Histology

Question 1

A Band

Answer 1

Anisotropic, only colored in polarized light, thick and thin. Bisected by M line.

Question 2

I band

Answer 2

Isotropic, bisected by Z disc, only actin

Question 3

Z disc

Answer 3

Bisects I bands. Area between 2 z discs = sarcomere.

Question 4

H band

Answer 4

Only thick. Area around M line.

Question 5

Types of striated muscle

Answer 5

Skeletal (move skeleton), visceral striated (tongue, pharynx, diaphragm, upper esophagus), cardiac (in the walls and base of large veins of the heart)

Question 6

Structure of troponin

Answer 6

3 subunits: TnC (calcium), TnI (actin), TnT (tropomyosin)

Question 7

Tropomyosin

Answer 7

masks myosin binding site on actin

Question 8

Triad

Answer 8

At A-I junction. 2 terminal cisterna of sarcoplasmic reticulum and 1 T-tubule. depolarization of the t tubule membrane triggers release of calcium from the terminal cisternae to initiate uscle contraction.

Question 9

dystrophin

Answer 9

binds ECM to actin filaments through dystroglycans

Question 10

Titin

Answer 10

spring, centers thick filament (@ z disc)

Question 11

Myosin II structure

Answer 11

dimer, 2 heads (globular). 1 ATP ginding site, 1 actin binding site. 2 necks: regulatory light chain x 2, essential light chain x 2. Tail: coiled coil –> bipolar arrangement –> bare zone (no heads)

Question 12

alpha actinin

Answer 12

binds actin to z disc

Question 13

desmin

Answer 13

intermediate filament binding sarcomeres to each other around z discs

Question 14

m line proteins

Answer 14

hold thick together

Question 15

What happens in contraction

Answer 15

Calcium binds to troponin –> tropomyoin moves out of the way –> ATP regulates muscle contraction –> shortening of I band.

Question 16

Types of muscle fibers

Answer 16

Type I: slow twitch, A. Type 2A: fast-twitch. Type 2B: fast twitch anaerobic.

Question 17

Type 1 muscle fiber

Answer 17

slow twitch, A (aerobic), small force, sustained activity, dark meat, myosin- ATPase rxn is slowest. Resistant to fatigue

Question 18

Type 2A muscle fiber

Answer 18

fast-twitch, glycolitic “I”, larger, pink (myoglobin), intermediate force, resistant to fatigue

Question 19

Type 2B muscle fiber

Answer 19

fasttwitch glycolitic, anaerobic. Fatigable, large force, lots of glycogen, fastest myosin ATPase activity –> lots of lactic acid

Question 20

terminal cisternae

Answer 20

serve as reservoirs for calcium. Plasma membrane contains an abundance of gated calcium release channels called ryanodine receptors.

Question 21

Ryanodine receptors

Answer 21

gated calcium release channels involved in releasing calcium into the sarcoplasm.

Question 22

calsequestrin

Answer 22

highly acidic calcum-binding protein capable of binding up to 50 internalized calcium ions; allows storage at high concentration.

Question 23

Myasthenia gravis

Answer 23

ACh nicotinic receptors are blocked by antibodies directed to the body’s own receptor proteein. Autoimmune disease caused by the reduced number of functional ACh receptor sites. –> weakening of the muscle fiber response to nerve stimulus. Begins with extraocular muscles. AChE inhibitors = pharmacological treatment. (extend the life of released ACh within the synaptic cleft).

Question 24

curare

Answer 24

paralyzing poison used on arrow tips in South America, binds to nictinic ACh receptors without opening the ion channels. –> paralysis of skeletal muscles including the diaphragm) without affecting contraction of cardiac muscle.

Question 25

Muscle spindle

Answer 25

specialized stretch receptor found in all skeletal muscles, consists of spindle cells and neuron terminals. 2 types of spindle cells: nuclear bag fiber and nuclear chain fiber.

Question 26

Nuclear bag fiber

Answer 26

(in muscle spindle) type of spindle cell containing an aggregation of nuclei in an expanded midregion

Question 27

nuclear chain fiber

Answer 27

(in muscle spindle) type of spindle cell having many nuclei arranged in a chain

Question 28

Types of sensory afferent nerve fibers coming from muscle spindles

Answer 28

Ia- annulospiral endings over both types of spindle cells. 2: flowerspray endings over the striated portions of bag fibers

Question 29

Golgi tendon organs

Answer 29

found in the tendons of muscle and respond to increased tension on the muscle. Contain only sensory (afferent, 1b) nerve fibers, monitor tension.

Question 30

thin filament consists of?

Answer 30

actin, troponin, and tropomyosin