lecture 16 Flashcards
what are the three types of muscle
cardiac, skeletal, and smooth
cardiac muscle
specialized for pumping blood
skeletal muscle
specialized for rapid and voluntary contraction and relaxation
smooth muscle
specialized for slow involuntary control can contract for long periods without fatigue ; most efficient use of ATP
how do all muscles function
they generate a “pulling” forces by the same sliding filaments mechanism
muscles are made up of what two things
thin and thick filaments
thin filaments have
actin (rope)
thick filaments have
myosin (person pulling the rope) myosin does the pulling
actin and myosin mediate what
cell division, cell motility, and organelle transport in many cell types
the organization of actin and myosin give the muscle what
a striated (striped) look
what two muscles are striated
cardiac and skeletal
skeletal muscle cells are
large and multinucleated made up of organized contactile fibers
what other two molecules are attached to myosin and actin
troponin and tropomyosin
troponin
binds to tropomyosin to position it on actin and get it ready to move
tropomyosin
blocks myosin binding sites on actin
what is the process of contraction
- myosin binds to actin molecule 2. myosin pulls structure of actin molecules 3. myosin then detaches to let structure return to original form 4. myosin binds again to actin to repeat
what plays a big role in contraction
atp
what shifts myosin to cocked position
atp hydrolysis
what initiates the power stroke (contraction)
myosin binding actin
atp is needed when
to bind to actin and to unbind from actin
what is the contractile unit of skeletal muscle and cardiac
sarcomere
the fundamental unit of muscles
sarcomere
z-line
where sarcomere ends and where actin is bound (end)
m-line
middle; where thick filaments (myosin) are bounded
A-band
includes ALL of the myosin band
I-band
region of just actin
H-band
region of just myosin
when muscle is contracted what locations are shortened
I and H bands will get smaller as myosin and actin pull on each other bringing the z lines together, the overlapping region is huge
how do muscles coordinate
through stimulation from the somatic nervous system
what regulates almost all muscle contractions
neurons
skeletal contractions are usually controlled
consciously
each muscle cell is innervated by
one neuron but one neuron can innervate multiple muscle cells
one motor neuron+ all of the muscle cells it innervates
one motor unit
neurons talk to muscle cells through
neuromuscular junctions
steps for neuron to muscle cell communication
- AP reaches end of axon 2. voltage gates calcium channels open 3. calcium stimulates synaptic vesicle fusion with presynp membrane 4. ACH is released and binds to ligand gated channels on muscle 5. sodium enters muscle causing depolarization and contraction signal 6. muscle signal spreads through muscle cell via voltage gated channels
steps for any other synapse
- AP reaches end of axon 2. voltage gates calcium channels open 3. calcium stimulates synaptic vesicle fusion with presynp membrane
AP spreads deep within cell to each
myofibril
t tubules
extensions of cell membrane that penetrate into the centre of skeletal and cardiac muscle cells
t tubules run close to what
sarcoplasmic reticulum
sarcoplasmic reticulum
modified endoplasmic reticulum that is designed for calcium storage
how do AP run deep into multiple muscle cells
- AP leads to opening of voltage gated calcium channels 2. diffusion from sarcoplasmic reticuluminto cytoplasm 3. calcium binds to troponin which then exposes myosin binding sites by moving tropomyosin
two things needed for contraction
ATP and calcium
simplified list of muscle molecule movement
ca2+ binds troponin -> tropomyosin shifts -> exposes myosin binding sites
