Fluid Movement and Extracellular Volume

Fluid Movement

• Decreased extracellular fluid (ECF) volume increases fluid movement out of a capillary into the interstitium.
• Increased capillary permeability to protein increases fluid movement out of a capillary into the interstitium.
• Decreased capillary hydrostatic pressure increases fluid movement out of a capillary into the interstitium.
• Increased interstitial fluid hydrostatic pressure increases fluid movement out of a capillary into the interstitium.
• Decreased plasma colloid osmotic pressure increases fluid movement out of a capillary into the interstitium.

Extracellular Fluid Volume

• Increased extracellular fluid volume can result from excessive sweating, blood loss, or intravenous infusion of a hypertonic solution.
• Increased extracellular fluid volume results in a decreased hematocrit.

Isotonic Overhydration

• Isotonic overhydration results in increased extracellular fluid (ECF) volume.
• Increased extracellular fluid volume can result from excessive sweating.
• Blood loss can result in increased extracellular fluid volume.

Plasma

• Components of plasma include fibrinogen, bicarbonate ions (HCO3-), albumin, and erythrocytes.

Hemoglobin

• Hemoglobin transports oxygen.

Red Blood Cells

• Red blood cells are produced in the bone marrow.
• Red blood cells are not nucleated.
• Red blood cells are not components of the immune system.
• Red blood cells transport carbon dioxide.
• Red blood cells hemolyse when suspended in a 0.9% sodium chloride (NaCl) solution.

Hematocrit

• Dehydration increases hematocrit.
• A person living at high altitude compared to a person living at sea level has an increased hematocrit.
• An incompatible blood transfusion increases hematocrit.
• Erythropoietin increases hematocrit.
• Folate deficiency decreases hematocrit.

Iron Deficiency Anemia

• Chronic iron deficiency anemia results in hypochromic erythrocytes.
• Chronic iron deficiency anemia results in a decreased hematocrit.
• Chronic iron deficiency anemia results in fewer circulating reticulocytes.

Na+/K+ ATPase Pump

• The Na+/K+ ATPase pump transports sodium ions (Na+) against their concentration gradient.
• The Na+/K+ ATPase pump transports potassium ions (K+) against their concentration gradient.
• The Na+/K+ ATPase pump maintains the resting membrane potential.
• The Na+/K+ ATPase pump requires energy.

Depolarization Phase of Neuronal Action Potential

• During the depolarization phase of a neuronal action potential, sodium ions (Na+) diffuse into the cell.
• During the depolarization phase of a neuronal action potential, the voltage-gated sodium (Na+) channel’s inactivation gates are closed.
• During the depolarization phase of a neuronal action potential, the membrane potential becomes positive.

Neuronal Conduction Velocity

• Neuronal conduction velocity is slower in C-class fibers than in A-class fibers.
• Neuronal conduction velocity is slower unmyelinated neurons than in myelinated neurons.
• Neuronal conduction velocity is slower in neurons with a narrow diameter than in neurons with a wide diameter.
• Neuronal conduction velocity is slower at low temperatures than at high temperatures.

Synapses

• In a chemical synapse, neurotransmitter release occurs via exocytosis.
• In a chemical synapse, neurotransmitters bind to metabotropic receptors, which stimulate post-synaptic intracellular second messengers.
• In a chemical synapse, neurotransmitters are degraded by enzymes.

Acetylcholine

• Acetylcholine is broken down by acetylcholine esterase.
• Acetylcholine release is blocked by botulinum toxin.
• Acetylcholine is a muscarinic agonist.

Skeletal Muscle Contraction

• Antibodies binding to nicotinic receptors inhibit skeletal muscle contraction.
• Decreased acetylcholinesterase activity inhibits skeletal muscle contraction.
• Adrenergic agonists inhibit skeletal muscle contraction.
• Muscarinic antagonists inhibit skeletal muscle contraction.
• Inhibition of synapsin-1 activity inhibits skeletal muscle contraction.

Sympathetic Nervous System

• The sympathetic nervous system contains postganglionic cholinergic neurons.
• The sympathetic nervous system has a higher ratio of preganglionic to postganglionic neurons (high divergence) than the parasympathetic nervous system.

Parasympathetic Nervous System

• The parasympathetic nervous system contains terminal ganglia.
• The parasympathetic nervous system activation causes urine retention.

Cyclic Adenosine Monophosphate (cAMP) Second Messenger

• cAMP is activated by G-protein-coupled receptor activation.
• cAMP is inhibited by the action of phosphodiesterase.
• cAMP is stimulated by β-adrenergic receptor activation.
• cAMP is involved in smooth muscle release of endoplasmic reticulum calcium.

Post-synaptic Membranes

• An increase in the conductance of the post-synaptic membrane to potassium (K+) ions results in an inhibitory post-synaptic potential (IPSP).
• An increase in the conductance of the post-synaptic membrane to chloride (Cl-) ions results in an inhibitory post-synaptic potential (IPSP).

Action Potentials

• The slow closing of voltage-gated potassium (K+) channels results in hyperpolarization.
• The plateau phase of a cardiomyocyte action potential results from calcium ion (Ca2+) influx.

Neurotransmitters

• Amino acid neurotransmitters include glutamate.

Autonomic Nervous System

• Autonomic preganglionic fibers are myelinated.
• Somatic motor neurons are efferent fibers.
• The vagus nerve (cranial nerve X) carries parasympathetic nerve fibers.
• Sympathetic and parasympathetic effects on the heart are antagonistic.
• Intracellular calcium is required for smooth muscle contraction.