L7 Muscles

Question 1

Explain the Actin and myosin protein structure

Answer 1

Each thick myosin filament is surrounded by thin actin filaments, at this every actin filament is surrounded by three myosin filaments

Question 2

How much dose the sarcomere contain of myosin

Answer 2

Each sarcomere has several thousand myosin filaments and 2000 thousand actin filaments located around myosin

Question 3

What is the structure of the sarcomere

Answer 3

1- myosin 
2- actin 
3- bridge of myosin 
4 - heads of the bridges 
5 - tropomyosin

Question 4

What is the sarcomere?

Answer 4

Sarcomere is common property of the all muscles , its organelles that provide muscle contraction

Question 5

Explain the sarcomere mechanism ( mechanism of the muscles contraction )

Answer 5

— First AP from outer membrane of a myocyte passes to a membrane of sarcoplasmic reticulum , that is calcium depot , calcium comes out from the depot through channels passively and gets into the sarcoplasm

— after the calcium appeared in sarcomere myosin heads connect to actin , the head are represented by a molecule of ATP , then ATP breaks down releasing energy that is used ti turn the head , the head rotate for 45 degrees and entails actin , this resulting in shorting of a sarcomere by 1% , and i total a sarcomere can shorten by 50% once the head turned , it detaches from actin ,Resynthesis of ATP from ADP take place and the head joins actin again

— next the relaxation begins , relaxation happens bcs calcium returns to depot due to pumps of sarcoplasmic reticulum begins to work

— in the absence of calcium
1) tropomyosin block restore
2) ATPase activity of myosin disappears
Therefore there will be no energy to turn the head
Contraction stop and tendons stretch the muscle leading it to a relaxed state

Question 6

Why Relaxation is an active process ?

Answer 6

Bcs energy is spent for functioning of calcium pumps

Question 7

What is the function of calcium in the sarcomere mechanism ( contraction of the muscles mechanism)

Answer 7

• It has 2 function
  —1) removes the tropomyosin block : in the presence of clacium protein of tropomyosin change its confirmation so thats it goss into the grooves of actin so actin can connect with myosin
  —2) Activation of ATPase activity of myosin : the Latin prefix (ase) at the end of the word thats mean we are speaking about a protein splitting the substance

Question 8

How many phases of the muscles contraction

Answer 8

1- latent period (0,01 sec )
2- phase of shortening (0,05 sec)
3- relaxation phase (0,05 - 0,06 sec)

Question 9

Explain the Latent period

Answer 9

Latent means hidden in medicine a period is called latent when a stimulus has already acted on , some process has already begun but there are no visible changes yet
Ex: infection activator ( germ ) appears in an organism a disease begun but there are no symptom this disease yet
— in latent period of muscle contraction
1- AP generating happens
2- calcium passage from a depot happens

Question 10

Explain the energetics of muscle contraction ( for what is spent (

Answer 10

1- ATP + ATPase = ADP + Ph- group + E1
( head turning and its breaking off ) 
2 - ADP + Ph-group+E2=ATP 
3- glucose + o2 = lactic acid ( or pyroracemic acid ) + E2 
4- Ca2+ pump ( for relaxation) 
5- K+\Na+ pump ( AT RP and AP )

Question 11

What is the fatigue ?

Answer 11

• Fatigue is a physiological condition that arises due to long term performing a function by tissue

There is another Df
- fatigue is lowering of tissue lability as result of long work

Question 12

What is the theories of fatigue ?

Answer 12

1- Starvation 
2- pollution 
3-Hypoxia 
4-suffocation 
5-Central

Question 13

Explain the starvation theory of fatigue

Answer 13

In experiment with a neuromuscular preparation , if we put a tired (fatigued) muscle in a glucose solution , the muscle immediately restore its contractive activity
- why thats happens : one of the reasons for fatigue us expenditure of nutrients (glucose in sarcoplasm ) the glucose is necessary for ATP resynthesis , and id the ATO dose not restore , then there will be no energy to turn the heads

Question 14

Explain the pollution theory of fatigue

Answer 14

In experiment with a neuromuscular preparation , we wash it with physiological solution , by this we remove metabolic products such as lactic acid , the muscle restore its contractions , therefore while long operation in a sarcomere excess amount of metabolic , lactic acid , protons accumulate , they contaminate the muscle , causing medium acidification , and i the acidic medium sarcomere proteins lose their activity

Question 15

Explain the Hypoxia theory of fatigue

Answer 15

If we put fatigued muscle in a hyperoxic solution contractions restore
- bcs while long operation oxygen is spent in tissues And its necessary for glycolysis reactions ( oxidation of glucose )

Question 16

What is the hyperoxic solution

Answer 16

Its a solution with high content of oxygen

Question 17

Explain the Suffocation theory of fatigue

Answer 17

If we place a muscle in hypercapinc solution in this solution fatigue develops significantly faster ,

Question 18

What is the hypercapnic solution

Answer 18

Its a solution with high content of carbon dioxide

Carbon dioxide is metabolic as well as lactic acid and protons

Question 19

What the reason of fatigue ?

Answer 19

Excess of lactic acid or protons carbon dioxide as well

Question 20

Explain the Central theory of fatigue

Answer 20

We have a fatigue neuromuscular preparation and we placed irritation not to muscle but to the nerve , once fatige arise we moved the stimuli to the muscle
And its start to contract again why ?
- bcs in the holistic organism fatigue develops earliest in synapses as result of spending the mediator , if there is no mediator , impulses from a nerve cannot pass to a muscle, the muscle stop to contract , and most of the synapses located in the CNS so fatigue develops primarily in the CNS