Muscle Tissue Flashcards
What are the three types of muscle tissue?
Smooth (non-striated, involuntary)
Cardiac (striated, involuntary)
Skeletal (striated, voluntary)
What are the four functions of muscle tissue?
- produce movement
- posture and stability
- storage and transference of substances (ions, glycogen, enzymes; sphincters)
- heat generation
What are the 4 key properties of muscle tissue?
- excitability
- contractibility
- extensibility
- elasticity
Periosteum
The layer of dense, irregular connective tissue that surrounds the bone and is continuous with synovial tendon sheath of the muscle.
Fascia
Fibrous connective tissue that surrounds the muscle.
What are the two fascial layers?
Superficial
Deep
Superficial fascia
Separates muscle from skin.
AKA subcutaneous or hypodermis fascia
Deep (investing) fascia
Surrounds muscle or a group of muscles and lines body wall.
Holds muscle of similar function together. Allows for free form movement of muscles.
Epimysium
Dense irregular connective tissue layer that encircles the entire muscle.
Perimysium
Dense irregular connective tissue that encircles a fascicle
Fascicle
A bundle of (ten or more) muscle fibres
Endomysium
Tissue layer that encircles and separates each individual muscle fibre within a fascicle
Tendons
Dense regular connective tissue that connect muscle to bone.
Can be continuous with epimysium, permysium and endomysium.
Long, cylindrical and tubular
Aponeurosis
Similar to a tendon, but broad, thin and flat.
Attaches muscle to muscle, or muscle to bone.
Synovial tendon sheaths
Skin for tendon.
Present where tendons are subject to high levels of stress.
Muscle fibre
AKA. Muscle cell
Stores each of the individual muscle filaments (thick and thin)
Develop from myoblasts and are the fundament unit of muscles
Hypertrophy
Increase in size. Muscles do this.
Hyperplasia
Increase in number. Muscles don’t do this.
Atrophy
loss of myofibrils and therefore size of muscle fibre.
Fibrosis
Damage to muscle fibres and replacement by fibrous scar tissue. Occurs when the number of satellite cells can’t keep up with the demand for new myofibrils.
Satellite cell
A mature myoblast that hasn’t transformed.
Aids in muscle repair. Still capable of mitosis (to create more satellite cells).
Myoblasts
Immature muscle cells derived from mesenchymal cells that may fuse with each other to form a mature muscle fibre (or may persist as satellite cell)
Sarcolemma
Plasma membrane of a muscle cell
Sarcoplasm
Cytoplasm of a muscle cell
Myoglobin
Protein found only in muscle cells, that bind O2 for ATP production
Myofibrils
Contracting organelles of skeletal muscle cells.
Myofibril vs muscle fibre
Muscle fibre: muscle cell. Contains myofibrils
Myofibrils: contractile organelles within muscle fibres
Parenchyma
Functional tissue of an organ
Muscle triad
One transverse tubule (T tubule), plus
Two terminal cisternae
Transverse (T) Tubules
Invagination of the sarcolemma, which go from the surface toward the centre of each muscle fibre
Filled with interstitial fluid
Muscle action potentials travels through the T tubules
Terminal cisternae
Enlargement of the sarcoplasmic reticulum, which butt up against T tubule
Ca2+ stored in the SR are released through the terminal cisternae, triggering muscle contraction.
Sarcoplasmic Reticulum
Smooth membranous sac that encircle and surround each myofibril
Stores and releases Ca2+ into the sarcoplasm to help with muscle contraction
Filaments
Contained within myofibril. Two types: Thick and thin.
Arranged in a staggered pattern within 1 sarcomere (z-line to z-line)
Overlap of thick and thin filaments give muscles their striated appearance
Thick and thin filaments pulling on each other are effectively muscle contractions
Thick filaments
1-2 micrometers long. 16 nanometers wide.
Made up of MYOSIN protein
Thin filaments
1-2 micrometers long. 8 nanometers wide.
Made up of ACTIN, TROPONIN, and TROPOMYOSIN proteins
What are the three types of muscle proteins?
Contractile
Regulatory
Structural
Contractile Proteins
Main components that generate force.
- Myosin
- - make up thick filaments - Actin
- - make up thin filaments
Structural Proteins
Help stabilize the entire structure
- Titin
- Mysomesin
- Nebulin
- Dystrophin
Titin
Third most plentiful structural protein
Anchors thick filament from m-line to z-disc.
Helps return filaments to their original position after contraction.
Myomesin
Structural protein.
Forms the M-line. Helps stabilize thick filaments
Nebulin
Structural protein
Anchors thin filaments to z disc
Dystrophin
Structural protein
Help link thin filaments to sarcolemma for stability.
Lacking in muscular dystrophy
Sarcomere
Arrangement of filaments inside a myofibril.
Smallest contractile unit of muscle.
Z disc to Z disc
A Band
Entire length of thick filament with ends overlapping thin filaments. Dark.
I band
Section with only thin filaments. Light.
A Z-band passes through the centre of each I-band
Z Disc
Protein structures located on the Z line.
Help stabilize filaments.
Z line
Lines that dictate the terminal end of one sarcomere unit.
M Line
The exact middle of the sarcomere. Passes through the middle of thick filaments.
Formed by myomesin
H Zone
The middle portion of the A Band of thick filaments only.
No thin filaments.
What happens during the zones during contraction?
Z lines/discs: come together as sarcomere shortens
H zone: shrinks/disappears
I band: shrinks
A band: NEVER CHANGES LENGTH
What are the four steps to the Sliding Filament Theory?
- ATP hydrolysis
- Formation of cross bridge
- Power stroke
- Breaking of cross bridges
Continues as long as ATP and Ca2+ are available.