Download Cardiovascular system

Cardiovascular system
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Blood alkaline is composed of cellular and liquid components
Blood ph. range is 7.45- 7.50
3 functions?
- Distribute nutrients, o2.
- Regulate fluid volume, ph and body temp
- Protection from blood loss and infection
Blood components
1. Erythrocytes (RBC) 44%- transport haemoglobin
2. Leukocytes (WBC) 1%- responds to foreign bodies
3. Platelets 1%- assists in blood clotting
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Haematocrit- percentage of erythrocytes in a blood sample
Blood types
Type A- Anti-body B
Type B- Anti-body A
Type AB- neither A or B anti-body
Type 0- both A and B anti-body
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Heart location is in the mediastinum of the thorax
2 cardiovascular systems
1. Pulmonary circuit
Right side receives deoxygenated blood and pumps to the lungs for gas exchange
2. Systemic circuit
Left side of heart receives oxygenated blood pumped through body
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Pericardium: sac that encloses the heart
1. Fibrous pericardium: tough outer layer, protects and anchors
2. Serous pericardium: smooth, allows for gliding movement (visceral - internal surface &
parietal- external heart surface).
Pericardial cavity: serous fluid, no friction, movement of heart allowed. Between visceral
and parietal layers.
3 layers of the heart
1. Epicardium (outer)
2. Myocardium (middle)
3. Endocardium (inner)
Heart chambers
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Left and right atria- separated by interatrial septum
Left and right Ventricles- separated by interventricular septum
Fibrous skeleton: surrounds and supports valves, prevents them from stretching & basis of electrical
discontinuity between ventricle and atria.
Atrioventricular valves & semilunar valves direct blood in 1 way to prevent backflow.
Heart conduction system
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SA nodes fire
Excitation through arterial myocardium
Av nodes fire
Excitation through AV bundle
Purkinji fibres distribute excitation through ventricular myocardium
Cardiocytes
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Contract in response to electrical stimulation
Consist of:
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Mitochondria
Gap junction: allow ions to spread action potentials
Desmoses: functional syncytium: Mechanical junctions that prevent cardiocytes
from splitting.
Heart regulation
Neural control – medulla centre
Automatic nervous system
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Sympathetic system (fight or flight)
 Innervated by cardiac plexus
 Cardio stimulatory effect- increased heart rate and contraction.
Parasympathetic system (rest or digest)
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Innervated by Vagus nerve
Cardio inhibitory effect- decrease heart rate
Cardiac cycle
Completion of contraction and relaxation in heart chambers
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75 beats/min
Systole (contraction)
Diastole (relaxation of ventricles)
End diastolic volume (EDV): volume in ventricle at the end of diastole- 120ml.
End Systolic volume (ESV): volume in atria at end of systole- 50 ml
Stroke volume: volume ejected from ventricles per beat 70 ml
Formula: SV= EDV-ESV
Factors that affect stroke volume:
Preload: cardiocytes stretch before they contract
Contractility: strength achieved at muscle length
Afterload: pressure needed for ventricles to eject blood
Cardiac output (CO): the amount of blood pumped by ventricle per minute
CO = HR (Heart rate) x SV (stroke volume).
Heart sounds
Lub S1: Atrioventricular valves close, systole begins (ventricle contracts and pumps blood).
Dub S2: Semilunar valves close, diastole begins (relaxed, fills with blood).
Arteries: Oxygenated blood carried away from the heart
Veins: Deoxygenated blood towards the heart. Lower pressure then arteries.
Layers of the arteries
1. Tunica Interna (inner layer): reduces friction, vessel lumen & endothelium
2. Tunica Media (middle layer): Increases vasoconstriction and decreases vasodilation
3. Tunica externa (outer layer): anchorage and protection
3 types of arteries
1. Muscular artery: blood to organs
2. Elastic artery: blood to systems
3. Arteriole: blood to tissue, arteriole diameter determines blood flow to capillaries
Capillaries: blood to tissue cells
- Smallest lumen to allow 1 erythrocyte through
- Function: exchange O2 and Co2, nutrients and hormones between interstitial fluid
3 types of capillaries
1. Continuous: intercellular clefts (gap junctions), less permeable
2. Fenestrated: small, nutrients, hormones and filtration to pass through
3. Sinusoidal: leaky, RBCs & Molecules can pass, leaky and modified
Layers of capillary wall
1. Endothelial cells: lipid soluble substances
2. Fenestrations (pores): larger soluable & water
3. Intercellular clefts: water soluable
Capillary exchange: movement of fluid in – out of capillaries
Semipermeable membrane- selectively allows particles to move through
Microcirculation: blood flow from arteriole to venule
Vascular shunt: connects the arterioles to the venules.
True capillaries: site of gas exchange
Bulk flow: fluid forced in and out of capillaries
1. Filtration of fluid: blood hydrostatic pressure promotes selective movement out of capillary
2. Reabsorption: Blood colloid osmotic pressure promotes interstitial fluid to move into
capillaries.
Filtration pressure: difference between blood hydrostatic pressure and colloid osmotic
pressure
If BHP STRONGER= PRESSURE OUT
IF COP STRONGER= PRESSURE IN
Blood hydrostatic pressure must be greater than colloid osmotic pressure in the capillary for
reabsorption to occur.
Veins
3 layers of veins:
1. Tunica Interna (inner): vessel lumen
2. Tunica Media (middle): innervated by sympathetic nervous system
3. Tunica Externa (outer): anchorage & protection
Types of veins
1. Venule- formed when capillaries unite
2. Medium vein- formed when venules unite, large blood volume
3. Large veins- low pressure, united medium veins
Pressure gradient: difference in fluid pressure
Blood flow: enabled by blood pressure and peripheral resistance
Sources of resistance
1. Vessel diameter- wider = lower resistance
2. Vessel length – longer = greater resistance
3. Viscosity – thickness
Venous blood flow
Skeletal muscle pump: muscle contraction, pressure on veins, blood to heart
Respiratory pump: decreased thoracic pressure during inhalation, blood to thoracic veins and right
atrium
Systemic blood pressure: pressure exerted on blood vessels in systemic circulation
Pressure exerted on arteries during contraction
Systolic pressure: exerted pressure during ventricular contraction
Diastolic pressure: lowest level of arterial pressure
Pulse pressure: difference between systolic and diastolic pressure
MAP (Mean arterial pressure): pressure that propels blood to tissue
MAP= diastolic pressure + 1/3 pulse pressure
Control of blood pressure
1. Short term neural & hormonal control: fluctuations in blood pressure by altering peripheral
resistance.
2. Long term renal regulations: controls fluctuations in blood pressure by altering blood
volume.
Neural controls of peripheral resistance: Maintain MAP- alters blood vessel diameter
Operate via reflex arcs that involve:
1. Baroreceptors (respond to changes in arterial pressure and stretch) & chemoreceptors
(respond to changes in 02, CO2 and H+)
2. Vasomotor in medulla: cardio-stimulatory centre & cardio-inhibitory centre
3. Vascular smooth muscle
Hormones influence BP through vasoactive effect or water regulation:
Angiostenin II: vasoconstrictor, raises BP
Aldersterone: Na+ and water retention by kidneys, raises BP and blood volume
ANP: increase urinary na+ excretion, reduces blood volume and BP
ADH: promotes water retention and raises BP.
Respiratory System
Functions of the respiratory system
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Gaseous exchange
Warms & filters the air
Acid-base balance
Phonation (voice production)
Defence against pathogens
Gas exchange between air and blood: lungs to tissues then back to lungs
Cells in body require continuous oxygen during metabolism.
Respiration process
Ventilation: air in & out of lungs due to changes in pressure of the bronchial tree and alveoli.
Inhalation: external intercostal pull ribs up & out, diaphragm flattens, thoracic cavity enlarges, lungs
expand, intrapulmonic pressure decreases (drops below atmospheric pressure).
Exhalation: respiratory muscles relax, thoracic cavity becomes smaller, intrapulmonic pressure
increases, air is forced out, and atmospheric & intrapulmonic pressure becomes equal.
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Pulmonary process: movement of air in and out of lungs
External respiration: o2 lungs to blood & co2 blood to lungs
Transport of respiratory gases: o2 body tissues to cells & Co2 body tissue to blood
Internal respiration: O2 blood to tissue cells & Co2 tissue cells to blood
Divisions of the respiratory system
1. Upper respiratory tract: nasal cavity, paranasal sinuses, pharynx
Lower respiratory tract: larynx, trachea, bronchi & lungs
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External intercostal muscles pull ribs up for inhalation
Internal intercostal muscles pull ribs down for exhalation
Diaphragm shortens and flattens to expand thoracic cavity
2. Conducting zone: conducts gas to exchange site
3. Respiratory zone: site of gas exchange