1.9

Question 1

characterisctics of Striated muscle

Answer 1

• each muscle fiber behaves as a single unit
• multinucleated
• myofibrils are surrounded by Sarcoplasmic Reticulum and invaginated by T (Transverse) Tubules

Question 2

myofibrils are divided to

Answer 2

repeating units of- Sarcomeres, which are the basic contractile unit

Question 3

Sarcomeres are composed of

Answer 3

Thick and Thin filaments

Question 4

Thick filaments contain

Answer 4

Myosin

Question 5

structure of Myosin

Answer 5

1x heavy chain

2x light chains

Question 6

Thin filaments contains 3 proteins:

Answer 6

• Actin
• Tropomyosin
• Troponin

Question 7

Describe what is Tropomyosin:

Answer 7

Runs along the Actin filament
It blocks the Myosin-binding site on Actin
we have to remove Tropomyosin in order for contraction to occcur

Question 8

Describe what is Troponin:

Answer 8

composed of 3 proteins:

1. Troponin T (attaches the Troponin to tropomyosin)
2. Troponin I (inhibits the intercation of actin-myosin)
3. Troponin C (binds Ca++)

Question 9

what is the name for continued cross-bridge cycling?

Answer 9

Tetanus

Question 10

The force of contraction depends on

Answer 10

Length of the sarcomer

Question 11

why do Passive tension arises when the muscle is stretched to long?

Answer 11

bcs of the elasticity of the muscle

Question 12

what creates the active tension?

Answer 12

the voluntary movement of the muscle

Question 13

Isometric?

Answer 13

muscle length is not changing
tension increases
antigravity muscles

Question 14

Isotonic?

Answer 14

tension remains the same

muscle shortens

Question 15

what doe we call it when both length and load varies during contraction?

Answer 15

Auxotonic

Question 16

Describe slow twitch muscle fiber

Answer 16

type I
red
oxidative
high mito
low glycogen

Question 17

Describe type IIa muscle fiber

Answer 17

red
oxidative
highest amount of mitochondria
very little glycogen
fast twitch

Question 18

Describe type IIb muscle fiber

Answer 18

fatigable
white
glycolitic
many glycogen
less mito
fast twitch

Question 19

Types of motor units

Answer 19

S: slow twitch
FF: like chicken breast. Fast twitch, Fatigable
FR: Fast and Resistable, like chicken leg

Question 20

what is the Ca sensor on the smooth muscle cell?

Answer 20

Calmodulin

Question 21

twitch duration in smooth muscle cell

Answer 21

200 ms-sustained

Question 22

Define the NMJ

Answer 22

chemical synaps in which ACh is release by a-motor neuron into the synaptic cleft

***only ACh!!

Question 23

Define the End Plate Potential

Answer 23

when the membrane of the skeletal muscle depolarize from -90 mV to -50 mV
* -50 mV is the EPP

Question 24

How many vesicles are necessary to reach the threshold?

from -90 to -50 mV

Answer 24

about 100
each MEPP (Miniature End Plate Potential= ACh in one vesicle) depolarize the membrane about 0.4 mV

Question 25

what can alter NMJ function?

Answer 25

Botulinium
Curare
Neostigmine
Hemicholinium

Question 26

How does Botulinium alter NMJ function?

Answer 26

blocks ACh release from the axon

Question 27

How does Curare alter NMJ function?

Answer 27

blocks NAChR

Question 28

How does Neostigmine alter NMJ function?

Answer 28

inhibits ACh Esterase

prolongs ACh effect on the NMJ

Question 29

what does Atropin do?

Answer 29

blocks muscarinic ACh R

Question 30

How does Hemicholinium alter NMJ function?

Answer 30

blocks choline reuptake by the Na/choline symporter