True/False Questions

When we lift a weight using the bicep muscles, the force generated by the muscle Fm is smaller than the weight of the object W. (Ch. 7)

False - Fm is actually larger than the weight of the object W.

The Nernst potentials for different ions have different magnitudes but all have the same polarity (or sign). (Ch. 15)

False - Nernst potentials can be either positive or negative.

Ohm's Law only holds for electric current flow in conducting wires. (Ch. 8)

False - Ohm's Law holds for resistors in circuits, resistive conductors and wires, and for the flow of electrolytes through solution. It can even describe the electrical behavior of the cell wall where the current is carried by ions.

P1 will eventually reach P2 after approaching it exponentially. (Ch. 6)

False - P1 never reaches the true value of P2; in about 5 time constants, it has gone 99.3% of the way, so this is often a practical value for specifying the total length of time for the change.

Contraction occurs because the fibers within muscle cells slide over each other and generate force. (Ch. 7)

True - a large number of the sarcomere units act together over the length and cross section of the muscle bundle, so a large force is produced along the axis of the muscle.

We described analogies between mechanical and electrical quantities in the body and described 4 different types of sources in both electrical and mechanical terms. In this context, the mammalian heart is more analogous to an ideal current source than an ideal voltage source. (Ch. 9)

True - blood flows through the body like current so the heart is more like a current source; it also follows conservation of volume (like current cannot disappear/be lost).

During systole, left ventricle compliance is low and during diastole, left ventricle compliance is high. (Ch. 5)

True - during systole, when the heart is contracting, the compliance has to be low (high stiffness), and when the heart is filling up during diastole, the compliance can be high (low stiffness) to intake more blood.

There can be discontinuous jumps in the curve for volume vs. time as long as the flow rate Q stays continuous. (Ch. 6)

False - a discontinuous jump in volume vs. time would mean the flow rate Q was infinite, which is impossible in practice.

An independent current source is one that whose voltage across its terminals is always the same regardless of the load. (Ch. 9)

False - an independent current source is one whose current is always the same regardless of the voltage across its terminals.

In a compliant vessel, any change in the input flow will result in an immediate change in the output flow. (Ch. 4)

False - any change in the input flow could go to filling up the vessel volume and not to flowing out of the vessel.

If more fluid enters a vessel than leaves during a set time t, the sign of Qnet is negative. (Ch. 4)

False - because Qnet = Qi - Qo, the sign of Qnet would be positive (Qnet is input - output, which is opposite what I think it should be).

The bit depth of a digital sampling system is what determines the largest amplitude we can capture, i.e., more bit depth means noticeably louder sound output from our speakers. (Ch. 14)

False - bit depth determines the number of discrete amplitude levels so that more bit depth leads to a more accurate reconstruction of the signal and has nothing directly to do with maximum amplitude.

All tissues in the body have elasticity except for bone, which has no elasticity. (Ch. 4)

False - bone still has to have elasticity because it has to be able to absorb shock and distribute stress.

Shapes and sizes of cells in the human body are all similar throughout the body. (Ch. 2)

False - cells vary widely from very small to very large; cell shape can be anywhere from perfectly circular to threadlike, long projections.

Cutoff filters will only allow a particle larger than the "effective" pore size of the filter if the pressure applied is great enough. (Ch. 2)

False - cutoff filters will not let these particles through regardless of the pressure.

Bioelectric fields can only be measured from the surface of the body. (Ch. 10)

False - electrodes can be placed on catheters and placed directly on tissue of the heart or any other tissue of interest.

Electrons flow in the same direction as the flow of positive current. (Ch. 8)

False - electrons flow in the opposite direction to the flow of positive current because electrons have negative charge.

According to Darcy's Law, an ideal membrane is one in which the flow rate is constant across all values of pressure. (Ch. 2)

False - ideal membranes provide a constant slope in a diagram of flow and pressure, so resistance to flow is constant. But more pressure will still cause more flow, i.e., flow is not constant with pressure.

The Frank-Starling mechanism explains how increased filling volume of the heart leads to decreased stroke volume. (Ch. 5)

False - it leads to increased stroke volume, not decreased because the heart will pump out all of the blood that is returned to it within the limits of the heart.

Laminar flow is characterized by a "slip" condition at the walls, so the fluid velocity is small where the fluid touches the walls and largest in the middle of the tube. (Ch. 3)

False - laminar flow is a "no-slip" condition, so the fluid velocity as fluid touches the walls is 0. Velocity still builds in a parabolic manner to a peak value at the center.

Almost all tissues in the body (e.g. bone, cartilage, skin, vessel walls) exhibit linear stiffness characteristics. (Ch. 4)

False - most tissues in the body have non-linear stiffness because they initially are pliable, stiffen up for moderate force, and then get pliable again before fracture. This is so these tissues can absorb shock and distribute stress properly.

Kinetic energy always involves motion or velocity of an object and potential energy always involves the height of an object. (Ch. 7)

False - potential energy doesn't have to involve the height of an object; think of spring potential energy or chemical potential energy.

The volume of water that leaks out of vessels depends upon how much less the hydrostatic pressure is than the osmotic pressure opposing it. (Ch. 2)

False - the amount that leaks out depends on how much greater the hydrostatic pressure is than the osmotic pressure.

The only means of control from the brain to the heart is the direct connection by means of the autonomic nervous system. (Ch. 7)

False - the brain can also reach the heart through the endocrine system and the hypothalamus.

In a parallel-plate capacitor, charge crosses the distance between the plates and reaches the other side. (Ch. 11)

False - the charge builds up on one side of the capacitor, and electrical repulsion pushes charge out the other side of the capacitor.

When compliant vessels recoil, they require active contraction of vessel walls. (Ch. 5)

False - the contraction occurs when compliant vessels are becoming tighter (lower compliance), and when they recoil, no active contraction is required because they are simply returning to their natural state.

Levers in the musculoskeletal system in the body act to use the contractions of the muscles, which are not very powerful but have a large range, to move and lift heavy objects. (Ch. 7)

False - the contractions of the muscles have a small range but are very powerful (it only takes a small amount of muscle shortening to move an object a large amount).

The driver allows the transport to occur, while the enabler encourages the transport to occur. (Ch. 3)

False - the enabler is what allows the transport to occur, while the driver encourages the transport to occur.

The following are the only assumptions under Poiseuille's Law: - the length of the tube must be much greater than the radius - the tube must be rigid - the flow must be steady in time and laminar in velocity profile (Ch. 3)

False - the fluid must also be Newtonian, or Poiseuille's Law will not apply.

The cell membrane is selectively permeable (semipermeable), and which molecules allowed through depend only on their size. (Ch. 2)

False - the membrane is specific to the size, shape and electrical charge of the molecule.

The equivalent circuit for the membrane of a typical neuronal cell contains only resistors and Nernst voltage sources. (Ch. 15)

False - the membrane voltage (capacitor) is also included, as well as a ground.

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 between the fulcrum and the end of the lever. (Ch. 7)

False - the moment of the weight of the lever is equivalent to positioning the full weight at a point along the lever located half way along the length of the lever.

As fluid flows through a membrane, the pressure drops exponentially to a lower pressure on the other side of the membrane. (Ch. 2)

False - the pressure drops linearly across the membrane.

To reconstruct a sawtooth wave, one only needs to include the odd harmonics (1st, 3rd, 5th, etc.). (Ch. 14)

False - the sawtooth needs all harmonics, while the square and triangle waves need only odd harmonics.

A sine wave will have larger amplitude harmonics than a square wave. (Ch. 14)

False - the square wave will have larger amplitude harmonics because the "sharper" the features of the signal, the larger the amplitudes An of the higher harmonics making up the waveform.

Arteries and arterioles are the most compliant of all the vessels, being thin-walled and very flexible. (Ch. 4)

False - the veins and venules are the most compliant, and they therefore store a good deal of the total blood volume (about 65%).

The Nyquist criterion requires that the sampling interval t should be small enough that there is at least one sample per period T of the highest frequency component. (Ch. 14)

False - there must be at least two samples per period of the highest frequency component.

The arrows in a fluid schematic always represent the direction of flow. (Ch. 5)

False - these arrows are arbitrary, and if a flow value is negative for that arrow, that means the flow is going opposite the direction of that arrow.

The positive and negative signs on the inputs to an operational amplifier indicate the polarity of voltages applied. (Ch. 10)

False - they have nothing to do with the actual polarity of the input voltages; they denote the inverting and non-inverting nature of the two inputs.

It is often easy to find an analytic solution to a differential equation which describes a realistic problem. (Ch. 6)

False - this is unusual, so we use the numerical solution Euler's method.

The amount of blood in the venous vessels is regulated by the compliance of these vessels, which is controlled only by the circulatory system. (Ch. 4)

False - this mechanism is under partial control by the nervous system; this allows the brain to contribute to how much blood is distributed where and what the blood pressure is.

When rearranging circuits, resistors can be moved past nodes. (Ch. 12)

False - this would rearrange the resistors and could change which ones are in series/parallel with one another.

Typical water filters will filter out both viruses and bacteria so the water is safe to drink. (Ch. 2)

False - viruses and proteins are typically very small molecules and it is impractical to make a water filter for them; alternative treatment methods such as iodine or boiling the water are typically used.

It is easy to correctly derive Poiseuille's Law based on just the driver term, cross-sectionally area, length of the tube, and viscosity of the liquid. (Ch. 3)

False - we have to take laminar flow characteristics into account as well.

The Nernst potential is the voltage Vm across the membrane. (Ch. 15)

False - when there are two or more ion species for which the membrane is permeable, the two voltages are different.

Work is the product of the force applied to a body and its motion perpendicular to the direction of the force. (Ch. 7)

False - work is the product of force F applied to a body and the distance d the body is moved in the direction of the force.

To find the Thevenin voltage, you make the circuit an open circuit. (Ch. 13)

False - you make the circuit a short circuit.

Bone, some biopolymers and biomaterials (such as metal and ceramic orthopedic implants) are approximately Hookean over a wide range of applied stress. (Ch. 4)

True - each material has a specific Young's Modulus (or stiffness) that is found from the slope of the linear portion of the stress-strain plot.

An electric circuit is composed of a source and one or more elements connected together by metallic wires and leads (usually copper, but sometimes gold, silver or aluminum) to form a closed path.

True - elements can include resistors, capacitors, diodes, etc.

Viscosity is a measure of the resistance of the layers of the fluid to flowing past one another - like "sliding friction". (Ch. 3)

True - for example, water has a small viscosity compared to molasses, which has a large viscosity.

The voltage across a capacitor cannot jump instantaneously. (Ch. 13)

True - for the voltage to jump instantaneously, the current would have to be infinite, which is impossible.

The bicycle is the most energy-efficient mode of transportation but its efficiency diminishes with speed. (Ch. 7)

True - higher speeds will cause a greater effect by friction and air resistance.

Ion channels are at least partially selective to passing a specific ion type, selecting, for example, by size and/or by charge. (Ch. 15)

True - ion channels can't just allow everything in and sometimes a specific channel will only transport one ion.

The area inside a PV loop is the work done per cycle, while the stroke volume is the width of the PV loop. (Ch. 5)

True - remember the loop progresses counterclockwise from the start of systole (lower-right corner) through the completion of systole and diastole before returning back to start the next cycle.

'Resistivity' is a property of a material while 'Resistance' is specific to an object or a piece of material. (Ch. 8)

True - resistivity is not specific to the particular geometry or size of the device, while the resistance is specific to the size.

An ideal operational amplifier has infinite input resistance. (Ch. 10)

True - the Ri is typically very large (several hundreds of megaohms) so we approximate it as infinite resistance. Keep in mind the output resistance Ro is approximated as 0.

After a long time has elapsed between changes in the source voltage, a capacitor acts like a break in the circuit. (Ch. 13)

True - the capacitor will act like an open circuit because it will be fully charged and no longer accept any more charge.

For any linear electrical source, no matter how complex, there exist ways to transform it, or to find an equivalent circuit, without changing its effect on the remainder of the circuit. (Ch. 13)

True - the equivalent voltage and equivalent resistance will create an equivalent circuit to the original circuit.

Some fluids exhibit a viscosity that varies with flow rate, known as non-Newtonian fluids. (Ch. 3)

True - the graph of shear rate (x-axis) vs. shear stress (y-axis) will show a line beginning linearly with a slight curve, unlike a Newtonian graph which shows a linear relationship.

The plasma membrane is composed of two layers of phospholipid molecules facing each other, with the heads facing out and the tails facing in. (Ch. 2)

True - the heads are hydrophilic so they can face the fluid in the inside and outside of the cell, while the hydrophobic tails face inward so they are protected.

The higher a membrane's resistance is, the lower the flow rate is for a given pressure difference. (Ch. 2)

True - the higher resistance will cause the flow rate to go down if we're keeping pressure constant.

An example of a nonideal material for Darcy's Law would be saline solution through cartilage in the knee. (Ch. 2)

True - the material is deformable, so as the pressure increases, the material compresses, closing off some fluid microchannels. The permeability constant k then decreases, increasing the resistance to flow.

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. (Ch. 7)

True - the moment only includes the normal force (perpendicular) to the lever's axis and the distance d between the fulcrum and the point of action of the force.

Whole blood is comprised only of blood plasma and red blood cells. (Ch. 3)

True - the percentage of the red blood cells is the hematocrit and is typically about 40-45%, higher in males than in females.

The pressure in V = Vo + CP is the transmural pressure (the difference between the pressures inside and outside of the vessel). (Ch. 4)

True - the pressure outside is usually constant and is often considered zero as the reference pressure.

Euler's method is based upon relating successive time samples of V to each other; at each sample point with index i, the value of the next sample point can be obtained from the present value. (Ch. 6)

True - the solution for V is obtained by stepping through the equations in time, with time increasing by a specific interval each time.

We characterize the "size" of biological particles or molecules by their mass in terms of molecular weight (MW). (Ch. 2)

True - the unit is Dalton (Da) and one proton and one neutron have essentially the same weight (the size of one Dalton).

For resistors connected in parallel, the voltages across each resistor are equal. (Ch. 12)

True - the voltage drop should be the same at the beginning of a branch as at the end, and parallel resistors begin at the same branch.

When measuring bioelectric voltages (e.g. EKG or ECG) with an amplifier, one often adds a voltage follower op-amp circuit in series with the electrode resistance in order to increase the input resistance and improve measurement accuracy. (Ch. 10)

True - the voltage follower helps to create an output voltage that is independent of the skin/electrode resistance. This creates a more accurate voltage measurement at the surface.

A windkessel element is a blood vessel possessing both distributed resistance and compliance properties. (Ch. 5)

True - these can have nonlinear properties and the values can vary to represent the changing properties of the vessel along its length.

The Nernst potential is when the drift current and the diffusion current cancel each other out so the net current is 0 and the cell is in equilibrium with respect to that ion. (Ch. 15)

True - these two currents oppose each other and each Nernst potential will be different for each ion.

At one time constant after t = 0, the voltage has gone 63% of its way to its final value. (Ch. 13)

True - this is because e^1 is approximately 0.63, so the voltage has gone 63% of the way.

Most larger (more than a few centimeters) organisms have closed circulatory systems that require pressure to move an oxygen-carrying fluid, but their hearts may differ, for example, some have only one-sided hearts while others have two-sided hearts (left and right). (Ch. 3)

True - this is because some animals don't need as much oxygenated blood pumped through their body as frequent as humans do (like the fish heart).

Cells that line the blood capillaries in the glomerulus of the kidney allow water to pass more easily than the cells in the capillaries of the brain. (Ch. 2)

True - this is because the kidney epithelia cells are designed to intake water, while the cells in the brain don't need to!

Darcy's Law is mathematically linear but may be nonlinear in practice. (Ch. 2)

True - this is because there are deformable materials (nonideal materials) found in the human body that demonstrate nonlinear characteristics in a pressure vs. flow rate graph.

Pulsating blood pressure, noticeable in the aorta and major arteries, is damped by the compliance of the arteries, arterioles, and capillaries in conjunction with their resistance, so by the time blood reaches the capillaries, the pressure waveform is almost flat. (Ch. 4)

True - this is so the thin walls of the capillaries don't have to deal with such high blood pressure.

The larger the resistance and/or compliance, the slower the fluid system will respond to changes and the less faithfully it will follow rapid variations in pressure, volume, or flow. (Ch. 6)

True - this is why the pulsatile pressure waveform of the blood entering the aorta is damped by the time it reaches the high-compliance venous side of the circulation.

When we refer to transmembrane potential, we take the outside of the cell (or membrane) as reference. (Ch. 15)

True - this makes it easier to compare; a negative Vm means that the inside voltage is lower than the outside voltage.

Time is not directly visible in the PV loop. (Ch. 7)

True - time is not either of the axes, and we can gather a lot more from a PV loop besides the time it takes.

Any arbitrary and repetitive waveform (e.g., a pulse, a square wave, or a musical tone) can be written as a combination of sine waves at discrete frequencies that are multiples of a fundamental frequency. (Ch. 14)

True - we do this by performing a Fourier transform and breaking down the waveform.