Unit 1 Muscle Basics Flashcards
Muscle Types
- Skeletal
- Cardiac
- Smooth
Skeletal Muscle Characteristics
- Striated (myosin & actin)
- Voluntary control
- Multiple nucleus
Cardiac Muscle Characteristics
- In heart
- Striated
- Involuntary control
- Single nucleus
Smooth Muscle Characteristics
- In viscera, blood vessels & skin
- Not striated
- Involuntary control
- Single nucleus
Muscle Tissue Functions
- Produce body movements (bone/tendon attachment)
- Stabilize body positions
- Producing heat (thermogenesis)
- Storing & moving substances in body
Muscle Tissue Properties
- Electrical excitability
- Contractility
- Elasticity
- Extensibility
Electrical Excitability
- Respond to stimuli
- Electrical & chemical signals
Contractility
- Attach to bone via tendons
- Cells contract to generate force
Elasticity
- Return to original length
- After contraction & extension
Muscle Organization
- Periosteum
- Tendon
- Epimysium
- Fascicle
- Perimysium
- Endomysium
- Myofibre
- Myofibril
Periosteum Function
- Lines surface of bone
Epimysium Function
- Encases muscle
Fascicle
- Bundle of myofibrils
Perimysium Function
- Encases fascicle
Endomysium Function
- Covers myofibre
Myofibre
- Muscle cell
Myofibril
- Think & thick filaments
- Repeating units of sarcomeres
Sarcomere
- Contractile unit of muscle
Z-Line
- Two sets of actin (thin) fibers join together
M-Line
- Two sets of myosin (thick) fibers join together
I-Band
- Region within myofibril
- Only actin present
H-Band
- Region within myofibril
- Only myosin present
A-Band
- Full length of myosin region
- Overlap with actin
- Remains same width
Myosin Structure
- Formed by two pieces
- Two heads & tails
- Actin binding site at 1 head
- ATP binding site at 1 head
Actin Structure
- Formed by series of balls
- Double helix
- Myosin binding site
- Covered by tropomyosin
-Troponin to interact with tropomyosin
Muscle Attachment
- attach to bones via tendons
Tendon Composition
- Continuation of fascial layers encasing muscle
Muscle Contraction Signal Pathway
- Brian
- Brainstem
- Spinal cord
- Periphery
- Upper & lower motor neuron
Upper Motor Neuron
- Takes contraction signal from brain
- Down spinal cord
- Synapse occurs
Lower Motor Neuron
- Carries contraction signal from spinal cord
Out to muscle
Contralateral Innervation
- Signals originating on one side
- Innervate opposite side
Motor Unit Composition
- Motor neuron
- All muscle fibers innervated
Force Production Equation
= Motor unit size + Firing frequency
Low Force Contractions
- Recruitment of small motor units
High Force Contractions
- Recruitment of large motor units
Skeletal Fiber Types
- Type I slow oxidative
- Type II fast oxidative-glycolytic
- Type Iix fast glycolytic
Skeletal Fiber Composition
- All muscles contain all fiber types
- Varying proportions
- Train specific fibers
Slow Oxidative Fiber (Type I)
- Slow fatigue rate
- Low force
Fast Oxidative-Glycolytic Fiber (Type II)
- Medium fatigue rate
- Medium force
Fast Glycolytic Fiber (Type IIx)
- Fast fatigue rate
- High force
Sliding Filament Theory Steps
- Bound sate
- Power stroke
- Rigor state
- Relaxed state
- Binding state
Muscle Contraction Characteristics
- Repetitive crossbridge formation cycle
- Elevated Ca++ levels
- Requires ATP
- Conformation change in myosin
- Z-disks move closer
Calcium (Ca++) Release
- Flows out of sarcoplasmic reticulum (SR)
- Down concentration gradient
Tendon/Muscle Injury Symptoms
- Swelling/bruising/redness
- Pain at rest
- Inability to use muscle/weakness
Grade 1 Tendon/Muscle Injury
- Over-stretching
Grade 2 Tendon/Muscle Injury
- partial tear
Grade 3 Tendon/Muscle Injury
- complete tear
Muscle Loss
- Progressive with aging 30+
- Replaced by fibrous connective tissue & adipose
Muscle Loss Causes
- Decreased voluntary neural control
- Slow nerve conduction speed
- Muscle fiber loss
Exercise Benefits on Muscle
- Increased bone density
- Increased motor neuron firing rate
- Hypertrophy (muscle size increase)
Aerobic & Strength-Based Activities
- Slows & reverses age-related muscle decline
