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Question 1

Hats the formula for the induction method of measuring body fluid compartment volumes
What assumption is this formula based on?

Answer 1

Yes, you’re right! The formula for calculating the volume of a compartment using the indicator solution method can also be expressed as:

F=I/C

Where:
• F = Volume of the compartment (e.g., plasma volume, extracellular fluid volume)
• I = The amount of dye or tracer injected into the body (usually in mg or g)
• C = The concentration of the dye in the sample after distribution (usually in mg/L or g/L)

This formula works under the assumption that the dye is evenly distributed in the compartment and that there’s no significant loss of the dye from the compartment.

Let me know if this makes sense now!

•Indicator dilution method
•If an indicator is mixed with blood with a known injection rate, I (mg/minute)
•And the concentration C (mg/liter) is measured after mixing, then the flow F (liters/minute) is given by

Question 2

State three characteristics of market substances
Which marker substance is used for:
Plasma
total body water
ECf

Answer 2

-They should be inert: they shouldn’t mix with substances in the body or undergo reactions in the body, they shouldn’t be metabolized, they shouldn’t be absorbed by the body tissues. Shouldn’t be excreted during the measurement period
-They should be harmless
-They should be measurable

Characteristics of Marker Substances:
1. Inert and non-toxic – It should not interfere with body functions or be harmful.
2. Distributes only in the target compartment – It must stay only in the fluid compartment being measured (e.g., plasma, ECF, TBW).
3. Even and rapid distribution – It should quickly and uniformly mix throughout the compartment.
4. Not metabolized or degraded – It should not be chemically altered by the body.
5. Not reabsorbed or secreted – Especially important for renal markers; no loss through urine or uptake by cells during measurement.
6. Easily measurable – Its concentration should be easily detected in body fluids (e.g., blood, urine).
7. Should not bind to proteins or tissues – To avoid being trapped and altering volume estimation.

•

• Examples:
• Evan’s blue and radioactive iodine for plasma.

Methods of Measurement of Body Fluid Volume
•What should be the characteristics of marker substances?
• Examples:
• Evan’s blue and radioactive iodine for plasma.
• D20, T20 and antipyrine for TBW
• Innulin, mannitol and radioactive sodium for ECF

Excellent question! The markers are chosen based on how they behave in the body—specifically, where they distribute and where they don’t. Here’s why each group of markers is used for its respective fluid compartment:

1. Plasma Volume (PV)

Markers: Evan’s blue, ¹²⁵I-albumin
Why:
• These substances bind to plasma proteins (like albumin).
• Therefore, they remain confined within the blood vessels (intravascular space) and do not enter interstitial or intracellular fluid.
• This makes them perfect for measuring plasma volume.

2. Total Body Water (TBW)

Markers: D₂O (deuterium oxide), T₂O (tritium oxide), antipyrine
Why:
• These substances are small, neutral, and lipophilic, so they can freely cross all cell membranes.
• They distribute throughout both extracellular and intracellular fluids.
• That’s why they reflect total body water.

3. Extracellular Fluid (ECF)

Markers: Inulin, mannitol, ²²Na (radioactive sodium)
Why:
• These substances do not enter cells, so they remain in the extracellular space (i.e., plasma + interstitial fluid).
• They are used to measure the volume outside cells, but they still distribute between blood plasma and interstitial fluid.

In short:
• Stays in blood only → Plasma markers
• Crosses into all water spaces → TBW markers
• Doesn’t enter cells → ECF markers

Let me know if you want a visual summary or diagram for easier memorization!

Question 3

Why don’t we measure ICF and interstitial fluid volume?
Define the following:
Osmolality
Osmolarity
Tonicity
Isosmotic

Answer 3

We don’t measure ICFV because Total body water is made up of ICFV and ECFV so since we can’t measure ICFV directly, we subtract the ECFV from the TBW so we get the ICFV. So TBW-ECfV

So we can’t directly separate the ITFV from the ECF. eCF comprises of plasma, interstitial fluid volume and trans cellular fluid.
So to get ITFV, you subtract the plasma volume from the ECF volume so ECf-PV

Osmolality refers to the concentration o the solute in kilograms of a solution

Osmolarity is the concentration of solute in the volume of a solution

Tonicity is the ability of solute to cause osmosis or cause water to move out of the cell and it depends on the solutes that stay outside the cell. If the solute won’t cause water to go out of the cell, it won’t affect tonicity.

Osmolality vs Osmolarity:
• Osmolality = solute concentration per kilogram of solvent (water) or conc of solute per unit weight(kg) of solvent.
• More accurate inside the body (less affected by temperature/volume changes)
• Osmolarity = solute concentration per liter of solution or conc per unit volume of solution.(mol/litre)
• Easier to calculate in labs

3. Tonicity:
   • Tonicity is the effect of a solution on cell volume. Or the measure of a solutes ability to cause osmosis
   • It depends only on non-permeable solutes (solutes that stay outside the cell).
   • These draw water out, making the cell shrink (hypertonic)
   • Or allow water in, making the cell swell (hypotonic)
   • Or cause no movement, so the cell stays the same (isotonic)

Isosomotic:
So if I understand what you’re saying, isOsmolality is when two solutions have the same concentration or number of particles per kilogram of solvent.

It relates to isotonicity because they have the same isosomolality May or may not cause swelling or shrinking of the cell. That’s why isotonicity is not equal to isosomolality

Yes — you’ve got it exactly right!

Here’s a clearer version of what you just said:
• Isosmolality means two solutions have the same number of solute particles per kilogram of water.
• But just having the same number of particles (isosmolality) doesn’t guarantee the same effect on a cell.
• That’s because tonicity depends on whether those particles can cross the cell membrane or not.

So yes, isosmolality may or may not lead to cell shrinking or swelling, which is why:

Isosmolality ≠ Isotonicity

Great understanding! Want a quick summary table to remember it?

Question 4

Explain ficks principle in relation to cardiac output and explain the principle ORS works on

Answer 4

Great questions!

1. What principle does ORS (Oral Rehydration Solution) work on?

ORS works based on the principle of co-transport of glucose and sodium in the small intestine.

Here’s how it works:
• In the intestine, there’s a special transporter (SGLT-1) that absorbs sodium and glucose together.
• When glucose and sodium are absorbed, water follows due to osmosis.
• This helps rehydrate the body effectively, even during diarrhea when you’re losing water and electrolytes.

So the principle is:

Sodium-glucose co-transport creates an osmotic gradient that pulls water into the body.

That’s why ORS contains both glucose and sodium — without both, it won’t work as well.

2. The Fick’s Principle and the equation

Yes! You’re right. The Fick principle focuses on blood flow (F). The equation usually looks like this:

F= oxygen consumption / arterial oxygen- venous oxygen

Or rate of oxygen consumption/ amount of oxygen leaving - amount of oxygen entering the heart
Where:
• F = Blood flow (Cardiac Output) in L/min
• Oxygen consumption = how much oxygen the body uses per minute (measured in mL/min)
• Arterial O₂ = oxygen content in oxygenated blood
• Venous O₂ = oxygen content in deoxygenated blood

Example:

If the body uses 250 mL of oxygen per minute(Oxygen used is mL/min) and the difference in O₂ content between arteries and veins is 50 mL per liter(diff in oxygen is ml/L) , then: F is litres per min.



That means the heart is pumping 5 liters of blood per minute.

Would you like to go over any part with a diagram or real-life example?

Yes, exactly! That’s another way of expressing Fick’s Principle — and it’s actually at the heart of the equation. Let’s break it down:

Fick’s Principle — Concept Simplified:

“The amount of a substance taken up by an organ (like oxygen by the lungs) is equal to the blood flow to the organ multiplied by the difference between the amount entering and leaving the organ.”

So for oxygen and the heart, we say:



Rearranging it gives the formula you’re seeing:



Meaning of “oxygen entering and leaving”:
• Oxygen entering = the amount of O₂ in arterial blood (from lungs to tissues)
• Oxygen leaving = the amount of O₂ in venous blood (after tissues have used some up)

So:
• If you measure how much O₂ the body uses in 1 min (e.g., 250 mL/min),
• And know how much O₂ is in blood before and after it passes through tissues,
• You can calculate how much blood (cardiac output) must have flowed to deliver that oxygen.

Would you like me to explain this with numbers or in a diagram-style breakdown too?

Great! Here’s a simple analogy followed by a clinical example:

Simple Analogy:

Think of your heart as a delivery truck, and oxygen as the cargo.
• The lungs are the loading station where the truck picks up oxygen.
• The body tissues are the delivery locations where the oxygen is dropped off.

Now, if you want to know how many trucks (how much blood) are moving each minute, you can check:
• How much cargo (oxygen) they pick up at the lungs, and
• How much cargo is left after delivery (how much oxygen is left in the blood returning to the lungs).

This is what Fick’s Principle does — by comparing oxygen before and after it’s delivered, it calculates how many “trucks” (i.e., cardiac output) are moving.

Clinical Example:

Let’s say a doctor wants to know how well a patient’s heart is pumping.
1. They measure how much oxygen is in the arteries (O₂ entering) and how much is in the veins (O₂ leaving).
2. They also measure how much oxygen the body is using per minute (VO₂) — maybe with a breathing mask.
3. Using Fick’s equation:
Cardiac output = oxygen used per minute/ arterial oxygen minus venous oxygen
This tells them how much blood the heart is pumping per minute.

If the result is low, it may mean the heart is weak or the tissues aren’t getting enough oxygen — and this helps the doctor know what treatment to give.

Would you like a quick recap in bullet points for easier memorization?

So basically to assess how well your heart is doing or how much blood it’s pumping per minute , we check the amount of oxygen you’re consuming divided by the amount of oxygen in blood leaving the heart minus the amount entering the heart

Cardiac output is the amount of blood the heart pumps out per minute.

Yes, exactly!
When the heart pumps once — meaning one full contraction (systole) — the amount of blood it pushes out from the left ventricle into the aorta is called the stroke volume.

In short:
Stroke volume = the amount of blood pumped out of the heart with each beat.
HR is the number of times the heart beats per minute.
So CO=SV X HR

Ficks oeinciple can also be expressed as F= dm/dt divided by Ca-Cv(the difference in oxygen content between arterial (Ca) and mixed venous (Cv) blood, according to the equation)
In the context of Fick’s principle of cardiac output, “dm/dt” would likely refer to the rate of change of oxygen (or another marker substance) concentration in blood as it moves through the pulmonary or systemic circulation, which is related to oxygen uptake (V̇O2) and the arterial-venous oxygen content difference.

Question 5

Explain the use of blood flow meter as an application of body fluid measurement in health and disease

Answer 5

Sure! Here’s a simple explanation:

Fistula Creation for Dialysis & Blood Flow Measurement
• In patients with kidney failure, hemodialysis is used to filter their blood.
• For this, a strong and wide vein is needed to allow large needles and good blood flow.
• So, doctors create a fistula — they join an artery to a nearby vein (usually in the arm).
• The high pressure from the artery causes the vein to enlarge and thicken over time so that it can be strong enough for the needle in dialysis
• Blood flow meters are then used to:
• Measure how well blood is flowing through the fistula
• Ensure it’s mature enough for dialysis use
• Detect any blockages or poor flow before complications happen

Let me know if you’d like a quick diagram or summary line to memorize this!

Great questions! Let’s break it down:

Why must they create a fistula for dialysis?
1. Dialysis needs strong blood flow — about 250–400 mL/min.
2. Normal veins are too small and fragile for repeated needle insertion and high blood flow.
3. So, a fistula is created by connecting an artery to a vein.
• The artery’s pressure makes the vein larger and stronger.
• This makes it easier to insert needles and handle the high blood flow needed for dialysis.

How is a blood flow meter an application of body fluid measurement?
1. Blood flow meters measure the rate of blood flow through vessels — this is a form of body fluid (blood) measurement.
2. In the case of a fistula:
• It assesses if the fistula is ready (mature) to be used for dialysis.
• It detects blockages or poor flow, which can prevent effective dialysis.
• It helps guide medical decisions (e.g., whether to redo or repair the fistula).

Summary:
Creating a fistula ensures strong, reliable access to blood for dialysis. Using a blood flow meter is a direct application of body fluid measurement to monitor and maintain this access for effective treatment.

Let me know if you want a quick one-liner to memorize!

Question 6

What carries what
Sodium or glucose?
In the symport

Answer 6

Na⁺/Glucose Symport (SGLT) – Found in intestines/kidneys:
• Sodium (Na⁺) moves down its concentration gradient into the cell.
• It pulls glucose with it into the cell.
• Both go in the same direction → Symport.

Sodium goes down the electrochemical gradient and easily enters the cell because it’s more outside the cell than inside so naturally it’ll want to move inside. And there’s more negative charge inside the cell than outside so sodium which Is positively charged will want to move inside.
So glucose will ride on sodium’s energy or easy ability to enter the cell using a contransporter called the sodium glucose linked transporter so it enters too.

You’re right! Actually, there is more glucose outside the cell than inside, and I made a mistake earlier. Here’s the corrected explanation:

Why does glucose struggle to enter?
• Glucose concentrations are higher outside the cell (in the bloodstream) compared to inside the cell, so it should naturally move into the cell by diffusion.
• However, glucose cannot easily diffuse across the cell membrane because the membrane is lipid-based, and glucose is a polar molecule, which has difficulty passing through.

So how does glucose enter the cell?

It uses facilitated diffusion or active transport mechanisms (like the SGLT co-transporter I mentioned). Here’s the correct flow:
1. Sodium (Na+) is pumped out of the cell by the sodium-potassium pump, creating a high concentration of sodium outside.
2. Glucose then enters the cell through a co-transporter (SGLT), which uses the energy from sodium moving into the cell (down its gradient) to pull glucose into the cell, even though glucose is already in higher concentration outside. This secondary active transport doesn’t directly use ATP but uses the energy from the sodium gradient.

To summarize:
• More glucose is outside the cell.
• Sodium moves into the cell easily (due to its concentration gradient), and in turn, it helps glucose enter via the co-transporter.

Does this clarify things better?

Yes, you’re correct! There are two main mechanisms for glucose to enter cells: facilitated diffusion and symport (secondary active transport). Both involve transport proteins, but they work in different ways:

1. Facilitated Diffusion (GLUT Transporters):
   • This process occurs via GLUT transporters (such as GLUT1, GLUT2, GLUT4, etc.).
   • Facilitated diffusion allows glucose to enter the cell along its concentration gradient without energy (ATP).
   • In this process, glucose moves from an area of high concentration to low concentration, but it needs a carrier protein (GLUT) to help it pass through the cell membrane since it cannot cross the lipid bilayer on its own due to its size and polarity.
   • Example: When glucose is present in the blood at higher concentrations, GLUT proteins in cells like those in the liver, muscle, and adipose tissue will allow glucose to diffuse into the cells.
2. Symport (Sodium-Glucose Transporter - SGLT):
   • This mechanism involves SGLT proteins (such as SGLT1 and SGLT2) and is a form of secondary active transport.
   • Symport means that two substances move in the same direction across the membrane. In this case, sodium (Na+) and glucose both move into the cell together.
   • The key here is that sodium ions are moving down their concentration gradient (from high outside the cell to low inside), and this energy is used to pull glucose into the cell against its concentration gradient (from low inside the cell to high inside).
   • Since sodium is moving down its gradient, it doesn’t require direct ATP energy. However, ATP is still involved indirectly because the sodium gradient is maintained by the sodium-potassium pump (which uses ATP to pump sodium out of the cell).
   • Example: In the small intestine or kidneys, glucose is absorbed from the lumen into cells via SGLT, driven by the sodium gradient.

Key Differences:
• Facilitated diffusion (GLUT): Moves glucose down its concentration gradient without energy.
• Symport (SGLT): Moves glucose against its concentration gradient by coupling it with sodium moving down its concentration gradient (indirect energy usage).

So, facilitated diffusion is a simpler, energy-free method when the glucose concentration is higher outside the cell, while symport allows glucose to be actively absorbed against its concentration gradient, often in tissues like the small intestine and kidney.

Both processes are important, but they work under different conditions and with different transport mechanisms.

Does that help clarify the two mechanisms?

Question 7

RBCs lack nucleus and mitochondria. Explain the fluid mosaic model.
State the types of proteins on the cell membrane
All water moves passively in response to an osmotic gradient

Water intake sources include:
Ingested food-60 percent
Solid food-30 percent
Metabolic water is 10 percert
What output:
Urine is 60 percent
Feces is 4%,losses through skin and lungs is 28%,sweat is 8%

Increase in plasma Osmolality triggers thirst.

Osmolality of C is = mole(n)/ volume
Mole = mass / molar mass

Exactly — reabsorption is not the same as absorption.
• Absorption happens when something is taken in for the first time (e.g., nutrients from the small intestine into blood).
• Reabsorption happens when something was already absorbed before but is taken back again (e.g., in the kidneys, where useful substances like glucose and water are reabsorbed from urine back into the blood).

Want a simple example for each?

Higher Osmolality means higher concentration of solute but volume of solution or water remains the same

Hypothalamus has receptors for Osmolality called osmoreceptors

The term for measuring concentration is colorimetry (if you’re using color to measure it) or simply titration (if using a chemical reaction).
• Colorimetry measures how much light a solution absorbs to find its concentration.
• Titration measures how much of a solution you need to react completely with another to find concentration.

Radioactive dushatance is used as a dye in measurement of compartments because it has a half life and disintegrates by itself

V=M/C
V=M-X/C
X is correction factor
M is quantity to be injected
C is conc of body fluids after substance has been distributed equally

Where:
• V = volume of distribution (how much space the substance spreads into)
• M = amount (quantity) of substance injected
• X = correction factor (amount lost, e.g., metabolized or excreted before measurement)
• C = concentration in body fluids after distribution

Simple meaning:
You subtract what was lost (X) from what you injected (M), then divide by the measured concentration (C) to find the volume where the substance spread.

Answer 7

•The cell and its organelles
•The cell membrane: the structure is described as fluid mosaic model:
•Fluid because the components are not linked by chemical bonds so can move freely.
•Mosaic because Proteins are dispersed in a hospholipid bilayer

•Components of the cell membrane: Proteins
• Integral Membrane Proteins are embedded within the lipid bilayer
• Transmembrane Proteins span the membrane and function as ion channels, carrier molecules, enzymes, receptors…
• Peripheral proteins: loosely bound to other proteins and phospholipids usually on the cytosolic side. They function mainly as part of the cytoskeleton

Question 8

Note from the psychology part of molecular:
The enteric system communicates with the CNS via the gut brain axis

Epigenesis refers to external influences that can cause genetic changes and influence gene expression

Social support reduces inflammation and cortisol levels
Social isolation increases oxidative stress and immune dysfunction

SSE factors regulating stress responses. SSE (Sympathetic Stress Endocrine) factors are involved in regulating the body’s stress responses. These factors primarily help the body react to stress through various hormonal, neural, and cellular mechanisms. Here’s how some of these key factors regulate stress responses:
1. Sympathetic Nervous System (SNS):
• The SNS is activated during stress, triggering the “fight or flight” response.
• It increases heart rate, blood pressure, and respiration, preparing the body to deal with immediate threats.
• This activation leads to the release of neurotransmitters like norepinephrine (noradrenaline), which help manage stress responses.
2. Hypothalamic-Pituitary-Adrenal (HPA) Axis:
• The HPA axis is a central part of the body’s endocrine stress response.
• Corticotropin-releasing hormone (CRH) from the hypothalamus stimulates the release of adrenocorticotropic hormone (ACTH) from the pituitary gland.
• ACTH then stimulates the adrenal glands to release cortisol, a key stress hormone that helps the body manage and adapt to stress by regulating metabolism, immune function, and other processes.
3. Corticosteroids (like cortisol):
• Cortisol helps regulate energy usage, suppresses non-essential functions (like digestion), and enhances the body’s ability to handle stress.
• Prolonged high levels of cortisol can negatively affect the body, leading to issues like immune suppression, increased blood sugar, and even neural changes.
4. Catecholamines (Epinephrine and Norepinephrine):
• Epinephrine (adrenaline) and norepinephrine are released from the adrenal medulla during stress and are critical in mobilizing the body’s resources to respond to stress.
• They increase heart rate, blood flow to muscles, and enhance focus by stimulating the central nervous system.
5. Endorphins:
• Endorphins are neurochemicals that act as natural painkillers and mood elevators.
• During stress, endorphins help reduce pain and induce feelings of euphoria or well-being, counteracting the negative effects of stress.
6. Immune Response:
• Stress activates immune responses through cytokines and other immune system mediators.
• Acute stress can enhance the immune response, but chronic stress may suppress it, making the body more vulnerable to infections.

In summary, these SSE factors work together to prepare the body to respond to stress, but if stress becomes chronic, it can lead to negative consequences on health, including mental and physical diseases.

Total body water is 42 L
ICF is 28
Ecf is 14(interstitial which ia fluid between the cells is 10,plasma 3, trans cellular which is fluid in
some special spaces and some organs example is synovial fluid 1L)

Hydrogen phosphate,magnesium,sulfate ion are all more in the ICF.
Sodium and bicarbonate and calcium are more in the ECf

Inside of a cell is more polar or negatively charged. A lot of the negativity is associated with proteins

Explain Starlings law of capillary filtration.

Answer 8

The four forces that help maintain fluid balance across capillary membranes are:
1. Capillary Hydrostatic Pressure (CHP):
• This is the pressure exerted by the fluid inside the capillaries, which pushes fluid out of the capillaries into the interstitial space. It is often referred to as the “filtration” pressure.
2. Interstitial Fluid Hydrostatic Pressure (IFHP):
• This is the pressure exerted by the fluid in the interstitial space (the space between cells). It tends to push fluid into the capillaries. This pressure is typically very low.
3. Capillary Oncotic (or Osmotic) Pressure (COP):
• This is the pressure exerted by the proteins (mainly albumin) in the blood plasma, which draws water into the capillaries from the interstitial space. It helps to retain fluid within the capillaries.
4. Interstitial Fluid Oncotic Pressure (IFOP):
• This is the osmotic pressure exerted by the proteins present in the interstitial fluid, which tends to draw water out of the capillaries and into the interstitial space. However, the concentration of proteins in the interstitial fluid is typically much lower than in the plasma, so its effect is relatively small compared to the capillary oncotic pressure.

Starling’s Law of Capillary Filtration:

Starling’s law describes how these four forces work together to regulate fluid exchange between the capillaries and the surrounding tissues. The net movement of fluid across the capillary membrane is determined by the balance between hydrostatic pressures and oncotic pressures.
• Net filtration pressure (NFP) = (Capillary hydrostatic pressure + Interstitial oncotic pressure) - (Interstitial hydrostatic pressure + Capillary oncotic pressure)

In simple terms:
• Filtration occurs when the capillary hydrostatic pressure is greater than the oncotic pressure, pushing fluid out of the capillaries.
• Reabsorption happens when the capillary oncotic pressure exceeds the hydrostatic pressure, pulling fluid back into the capillaries.

When this balance is disrupted, it can lead to conditions like edema, where excess fluid accumulates in the tissues.

Fluid shifting:
If ECF becomes hypertonic or more concentrated relative to the IcF, water moves from the ICF to the ECF.
If ICF is more dilute than ECf, water will move from ICF to ECF(osmosis)
If Ecf becomes hypotonic relative to ICf, water moves from ICF into cells

Question 9

Components of trans cellular fluid
Lymph Is part of interstitial fluid.

Answer 9

The transcellular compartment refers to a specialized part of the extracellular fluid (ECF) that exists within certain epithelial-lined spaces or compartments in the body. It is distinct from the interstitial and plasma compartments of the ECF.

Here are the main components of the transcellular compartment:
1. Cerebrospinal fluid (CSF): This is found in the brain and spinal cord, in the ventricles and around the brain in the subarachnoid space.
2. Synovial fluid: This is found in the cavities of synovial joints and helps with lubrication.
3. Intraocular fluid (aqueous humor): Found in the anterior and posterior chambers of the eye, providing nourishment and maintaining intraocular pressure.
4. Pleural fluid: This is found in the pleural cavity, which surrounds the lungs, aiding in lung expansion and reducing friction.
5. Peritoneal fluid: This is present in the peritoneal cavity, a space between the abdominal walls and the organs, allowing smooth movement of abdominal organs.
6. Pericardial fluid: This is found in the pericardial cavity surrounding the heart, providing lubrication and reducing friction as the heart beats.

These fluids are distinct because they are located in compartments that are physically separated from the blood and interstitial fluids by epithelial layers, hence they are referred to as transcellular compartments.

Question 10

Psychology part of molecular:
What’s the effect of chronic stress of the hypothalamus pituitary adrenal axis

Psychological stress increases what pro inflammatory cytokines?

Psychological experiences alter gene expression via DNA methylation. This is an epigenetic modification. Histone modification is another example of epigenetic modification.

Answer 10

It activates the axis and the axis Produces excessive cortisol and this disrupts cellular homeostasis. It suppresses immune function and increases inflammation and makes you susceptible to infections and is linked to cancer and autoimmunity

IL-6,TNF alpha.

Long term stress can lead to epigenetic changes affecting brain and immune function. These are what influence mental health and disease susceptibility (probably why stressed people are always looking sick)

Chronic Stress also increases ROS leading to oxidative damage. Oxidative stress accelerates aging and contributed to neurodegeneration.
Chronic stress shortens telomeres leading to premature cell aging.(probably why chronically stressed people look older age than their ages)

Gut-Brain Axis and Microbiome
• Psychological stress alters gut microbiota composition.
• Dysbiosis affects immune responses and contributes to mental disorders.
• Gut microbiota regulate neurotransmitter production and overall health.

Mitochondrial Function and Energy
Metabolism
• Stress disrupts mitochondrial energy production.
• Leads to fatigue, metabolic disorders, and neurodegeneration.
• Mitochondrial dysfunction plays a role in aging and disease progression.

Conclusion
• Psychological factors significantly impact cellular and molecular health.
• Chronic stress, inflammation, and epigenetic changes contribute to disease.
• Managing mental health can improve overall well-being and longevity.

Question 11

Still on psychology note of molecular

Health and disease are influenced by social, spiritual, and environmental factors.
• These
factors regulate stress
responses, immune function, and inflammation.
• Understanding their molecular impact can aid in disease prevention.

Social support reduces cortisol levels and inflammation.
Social isolation increases oxidative stress and immune dysfunction.

Socioeconomic status affects stress, epigenetics, and disease risk.
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Effects of Social Support on Cellular Health
• Strong relationships enhance immune function and recovery.
• Positive social interactions lower pro- inflammatory markers.
• Chronic stress from isolation accelerates aging and disease progression.
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SpiritualFactorsa n dCellularHealth
• Meditationandprayerregulatestressand inflammation.
• Spiritualpracticesactivatebeneficialgene expression.
• Emotionalresiliencereduceschronicstress effectso ncellularaging.
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Epigenetics and Mind-Body Connection
• Mindfulness can alter gene expression to
reduce
inflammation.
• Stress-reducing spiritual practices promote healthy cellular function.
• The placebo effect triggers brain signals that enhance healing.
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Environmental Factors and Molecular Health
• Pollution increases oxidative stress and DNA damage.
• Poor diet leads to chronic inflammation and metabolic disorders.
• Green spaces promote relaxation and reduce molecular stress markers.

Answer 11

Yes, that’s true!

The placebo effect happens when a person feels better after receiving a fake treatment, just because they believe it’s real.
• This belief can actually trigger brain signals that release natural chemicals like endorphins and dopamine,
• These chemicals can reduce pain, improve mood, and even boost the body’s own healing processes.

Simple:
Believing you are getting treated can make your brain help your body heal.

Would you like a short example from medicine where the placebo effect is seen clearly?

Exactly — it’s a major concept in psychology too!

In psychology, the placebo effect shows how mental and emotional states (like belief, expectation, and hope) can physically influence the body.
• It proves that thoughts and beliefs can cause real biological changes (like reduced pain, lower stress, better mood).
• It’s used to study how mind-body connection works — how the brain’s expectation can create real improvements without real medicine.

Simple:
In psychology, the placebo effect shows that believing you’re healing can actually trigger real healing through the brain.

Want me to also give you a super short real-life psychology study about it?

Of course! Here’s a quick, exam-friendly summary on the mind-body connection:

Mind-Body Connection (Psychology)
• It means the mind (thoughts, emotions, beliefs) can affect the body’s health.
• Positive thoughts → improve healing, lower stress, boost immunity.
• Negative emotions (like fear, anger) → increase risk of illness (like heart disease, weak immune system).

Key examples:
• Placebo effect: Believing you’re getting treatment makes you heal faster.
• Stress: Mental stress causes real body symptoms (like ulcers, high blood pressure).
• Meditation/Relaxation: Calms the mind → lowers heart rate and blood pressure.

Simple definition:
The mind and body are connected — what you think and feel can directly affect your physical health.

Would you also like a few simple “possible exam questions” about the mind-body connection to practice? (They’ll be super short and quick to revise!)

Question 12

The energy of muscle contraction is derived from the following except:
a- ATP.
b- muscle glycogen. c- lactic acid.
d- Creatine phosphate. c
2- The frequency needed to produce tetanus:
a- is increased by cooling.
b- is decreased in red muscles.
c- is increased in fatigue.
d- is decreased in the pale muscles. b
3- Depolarization:
a- is associated with increase in membrane permeability to Na+. b- is terminated with closure of voltage activated K+ channels. c- is followed by muscle relaxation.
d- is caused by K+ efflux.
a
4- Action potential:
a- is a graded potential.
b- is produced by sub threshold stimulus.
c- starts with repolarization caused by outward movement of Cl-. d- is conducted slower in thin nerve fibers.
d
5- RMP of a nerve:
a- is caused by equal distribution of ions along both sides of the membrane. b- is caused by selective permeability of the membrane to the ions.
c- Na+ - K+ pump has no role in RMP.
d- is caused mainly by inward movement of Na+ ions.
b
6- As regard conduction of action potential in a nerve:
a- in thick myelinated nerve fibers can reach up to 120 meter / second. b- can be increased by increase calcium.
c- can be increased by cooling.
d- is conducted with decrement.

Answer 12

Here are the correct answers with brief explanations for each:

1. The energy of muscle contraction is derived from the following except:
   Correct answer: c. Lactic acid
   Explanation: Lactic acid is a byproduct of anaerobic glycolysis, not an energy source. Energy comes from ATP, creatine phosphate, and muscle glycogen.
2. The frequency needed to produce tetanus:
   Correct answer: b. Is decreased in red muscles
   Explanation: Red (slow-twitch) muscle fibers have longer contraction times and therefore reach tetanus at lower frequencies than fast-twitch (pale) fibers.

To produce tetanus, the muscle must be stimulated quickly enough that each twitch builds on the previous one
So red muscles twitch slowly meaning it takes a long time for them to reach tetanus so you won’t stimulate them as often as you would stimulate the pale muscles thag twitch very fast so their impulses easily die out so you have to increase their frequency of stimulation before you can get to tetanus. So pale you’ll increase and red you’ll decrease.
3. Depolarization:
Correct answer: a. Is associated with increase in membrane permeability to Na+
Explanation: During depolarization, voltage-gated Na+ channels open, allowing Na+ to enter the cell and make the inside more positive.

4. Action potential:
   Correct answer: d. Is conducted slower in thin nerve fibers
   Explanation: Thinner fibers and unmyelinated axons conduct action potentials more slowly than thick, myelinated fibers.
5. Resting membrane potential (RMP) of a nerve:
   Correct answer: b. Is caused by selective permeability of the membrane to the ions
   Explanation: The membrane is more permeable to K+ than Na+, leading to a negative resting potential. Na+/K+ pump also contributes but selectively permeability is key.
6. As regard conduction of action potential in a nerve:
   Correct answer: a. In thick myelinated nerve fibers can reach up to 120 meters/second
   Explanation: Myelinated axons conduct action potentials rapidly via saltatory conduction. Calcium doesn’t increase conduction speed, and cooling slows it down.

Let me know if you’d like this in a printable study table format!

Let’s break down number 2:

Question:
The frequency needed to produce tetanus:
a) is increased by cooling
b) is decreased in red muscles
c) is increased in fatigue
d) is decreased in the pale muscles

Correct answer: b) is decreased in red muscles

Why?

To produce tetanus, the muscle must be stimulated quickly enough that each twitch builds on the previous one. This required frequency varies depending on the muscle type.
• Red muscles (slow-twitch) contract and relax slowly. Because of this slower response, they need a lower frequency to reach tetanus.
• Pale muscles (fast-twitch) contract quickly and require higher frequencies to reach tetanus because they relax more quickly.

What about the other options?
• a) Increased by cooling – Cooling slows everything down, including nerve and muscle activity, but it does not increase the frequency needed for tetanus; in fact, it might reduce it.
• c) Increased in fatigue – Fatigue makes it harder for muscles to respond, but it does not increase the required frequency for tetanus.
• d) Decreased in pale muscles – Pale muscles need higher, not lower, frequencies.

Would you like a chart showing red vs pale muscle characteristics?

Question 13

• Pale (fast) fiber:
  a- contains much blood capillaries.
  b- doesn’t show fatigue.
  c- contains low concentration of myoglobin. d- depends on aerobic oxidation.
  c
  8- About cellular sheath ( sheath of Schwann):
  a- It acts as an electric insulator around the nerve fiber.
  b- It surrounds the axons of all neurons inside and outside the CNS. c- It is responsible for the color of the white matter of the spinal cord. d- It is essential for regeneration of the damaged verve fibers.
  d
  9- Myelin sheath:
  a- Present in the myelinated and unmyelinated nerve fibers.
  b- Formed of lipoprotein complex and acts as electric insulator.
  c- It is formed of successive wrappings of the membrane of Schwann cells. d- It is the cause of decreased conduction of nerve impulse.
  b
  10- Chronaxia:
  a- is the minimal stimulus which produce response after relatively long time.
  b- is the minimal time needed by the strong stimulus to produce response.
  c- is the time required to stimulate the nerve by a minimal stimulus.
  d- is the time required to stimulate the nerve by a stimulus which is double rheobase. d
  11- During depolarization:
  a- voltage activated Na+ channels open.
  b- the membrane becomes impermeable to Na+.
  c- when membrane potential reaches -55 m.v Na+& K+ fluxes occur at the same time. d- K+ ions diffuse outside.
  a
  12- The resting membrane potential is caused by:
  a- Diffusion of K+ ions outside the nerve fibers.
  b- Diffusion of Na+ ions inside the nerve fibers.
  c- Opening of the chemically activated ion channels. d- Opening of the voltage activated ion channels.
  a
  13- To measure resting membrane potential:
  a- We use a special voltmeter or cathode ray oscilloscope (CRO).
  2b- We put the two electrodes outside the nerve fiber. c- We stimulate the nerve by an effective stimulus. d- We put the two electrodes inside the nerve fiber.

14- Repolarization:
a- Occurs at first gradual then becomes fast.
b- Results from closure of sodium gates and opening of potassium gates. c- is represented by the ascending limb of the spike.
d- is followed by appearance of response.
b
15- Continuous conduction:
a- occurs in myelinated nerve fibers.
b- occurs by jumping of charges from one node of Ranvier to another. c- is relatively slow 0.5-2.0 meter / second.
d- occurs in the neuro-muscular junction.
c
16- Saltatory conduction:
a- occurs in unmyelinated nerve fibers.
b- may reach up to 120 meter / second.
c- occurs by jumping from one neuron to another.
d- decreases gradually with distance till it disappears. b
18- In monophasic action potential:
a- One electrode is put inside and the other is put outside the same nerve fiber. b- The spike is a large wave of short duration.
c- The spike is followed by positive after potential then negative after potential. d- The ascending limb of the spike is due to K+ efflux.
b
19- Local excitatory state is characterized by the following except:
a- its magnitude is directly proportional with the intensity of the sub-minimal stimulus. b- does not obey all or non rule.
c- can be summated.
d- propagated without decrement.
d
20- About A fibers all are true except:
a- They have the greatest diameter.
b- They conduct impulses with the greatest velocity (10-120 met./sec) c- They include somatic sensory and motor fibers.
d- They are very sensitive to local anesthetic drugs.
3

d
21- In all or non rule:
a- A minimal stimulus produces a maximal response.
b- The response in a single nerve fiber increases with increase intensity of stimulus. c- The nerve trunk either respond maximally or not respond at all.
d- Minimal stimulus produces minimal response.
a
22- Excitation contraction coupling involves all the following except:
a- Release of Ca++ from troponin.
b- Formation of cross bridges between actin and myosin. c- Spread of depolarization along the transverse tubules. d- Hydrolysis of ATP to ADP.
a
23- Muscle fatigue is due to:
a- Inability of the action potential to spread over the muscle. b- Failure of transmission in the motor nerve.
c- Failure of neuro-muscular transmission.
d- Depletion of energy stores.

24- An-electrotonus :
a- is a localized area of depolarization.
b- results from stimulation by effective galvanic current . c- is associated with decreased excitability.
d- used to stimulate the nerve fibers
c
25- Nerve block is produced by:
a- Sever cooling.
b- Strong catelectrotonus. c- Decrease Ca++ ions.
d- Increased Na+ ions.
a
26- Which of the following has the lowest conduction velocity:
a- A α fibers. b- A β fibers. c- B fibers. d- C fibers.
c
27- The function of tropomyosin in skeletal muscle include:
a- binding to myosin during contraction
4

b- acting as a relaxing protein at rest by covering the binding sites on actin. c- sliding on actin to produce shortening.
d- releasing Ca++ after propagation of action potential.
b
28- Contraction of skeletal muscles:
a- produces more work when the muscle contracts isometrically than when the muscle contracts isotonically.
b- depends on external Ca++.
c- decrease in magnitude with rapid repeated stimulation. d- does not depend on action potential.
c
29- The motor end plate potential is produced by:
a- opening of Na+ channels.
b- opening of Na+ channels then opening of K+ channels. c- opening of Na+ and K+ channels at the same time.
d- opening of Ca++ channels.
c
30- Nerve block is produced by all the following except:
a- local anesthetics.
b- excessive cooling.
c- deep pressure.
d- strong cat-electrotonus. d
31- As regard neuro-muscular transmission all are true except:
a- it shows fatigue due to depletion of acetylcholine vesicles. b- occurs from nerve to muscle i.e. one way conduction.
c- it is stimulated by succinyl choline.
d- it is blocked by botulinum toxins.
c
32- Red ( slow ) fibers are characterized by the following except:
a- contains much blood capillaries.
b- glycogen stores is low.
c- contains high concentration of myoglobin.
d- depends on anaerobic oxidation.
d
33- Neuromuscular transmission is blocked by:
a- prostigmine .
b- increase Ca++ ions. c- acetylcholine .
5

d- succinylcholine.
d
34- All about the Sarcomere are true except:
a- is the distance between myosin and actin. b- is the distance between two Z membranes. c- is the contractile unite of the muscle.
d- shorten when the muscle contracts.

35- Excitability of nerve fibers:
a- is increased by decreased temperature.
b- is increased by decreased Na+.
c- is decreased by decrease Ca++ ions.
d- is completely lost by local anesthetic drugs.

What is the name of the distance between actin and myosin?

That space is known as the:

H zone (or H band)

Details:
• The H zone is the part of the sarcomere where only myosin is present — no overlapping actin.
• During muscle contraction, actin slides in, and the H zone narrows or disappears.
• It’s located in the center of the A band.

Answer 13

Let’s go through each of these MCQs quickly and clearly:

7. Pale (fast) fiber:
   Correct answer: c) contains low concentration of myoglobin

Explanation:
Pale (fast-twitch) fibers are:
• Low in myoglobin (so they look pale)
• Have few capillaries
• Fatigue quickly
• Use anaerobic metabolism for energy

8. About cellular sheath (Sheath of Schwann):
   Correct answer: d) It is essential for regeneration of the damaged nerve fibers

Explanation:
Schwann cells help in nerve regeneration in the peripheral nervous system (PNS). They don’t surround all CNS neurons—that’s oligodendrocytes’ job.

9. Myelin sheath:
   Correct answer: b) Formed of lipoprotein complex and acts as electric insulator

Explanation:
• Myelin is made of fats and proteins (lipoproteins)
• It insulates and speeds up conduction
• Only myelinated fibers have a myelin sheath, not unmyelinated ones
• It increases, not decreases, conduction speed

10. Chronaxia:
    Correct answer: d) is the time required to stimulate the nerve by a stimulus which is double rheobase

Explanation:
• Rheobase: the minimum strength of a stimulus that can trigger a response
• Chronaxia: the time it takes for a stimulus twice the rheobase to trigger a response
• A way to measure nerve excitability

11. During depolarization:
    Correct answer: a) voltage activated Na+ channels open

Explanation:
• When a nerve is stimulated and reaches threshold, Na+ channels open, Na+ rushes in, and the inside becomes positive (depolarization).

12. The resting membrane potential is caused by:
    Correct answer: a) Diffusion of K+ ions outside the nerve fibers

Explanation:
• More K+ leaks out than Na+ leaks in
• The membrane is more permeable to K+ at rest
• This leads to a negative resting potential (~ -70 mV)

13. To measure resting membrane potential:
    Correct answer: a) We use a special voltmeter or cathode ray oscilloscope (CRO)

Explanation:
• One electrode is placed inside the cell, and the other outside
• A CRO or voltmeter shows the voltage difference (resting membrane potential)

Let me know if you’d like a summary chart for muscle fibers or nerve terms!

Here are the explanations for each of the MCQs you’ve provided:

14. Repolarization:
    Correct answer: b) Results from closure of sodium gates and opening of potassium gates

Explanation:
• Repolarization occurs when sodium (Na+) channels close, and potassium (K+) channels open, allowing K+ to flow out, restoring the negative resting membrane potential.

15. Continuous conduction:
    Correct answer: c) is relatively slow 0.5-2.0 meter / second

Explanation:
• Continuous conduction happens in unmyelinated fibers, where the action potential moves slowly along the entire length of the fiber.

16. Saltatory conduction:
    Correct answer: b) may reach up to 120 meter / second

Explanation:
• Saltatory conduction occurs in myelinated fibers and is much faster (up to 120 m/s) as the action potential “jumps” between the nodes of Ranvier.

18. In monophasic action potential:
    Correct answer: b) The spike is a large wave of short duration

Explanation:
• In a monophasic action potential, the spike represents a single large wave (depolarization) of short duration, often recorded in experimental setups.

19. Local excitatory state is characterized by the following except:
    Correct answer: d) propagated without decrement

Explanation:
• The local excitatory state does not propagate without decrement. It can be summated but typically does not travel long distances without diminishing.

Here are the correct answers and explanations for the 3 multiple-choice questions:

1. Local excitatory state is characterized by the following except:

Correct answer: d- Propagated without decrement.

Explanation:

The local excitatory state (or local potential) is a graded potential, not an action potential. It:
• a: Yes – It is graded, so its magnitude increases with stimulus intensity. (True)
• b: Yes – It does not obey the all-or-none law. (True)
• c: Yes – It can be summated (temporal and spatial summation). (True)
• d: False – It is not propagated like action potentials. It decays with distance (decremental conduction), so this is the correct “except” choice.

2. About A fibers, all are true except:

Correct answer: d- They are very sensitive to local anesthetic drugs.

Explanation:
• a: True – A fibers are the largest diameter fibers.
• b: True – They have the fastest conduction velocity (up to 120 m/s).
• c: True – They include somatic motor and sensory fibers.
• d: False – They are less sensitive to local anesthetics. Smaller fibers (like C fibers) are more sensitive because anesthetics block sodium channels more effectively in small, unmyelinated fibers.

3. In all-or-none rule:

Correct answer: c- The nerve trunk either responds maximally or not respond at all.

Explanation:
• a: False – A minimal stimulus only causes a response if it’s threshold or higher. A threshold stimulus causes a maximal response. So this is inaccurately worded.
• b: False – In a single nerve fiber, increasing stimulus does not increase response size. It’s either full response or none.
• c: True – In a nerve trunk (many fibers), as you increase intensity, more fibers are recruited. But each fiber still follows all-or-none.
• d: False – Minimal (subthreshold) stimulus causes no response.

So c is the correct statement about the all-or-none rule.

Would you like more MCQs explained like this?

20. About A fibers all are true except:
    Correct answer: d) They are very sensitive to local anesthetic drugs

Explanation:
• A fibers are large, myelinated, and conduct impulses quickly. They are less sensitive to anesthetics compared to smaller fibers.

21. In all or non rule:
    Correct answer: a) A minimal stimulus produces a maximal response

Explanation:
• The “all or none” law states that a minimal stimulus that reaches threshold will cause the full response. Any sub-threshold stimulus won’t trigger a response.

22. Excitation-contraction coupling involves all the following except:
    Correct answer: a) Release of Ca++ from troponin

Explanation:
• During excitation-contraction coupling, Ca++ is released from the sarcoplasmic reticulum, not from troponin. Troponin binds Ca++.

23. Muscle fatigue is due to:
    Correct answer: d) Depletion of energy stores

Explanation:
• Muscle fatigue is caused by energy depletion (ATP, glycogen) during prolonged activity, reducing muscle function.

24. An-electrotonus:
    Correct answer: c) is associated with decreased excitability

Explanation:
• An-electrotonus is the hyperpolarized state of the nerve due to an inhibitory stimulus, leading to decreased excitability.

25. Nerve block is produced by:
    Correct answer: a) Sever cooling

Explanation:
• Severe cooling can block nerve conduction by reducing ion channel activity, leading to nerve block.

26. Which of the following has the lowest conduction velocity:
    Correct answer: d) C fibers

Explanation:
• C fibers are unmyelinated and have the slowest conduction velocity.

27. The function of tropomyosin in skeletal muscle include:
    Correct answer: b) acting as a relaxing protein at rest by covering the binding sites on actin

Explanation:
• Tropomyosin covers the actin binding sites at rest, preventing cross-bridge formation until Ca++ binds to troponin, shifting tropomyosin.

28. Contraction of skeletal muscles:
    Correct answer: c) decrease in magnitude with rapid repeated stimulation

Explanation:
• Twitch summation (rapid repeated stimulation) leads to fatigue and decrease in contraction strength.

29. The motor end plate potential is produced by:
    Correct answer: c) opening of Na+ and K+ channels at the same time

Explanation:
• At the motor end plate, both Na+ and K+ channels open, leading to a change in membrane potential (depolarization).

30. Nerve block is produced by all the following except:
    Correct answer: d) strong cat-electrotonus

Explanation:
• Cat-electrotonus (an increase in excitability) does not block nerves. Nerve block is caused by local anesthetics, cooling, and pressure.

31. As regards neuro-muscular transmission, all are true except:
    Correct answer: c) it is stimulated by succinylcholine

Explanation:
• Succinylcholine mimics acetylcholine but causes prolonged depolarization, which is not a normal physiological process in neuromuscular transmission.

32. Red (slow) fibers are characterized by the following except:
    Correct answer: d) depends on anaerobic oxidation

Explanation:
• Red (slow-twitch) fibers are rich in myoglobin and rely on aerobic metabolism (not anaerobic) for energy.

33. Neuromuscular transmission is blocked by:
    Correct answer: d) succinylcholine

Explanation:
• Succinylcholine prevents neuromuscular transmission by mimicking acetylcholine and causing sustained depolarization, leading to muscle paralysis.

34. All about the Sarcomere are true except:
    Correct answer: a) is the distance between myosin and actin

Explanation:
• The sarcomere is the distance between two Z-lines and contains both myosin and actin, but it is not the direct distance between them.

35. Excitability of nerve fibers:
    Correct answer: d) is completely lost by local anesthetic drugs

Explanation:
• Local anesthetics block the ability of nerve fibers to transmit action potentials, completely reducing excitability.

Let me know if you need further clarification!

Let’s go through each question and explain the correct answers and why:

28. Contraction of skeletal muscles:Correct answer: c – Decrease in magnitude with rapid repeated stimulation

Explanation:
• This refers to muscle fatigue. With repeated stimulation, muscles fatigue, and contraction force gradually decreases.
• Let’s briefly evaluate the other options:

Option True/False Why
a. Isometric > Isotonic False Isometric contraction generates tension without shortening; isotonic does actual work (movement), so it’s more related to work output.
b. Depends on external Ca²⁺ False Skeletal muscle uses internal Ca²⁺ from the sarcoplasmic reticulum. External Ca²⁺ is more important in cardiac and smooth muscle.
d. Does not depend on AP False Skeletal muscle must have an action potential to contract. No AP = no contraction.

29. The motor end plate potential is produced by:Correct answer: c – Opening of Na⁺ and K⁺ channels at the same time

Explanation:
• At the neuromuscular junction, acetylcholine (ACh) binds to nicotinic receptors, opening ligand-gated ion channels that allow both Na⁺ in and K⁺ out.
• More Na⁺ enters than K⁺ leaves, causing depolarization (end plate potential).

Option Why it’s wrong
a. Only Na⁺ Not just Na⁺ — both ions move.
b. Na⁺ then K⁺ They move simultaneously.
d. Ca²⁺ Ca²⁺ entry is involved in neurotransmitter release, not the end plate potential itself.

30. Nerve block is produced by all except:Correct answer: d – Strong cat-electrotonus

Explanation:
• Nerve block means stopping nerve conduction, and this can be caused by:
• Local anesthetics: block Na⁺ channels.
• Cooling: slows ion channel function.
• Deep pressure: can physically compress nerves.
• Strong cathodal (cat-) electrotonus actually depolarizes the nerve and increases excitability, not block it.

Option Why it’s incorrect as a cause of block
d. Strong cat-electrotonus It enhances nerve excitability rather than blocking it.

Let me know if you’d like a mnemonic for end plate potentials or muscle contraction types!

Question 14

Properties of graded potentials

Answer 14

The local excitatory state (also called a graded potential) is not an action potential.
• It has the following properties:
• Graded: Its size depends on stimulus strength.
• Can be summed: Both temporal and spatial summation.
• Decremental: It fades with distance.
• Not all-or-none: It can be small or large, depending on stimulus strength.

So, graded potentials like the local excitatory state do NOT obey the all-or-none law. Only action potentials do.