Chapter 9 - Muscles and Muscle Tissue Flashcards
Functions of Muscles (PMSGS)
A. Producing movement – skeletal muscle – is responsible for locomotion and manipulation; cardiac muscle – movement of the heart; smooth muscle – moves blood and food stuff
B. Maintaining posture – due to skeletal muscle it continuously makes movements to help counteract gravity
C. Stabilizing joints – when muscles causes movement it strengthens joints
D. Generating heat – as they contract they generate heat, this heat maintains normal body temperature
E. Skeletal - It protects internal viscera organs; smooth muscle forms valves that regulate the passage of substances through body openings, it dilates and constricts the pupils, it also forms elector pili muscles.
Properties of Muscle Tissue (ECEE)
A. Excitability – ability of muscle tissue to receive and respond to a stimulus
B. Contractility – ability to shorten forcibly when adequately stimulated
C. Extensibility –ability to be stretched or extended
D. Elasticity – ability of muscle to recoil and resume its resting length after being stretched
Types of Muscle Tissue: Skeletal
- Location – attached to bones; fibers are the longest muscle cells and many come together to form a fascicle; many muscle fascicles make up a muscle (muscle fibers are the cell). Attached to and covering the boney skeleton
- Appearance – long stripes called striated appearance, longest muscle cells
- Control – voluntary control; responsible for overall body mobility
Types of Muscle Tissue: Cardiac
- Location – walls of the heart, body’s blood pump, it makes up most of the heart walls
- Appearance – striated appearance
- Control – involuntary control; it contracts at a very steady rate which is controlled by a pacemaker
Types of Muscle Tissue: Smooth
- Location – hollow visceral organs (stomach, urinary bladder, repertory passages, and blood vessels)
- Appearance – smooth and no striations
- Control – involuntary control
Skeletal Muscle: Muscles as Organs
- Nerve supply – each muscle has nervers, they will enter and exit through the central part of the muscle and branch profusely though the connective tissue sheath
- Blood supply – enters and exits through a central part, has a rich blood supply because it needs a rich blood supply (O2 and nutrients). Some muscles have more than 1 venues drainage
- Epimysium – aka the overcoat of the muscle – which is made up of dense irregular connective tissue, it surrounds the entire muscle
- Attachments – how the muscle comes in contract with the bone
a. Direct attachments – when the epimysium is fused to the periosteum or perichondrium (muscle is directly attaching to bone)
b. Indirect attachments – muscle’s connective tissue wrapping extend beyond the muscle either as a ropelike tendon or as a sheet like aponeurosis
Skeletal Muscle: Fascicles
Groups of muscle fibers within skeletal muscles (muscle cells) and they resemble bundles of sticks
1. Perimysium – layer of fibrous connective tissue that is found surrounding each
Skeletal Muscle: Muscle Fibers
Each fiber is a long cylindrical cell with multiple nuclei
1. Endomysium – each individual muscle fiber is surrounded by a fine sheath of connective tissue consisting of areolar and reticular fibers. (Within muscle) 2. Sarcolemma – plasma membrane outside covering of the cell, beneath the endomysium 3. Nuclei – multiple oval shaped nuclei, found just beneath the sarcolemma 4. Sarcoplasm – of a muscle fiber is similar to the cytoplasm of other cells, but it contains unusually large amounts of gylcosomes and myoglobin
Skeletal Muscle: Muscle Fibers - Sarcoplasm
a. Glycosomes – granules of stored glycogen and provide glyocose during periods of activity
b. Myoglobin – a red pigment that stores oxygen and is similar to hemoglobin
c. Myofibrils – rod like elements that come together to help form a muscle fiber
Skeletal Muscle: Muscle Fibers - Sarcoplasm; Myofibrils - Striations
i. Striations – they are created by myofibrils, they are repeating series of dark (A band – thick) and light bands (I bands – thin bands)
A. A band – dark bands, thick lines
1. H zone – lighter mid region area where filaments don’t overlap (middle of A band)
2. M line – line of protein known as myomesin – holds adjacent thick filaments together
B. I band – light band, thin lines
1. Z disc – coin like sheet of proteins that anchor the thin filaments and connect myofibrils
Skeletal Muscle: Muscle Fibers - Sarcoplasm; Myofibrils - Sarcomeres
Smallest contractile unit of a muscle fiber (functional unit) area between two Z discs, compose of thick and thin myofilamnets that are made of contractile protiens
Skeletal Muscle: Muscle Fibers - Sarcoplasm; Myofibrils - Myofilaments - Thick Filaments
Thick filaments – consist of protein myosin, they extend the entire length of the A band
- H zone – lighter mid region area where filaments don’t overlap (found in the middle of A band)
- M line – line of protein holds adjacent thick filament together
- Myosin – protein that assist in movement, it has a tail (2 woven heavily polypeptide chains), heads contain 2 smaller lighter polypeptide chains which act as cross bridges during contraction (contain binding sites for actin and ATP)
Skeletal Muscle: Muscle Fibers - Sarcoplasm; Myofibrils - Myofilaments - Thin Filaments
Thin filaments – twisted double strains of fibrous proteins that are called F actin – consists of many G actin subunits
- Z disc – found in the midline of the I band
- Actin – G actin – kidney shaped polypeptides that bear or contain active sites to which myosin heads attach to during contraction
- Tropomyosin – rod shaped regulatory protein found spiraling about the actins chord
- Troponin – another protein related to the thin filament, it has a globular 3 polypeptide complex structure, 1 polypeptide is inhibitory (TnI) another polypeptide binds to tropomysoin which helps positin it to actin (TNT) the last polypeptide binds calcium (TnC)
Skeletal Muscle: Muscle Fibers - Sarcoplasm; Myofibrils - Myofilaments - Sliding Filament
In the relaxed state thick and thin filaments overlap slightly; however during contraction after a nervous stimulation the myosin heads bind to actin, it detaches and binds again to propel the thin filaments toward the M line completely; h zone, I band and distance between the two Z discs shortens, the whole muscle shortens
Skeletal Muscles: Sarcoplasmic Reticulum
Is an elaborate smooth endoplasmic reticulum that’s found surrounding each myofibril, it regulates intracellular ionic calcium concentration
i. Terminal cisternae – aka end sacs these are large perpendicular cross channels at the AI band junction
