Muscles Flashcards
What are the three types of muscle tissue?
1) skeletal muscle
2) cardiac muscle
3) smooth muscle
what functions does muscle contraction have?
1) body movement
2) stabilization of body position
3) movement of substances through the body
4) generating heat to maintain body temperature
what type of muscle is skeletal muscle?
voluntary - control it consciously
- it connects one bone to another . muscle is not att directly to the bone, its att via a tendon
How do muscles work in groups?
agonist (muscle resp for movement) contracts while the antagonist stretches.
when the antagonist contracts, the bone move into opp direction , stretching the agonist!
there are also synergistic muscles- assist the agonist by stabilizing the original bone
what else can contraction of skeletal muscle cause?
- squeeze blood and lymph vessels aiding in circulation
- also produces heat
what is the smallest functional unit of skeletal muscle?
sarcomere
what is a sarcomere made of?
many strands of two protein filaments (thick and thin filaments)
sarcomere are laid side-side to form myofibril. each myofibril is surrounded by specialized endoplasmic reticulum of the muscle cell called the sarcoplasmic reticulum. a modified mem called sarcolemma wraps several myofibrils together to form muscle cell or muscle fibre.
Sarcoplasmic reticulum..
lumen is filled with calcium ions .
skeletal muscle is ____ nucleate
multi
what is the thick filament of a sarcomere made of ?
protein myosin
What is the thin filament composed of?
actin (globular protein)- attatched to the actin are proteins troponin and tropomyosin
How does contraction of the skeletal muscle occur?
myosin and actin work together sliding alongside each other to create the contractile force of skeletal muscle.
each myosin head crawls along the actin in a 5 stage cycle.
what are the 5 stages of contraction?
1) tropomyosin covers an active site on actin - that prevents myosin head from binding. the myosin head remains cocked in a high energy position with a phosphate and ADP group att
2) in presence of ca2+, troponin pulls tropomyosin back , exposing active site, allows myosin head to bind to the actin
3) the myosin heads expels the phosphate and ADP and it bends into a low energy position , dragging the actin along with it ( this is called the power stroke bc it causes shortening of sarcomere and muscle contraction)
4) ATP attaches to the myosin head, this releases myosin head from the active sire, which is covered immediately by the tropomyosin
5) ATP splits into inorganic phosphate and ADP causing myosin head to cock into high energy position .
what does the muscle contraction begin with?
action potential
- a neuron attaches to a muscle cell forming a neuromuscular synapse. the action potential of a neuron will release acetylcholine- which activate ion channels in sarcolemma of muscle cells , creating an action potential.
which moves deep into muscle via small tunnels called t tubules.
what do the t tubules allow?
uniform contraction of muscle by allowing the action potential to spread through the muscle cell more rapidly
the action potential is spread through the muscle cell more rapidly. The action potential is transferred to the sarcoplasmic reticulum, which suddenly becomes permeable to calcium ions. the calcium ions begin 5 stage cycle . at the end of the cycle, calcium is actively pumped back into sarcoplasm reticulum
what is a motor unit?
a motor unit consists of a nerve and all muscle fibres that synapse with the nerve
- motor units are independent of each other .
- force of contracting muscle depends upon number and size of active motor units and the freq of action potentials in each neuron of motor units
- smaller motor units work faster compared to bigger ones
what are the THREE type of skeletal muscle fibres?
1) slow oxidative type (type 1)
2) fast oxidative type (type 2 a)
3) fast glycolytic type (type 2 b) fibers
type 1 - slow oxidative type
red from large amount of myoglobin - which an oxygen storing protein (myoglobin has 1 subunit)
- therefore have large amounts of mitochondria- they split ATP at a slow rate- so they are slow to fatgiue, but also have a slow contraction speed
type 2 a - fast oxidative fibers
also red ! but they split ATP at a higher rate! these contract rapidly, these are resistance to fatigue but not as resistance then type 1
type 2 b - fast glycolytic fibers
low myoglobin content, appear WHITE ! contract very rapidly
they have large amount of glycogen
do muscle cells undergo mitosis?
human muscle cells are very speacilized - lost ability to undergo mitosis
what does myoglobin do?
stores oxygen inside muscle cells. - its one subunit ! - so stores one oxygen molecule
cardiac muscle is started like…
skeletal muscle
started muscles (cardiac and skeletal ) are striated bc …
they have sarcomeres!
cardiac muscle unlike skeletal muscle has…
one nucleus.. and is separated from its neighbour by an intercalated disc
what do the intercalated discs have?
gap junctions- which allow action potential to spread from one cardiac cell to the other via electrical synapses
cardiac muscle is…
involuntary
the action potential of cardiac muscle exhibits a plateau after …
depolarization ! this plateau is created by slow voltage gated Ca channels which allow calcium to enter and hold the inside of the membrane at a positive potential difference. the plateau lengthens the time of contraction
without the calcium …
heart would beat too fast and we would die
Smooth muscle is involuntary therefore its innervated by the …
autonomic nervous system
smooth muscle has one nucleus like…
cardiac muscle! skeletal muscle has many nuclei
smooth muscle also has thick and thin filaments ..
but they are not organized into sarcomeres.
smooth muscle has intermediate filaments… what do the intermediate filaments do?
intermediate filaments are attatched to dense bodies spread through the cell. the thick and thin filaments are attatched to the intermediate filaments and when they contract the intermediate filaments will pull the dense bodies together.
what are the two types of smooth muscles?
1) single unit
2) multi unit
what is the single unit smooth muscle called?
visceral- most common type! - found in small arteries and veins, the stomach, intestines, uterus, urinary bladder
in addition to responding to neural stimulus , smooth muscle also contracts or relaxes in presence of…
hormones, changes in ph, O2, CO2 levels, temperature and ion concentrations
