Edexcel IAL Biology — Unit 5: Heart, Brain, and Kidney

Comprehensive vocabulary flashcards covering the circulatory system, nervous coordination, brain anatomy, and renal homeostatic osmoregulation for Edexcel IAL Biology Unit 5.

Septum

The tissue that separates the right and left sides of the heart, preventing the mixing of oxygenated and deoxygenated blood.

Pulmonary Artery

The blood vessel that carries deoxygenated blood from the right ventricle of the heart to the lungs.

Pulmonary Veins

The blood vessels that transport oxygenated blood from the lungs into the left atrium of the heart.

Aorta

The main artery carrying oxygenated blood under high pressure from the left ventricle to the rest of the body.

Vena Cava

The superior and inferior veins that return deoxygenated blood from systemic circulation back to the right atrium.

Tricuspid Valve

The atrioventricular valve located between the right atrium and the right ventricle.

Bicuspid Valve (Mitral Valve)

The atrioventricular valve located between the left atrium and the left ventricle.

Semilunar Valves

Valves located at the base of the pulmonary artery and aorta that prevent backflow of blood into the ventricles during diastole.

Chordae Tendineae

Tendinous cords attached to papillary muscles that prevent the atrioventricular valves from inverting during ventricular contraction.

Atrial Systole

The phase of the cardiac cycle where the atria contract, pressure rises, atrioventricular valves open, and blood flows into the ventricles.

Ventricular Systole

The phase of the cardiac cycle where the ventricles contract, atrioventricular valves snap shut, semilunar valves open, and blood is ejected into the pulmonary artery and aorta.

Diastole

The relaxation phase of the cardiac cycle where heart muscle relaxes, ventricular pressure drops, semilunar valves close, and atria refill with blood.

First Heart Sound

The sound caused by the closure of the atrioventricular valves at the beginning of ventricular systole.

Second Heart Sound

The sound produced by the closure of the semilunar valves at the onset of ventricular diastole.

Coronary Arteries

Arteries branching from the aorta that deliver oxygenated blood and glucose directly to the cardiac muscle tissue.

Sinoatrial Node (SAN)

The primary pacemaker of the heart that spontaneously generates waves of electrical excitation, initiating atrial contraction.

Atrioventricular Node (AVN)

Node of specialized tissue that receives excitation from the SAN, delays it briefly, and conveys it to the bundle of His.

Purkyne Tissue

Specialized conductive fibres that rapidly propagate electrical impulses through ventricular walls, triggering coordinated contraction from the apex upwards.

Cardiac Output

The total volume of blood pumped by one ventricle per minute, calculated as $\text{Cardiac output} = \text{heart rate} \times \text{stroke volume}$.

Stroke Volume

The volume of blood pumped out of the left ventricle during each individual beat.

Atherosclerosis

The accumulation of fatty plaques underneath the arterial endothelium, resulting in luminal narrowing and restricted blood flow.

HDL Cholesterol

High-density lipoprotein that transports cholesterol to the liver for excretion and reduces cardiovascular disease risk.

LDL Cholesterol

Low-density lipoprotein that deposits cholesterol into arterial walls, increasing the risk of cardiovascular disease.

Cerebrum

The main brain region responsible for higher functions including voluntary movement, reasoning, memory, conscious thought, language, and personality.

Cerebellum

Brain structure coordinating motor commands, balance, posture, and fine motor skills.

Medulla Oblongata

The brainstem region containing autonomic regulatory centres that govern involuntary processes like heart rate, breathing rate, and blood pressure.

Hypothalamus

Homeostatic control centre of the brain that regulates temperature, water balance, and hunger while bridging the nervous and endocrine systems.

Pituitary Gland

An endocrine gland that secretes hormones under hypothalamic direction to control other peripheral endocrine glands.

Corpus Callosum

A dense bridge of nerve fibres facilitating interhemispheric communication between the left and right cerebral hemispheres.

Peripheral Nervous System (PNS)

All neural tissue situated outside the brain and spinal cord, linking the central nervous system to effectors and sensory receptors.

Sympathetic Nervous System

Autonomic branch that triggers 'fight or flight' reactions: elevates heart rate, respiratory rate, and blood glucose during stress or exercise.

Parasympathetic Nervous System

Autonomic branch responsible for 'rest and digest' mechanisms that conserve energy, decelerate heart rate, and stimulate digestive processes.

Resting Potential

The stable electrical potential across a resting neuronal membrane, typically around $-70\,\text{mV}$, established by active ion transport and differential membrane permeability.

Depolarisation

The rapid influx of $\text{Na}^+$ ions through voltage-gated channels, shifting the internal membrane charge from negative towards positive.

All-or-Nothing Principle

The physiological rule stating that an action potential fires at full magnitude if threshold is reached, or fails to trigger entirely if it is not.

Refractory Period

A brief recovery interval post-action potential during which a neurone cannot generate another impulse, enforcing unidirectional propagation and maximum firing frequency.

Saltatory Conduction

The rapid jumping of action potentials from one node of Ranvier to the next along a myelinated axon.

Summation

The cumulative integration of post-synaptic potentials, which can be spatial (multiple pre-synaptic neurones) or temporal (rapid firing of a single pre-synaptic neurone).

Reflex Arc

A dedicated, rapid neural circuit mediating involuntary responses: receptor $\rightarrow$ sensory neurone $\rightarrow$ relay neurone $\rightarrow$ motor neurone $\rightarrow$ effector.

Rods

Retinal photoreceptors containing rhodopsin that provide sensitive monochrome vision under low-light conditions.

Cones

Retinal photoreceptors densely packed within the fovea that provide high visual acuity and colour discrimination in bright light.

Habituation

A non-associative learning process characterized by a diminished response to repeated harmless stimuli due to reduced presynaptic neurotransmitter release.

Selective Serotonin Reuptake Inhibitors (SSRIs)

Antidepressant pharmaceuticals that selectively prevent the reabsorption of serotonin into presynaptic terminals, sustaining its concentration within the synaptic cleft.

Nephron

The microscopic structural and functional filtering unit of the vertebrate kidney.

Ultrafiltration

The non-specific filtration process in the glomerulus driven by hydrostatic pressure, forcing fluid, glucose, ions, amino acids, and urea into Bowman's capsule.

Selective Reabsorption

The active and passive recovery of essential solutes (such as all glucose, amino acids, ions, and water) from glomerular filtrate back into peritubular capillaries, primarily in the proximal convoluted tubule.

Loop of Henle

A hairpin-shaped tubular segment that creates an osmotic salt concentration gradient in the renal medulla to facilitate urine concentration.

Countercurrent Multiplier

The functional configuration of the loop of Henle that establishes a hypertonic medullary interstitium, allowing water extraction from the collecting duct.

Antidiuretic Hormone (ADH)

Hormone synthesized in the hypothalamus and released by the posterior pituitary that promotes water conservation by embedding aquaporins into collecting duct and distal tubule cells.

Aldosterone

Mineralocorticoid hormone that enhances sodium ion reabsorption in the distal convoluted tubule and collecting duct, altering blood pressure and secondary fluid retention.

Haemodialysis

A medical intervention that filters blood through an artificial kidney where metabolic wastes diffuse down concentration gradients across semipermeable membranes into dialysis fluid.

Urea

A primary nitrogenous waste metabolite present in systemic blood produced from excess amino acid deamination in the liver.