Zoology 2425 – Physiology Labs Final Review

This set of flashcards covers key questions and answers from each physiology laboratory topic—pH and buffers, enzymes, diffusion/osmosis, neurophysiology, sensory systems, muscle physiology, cardiac function, hematology, ECG, respiratory mechanics, and renal regulation—providing a comprehensive review for the Zoology 2425 final.

If hydrogen-ion concentration increases in a solution, what happens to its pH?

The pH decreases (solution becomes more acidic).

If hydrogen-ion concentration decreases, what happens to pH?

The pH increases (solution becomes more basic).

Each whole number change on the pH scale equals what fold change in [H⁺]?

A ten-fold change.

What is a buffer?

A substance that resists large changes in pH when acid or base is added.

How does a buffer minimize pH change?

By alternately binding or releasing hydrogen ions according to the law of mass action.

Which buffer was used in Lab 2?

The bicarbonate buffer system (NaHCO₃ / H₂CO₃).

Give the bicarbonate buffer equation.

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃⁻

Shifting the bicarbonate equation to the right has what effect on pH?

Raises [H⁺] and lowers pH (more acidic).

Blood pH below 7.35 is called ____; above 7.45 is called ____.

Acidosis; alkalosis.

Excessive vomiting typically causes which acid–base disorder?

Metabolic alkalosis (loss of stomach acid).

Diarrhea generally leads to which acid–base disorder?

Metabolic acidosis (loss of bicarbonate).

Hyperventilating because of fear causes what acid–base disturbance?

Respiratory alkalosis (excess CO₂ loss).

Hypoventilation due to narcotics tends to cause ____.

Respiratory acidosis.

Why did titrating NaCl with strong acid drop pH sharply?

NaCl provides no buffering capacity; added H⁺ remains free in solution.

Why did NaHCO₃ resist pH change compared with NaCl when acid was added?

HCO₃⁻ acted as a buffer, converting to H₂CO₃ and limiting free H⁺ rise.

What is an enzyme?

A biological catalyst made of protein that speeds specific reactions without being consumed.

Can an enzyme catalyze any reaction?

No, each enzyme is specific to its substrate(s).

Define substrate in enzymology.

The reactant molecule(s) upon which an enzyme acts.

Define product in an enzyme-catalyzed reaction.

The molecule(s) produced after the enzyme converts the substrate.

Increasing enzyme concentration generally has what effect on reaction rate (assuming excess substrate)?

It increases reaction rate proportionally until substrate becomes limiting.

What happens to enzyme activity if temperature rises above the optimum?

Activity drops due to enzyme denaturation.

Write the catalase reaction for hydrogen peroxide breakdown.

2 H₂O₂ --catalase→ 2 H₂O + O₂

Which organ contains many peroxisomes rich in catalase?

The liver.

Why is catalase needed in peroxisomes?

To degrade toxic H₂O₂ generated by oxidases during fatty-acid breakdown.

Define diffusion.

Net movement of molecules from high to low concentration due to random kinetic motion.

Does diffusion require input of cellular energy?

No, it is a passive process.

How does molecule size affect diffusion rate?

Smaller molecules diffuse faster than larger ones.

How does temperature affect diffusion?

Higher temperature increases molecular motion and diffusion rate.

Define solute, solvent, and solution.

Solute: substance dissolved; solvent: substance doing the dissolving; solution: homogeneous mixture of solute in solvent.

What is osmosis?

Diffusion of water across a selectively permeable membrane from low solute concentration to high solute concentration.

Normal human plasma osmolarity is about ____ mOsm.

300 mOsm (≈ 285–295 mOsm).

An isotonic NaCl solution is approximately what percent?

0.9 % NaCl.

An isotonic glucose (dextrose) solution is approximately what percent?

5 % glucose (D5W).

What happens to a red blood cell in a hypertonic solution?

It shrinks (crenates) as water leaves the cell.

Name the three types of voltage-gated channels on a neuron.

Voltage-gated Na⁺ channels, voltage-gated K⁺ channels, voltage-gated Ca²⁺ channels.

Which channels establish the resting membrane potential?

K⁺ leak channels, Na⁺ leak channels, and the Na⁺/K⁺ ATPase pump.

Depolarization phase of an action potential is caused by opening of ____ channels.

Voltage-gated Na⁺ channels.

Repolarization is primarily due to opening of ____ channels.

Voltage-gated K⁺ channels.

Define absolute refractory period.

Time during which a second AP cannot be initiated because Na⁺ channels are inactivated.

What is the effect of monosodium glutamate (MSG) on neuronal activity?

Increases activity by acting as an excitatory glutamate agonist.

How does nicotine affect nerve activity?

Stimulates nicotinic ACh receptors, increasing excitability.

Adding CaCl₂ to extracellular fluid usually ____ neuronal excitability.

Decreases it by raising threshold (more Ca²⁺ stabilizes membrane).

What is a receptive field?

The area over which a sensory neuron collects stimuli.

How does high receptor density affect two-point discrimination threshold?

It lowers the threshold, allowing finer spatial resolution.

Slow-adapting (tonic) receptors respond how to constant stimulus?

They continue to fire APs with little decrease in frequency.

Rapidly-adapting (phasic) receptors respond how to constant stimulus?

They fire at stimulus onset/offset and quickly stop during constant stimulation.

Function of muscle spindle fibers?

Detect muscle stretch and initiate stretch reflex to resist lengthening.

What is referred pain?

Perception of visceral pain as originating from a somatic (skin or muscle) location.

Myopia results from what optical problem?

Eyeball too long or lens too strong, focusing image in front of retina.

Which lens corrects myopia?

A concave (diverging) lens.

Hyperopia is caused by ____.

Eyeball too short or lens too weak, focusing image behind retina.

Which lens corrects hyperopia?

A convex (converging) lens.

Why is color blindness more common in males?

Most color-vision genes are X-linked; males have only one X chromosome.

How does the nervous system code for stimulus intensity if APs are all-or-none?

By frequency of action potentials and number of recruited afferent fibers (population coding).

How is pitch encoded in the cochlea?

By which region of the basilar membrane vibrates (place coding; base = high pitch, apex = low pitch).

How is volume of sound encoded?

By the amplitude of basilar membrane vibration, producing higher firing rates in hair cells.

What is the A band of a sarcomere?

Region containing the full length of thick (myosin) filaments; appears dark.

What happens to the I band during contraction?

I band (thin filament region) shortens as actin slides toward the M line.

Define motor unit.

A motor neuron and all the muscle fibers it innervates.

Name the proteins directly involved in sarcomere contraction.

Actin, myosin, troponin, tropomyosin.

Briefly list steps from a motor-neuron AP to muscle contraction.

AP in motor neuron → ACh release → end-plate potential → muscle AP → Ca²⁺ release from SR → Ca²⁺ binds troponin → tropomyosin shifts → cross-bridge cycling → contraction.

Parts of a muscle twitch?

Latent period, contraction phase, relaxation phase.

Early strength gains from resistance training are due primarily to what component?

Neural adaptations (improved motor unit recruitment) for ~4–6 weeks.

First type of muscle fatigue (rapid onset) is caused by ____ and typical in ____.

Neuromuscular transmission failure (ACh depletion); high-intensity weight lifting.

Glycolytic muscle fibers are specialized for what activities?

Short, powerful bursts like sprinting; rely on anaerobic glycolysis.

Increasing stimulus size to a muscle recruits more ____.

Motor units (motor unit recruitment) increasing contraction strength.

Increasing stimulation frequency can lead to ___, strengthening contraction.

Temporal summation and tetanus.

What feature do cardiac and skeletal muscle cells share?

Striations composed of organized sarcomeres.

What cell-to-cell junction allows electrical coupling in cardiac muscle?

Gap junctions within intercalated discs.

Conductive cardiac cells have what primary purpose?

Generate and propagate action potentials to coordinate contraction.

What is the Langendorff heart setup?

An isolated heart perfused retrogradely through the aorta with oxygenated Krebs solution to measure contractile force and rate.

Effect of adrenaline (epinephrine) on the heart?

Increases heart rate and contractility via β₁-adrenergic receptors.

Effect of acetylcholine on the heart?

Decreases heart rate via muscarinic receptors on the SA node.

What does verapamil do to heart tissue?

Blocks L-type Ca²⁺ channels, reducing contractility and heart rate.

Normal hematocrit range for males vs females?

Males ~42–52 %; females ~37–47 %.

Typical erythrocyte (RBC) count per μL of blood?

About 4.5–6 million/μL.

Where are ABO and Rh antigens located?

On the surface of erythrocytes.

If B antibodies agglutinate your blood, what is your ABO type?

Type B (surface antigen B present).

How many alleles are involved in the ABO system and which are dominant?

Three alleles (IA, IB, i); IA and IB are codominant over i.

Rh incompatibility risk exists when mother is ____ and fetus is ____.

Rh-negative; Rh-positive.

What preventative treatment is given for Rh incompatibility?

Rho(D) immune globulin injection (RhoGAM).

What does the P wave represent on an ECG?

Atrial depolarization.

QRS complex corresponds to which electrical event?

Ventricular depolarization (and atrial repolarization).

What is the role of the SA node?

Acts as primary pacemaker initiating each heartbeat.

Autorhythmic cells contain which special ion channel responsible for spontaneous depolarization?

Funny current (I_f) channels permeable to Na⁺ and K⁺.

During inspiration, which muscles chiefly expand the thoracic cavity?

Diaphragm contracts (flattens) and external intercostals lift ribs.

Define tidal volume (TV).

Volume of air inhaled or exhaled in a normal quiet breath (~500 mL).

Obstructive lung disease primarily affects which spirometric value?

Forced expiratory volume (FEV₁) is reduced relative to FVC.

Example of a restrictive lung disease.

Pulmonary fibrosis (also scoliosis, sarcoidosis, etc.).

Central chemoreceptors respond chiefly to changes in ____ in cerebrospinal fluid.

CO₂ (via H⁺ concentration).

Hyperventilation allows longer breath-holding by lowering arterial ____.

CO₂ levels (PaCO₂).

Proteinuria may indicate dysfunction of what renal structure?

Glomerular filtration barrier (e.g., glomerulonephritis).

What condition commonly causes glycosuria?

Uncontrolled diabetes mellitus (plasma glucose exceeds renal threshold).

ADH release is stimulated by what physiological change?

Increased plasma osmolarity or severe blood volume loss.

Effect of ADH on the kidney?

Increases water reabsorption in collecting ducts, concentrating urine.

Aldosterone release is triggered primarily by ____ or ____.

High plasma K⁺ or activation of the renin-angiotensin system (low blood pressure).

Atrial natriuretic factor (ANF) is released in response to ____ and causes what renal effect?

Atrial stretch/high blood volume; increases Na⁺ and water excretion.

Drinking a large volume of water does what to ADH levels and urine output?

Suppresses ADH; increases urine volume and lowers specific gravity.

Ingesting high salt load will have what effect on aldosterone secretion?

Suppresses aldosterone; Na⁺ excretion increases (after ANF release).