General Physio Flashcards
(21 cards)
Homeostasis
Maintenance of relatively stable internal environment (extracellular fluid) within physiological range
It involves :
negative feedback mechanisms (e.g., temperature regulation) & positive feedback mechanisms (e.g., blood clotting, labor contractions).
(Guyton 4th SA Ed.)
Role of the hypothalamus in homeostasis
Hypothalamus regulates temp. , hunger, thirst & hormonal balance through neural & endocrine control.
(Guyton 4th SA Ed.)
How does the body regulate temperature?
Through vasodilation, sweating (heat loss), vasoconstriction, and shivering (heat conservation).
(Guyton 4th SA Ed.)
Different types of membrane transport?
Passive Transport: Simple diffusion, facilitated diffusion, osmosis (no ATP required).
Active Transport: Primary (Na+/K+ pump) & secondary (co-transport & counter-transport).
Vesicular Transport: Endocytosis and exocytosis.
(Guyton 4th SA Ed.)
What factors influence the rate of diffusion across the cell membrane?
Conc. gradient, membrane permeability, surface area, molecular size & temp.
(Guyton 4th SA Ed.)
Function of aquaporins
Aquaporins are water channel proteins that facilitate rapid water movement across membranes.
(Guyton 4th SA Ed.)
What maintains the resting membrane potential (RMP)?
RMP is maintained by the Na+/K+ ATPase pump (3 Na+ out, 2 K+ in),
selective permeability of K+ & fixed anions inside the cell. The typical RMP of a neuron is -70 mV.
(Guyton 4th SA Ed.)
Phases of an action potential?
Depolarization (Na+ influx).
Repolarization (K+ efflux).
Hyperpolarization (K+ channels remain open briefly).
(Guyton 4th SA Ed.)
What is the absolute refractory period?
The period during which no new action potential can be generated, regardless of stimulus strength.
(Guyton 4th SA Ed.)
How is body fluid distributed?
Total body water (~60% of body weight) is divided into:
Intracellular fluid (ICF): ~40% body weight.
Extracellular fluid (ECF): ~20% body weight (includes interstitial fluid & plasma).
(Guyton 4th SA Ed.)
What are the main solutes in ICF and ECF?
ICF: High K+, Mg2+, and phosphate.
ECF: High Na+, Cl-, and bicarbonate.
(Guyton 4th SA Ed.)
Role of albumin in fluid balance?
Albumin maintains oncotic pressure and prevents excessive fluid leakage from capillaries.
(Guyton 4th SA Ed.)
Primary buffer systems in the body?
Bicarbonate buffer system (HCO3-/H2CO3) – major ECF buffer.
Protein buffer system (Hemoglobin & plasma proteins).
Phosphate buffer system – important in ICF & urine.
Respiratory & renal mechanisms help maintain pH.
(LPR Fundamentals 9th Ed.)
How does the respiratory system regulate acid-base balance?
By controlling CO2 levels. Increased CO2 lowers pH (respiratory acidosis), while decreased CO2 raises pH (respiratory alkalosis).
(LPR Fundamentals 9th Ed.)
Metabolic acidosis
A condition characterized by decreased bicarbonate (HCO3-) levels, leading to lowered blood pH.
(LPR Fundamentals 9th Ed.)
What factors affect enzyme activity?
Temperature & pH (optimum conditions required).
Substrate concentration (Michaelis-Menten kinetics).
Enzyme inhibitors: Competitive & non-competitive.
LPR Fundamentals 9th Ed.
Role of ATP in metabolism?
ATP provides energy for cellular reactions, including active transport, biosynthesis, and muscle contraction.
LPR Fundamentals 9th Ed.
How is ATP synthesized?
ATP is synthesized via glycolysis, Krebs cycle & oxidative phosphorylation.
LPR Fundamentals 9th Ed.
How do the sympathetic and parasympathetic nervous systems differ?
Sympathetic: “Fight or flight,” increases HR, BP, bronchodilation.
Parasympathetic: “Rest and digest,” decreases HR, increases digestion.
Neurotransmitters: Sympathetic (norepinephrine), Parasympathetic (acetylcholine).
Guyton 4th SA Ed.
What are the effects of the autonomic nervous system on the eye?
Sympathetic: Pupil dilation (mydriasis).
Parasympathetic: Pupil constriction (miosis).
Guyton 4th SA Ed.
What is the baroreceptor reflex?
A mechanism that helps regulate blood pressure by adjusting heart rate and vascular tone.
Guyton 4th SA Ed.
