Download PowerPoint 09- Muscle Tissue

Muscle Tissue
Handout #5 Muscles and
#6 Excitation-Contraction
A. Types of muscle
B. Functions of muscle
C. Characteristics of muscle
D. Anatomy and innervation of skeletal
muscle tissue
1. Nerve and blood supply
2. Connective tissue components
3. The motor unit
4. The neuromuscular junction
5. Microscopic anatomy of muscle
a. Myofibrils
b. Sarcoplasmic reticulum
and transverse tubules
E. Contraction of skeletal muscle
1. Sliding filament mechanism
a. Role of calcium
and regulator proteins
b. The power stroke
and the role of ATP
2. Relaxation
3. Muscle tone
4. Homeostasis of
body temperature
F. Adjusting muscle tension
1. Twitch
2. Frequency of stimulation
a. Tetanus
b. Staircase effect (treppe)
3. Number of muscle cells contracting
4. Isotonic and isometric contractions
G. Cardiac muscle
H. Smooth muscle
Motion results from alternating
contraction (shortening) and
relaxation of muscles.
The prime function of muscle is to:
convert chemical energy (ATP) into
mechanical energy in order to:
1. generate force
2. perform work
3. produce movements
Types of Muscle Tissue
1. skeletal muscle
2. cardiac muscle
3. smooth muscle
Functions of Muscle Tissue
1. motion
2. stabilizing body positions and
regulating organ volume
3. thermogenesis
Characteristics of Muscle Tissue
1.
2.
3.
4.
excitability (irritability)
contractility
extensibility
elasticity
Anatomy of Skeletal Muscle
Blood supply and innervation of skeletal
muscle tissue
Fascia
1. superficial
2. deep
Deep Fascia
Superficial fascia
Connective Tissues of Skeletal Muscle
1. epimysium
2. perimysium
-- fascicles
3. endomysium
_______________
4. tendon
5. tendon sheath
6. aponeurosis
Microscopic Anatomy
1.
2.
3.
4.
5.
6.
myofiber
sarcolemma
sarcoplasm
myofibrils
myofilaments
sarcomeres
Skeletal Muscle Anatomy
Summary
1.
2.
2.
3.
Sarcomere
Z disc
thin and thick myofilaments
A bands and I bands
striations
Thin Myofilament
1. actin
a. actin filaments (2)
b. myosin-binding sites
2. tropomyosin
3. troponin
_______________________
4. tropomyosin-troponin complex
Thick Myofilament
1. myosin
2. filamentous tail (shaft)
3. globular head (cross
bridge)
___________________
4. titan (elastin filament)
Sarcoplasmic Reticulum
1.
2.
3.
4.
intracellular tubules
stores Ca++ at rest
releases Ca++ when stimulated
Ca++ diffuse into sarcoplasm
Transverse Tubules
1.
2.
3.
4.
5.
tunnel-like infoldings of sarcolemma
lie at right angles to myofibrils
filled with ECF
terminal cisternae
muscle triad
The Nerve Muscle Relationship
1.
2.
3.
4.
motor neuron
motor unit
precise vs gross control
What is recruitment?
The Neuromuscular Junction
1. axon terminals
2. synapse and
synaptic cleft
3. motor end plate
4. synaptic vesicles
5. neurotransmitter =
acetylcholine (ACh)
7. exocytosis
8. ACh receptors on
motor end plate
Neuromuscular Junction
Excitation-Contraction Coupling
Sliding filament theory
1. thick myofilaments attach to thin myofilaments
2. cross bridges "tilt" or swivel
3. thin myofilaments "slide" across thick
myofilaments
4. Z discs are drawn together
5. sarcomeres shorten
Sliding filament theory
Excitation-Contraction Coupling
Power Stroke
1. ACh stimulates motor end plate
2. action potential crosses
sarcolemma, T-tubules, and
sarcoplasmic reticulum
3. Ca++ channels open
a. Ca++ bind T-T complex
b. Ca++ activate ATPase
4. cross bridges bind and swivel
Cross Bridge Cycle
Recovery stroke (muscle relaxation)
acetylcholinesterase
2. calsequestrin
1.
Summary of Muscle Contraction
Muscle Tone
1. sustained, small contractions of motor
units
2. few motor units contracting, others
relaxed
3. muscle firmness without producing
movement
4. essential for maintaining posture
5. asynchronous firing of motor units
Muscle Metabolism During
Contraction
1. aerobic
2. phosphagen
3. glycogen-lactic acid
Phosphagen System
What is oxygen debt?
The difference between oxygen consumption
at rest and oxygen consumption following
exercise.
This "debt" must be "repaid" in order to:
1. replace the body's oxygen reserves
2. replenish the phosphagen system
3. oxidize accumulated lactic acid
4. serve the elevated metabolic rate postexercise
Physiological Classes of Muscle
Fibers
1. slow oxidative, slow-twitch, red, or type I fibers
abundant mitochondria, myoglobin, and capillaries
aerobic respiration
2. fast glycolytic, fast-twitch, white, or type II
fibers
poor in mitochondria, myoglobin, and capillaries
rich in enzymes of the phosphagen and glycogen
pathways
vast sarcoplasmic reticulum (rapid Ca++ movement)
anaerobic respiration
fatigue quickly
3. intermediate fibers (at least 3 types)
Homeostasis of Body
Temperature
Controlled Condition- A stimulus or stress disrupts homeostasis by
causing body temperature to decrease below normal.
.
Receptors-Thermoreceptors, located in the skin and in the hypothalamus,
detect the decreased body temperature and provide nervous input to the
hypothalamus.
Control Center- The hypothalamic temperature control center integrates
the input, then provides output that leads to stimulation of skeletal muscles.
Effectors- In response, large skeletal muscle groups increase their muscle
tone involuntarily (shivering).
Return to Homeostasis- Due to the inefficient use of energy by contracting
skeletal muscles, heat is generated, the body temperature increases, and
the negative feedback loop turns off the shivering.
BODY TEMPERATURE CONTROL
CONTROLLED CONDITION
A stimulus or stress disrupts
homeostasis by causing a decrease in
body temperature
negative
feedback
RETURN TO HOMEOSTASIS
Due to inefficient use of energy by
contracting skeletal muscles, heat
generated raises body temperature
RECEPTOR
Thermoreceptors in skin and
hypothalamus are activated and send
nerve impulses to the control center
EFFECTORS
Large skeletal muscle groups increase
their muscle tone involuntarily
(shivering)
CONTROL CENTER
Hypothalamic control center initiates nerve
impulses that lead to stimulation of skeletal
muscles
end
Regulation of Body Temperature
Behavior of Whole Muscles
Adjusting muscle tone
1. all-or-none principle
2. threshold stimulus
Adjusting muscle tone -- The amount of force
(tension) that a muscle can generate depends
upon four factors:
1. frequency of stimulation of muscle fibers
by motor neurons
2. length of muscle fibers before they
contract
3. number of muscle fibers contracting at
any one time (number of activated motor
units) -- process of recruitment
4. structural components of the muscle itself
Length Tension Relationship
Twitch Contractions
1.
2.
3.
4.
latent period
contraction period
relaxation period
refractory period
Treppe contractions
(staircase phenomenon)
Wave Summation
1. incomplete tetany
2. complete tetany
Isotonic versus Isometric
Contratctions
Cardiac Muscle
1.
2.
3.
4.
5.
6.
striated
single nucleus/cell
intercalated discs
functional syncytium
involuntary
self-stimulating
Smooth Muscle
1.
2.
3.
4.
non-striated
no sarcomeres
single nucleus/cell
two types
a. visceral
(functional syncytium)
b. multiunit