HUBS1404 Summary Notes (L1-17) PDF

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My memorised summaries before the mid semester exam - which I got a credit on...

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Lecture 1: Overview of the Cardiovascular System PASS Information List the two primary functions of the Cardiovascular system: n Pump oxygen and nutrients to cells n Remove carbon dioxide and waste n BONUS: transport for hormones and antibodies What are the names and function of the two main circuits of the cardiovascular system? n Pulmonary – oxygenates blood n Systemic – transport around body (supplies oxygen and nutrients, and removes waste) Other Questions: n Cells dispose of their waste down concentration gradients n The largest percentage of blood distributed in the body is within systemic veins and venules (because there is less pressure to push the blood back up) n Blood in the systemic arteries and arterioles travel faster, and therefore less is stored n Fluid will only flow in a system if there is a positive pressure gradient across the length of the vessel n Flow = ∆P/TPR n Flow and pressure are proportionate, while resistance is inversely proportional Summary (Learning Objectives) Understand the purpose of the circulatory system: n To transport oxygen and nutrients to cells n To remove carbon dioxide and waste Discuss why the circulatory system structure is needed for humans n Complex structure due to extremities and large body n Double pump – one to oxygenate blood, the other to send it out to the rest of the body List two key physical parameters that enables change in fluid flow along a tube and how these affect flow n n n n

Flow = ∆P/TPR Increased pressure = increased flow Increased resistance = decreased flow Increased radius = decreased resistance

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Lecture 2: Anatomy of the Heart Summary (Learning Objectives) Draw the flow of blood through the chambers of the heart and heart valves indicating where the blood is coming from and going to in terms of pulmonary and systemic circulations

Right atrium → tricuspid valve → right ventricle → pulmonary valve → pulmonary artery (trunk, arteries) → pulmonary capillaries → pulmonary veins → left atrium → bicuspid valve → left ventricle → aortic valve → aorta → systemic arteries → systemic capillaries → systemic veins→ superior and inferior vena cava and coronary sinus → Describe the function of those anatomical features mentioned in this module n n n n

Atrioventricular valves: stop backflow to the atrium Semilunar valves: stop backflow to the ventricles Atrium: receive blood Ventricles: pump out blood

Understand the operation of the heart valves and associated heart sounds n First sound in heart beat: atrioventricular valves opening n Second sound in heartbeat: semilunar valves opening n Blood backflow: heart murmur

Describe the functional and structural differences between the left and right sides of the heart (e.g. Heart wall thickness) n Right: to the lungs, therefore thin and relatively low pressure n Left: to the body; therefore thick and relatively high pressure Discuss the coronary circulation and understand that small blockages of the coronary circulation can have disastrous consequences n Coronary circulation; circulation of blood within the heart n Coronary arteries and cardiac veins n Plaque build up can restrict blood flow within the heart and stop it from working

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Lecture 3: Coordination of Cardiac Contraction PASS Information Label the depolarization, plateau, and repolarization on the graph

Summary (Learning Objectives) Recall the ionic mechanisms which underlie the cardiac action potential and control of heart contraction n Repolarisation – influx of Na through open voltage channels n Plateau – opening slow Ca channels and some K channels n Repolarisation – Ca inactive, K open back to resting membrane potential Describe the structures responsible for the spread of excitation through the heart n n n n n

SA node – pacemaker, in right atrium AV node – above tricuspid valve, receive signal Interventricular septum – link to atrioventricular bundle/bundle of His Atrioventricular bundle/bundle of His – transfer signal to inferior end of heart Purkinje fibres – left and right ventricles

Describe the sequence in which different cardiac structures are excited n n n n

Pacemaker cells in sinoatrial (SA) node Spread impulses across atria through gap junctions to atrioventricular (AV) node Delay (milliseconds), atrial contraction begins To inferior end of heart through atrioventricular bundle/bundle of His – branches into left and right ventricles

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n Signal disperses into purkinje fibres, triggering depolarisation in surrounding cells (contraction from the bottom up) Understand how an ECG is measured, know what the peaks in an ECG trace mean and describe how an ECG trace would look when heart function is abnormal for those examples provided n ECG – electrocardiogram n ECG measures timing of contraction and relaxation of the heart through extracellular currents on the skin which match pulse sequence n ECG = electrocardiogram n P wave = atrial depolarisation n QRS eave = ventricle depolarisation (and atrial repolarisation) n T wave = ventricle repolarisation n Graph without P, QRS, and T waves are atypical – can show weak/no/delayed/etc. contraction in parts of heart. Describe the cardiac cycle in terms of pressure and volume changes over the cycle and relate this to the timing of heart sounds and ECG waves

Explain in detail the mechanisms by which the nervous system modulates heart rate n Heart rate intrinsic, but nervous system can be used to change heart rate n Parasympathetic: decrease heart rate o Vagus – when excited, signal to synapse neurons next to the heart that connects with the SA node cells. Mostly release transmitter to slow them down. Slow heart rate through dorsal motor nucleus of vagus n Sympathetic: increase heart rate o Medulla oblongata signal through spinal cord, sympathetic ganglion on either side of the aorta can send an axon to the SA node to speed up heart rate n Neurotransmitters: o Parasympathetic – Acetylcholine – to SA node to slow down, Released from cells and activates muscarinic receptor – change how leaky the membrane is, change way the channels open, slow gradient therefore takes longer to reach threshold. o Sympathetic – Noradrenaline – to SA node cell to speed up, released from cell and activates on beta adrenal receptor – make proteins in membrane leakier, therefore reaches threshold faster

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Lecture 4: Blood Pressure and the Circulation PASS Information List some examples for each mechanism that controls vessel diameter n Metabolic o Decrease pH → dilate (allow more O2) o Decrease O2 → dilate (allow more CO2) o Increase CO2; K+, prostaglandins, adenosine, nitric oxide → dilate o Increase endothelins → constrict n Myogenic o Stretch receptors activated → constrict n Nerves o Sympathetic → constrict (more pressure) o Parasympathetic → dilate n Hormones o Epinephrine, angiotensin II, antidiuretic hormone (ADH) → constrict o Atrial natriuretic peptide (ANP) → dilates Summary (Learning Objectives) Outline the vessels through which blood moves on its passage from the heart to the capillaries and back n Aorta → elastic artery → muscular artery → arteriole → continuous capillary → fenestrated capillary → venule → medium sized vein → large vein (SVC, IVC) Know the anatomy of blood vessels and different levels of the circulation and the relative distribution of blood within these different vessels n Most blood vessels have three layers o Inner = tunica intima – contains endothelium (simple squamous epithelium – continuous with lining of heart, creates slick surface, helps blood move without friction), connective tissue, and internal elastic membrane o Middle = tunica media – contains smooth muscle cells and sheets of protein elastin (external elastic membrane). Smooth muscle tissue regulated by nerve fibres of ANS, therefore decrease diameter of lumen by contracting tunica media during vasoconstriction, or expanding it by relaxing during vasodilation § The smaller the diameter of the blood vessel, the harder it is for blood to move through it o Outer = tunica externa – overcoat made of loosely woven collagen fibre. Protects and reinforces the blood vessel n Arteries are thicker than veins n Veins contain valves to prevent backflow n Fenestrated/continuous capillaries → basal lamina and endothelium (fenestrated has pores) Distinguish between pressure reservoir (arteries) and blood reservoir (veins) features n Arteries – high pressure, thick muscular layers, non-compliant, resistors n Veins – low pressure, thin muscular layers, valves to prevent backflow, compliant/elastic, Biomedical Sciences 2

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capacitators Know the key physical determinants of blood flow and how they affect flow n ∆ Pressure (↑ to ↓, diffusion) n Resistance (of vessels) o Size if lumen (large = less) o Vessel length (larger = more pressure) o Viscosity (thickness of liquid) Know that small arteries and arterioles are under nervous, local, and endocrine control

Appreciate the concept of blood pressure and mean arterial pressure n Blood pressure is arterial hydrostatic pressure (~120/80mmHg), and it fluctuates with systolic and diastolic pressure. Calculation: 𝑆𝐵𝑃 𝐵𝑃 = 𝐷𝐵𝑃 n Mean arterial pressure (MAP) is average pressure in arteries during a cardiac cycle – considered a better indicator of perfusion to vital organs. Calculation: 𝑆𝐵𝑃 + 2𝐷𝐵𝑃 𝑀𝐴𝑃 = 3 n Systolic pressure = highest level of pressure the blood reaches during heart contraction n Diastolic pressure = lowest level of pressure the blood reaches during heart relaxation

Explain different

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Lecture 5: Tissue Perfusion and Fluid Recovery PASS Information Define: n Hydrostatic pressure – the difference between the pressure in the capillary and that in the surrounding tissue o More pressure in the capillary, forcing what’s in the vessel out with net force. Eventually, pressure is smaller inside, then moves back in n Colloid Osmotic pressure – Difference between intravascular osmotic pressure due to plasma proteins and extracellular osmotic pressure due to interstitial proteins o Bring blood back in n Ultrafiltration – filter things out o Higher pressure, net filtration out n Reabsorption – take things in o Lower pressure, net absorption in Summary (Learning Objectives) Know the functions of the different types of capillaries n Continuous – located in CNS, lungs, muscle, skin n Fenestrated – pores – located in kidneys, small intestine, brain ventricles, eyes, endocrine glands n Sinusoid – incomplete basal membrane – located in liver, spleen, anterior pituitary, parathyroid, adrenals, red bone marrow Discuss the pressures that cause movement of fluids between capillaries and interstitial space (know how water, gases, and various types of solutes move across capillaries) Diffusion through membrane (lipid-soluble substances) Movement through intercellular clefts (small water-soluble substances) Through fenestrations where present (allows larger molecules through) Transport via vesicles (transocytosis) Transcellular (aquaporin channels) Paracellular (fenestrations, gaps) Hydrostatic pressure – difference between pressure in capillary and in surrounding tissue o Forces water out, but the remaining large molecules within the capillary attract it back n Colloid osmotic pressure – difference between intravascular osmotic pressure due to plasma proteins and the extravascular osmotic pressure due to interstitial proteins and proteoglycans n n n n n n n

Understand how blood moves through the veins and lymph moves through the lymphatic vessels n Venuous return due to pressure from left ventricle contractions o Venuous pressure is low – most veins have valves o Smooth muscle in veins, skeletal muscle and respiratory pumps help move blood back to the heart n Lymphatic system removes excess fluid o Return excess interstitial fluid into the blood – aided by smooth and skeletal muscles, and valves

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Lecture 6: Blood Volume Regulation PASS Information Describe the intrinsic and extrinsic determinants of cardiac output n Intrinsic – heart; end systolic and end diastolic volume n Extrinsic – everything else; nervous system (parasympathetic and sympathetic) and endocrine system (adrenaline) Summary (Learning Objectives) Define cardiac output n Cardiac Output = Heart Rate x Stroke Volume Understand the relationship between blood pressure, cardiac output, and peripheral resistance, and use this information to determine how alterations to one of these factors would affect the other n BP = CO x TPR n CO = HR x SV n ∴ BP = HR x SV x TPR Understand the terms preload and afterload n Both effectors of end systolic volume n Preload – increased filling of ventricles due to stretching of cardiac muscle, resulting in a more forceful contraction. Related to length tension relationship of cardiac muscle n Afterload – aortic pressure List the main receptors which your body uses to measure changes in blood pressure and blood volume n Baroreceptors – in aorta wall to measure pressure, send signals to cardiovascular center in brainstem, which then effects change by modifying blood pressure (cardiac output and total peripheral resistance) n Atrial baroreceptors – indirect measure of blood volume n Pressure receptors – in atria, measure filling pressure. Can increase heart rate to shift excess blood from venous side to atrial side. List the effectors which your body uses to change blood pressure and volume n Short term – ANS and specialised sensory neurons activate heart and arteries – important following postural changes, and in anticipation/response to exercise and changes in body temp n Intermediate term o Hormonal (renin angiotensin system) - Angiotensinogen →(renin)→Angiotensin I → (angiotensin converting enzyme) → Angiotensin II → constricts arteries → increase blood pressure o Autoregulation (capillary fluid shift) – less fluid into tissues to maintain blood volume n Long term – kidneys change amount of water secreted in urine Understand the mechanisms by which these effectors are activated n Hormones increasing blood pressure: norepinephrine, epinephrine, angiotensin II, antidiuretic hormone (ADH), aldosterone n Hormones decreasing blood pressure: atrial natriuretic peptide (ANP), nitric oxide

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Lecture 7: Organisation of the Respiratory System PASS Information List the components of n Upper Respiratory System – nose and pharynx n Lower Respiratory System – larynx , trachea, and alveoli Describe the branching of the bronchial tree and what happens to the structure of these branches n Vessels made of cartilage to stay open n Down in lungs, no cartilage because need to pass through blood (O2), therefore made of elastic smooth muscles n 23 branches, starting with all cartilage and moving to all muscle n Trachea → main bronchi → lober bronchi → segmented bronchi → bronchioles → [alveoli → membrane] Summary (Learning Objectives) Know all the components of the respiratory system and their major function(s) n Nose – filters, warms, and moistens the air n Pharynx – passageway for air and food n Larynx – vocal folds, protects glottis – three large cartilages – thyroid (shield), cricoid (posterior), epiglottis (protects glottis) – small cartilage structures – arytenoid, corniculate, cuneiform n Trachea – cleans, warms, and moistens the air n Alveoli – site of gas exchange – bronchial artery supplies the bronchi with arteriole blood – visceral and parietal pleura – type I pneumocytes – type II pneumocytes (surfactant) n Lungs – right 3 lobes, left 2 lobes, sits in pleural cavity – house small respiratory passages n Pulmonary arteries and veins – arteries from right ventricle, veins to left ventricle – primary bronchus o Bronchial tree – 23 branches, at top cartilage down to muscle – Main bronchi → Lobar bronchi → segmental bronchi → bronchioles → terminal bronchioles Understand the concept of partial pressure and the relationship between the partial pressure of a gas and its solubility n n n n n n n n n

Henry’s Law: the amount of gas in a solution is proportional to its partial pressure (outside the liquid) and its solubility Air: 78% Nitrogen, 21% Oxygen PN2 + PO2 + PH2O + PCO2 = 760mmHg Partial pressure of a gas allows us to predict its behaviour in the body In moist air we have to take PH2O into account In solution, gas diffuses down its concentration gradient Alveolar air is humidified Gas exchange at the alveoli modifies CO2 and O2 content Exhaled air is a mixture of alveolar air and the air in the ‘dead space’ which did not participate in gas exchange

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Lecture 8: Breathing PASS Information Define: n Intrapulmonary pressure – pressure inside lungs decreases as lung volume increases during inspiration; pressure increases during expiration n Intrapleural pressure – pleural cavity pressure becomes more negative (from outside pressure) as chest wall expands during inspiration. Returns to initial value as chest wall recoils n Volume of breath – during each breath, the pressure gradients move 0.5L of air into and out of the lungs What three factors affect lung compliance? n n n n

Lung compliance = how much lungs can expand – how elastic Level of surfactant → what allows movement, more surfactant = more movement Mobility of the thoracic cage Healthiness of the lung connective tissue

Surfactant is released by what type of cells n Type II Pneumocytes Summary (Learning Objectives) Describe the mechanics of breathing and know which muscles are involved n Inhalation – diaphragm contracts and external intercostals contract, chest cavity expands, alveolar pressure drops below atmospheric pressure, air flows in response to pressure gradient, lung volume expands n Deep inhalation – scalene and sternocleidomastoid muscles expand further n Exhalation – diaphragm relaxes and external intercostals relax, chest and lungs recoil, chest cavity contracts, alveolar pressure increases above atmospheric pressure, air flows out of lungs in response to pressure gradient, lung volume decreases n Forced exhalation – internal intercostals and abdominal muscles contract Know the respiratory volumes and capacities n n n n n n n n

Tidal volume – air in and out during normal respiration Inspiratory reserve volume – amount you can breathe in with effort Expiratory reserve volume – amount you can breathe out with effort Reserve volume – amount of air that remains in the lungs Functional reserve capacity – amount of air remaining in lungs after normal respiration (RV + ERV) Inspiratory capacity – amount of air that can be inhaled (TV + IRV) Vital capacity – amount of air that can be breathed in and out (ERV + TV + IRV) Total lung capacity – amount of air in lungs (IRV + TV + ERV + RV)

Know the major neural centers involved in the control of respiration

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n Pons, Medulla, Ventral respiratory group, Dorsal respiratory group, Chemoreceptors Discuss the respiratory reflexes their stimuli and response n n n n

Sigh – deep breaths Yawn – open up collapsed airways not opened with a sigh Cough – irritants in chest – air flow with closed glottis, then rapid release of glottis Sneeze – irritants in nose

Understand the function of chemoreceptors in relation to the control of breathing and know the main factors which influence rate and depth of breathing n Peripheral chemoreceptors – in aortic arch and carotid bodies n Central chemoreceptors – medulla n Most sensitive to changes in CO2 and pH

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Lecture 9: Gas Exchange PASS Information What is haemoglobin saturation n Percentage of red blood cells (haem units) bound to oxygen (↑=+) What is the effect of O2 binding to haemoglobin n When o o n When o

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