Origin of Bioelectric Signals | Basic Concepts

Summary

This educational video delves into the origins of bioelectric signals in the human body, which are linked to the cell, the smallest functional unit. It explains how the distribution of ions like sodium, potassium, and chloride across cell membranes creates electric potentials, leading to resting and action potentials. The video outlines the polarization and depolarization processes, and how these bioelectric signals are crucial for heart, brain, and muscle function, with techniques like ECG, EEG, and EMG used for analysis and monitoring.

Takeaways

• 🧠 The video discusses the origin of bioelectric signals in the human body, focusing on their generation at the cellular level.
• 🧬 Bioelectric signals originate due to the unequal distribution of ions across the cell membrane, leading to the development of an electric potential.
• 💧 The human body is composed of about 70% fluid, which contains several principal ions like sodium (Na+), potassium (K+), and chloride (Cl-).
• ⚡ The unequal distribution of these ions creates an electric potential across the cell membrane, known as bioelectric potential.
• 🧱 In the resting state, cells have a negative charge on the inner surface of the membrane and a positive charge on the outer surface, leading to a resting potential of about -90 millivolts.
• 🏃 When a cell is excited, the charge distribution reverses: the inner surface becomes positive, and the outer surface becomes negative, creating an action potential of about +20 millivolts.
• 🔄 The process of a cell returning to its resting state after being excited is called repolarization, and the time it takes is known as the refractory period (approximately 3-4 milliseconds).
• 💓 The video explains the main bioelectric signals: ECG (Electrocardiography) for the heart, EEG (Electroencephalography) for the brain, and EMG (Electromyography) for skeletal muscles.
• 📊 The frequency and amplitude ranges for these bioelectric signals are outlined, with ECG ranging from 0.05 to 120 Hz and EEG from 0.1 to 100 Hz, among others.
• 🎓 The video concludes by summarizing the importance of understanding bioelectric signals for biomedical analysis and patient monitoring.

Q & A

What is the main topic discussed in the video?

The video discusses the basic concepts related to the origination of bioelectric signals in the human body.

What is the smallest functional and structural unit of the human body mentioned in the video?

The cell is described as the smallest functional and structural unit of the human body.

What role do ions play in the development of bioelectric signals?

Ions such as sodium, potassium, and chloride are crucial for the development of bioelectric signals. The unequal distribution of these ions across the cell membrane leads to the formation of an electric potential.

What is the difference between resting potential and action potential?

Resting potential occurs when a cell is in a non-excited state, with negative charge on the inner surface and positive charge on the outer surface, typically around -90 millivolts. Action potential occurs during cell excitation, where the charges reverse, with positive charge inside and negative outside, reaching around +20 millivolts.

What is depolarization and how does it relate to the action potential?

Depolarization is the process where the cell transitions from a resting state to an excited state, leading to the generation of an action potential. During this process, the cell membrane's charge distribution reverses.

What happens during repolarization?

Repolarization is the process by which a cell returns from an excited state back to its resting state, re-establishing the original charge distribution with negative charge inside and positive charge outside.

What is the refractory period and how long does it last?

The refractory period is the time it takes for a cell to return to its resting state after excitation. It typically lasts about 3 to 4 milliseconds.

What are the three main bioelectric signals mentioned in the video, and what do they measure?

The three main bioelectric signals are the electrocardiogram (ECG) which measures heart activity, the electroencephalogram (EEG) which measures brain activity, and the electromyogram (EMG) which measures skeletal muscle activity.

What are the typical frequency and amplitude ranges for ECG, EEG, and EMG signals?

ECG signals have a frequency range of 0.05 to 120 Hz and an amplitude range of 0.1 to 5 microvolts. EEG signals have a frequency range of 0.1 to 100 Hz and an amplitude range of 2 to 200 microvolts. EMG signals have a frequency range of 5 Hz to 2 kHz and an amplitude range of 0.1 to 5 microvolts.

Why is it important to understand bioelectric signals in the context of biomedical analysis?

Understanding bioelectric signals is crucial for biomedical analysis because these signals are used in patient monitoring systems to identify medical anomalies related to the heart, brain, and muscular systems.

Outlines

00:00

🔬 Introduction to Bioelectric Signals and Cells

This paragraph introduces the concept of bioelectric signals, explaining that they originate from cells, the basic building blocks of the human body. The human body consists of trillions of cells varying in size, and these cells contribute to bioelectric signals through the distribution of ions within body fluids. The paragraph explains how different ions like sodium, potassium, and chloride create electric potentials across cell membranes due to their unequal distribution, laying the groundwork for understanding bioelectric signals.

05:02

⚡ Resting and Action Potentials Explained

This section delves into the behavior of cells in resting and excited states. It explains that during the resting state, cells have a negative charge on the inner surface of the cell membrane and a positive charge on the outer surface, leading to the development of a resting potential, typically around -90 millivolts. When a cell is in an excited state, due to physical activities like walking or lifting, the charges reverse, creating an action potential of about +20 millivolts. The paragraph emphasizes the concepts of polarization and depolarization as key processes in these states.

10:03

🔄 The Cycle of Polarization, Depolarization, and Repolarization

This paragraph discusses the transition of cells from a resting state to an excited state and back again, a process known as repolarization. It explains that after excitation, cells quickly return to their resting state within a refractory period of 3-4 milliseconds. The paragraph also provides a graph illustrating the changes in electric potential during these states. Additionally, it mentions the main bioelectric signals—ECG (heart), EEG (brain), and EMG (muscles)—their frequency and amplitude ranges, and their importance in biomedical analysis.

Keywords

💡Bioelectric Signals

Bioelectric signals are electrical signals generated by cells in the human body due to the movement of ions across cell membranes. These signals are crucial for various physiological processes, such as the functioning of the heart, brain, and muscles. The video discusses how these signals originate and their importance in biomedical analysis.

💡Cell Membrane

The cell membrane is a semi-permeable barrier that surrounds the cell, controlling the movement of ions and molecules in and out of the cell. It plays a critical role in the development of bioelectric signals by allowing selective ion passage, leading to an electric potential difference across the membrane. This concept is central to understanding how bioelectric signals are generated.

💡Resting Potential

Resting potential refers to the electric potential difference across the cell membrane when the cell is not excited or stimulated. In the video, it is described as the condition where the inside of the cell membrane is negatively charged, and the outside is positively charged, typically around -90 millivolts. This state is foundational to the cell's ability to generate bioelectric signals.

💡Action Potential

Action potential is the change in electrical potential that occurs when a cell is excited or stimulated, such as during physical activity. The video explains that during this state, the inside of the cell membrane becomes positively charged, and the outside becomes negatively charged, with a typical value of +20 millivolts. Action potential is key to understanding how cells communicate and perform various functions.

💡Depolarization

Depolarization is the process by which the cell membrane's resting potential becomes less negative, leading to the generation of an action potential. This occurs when the cell is excited, causing a reversal of the charge distribution across the membrane. The video highlights depolarization as a critical step in the formation of bioelectric signals during physical activities.

💡Repolarization

Repolarization is the process by which the cell returns to its resting potential after being excited. This involves the restoration of the original charge distribution, with the inside of the cell becoming negative again. The video explains that this process occurs rapidly, within 3 to 4 milliseconds, and is essential for the cell to be ready for subsequent excitations.

💡Sodium and Potassium Ions

Sodium and potassium ions are cations (positively charged ions) that play a crucial role in the generation of bioelectric signals. The unequal distribution of these ions across the cell membrane is responsible for creating the electric potential. The video discusses how the movement of these ions contributes to the development of both resting and action potentials.

💡Chloride Ions

Chloride ions are anions (negatively charged ions) involved in the generation of bioelectric signals. These ions, along with sodium and potassium ions, contribute to the electric potential difference across the cell membrane. The video emphasizes the role of chloride ions in maintaining the balance of charges within and outside the cell, which is crucial for bioelectric signal generation.

💡Electrocardiography (ECG)

Electrocardiography (ECG) is the process of measuring the bioelectric signals generated by the heart, known as electrocardiogram signals. The video mentions ECG as a key application of bioelectric signal analysis, with a frequency range of 0.05 to 120 Hz and an amplitude range of 0.1 to 5 microvolts. ECG is essential for monitoring heart health and diagnosing cardiac conditions.

💡Electroencephalography (EEG)

Electroencephalography (EEG) is the process of measuring the bioelectric signals generated by the brain. The video describes EEG as a crucial tool for analyzing brain activity, with a frequency range of 0.1 to 100 Hz and an amplitude range of 2 to 200 microvolts. EEG is used in various medical fields to study brain function and diagnose neurological disorders.

Highlights

Introduction to the origination of bioelectric signals.

The smallest functional and structural unit of the human body, the cell, is crucial to the development of bioelectric signals.

Human body fluids contain key ions like sodium, potassium, and chloride, contributing to bioelectric signals.

Unequal distribution of ions across the cell membrane leads to the development of electric potential known as bioelectric potential.

The cell membrane behaves as a semipermeable membrane, allowing selective passage of ions, which creates electric potential.

Resting potential in a cell is around -90 millivolts, with a negative charge inside the cell membrane and a positive charge outside.

In the excited state, the charge distribution reverses, with a positive charge inside and a negative charge outside, generating action potential.

Action potential, generated during physical activity, has a value of approximately +20 millivolts.

The process of a cell returning from an excited state to a resting state is called repolarization.

The refractory period, typically 3 to 4 milliseconds, is the time taken for the cell to return to its resting state.

Key bioelectric signals in the human body include those from the heart (ECG), brain (EEG), and skeletal muscles (EMG).

Electrocardiography (ECG) measures the bioelectric signals of the heart, with a frequency range of 0.05 to 120 Hz.

Electroencephalography (EEG) measures brain signals, with a frequency range of 0.1 to 100 Hz and amplitude of 2 to 200 microvolts.

Electromyography (EMG) measures skeletal muscle signals, with a frequency range of 5 to 2 kHz and amplitude of 0.125 microvolts.

The importance of bioelectric signals in patient monitoring systems for identifying medical anomalies in the heart, brain, and muscles.

Transcripts

hello friends welcome to engineering

tutorial in today's video we are going

to discuss about some basic concepts

related to the origination of

bioelectric signals so we have already

discussed about the various types of

biomedical signals that are present in

the human body in today's video we are

going to discuss about one such signal

which is the bioelectric signals how do

they originate so the origin of

bioelectric signals is associated with

the smallest functional and structural

unit of the human body which is the cell

we all know it is the basic building

block the cells they combine to form

tissues tissues they combine to form

organs and our human body is just a

combination of various organs which

perform various tasks in a systematic

way so the human body is composed of

many cells almost trillions in numbers

and they vary in size from 1 micrometer

200 micrometer in diameter 0.1 micron in

thickness and one millimeter to 1 metre

in length ok so so much difference in

the thickness in the diameter and in the

length of the various cells that are

associated with the various body parts

so how does cell contribute to the

development of the bioelectric signals

so we know that the human body it is 70%

liquid 70% fluid and that fluid the body

fluids they contain several ions okay

mainly the principal ions that are

present in the body fluids are sodium ok

the sodium ions it is a cation the

potassium

which is also a cation

positively-charged and chloride it is an

anion okay it is negatively charged ion

now we know that when oppositely charged

particles are separated by a certain

distance an electric potential exists

between those oppositely charged ions so

here also these ions positively charged

ions and negatively charged ions the

unequal distribution of these ions

across the cell membrane leads to the

development of the electric potential

which is called as pyroelectric

potential now the cell it behaves as a

conductor an ionic conductor okay which

allows migration of certain ions and

prevents certain ions from passing so it

behaves as a semipermeable membrane okay

a selective ionic filter it allows some

ions to pass and blocks the passage of

certain ions which leads to an unequal

distribution of cations and anions

across the cell membrane now this leads

to the development of the action

potential which is called as the

electric potential now the electric

potential across the cell can be

visualized like this okay one side there

are positive charge which is sodium and

potassium and on the other side is

negatively charged which is

predominantly chloride now we know when

positive and negative charged are

separated the unequal distribution it

leads to the development of an electric

potential this is the same which happens

in the human cell so there are two

conditions in which the behavior of a

human cell is analyzed

first in the resting state or the unn

cited state and another one is in the

excited state two states so first let us

discuss the behavior of the cell in the

resting state now in the resting state

the cell has negative charge along the

inner surface of the cell membrane and

positive charge along the outer surface

okay this is the behavior of the cell

during the resting state as you can see

there is negative charge along the inner

surface in the inside of the cell

membrane and positive charge along the

outer side so this unequal distribution

of positive and negatively charged ions

leads to the development of an electric

potential which is called as a resting

potential okay in this condition the

potential which is developed between

these ions oppositely charged ions is

called as resting potential and the

value of it is generally minus 90 milli

volt okay - 90 millivolt so the

magnitude is very less milli volt of the

order of millivolts so in this condition

the cell is said to be in polarized

State okay this my unequal distribution

of charge carriers along the SEM a cell

membrane causes the development of the

resting potential which is about minus

90 millivolt now cell in the excited

state

now when we call a cell to be an excited

state for example when we walk when we

run when we wave our hand when we lift

any body part okay any simple activity

that we do which which is associated

with any part of the body the cells

associated with that body part get

excited for example when we walk the

cells associated with our legs they get

when we lift something the cells

associated with our hands they get

excited when we talk when we move our

jaws the upper and lower jaws the cells

associated with our face they get

excited they get stimulated so when the

cells associated with a particular body

part get excited or stimulated because

of any physical activity the outer side

of the cell becomes momentarily negative

and the inner side the same cell

membrane it becomes positive just the

opposite of that in the resting state

okay the inner side becomes positive it

acquires a positive charge and the outer

side acquires a negative charge this is

in the excited state just the opposite

of what in resting state in resting

state there is negative charge along the

inner side of the cell membrane positive

charge along the outer side in excited

state it is the opposite there is

positive charge in the along the inner

side and negative charge along the outer

side okay so in the excited state okay

in the excited state because of this

migration okay the the opposite which is

happening to that in the resting state

the electric potential which is

generated is called as action potential

okay this is the basic cause of the

various electric potential which is

generated by the various body parts the

action potential because of physical

activity now this action potential value

is generally plus 20 millivolt the

resting potential value is minus 90 way

volt the action potential value is plus

20 millivolt the resting potential is

generally is the electric potential

generated by the cells during the

unexcited State the resting state under

no physical activity but when it is

excited stimulated it acquires the value

of

plus 20 millivolt and this process is

called as depolarization in

resting-state

the process is called the cell to be in

polarized state an excited state it is

called as depolarize state okay

depolarization so this is the behavior

of the cells in the resting state

negative charge along the inner surface

positive charge along the outer surface

of the cell membrane and this is the

behavior of the cells in the excited

state positive charge along the inner

surface and negative charge along the

outer surface so just the opposite of

each other now now after being excited

or stimulated the cell again returns

back to its normal resting state it does

not stay in the excited state

indefinitely okay it does not stay

excited for a long period of time

it almost quickly returns back to its

normal resting state that is from this

state okay

from excited state again back to resting

state and acquires the resting potential

of minus 90 millivolt now this process

of the cell returning from resting state

to excited state sorry excited state to

resting state is called as

repolarization okay the process of the

cell after being excited or stimulated

again returning back to the resting

state is called as repolarization again

it acquires the resting potential which

is about minus 90 millivolt and the time

which it takes for returning back to the

resting state is called as a refractory

period which is generally about 3 to 4

milliseconds okay 3 to 4 milliseconds

refractory period is generally it varies

from 3 to 4 or 6 milliseconds ok so this

is a graph of the electric potential

changes during polar a depolarization

and repolarization of a cell

in the resting state this is the value

of the electric potential which is minus

90 millivolt during the resting state

whenever any physical activity takes

place when it is externally stimulated

or excited it acquires the action

potential plus 20 millivolt okay

this is during excitation and soon after

a few milliseconds generally 3 to 4

millisecond the electric potential again

drops back to the resting potential

minus 19 millivolt and it remains as it

is unless further excited or stimulated

so this is the behavior of the electric

potential associated with the cells so

the bioelectric signals are the main

bioelectric signals that are present in

the human body they are associated with

heart brain and the skeletal muscles ok

they are the main by electric signals

the electrical signal the bioelectric

signal associated with heart is called

as electro cardiogram signal and the

measurement technique is called as

electrocardiography the bioelectric

signal associated with brain is called

as electroencephalography EEG this is

called as ECG and those with skeletal

muscles is called as electromyography

EMG this is the frequency range of ECG

generally from point 0 5 to 120 Hertz

and the amplitude range is from point 1

to 5 micro volts it varies in between

that and for EEG the frequency range is

from point 1 200 Hertz and amplitude

range is from 2 to 200 micro volt it can

be more than that but this is the normal

range can be less or more than that then

for EMG it is 5 to 2 kilohertz to normal

range and then the amplitude range is

0.125 micro volt so these are the three

main bio electric signals that are used

in the biomedical analysis the

patient monitoring system for the

identification of any medical anomaly

associated with heart brain or the

muscular parts so this is all about the

bioelectric signals the origin of

bioelectric signals so we have discussed

about how the bioelectric signals

originate what is the reason

electric potential develops across cells

it is because of the unequal

distribution of positively and

negatively charged ions we also

discussed the behavior of the cell in

resting state exciting state excited

state and the cell again returning back

to the resting state from excited state

so I hope you liked this video and

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