Muscles Fitz

Question 1

3 functions of skeletal muscles

Answer 1

1. Produces body movements
2. Stabilizes body positions
3. Produces heart (Due to involuntary contractions of skeletal muscles- shivering)

Question 2

5 properties of muscle tissues

Answer 2

Conductivity 
Contractility 
Excitability 
Extensibility
Elasticity

Question 3

Neuromuscular junction

How is it different from the synapse in the CNS?

Answer 3

Motor neuron with axons that extend onto the skeletal muscles.

Unlike the CNS, the post synaptic terminal of the muscle call has deep inholdings that increase the surface area for post-synaptic receptors.

Question 4

Which neurotransmitter is responsible for synaptic connection at the NMJ? What receptor does it bind to?

Answer 4

AcH. It is released and can either bind to a nicotinic (iontropic) or a muscarinic receptor.

Nicotinic (ionotropic) receptors are much faster, which is why they are found in the muscles.

Muscarinic are G protein coupled and slower. They are not found in the muscles.

Question 5

How does the botulinum toxin affect the NMJ

Answer 5

Blocks the release of the acetylcholine neurotransmitter at the NMJ so that muscle contraction cannot occur,
Death occurs due to paralysis of the diaphragm.
Found in improperly canned food.

Question 6

How does curare affect the NMJ

Answer 6

Poison from plants and colorful frogs that eat the plants and then secrete the toxin from their skin.

Causes muscle paralysis by blocking the AcH receptor so that AcH cannot bind.

Used in low levels to relax muscles during surgery.

Question 7

how does Neostigmine affect the NMJ?

Answer 7

Anticholinesterase agent.

Blocks removal of ACh from receptors. Strengths weak muscle contractions of myasthenia graves.

Also an antidote for curare after surgery is complete.

Question 8

Muscle growth is a result of cellular ____, and not cell ___

Answer 8

Enlargement

Division

Question 9

Every mature muscle cell developed from hundreds of ___ that fused together in the fetus.

Answer 9

Myoblasts. This is why skeletal muscle cells are multinucleated.

Question 10

Can mature muscle cells divide?

Answer 10

No

Question 11

Which cells have the ability to regenerate new muscle cells if needed?

Answer 11

Since mature muscle cells cannot divide, satellite cells retain the ability to differentiate if needed.

Question 12

Sarcolemma

Sarcoplasm

Answer 12

Muscle cells membrane.
Cytoplasm of a myofiber. Filled with myofibrils (contractile proteins, regulatory proteins and structural proteins) and myoglobin (red colored due to its oxygen binding property)

Question 13

What is found within the sarcoplasm of a muscle fiber/myofiber?

Answer 13

Myofibrils:

1. Contractile proteins- actin and myosin
2. Regulatory proteins- troponin and tropomyosin
3. Structural proteins- titin to provide alignment and elasticity.

Myoglobin
Has oxygen binding properties that makes it red.

Question 14

Myosin is held in place by which band

Answer 14

M line proteins

Question 15

Titan filament

Answer 15

A structural protein (elasticity) found in myosin that anchors them to the M line. allows the muscle to return to its resting position after being stretched.

Can stretch 4x its resting length and spring back unharmed.

Question 16

How does Ca2+ affect a muscle cell

Answer 16

Calcium binds to troponin, causing the displacement of tropomyosin. This allows the myosin heads to attach too actin.

Question 17

Thin filaments are held in place by which band

Answer 17

Z lines

Question 18

Steps for contraction

Answer 18

1. Nerve impulse reaches axon terminal and vesicles release Ach.
2. Ach diffuses and binds to nicotinic receptors on the sarcolemma. Na+ rushes into the cell and causes depolarization.
3. Action potential spreads over sarcolemma and down the transverse tubules.
4. Sarcoplasmic reticulum releases Ca2+ into the sarcoplasm.
5. Ca2+ binds troponin, causing tropomyosin to move and reveal the myosin binding sites on actin.

Question 19

T tubules are transverse to the ___

Adjacent to them is the ____

Answer 19

They are transverse to the muscle fiber.
They are adjacent to the sarcoplasmic reticulum.

They help extend depolarization deep into the muscle.

Question 20

Rigor mortis

Answer 20

Myosin heads cannot release/unbind from the actin without ATP.

Question 21

4 steps in the contraction cycle

Answer 21

1. ATP hydrolysis
2. Attachment of myosin to actin to form cross bridge
3. Power stroke
4. Detachment

Question 22

Ryanodine receptor

Answer 22

Special molecule that interacts between the T tubules and SR. Initiated by an action potential moving down T-tubule.

Question 23

T tubule can also be called the

Answer 23

Triad, because its associated with 2 sarcoplasmic reticulum. (one on each side of the sarcomere)

Question 24

Receptor on the T tubule that plugs into the sarcoplasmic reticulum’s foot proteins

Answer 24

Dihydropyridine receptor- forms a special type of channel called a ryanodine receptor. Results in the release of Ca2+ from the SR.