bio125 Flashcards
(193 cards)
1
Q
Central Nervous System (CNS)
A
brain and spinal cord.
2
Q
Peripheral Nervous System (PNS)
A
cranial and peripheral nerves.
3
Q
Sensory function of the nervous system
A
detect internal/external changes.
4
Q
Integrative function of the nervous system
A
analyse and decide responses.
5
Q
Motor function of the nervous system
A
initiate movement or glandular secretion.
6
Q
Sagittal plane
A
divides left and right.
7
Q
Coronal plane
A
divides front and back.
8
Q
Transverse plane
A
divides top and bottom.
9
Q
Superior
A
above.
10
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Inferior
A
below.
11
Q
Anterior/Ventral
A
front.
12
Q
Posterior/Dorsal
A
back.
13
Q
Medial
A
toward midline.
14
Q
Lateral
A
away from midline.
15
Q
Cerebrum
A
largest part; cortex + subcortical areas.
16
Q
Cerebellum
A
balance and coordination.
17
Q
Brainstem
A
involuntary control (e.g., breathing, heart rate).
18
Q
Frontal lobe
A
decision making, voluntary movement.
19
Q
Parietal lobe
A
integrates sensory information, motor coordination.
20
Q
Temporal lobe
A
hearing, speech, object recognition, emotion.
21
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Occipital lobe
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visual processing.
22
Q
Hypothalamus
A
involved in memory, emotion, motor control, and sensory processing.
23
Q
Amygdala
A
involved in memory, emotion, motor control, and sensory processing.
24
Q
Hippocampus
A
involved in memory, emotion, motor control, and sensory processing.
25
Thalamus
involved in memory, emotion, motor control, and sensory processing.
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Basal ganglia
involved in memory, emotion, motor control, and sensory processing.
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Colliculi
direct eye movement.
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Tegmentum
movement coordination, alertness.
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Cerebral peduncle
control of ocular muscles.
30
Cervical spinal cord
critical link between CNS and PNS; innervates body regions.
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Thoracic spinal cord
critical link between CNS and PNS; innervates body regions.
32
Lumbar spinal cord
critical link between CNS and PNS; innervates body regions.
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Sacral spinal cord
critical link between CNS and PNS; innervates body regions.
34
Coccygeal spinal cord
critical link between CNS and PNS; innervates body regions.
35
Somatic division of PNS
voluntary control of skeletal muscle.
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Autonomic division of PNS
involuntary control (sympathetic = fight or flight, parasympathetic = rest and digest).
37
Enteric division of PNS
controls gut movement and secretion.
38
Afferent pathways
sensory input to CNS ('Arriving').
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Efferent pathways
motor output from CNS ('Exiting').
40
Reflex arc of the knee-jerk response
Sensory afferents → spinal cord dorsal column → interneurons → efferent motor neurons → muscle contraction. Occurs without brain input.
41
Neurons
conduct electrical signals.
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Microglia
immune surveillance and response.
43
Astrocytes
structural and metabolic support; form glial scars.
44
Oligodendrocytes
form myelin sheaths (PNS = Schwann cells).
45
White matter
myelinated axon bundles; fast conduction (up to 150 m/s).
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Grey matter
unmyelinated cell bodies.
47
Cerebrospinal fluid (CSF)
provides brain buoyancy, cushions, waste removal (produced by choroid plexus).
48
Blood-brain barrier
endothelial tight junctions selectively protect the brain from harmful blood substances.
49
Resting membrane potential of a neuron
Combination of K⁺ diffusion out via leaky channels and the Na⁺/K⁺ ATPase pump which actively transports ions (3 Na⁺ out, 2 K⁺ in). Resulting resting potential ≈ -70 mV (inside negative).
50
Forces driving ion movement across membranes
Chemical gradient: ions move from high to low concentration. Electrical gradient: oppositely charged ions are attracted across the membrane. Combined: electrochemical driving force.
51
Electrochemical driving force
Combined driving force for ion movement across a membrane.
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Gated channels
Ion channels that open in response to ligands, voltage, or mechanical stimuli.
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Leak channels
Ion channels that are always open and allow passive ion movement.
54
Relative ion concentrations in neurons at rest
Na⁺: ~10x higher outside. K⁺: ~15x higher inside.
55
Potassium movement and membrane potential
K⁺ moves out of the cell via leaky K⁺ channels, making inside negative.
56
Na⁺/K⁺ ATPase pump
Moves 3 Na⁺ out and 2 K⁺ in per cycle, maintaining ion gradients.
57
Resting membrane potential
The voltage difference across a neuron's plasma membrane at rest (~ -70 mV).
58
Opening of sodium channels
Na⁺ moves into the neuron down both chemical and electrical gradients.
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Equilibrium potential
The membrane potential at which there is no net ion movement for a specific ion.
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Nernst equation
E = 61 log(C₀/Cᵢ) where E = equilibrium potential (mV), z = charge of ion.
61
Triggering an action potential
Neuron is depolarised to threshold (~ -55 mV), opening voltage-gated Na⁺ channels.
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Phases of an action potential
Depolarisation, repolarisation, and hyperpolarisation of the membrane.
63
Refractory period
Time after action potential when neuron cannot fire another spike.
64
Hyperpolarisation
Membrane potential becomes more negative than -70 mV due to K⁺ leaving.
65
Voltage-gated ion channels
Channels that open in response to changes in membrane voltage.
66
Types of synapses
Electrical synapses: direct ion flow; chemical synapses: neurotransmitters cross cleft.
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Triggering neurotransmitter release
An action potential opens voltage-gated Ca²⁺ channels, causing neurotransmitter release.
68
Quantum in synaptic transmission
The fixed amount of neurotransmitter released by the fusion of one synaptic vesicle.
69
Excitatory postsynaptic potentials (EPSP)
Neurotransmitter binding causes Na⁺ influx, depolarising the membrane.
70
Inhibitory postsynaptic potentials (IPSP)
Neurotransmitter causes K⁺ efflux or Cl⁻ influx, hyperpolarising the membrane.
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Termination of neurotransmitter action
By enzymatic degradation or reuptake into the presynaptic neuron or nearby glia.
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Four criteria to define a neurotransmitter
Synthesised by neurons. Present at presynaptic terminals. Mimics natural action when applied exogenously. Has a removal mechanism from the synaptic cleft.
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Ionotropic receptors
Ligand-gated ion channels. Open directly when neurotransmitter binds. Examples: nicotinic acetylcholine receptor, GABA A receptor.
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Metabotropic receptors
G-protein coupled receptors (GPCRs). Binding of neurotransmitter activates G-proteins, which then regulate ion channels or enzymes indirectly. Slower response than ionotropic receptors.
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Structure of ionotropic receptors
Composed of 4-5 subunits around a central pore. Pore remains closed until neurotransmitter binding causes a conformational change allowing ion flow.
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Agonist in receptor pharmacology
Activates receptor to mimic natural neurotransmitter action.
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Antagonist in receptor pharmacology
Binds receptor but blocks activation, preventing the normal neurotransmitter from acting.
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Three main classes of neurotransmitters
Biogenic amines (e.g., dopamine, serotonin), Amino acids (e.g., glutamate, GABA), Peptides (e.g., endorphins, enkephalins).
79
Synthesis and degradation of acetylcholine (ACh)
Synthesised from choline by choline acetyltransferase. Degraded in the synaptic cleft by acetylcholinesterase (AChE).
80
Two main types of acetylcholine receptors
Nicotinic (neuromuscular junction, brain, autonomic nerves), Muscarinic (smooth muscle, glands, brain).
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Agonists and antagonists of cholinergic receptors
Nicotinic: agonist = nicotine, antagonist = curare; Muscarinic: agonist = muscarine, antagonist = atropine.
82
Acetylcholine and Alzheimer's disease
Cholinergic neurons die early → memory and attention deficits. Treatment: AChE inhibitors (donepezil, rivastigmine, galantamine).
83
Synthesis and breakdown of catecholamines
Synthesised from tyrosine → L-DOPA → dopamine → noradrenaline → adrenaline. Broken down by MAO and COMT.
84
Pathology and treatment of Parkinson's disease
Loss of dopaminergic neurons in substantia nigra. Treatment: L-DOPA + Dopa decarboxylase inhibitors, plus COMT/MAO-B inhibitors.
85
Synthesis and degradation of serotonin (5-HT)
Synthesised from tryptophan → 5-HTP → serotonin. Degraded by MAO and aldehyde dehydrogenase to 5-HIAA.
86
Key neurotransmitter receptors for glutamate and GABA
Glutamate: NMDA, AMPA, kainate, mGluRs; GABA: GABA A (ionotropic), GABA B (metabotropic).
87
Astrocytes regulation of glutamate and GABA levels
Uptake glutamate via EAAT transporters. Uptake GABA via GAT transporters. Convert both to glutamine for recycling to neurons.
88
Two families of dopamine receptors
D1-like (D1, D5): stimulate adenylate cyclase; D2-like (D2, D3, D4): inhibit adenylate cyclase.
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Serotonin reuptake and SSRIs
Serotonin Transporter (SERT) reabsorbs serotonin from synaptic cleft. SSRIs (e.g., fluoxetine, citalopram) block reuptake → increase synaptic serotonin.
90
Difference between peptide neurotransmitters and classical neurotransmitters
Peptide neurotransmitters differ from classical neurotransmitters in their structure and function.
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Synthesised as large precursor proteins
Cleaved into active peptides
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Examples of neuropeptides
Substance P, neuropeptide Y, enkephalins, endorphins
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Co-release with classical neurotransmitters
Slower but longer-lasting effects
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Tyrosine hydroxylase
Tyrosine → L-DOPA
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Aromatic L-amino acid decarboxylase
L-DOPA → dopamine
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Dopamine β-hydroxylase
Dopamine → noradrenaline
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PNMT
Noradrenaline → adrenaline
98
Glutamate
Major excitatory neurotransmitter; promotes depolarisation
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GABA
Major inhibitory neurotransmitter; promotes hyperpolarisation
100
Four basic processes of the digestive system
Digestion, Absorption, Motility, Secretion
101
Main organs of the digestive system
Mouth, pharynx, oesophagus, stomach, small intestine, colon, rectum, anus
102
Accessory organs of the digestive system
Salivary glands, pancreas, liver, gallbladder
103
General structure of the gastrointestinal (GI) tract
Mucosa, Submucosa, Muscularis, Serosa
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Key cell types of the mucosal epithelium
Absorptive cells, Exocrine cells, Goblet cells, Endocrine cells
105
Function of the enteric nervous system
Controls gut motility, secretion, and blood flow
106
Saliva production per day
0.75-1.5 litres/day
107
Main components of saliva
Salivary α-amylase, lingual lipase, mucus, lysozyme, lactoferrin, buffers
108
Functions of saliva
Lubrication, Dilution of harmful substances, Antibacterial action, Taste facilitation, Cleaning teeth, Fluoride and calcium uptake into teeth
109
Structure and function of the oesophagus
Muscular tube (~25 cm) with upper 1/3 skeletal muscle and lower 2/3 smooth muscle
110
Main secretions of the stomach
HCl and intrinsic factor from parietal cells, pepsinogen from chief cells, mucus from neck cells
111
HCl secretion by parietal cells
CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻; H⁺ pumped into lumen in exchange for K⁺; Cl⁻ enters lumen with H⁺ to form HCl
112
Activation of pepsinogen
Converted to pepsin by HCl; pepsin removes internal peptide bonds of proteins (endopeptidase), active at pH 2
113
Key digestive zymogens and their active forms
Pepsinogen → pepsin; Chymotrypsinogen → chymotrypsin; Trypsinogen → trypsin; Procarboxypeptidase → carboxypeptidase; Proelastase → elastase
114
Role of the duodenum in digestion
First part of small intestine (first 30 cm); receives chyme from stomach, enzymes from pancreas, bile from liver/gallbladder; major site of nutrient digestion
115
Histology and function of the small intestine
Surface area ~300 m² (villi + microvilli); functions include digestion and absorption of nutrients, water, vitamins, minerals; Crypts of Lieberkühn secrete bicarbonate-rich fluid to neutralise stomach acid
116
Key features and functions of the colon
Includes cecum, rectum, anal canal, appendix; no villi but crypts of Lieberkühn present; main site of water absorption; hosts large population of commensal microflora
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Exocrine function of pancreas
Secretion of digestive enzymes and bicarbonate into the duodenum via pancreatic ducts.
118
Endocrine function of pancreas
Secretion of hormones (e.g., insulin) by Islets of Langerhans into the bloodstream.
119
Enzymes produced by pancreatic acinar cells
Proteases: trypsin, chymotrypsin, elastase, carboxypeptidase (as zymogens); Amylase: digests starch; Lipase: digests fats; DNase/RNase: digest nucleic acids.
120
Function of pancreatic bicarbonate
Secreted by duct cells to neutralise gastric acid in the duodenum and creates an optimal pH for pancreatic enzymes to function.
121
Islets of Langerhans
Clusters of endocrine cells in the pancreas that secrete insulin (β-cells) and glucagon (α-cells) to regulate blood glucose levels.
122
Processing of insulin from proinsulin
Proinsulin (86 amino acids) is cleaved into A-chain (21 aa), B-chain (30 aa), and C-peptide (31 aa, removed).
123
Type 1 diabetes
Autoimmune destruction of insulin-producing β-cells; early onset; insulin dependent.
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Type 2 diabetes
Insulin resistance followed by secretion decline; linked to obesity; may be managed with lifestyle and drugs.
125
Lifestyle changes and Type 2 diabetes
Diet and exercise can prevent or delay Type 2 onset, reducing insulin resistance and improving blood glucose regulation.
126
Absorption in the small intestine
Mainly occurs in the duodenum and jejunum; nutrients enter capillaries of villi and travel via hepatic portal vein to the liver.
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Absorption of lipids in the intestine
Emulsified by bile salts, digested by lipase, absorbed as fatty acids and monoglycerides, and reassembled into chylomicrons.
128
Chylomicrons
Lipoprotein particles carrying triglycerides, released from enterocytes into lacteals, lymphatic system, thoracic duct, and left subclavian vein.
129
Role of the lymphatic system in digestion
Transports absorbed lipids and fat-soluble vitamins via chylomicrons and returns interstitial fluid to blood while supporting immune defence.
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Hepatic portal system
Nutrients (except fats) travel from gut to mesenteric veins, hepatic portal vein, and then to the liver to be processed and detoxified before systemic circulation.
131
Dominant bacterial phyla in human gut microbiota
Bacteroidetes and Firmicutes; also present: Actinobacteria and Proteobacteria.
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Gut microbiota support for digestion and health
Ferments fibre, produces SCFAs like butyrate, and synthesises Vitamin K, folate, thiamine, biotin, riboflavin, and pantothenic acid.
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Gut microbiota influence on obesity and metabolism
Regulates FIAF (fasting-induced adipocyte factor), which affects fat storage; microbial composition is linked to metabolic syndrome and obesity.
134
"What are the main functions of the cardiovascular system?"
"To deliver oxygen and nutrients, remove waste, maintain blood pressure, regulate body temperature, and support immune function."
135
"What are the four chambers and four valves of the heart?"
"Chambers: Right atrium, Right ventricle, Left atrium, Left ventricle. Valves: Tricuspid (R AV), Bicuspid/Mitral (L AV), Aortic semilunar, Pulmonary semilunar."
136
"What is the function of atrioventricular (AV) valves and semilunar valves?"
"AV valves prevent backflow from ventricles to atria; Semilunar valves prevent backflow from arteries into ventricles."
137
"What is pericardium and its function?"
"A protective sac surrounding the heart; provides lubrication and mechanical protection. Composed of fibrous, serous, and epicardium layers."
138
"What are the three layers of the heart wall?"
"1. Epicardium (outer) 2. Myocardium (muscular middle) 3. Endocardium (inner lining of chambers)"
139
"What causes heart valve problems?"
"Incompetent valves (leaky, do not close fully) and valvular stenosis (narrowed due to damage or deposits) both impair normal flow."
140
"What are the three layers of arteries and veins?"
"1. Tunica intima (endothelium) 2. Tunica media (smooth muscle) 3. Tunica externa/adventitia (connective tissue)"
141
"How does smooth muscle in blood vessels affect blood pressure?"
"Vasoconstriction (narrowing) increases resistance and BP; Vasodilation (widening) decreases resistance and BP. Flow ∝ radius⁴."
142
"What are the main types of capillaries and their functions?"
"1. Continuous: tight control (CNS, lungs) 2. Fenestrated: small pores for fluid exchange (kidney, glands) 3. Sinusoid: large gaps for cells (bone marrow, liver)"
143
"What is the role of the venous system?"
"Low-pressure system; stores ~65% of blood volume; contains valves to prevent backflow; returns blood to heart."
144
"Where is blood distributed at rest (upright vs. supine)?"
"Upright: 65% veins, 13% arteries, 15% central volume. Supine: 54% veins, 10% arteries, 30% central volume; central shift reduces peripheral pooling."
145
"What are the three circulatory systems associated with the heart?"
"1. Pulmonary (RHS to lungs) 2. Systemic (LHS to body) 3. Coronary (to heart tissue itself from aorta)"
146
"What is coronary circulation and why is it important?"
"Supplies oxygen and nutrients to the myocardium; coronary arteries arise from aorta and are closed during contraction, hence vulnerable to blockage."
147
"What determines ABO blood types?"
"Presence of A and/or B antigens on RBCs and corresponding antibodies in plasma; determined by alleles: A, B (co-dominant), and O (recessive)."
148
"What causes ABO incompatibility in newborns?"
"Mother's anti-A or anti-B antibodies attack fetal RBCs → jaundice, anaemia, high bilirubin. Severe cases may need phototherapy or transfusion."
149
"What are the two main phases of the cardiac cycle and what do they represent?"
"Systole: contraction (mainly ventricular); Diastole: relaxation (ventricular filling)."
150
"How long does the cardiac cycle last at rest (75 bpm) and what are the key timings?"
"Cycle lasts 0.8s: Atrial systole = 0.1s, Ventricular systole = 0.3s, Diastole = 0.4s."
151
"What causes the first and second heart sounds (LUBB and DUPP)?"
"LUBB: AV valve closure during ventricular contraction. DUPP: Semilunar valve closure during ventricular relaxation."
152
"What is isovolumetric contraction and what occurs during it?"
"All valves are closed. Ventricles contract, pressure rises but no blood is ejected. AV valves close (1st heart sound)."
153
"What happens during the rapid ejection phase of the cardiac cycle?"
"SL valves open as ventricular pressure exceeds arterial pressure; blood is ejected from the heart; no heart sound in healthy people."
154
"What causes isovolumetric relaxation and what are its effects?"
"All valves closed again. Ventricles relax; pressure drops. Second heart sound from SL valve closure; volume remains constant (ESV ~60 ml)."
155
"How is stroke volume (SV) calculated and what does it represent?"
"SV = EDV - ESV; represents the volume of blood ejected by each ventricle per beat (~70 ml)."
156
"How is cardiac output (CO) calculated?"
"CO = Stroke Volume × Heart Rate; typical rest value ≈ 5–6 L/min."
157
"What is Starling’s Law of the Heart?"
"As end-diastolic volume increases, the stroke volume increases due to stronger ventricular contraction (more stretch = more force)."
158
"What factors regulate heart rate and cardiac output?"
"Neural: SNS ↑HR, PNS ↓HR; Ion levels: Ca²⁺ and K⁺ affect contractility; Emotional/physical stress can modulate HR."
159
"What are preload
afterload, and contractility in relation to stroke volume?","Preload: end-diastolic stretch; Afterload: resistance to ventricular ejection; Contractility: force of myocardial contraction."
160
"What is the skeletal muscle pump and how does it aid venous return?"
"Skeletal muscles compress veins during movement, pushing blood toward the heart and improving venous return via one-way valves."
161
"What is the formula for blood pressure and what influences it?"
"BP = Cardiac Output × Total Peripheral Resistance; influenced by HR, SV, vessel constriction, blood volume, viscosity."
162
"What are baroreceptors and how do they regulate BP?"
"Stretch-sensitive receptors in the carotid sinus and aortic arch that detect BP changes and signal the cardiovascular centre to adjust SNS/PNS activity."
163
"What is the Mean Arterial Pressure (MAP) and how is it calculated?"
"MAP = Diastolic BP + (Pulse Pressure ÷ 3); reflects average arterial pressure during a full cardiac cycle."
164
"What are the two main anatomical divisions of the respiratory system?"
"Upper respiratory system (nasal cavity, pharynx, larynx) and lower respiratory system (trachea, bronchi, lungs)."
165
"What is the branching sequence of the bronchial tree from trachea to alveoli?"
"Trachea → Main bronchi → Lobar bronchi → Segmental bronchi → Bronchioles → Terminal bronchioles → Respiratory bronchioles → Alveolar ducts → Alveoli."
166
"What are the functional divisions of the respiratory system?"
"Conducting zone (air passage and conditioning) and respiratory zone (gas exchange)."
167
"What are the key functions of the lower respiratory system?"
"Filtration, warming and humidification of air, gas exchange, mucociliary clearance, and air passage."
168
"What is the structure and function of alveoli in gas exchange?"
"Alveoli are thin-walled sacs surrounded by capillaries, providing ~70 m² surface area for gas exchange through diffusion of O₂ and CO₂."
169
"What is pulmonary ventilation and what muscles are involved?"
"The process of breathing: inhalation and exhalation. Involves diaphragm, external and internal intercostals, and accessory muscles during forceful breathing."
170
"How does inhalation occur in terms of pressure changes?"
"Diaphragm and external intercostals contract → thoracic volume increases → alveolar pressure drops to 758 mmHg → air flows in due to pressure gradient."
171
"What happens during exhalation at the pressure level?"
"Muscles relax → thoracic volume decreases → alveolar pressure rises to 762 mmHg → air is expelled due to pressure gradient with atmosphere (760 mmHg)."
172
"What is Boyle’s Law and how does it apply to breathing?"
"Boyle’s Law: pressure of a gas is inversely proportional to its volume. During inhalation, increasing lung volume lowers pressure and draws air in."
173
"What are the factors that influence pulmonary ventilation efficiency?"
"Lung compliance, airway resistance, and surface tension in alveoli (reduced by surfactant)."
174
"What are the four primary lung volumes and their values?"
"Tidal Volume (500 mL), Inspiratory Reserve Volume (3100 mL), Expiratory Reserve Volume (1200 mL), Residual Volume (1200 mL)."
175
"What are lung capacities and how are they calculated?"
"Inspiratory Capacity = TV + IRV, Vital Capacity = TV + IRV + ERV, Total Lung Capacity = VC + RV, Functional Residual Capacity = ERV + RV."
176
"What is anatomical dead space and why is it significant?"
"Portion of air (~150 mL) that fills conducting airways and does not participate in gas exchange."
177
"What are the primary respiratory control centres and their roles?"
"Medullary centres (dorsal and ventral respiratory groups) and pontine centres regulate rhythm and depth of breathing."
178
"How do chemoreceptors influence breathing rate and depth?"
"Peripheral chemoreceptors detect changes in CO₂, O₂, and pH, signalling the respiratory centres to adjust ventilation accordingly."
179
"What is external respiration and where does it occur?"
"External respiration is the exchange of gases between alveoli and pulmonary capillaries: O₂ diffuses into blood; CO₂ diffuses out."
180
"What is internal respiration?"
"The exchange of gases between systemic capillaries and tissues: O₂ moves into cells, CO₂ moves into blood."
181
"What is partial pressure and how is it calculated?"
"Partial pressure (P or pp) is the pressure of an individual gas in a mixture, calculated as % of gas × total pressure (e.g., PO₂ = 21% × 760 mmHg = 159 mmHg)."
182
"What is Dalton’s Law of partial pressures?"
"The total pressure of a gas mixture equals the sum of partial pressures of each gas within it."
183
"How does altitude affect gas exchange?"
"At altitude, reduced PO₂ stimulates increased ventilation. At sea level, PCO₂ is the primary driver of respiratory rate."
184
"What is the function of surfactant in the alveoli?"
"Surfactant, produced by type II alveolar cells, reduces surface tension to prevent alveolar collapse, especially during exhalation."
185
"What is the structure of the respiratory membrane?"
"Composed of type I alveolar cells, alveolar basement membrane, interstitial space, capillary basement membrane, and capillary endothelium."
186
"What factors affect the rate of gas diffusion across the respiratory membrane?"
"Surface area, membrane thickness (diffusion distance), diffusion gradient, and the diffusion constant of the gas."
187
"What does Fick’s Law state regarding gas exchange?"
"Rate of diffusion ∝ surface area × pressure difference / thickness; diffusion increases with surface area and pressure gradient, and decreases with distance."
188
"What is the typical surface area and membrane thickness for gas exchange in healthy lungs?"
"Surface area: 70–100 m²; Thickness: 0.5–1.5 µm, enabling rapid gas diffusion."
189
"How does emphysema impair gas exchange?"
"Emphysema damages alveolar walls, reducing surface area and impairing oxygen diffusion."
190
"What is the ventilation-perfusion (V/Q) ratio and what is the ideal average?"
"The V/Q ratio compares ventilation (air flow) to perfusion (blood flow); average ideal V/Q = 0.8."
191
"How does gravity affect V/Q ratios in the lungs?"
"At the apex: higher V/Q due to more ventilation than perfusion. At the base: lower V/Q due to greater perfusion from gravity."
192
"What conditions can cause decreased V/Q ratios?"
"Diseases like asthma, bronchitis, and pulmonary oedema reduce ventilation, leading to low arterial PO₂ and elevated CO₂."
193
"What happens when V/Q ratio is high?"
"Ventilation is high but perfusion is low, increasing dead space and reducing arterial oxygenation (e.g., in emphysema or pulmonary embolism)."
