Exam 2

Question 1

How do myofibers form?

Answer 1

Myoblasts fuse to become myotubes which differentiate into myofibers with satellite cells attached.

Question 2

What are the regulatory proteins found on thin filaments?

Answer 2

Troponin and tropomyosin.

Question 3

What are thin filaments composed of? Thick?

Answer 3

Actin. Myosin.

Question 4

What do myosin heads (cross-bridges) contain?

Answer 4

Actin, ATP, and ATPase binding sites.

Question 5

What protein do z-discs contain? What is its function?

Answer 5

Actinin. Binds actin on thin filaments.

Question 6

What determines the length of a sarcomere?

Answer 6

Length between neighboring z-discs.

Question 7

What is the H-zone? Why is it lighter in pigment than the A band?

Answer 7

Portion of the A band that lacks myosin heads and contains no filament overlap - thick filaments only. These are the two reasons it is lighter in color.

Question 8

What is the A band? I band?

Answer 8

The A band is a dark zone full of thick filaments. At the edges, the A band has filament overlap. The I band is a light zone full of thin filaments only. The I bands flank each z-disc.

Question 9

What is the M-line? What moves closer to it during contraction?

Answer 9

Line in the middle of the H-zone with proteins that cross-link the thick filaments. Thin filaments move towards the M-line during contraction.

Question 10

What is the M-line? What moves closer to it during contraction?

Answer 10

Line in the middle of the H-zone with proteins that cross-link the thick filaments. Thin filaments move towards the M-line during contraction.

Question 11

What changes occur in the sarcomere during contraction?

Answer 11

I-bands shorten, H-zone virtually disappears, and z-discs get closer together, shortening the sarcomere.

Question 12

Why is there no attachment between thick and thin filaments during relaxation?

Answer 12

Regulatory proteins troponin and tropomyosin block actin binding sites.

Question 13

What causes a conformational change in troponin? What does this conformation do?

Answer 13

Binding of calcium ions. The conformational change exposes the actin binding sites so the thin filament can bind to myosin heads.

Question 14

What does binding of actin to the myosin head increase? Why?

Answer 14

Binding increases activity of ATP synthase. This is because actin is a cofactor.

Question 15

What does the power stroke motion receive its energy from? What happens in this process?

Answer 15

Hydrolysis of ATP. Thick filaments anchor and pull the thin filaments towards the M-line. ATP releases the thin filament so the process can be repeated rapidly.

Question 16

What is the NMJ?

Answer 16

Synapse that occurs between a motor neuron and muscle fiber.

Question 17

Which neurotransmitter do synaptic vesicles in the NMJ release? How does this bind and what are its immediate affects?

Answer 17

Acetylcholine (AcH). Binds to AcH receptors on myofibers and causes a wave of depolarization.

Question 18

What composes a triad? What are the functions of each component?

Answer 18

Composed of a t-tubule with 2 terminal cisternae (flanking SR). The t-tubule invaginates into the sarcolemma to allow for depolarization of inner myofibrils while the SR releases calcium ions that can bind to actin sites on thin filaments for contraction.

Question 19

What are the key features of slow twitch muscles? Fast twitch?

Answer 19

Slow twitch have lots of myoglobin (more red) and fatigue slowly while fast twitch are very large and fatigue rapidly.

Question 20

What are the 4 unique features of cardiac muscles in comparison to skeletal?

Answer 20

1. Intercalated discs: allow for synchronous contraction via gap junctions/desmosomes.
2. Branched.
3. Uninucleated or binucleated.
4. Diads: cardiac muscles don’t need as much calcium from the SR so they only need 1 terminal cisternae. In addition, the diads are found over z-discs compared to skeletal where they are found in the I-A region.

Question 21

What are the components of the blood and what percentage do they make up?

Answer 21

Plasma (55%), erythrocytes (45%), and buffy coat (leukocyte and platelets - <1%)

Question 22

What are the components of plasma?

Answer 22

Water (92%), proteins (albumins, globulens, and fibrinogen - 7%), and small molecules (<1%).

Question 23

What is serum? What are the serum proteins and what are their functions?

Answer 23

Plasma without clotting factors. Albumins and globulins maintain osmotic blood pressure and function as transport molecules.

Question 24

What is hematocrit?

Answer 24

Volume of packed red blood cells in a sample.

Question 25

What is the function of fibrinogen?

Answer 25

Precursor molecule to fibrin which is crucial to clotting. Clotting factors convert prothrombin into thrombin which converts fibrinogen into fibrin.

Question 26

What is the function of blood?

Answer 26

Gas carry, transportation, and clotting.

Question 27

What are blood smears?

Answer 27

Staining process that allows you to see different cells in a blood sample.

Question 28

Describe the erythrocyte structure. Include shape and size.

Answer 28

Biconcave shape that’s basically a sac of hemoglobin with no organelles or nucleus. 7-8 microns.
Hemoglobin is made up of 2 alpha globulin chains, 2 beta globulin chains, and a central heme group with iron.

Question 29

What is the function of red blood cells? How long do they live?

Answer 29

Gas transport via Hb which binds reversibly to O2 and CO2. Live for 120 days and are removed by spleen/liver by phagocytosis.

Question 30

What are sickle cell erythrocytes and what do they cause? Why have they not gone away from evolution?

Answer 30

Single amino acid mutation in beta chain that deforms the cell and makes it more fragile. These cells often burst (hemolysis) and/or lead to anemia (reduced O2 carrying capacity). Heterozygotes have a reduced risk of contracting malaria.

Question 31

What do all leukocytes contain? What do they stain with? What do presence of secondary granules indicate?

Answer 31

Azurophylic (primary granules) that stain light pink with azure. Indicates granulocytes if secondary granules present.

Question 32

What do all leukocytes contain? What do they stain with? What do presence of secondary granules indicate?

Answer 32

Azurophylic (primary granules) that stain blue with azure. Indicates granulocytes if secondary granules present.

Question 33

What are the different types of leukocytes and what percentage do they make up?

Answer 33

Neutrophils (50-60%), eosinophils (1-5%), basophils (<1%), lymphocytes (20-30%), monocytes (5-10%).

Question 34

Describe the structure of neutrophils and how they stain. What are Barr bodies?

Answer 34

Highly lobed nuclei. Secondary granules that stain light pink. Small appendages coming off nucleus which indicate a female.

Question 35

What is the function of neutrophils? Where are they often found?

Answer 35

Contains lysozymes, lactoferrin, and myeloperoxidase that all generate reactive O2 species which fight off pathogens and bacteria. Found in wound pus.

Question 36

Describe the structure of eosinophils.

Answer 36

Bi-lobed nuclei with secondary granules that stain hot pink and have an inner core and outer region.

Question 37

What is the function of eosinophils?

Answer 37

Core of secondary granules contain a protein which is toxic while RNAses and EPs on the outside act as antivirals and reactive O2 species. These cells attack large helmin (worm) parasites and can contribute to inflammation. They can worsen asthma and eosonophilic esophagitis (closing of the esophagus).

Question 38

Describe the structure of basophils.

Answer 38

Have abundant metachromatic secondary granules which stain dark blue and/or purple.

Question 39

What is the function of basophils?

Answer 39

Granules contain heparin (prevents clotting) and histamine (allergic response). Both basophils and mast cells function in allergic reactions due to their metachromatic granules.

Question 40

Describe the structure of lymphocytes including diameter.

Answer 40

Smallest leukocyte (8-9 microns) that have a very large nuclei that takes up most of the cell.

Question 41

Describe the structure, size, and function of monocytes.

Answer 41

Largest leukocyte (20-25 microns) with an indented nucleus. They are the precursor to the phagocytic system as they give rise to macrophages.

Question 42

Describe the structure of platelets.

Answer 42

No nucleus with many synthetic organelles. Platelets are fragments of megakaryotes and they are metabolically active. They are composed of alpha and delta granules.

Question 43

What is the function of platelets?

Answer 43

Crucial in the clotting process.