Final: Musculoskeletal System Slides Flashcards by Katrina Paras

Overall function of musculoskeletal systems

Convert electrical activity into force that is used for daily activity

How well did you know this?

Not at all

Perfectly

Neural pathway/cycle

Stimulus - skin receptors - sensory neuron - interneuron - motor neuron - effector (muscle)

How well did you know this?

Not at all

Perfectly

General function of muscles

Excitable cells; receive action potential and act; contractile tissues

How well did you know this?

Not at all

Perfectly

Types of muscle (3)

Skeletal (voluntary), smooth (involuntary - found around organs), cardiac (involuntary)

How well did you know this?

Not at all

Perfectly

Skeletal muscle organization, large to small

Muscle, fascicles (bundles), muscle fibers/cells, myofibrils, sarcomeres

How well did you know this?

Not at all

Perfectly

Myofibrils are ____ proteins

Contractile

How well did you know this?

Not at all

Perfectly

Muscle fiber structure

Bundle of cells within each fascicle, unique cylindrical shape; can extend entire length of muscle

How well did you know this?

Not at all

Perfectly

Sarcomere function

Functional unit of muscle (contraction); combination of different proteins

How well did you know this?

Not at all

Perfectly

What are Z lines?

Network of interconnecting proteins that binds each sarcomere

How well did you know this?

Not at all

Perfectly

What are thick filaments composed of?

Myosin (contractile protein)

How well did you know this?

Not at all

Perfectly

What do thin filaments contain?

Actin (contractile protein), troponin and tropomyosin (both regulatory proteins)

How well did you know this?

Not at all

Perfectly

What is required for force production in sarcomeres?

Interaction (physical contact) between thick and thin filaments

How well did you know this?

Not at all

Perfectly

Composition of myosin molecule

Two heads and two tails

How well did you know this?

Not at all

Perfectly

What does each myosin head (or cross bridge) contain and what does it do?

Actin binding site, ATP binding site; myosin head is where all activity occurs

How well did you know this?

Not at all

Perfectly

Which parts of myosin molecule interact?

Tails (heads don’t interact)

How well did you know this?

Not at all

Perfectly

Function and structure of titin

Very large, thick protein; connects thick filaments to Z lines

How well did you know this?

Not at all

Perfectly

How is actin arranged in thin filaments?

Actin molecules are globular proteins that polymerize to form intertwined helix

What does a thin filament look like at rest?

The myosin binding site is covered by tropomyosin (arranged like a ribbon; it must be removed to allow binding of myosin)

Troponin structure

3 spherical subunits with 3 binding sites: for actin, tropomyosin, and calcium (need it for muscle contraction)

What happens to sarcomere shape during muscle contraction?

Shortens

Besides the proteins in thick/thin filaments, what causes binding of actin and myosin to occur?

ATP (binding site on myosin) and calcium (binding site on troponin)

Where do muscles get energy?

From ATP, since they’re packed with mitochondria (cell respiration, etc.)

Where does calcium come from in muscles?

Stored in sarcoplasmic reticulum (not available in cytosol, bc we don’t want it to depolarize cell all the time)

What is the sarcoplasmic reticulum?

Modified smooth ER, found around myofibrils, lateral sacs release calcium

What is the modified plasma membrane of muscle cells called?

Sarcolemma

Sarcolemma structure

Extensions (invaginations) that dip deep into cytoplasm: these are T-tubulus

T-tubules (transverse tubules) structure and function

Have special voltage sensitive calcium channels called dihydropuridine receptors (DHPR); increase surface area for electrical activity

Where are ryanodine receptors located?

Lateral sacs of sarcoplasmic reticulum

How does activity at the neuromuscular junction start (eventually causing Ca release)?

Action potential reaches axon terminal - voltage gated calcium channels open - Ca2+ influx from extracellular space- NT vesicles move - NT (ACh) released by exocytosis

What is the electrical activity in muscle cells called?

End plate potential (EPP)

What causes calcium release after ACh released?

ACh binds to its receptors on muscle cell to activate them - Na+ enters cell - depolarizes membrane - EPPs accumulate and cause action potential - action potential travels down sarcolemma and dips into T-tubules - activates DHPR on T-tubules - DHPR activates ryanoside receptors - Ca2+ released from SR

Once released, where does Ca go and what happens?

Binds to troponin on actin - tropomyosin uncovers myosin binding site - Myosin and actin bind

Steps of cross bridge cycle (8 steps)

1. ADP and Pi bound to myosin cross bridge 2. Myosin binds to actin once it's exposed 3. Pi unbinds from myosin head 4. Power stroke (muscle contraction) 5. ADP unbinds 6. ATP binds to myosin head 7. Myosin detaches from actin 8. ATP hydrolyzed to ADP and Pi, cycle repeats

Cross bridge cycle: when is it low energy and when is it high energy state?

Low energy: after power stroke to ATP hydrolysis | High energy: after ATP hydrolysis to power stroke

What happens in the power stroke?

Muscle contraction: myosin pulls and "snaps" actin - shortens sarcomere

What stops the cross bridge cycle?

Removing ACh: acetylcholine esterase breaks down acetylcholine Removing Ca2+: calcium pumped back to SR through active transport pumps

Where does muscle cell get energy from (3)?

Creatine phosphate Cellular respiration Glycolysis followed by fermentation

What is creatine phosphate?

Stored form of energy: creatine phosphate + ADP becomes small amount of ATP bound to creatine (in presence of creatine kinase)

What are the two phosphagens and where are they found?

Creatine phosphate: vertebrate animals | Arginine phosphate: invertebrate animals

Advantage/disadvantage of creatine phosphate

Very quick source of energy but only lasts for about a second (then other processes take over)

What causes muscle fatigue?

Local increase of inorganic phosphate Build up of acid (fermentation) Depletion of energy: O2 demand > availability