Muscles

Question 1

What are the characteristics of muscle tissue?

Answer 1

Excitability
Contractility
Extensibility
Elasticity

Question 2

What is excitability?

Answer 2

The ability to receive and respond to stimulus

Question 3

What is contractility?

Answer 3

The ability to produce tension/force when stimulated

“Shortening”

Question 4

What is extensibility?

Answer 4

The ability to be stretched, “lengthen”

Question 5

What is elasticity?

Answer 5

The ability to recoil to resting length

Question 6

What are the functions of muscle tissue?

Answer 6

Movement of bones or fluids
Maintaining of posture and body position
Stabilizing joints
Heat generation (esp. true for skeletal)

Question 7

What is the difference between skeletal muscles and cardiac and smooth muscles as far as nerve impulses?

Answer 7

Skeletal muscles are voluntary
Cardiac/Smooth muscles are involuntary

Question 8

True or False: Skeletal muscles regenerate after being “torn” during exercise.

Answer 8

False. We are born with a set number and that’s how many we have

Question 9

What is unique about the structure of cardiac muscles?

Answer 9

They are branched and connect to each other in chains

Question 10

What is the epimysium?

Answer 10

The top, dense layer of connective tissue covering everything

Question 11

What are fascicles?

Answer 11

Groups of muscle tissue fibers connected together

Question 12

What is the perimysium?

Answer 12

The connective tissue holding fascicles together

Question 13

What is sarcolemma?

Answer 13

The special name for the plasma membrane of muscle cells

Question 14

What is a myofibril?

Answer 14

A stack of fibrous muscle cells (sarcomeres) within the sarcolemma.

This organelle is unique to skeletal muscles

Question 15

What is a sarcomere?

Answer 15

The smallest prt of a myofibril

An A-Band (stacks of overlapping actin and myosin*)between two protein “caps” called Z-Discs.

The middle space between two z-discs is just myosin, this is called the M-line

Question 16

Which protein is a thin filament and which is a thick filament?

Answer 16

Actin: Thin
Myosin: Thick

Question 17

The thin membrane coating each myofibril is called what?

Answer 17

Sarcoplasmic Reticulum

Question 18

What is a Triad?

Answer 18

1 T-tubule aka Transverse tubule of sarcolemma around 2 terminal cisternae storing Ca2+

Question 19

What are the “contractile proteins”

Answer 19

Actin and myosin

Question 20

What is the difference between troposin and tropmyosin?**

Answer 20

Tropomyosin covers actin and myosin heads bind to it

Troponin covers tropomyosin. When it binds to Ca2+ it changes its shape, revealing the active sites

Question 21

Where does activation happen and what is that?

Answer 21

In the motor end plate

A stimulation (AP) travels down a neuron to a neuromuscular junction.

ACh is released into the sarcolemma via exocytosis

Question 22

What is a neuromuscular junction?

Answer 22

A muscle synapse: the place where a muscle neuron’s synaptic bulb meets the motor end plate

Question 23

Where does excitation take place, what is it?

Answer 23

In the muscle membrane (sarcolemma)

The membrane is depolarized, ACh binds to receptors on motor end plates and opens ligand-gated channels, allowing Na+ in and K+ out

This depolarization opens voltage-gates Na+ channels, which causes an AP that changes the shape of T-tubules

The sarcolemma receives an influx of Ca2+, which binds to troponin and exposes the active sites on actin

Note: This is always a nicotinic receptor, EPSP

Question 24

What happens during Excitation-Contraction?

Answer 24

ATP provides energy for mysofilaments to slide together. Myosin heads bind to actin and shorten the sarcomere.

A second ATP causes the mysosin head to unlatch

Question 25

What is the latent period?

Answer 25

The time between excitation and depolarization

Question 26

What is the Cross-Bridge Cycle?

Answer 26

Energized myosin heads attach to actin, this is called the “working stroke” or “power stroke”

The myosin head is cocked back by a second ATP molecule

Note: This will happen as long as ATP and Ca2+ are present

Question 27

What is meant by muscle relaxation?

Answer 27

Ca2+ is pumped back into the SR, tropomyosin rolls back over and covers the binding sites of actin

Question 28

What is rigor mortis?

Answer 28

When a person dies the stored Ca2+ in their terminal cisternae flood the sarcolemma and the ATP still left in their system causes all the myosin to keep cocking forward and contracting until it runs out

Question 29

What is the difference between isometric and isotonic contractions?

Answer 29

Isometric - Tension is constant but muscle length stays the same

Isotonic - Muscle length changes the same but tension remains the same

Question 30

What is tension

Answer 30

The force exerted on the load of an object, created by contraction

Question 31

True or False: contraction means the muscle shortens

Answer 31

False. In concentric contractions the muscle shortens, in eccentric contractions the muscle grows in length

Question 32

What is a motor unit?

Answer 32

A single motor neuron and the muscle fibers it supplies

Question 33

What parts of the body have more motor end units?

Answer 33

Fingers, lips, etc.
Areas where fine, precise motor control is more important

Question 34

What parts of the body have large motor units?

Answer 34

Thighs, back, anywhere that is weight-bearing

Question 35

What is the definition if a muscle twitch?

Answer 35

The response if a muscle to a single, brief threshold stimulus.

It is the simplest contraction observable in a lab

Question 36

What are the three phases of a muscle twitch?

Answer 36

Latent Period - E-C Coupling
Period of Contraction - Cross-Brudge formation, increasing tension
Period of Relaxation - Ca2+ re entering SR, tension declines to 0