Download BIOMEDICAL INSTRUMENTATION - Prof. Dr. Joyanta Kumar Roy

PROF. DR. JOYANTA KUMAR ROY
DEPARTMENT OF APPLIED ELECTRONICS &
INSTRUMENTATION ENGINEERING
NARULA INSTITUTE OF TECHNOLOGY
WWW.dr-joyanta-kumar–roy.com
SUBJECTS OF DISCUSSION
•
Introduction to Biomedical Instrumentation
•
Human Body
•
Physiology of Heart and Circulatory system
•
Physiology of Respiratory system
•
Physiology of Brain and Nervous system
•
Neurons and Bio-signals
The Module -1 course duration : 3 lectures
The lecture content will be available at http//www.dr-joyanta-kumar-roy.com
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BOOKS AND REFERENCES FOR STUDY
1. Hand Book of Biomedical Instrumentation, R S Khandpur, McGraw Hill
2.BioInstrumentation, John G. Webster, Wiley India
3.Biomedical Instrumentation & Measurement, Cronwell L, Pearson
4.Medical Instrumentation, Application and Design, Webster JS
5. Introduction to Biomedical Instrumentation and measurement, Astor B R, McMillan
6. Introduction to Biomedical Equipment Technology, Carr, Pearson
7. Biomedical Instrumentation, Chatterjee & Millar, Cengage Learning
8. Internet search engines like : Google, Bing etc.
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Human Machine
Finest Technology
Of the world
Greatest creation of
God
Best creature of the
Planet
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HUMAN BODY
The human body is the entire structure of a human organism, and consists of a head, neck, torso,
two arms and two legs. By the time the human reaches adulthood, the body consists of close to
100 trillion cells, the basic unit of life. These cells are organized biologically to eventually form the
whole body.
Organ System:
The organ systems of the body include the musculoskeletal system, cardiovascular system,
digestive system, endocrine system, integumentary system, urinary system, lymphatic system,
immune system, respiratory system, nervous system and reproductive system.
Constituents of the human body
In a normal man weighing 60 kg
Constituent
Weight [2]
Percent of atoms[2]
Oxygen
38.8 kg
25.5%
Carbon
10.9 kg
9.5%
Hydrogen
6.0 kg
6.3%
Nitrogen
1.9 kg
1.4%
Calcium
1.2 kg
0.2%
Phosphorus
0.6 kg
0.2%
Potassium
0.2 kg
0.07%
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CARDIOVASCULAR SYSTEM
The cardiovascular system comprises the heart, veins, arteries and capillaries. The
primary function of the heart is to circulate the blood, and through the blood, oxygen
and vital minerals are transferred to the tissues and organs that comprise the body.
The left side of the main organ (left ventricle and left atrium) is responsible for
pumping blood to all parts of the body, while the right side (right ventricle and right
atrium) pumps only to the lungs for re-oxygenation of the blood. The heart itself is
divided into three layers called the endocardium, myocardium and
epicardium,(liquidation) which vary in thickness and function.
Anterior (frontal) view of the opened heart. White arrows indicate normal
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blood flow.
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The cardiovascular system is a complex hydraulic system, which performs the essential service of
transportation of oxygen, carbon-di-oxide, numerous chemical compounds and blood cells.
Structurally, the Heart is divided into right and left parts. Each parts has two chambers called
atrium and ventricle.
The
1.
2.
3.
4.
Heart has four valves:
The Tricuspid valve or Right atria-ventricular valve
Bicuspid mitral valve or Left atria-ventricular valve
Pulmonary valve
Aortic Valve
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Heart valve
location
Function
The Tricuspid valve
Between right atrium &
ventricle
Prevent backward flow of
blood from right ventricle to
right atrium
Bicuspid mitral valve
Between left atrium & left
ventricle
Prevents backward flow of
blood from left ventricle to
left atrium
Pulmonary valve
At the right ventricle
Does not allow blood to
come back at right
ventricle
Aortic Valve
Between left ventricle and
aorta
Prevents the return of
blood to the left ventricle
from Aorta
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THE HEART WALL
The pericardium:
Outer layer of Heart. It keeps the outer
surface moist and prevent friction due to
Heart beats
The myocardium:
Middle layer of the Heart, which made of
short cylindrical muscle fibers. The muscle is
automatic in action, contracting & relaxing
rhythmically through out the life.
The endocardium:
The inner layer of the Heart provides smooth
lining for blood flow
Consist of 3 layers
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ENGINEERING POINT OF VIEW
Fig: Circulatory system
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Blood transport mechanism
The blood is carried to the various parts of the body(organs) through Blood vessels. The blood
vessels are classified into:
1.
2.
3.
Arteries : The arteries are thick walled and they carry the oxygenated blood away from the
Heart
Veins: They are thin walled and they carry deoxygenated blood with carbon di oxide towards
heart
Capillaries :Smallest and the last level of blood vessels which supply food and oxygen to the
organs.
From the engineering point of view Heart act as pump and drives blood through blood vessels
of the circulatory system consist of four chamber muscular pump that beats 72 per minutes
on an average for normal adult, sending blood to every part of the body. The pump act as two
synchronized but functionally isolated two stage pump. The first stage of each pump (Atrium)
collects blood from hydraulic system and pumps to the second stage (the ventricle). In this
process the heart pumps the blood through pulmonary circulation to the lungs and through
the systematic circulation to the other parts of the body.
Pulmonary circulation: The venous deoxygenated blood flows from right ventricle to the
pulmonary artery to the lungs, where it is oxygenated and gives of carbon di oxide. The
oxygenated blood then flows through pulmonary veins to the left atrium.
Systematic Circulation: The blood is forced through blood vessels which are elastic. The
blood flows through left atrium to left ventricle and is pumped through aorta and its
branches the arteries to the out of the bodies. Through arterioles (Small and fine arteries) the
blood is distributed through capillaries to the human body organs. Where it gives up oxygen
and other relevant chemical compounds and taken up carbon di oxide and product of
combustion.
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The blood returns to the heart from different routes. It usually passes from the Venus side of the
capillaries. The heart itself is supplied by two small but highly important arteries, called Coronary
arteries. If they blocked by Coronary Thrombosis, Myocardial infraction follows, often leading to fatal
situation.
The Heart rate is partially controlled by autonomic nervous system and partially by Hormone action.
These control the heart pump’s speed, efficiency and blood flow pattern through the system.
The circulatory system is the Transport mechanism by which body takes food, oxygen, water and other
essentials are transported to the tissue cells and their waste product are transported away. This
happens through the diffusion process, in which nourishment from blood cells diffuses through
capillary wall into the interstitial fluid. Similarly carbon di oxide and waste product from interstitial
fluid diffuses through wall to the blood cell.
The condition of the Cardio vascular system is examined by the hemodynamic measurement and
recording the electrical activity of Heart muscles (Electro cardiography)
For assessing the performance of Heart as a pump, the measurement of cardiac output (amount of
blood flow per unit time)i.e by measuring blood pressure and flow at various location of the
Circulatory system
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THE END
OF
INTRODUCTION TO THE CARDIOVASCULAR
SYSTEM
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THE PHYSIOLOGY OF
RESPIRATION
This presentation takes you through the basic anatomy and physiology of
the respiratory system
You can complete the questions in your GM402M workbook as you work
through this presentation
Keep clicking your mouse to take you through the presentation
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WHY DO WE NEED TO
BREATHE?
Breathing gets oxygen into the body so that cells can make energy
Cells use this energy to contract muscles and power the thousands of
biochemical reactions that take place in the cell every second
Without oxygen, cells can’t make energy and without energy, cells would die
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IMPORTANT CONCEPT
The supply of blood and oxygen to cells and tissues is called
PERFUSION
If perfusion stops then cells die
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ENERGY PRODUCTION
Inside the cells most energy is made by the mitochondria. This energy is
in the form of ATP*
In the process of energy production………

Oxygen is consumed by the cells

Carbon dioxide is produced as a waste gas

Glucose fuels the process
*adenosine triphosphate – a small packet of
energy
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HOW DO CELLS GET THEIR
OXYGEN?
Oxygen (O2) from the air in the lungs diffuses into the blood
It is transported in the blood to the cells
Oxygen diffuses from the blood into the cells
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HOW DO CELLS DISPOSE OF
THEIR CARBON DIOXIDE?
Carbon dioxide (CO2) from the cells diffuses into the blood
It is transported in the blood to the lungs
In the lungs carbon dioxide diffuses into the air and is breathed out
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MOVEMENT OF O2 AND CO2
BETWEEN LUNGS AND CELLS
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THE ANATOMY OF THE
RESPIRATORY SYSTEM
The respiratory system consists of a series of tubes that transfer air
from outside the body to the small air sacs in the lungs where gas
exchange take place – the alveoli
The diagram on the next page shows the basic layout of the system –
label the diagram in your workbook
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Look at the
structure of the
respiratory
system and label
the diagram in
your workbook
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ALVEOLI
At the end of the smallest bronchioles are the alveoli
There are millions of alveoli in each lung
Alveoli are surrounded by a network of small blood vessels called
capillaries
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ALVEOLI AND ADJACENT
CAPILLARIES
alveoli
terminal bronchiole
capillaries
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GAS EXCHANGE IN THE ALVEOLI
Oxygen diffuses from the alveoli to the blood in the capillaries
Carbon dioxide diffuses from the blood in the capillaries to the
alveoli
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WHAT IS DIFFUSION?
Diffusion is a process that occurs when there is a difference in the
concentration of a substance between two areas
The substance, for example oxygen, will diffuse from an area of high
concentration to an area of low concentration
No energy is required from the body for this process
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VENTILATION (BREATHING)
Breathing air in and out of the lungs –
As the ribs rise and fall and the diaphragm domes and flattens, the
volume and pressure in the lungs changes
It is the changes in pressure that cause air to enter and leave the
lungs
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VENTILATION (BREATHING)
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VENTILATION (BREATHING)
Inspiration (breathing in)
•Ribs rise and diaphragm flattens
•Volume increases and pressure decreases
•Air enters the lungs
Expiration (breathing out)
•Ribs fall and diaphragm domes
•Volume decreases and pressure increases
•Air leaves the lungs
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CONTROL OF VENTILATION
As we exercise, the body needs to obtain more oxygen and remove
more carbon dioxide (CO2)
This is done by increasing the rate and depth of breathing
An increase in carbon dioxide in the blood is the main trigger that
increases the rate and depth of breathing
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CONTROL OF VENTILATION
Chemoreceptors in the respiratory centre in the brain stem’s medulla
detect an increase in blood CO2 levels
The intercostal and phrenic nerves increase the rate and depth of
breathing
Additional chemoreceptors on arteries near the heart
monitor oxygen and blood acidity
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Control of Respiration
chemoreceptors
on aorta and
carotid artery
brain
respiratory
centres in
medulla
heart
intercostal
nerve to
external
intercostal
muscles
phrenic
nerve to
diaphragm
ribs
diaphragm
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RESPONSE TO HYPERCAPNIA
Diseases such as emphysema, bronchitis and asthma can
impede the movement of gas between the alveoli and the blood
CO2 levels can build up in the blood – known as hypercapnia
This stimulates the chemoreceptors in the respiratory centre
of the brain
The rate and depth of breathing increases to expire more CO2
and reduce levels in the blood
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The Physiology of
NERVOUS SYSTEM
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Central Nervous System:
“CNS”
Spinal Cord
Brain
THE SPINAL CORD
Foramen magnum to L1 or L2
Runs through the vertebral canal of the vertebral
column
Functions
1.
2.
3.
Sensory and motor innervation of entire body inferior
to the head through the spinal nerves
Two-way conduction pathway between the body and
the brain
Major center for reflexes
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Spinal cord
http://www.apparelyzed.com/spinalcord.html
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PROTECTION:
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ANATOMICAL CLASSIFICATION
Cerebral hemispheres
Diencephalon
 Thalamus
 Hypothalamus
Brain stem
 Midbrain
 Pons
 Medulla
Cerebellum
Spinal cord
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PARTS OF BRAIN
Cerebrum
Diencephalon
Brainstem
Cerebellum
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SIMPLIFIED…
Back of brain: perception
Top of brain: movement
Front of brain: thinking
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CEREBRAL HEMISPHERES
Lobes: under bones of same name
 Frontal
 Parietal
 Temporal
 Occipital
 Plus: Insula (buried deep in lateral sulcus)
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HOMUNCULUS – “LITTLE MAN”
Body map: human body spatially represented
 Where on cortex; upside down
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PREFRONTAL CORTEX: COGNITION
This area is remodeled during adolescence until the age of 25 and is very important for
well-being; it coordinates the brain/body and inter-personal world as a whole
Intellect
Abstract ideas
Judgment
Personality
Impulse control
Persistence
Complex
Reasoning
Long-term
planning
Social skills
Appreciating
humor
Conscience
Mood
Mental
flexibility
Empathy
Executive functioning
e.g. multiple step problem solving
requiring temporary storage of
info (working memory)
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RETICULAR FORMATION
Runs through central core of medulla, pons and midbrain
Reticular activating
system (RAS):
keeps the cerebral
cortex alert and
conscious
Some motor control
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THE END
OF
PHYSIOLOGY OF HUMAN BRAIN & NERVOUS
SYSTEM
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Biomedical signals: Origins and dynamic
characteristics
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BIOMEDICAL SIGNALS:
ORIGIN AND DYNAMIC CHARACTERISTICS
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NEURONS AND SYNAPSES
Types of Neurons
Sensory
Motor
Interneurons
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SENSORY NEURONS
• INPUT From sensory organs to the brain and spinal cord.
Drawing shows a
somatosensory neuron
Vision, hearing, taste and
smell nerves are cranial,
not spinal
Sensory
Neuron
Brain
Spinal
Cord
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MOTOR NEURONS
• OUTPUT From the brain and spinal cord To the
muscles and glands.
Sensory
Neuron
Brain
Spinal
Cord
Motor
Neuron
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INTERNEURONS
Interneurons carry information between other neurons only found
in the brain and spinal cord.
Sensory
Neuron
Brain
Spinal
Cord
Motor
Neuron
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STRUCTURES OF A NEURON
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THE CELL BODY
Contains the cell’s Nucleus
 Round, centrally located structure
 Contains DNA
 Controls protein manufacturing
 Directs metabolism
 No role in neural signaling
57
DENDRITES
•
Information collectors
•
Receive inputs from neighboring
neurons
•
Inputs may number in thousands
•
If enough inputs the cell’s AXON may
generate an output
58
DENDRITIC GROWTH
•
Mature neurons generally can’t divide
•
But new dendrites can grow
•
Provides room for more connections
to other neurons
•
New connections are basis for
learning
59
AXON
The cell’s output structure
One axon per cell, 2
distinct parts
 tubelike structure branches at end that
connect to dendrites of other cells
60
MYELIN SHEATH
•
White fatty casing on axon
•
Acts as an electrical insulator
•
Not present on all cells
•
When present increases the speed of
neural signals down the axon.
Myelin Sheath
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HOW NEURONS COMMUNICATE
Neurons communicate by means of an electrical
signal called the Action Potential
Action Potentials are based on movements of ions
between the outside and inside of the cell
When an Action Potential occurs a molecular
message is sent to neighboring neurons
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PLASMA MEMBRANE
FUNCTION OF PLASMA MEMBRANE
• Oxygen, carbon di oxide and water can easily cross plasma membrane
• large molecule and ions only can move through protein channel
63
WATER
+ ,Cl-
outside
Na+ 10
------= ---K+
1
Na+ 1
------= ---K+
30
WATER
+ ,Cl-
K
Inside
Cell membrane
Inside
Cell membrane
K
108 mM Cata ions
12mM Na+
125mM K+
5mM Cloutside
Intra-cellular Fluid
Extra-cellular Fluid
120mM Na+
5mM K+
125mM Cl-
64
ION CONCENTRATIONS
Outside of Cell
K+
Na+
Cl-
Cell Membrane in resting state
K+
Na+
Cl-
Inside of Cell
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THE CELL MEMBRANE IS SEMIPERMEABLE
K+
Na+
Cl-
Outside of Cell
Cell Membrane at rest
K+
Na+
Cl-
- 70 mv
A-
Inside of Cell
Potassium (K+) can
pass through to
equalize its
concentration
Sodium and
Chlorine cannot
pass through
Result - inside is
negative relative to
outside
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RESTING POTENTIAL
-90mV
(a) Polarized Cell
•
At rest the inside of the cell is at -70 milli volts
•
With inputs to dendrites inside becomes more positive
•
if resting potential rises above threshold an action potential starts to travel from
cell body down the axon
•
Figure shows resting axon being approached by an AP
67
DEPOLARIZATION AHEAD OF AP
-90mV
(a) De-polarized Cell
• AP opens cell membrane to allow sodium (NA+) in
• inside of cell rapidly becomes more positive than outside
• this depolarization travels down the axon as leading edge of the AP
68
REPOLARIZATION FOLLOWS
•
After depolarization potassium (K+) moves out restoring the inside to a
negative voltage
•
This is called repolarization
•
The rapid depolarization and repolarization produce a pattern called a
spike discharge
69
FINALLY, HYPERPOLARIZATION
• Repolarization leads to a voltage below the resting potential, called
hyperpolarization
• Now neuron cannot produce a new action potential
• This is the refractory period
70
RESTING POTENTIAL
• Recall the definition of VM from the muscle lectures.
• Neurons are also highly polarized (w/ a VM of about –
70mV) due to:
»Differential membrane permeability to K+ and Na+
»The electrogenic nature of the Na+/K+ pump
»The presence of intracellular impermeable anions
• Changes in VM allow for the generation of action
potentials and thus informative intercellular
communication.
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GRADED POTENTIALS
Let’s consider a stimulus at the dendrite of a neuron.
The stimulus could cause Na+ channels to open and this
would lead to depolarization. Why?
However, dendrites and somata typically lack voltage-gated
channels, which are found in abundance on the axon
hillock and axolemma.
 So what cannot occur on dendrites and somata?
Thus, the question we must answer is, “what does this
depolarization do?”
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GRADED POTENTIALS
The positive charge carried by the Na+ spreads as a wave of
depolarization through the cytoplasm (much like the ripples
created by a stone tossed into a pond).
As the Na+ drifts, some of it will leak back out of the
membrane.
 What this means is that the degree of depolarization caused by the
graded potential decreases with distance from the origin.
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GRADED POTENTIALS
Their initial amplitude may be of almost any size – it
simply depends on how much Na+ originally entered
the cell.
If the initial amplitude of the GP is sufficient, it will
spread all the way to the axon hillock where V-gated
channels reside.
If the arriving potential change is suprathreshold, an
AP will be initiated in the axon hillock and it will
travel down the axon to the synaptic knob where it
will cause NT exocytosis. If the potential change is
subthreshold, then no AP will ensue and nothing will
happen.
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NERNST POTENTIAL
The chemical potential gradient due to different
concentrations
between inside and outside of the cell is given by
NERNST RELATION
ENS = NERNST POTENTIAL = 61.6
Where
u-v
u+v
u = Mobility of cataions ( Negative ions)
v = Mobility of Anaions (Positive ions)
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ELECTRICAL EQUIVALENT CIRCUIT OF CELL MEMBRANE
Inside of the cell
1 KΩ
RK
38 KΩ
C
R Na
R Nad
1 50KΩ
EK
91mV
EK = 61.6 log (30/1) = 91 mV Nernst Potential when Polarized
E na = 61.6 log (10/1) = 62 mV Nernst Potential when Depolarized
E Na
62mV
Out side of the cell
C = Capacitance of the Cell
RK = Relative permeability of the membrane to the flow of K+ ion
R Na = Relative permeability of the membrane to the flow of Na+
ion at polarized condition
R Nad =Relative permeability of the membrane to the flow of
Na+ ion at De-polarized condition
Net K Current + Net Na Current = 0
Net K Gradien Net na Gradient
+
=
RK
Rna
EK + EC
-Ena + EC
+
=0
RK
Rna
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ACTION POTENTIALS
If VM reaches threshold, Na+ channels open and Na+ influx
ensues, depolarizing the cell and causing the V M to increase.
This is the rising phase of an AP.
Eventually, the Na+ channel will have inactivated and the K+
channels will be open. Now, K+ effluxes and repolarization
occurs. This is the falling phase.
 K+ channels are slow to open and slow to close. This causes the VM to take
a brief dip below resting VM. This dip is the undershoot and is an example of
hyperpolarization.
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NA+ CHANNELS
1
They have 2 gates.
 At rest, one is closed (the
activation gate) and the other
is open (the inactivation gate).
 Suprathreshold depolarization
affects both of them.
2
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3
4
5
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ABSOLUTE REFRACTORY PERIOD
During the time interval between the opening of the
Na+ channel activation gate and the opening of
the inactivation gate, a Na+ channel CANNOT be
stimulated.
 This is the ABSOLUTE REFRACTORY PERIOD.
 A Na+ channel cannot be involved in another AP until the
inactivation gate has been reset.
 This being said, can you determine why an AP is said to be
unidirectional.
 What are the advantages of such a scenario?
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RELATIVE REFRACTORY PERIOD
Could an AP be generated during the undershoot?
 Yes! But it would take an initial stimulus that is much, much stronger than usual.
 WHY?
 This situation is known as the relative refractory period.
Imagine, if you will, a toilet.
When you pull the handle, water floods the bowl. This event takes a
couple of seconds and you cannot stop it in the middle. Once the bowl
empties, the flush is complete. Now the upper tank is empty. If you try
pulling the handle at this point, nothing happens (absolute refractory).
Wait for the upper tank to begin refilling. You can now flush again, but
the intensity of the flushes increases as the upper tank refills (relative
refractory)
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In this figure, what do the red
and blue box represent?
VM
TIME
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SOME ACTION POTENTIAL QUESTIONS
What does it mean when we say an AP is “all or none?”
 Can you ever have ½ an AP?
How does the concept of threshold relate to the “all or none” notion?
Will one AP ever be bigger than another?
 Why or why not?
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ACTION POTENTIAL CONDUCTION
If an AP is generated at the axon hillock, it will
travel all the way down to the synaptic knob.
The manner in which it travels depends on
whether the neuron is myelinated or
unmyelinated.
Unmyelinated neurons undergo the continuous
conduction of an AP whereas myelinated
neurons undergo saltatory conduction of an AP.
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CONTINUOUS CONDUCTION
Occurs in unmyelinated axons.
In this situation, the wave of de- and repolarization simply
travels from one patch of membrane to the next adjacent
patch.
APs moved
in this
fashion
along the
sarcolemma
of a
muscle
fiber as well.
Analogous to
dominoes
falling.
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SALTATORY CONDUCTION
Occurs in myelinated axons.
Saltare is a Latin word meaning “to leap.”
Recall that the myelin sheath is not completed. There exist myelin
free regions along the axon, the nodes of Ranvier.
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RATES OF AP CONDUCTION
1. Which do you think has a faster rate of AP
conduction – myelinated or unmyelinated axons?
2. Which do you think would conduct an AP faster – an
axon with a large diameter or an axon with a small
diameter?
The answer to #1 is a myelinated axon. If you can’t see why, then answer this
question: could you move 100ft faster if you walked heel to toe or if you bounded in
a way that there were 3ft in between your feet with each step?
The answer to #2 is an axon with a large diameter. If you can’t see why, then answer
this question: could you move faster if you walked through a hallway that was 6ft
wide or if you walked through a hallway that was 1ft wide?
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NEURON TO NEURON
•
Axons branch out and end near
dendrites of neighboring cells
•
Axon terminals are the tips of the
axon’s branches
•
A gap separates the axon terminals
from dendrites
•
Gap is the Synapse
Dendrite
Axon
Cell
Body
90
SYNAPSE
•
Sending
Neuron
axon terminals contain small
storage sacs called synaptic
vesicles
91
Axon
Terminal
Synapse
vesicles contain
neurotransmitter
molecules
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NEUROTRANSMITTER RELEASE
Action Potential causes vesicle to open
 Neurotransmitter released into synapse
 Locks onto receptor molecule in postsynaptic
membrane
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LOCKS AND KEYS
Neurotransmitter molecules
have specific shapes
 Receptor molecules have
binding sites
 When NT binds to
receptor, ions enter
positive ions (NA+ )
depolarize the neuron
negative ions (CL-)
hyperpolarize
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SOME DRUGS WORK ON RECEPTORS
•
Some drugs are shaped like
neurotransmitters
•
Antagonists : fit the receptor but poorly
and block the NT
– e.g. beta blockers
 Agonists : fit receptor
well and act like the NT
e.g. nicotine.
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THE END
OF
MODULE -1
DR. J. K. ROY
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