what is skeletal muscle and its funcitons
Skeletal muscle
Striated
Voluntary
Visible cross striations
Multinucleated
Attached to bones
Functions are to:
1. Produce skeletal movement
2. Maintain posture
3. Support soft tissues
4. Gaurd entrances and exits (sphincters)
5. Maintain body temperature (heat production)
6. Store nutrient reserves (glycogen)
what is cardiac muscle and its functions
Cardiac muscle
Found only in heart
Striated
Involuntary
Branched fibers
Connected by intercalated disks
Contracts as a coordinated unit
The intercalated disks allow electrical communication and synchronized contraction
what is smooth muscle and its funcitons
smooth muscle
Also called visceral muscle
Non striated
Involuntary
Part of digestive tract walls, blood vessels, bladder, uterus
Functions are to move substances thru hollow organs and control vessel diameter
what is connective tissue and what does it wrap arround
Connective tissue forms wrappers around each muscle fiber, fascicles (groups) of muscle fibers, and around the entire muscle, and fascia surrounds muscle organs and nearby structures
(so the Epimysium, Perimysium, Endomysium)
each muscle has 3 layers:
Each muscle has 3 layers:
1. Epimysium → surrounds entire muscle
2. Perimysium → surrounds fascicles (bundles of fibers)
3. Endomysium → surrounds each individual muscle fiber
what is the hierarchy of organizaiton for muscles to the myofilaments
Hierarchy of organization:
Muscle → fascicles → muscle fibers (myofibers) → myofibrils → myofilaments
what encloses the individual myofibrils and contains the myosatellite cells and cpaillaries
- Endomysium → surrounds each individual muscle fiber/myofibril (which contains myosatellite cells)
what are three key regions of a skeletal muscle
Most skeletal muscles:
Cross at least one joint and attach to bones through tendons
Key terms:
Origin → attachment of stationary/fixed bone when movement occurs
Insertion → attachment to moving bone
body/belly → main contractional region/main part of the region
what are tendons
Tendons:
These are made up of dense fibrous connective tissue
Attach muscle to boneW
WHAT are tendons surrounded by and why
Tendons:
Some are surrounded by synovial tendon sheaths which reduce friction and contain synovial fluid
give two reasons skeletal muscle are unique and why
Skeletal muscle formation
Skeletal muscle fibers are unique because they are:
1. Very large
2. Multinucleated → this is to form fusion of embryonic cells called myoblasts which allows for more protein formation, more genetic transcription and translation, and explains the larger size
Each muscle fiber has:
Sarcolemma (plasma membrane), wraps the muscle
Sarcoplasm which is the plasma membrane/cytoplasm
Myofibrils
Mitochondria
Nuclei
what are contractile cells and what are myofilaments and the two types
Contractile cells are called muscle fibers and connective tissue holds muscle fibers in parallel groupings (striations)
These fibers of the cytoskeleton have the myofilaments
B. myofilaments
Myofilaments = protein filaments INSIDE of myofibrils
Two types of myofilaments
1. Thin filament → actin
2. Thick filament → myosin
interactduring contracton
what is the sarcomere
The sarcomere is the basic functional unit of contraction
Each myofibril contains 10000 sarcomeres (so a bunch of myofilaments/thin and thick actin)
Each are 2 um at rest
Sarcomeres are separated from each other through dark Z lines
Thick and thin filaments slide past each other (sliding filament model) to contract and requires calcium and ATP
what are all the sarcomere landmarks and striations (lines, bands)
- Z line
- junction of adjacent sarcomeres (the place where two sarcomeres meet), where proteins called actinins hold the thin filaments in place - I band
- light region and thin filaments only (actin) - A band
- dark region, thick filaments (myosin) - Zone of overlap
- area where thick and thin filaments overlap (myosin and actin) - M line
- middle of the sarcomere, thick filaments are anchored here (myosin) - H band
- thick filaments only, visible only when relaxed - M line
- middle of the sarcomere, thick filaments are anchored here (myosin) - H band
- thick filaments only, visible only when relaxed
what is the mechanism of contraciton and why is ATP required
Mechanism of contraction:
Thick and thin filaments slide past each other
Sarcomere shortens
Z lines move closer together
FILAMENTS Don’t shrink, they slide
ATP is required for cross bridge cycling, myosin detachment and energy for the power stroke
what is the sarcolemma and its function
Sarcolemma = muscle fiber plasma membrane
Selectively permeable and maintains charge difference +/-
Nerve impulses causes reversal of change and is 1st step leading to muscle contraction
This electrical changes initiates contraction (where the change in charge is initiated by neuron/nerve cell impulses that spread across the entire sarcolemma)
The action potential spreads across entire fiber
Sarcolemma: the plasma membrane of a muscle fiber that conducts action potentials across the cell to initiate muscle contraction.
