Human Physiology – Comprehensive Review

100 English fill-in-the-blank flashcards covering major concepts from membrane transport to cellular organelles.

A small, non-polar molecule can easily cross the plasma membrane because it can diffuse through the __.

phospholipid bilayer

The phospholipid bilayer is virtually impermeable to __ such as Na⁺, K⁺ and Ca²⁺.

ions

Ion channels that are always open in the cell membrane are called __ channels.

leakage

Movement of an ion through an open membrane channel is an example of __ mediated transport.

passive

Facilitated transport is mediated by membrane carriers and __ require ATP.

does not

The Na⁺/K⁺-ATPase exchanges __ Na⁺ out for 2 K⁺ in each cycle.

3

An ion is in electrochemical equilibrium when the membrane potential equals the value predicted by the __ equation.

Nernst

A red blood cell placed in a hypotonic solution absorbs water and may burst, a process called __.

hemolysis

Tonicity describes the __ of a solution relative to plasma.

osmolarity

The Goldman equation calculates membrane potential considering the permeabilities of Na⁺, K⁺ and __.

Cl⁻

An action potential is an all-or-none event: once triggered by a suprathreshold stimulus it always has the same __ and duration.

amplitude

Along an axon, the action potential normally propagates in a __ direction.

unidirectional

During the falling phase of an action potential, membrane permeability to K⁺ increases while permeability to __ decreases.

Na⁺

During the relative refractory period, a sufficiently strong stimulus __ evoke another action potential.

can

Hyperpolarization occurs when the membrane potential becomes more __ than the resting value.

negative

Opening of postsynaptic Na⁺ and K⁺ channels produces an __ (EPSP).

excitatory postsynaptic potential

Spatial summation occurs when two or more graded potentials from different parts of soma or dendrites reach the __ and add together.

trigger zone

Besides receptors, the postsynaptic membrane contains __ that degrade neurotransmitters.

enzymes

Most neurotransmitters are synthesized in the __ of the neuron.

soma

Voltage-gated __ channels are absent from the presynaptic terminal.

Na⁺

ATP hydrolysis during skeletal-muscle contraction drives the cyclic __ of the myosin head on actin.

power-stroke

As an action potential travels down the T-tubules, Ca²⁺ channels in the sarcolemma open and activate ryanodine receptors, releasing Ca²⁺ from the __.

sarcoplasmic reticulum

Cardiac muscle cells are usually mononucleated and interconnected by __ discs.

intercalated

Smooth-muscle contraction is regulated by a mechanism based on __ / dephosphorylation of myosin light chains.

phosphorylation

The elbow joint with biceps lifting the hand functions as a __-class lever.

third

The atlanto-occipital joint with the trapezius acting on the head functions as a __-class lever.

first

The muscular insertion is defined as the __ and mobile attachment of the muscle.

distal

Antagonistic muscles consist of an extensor and a __ acting on the same joint.

flexor

The cell bodies of somatic motoneurons are located in the __ horn of the spinal cord.

anterior

The ventral root of the spinal cord carries __ motor fibers.

efferent

Sympathetic activation dilates the bronchi and __ heart rate.

accelerates

Parasympathetic stimulation typically enhances __ and digestive secretions.

salivary

The cerebellum’s primary role is to coordinate movements and maintain __.

balance

Cortical areas processing touch, pain and temperature lie in the __ lobe.

parietal

In the sensory system, the thalamus receives and processes information before it reaches the __.

cortex

A fast, involuntary spinal response to a stimulus is mediated by a __ arc.

reflex

After the optic chiasm, visual information ultimately reaches the __ lobe.

occipital

Auditory information is processed mainly in the __ lobe.

temporal

The left ventricle has walls __ than those of the right ventricle.

thicker

Cardiac valves prevent the __ of blood within the heart and great vessels.

backflow

Blood flows: right atrium → right ventricle → lungs → left atrium → left ventricle → __.

systemic circulation (body)

The physiological pacemaker of the heart is the __ node.

sinoatrial (SA)

Impulse conduction follows: SA node → AV node → His bundle → bundle branches → __ fibers.

Purkinje

During ventricular systole, the ventricles contract and eject blood into the __.

arteries

Systolic pressure is the arterial pressure during ventricular __.

contraction

Arterial baroreceptors are located in the carotid sinus and the __ arch.

aortic

Peripheral vasodilation decreases vascular resistance and arterial __.

pressure

Cardiac output equals heart rate multiplied by __ volume.

stroke

At rest, the main muscles of inspiration are the diaphragm and the external __ muscles.

intercostal

During inspiration the intrapulmonary pressure __, allowing air to enter the lungs.

decreases

Tidal volume is the amount of air inspired or expired during one __ breath.

quiet

Anatomical dead space is the air remaining in the conducting airways that does not participate in __ exchange.

gas

The respiratory rhythm generator is located in the __ (medulla oblongata).

brainstem

Central chemoreceptors are mainly stimulated by an increase in arterial __.

CO₂

The partial pressure of oxygen (pO₂) is the portion of total pressure exerted by __ gas.

oxygen

Most oxygen in blood is transported bound to __ in red blood cells.

hemoglobin

The Bohr effect refers to the decreased affinity of hemoglobin for O₂ in the presence of CO₂ and __ pH.

low (acidic)

Excessive alveolar ventilation lowers arterial pCO₂, producing __.

hypocapnia

The functional unit of the kidney that forms urine is the __.

nephron

Plasma is filtered in the renal __.

glomerulus

Selective filtration occurs because the glomerular membrane has pores that allow passage of water and small __ only.

molecules

The majority of water and solute reabsorption occurs in the __ tubule.

proximal

Antidiuretic hormone (ADH) increases water reabsorption in the __ duct.

collecting

Aldosterone enhances Na⁺ reabsorption and K⁺ secretion in the __ tubule.

distal

In response to hypotension, the kidney releases __ into the bloodstream.

renin

Angiotensin II causes vasoconstriction and stimulates secretion of __.

aldosterone

Atrial natriuretic peptide promotes natriuresis and lowers __ pressure.

blood (arterial)

Urine concentration is mainly regulated in the loop of Henle and the __ duct.

collecting

Blood consists chiefly of plasma and formed elements: erythrocytes, leukocytes and __.

platelets

Hematocrit is the percentage of blood volume occupied by __.

red blood cells

Hemoglobin’s primary function is to transport __ and carbon dioxide.

oxygen

Coagulation is a cascade of reactions leading to formation of a stable __.

clot

Platelets form the platelet plug and release __ of coagulation.

factors

Fibrin stabilizes the clot by forming a __ protein mesh.

fibrous

Vitamin K is essential for hepatic synthesis of several __ factors.

clotting

Antithrombin III functions as a physiological __.

anticoagulant

Fibrinolysis is the process that enzymatically degrades the fibrin __.

clot

The lymphatic system returns excess __ fluid to the bloodstream.

interstitial

ATP serves as the universal cellular __ currency.

energy

Hydrolysis of ATP yields ADP, inorganic phosphate and __.

energy

Enzymes accelerate reactions by lowering the __ energy.

activation

Enzyme specificity arises because the active site is complementary to a single __.

substrate

NAD⁺ and FAD act as electron __ in red-ox reactions.

carriers

Under aerobic conditions, glycolysis ends with formation of __.

pyruvate

The Krebs (citric-acid) cycle takes place in the __ matrix.

mitochondrial

The electron-transport chain generates a proton gradient used for __ synthesis.

ATP

Cyclic AMP (cAMP) frequently acts as an intracellular __ messenger.

second

Ligand binding to a membrane receptor typically activates an intracellular signaling __.

cascade

The four basic tissue types are epithelial, connective, __ and nervous.

muscular

A key feature of epithelial tissue is that it forms protective __ lining internal and external surfaces.

barriers

Connective tissue primarily serves to __ and connect other tissues.

support

Muscle tissue is distinguished by its ability to contract through interactions of actin and __.

myosin

The main function of nervous tissue is rapid __ of electrical impulses.

transmission

The nucleus houses DNA and directs overall __ activities.

cellular

Rough endoplasmic reticulum bears ribosomes and synthesizes proteins, whereas smooth ER produces lipids and performs __.

detoxification

The Golgi apparatus modifies, packages and __ proteins for their destination.

sorts

Mitochondria produce ATP through cellular __.

respiration

Lysosomes contain hydrolytic enzymes for intracellular __ of waste.

digestion