AN INTRODUCTION TO BIOPHYSICS

Prof. Dr. Moustafa. M. MohamedVice Dean

Faculty of Allied Medical SciencePharos University

Alexandria

Dr. Yasser khedrBasic Science DepartmentFaculty of Physical therapy

Pharos University in Alexandria

Electricity

Within The

Body

ch1

Cardio Vascular

Instrumentation

ch2

Heat In

Medicine

ch3

Ultrasound In

Medicine And

Biology

ch4

TOPICS

Laser In

Medicine

And Biology

ch5

Human vision

ch5

Nuclear

Medicine

ch6

TOPICS

CALENDARDate Week Lecture 1

29-9-2012 1 About the biophysics

6-10-2012 - Vacation

13-10-2012 3 Ch 1

20-10-2012 4 Ch 1

27-10-2012 5 Ch 2

3-11-2012 6 Ch 2

10-11-2012 7 Ch 3

17-11-2012 8 Ch 3

24-11-2012 9 Revision

CALENDAR

Date Week Lecture 1 1-12-2012 10 Med term exam

8-12-2012 11 Ch 4

15-12-2012 12 Ch 4

22-12-2012 13 Ch 5

29-12-2012 14 Ch 5

5-1-2014 15 Ch 6

12-1-2014 15 Revision

******** ** Final Exam

What Is Biophysics?

Link BetweenBiology Physics

BIOPHYSICS

Biophysics

1. Biophysics is a bridge between

biology and physics.

2. biophysics is the study of

biological systems and

biological processes using

physics-based methods or based

on physical principles.

How Essential Is Biophysics To Progress In Biology?

1. Biophysics discovers how atoms

are arranged to work in DNA and

proteins.

2. Biophysicists are discovering how

proteins work, they use these

protein structures for discovering

how biological machines work, in

health and also in diseases.

How Essential Is Biophysics To Progress In Biology?

3. Variations in proteins make people

respond to drugs differently.

Understanding these differences

opens new possibilities in drug

design, diagnosis, , disease control

and decrease of side effects.

What Are The Applications Of Biophysics?

1. The applications of biophysics depend on society’s needs.

2. In the 20th century, great progress was made in treating disease. Biophysics helped create powerful vaccines against infectious diseases.3. It described and controlled diseases of metabolism, such as diabetes.4. Biophysics provided both the tools and the understanding for treating the diseases of growth known as cancers.

What Are The Applications Of Biophysics?

5. Biophysical methods are increasingly used to serve everyday needs, from forensic science to bioremediation6. Biophysics gives us medical imaging technologies including MRI, CAT scans and sonograms for diagnosing diseases.7. It provides the life-saving treatment methods of kidney dialysis, radiation therapy, cardiac defibrillators, and pacemakers.

Why Is Biophysics Important Right Now?1. Biophysics discovers how to modify microorganisms for biofuel (replacing gasoline and diesel fuel) and bioelectricity (replacing petroleum products and coal for producing electricity).2. Biophysics discovers the biological cycles of heat, light, water, carbon, nitrogen, oxygen, heat, and organisms throughout our planet.3. Biophysics harnesses microorganisms to clean our water and to produce lifesaving drugs.

Instrumentation AND Biophysical Methods. Measuring systems are used to provide quantitative information about parameters of biological importance.Such parameters may include bio potentials from muscles, neurons, eye, heart or brain, blood pressure or muscle forces. The signal may take different forms, such as being mechanical or electrical.. Electrical signals are the most popular and they have to be well treated so as to eliminate unwanted signals and amplified to be displayed

Examples of Electric Signals• Electrical potentials of nerves.• Electrical signals from muscles the electro-

myogram.• Electrical signal from the heart the electro-

cardiogram.• Electrical signal from the brain the electro-

encephalogram.• Electrical signal from the eye the electro-

retinogram and the electro oculogram.

Cardiovascular Instrumentation

• Bio potentials of the heart.• Electrodes.• Amplifiers.• Patient monitoring.• Defibrillators.• Pacemakers.

Applications Of Electricity And Magnetism In Medicine

• Electrical shock .• High frequency electricity in medicine.• Low frequency electricity and

magnetism in medicine.• Current research involving electricity

applied in the body.

Sound In Medicine

• General properties of the sound.• The body as a drum (percussion in

medicine).• Ultrasound pictures of the body.• Ultrasound measure motion.• Physiological effects of ultrasound in

therapy.• The production of speech (phonation).

Physics Of Ear And Hearing

• The outer ear.• The middle ear.• The inner ear.• Sensitivity of the ears.• Testing your hearing.• Deafness and hearing aids.

Light In Medicine

• Measurement of light and its units.• Applications of visible light in medicine.• Applications of ultraviolet and infrared

light in medicine.• Laser in medicine.• Application of microscopes in medicine.

Physics Of Eyes And Vision

• Focusing elements of eye.• Diffraction effects on the eye.• Defective vision and its correction.• Color vision and chromatic

aberration.• Instruments used in ophthalmology.

Physics Of Diagnostic X-ray

• Production of X-ray beam.• How X-ray are absorbed.• Making an X-ray image.• Radiation to patient from X-rays.• X-ray slices of the body.

Physics Of Radiation Therapy:

• The dose units used in radiotherapy are the rad and gray.

• Principles of radiation therapy.• A short course in radiotherapy treatment

planning.• Megavoltage therapy.

Heat And Cold In Medicine

• Physical basis of heat and temperature.• Thermometry and temperature scales.• Thermography mapping the body’s

temperature.• Heat therapy.• Use of cold in medicine.• Cryosurgery.

TUTORIAL BIOPHYSICS

INTRODUCTION OF ELECTRICITY

Dr : Yasser Ibrahim KhedrLecturer Assistant : Bohaysa

SalemBasic Science DepartmentFaculty of Physical therapy

Pharos University in Alexandria

Basic Electric Circuit Concepts

What is electricity?

Electricity is the set of physical phenomena associated with the presence and flow of electric charge.

cell switch

lamp

wires

Electric chargeThere are two types of electric charges – positive and negative.

Ion is an atom that has lost one or more electrons, giving it a net positive charge (Cation)Example : Sodium, Calcium, Potassium, and Magnesium

or that has gained one or more electrons, giving it a net negative charge (Anion). Example : Chloride, Sulfate, Phosphate, Bicarbonate

Movement or flow of electrically charged particles, typically measured in amperes. The unit of current is the ampere (A).

1 ampere = 1 coulomb/second

3

Basic Electric Circuit Concepts

QI=

t

Current

Voltage

a force that pushes the current through the circuit.

Suppose one coulomb of charge is located at point b and one joule of energy is required to move the charge to point a. Then we say that Vab = 1 volt = 1 joule/coulomb = 1 Newton.meter/coulomb.

5

Basic Electric Circuit Concepts

Friction that impedes flow of current through the circuit (rocks in the river)

Ohm’s Law

I = Current (Amperes) (amps)

V = Voltage (Volts)

R = Resistance (ohms)

Resistance:

Basic Electric Circuit Concepts

V=I.R

Another way to find resistance

The resistance varies directly with length and inversely with width (or cross-sectional area)

Short, thick wire small resistance Long, skinny wire large resistance

ρ.LR=

A

1ρ=

σ

r= Resistivity σ= Conductivity

Measuring Resistance

We can find the resistance of a component by measuring

voltage across the component using a voltmeter

current through the component using an ammeter

Measuring Resistance

or we can measure it directly using an

ohmmeter

Ω

Calculate the resistance of auniform wire of a diameter 0.32mm and length 5.0m , the resistivity of awire 5x10-7 Ωm

Solution

A=Pi r2

r=0.00016R=5.0 x10-7 x 5/(Pi x 0.000162)

R=31Ω

ρ.LR=

A

Example 1:

Solution

r = 0.14mm = 0.00014mL = 1.50 m, R = 45, A = 6.15x10-8

ρ = 45x(6.15x10-8 /a.5)=0.0000018=1.8x10-6 Ω .m

L=1x(6.15x10-8 /1.8x10-6 )=0.034 m

A wire of uniform diameter 0.28 mm and length a.50m has a resistance of 45Calculate1- its resistivity2- the length of wire that has a resistance of 1.0

Example 2:

Simple Circuits Series circuit

All in a row 1 path for

electricity 1 light goes out

and the circuit is broken

Parallel circuit Many paths for

electricity 1 light goes out and

the others stay on

Series and Parallel Circuits

What is the relationship between the three currents?What type of circuit is this?

The current is the same at each point.

321 III

What is the relationship between the four voltages?

They add to equal the supply voltage.

321 VVVVs How do you find total resistance in series?

Add each resistance together.

321 RRRRtotal

What type of circuit is this?

What is the relationship between the four currents?

The four currents add to give the total current.

321 IIIIT What is the relationship between the four voltages?

Each voltage is equal to the supply voltage.

321 VVVVS

The resistance in parallel?

321

1111

RRRRT

Find the total resistance of R1=2Ω, R2=5Ω and R3=7Ω if connected in series then in parallel

Solution In series

=2+5+7 =14 Ω

In parallel

=1/2 +1/5 +1/7 =1.2 Ω321

1111

RRRRT

321 RRRRtotal

Capacitors

A basic capacitor has two parallel plates separated by an insulating material

A capacitor stores an electrical charge between the two plates

The unit of capacitance is Farads (F) Capacitance values are normally smaller, such as

µF, nF or pF

Capacitors Basic capacitor construction

Dielectric material

Plate 1

Plate 2

The dielectric material is an insulator therefore no current flows through the capacitor

Capacitors

Storing a charge between the plates

Electrons on the left plate are attracted toward the positive terminal of the voltage source

This leaves an excess of positively charged holes

The electrons are pushed toward the right plate

Excess electrons leave a negative charge

A charged parallelplate capacitor.

Q = C V where C = ɛo A / d

for a parallel plate capacitor, where ɛo is the permittivity of the

insulating material (dielectric) between plates.

The unit of capacitance is called the Farad (F).

1 / CT = 1 / C1 + 1 / C2

11

Two capacitors in series and the equivalent capacitor.V = V1 + V2 and Q = C V

CT= C1 + C2 Two capacitors in parallel and

the equivalent capacitor.

Q = Q1 + Q2 and Q = C V

Two capacitors, C1= 5.00 µF and C2= 12.0 µF, are connected in parallelWhat is the equivalent capacitance of the combination?

Solution

C1=5 µF =5x10-6 F

C2= 12.0 µF =12x10-6 F

In parallelCeq=C1+C2

= 5x10-6 + 12x10-6 =17x10-6 F

Reference• Text books• First – Title: Physics in Biology and Medicine, – Author: Paul Davidovits• Second – Title: Medical Physics – Author: Martin Hollins• Third – Title: Medical Physics – Author: John R. Cameron and James G. Shofronck• Fourth – Title: General Physics – Morton M. Sternheim and Joseph W. Kane