Mod 7 (ch7) Flashcards
major functions of the muscular system
- movement of the body
- maintenance of posture
- respiration
- production of body heat
- communication
- constriction of organs and vessels
- contraction of the heart
skeletal muscle (factors)
Location - attached to bones
Cell shape - long, cylindrical
Nucleus - multiple, peripherally located
Striations - yes
Control - voluntary and involuntary (reflexes)
Function - body movement
Smooth muscle (factors)
Location - walls of hollow organs, blood vessels, and glands
Cell shape - spindle-shaped
Nucleus - single, centrally located
Special cell to cell attachments - gap junctions join some smooth muscle cells together
Autorhytmic - yes (some smooth muscle)
Control - involuntary
Function - moving food through digestive tract, emptying the urinary bladder, regulating the blood vessel diameter. contracting many gland ducts
cardiac muscle (factors)
Location - heart
Cell shape - branched, cylindrical
Nucleus - single, centrally located
Special cell to cell attachments - intercalated disks
Striations - yes
auto rhythmic - yes
Control - involuntary
Function - pumping blood; contractions provide the major force for propelling blood through blood vessels
4 major function characteristics of muscle tissues
- contractility
- the ability of muscle to shorten forcefully, or contract - excitability
- the capacity of muscle to respond to a stimulus - extensibility
- means that a muscle can be stretched beyond its normal resting length and still be able to contract - elasticity
- is the ability of muscle to recoil to its original resting length after it has been stretched
skeletal muscle - contractility
skeletal muscle contraction causes the structures to which they are attached (such as a bone) to move
smooth muscle - contractility
smooth muscle contraction increases pressure inside hollow organs, such as the intestines
cardiac muscle - contractility
cardiac muscle contraction increases pressure inside the heart
skeletal muscle - excitability
the stimulus to contract is from nerves that we consciously control
smooth and cardiac muscle - excitability
smooth and cardiac fibres contract spontaneously but also receive involuntary neural signals and hormonal signals to modulate force or rate of contraction
skeletal muscle
when associated w connective tissue, constitutes approx 40% of body weight
- also called striated muscle
- consists of: skeletal muscle tissue, nervous tissue, connective tissue, and adipose tissue
- each muscle cell is called a muscle fibre
what are the 3 layers of connective tissues in skeletal muscles?
- epimysium
- perimysium
- endomysium
epimysium
forms a connective tissue sheath that surrounds each skeletal muscle
- separate the muscles from nearby structures
perimysium
subdivides each whole muscle into numerous, visible bundles of muscle fibres (cells) called fascicles
- loose connective tissue serving as passageways for blood vessels and nerves that supply each fascicle
endomysium
is a delicate layer of connective tissue that separates the individual muscle fibres within each fascicle
- serves as passageway for nerve fibres and blood vessels that supply each separate muscle fibre
tendons
the protein fibres of the 3 layers of connective tissues blend into one another and merge at the ends of most muscles to form tendons, which attach muscle to bone
striated
alternating light and dark bands give the muscle fibre a striated, or striped appearance
2 main aspects to muscle contraction
- electrical component
- mechanical component
electrical component - 3 muscle fiber components that respond to and transmit electrical signals
- sarcolemma
- cell membrane of muscle fibres - transverse tubules
- tubelike inward folds of the sarcolemma
- carry electrical impulses into the centre of the muscle fibre so that the muscle fibre contract as a whole - sarcoplasmic reticulum
- highly specialized smooth endoplasmic reticulum in skeletal muscle fibres that stores high levels of Ca2+
mechanical component structure - contractility is due to 2 main structures in muscle fibers
- myofibrils
- bundles of protein filaments
- its the protein filaments in the myofibrils that interact to shorten the muscle fibre during contraction - myofilaments
Two types of myofilaments: - actin myofilaments or thin filaments
- myosin
- both arranged in ordered units called sarcomeres this is the structural and functional units of skeletal muscles
sarcomeres
Smallest portion of a muscle that can contract
- Z disks are the anchor for actin myofilaments
3 regions:
1. two lighter-straining regions called I bands
2. central darker-staining region, called an A band
- each A band contains actin and myosin myofilaments overlapping, except in the centre b/c that is called the H zone which only contains myosin myofilaments (thick filaments)
- the middle of the H zone has a dark line called the M line, which consists of delicate protein filaments that hold the myosin filaments in place
actin myofilaments is composed of which 3 proteins?
- actin
- tropomyosin
- in a relaxed muscle, this is covering the attachment sites on the actin
- a muscle cannot contract until the tropomyosin moves to uncover the active sites - troponin
- consists of 3 subunits: 1: anchors the troponin to the actin, 2: subunit that prevents the tropomyosin from uncovering the actin attachment sites in a relaxed muscle, 3: subunit that binds Ca2+
myosin myofilaments
composed of elongated myosin molecules which consist of a rod portion and 2 myosin heads
myosin heads 3 properties:
1. heads bind to active sites on the actin molecules to form cross-bridges to contract the muscle
2. the heads are attached to the rod portion that bends and straightens during contraction
3. heads break down ATP for contraction
muscle fibre and motor neurons
each muscle fibre is in contact w a branch of a motor neuron axon from the brain or spinal cord, these motor neurons carry electrical signals (action potentials) which cause action potentials in the muscle fibre and then muscle contraction happens
