CVRS Flashcards
Appreciate how different epithelial surfaces have adapted for function.
○ Epithelium is formed by cells within an ECM
○ The cells in this tissue are tightly packed within a thin ECM
§ Forming sheets that cover the internal and external body surfaces (surface
epithelium) and secreting organs (glandular epithelium).
○ Functions of epithelial tissue are secretion, protection, absorption, transportation and special sensory receptive.
Discuss why epithelial surfaces are susceptible to environmental factors that can cause disease
○ External surfaces are susceptible to environmental insults (trauma and infection)
○ Mucous membranes are particularly susceptible (thin walled)
○ Routes of infection
§ Horizontal transmission – direct contact, aerosol, orofacial, vector borne
§ Vertical transmission – direct contact
(P1) Discuss adaptations of skin, respiratory tract and alimentary tract to protect against environmental insults such as trauma and infectious agents
○ Defensive Barriers § Physical – Skin § Physiological – Mucous membranes § Biochemical – Gastric Acid § Chemical – Lysozyme § Cellular – Macrophages
○ Skin adaptation
§ Commensal flora – provide competition & prevent pathogen colonisation
§ Physical barrier – keratinocytes replicate to generate stratified squamous
keratinised epithelium
§ Melanocytes – UV damage protection
§ Langerhans cells – immune sentinels
§ Sebaceous glands & sebum – chemical barrier (fatty acids 5.5pH, anti-
microbial)
§ AMPs – beta-defensins that disrupt microbial membranes/intracellular
functions
§ Keratinocytes
□ TLR signalling cascade creates anti-microbial soluble factors
□ trigger inflammation
® produce cytokines (immunological hormone)
® produce chemokines (cell migration factors)
(P2) Discuss adaptations of skin, respiratory tract and alimentary tract to protect against environmental insults such as trauma and infectious agents
○ Respiratory adaptation
§ Mucous – antimicrobial compounds, antibodies (IgA), antioxidants
§ Muscociliary escalator – continual ciliation stops pathogen attaching to
surface
§ Alveolar macrophages – defence against inhaled pathogens
§ Phagocytosis – attachment, phagosome, kill & digest, post digestion
○ Alimentary Adaptation
§ Oral cavity & oesophagus
□ physical (stratified squamous epithelial)
□ biochemical (lysozyme in saliva)
§ Stomach – sterilisation & food digestion (HCl acid pH2, mucous protect
epithelium)
§ Small intestine – cryptidins (toxic to bacteria)
§ GIT – mucosal protective antibody (IgA), Peyers patches (gut-associated
lymphoid tissue)
Describe the functions of the mammalian cardiovascular system
§ Transport of O2 and substrates to cells
□ glucose, fatty acids, amino acids, vitamins, drugs etc
§ Transport of CO2 and metabolites from cells (urea, creatinine etc)
§ Distribution of hormones - adrenaline (epinephrine) - regulates CVS
§ Defence - cells and molecules are carried in the blood
§ Haemostasis
□ Blood clotting mechanism (cessation bleeding from a blood vessel)
§ Thermoregulation – Regulated flow to skin and extremities
○ (Dissipated heat from deep organs)
Descibe the components and major features of the mammalian cardiovascular system.
§ Heart
□ Components – pump (driving force), 2 atria & 2 ventricles,
contractions via intrinsic pacemaker (ANS stimulation)
□ Major features – cranial/caudal vena cava, R atrium, R ventricle,
pulmonary artery, pulmonary vein, L atrium, L
ventricle, aorta
§ Blood Vessels
□ Components – arteries, microcirculation (capillaries), veins
(reservoirs)
□ Arteries & Veins Major features - lumen, tunica intima (endothelium),
tunica media (smooth muscle),
tunica externa (support)
□ Capillary major features – endothelium intima, simple endothelial
cells on basement membrane, pericytes
(external - contractile)
Understand the relationship between pressure and flow in the circulation.
○ Blood flow (f) is directly proportional to blood pressure gradient (ΔP)
○ Blood flow is inversely proportional to resistance (R)
○ Blood flow = blood pressure / resistance (F = ΔP/R)
○ Vasoconstriction = inc. R & dec. F
○ Vasodilation = inc. F & dec. R
Describe the origin and propagation of the heartbeat.
○ Sinoatrial (SA) node – origin primary pacemaker region via ANS
○ Propagation – SA node spontaneously depolarises, AV node, Bundle of His,
Purkinje fibres, ventricular muscle
○ SA node action potential – slow polarisation (K out, Na & Ca in), rapid
polarisation (L type calcium channels open),
repolarisation (potassium permeability increases)
Outline the unique features of cardiac muscle.
○ Principle features – good blood supply, branched fibres, intercalated discs (gap
junctions), central nuclei, high mitochondrial density
○ Functional syncytium -myocyte cells electrically & mechanically coupled
§ Electrochemical link
□ gap junctions (between each cell)
□ How electric signal is spread from cell to cell
§ Mechanical link
□ desmosomes (anchor cells together) & actin filament
□ Provide stability & links all cells together
(P1) Describe the mechanisms contributing to the coordination of the cardiac cycle.
○ Systole – CICR (calcium-induced release) (contract)
1. Action potential arrives in t-tubule
2. Signal opened up L type calcium channels on t-tubule
3. Calcium enters from ECM into muscle cell cytosol (inc. calcium in cell)
4. Calcium release channels on S.M cell membrane (activated by Ca)
5. Calcium binds to S.M channels = open & calcium released from
intracellular stores into cytosol
6. Calcium binds to troponin C in cytosol = contract muscle cell
(P2) Describe the mechanisms contributing to the coordination of the cardiac cycle.
○ Diastole – Reduce intracellular calcium (relax)
§ 1. Facilitated transport (Na+/Ca2+ exchanger (3:1)
□ Extrudes calcium in exchange for sodium into cell
§ 2. Energy Dependant Pumps (e.g. Ca2+ ATPase)
□ Sit in plasma membrane & extrude calcium out of cell
○ S.M pumps retrieve calcium from cytosol and store back inside S.M
(P3) Describe the mechanisms contributing to the coordination of the cardiac cycle.
○ Refractory Period
§ Relatively long due to plateau phase
§ Cell unable to respond to further/any other stimulation
§ Allows ventricles sufficient time to empty & refill before next contraction
Define cardiac output, preload and afterload.
○ Cardiac output – volume of blood pumped into the aorta (per unit time)
○ Preload – volume of blood in ventricles at end of diastole (end diastolic
pressure)
○ Afterload – resistance the left ventricle overcomes to circulate blood (pressure
against the heart ejects)
Explain how changes in heart rate regulate cardiac output
§ Vegas nerve – innervates SA, AV, small atria
§ Adrenergic fibres – innervates SA, AV, A&V
§ Regulated by SA node
□ Parasympathetic (vagal)
® acetylcholine release = dec. heartrate
® slower depolarisation
® intervenes with sympathetic (stops noradrenaline release)
◊ AFFECTS CONTRACTILITY OF ATRIAL MUSCLE
□ Sympathetic ® noradrenaline release = inc. heartrate ® faster depolarisation
Explain how changes in stroke volume regulate cardiac output
§ Determinants
□ Preload – greater SV via raised preload & inc. diastolic volume
□ Afterload – regulated by inc. or dec. heart contractility
§ Intrinsic regulation (own system)
□ Change filling pressure & muscle resting length
§ Extrinsic regulation
□ Sympathetic stimulation
□ Increased contractility at constant filling pressure = +ve inotropism
§ Sympathetic stimulation on ventricles increase:
□ Rate of force development
□ Rate of relaxation
□ Maximal force developed
