Cell Physiology and Intercellular Communications - Practice Flashcards

Physiology: study of normal functions of living organisms; how these functions are performed and integrated.

Compartments: Intracellular fluid (ICF) and Extracellular fluid (ECF).
Total body water (TBW): \text{TBW} = 0.60 \times \text{body weight} (60% of body weight).
ICF: \text{ICF} = \frac{2}{3} \text{TBW} = 0.40 \times \text{body weight} (40% of body weight).
ECF: \text{ECF} = \frac{1}{3} \text{TBW} = 0.20 \times \text{body weight} (20% of body weight).
ISF (Interstitial fluid): 0.15 \times \text{body weight}.
Plasma: 0.05 \times \text{body weight}.
Example: TBW for a 70 kg person = 0.60 \times 70 = 42\ \text{kg} = 42\ \text{L}.

Homeostasis: the body's effort to maintain a constant internal environment.
Internal environment is the fluid environment (interstitial fluid).
Factors to regulate within normal range: body temperature (≈ 37^{\circ}\mathrm{C}), water and salts concentrations, etc.

Negative feedback: drives a factor in the opposite direction of the external change; common.
Positive feedback: drives a factor in the same direction as the change; rare.

Membrane components: Proteins (≈ 55\%), Phospholipid bilayer (≈ 25\%), Cholesterol (≈ 13\%), Other lipids (≈ 4\%), Carbohydrates (≈ 3\%).

Proteins act as: Adhesion molecules, Enzymes, Antigens, Receptors, Ion channels, Carriers for facilitated diffusion, Pumps for active transport.

Osmosis: passive movement of water from low solute concentration area to higher solute concentration area.
Simple (passive) diffusion: passive movement of small molecules (e.g., O2 & CO2, some ions) from higher to lower concentration through lipid bilayer or protein channels.
Facilitated diffusion: passive movement of larger molecules (e.g., glucose & amino acids) from higher to lower concentration via carrier proteins.
Active transport: active movement of specific ions (e.g., Na+, K+, Ca++) from lower to higher concentration; requires energy (ATP).\n - Na+/K+ pump: extrudes 3 Na+ from inside to outside; 2 K+ from outside to inside.

Cells communicate via chemical messengers.
Gap junctions: channels between cells; some messengers move from cell to cell via gap junctions without entering the ECF.

Neurotransmitters are released at synaptic junctions from nerve cells and act across a narrow synaptic cleft on a postsynaptic cell.

Paracrine: products diffuse in the ECF to affect neighboring cells (A = autocrine; P = paracrine).
Endocrine: hormones and growth factors reach cells via circulating blood.