BIOL121 Human Biological Science 1 Practice Flashcards

Comprehensive vocabulary flashcards covering the core physiological systems, microbiological concepts, pharmacology principles, and biochemical processes presented in Topics 1 to 9 of BIOL121.

Anatomical position

The standard reference position where the body is standing upright, facing forward, with arms at the sides and palms facing forward; used so everyone describes anatomical orientation identically.

Phospholipid bilayer

A two-layered cell membrane framework with hydrophilic (water-loving) heads facing outward toward water and hydrophobic (water-fearing) fatty acid tails facing inward, stabilized by cholesterol.

Facilitated diffusion

A passive transport process where substances move down their concentration gradient through a membrane via a carrier or channel protein (such as glucose entering via GLUT transporters) without using $ATP$.

Osmosis

The net movement of water across a semipermeable membrane toward the region of higher solute concentration.

Crenation

The shrinking or shrivelling of a cell that occurs when it is placed in a hypertonic solution (such as $1.5\%$ saline) because water leaves the cell.

Haemolysis

The swelling and bursting of red blood cells caused by water entering down its concentration gradient when cells are placed in a hypotonic solution (such as distilled or sterile pure water).

Serous membrane

A double-layered membrane lining closed body cavities (pleura, pericardium, peritoneum) that secretes lubricating fluid to reduce friction.

Negative feedback

The primary homeostatic control mechanism where an effector responds to reverse or oppose a detected change, restoring the variable back to its set point (e.g., body temperature, blood glucose, blood pressure).

Positive feedback

A homeostatic control mechanism that amplifies and reinforces a change until an end point is reached (examples include childbirth contractions via oxytocin, blood clotting, and lactation milk let-down).

Opportunistic pathogens

Normal flora that typically live on the skin, mouth, gut, or urogenital tract without causing disease, but cause infection if host immunity drops or if they access an abnormal site.

Disinfection

A microbial control process that kills most harmful microbes on inanimate objects, distinct from sterilization (which kills or removes all microbes) and sanitization (which reduces microbial counts to safe levels).

Innate immunity

Non-specific body defences present from birth that provide an immediate response to all threats without immunological memory.

Adaptive immunity

Specific body defences that develop after antigen exposure, exhibiting specificity, versatility, memory (faster and stronger second response), and self-tolerance.

Antibody-mediated (humoral) immunity

An adaptive immune branch where $B$ cells differentiate into plasma cells that secrete antibodies into blood and lymph; most effective against extracellular bacteria, toxins, and viruses outside host cells.

Cell-mediated immunity

An adaptive immune branch driven by $T$ cells, in which cytotoxic $T$ cells directly destroy infected host cells, cancer cells, and transplanted tissue.

Pharmacokinetics

The branch of pharmacology describing what the body does to a drug, consisting of absorption, distribution, metabolism (mostly liver), and excretion (mostly kidney).

First-pass effect

The hepatic metabolism of orally administered drugs absorbed from the small intestine via the hepatic portal vein before reaching systemic circulation, which decreases overall drug bioavailability.

Bioavailability

The fraction of an administered dose of unchanged drug that reaches the systemic circulation ($100\%$ for intravenous administration).

Drug half-life

The time required for the blood concentration of a drug to reduce by half; steady state is typically reached (or cleared) in about $4\text{--}5$ half-lives.

Resting membrane potential

The electrical potential across a non-excited neuronal membrane (approximately $-70\,\text{mV}$), characterized by a negative inside with more $\text{K}^+$ inside and more $\text{Na}^+$ outside, maintained by the $\text{Na}^+/\text{K}^+$ pump.

Depolarisation

The phase of an action potential when a stimulus reaches threshold, triggering voltage-gated $\text{Na}^+$ channels to open so that $\text{Na}^+$ rushes into the cell, making the interior positive.

Repolarisation

The phase of an action potential where $\text{Na}^+$ channels close and voltage-gated $\text{K}^+$ channels open, allowing $\text{K}^+$ to leave the cell so the interior becomes negative again.

Synapse

The junction between a neuron and another neuron or effector cell, across which an action potential induces $\text{Ca}^{2+}$ influx to release neurotransmitters from vesicles across the synaptic cleft.

Sympathetic nervous system

The 'fight or flight' division of the autonomic nervous system that increases heart rate, blood pressure, breathing rate, and blood glucose, dilates airways and pupils, and causes vasoconstriction in the gut and skin.

Parasympathetic nervous system

The 'rest and digest' division of the autonomic nervous system (acting largely via the vagus nerve) that slows heart rate, promotes digestion, and stimulates bladder emptying.

Anterior pituitary

The glandular lobe of the pituitary gland controlled by hypothalamic releasing hormones via a portal blood system; synthesizes and releases its own hormones (including $TSH$, $FSH$, $LH$, and prolactin).

Posterior pituitary

The neurohypophysis, which stores and secretes hormones ($ADH$ and oxytocin) that are synthesized in the hypothalamus and transported down axons for release upon nerve impulses.

Parathyroid hormone (PTH)

A hormone released by the parathyroid glands in response to low blood $\text{Ca}^{2+}$ that raises blood calcium by activating osteoclasts to release $\text{Ca}^{2+}$ from bone, retaining $\text{Ca}^{2+}$ in the kidneys, and activating vitamin $D$.

Epiphyseal plate

A layer of hyaline cartilage located in the metaphysis of growing long bones that allows bone lengthening, which eventually fuses into bone tissue when growth ceases.

Osteoblasts

Bone cells responsible for building and depositing new bone matrix.

Osteoclasts

Bone cells that resorb and break down old bone matrix, releasing minerals including calcium into the blood.

Synovial joint

A freely movable joint featuring a joint capsule, synovial membrane, joint cavity containing lubricating synovial fluid, articular cartilage, and stabilizing ligaments.

Sarcomere

The functional contractile unit of a muscle myofibril, bordered by Z-lines and composed of overlapping thin actin and thick myosin filaments.

Sarcoplasmic reticulum

A specialized network of smooth endoplasmic reticulum within muscle fibres that stores and releases $\text{Ca}^{2+}$ to trigger actin-myosin cross-bridge cycling.

Systole

The mechanical phase of the cardiac cycle when the ventricles contract, causing ventricular pressure to exceed arterial pressure and ejecting blood into the aorta and pulmonary trunk.

Diastole

The mechanical relaxation phase of the cardiac cycle when the ventricles relax and fill with blood as atrial pressure exceeds ventricular pressure.

Sinoatrial (SA) node

The primary physiological pacemaker of the heart, located in the right atrium, which initiates the electrical impulses that trigger atrial depolarization.

Mean Arterial Pressure (MAP)

The average driving blood pressure in the arterial system, calculated as $\text{MAP} = \text{diastolic} + \frac{1}{3}(\text{pulse pressure})$ or $\text{MAP} = \text{CO} \times \text{TPR}$.

Baroreceptor reflex

A short-term neural homeostatic mechanism in which stretch receptors in the carotid sinus and aortic arch detect blood pressure changes and signal the medulla to adjust sympathetic and parasympathetic outputs.

Extrinsic pathway (coagulation)

A rapid clotting cascade pathway triggered by damage to tissues outside the blood vessel, initiating coagulation via the release of tissue factor.

Fibrinolysis

The enzymatic clot-removal process in which plasmin breaks down and digests insoluble fibrin threads once vascular healing has occurred.

Universal blood donor

Blood Group $O$, characterized by red blood cells lacking both $A$ and $B$ surface antigens, which can be safely donated to all ABO recipients because it does not trigger anti-A or anti-B recipient antibodies.

External respiration

The exchange of gases across the alveolar-capillary membrane between alveolar air ($\text{PO}_2 \approx 100$, $\text{PCO}_2 \approx 40$) and pulmonary blood ($\text{PO}_2 \approx 40$, $\text{PCO}_2 \approx 45$).

Internal respiration

The gas exchange process occurring at systemic tissues between capillary blood ($\text{PO}_2 \approx 100$) and surrounding tissue cells ($\text{PO}_2 \approx 40$, $\text{PCO}_2 \approx 45$).

Surfactant

A lipid-rich secretion produced in the alveoli that reduces the surface tension of alveolar fluid, preventing the collapse of alveoli during exhalation.

Vital capacity

The maximum volume of air that can be exhaled following a maximal inhalation, equal to $\text{TV} + \text{IRV} + \text{ERV}$ (typically about $4800\,\text{mL}$).

Residual volume

The volume of air remaining in the lungs and airways after a maximal forced exhalation (typically about $1200\,\text{mL}$) that prevents alveolar collapse and cannot be exhaled.

Glomerular Filtration Rate (GFR)

The volume of filtrate formed by both kidneys per minute (typically approximately $125\,\text{mL/min}$), driven by a net filtration pressure of $10\,\text{mmHg}$ and serving as a key measure of kidney function.

Obligatory water reabsorption

The non-regulated, osmotic movement of water that obligatorily follows solute reabsorption, occurring primarily in the proximal convoluted tubule (\approx 60\%+\) and the descending loop of Henle (\approx 15\%\).

Renin-Angiotensin-Aldosterone System (RAAS)

A hormonal cascade triggered by low blood pressure or volume where the kidneys secrete renin to produce angiotensin $I$, converted by $ACE$ to angiotensin $II$, causing vasoconstriction, aldosterone release, $ADH$ release, and thirst to elevate blood pressure.

Atrial Natriuretic Peptide (ANP)

A hormone secreted by atrial myocytes in response to high blood volume or atrial stretch that promotes renal excretion of $\text{Na}^+$ and water, opposes $RAAS$, and decreases blood volume and blood pressure.

Detrusor muscle

The smooth muscle layer of the urinary bladder wall that relaxes under sympathetic stimulation to store urine and contracts under parasympathetic stimulation to empty the bladder.

Peristalsis

Involuntary, alternating contractions and relaxations of circular and longitudinal muscularis layers in the gastrointestinal tract that push food boluses and chyme forward.

Pepsin

An active gastric protease formed when chief cell pepsinogen is activated by hydrochloric acid ($HCl$), functioning at acidic $\text{pH } 1.5\text{--}3.5$ to break proteins down into polypeptides.

Bile

A substance produced continuously by the liver and stored/concentrated in the gallbladder that physically emulsifies dietary fats into small droplets to increase the surface area for pancreatic lipase activity.

Gluconeogenesis

An anabolic metabolic pathway occurring primarily in the liver that synthesizes new glucose molecules from non-carbohydrate precursors during the post-absorptive or fasting state.

Absorptive (fed) state

The metabolic state during and immediately following a meal when nutrients are being absorbed, driven by insulin to stimulate glucose uptake, glycogenesis, and lipogenesis.

Post-absorptive (fasting) state

The metabolic state between meals when the GI tract is empty, driven by glucagon to promote glycogenolysis, lipolysis, and gluconeogenesis to maintain blood glucose for the brain.

Human Chorionic Gonadotropin (hCG)

A hormone produced by the early embryo and developing placenta that maintains the corpus luteum, ensuring continuous progesterone and oestrogen secretion to preserve the uterine endometrium.

Corpus luteum

The endocrine structure formed from a ruptured ovarian follicle during the luteal phase (days $\sim 15\text{--}28$) that secretes progesterone and oestrogen to prepare and maintain the endometrium.

Combined oral contraceptive pill

A hormonal medication containing oestrogen and progestin that provides negative feedback to inhibit hypothalamic $GnRH$ and pituitary $FSH$ and $LH$, thereby preventing follicle maturation and ovulation.

Prolactin

An anterior pituitary hormone that stimulates milk production in the alveoli of the mammary glands following birth.