CH 11 Lecture Exam Study Guide

Question 1

What are the 5 characteristics of muscle cells?

Answer 1

Contractibility, elasticity, extensibility, excitability, and conductivity.

Question 2

Define contractibility.

Answer 2

Ability to shorten.

Question 3

Define elasticity.

Answer 3

Ability to recoil back to original length.

Question 4

Define extensibility.

Answer 4

Ability to stretch far without breaking.

Question 5

Define excitability.

Answer 5

Responds to stimulus with a local electrical change.

Question 6

Define conductivity.

Answer 6

Ability to transfer nerve impulses along membrane.

Question 7

What is stored in glycogen.

Answer 7

Stored glucose/ ATP.

Question 8

What is stored in myoglobin.

Answer 8

Binds and stores oxygen, used to make ATP.

Question 9

Describe sarcoplasm and state its role in muscle contraction.

Answer 9

Cytoplasm of muscle fibers. Sarcoplasm contains high amounts of glycogen and myoglobin. An increase in Ca+ concentration in the sarcoplasm begins the process of filament sliding.

Question 10

Describe sarcolemma and state its role in muscle contraction.

Answer 10

Plasma membrane of muscle fiber. High concentration of Na+ and K+ ion channels. The sarcolemma transmits neural excitatory impulses that lead to muscle contraction.

Question 11

Describe junctional folds and state their role in muscle contraction.

Answer 11

Indents of the sarcolemma at the NMJ that increase the surface area and fit the synaptic knob. They create a large surface area for the neurotransmitter to bind to receptors.

Question 12

Describe T-tubules and state their role in muscle contraction.

Answer 12

Place where sarcolemma
folds in across almost the entire cell. T-tubules carry the action potential (AP) deep into the cell interior.

Question 13

Describe the terminal cisternae and state its role in muscle contraction.

Answer 13

Dilated end sac of sarcoplasmic reticulum (always found on either side of T-tubules) . Stores calcium and releases it when an action potential courses down the transverse tubules, eliciting muscle contraction.

Question 14

Describe sarcoplasmic reticulum and state its role in muscle contraction.

Answer 14

A complex network of specialized smooth endoplasmic reticulum. Stores calcium until needed for contraction.

Question 15

What makes up a triad within a muscle cell?

Answer 15

2 terminal cisternae + a T-tubule.

Question 16

Relate the arrangement of a triad to its function.

Answer 16

The main function of the triads are to translate the action potential from the plasma membrane to the sarcoplasmic reticulum, effecting calcium flow into the cytoplasm.

Question 17

What are myofibrils?

Answer 17

Bundles of contractile proteins (thick and thin fibers). Sarcoplasmic reticulum is wrapped around the myofibrils.

Question 18

What is the basic structure/ components of thick filaments.

Answer 18

Contain 200-500 myosin proteins. Each myosin has two entwined tails and two heads.

Question 19

What is the basic structure/ components of thin filaments.

Answer 19

Two intertwined strands of actin protein. Each actin has an active site where the myosin head of the thick filament can bind.

Question 20

What is the functional unit of a muscle fiber?

Answer 20

A sarcomere.

Question 21

Identify the components of the sarcomere.

Answer 21

I Band, A Band, H Band, M Line, and Z Disc.

Question 22

Describe what the I Band is in a sarcomere.

Answer 22

Light area of sarcomere. Contains only thin filaments.

Question 23

Describe what the A Band is in a sarcomere.

Answer 23

Dark area of sarcomere. Refers to the entire length of the thick filaments.

Question 24

Describe what the H Band is in a sarcomere.

Answer 24

Middle of A Band. Where thin filaments don’t reach, contains only thick filaments.

Question 25

Describe what the M Line is in a sarcomere.

Answer 25

Middle of H Band. A transverse protein that links thick filaments together.

Question 26

Describe what the Z Disc is in a sarcomere.

Answer 26

Bisects the I Band (think filaments). Provides anchorage for thin and elastic filaments.

Question 27

Describe the synaptic knob at the NMJ.

Answer 27

Enlarged ends of the axon terminals. Contain synaptic vesicles that store neurotransmitters. When an electrical signal (an action potential) reaches the synaptic knob, it triggers the release of these neurotransmitters.

Question 28

Describe synaptic vesicles.

Answer 28

Are clustered at presynaptic terminals. They store neurotransmitters (ACh) and release them into the synaptic cleft by calcium-triggered exocytosis.

Question 29

Describe the voltage gated Ca+ channels of the synaptic knob.

Answer 29

Channels are found in the membrane of the synaptic knob. When the action potential arrives at the synaptic knob of the motor neuron, it will cause voltage-gated calcium channels to open allowing calcium ions to enter the inside of the synaptic knob and bind to synaptic vesicles, which in turn release ACh.

Question 30

Describe the synaptic cleft of the NMJ.

Answer 30

Fluid filled space between neuron cell membrane and muscle cell membrane.

Question 31

Define resting membrane potential.

Answer 31

Occurs when muscle fibers are relaxed. RMP is -90 mv.

Question 32

Define depolarization.

Answer 32

Region along the membrane at the motor end plate becomes more positive (end plate potential). Mediated by ligand gated channels.

Question 33

Define repolarization.

Answer 33

Membrane starts going back towards the negative resting potential.

Question 34

Define action potential.

Answer 34

Progression of the membrane depolarization along the rest of the sarcolemma. Mediated by voltage gated channels.

Question 35

Is the electric potential of cells negative or positive.

Answer 35

Negative.

Question 36

What is electric potential.

Answer 36

Voltage.

Question 37

Where are ligand gated Na+ channels found and what is their function.

Answer 37

Found along the junctional folds at the NMJ. Channel have ACh receptors attached, when ACh binds to these receptors, the ligand gated Na+ channels open.

Question 38

Where are voltage gated Na+ channels found and what is their function.

Answer 38

Found along the sarcolemma. As one set opens, new Na+ diffuses in, depolarizing the adjacent membrane, opening the next set (action potential).

Question 39

Understand concentration gradient of Na+ and K+.

Answer 39

Na+ concentration is higher extracellularly; it can diffuse into the cell. K+ concentration is higher intracellularly; it can diffuse out Both diffuse with their gradient, high to low.

Question 40

Describe the role of troponin and tropomyosin in inhibiting muscle contraction.

Answer 40

These are the regulatory proteins. Tropomyosin: Blocks actin/myosin binding site when muscle is relaxed. Troponin: Keeps tropomyosin “locked” into place until calcium makes contact with troponin receptors again.

Question 41

What is the sliding filament theory?

Answer 41

It is the process of muscle contraction involving the sliding of actin & myosin myofilaments past each other to shorten the length of each sarcomere.

Question 42

Relate the release of calcium from the terminal cisternae to the action potential along the sarcolemma.

Answer 42

The terminal cisternae stores calcium and releases it into the SR when an action potential courses down the transverse tubules. The SR releases the calcium into the myofibrils through voltage gated Ca+ channels.