BME Exam 2

The output voltage is generated by a dependent voltage source in the shape of a diamond. Its voltage is... and it is connected to the output terminal through a... There is also an input resistance that is...

- A(Vp-Vn) (A is very large) - small series output resistor, Ro, which can be approximated as zero resistance - very large, can be approximated as infinite resistance or an open circuit

Which of these items are true about the Pressure-Volume (PV) loop for the heart.

- The area of the PV loop is a measure of work performed by the heart. - The width of the loop is a measure of the stroke volume of each chamber of the heart. - Time is not directly visible in the PV loop. - The PV Loop can be constructed from the Wigger's Diagram, the diagram that shows pressure and volume of the heart as functions of time - the bigger the loop area, the more energy is used

Ohm's law represents a ... relationship between current and voltage

- linear (V=IR). - States that the voltage drop across a resistive element is proportional to the electrical current, with the proportionality constant given by the resistance R. - If R increases: the current will decrease, the voltage will increase, and the pressure drop across the tube goes up

the ideal op amp model

- no current can flow into these input terminals because they are terminated in open circuits - output voltage is the same as the dependent source voltage since Ro=0 - Vp=Vn

succession of pv-loops

- starts with left ventricle overfilled compared to normal, goes through cycles until normal volume is reached - line that marks the left edge has a slope of 1/Chs

non inverting amplifier

- used when it is desired that the output voltage have the same polarity as the input voltage - signal voltage source is connected to the non-inverting input - input and output voltages have the same sign

inverting amplifier

- used when it is desired to amplify and invert an input signal so that the output voltage is larger than the input but of opposite polarity. - output voltage of the amplifier is equal to the input voltage multiplied by the ratio of Rf and Rs - negative sign in the equation means that the polarity of the output is inverted from that of the input, hence the name

Steps to find FM and FJ

1. Draw a free body diagram and include, - Wc: applied weight - WL: lever weight - Fm: muscle force - Fj: joint force - axis - correct moment-arm lengths 2. balance the moments, find moments and set equal to zero (Fj not inlcuded) 3. find the joint reaction force

1. Vp 2.Vn 3. Vo

1. input voltage to non-inverting terminal 2. input voltage to inverting terminal 3. output voltage

In an inverting amplifier 1. Rs 2. Rf

1. resistor connecting the source to the op amp 2. feedback resistor, connecting the output back to the inverting input, always must be connected back to the inverting input

1. Kirchhoff's Voltage Law 2. Kirchhoff's Current Law

1. the algebraic sum of voltages around any closed path (loop) is zero 2. the sum of currents at any node is zero

1. A diode is... 2. In an ideal diode...

1. used as a one-way 'valve' of current, and is highly resistant to flow in the opposite direction 2. it is assumed that in the forward direction, the diode possesses zero resistance, but in the reverse direction it acts like an open circuit with infinite resistance

Kirchhoffs Tour Rules

1. when using KVL around a loop, the sign of the voltage contribution across any element is the sign first encountered in the direction of the tour 2. Each independent loop must include at least one new branch not included in any other loop 3. For n nodes, KCL gives (n-1) independent equations

How many equations is the minimum number needed to solve a set of linear questions for 3 unknown variables?

3

When we lift a weight using the bicep muscles, how does the force generated by the muscle, FM, compare to the weight of the object, W?

FM > W

Bioelectric fields can only be measured from the surface of the body.

False

The function of a diode, like a resistor, does not depend on which way we attach it in a circuit.

False

The only means of control from the brain to the heart is the direct connection by means of the autonomic nervous system.

False

Work is the product of the force applied to a body and its motion perpendicular to the direction of the force.

False

For a voltage divider to function, there must also be an amplifier in the circuit.

False, A voltage divider consists of two resistors (or resistances) and does not need an amplifier. It is a `passive' circuit.

the positive and negative signs on the inputs to an operational amplifier indicate the polarity of voltages applied.

False, the signs inside the symbol denote inverting and non-inverting. However, the signs of power supply voltage leads (V+ and V-) do denote polarity.

moment, M is the product of the component... and the...

Fn, the normal force (perpendicular), distance between the fulcrum and the point of action of the force

The moment that a uniform lever produces around a fulcrum is equivalent to positioning the full weight, WL, at a point along the lever located:

Half way along the length of the lever.

What sort of amplifier is this op-amp circuit?

Inverting amplifier

An ideal operational amplifier has infinite input resistance.

True

Contraction occurs because the fibers within muscle cells slide over each other and generate force.

True

The bicycle is the most energy-efficient mode of transportation but its efficiency diminishes with speed.

True

When computing rotational moments about a lever, we have to include only the components of the forces that apply perpendicular (normal) to the axis of the lever.

True

`Resistivity' is a property of a material while `Resistance' is specific to an object or a piece of material.

True

P depends on

V and C

Class one lever, neck joint

W and F are on opposite sides of the fulcrum but in the same direction

Class three lever, bicep

W and F are on the same side of the fulcrum and W is further from the fulcrum than the pull F

Class two lever

W and F are on the same side of the fulcrum but in opposing directions, with F acting at some point further from the fulcrum

voltage divider circuit occurs whenever

a source voltage is applied to a string of resistors in series, and the measured voltage is taken across one of these resistors.

node

any point at which two or more circuit elements join, more than two = essential node

the inverse of resistance/resistivity is

conductance/conductivity

the curve for volume (and pressure) versus time must be

continuous, there can be no discontinuous jumps at any time

work is a

convenient way of measuring the transfer of energy from one form to another

time constant

determines how fast the flow variables in this system can change from one value to another

at a junction, flow rate in =

flow rate out

systolic phase

forceful contraction and ejection

levers pivot around or rotate around if unbalanced the

fulcrum

If V across a resistor is positive, then the voltage on the left is.... than on the right.

greater (if negative then right is greater then left) *sign of v and i are always linked together

the heart wall muscles change from ... compliance to ... compliance

high stiffness to low stiffness

if I is negative, the current actually flows

in the opposite direction of the arrow drawn

when compliance decreases, pressure

increases which causes ejection

initial pressure inside the vessel before and just at time t=0

initial constant pressure, Pi

forces on a lever are

load, W, and pulling force, F

diodes are purposely made to behave in a ... manner

non-ohmic, meaning it doesn't obey ohms law

dependent sources have

outputs that are variable, and are identified by a diamond shape

if lever moves counterclockwise than its moments sign is

positive

eulers method

predicts the future value of a variable based on the present value of the variable, termed forward-difference method

Ps>Pd which is a requirement for

pumping blood into the higher pressure arteries after being collected from the lower pressure veins

diastolic phase

relaxing and filling, must expand easily to accept this volume

pressure and volume are related by

the compliance of the vessel

if there is a continuous branch with multiple elements containing no essential nodes then

the current will be the same throughout the continuous branch

power is defined as

the energy expended per unit of time, there is a power requirement for maintaining the flow

electrostatic

the force produced on a charged particle by the presence of other nearby charged particles.

starlings law of the heart

the heart will pump out all of the blood that is returned to it, within the limits of the heart

location of center of gravity

the moment that the lever produces around the fulcrum is equivalent to positioning the full weight WL of the lever exactly halfway down the lever

Passive sign convention

the positive sign for the voltage reference is put on the side of the resistor where the positive current enters

resistivity

the resistive properties of a small incremental volume, specific to the material (units of ohm-meter)

isovolumic contraction: left ventricle the ventricular volume at the start of systole is... but the force exerted on this blood by the walls ... marking the beginning of systole

the same as at the end of diastole, sharply rises

independent sources are identified by

the shape of a circle or by a battery symbol

The larger the time constant

the slower P1 will change

the larger the resistance and/or compliance

the slower the fluid system will respond to changes

dual input or differential amplifier

two inputs (inverting and non-inverting) and one output. Output power is often much larger than the input power

independent voltage source/(independent current source)

voltage (current) is always the same regardless of the current (voltage) through the source

a stationary lever has a moment sum of

zero

the net moment around the joint must be

zero