Bio-Medical Instrumentation

Sources

Bio Chemical Cardiovascular Respiratory Nerves Measurement Systems

Bio-Chemical

Energy to activate bodyWith Intake of

Food

Water

air

Support Messenger agent material for

growth

repair of parts of body

Cardiovascular

Closed Hydraulic system Four Valves Pump Heart connected to flexible/elastic tubing Blood VesselsFunction

Transportation of Oxygen , Co2

Heart drives blood 72 times/hr

Activities monitored by Electro - cardiography

Respiratory

Pneumatic system Air pump Diaphragm create +ve and ve pressure in sealed chamber Thoractic cavity Cause air to be sucked and forced out Oxygen is taken into blood and Co2 is transferred from blood to air

Nervous system

Communication network Brain is Central information processor

Memory

Computational

Decision making

I/O Channel

Central Part-- Encephalon and Spinal cord Peripheral part- Nerves and group of nerves

Brain

Cerebrum responsible for

hearing

sight

touch

Volume muscle control

Cerebellum

Intercept sensors

Motor nerves

Smooth out , avoid jerking motions

Bio-Medical Instrumentation

Involves Study of

Action PotentialBio- Potential electrodes

Recording Systems

ECG,EEG,EMG

Exploratory Systems

X-Rays Machines, Ct Scanners, MRI and Ultrasonic Imaging Systems

Nervous System

The brain communicates with the rest of the body through the spinal cord and the nerves.

Each nerve is a bundle of hundreds or thousands of neurons (nerve cells).

The spinal cord runs down a tunnel of holes in your backbone or spine.

The cord is a thick bundle of nerves, connecting your brain to the rest of your body.

Brain

Spinal Cord

Nervous System

The nervous system is made up of nerve cells or neurons that are "wired" together throughout the body. Neurons carry messages in the form of an electrical impulses. The messages move from one neuron to another to keep the body functioning.

The axon of one neuron doesn't touch the dendrites of the next. Nerve signals have to jump across a tiny gap. To get across the gap they have to change from electrical signals into chemical signals then back into electrical signals.

*

Action Potentials

*

Resting Cell Membrane Potential

*

The potential difference (70 mV) across the membrane of a resting neuronIt is generated by different concentrations of Na+, K+, Cl, and protein anions (A)Ionic differences are the consequence of:Differential permeability of the membrane to Na+ and K+

Membrane Potential

*

The outside (extracellular) face is positive, while the inside face is negativeThis difference in charge is the resting membrane potentialThe predominant extracellular ion is Na+The predominant intracellular ion is K+The sarcolemma is relatively impermeable to both ions

Electrical Conditions of a Polarized Sarcolemma

*

Used to integrate, send, and receive informationMembrane potential changes are produced by:Changes in membrane permeability to ionsAlterations of ion concentrations across the membrane

Membrane Potential Signals

*

Depolarization

Initially, this is a local electrical event called end plate potentialLater, it ignites an action potential that spreads in all directions across the sarcolemmaThreshold critical level of stimulus

*

Action Potential

A transient depolarization event that includes polarity reversal of a sarcolemma (or nerve cell membrane) and the propagation of an action potential along the membrane

*

Application of voltage causes a patch of the sarcolemma to become permeable to Na+ (sodium channels open)Na+ enters the cell, and the resting potential is decreased (depolarization occurs)If the stimulus is strong enough, an action potential is initiated

Depolarization and Generation of the Action Potential

*

Polarity reversal of the initial patch of sarcolemma changes the permeability of the adjacent patchVoltage-regulated Na+ channels now open in the adjacent patch causing it to depolarizeThus, the action potential travels rapidly along the sarcolemmaOnce initiated, the action potential is unstoppable, and ultimately results in the contraction of a muscle

Propagation of the Action Potential

*

Repolarization Restores the resting electrical conditions of the neuronDoes not restore the resting ionic conditionsIonic redistribution back to resting conditions is restored by the sodium-potassium pump

Role of the Sodium-Potassium Pump

*

Repolarization

Immediately after the depolarization wave passes, the sarcolemma permeability changesNa+ channels close and K+ channels openK+ diffuses from the cell, restoring the electrical polarity of the sarcolemmaRepolarization occurs in the same direction as depolarization, and must occur before the muscle can be stimulated again The ionic concentration of the resting state is restored by the
Na+-K+ pump

*

Hyperpolarization

Occurs when membrane potential increasesInside of membrane becomes more negative

*

Phases of the Action Potential

1 resting state2 depolarization phase3 repolarization phase4-- hyperpolarization

*

Time from the opening of the Na+ activation gates until the closing of inactivation gates The absolute refractory period:Prevents the neuron from generating an action potentialEnsures that each action potential is separateEnforces one-way transmission of nerve impulses

Absolute Refractory Period

*

The interval following the absolute refractory period when:Sodium gates are closedPotassium gates are openRepolarization is occurring

Relative Refractory Period

Action Potential

Membrane potential propagation

Action Potential 1 msRepolarisation 150 to 300msMuscle twitch 10 ms after repolarisation

Graded potentials

*

*

Graded Potentials

*

Graded Potential Action Potential

Short-lived, local changes in membrane potentialDecrease in intensity with distanceTheir magnitude varies directly with the strength of the stimulusSufficiently strong graded potentials can initiate action potentialsAction potentials are only generated by muscle cells and neuronsThey do not decrease in strength over distanceThey are the principal means of neural communicationAn action potential in the axon of a neuron is a nerve impulse

*

What if ..?

The amount of extracellular K+ were below normal?

Opening of the voltage-gated sodium channels were prevented?

*

Extracellular K+ were below normal?

Stronger tendency of K+ to diffuse out Therefore more difficult to reach threshold and action potentialSigns and symptoms = muscle weakness, sluggish reflexes,

*

Extracellular Na were below normal

.

Some of the Na channels which are normally closed will remain open Easier to reach threshold and action potentialSigns and Symptoms nervousness, muscle spasms tetany.

Bio-potential Electrodes

*