Muscle structure and function Flashcards
3 types of muscle tissue
skeletal, cardiac, smooth
cardiac muscle
found in heart responsible for circulating blood, small cells, and very limited ability to repair, involuntary contraction,s single nucleus in a cardiac muscle cell
skeletal muscle
multinucleated, larger muscle, very large muscle cells (up to 30cm), partially repair, under voluntary control
smooth muscle
found in walls of organs, single nucleus, can divide and repair itself if damaged, involuntary
3 layers of muscle connective tissue
epimysium (round the entire muscle), perimysium (divides the muscle into small bundles- fasciculus), endomysium (around an individual cell)
what is a muscle cell also known as
a muscle fiber
functions of muscle tissue
produce body movement, stabilizes body position, regulates organ volumes, movement of substances in the body, produce hear
how do muscles regulate organ volumes
bands of smooth muscles called sphincters control this
how do muscle tissues produce heat
involuntary contractions of skeletal muscle (shivering)
productions of muscle tissue
excitability, conductivity, contractility, extensibility, elasticity
productions of muscle tissue- excitability
response to chemicals released from nerve cells
productions of muscle tissue- conductivity
ability to propagate electrical signals over membrane
productions of muscle tissue- contractility
ability to shorten and produce force
productions of muscle tissue- elasticity
ability to return to original shape after being stretched
Skeletal muscle tissue- attachment
attaches to bone, skin or facia (the skeletal system), maybe via tendons/ aponeuroses)
Skeletal muscle tissue- striations
striated with light and dark bands visible with scope (due to proteins in muscle cells)
Skeletal muscle tissue- multinucleated
due to development muscles are formed by multiple myoblasts that don’t fuse, these then become the satellite cells- stem cells, when damage to muscle they can divide and assist repair
functions of skeletal muscle
produce skeletal movement, maintain body position, support soft/ hard tissue, guard body openings (sphincters), maintain body temp, stores nutrients reserves, role in proprioception
skeletal muscle structures
connective tissues, nerves, blood vessels, muscle tissue
Connective tissue layers- epimysium
outer layer- surround the whole muscle, exterior collagen layer, connected deep to fascia, separates muscle from surrounding tissues, fibrous irregular connective tissue
Connective tissue layers- perimysium
middle layer- surrounds muscle fibre bundles (fascicles), contains blood vessels and nerve supply to fascicles, made of more elastic fibres (half collagen and half elastin)
Connective tissue layers- endomysium
inner layer- surrounds individual muscle cells (muscle fibres), contains capillaries and nerve fibres contracting muscle cells, contains satellite cells that repair damage, more elastic fibres
when do endomysium, perimysium and epimysium come together
at ends of muscles, to form connective tissue attachment to bone matrix e.g. tendon
Skeletal muscle structures- nerve
skeletal muscles are voluntary muscles controlled by nerves of the central nervous system, peripheral nerves, a collection of muscle cells is supplied by a motor neurone (muscle nerve), each muscle cell is supplied by a terminal branch of motor neurone
The sarcolemma
the cell membrane of a muscle cell, surrounds the sarcoplasm (cytoplasm of muscle), sarcoplasm is filled with tiny threads called myofibrils, and myoglobin (oxygen binding protein), a change in transmembrane potential begins contraction
transverse T- tubules
they are invaginations of the sarcolemma into the centre of the cell, filled with extracellular fluid, carry muscle action potentials down into cell, allow the entire muscle fibre to contract simultaneously
transverse T- tubules- mitochondria
they lie in rows throughout the cell, near the muscle proteins that use ATP during contraction
What is a motor unit
one motor nerve and the muscle fibre it supplies
skeletal muscle fibres
are long and cylindrical, develop through fusion of mesodermal cells (myoblast), become very large, contains hundreds of nuclei, nuclei arranged around periphery of cell, contains many mitochondria- lots of energy
Skeletal muscle structures- blood vessels
each muscle cell is in contact with 1 or.2 capillaries, nerve fibres and capillaries are found in the endomysium between individual cells, need large blood supply- lots of energy
why do muscles have extensive vascular systems
supply large amounts of oxygen, supply nutrients, carry away waste products
what is a sarcoplasmic reticulum (SR)
a membranous structure surrounding myofibrils, systems of tubular sacs similar to smooth endoplasmic reticulum in non- muscle cell, forms chambers at each end (terminal cisternae), attached to T- tubules
role of sarcoplasmic reticulum
helps to transmit action potentials to the myofibril, stores calcium ion
when is a triad forms
it is formed by 1 T- tubercle and 2 terminal cisternae
what do terminal cisternae do
concentrate Ca+ (via ion pumps)
release Ca++ into sarcomeres begin muscle contractions
myofibrils and myofilaments
muscle fibres are filled with threads called myofibrils separated by SR, myofibrils are made up of bundles of protein filaments= myofilaments, myofilaments (thick and thin filaments) are the contractile proteins of muscles
myofilaments and the sarcomere- I band
contains only thin filaments (actin), appears light
myofilaments and the sarcomere- A band
contains thick (Myosin) and thin filaments
myofilaments and the sarcomere- overlap reigion
in the overlap region of the A band, 6 thin filaments surround each thick filament- zone of overlap
myofilaments and the sarcomere- filaments compartment
filaments are arranged in compartments= sarcomeres, separated by Z discs
myofilaments and the sarcomere- M lie
myosin thick filaments attach to the M line
myofilaments and the sarcomere- Z line/ discs
shaped like a Z, actin attaches here
what is titin
titin is a muscle protein that is important in eccentric muscle contraction- attaches myosin filament to M line- helps muscles return to normal size and shape
what is sarcomere
contractile unit of muscle, structural units of myofibrils, forms visible striated patterns within myofibrils, transverse tubules encircle sarcomeres near zones of overlap, Ca++ released by the SR causes thin and thick filaments to interact
