muscular system structure and functions Flashcards
What are the 3 types of muscle tissue?
- skeletal muscle
- cardiac muscle
- smooth muscle
What are the general characteristics of skeletal muscle?
- attached to bones of skeleton
- voluntary (consciously controlled)
what are the general characteristics of cardiac muscle?
- makes up most of the wall of the heart
- involuntary
- responsible for pumping action of the heart
What are the general characteristics of smooth muscle?
- found in walls of internal organs, such as those of digestive tract
- involuntary
What are the functions of muscle tissue?
- body movement
- maintenance of posture
- temperature regulation
- storage and movement of materials
- support
what is the structure of skeletal muscle?
composed of:
- skeletal muscle tissue
- nervous tissue
- blood
- CT
What are the actions of skeletal muscle?
- generate a great variety of body movements
- the action of each muscle mostly depends upon:
- the type of joint it is associated with
- the way the muscle is attached on either side of the joint
What are origin, insertion and action?
origin: less moveable end of muscle
insertion: more moveable end of muscle
action: what movement is made
What are the CT coverings over skeletal muscles?
- fascia (dense CT separating individual muscles)
- tendons (cordlike structure connecting muscle to bone)
- aponeuroses (sheet-like structure that is composed of dense CT
- epicranial aponeuroses
- lumbar aponeuroses
- external oblique aponeuroses
- palmer aponeuroses
- linea alba
What are the different muscle structures?
- myofilaments
- myofibrils
- muscle fiber
- fascicle
- muscle
What is endomysium?
- delicate loose CT that surrounds each muscle fiber
- provides the chemical environment for the exchange of ions for nervous stimulation
What is a fascicle?
- is a bundle of muscle fibers covered by a CT sheath
- all of the fascicles together form the entire muscle which is surrounded by a layer of fibrous CT called the epimysium
What is a perimysium?
- sheath of CT that encloses a bundle of skeletal muscle fibers or a fascicle
What is the epimysium?
outer layer of CT surround a skeletal muscle
What is a fascia?
- most superficial layer of CT and is continuous with the epimysium and serves to separate individual muscles
what are thick and thin filaments?
- structures containing the contractile proteins actin and myosin
- intracellular
What is a myofibril?
- overlapping parallel groups of thick and thin filaments in a repeating pattern; underlying basis for the striation pattern
- intracellular
What is the structure of a muscle fiber?
- a single muscle cell, multinucleate and may be many centimeters long
- within a muscle, surrounded by a layer of CT called endomysium
what is the structure of a fascicle?
- a bundle of muscle fibers within a muscle
- within a muscle, surrounded by a layer of CT called perimysium
what is the structure of a muscle?
- a bundle of fascicles
- surrounded by a layer of CT called epimysium and in some cases an additional layer called muscle fascia
What is a muscle compartment?
- is the space that contains a particular group of muscles, blood vessels, and nerves
- all tightly enclosed by fascia
What is the structure of a skeletal muscle fiber?
- contains numerous myofibrils
- each consist of repeating units called sarcomeres
- the characteristic striations of a sarcomere reflect the organization of actin (thin) and myosin (thick) filaments
What do the skeletal muscle striations result from?
- repeating pattern of units called sarcomeres that are within each muscle fiber
- myofibrils are essentially sarcomeres joined end to end
what is a sarcomere?
- structural and functional unit of a myofibril
- muscle fibers and muscles themselves may be thought of as collections of sarcomeres
how is skeletal muscle composed?
- layers of CT
- fascia covers the surface of the muscle
- epimysium lies beneath the fascia and is continuous with the periosteum of the bone/tendons
- perimysium extends into the structure of the muscle where it separates fascicles
- endomysium separates individual muscle fibers
What does muscle fiber consist of?
- is a single elongated cell surrounded by a plasma membrane, known as the sarcolemma
- each muscle fiber contains multiple nuclei that are found just beneath the sarcolemma
- threadlike structures called myofibrils extend the length of the fiber and dominate its interior
- myofibrils are unique to muscle and are composed of two kinds of protein filaments - actin (thin) and myosin (thick) myofilaments
How are actin and myosin myofilaments organized?
- in a contractile unit called a sarcomere
- the sliding of these filaments along each other shortens the sarcomere
- this results in movement of the skeleton
What is an aponeurosis?
- sheet of CT that attaches muscles to bone, skin, and other muscles
What is a compartment?
- a space that contains a particular group of muscles, blood vessels, and nerves
- all tightly enclosed by fascia
What is the network of fasciae that surrounds muscles?
- deep fascia
- is continuous with the subcutaneous fascia that lies beneath the skin
- also is continuous with the subserous fascia that forms the CT layer of the serous membranes covering organs in various body cavities and lining those cavities
What is a skeletal muscle fiber?
- single muscle cell
- each fiber forms from many undifferentiated cells that fuse during development
- the result is a multinucleate muscle fiber that is thin, elongated and cylindrical with rounded ends that attach to the CT associated with the muscle
- beneath the cell membrane (sarcolemma) the cytoplasm (sarcoplasm) of the fiber contains many small, oval nuclei and mitochondria
What is contained within the sarcoplasm?
- abundant long, parallel structures called myofibrils
what does striation result from?
- repeating pattern of units called sarcomeres (structural and functional unit of a myofibril)
- the myofibrils are essentially sarcomeres joined end to end
- muscles can be thought as a collection of sarcomeres and are the functional units of muscle contraction
What are the 2 main parts of muscle striation?
- I bands (the light bands)
- A bands (the dark bands)
What are I bands composed of?
- thin action filaments held by direct attachments to structures called Z lines which appear in the center of the I bands
What do A bands consist of?
- composed of thick myosin filaments overlapping thin actin filaments
- also consist of a slightly lighter central region (H zone)
- H zone consists of only thick filaments
- also includes a thickening known as the M line that consists of proteins that help hold the thick filaments in place
- the myosin filaments are held in place by the Z lines and are attached to them by a large protein called TITIN
What does a sarcomere extend from?
- from one Z line to the next
What is myosin composed of?
- two twisted protein strands with globular parts called heads that project outward along their lengths
What is actin composed of?
- consist of double strands of actin twisted into a helix
- actin molecules are globular, and each has a binding site to which the heads of a myosin molecule can attach
What are the 2 regulatory proteins that are associated with actin filaments?
- troponin and tropomyosin
what do troponin molecules consist of?
- has three protein subunits and are attached to actin
What do tropomyosin molecules consist of?
- are rod-shaped and occupy the longitudinal grooves of the actin helix
- each tropomyosin is held in place by a troponin molecule, forming a troponin-tropomyosin complex
What is the sarcoplasmic reticulum?
- a membranous network of channels and tubules in a muscle fiber, corresponding to the smooth endoplasmic reticulum of other cells
What are transverse tubules?
- a set of membranous channels (T tubules) that extend into the sarcoplasm as invaginations continuous with the sarcolemma and contains extracellular fluid
- lies between two enlarged portions of the sarcoplasmic reticulum called cistern
What is cisternae?
- enlarged portion of the sarcoplasmic reticulum near the actin and myosin filaments of a muscle fiber
what do the sarcoplasmic reticulum, T tubules and cisternae form?
- a triad near the region where the actin and myosin filaments overlap
what do the sarcoplasmic reticulum and T tubules participate in?
- activating muscle contraction once a muscle fiber receives stimulation via a nerve impulse
