biocybernetics 2008 assoc. prof. helena baráni, ing. phd. institute of medical biophysics martin
TRANSCRIPT
BIOCYBERNETICS
2008
Assoc. prof. Helena Baráni, Ing. PhD. Institute of Medical Biophysics MARTIN
1. Theory of information- signal information carrier- living organism biological system- information connected by some physical quantity
BIOCYBERNETICS
3. Control - simple control (without feedback)- control with feedback or regulation
2. Information transmission (communication)- information transmitting systems
Biocybernetics plays a major role in systems biology, seeking to integrate different levels of information to understand how biological systems function.
Biocybernetics is the application of cybernetics to the biological science.
Cybernetics has close connections to biology and medicine
Definition by Norbert Wiener:
Cybernetics is the science of communication and control in machines and living organisms.
SIGNAL as an INFORMATION CARRIER
THEORY OF INFORMATION
All of the systems in an organism are interconnected.
The circulatory, respiratory and muscular systems:
The function of circulatory system is to service the needs of body tissues:- to transport oxygen and nutrients to the cells - to transport carbon dioxine and waste products away
Example:
The circulatory system is connected to all of body's cells so that it can transport oxygen efficiently.
The circulatory system – direct connection to the lymphatic system - the involvement in defense of organism against infection
The circulatory system – the carrier of chemical information– the transport of hormones and other physiological substances on the place of their effect.
The muscular system is closely connected to the nervous system. The neurons of nervous system are connected to most of
the cells in the muscular system.
In the same way that all of a cells need oxygen transported by the circulatory system, all of a tissues and organs require instruction and direction from the nervous system.
There is interaction between the muscles and nervous system.
That interaction helps the organism interacts with the environment.
The other direction of the interaction is connected with the fact that the life functions are accompanied by various phenomena. These phenomena can be observed and recorded as signals which supply information and may be processed by the environment.
In one direction of this interaction the organism perceives signals arriving from the external world and processes the information content of these signals.
INTERACTION
The organism continually interacts with the surroundings and with other systems.
- Information is associated with a signal. - Information is always carried by some physical quantity, usually it is signal.
BIOLOGICAL SIGNALS
The signal, or information, may refer to the state of the system, to some process, etc.
parameter of status - e.g. body temperature. - the signal associated with this is continuous, and its
magnitude is approximately constant - the blood sugar concentration is an important indicator
of the metabolism
Definition:A quantity of matter, resp. change of quantity, carrying or storing information is called a signal.
periodic processes - the ECG signal associated with the heart function.
Biological signals
Biological systems - open dynamical systems, which are enable to generate, receive, process and emit informations
Input informations – reflect to the health conditions
•Biological signals are generated in life organism
- created by vital manifestation of organism or by stimulus from external space, which may affect vital manifestation
- velocity changes are characterized by large variability
are all signals that are produced by organs within a body.
• Mediated biological signals
- originate by interaction of organism i.a. with rtg radiation, ultraviolet wave or with the magnetic field. diagnostic application
Biological signals are a manifestation of activities of very complex biological systems, representing real living object.These signals are generated directly by this object. Biological signals are caused by mechanical, chemical or electrical activities.
- ELECTRICAL SIGNALS are either the local electrical changes or the generalized electrical changes, represented by action potential.Action potentials are the sources of biological signals. They are generated by membranes or muscle fibers.
Living body represents a kind of a spatial conductor. The spreading of APs through such conductor creates the electric field. Scanning electrical signals with different frequency and intensity can be processed and analyzed by various methods to obtain informations about living systems or clinical applications.
ECG, EEG, EMG, ENG
- NON-ELECTRICAL SIGNALS have to be transformed into electrical signals
- e.g. blood pressure, respiratory pressures, volumes, flows, body temperature
BIOLOGICAL SIGNALS
a) Measurement of respiratory pressures Measurement of blood pressure (Direct method) - electromanometers equipped with pressure transducers working on one of those three principles: tensometric, capacitive, inductive.
b) Measurement of blood flow by an electromagnetic flowmeter or by the ultrasound detectors.
c) Measurement of air flow by pneumotochograph
d) Measurement of air volumes by spirometers
e) Measurement of body temperature by thermometer
FOR RECORDING OF ELECTRICAL SIGNALS we need:
• Electrodes • Amplifier with Filter • Oscilloscope • Chart Recorder or
Computer (with AD Converter)
FOR RECORDING OF NON-ELECTRIC SIGNALS we need: • Transducer• Amplifier• Chart Recorder or • Computer (with AD Converter)
BIOLOGICAL SIGNALS
1. ELECTRODES - metals, glass - filled with salt solutions
Macroelectrodes - for a skin recording of ECG, EEG. The electrodes have to be moistured before using by a jell or salt solution in order to decrease the input resistance, and then firmly attached to the body.
For ENG or EMG recording we can use a variety of metal electrodes with different shape and size (plate electrodes, needle electrodes etc.)
Low impedance electrode
Microelectrodes - for intracellular or extracellular recording from the neurons. Microelectrodes for extracellular recording filled in with a high
concentration of NaCl solution (electrolyte)
Microelectrodes for intracellular recording filled in with the high concentration of K solution.
•Bipolar leads - scan potential difference between scan potential difference between two places (two places (two active electrodes) a biphasic potential is obtained.
Bipolar limb leads I. II. III.Bipolar chest leads Bipolar chest leads CR, CL, CFCR, CL, CF
•Unipolar leads - scan potential difference scan potential difference between between one active electrode and an indifferent one (the Wilson’s clipthe Wilson’s clip with a zero potential) the monophasic potential is obtained.
Unipolar limb leads VR, VL, VFVR, VL, VF Unipolar augmented limb leads aVR, aVL, aVFUnipolar chest leadsUnipolar chest leads V1 – V6V1 – V6
BIOLOGICAL SIGNALS
Recordings:
B. MULTIUNIT ACTIVITY = MULTIPOTENTIAL - results from mixing a variety of APs. e.g. from the nerve or muscle tissue
A. SINGLE FIBRE NERVE ACTIVITY
or UNIT NEURONAL ACTIVITY - recording from the one nerve fibre or one neuronal cell
BIOLOGICAL SIGNALS
2. FILTRATION - removes the unwanted components of electrical signals obtained during recording,
e.g. using RC filters - one can remove 50 Hz of AC current, that superimposed on the taken body electrical signals.
3. AMPLIFIER - increases a low input signal into the higher output signal.
In medical practice the differential amplifiers are commonly used - they consist of two amplifiers with common output clamp. Both amplifiers have the same degree of amplification but one of them serves as inverting.
Basic parameters: discriminating factor of the amplifier input (output) specifications, gain, width of transmission (frequency) band
BIOLOGICAL SIGNALS
Signal Name Amplitude(mV)
Frequency range (Hz)
ECG Electrocardiogram 0.5 - 5.0 0.01 - 250
EEG Electroencefalogram 0.01 - 50.0 0.1 - 100
EMG Electromyogram(surface electrode)
0.1 - 10.0 0.01 - 10000
EMG Electromyogram(needle electrode)
0.05 - 5 0.01 - 10000
ENG Electroneurogram 0.05 – 10.0 0.01 - 1000
4. OSCILLOSCOPE
- displays the recorded
electrical signals.
BIOLOGICAL SIGNALS
5. CHART RECORDERS or COMPUTERS record the curve of signals or store the parameters of signal within the memory, on-line or of-line recording digital transform – analog signal is transformed into
digital form by AD Converter sampled signal subsequent processing and evaluation of signals.
BIOLOGICAL SIGNALS
BIOLOGICAL SIGNALS - EVALUATION
Amplitude Amplitude of particular waves and oscillations:of particular waves and oscillations:
P = 1 to 3 mm, R = 7 to 15 mm, T = 3 to 5 mm, Q and S = -3 to -5 mmP = 1 to 3 mm, R = 7 to 15 mm, T = 3 to 5 mm, Q and S = -3 to -5 mm
Wave PWave P – depolarization of – depolarization of atrium (0.09s – 0.11) satrium (0.09s – 0.11) s
Interval PQInterval PQ – time necessary – time necessary for transmission of irritation for transmission of irritation from the atrium to the from the atrium to the ventricles 0.12 s – 0.2 sventricles 0.12 s – 0.2 s
Complex QRSComplex QRS – depolarization – depolarization of ventriclesof ventricles
Wave TWave T - - depolarizationdepolarization of of ventricleventricle
BIOLOGICAL SIGNALS can be processed and analyzed by computer analysis with large number of methods:
Mapping of frequenciesThe computer displays model of the human head and positioning of the electrodes. The different frequencies are displayed with different colors in relation to time.
is basis for establishing of diagnosis. Frequency characteristic determines which frequencies are included in a signal.
Frequency characteristics
Spectral analysisprovides more transparent insight in spectrum of signal frequencies in relation to time. The magnitude of amplitude expresses corresponding color depth according to the chosen scale.
Dominant frequency is 10Hz during 7 seconds of measurement, and amplitude is 32 mV.
Technical communication or information - transmitting systems include the telegraph, radio and television while
biological examples are the processes of seeing, hearing, etc.
The information arrives from the information source to the transmitter unit, the transmitter unit transforms the information into signals and transmits the signals carring information.
The signals are transmitted to the receiver through a channel.
Every system which transmits information serves as a channel.
Signals from the environment may also reach the channel.
Signals may comprise noise, which may distort the original meaning of the information.
Transmitter Receiver
Information transmission
- For transmitting of correct signal we have to use coded signal.- The assignment of an unequivocal signal series to the
information is called coding.
Examples of code: Morse code, Brialle script
The code is the rule relating to the assignment, which allows the reconstruction of the information from the signals.
Information transmission
PRIMARY SENSORY CODING The sensory pathways provide information on stimulus type, intensity, and location.
This information has to be coded in the language of action potentials conveyed over the nerve pathways.
Action potentials are coded by frequency not by amplitude.
The sensory systems code of stimulus intensity example:
A record of an experiment in which increased stimulus intensity is reflected in an increased action potential frequency in a single afferent nerve fiber.
HEARING - communication system
Information source the sound arriving at the ears.
userInformation
source channel
noise
userTransmitter Receiver
Receiver the hearing cortex
Channel the fibres of the auditory nerve and
the information is carried by action potential signals
Coding
during the movement of Basilar membrane, the mechanical vibration of the hair cells is transformed into a generator potential and the action potential of the fibres of the auditory nerve. Both potentials result in microphone potential.
Transmitter
the hair cells of the organ of Corti
Biophysics of hearing
The information on frequency and intensity of sound stimulus is coded in two ways involving - the position of active auditory nerve fibre- the frequency of action potential signal of a single fibre.
Recording of an action potential of a single auditory nerve fibre
Biological systems are coordinated and controlled.
The concept of control includes two types of processes:
simple control = control without feedback
regulation = control with feedback
CONTROL
The two basic functional elements of a control system (without feedback) are: the controlling unit (control centre) the controlled unit
In the control without feedback no information reaches the controlling unit (centre) from the controlled unit. Output signal does not react upon the control centre.
Examples: the adaptation of living bodies to their environment - the sensation e.g. perception of the warmth
CONTROL
Each type of control is based on the transmission of information.
INFORMATION TRANSMISSION signal
base interference
signal signal
output
REGULATION
Biological systems contain many types of regulatory circuits, with negative and positive feedbacks.
In biological systems most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions.
Regulation should be understood as an action which minimalize difference between real regulated values of quantities and their desired values
REGULATORY CIRCUITS
Outputsignal
Negative feedback is a process that happens when the systems need to slow down or completely stop a physiological process.
NEGATIVE FEEDBACK
Negative feedback helps to maintain stability in a system in spite of external changes. It is related to homeostasis.
Homeostasis - maintenance of nearly constant conditions in the internal environment
Example:- negative feedback occurs when your body temperature begins to rise and this has to be stopped - sweating is a good example of negative feedback, as well as
- regulation of the blood pressure, pH value or
- hormonal regulation of living body.
POSITIVE FEEDBACK
Positive feedback is the opposite of negative feedback in that encourages a physiological process or amplifies the action of a system.
Example:
- most positive feedbacks provide for fast autoexcitation of elements of endocrine and nervous systems (in particular, in stress responses conditions)
- and play a key role in regulation of growth, and development of organs.
Positive feedback is a cyclic process that can continue to amplify the body response to a stimulus.
1. The impulses generated by the cells of the SA node are carried across the right atrium, to the left atrium and to the AV node.
2. The electrical signal follows through the Hiss and Purkinje systems.
The movement of electricity causes the atria to contract, thus helps push blood into the ventricles.
The movement of electricity causes the ventricles to contract and thus to push blood
out to the lungs and the rest of the body.
CONTROL OF THE HART RATE EXAMPLE
The quantity of blood pumped by the heart varies each minute by changing its frequency of beating (heart rate) or by volume it ejects per beat.
The cardiac response to peripheral chemoreceptor (PCh) stimulation is result ofprimary and secondary reflex mechanisms.
REGULATION of HEART RATE
The control of heart rate is mediated by the autonomic nervous system.
The secondary influences attenuate the primary reflex effect of PCh stimulation on the heart rate
Normal Regulation of Blood Glucose
•When the blood sugar level rises, the islets of Langerhans in the pancreas release insulin into the blood.
When blood sugar levels are too low, the pancreas stops producing insulin so less glucose is taken up by tissues and liver, and blood sugar levels rise again.
Insulin triggers uptake of sugar into the tissues and muscles, and triggers the liver to turn glucose into glycogen, which is stored. This brings the blood sugar level down.
glucoregulation.swf
