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14.4 Control Systems
During a heart attack and cardiac surgery,ibrillations can occur.
Large currents can be used to align the heart.
The device has a 6000 V charge and 200 J of energy.
There are two wires on the chest.
TheCapacitor discharges through the body when the switch is closed.
The heart can resume its normal beat after a pulse.
The heart needs to be shocked a few times.
Electric current can be used to strengthen muscles.
The electric stimulation of paralyzed muscles is necessary to maintain their tone.
In a similar way, the heart muscles can be triggered.
In some heart diseases, the cells that control the timing of the heartbeat cease to function properly, and electronic pacemakers have been very useful.
The electronic pacemaker is a pulse generator that can be used to start and stop the heartbeat.
The device is small enough for surgery.
The battery that powers the pacemaker needs to be replaced every few years.
Many of the processes in living systems have to be controlled.
Some examples of controlled processes have already been encountered.
The growth of bones and temperature control in the body were two cases where various processes had to be regulated.
The general method of analyzing control systems will be described in this section.
The control system has an identifiable function.
The parameters to be controlled.
This may be the temperature of the skin, the movement of muscles, the rate of heart beat, the size of the bone, and so on.
It is possible to transmit information about the parameters state to a decision-making center.
The task is usually performed by the sensory cortex.
The controlled parameters are required to comply with a reference value.
The reference value is set by the central nervous system.
Many references for body functions are not under the control of the brain.
There is a method for comparing the state of the parameter with the reference value.
The messages are translated into actions that change the parameters.
The contraction of a set of muscle fibers is what happens in the case of the hand position.
As the light intensity increases, the opening size decreases.
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