So in this article , we will be talking about "MUSCLES". This article is actually a Educational article to learn why doing exercise and lifting weights in Gym build up your body.
So before starting , let's have a visit to image of muscle in your pre-conscious mind
Ok! Let's start with really basic question, but i want you to be true .
Show at the image below and identify it !
Be true to yourself ! You identified it . ALL-RIGHT
You identified it as Smooth muscle! But sorry to say you are wrong 😔
It is a muscle fibre not a muscle , if you identified it as a muscle then image in your pre-conscious mind about muscle is not right and need to be corrected. Well no problem I am here
Muscle VS Muscle Fibre.
Ok let me show you a very old diagram that you must be familiar with :-
You remember this diagram , it is Class 11th NCERT Diagram .
what this diagram actually shows ?
See as you know that nerve and neuron are quite different just like that muscle fibre and muscle are quite different . Let's revisit the diagram again.
so basically when you cut a muscle and put it under a microscope for histological studies what you will notice is quite interesting.
See the outer lining of muscle is called as Epimysium , so basically when you hold a biceps muscle in your hands in anatomy dissection hall your fingers are actually touching the Epimysium
This Epimysium has many muscle bundle within it and we call them as Fasiculi (singular - Fasiculus) (see the fasiculi in the above diagram)
The Fasiculi are actually surrounded by Connec. tissue we call that sheath and content of connective tissue surrounding thses fasiculi as- "Perimysium"
Now what forms the Fasiculus or Muscle bundle ?? It is the Collection of Muscle fibre so imagine it like this.
Assume the pencil are muscle fibres and you collect those pencils together in your hand and that forms a bundle of pencils so just like this muscle fibres come together closely both physically and functionally (via gap junction) to form a Muscle bundle or Fasiculus.
See the image below :-
you might have noticed the spaces between the pencils collection , similar to that there are spaces between different muscle fibres and that space is actually occupied by another connective tissue called - Endomysium (high resistance C.T.)
Long story short :-
Muscle is not a simple structure , it is a complex one .
Surrounded by Epimysium and formed of many Fasiculi and those Fasiculi are surrounded by Perimysium and those Fasiculi are actually formed of Muscle Fibres which are surrounded by Endomysium.
I think now you might be clear about the Muscle structure
see the images below for a final touch to the concept.
So basically a simple definition of muscle is
Muscle refers to multiple bundles (fascicles) of cells joined together called muscle fibers.
Note- Nerves and blood vessel supplying to the muscle fibres exist in the endomysium layer .
OK, so now let's understand what is a motor unit?
Motor unit :-
In very simple terms -
Motor Unit = motor neuron + all the muscle fibres which are supplied by it
Let me make the concepts more clear now.
Consider a nerve supplying a Muscle. So a nerve is complex collection of nerve fibres that means it has a lot of motor neurons which exits from nerve and those motor neurons actually supply a lot of muscle fibres
See the diagram below :-
So pick any motor neuron and whatever muscle fibres are supplied by the branches of that motor neuron combindely with the motor neuron actually supplying forms a Motor unit
So a Muscle is actually made up of a lot of motor units , see the below image to get a more clear view:-
So a muscle contains a lot of motor unit as you can see in above a muscle is nothing but a collection of many motor units
Let,s understand now what happen when you life weight with the help of your muscles.
Motor unit in real life.
So imagine , If i ask you to pick up a pencil . you will easily pick it up and a very little effort will be made by your muscles but if i ask you to pick up a 10 kg bucket of water , you will still pick it up but now the task will not be easy and you apply more strength to pick it up
So Basically as the weight will increase ,the strength to pick it up also increases
Question is where does that Extra strength come from ?
Let me represent the question through a different view - pay attention and focus on question!
When you lifted the pencil your muscles contracted right , when you picked up 10 kg bucket of water your muscle again contracted but what is the difference between those contraction , you may answer that the contraction for lifting 10 kg weight was quite powerful as compared to the one which took place while lifting up the pencil
But what is the Physiological basis of that more powerful contraction or what you say you applied more force against gravity to pick up that bucket.
The Answer lies in the concept of Motor unit , see the below diagram again
as you can see muscle has a lot of motor units , so basically whenever you contract the muscle to do some work not all of the motor unit get activated . NOTE AGAIN-"not all of the motor units get activated when muscle undergo contaction"
It depends on the intensity of work if you are doing a high intensity work (like lifting heavy weights) than many many motor units gets recruited and they get recruited until you are able to lift that weight
So when you are lifting a pencil a very few motor unit get recruited to lift the weight and they are enough able to lift the pencil but when you try to pick up a 10 kg bucket then body start recruiting (many motor neuron start firing on mucle fibres) and they get recruited until you generate an enough force to pick it up .
see the image below :-
Note:- Motor units contains a single motor neuron supplying to many muscle fibres and motor unit recruitment means that motor neuron start firing so all the muscle fibre supplied by that motor neuron contract generating a contraction in muscle , as more motor units get recruited more muscle fibres start contracting thus generating a high amount of Force.
So i hope now , that you must be clear with the concept of Motor unit.
NOTE- if you try your best and still not able to pick up a weight even when all motor unit of that muscle get recruited than this is the point when body starts a interesting process called -Hypertrophy (muscle growth) and this generally happens in those who try to exceed the natural limit of their muscle strength , Like a person at gym trying to lift heavy weight might find very difficult to lift heavy weight initially but as day passes he is able to lift that weight , it is because his body muscle has now adapted themself to that weight by doing hypertrophy (we will discuss about this later in detail )
Now you have Learnt about motor unit and their recruitment , let me tell you an interesting case :-
In some system of body all the Motor unit contract together as a single unit but it happens in just few organ system of body and example of such organ is -GIT and those muscle are mostly smooth muscle , so this generated a new group of muscle called - Unitary smooth muscle . Let's understand this concept.
Unitary smooth muscle:-
Unitary smooth muscles are those muscle in which all motor units contract as a single unit , in those muscles no thing like - "recruitment of motor unit " exists just one firing from a neuron to any motor unit will excite all of the motor units(it happens because many gap junction exists between several motor units and due to them there exists a excitation synchronization ) it is found in "GIT" the Muscularis externa layer that you studied during the histology of "GIT" which is present on outer side of submucosa is actually made up of unitary smooth muscles.
Note - Multi-unit smooth muscle does exists (like in some part of respiratory system)
Muscle Growth and collaboration in real life
Ok, so we will now learn how strength training in the gym and regular exercise affects your body .
Let's start with a basic question:-
Which system in our body is trained by lifting weights and doing exercise
Well that the answer might shock you but let me reveal the answer:-
The organ system that get tuned up due to regular exercise and strength training(lifting heavy weight in gym) are:-
- Cardiovascular system
- Muscular system
- Central Nervous system
- Skeletal system
Note:-Well , there are some other homeostatic process which also get better with exercise land affects Lipid profile , Sugar profile but we will not talk about them.
Note:- Running tunes up the respiratory system also.
So major 4 system in your body get tuned up , we will learn about only two in this article . We will be talking about How muscular system and CNS get better due to regular exercise.
CNS and Exercise--
Well let's start with a very basic query of most of people :- "How i can boost my brain power?"
People are always wondering how we can increase our brain cognitive functionality ? and the answer they always get is -"Wake up early and do some exercise on regular basis "
Most of people can't understand how exercise affect brain ??? and they just neglect this advice and focus more on heavy tasks for improving their brain function like memory games and mathematical calculation games.
Well let me clearly tell you that Exercise on a regular basis significantly improve cognitive ability even more than mind training games . Wanna know why,how???
Let's start :-
You learned about motor unit above and I hope your concept is clear now about motor unit.
Ok Imagine now -- You are in Gym, lifting dumbbell or running in a field as a part of your daily exercise routine. What happens after some time ? You get tired
But why you get tired ??
You are in Gym , you are lifting weight of 10 KG applying all of your force and finally after some time you will get tired to an extent that you will not be able to lift even a 1 KG weight and you feel what people call as-"Muscle Soreness".
Think deeply :- Are those muscles, which are actually tired or something else?
Let me tell you(Non-strictly speaking) that your muscle does not get tired actually it is the accumulation of Lactic acid which cause the pain during the muscular soreness. It is actually the CNS which is tired or You can say neuronal fatigue .
Have you ever heared -"In living human body fatigue only take place at Synapses"
Well it is definitely true . So in short i want to say that when you are constantly using a muscle and picking up heavy weights and you have already recruited all of the motor units of that muscle , the neurons firing to muscles fibres of several motor unit start getting tired and they stop their firing and motor units start getting de-recruited and with time and continuously lifting weight more and more motor unit get de-recruited as neurons firing to them get tired.
Note:-Neuronal adaptation is phenomenon which is also called neuronal fatigue in sensory system.
So in short It's the CNS which get tired and as neuron stops firing , so the Motor unit also stop working and as less and less motor unit are available and working in muslce ,Muscle strength decreases and you find hard to lift same weight after lifting it 8,9 times (that is what forms a set of 8 or 9 reps for body builders and you need some rest)
You take some rest and then again , you get your strength back and start lifting weight again , again after some time CNS undergo fatigue you again take rest and cycle goes on .....
That is how Exercise is actually connected with the CNS .
Now you know how exercise and brain are related (brain is the one which sends signals for muscular contraction) but still we did not get our answer -"How exercise tune up the CNS"
Let me clarify this thing very simply :-
What happens if you visit on a road very often ? You will be more aware to that road Right! , well same thing happens in the CNS , Muscle you use more extensively by activating his all motor units, the neuronal pathway supplying that muscle motor units get more stronger and more recognized to the CNS. Also the primary motor cortex(Brodmann area no.-4) adapts to your training also and also the prefrontal cotex (Origin of thoughts take place here) adapts to your training and develops.
So training and exercise improves your cortex function that's why It is often advised to do exercise if you really want to improve your brain function.
Interesting comparison of person who regularly do exercise and of the one who does not . Let's compare just on the basis of CNS. Who will be perform better ?
Note:- Person doing exercise has muscles which have undergone hypertrophy to a large extent . I am asking you to think of Imaginative case of a person who have not undergone muscular hypertrophy but have undergone CNS tune up due to regular exercise.
Obviously the person having CNS tune up will win easily because as the neuronal pathways in his CNS are strong and he will be able to recruit a large amount of motor unit in a short amount of time and normal person who does not do exercise will not be able to recruit all of motor unit very easily .
Note:- Recruiting all of motor unit is not a very easy task , it really overburden the CNS that's why in initial day of gym you do not develope muscle by lifting weights . For few days you are actually learning to recruit all of your motor unit and when you reach at a stage when you are able to recruit all of your motor units of your muscles , you start strengthening up your neuronal pathways to that muscle and tuning up your CNS.
Note:- There are a lot of process that are responsible for muscle soreness and strictly speaking Muscle tiredness is a really a legit thing (we will learn about it later) . I have tried to simplify the things , as much as I can for this article . In real life the Process is very complex ,you do not need to overburden your CNS with that complex process
In upcoming update , we will talk about Muscle hypertrophy and other aspects of muscle growth
Stay updated .
--signing off
Bhavesh saini
Comments
Post a Comment