion
Antagonistic muscle pair of
the upper arm in action.
During extension of the
elbow (shown at left), the
triceps is contracted and
the biceps is relaxed.
During flexion of the
elbow (shown at right),
the triceps is relaxed and
the biceps is contracted.
Terminology of Movement
Naming and Action of Skeletal
Muscles

Named by:
 Action
 Shape
 Origin and insertion
 Location
 Number of divisions
 Direction of fibers
Naming and Action of Skeletal
Muscles
Muscles named for
the number of
divisions: Posterior
view shown at left.
Anterior view
shown at right.
Muscles of the Head and Neck
(lateral view)
Major Cervical Muscles
Muscles of the Arm
Muscles of the Arm
Muscles of the Trunk
 Abdomen



– Three layers
External oblique (outer most)
Internal oblique
Rectus abdominis
 Respiratory


muscles
Intercostal muscles (important for respiration)
Diaphragm (separates the thoracic and abdominal
cavities)
Muscles of the Abdomen
Muscles of the Abdomen
Muscles of the Leg
Muscle Disorders

Caused by problems with:





Vascular supply
Nerve supply
Connective tissue sheaths around muscle
Muscle bundles
Symptoms





Paralysis
Weakness
Degeneration or atrophy
Pain
Spasms
Paralysis
 The
loss of sensation and voluntary muscle
movement through disease or injury to its nerve
supply





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Myoparesis
Hemiparesis
Hemiplegia
Cardioplegia
Paraplegia
Quadriplegia
Contracture
A muscle shortens its length in the
resting state
 Lack of exercise
 Treatment
 Relengthening

Torticollis
Cramps
Spastic, painful contractions
 Irritation caused by lactic acid build-up
or inflammation

Myasthenia Gravis
Easy tiring of muscles and/or muscle
weakness
 Starts in face
 Abnormal ACh destruction

Torn Muscle
Other Disorders

Myalgia
 Muscle pain

Myositis
 Inflammation

Atrophy
 Decrease in muscle bulk
 Lack of exercise
 Electrical current
Other Muscle Disorders

Hypertrophy
 Increase in muscle size
 Muscle bulking
 Exercise and weight-lifting

Tendinitis
 Tendon inflammation

Muscular dystrophy
 Genetic
 Muscle tissue degenerates over time
Hypertrophy

Variances of
muscle size and
shape:
hypertrophy.
Atrophy

Variances of
muscle size and
shape: atrophy.