It’s all about muscle fibers

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Presented by Idhal Sajeev

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At the end of the lesson, students are be able to:
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Give a definition
and description
of muscle fibers
Label the parts
of a muscle fiber
Identify the
functions of
each parts.

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Definition of a Muscle Fiber
Types of Muscle fibers
Parts and Functions

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Definition of a
Muscle fiber

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The muscular system works to control the movement
of our body and internal organs. Muscle tissue
contains something called muscle fibers.
Muscle fibers consist of a single muscle cell. They help
to control the physical forces within the body. When
grouped together, they can facilitate organized
movement of your limbs and tissues.

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Types of Muscle
Tissues

7. There are several types of muscle fiber, each with different
characteristics. Keep reading to learn more about these
different types, what they do, and more.
Types
You have three types of muscle tissue in your body. These
include:
skeletal muscle
smooth muscle
cardiac muscle
Each of these types of muscle tissue has muscle fibers. Let’s
take a deeper dive into the muscle fibers in each type of
muscle tissue.
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8. Each one of your skeletal muscles is made up of hundreds to thousandsTrusted
Source of muscle fibers that are tightly wrapped together by connective tissue.
Each muscle fiber contains smaller units made up of repeating thick and thin
filaments. This causes the muscle tissue to be striated, or have a striped
appearance.
Skeletal muscle fibers are classified into two types: type 1 and type 2. Type 2 is
further broken down into subtypes.
Type 1. These fibers utilize oxygen to generate energy for movement. Type 1
fibers have a higher density of energy-generating organelles called
mitochondria. This makes them dark.
Type 2A. Like type 1 fibers, type 2A fibers can also use oxygen to generate
energy for movement. However, they contain less mitochondria, making them
light.
Type 2B. Type 2B fibers don’t use oxygen to generate energy. Instead, they
store energy that can be used for short bursts of movement. They contain
even less mitochondria than type 2A fibers and appear white.
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9. Skeletal muscle

10. Unlike skeletal muscles, smooth muscles aren’t
striated. Their more uniform appearance
gives them their name.
Smooth muscle fibers have an oblong shape,
much like a football. They’re also thousands of
times shorter than skeletal muscle fibers.
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11. Similar to skeletal muscles, cardiac muscles are
striated. They’re only found in the heart. Cardiac
muscle fibers have some unique features.
Cardiac muscle fibers have their own rhythm.
Special cells, called pacemaker cells, generate the
impulses that cause cardiac muscle to contract.
This typically happens at a constant pace, but can
also speed up or slow down as necessary.
Second, cardiac muscle fibers are branched and
interconnected. When the pacemaker cells
generate an impulse, it spreads in an organized,
wavelike pattern, which facilitates the beating of
your heart.
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Functions of Muscle
Fibers

13. The types of muscle tissue have different functions within
your body:
Skeletal muscle. These muscles are attached to your
skeleton by tendons and control the voluntary
movements of your body. Examples include walking,
bending over, and picking up an object.
Smooth muscle. Smooth muscles are involuntary,
meaning that you can’t control them. They’re found in
your internal organs and eyes. Examples of some of their
functions include moving food through your digestive
tract and changing the sizes of your pupil.
Cardiac muscle. Cardiac muscle is found in your heart.
Like smooth muscle, it’s also involuntary. Cardiac muscle
contracts in a coordinated way to allow your heart to
beat.
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14. Muscle fibers and muscles work to cause movement in the
body. But how does this occur? While the exact mechanism
is different between striated and smooth muscles, the
basic process is similar.
The first thing that occurs is something called
depolarization. Depolarization is a change in electric
charge. It can be initiated by a stimulatory input like a nerve
impulse or, in the case of the heart, by pacemaker cells.
Depolarization leads to a complex chain reaction within
muscle fibers. This eventually leads to a release of energy,
resulting in muscle contraction. Muscles relax when they
stop receiving a stimulatory input.
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15. You may have also heard about something called fast-twitch
(FT) and slow-twitch (ST) muscle. FT and ST refer to skeletal
muscle fibers. Types 2A and 2B are considered to be FT while
type 1 fibers are ST.
FT and ST refer to how fast muscles contract. The speed at
which a muscle contracts is determined by how quickly it
acts on ATP. ATP is a molecule that releases energy when it’s
broken down. FT fibers break down ATP twice as fast as ST
fibers.
Additionally, fibers that use oxygen to produce energy (ATP)
fatigue at a slower rate than those that don’t. So as far as
endurance is concerned, the skeletal muscles listed from
highest to lowest are:
type 1
type 2A
type 2B
1.
2.
3.
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16. It’s possible for muscle fibers to develop problems. Some examples of this include but aren’t limited to:
Cramps. Muscle cramps occur when a single skeletal muscle fiber, muscle, or entire muscle group
contracts involuntarily. They’re often painful and can last for several seconds or minutes.
Muscle injury. This is when skeletal muscle fibers are stretched or torn. This can happen when a
muscle stretches beyond its limits or is made to contract too strongly. Some of the most common
causes are sports and accidents.
Palsy. These actually happen due to conditions affecting the nerves. These conditions can go on to
affect skeletal muscles, leading to weakness or paralysis. Examples include Bell’s palsy and Guyon
canal syndrome.
Asthma. In asthma, the smooth muscle tissue in your airways contracts in response to various
triggers. This can lead to narrowing of the airways and breathing difficulties.
Coronary artery disease (CAD). This happens when your heart muscle doesn’t get enough oxygen and
can cause symptoms like angina. CAD can lead to damage to cardiac muscle, which can impact the
functioning of your heart.
Muscular dystrophies. This is a group of diseases characterized by degeneration of muscle fibers,
leading to a progressive loss of muscle mass and weakness.
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17. T h S C k y o H !