Intro to Circulation, Perfusion, Blood Pressure Flashcards
Lecture 1 and 2
Venous Return
The rate of blood flowing back to the heart through the veins
Preload
the initial stretching of the cardiac myocytes during diastole before the contraction
- this depends on venous return
Volume overload
when preload becomes to large
Factors Affecting preload (increased)
- increased Atrial contractility
- decreased HR
- increased Aortic pressure
- increased central venous pressure
- increased ventricular compliance
Afterload
the resistance that the chambers of the heart must overcome during systole
Features of the pulmonary circulation
- High capillary density
- Low vascular resistance
- Acts as a blood reservoir
- Endocrine control of BP (ACE)
- Acts as a Filter
ACE in the lungs
Angiotensin Converting Enzyme, 1 into 2
- located in endothelial cells
The affect of low O2 in a region of the lungs
- the arterioles constrict
- poor ventilation leads to reduced perfusion
- this minimises the amount of blood that is poorly oxygenated
Hypertension
- high blood pressure (diastolic)
- lead to coranry artery disease MI
- idiopathic causes, hormones (Ang II) and Brain Medulla (NTS)
NTS in hypertension
The nucleus of the solitary tract
- part of the dorsal medulla
- the first synaptic station for cardiorespiratory afferent inputs
- neurons in the NTS are essential for the processing of sympathetic and respiratory responses to hypoxia
Chronic Hypertension can lead to
- Stroke
- Aneurysm
- MI
- Kidney failure
- Heart Failure
- Cardiac Hypertrophy
Stroke
the rapid loss of brain function due to disturbance in blood supply to the brain
Aneurysm
a localized, blood filled balloon-like enlargement in the wall of a blood vessel
- due to weakening structure
- tearing or ripping of the blood vessel
- ultimately result in internal haemorrhage
Orthostatic Hypertension
low BP on standing to due to low decreased venous return
Cardiogenic Shock
critically low perfusion caused by the heart
Compensatory mechanisms of cardiogenic shock
- Tachycardia
- Tachypnoea
Failure to compensate symptoms in cardiogenic shock
- low urine output
- hypotension
- confusion
- confusion
- syncope
- acidosis
Perfusion
requires a pressure difference in order for flow to occure
Syncope
- fainting, due to insufficient blood to the head, hypotension
Shock
Insufficient perfusion
Pulmonary circulation
- from the right heart,
- series flow system
Systemic circulation
- from the left side of the heart
- parallel branching paths
- concurrent flow
Pressure and Flow
BP= cardiac output x peripheral resistance
action and role of theAorta
stretch and recoil, stores energy
role of the Arteries
distribute, volume adjust
role of the Arterioles
regulate caps, resistance set BP & TPR
role of the Capillaries
Exchange, nutrients,gas,fluid
role of the Venules
collect blood, some exchange
role of the Veins
Reservoir for blood, muscle pump
~64% of blood volume
Right Ventricle
- thin walled
- crescent x-section (anterior view)
- supply only lungs
- low pressure
- high perfusion
- low resistance
Left ventricle
- Thick walled
- Circular x-section from and (anterior view)
- supplies many organs
- high pressure
- variable flow
- variable resistance
Apex Beat
apex of the heart moves forward and strikes the chest wall
Mitral Valve
- between left atrium and ventricle
- has 2 leaflets
- papillary muscle and chordae tendineae prevent eversion of valve flaps
AV Valves
- Mitral & tricuspid
- have papillary fibres to prevent prolapse
- close during systoles
- S1: first heart sound (lub)
Semilunar valves
- Aortic and Pulmonary valves
- moon-shaped
- Close during diastole
- diastole is longer than systole
- S2: second heart sound (dub)
Blood volume - kidneys
- depends on water intake
NOT formed elements
Formed elements
- red/ white blood cells
- platelets
Peritubular capillaries
small blood vessels that travel alongside the nephrons
- allows reabsorption and secretion between the blood and the lumen of the nephron
Glomerular filtration rate
- all the fluid entering all the bowman’s capsules in the kidney
Hypoxia, Anoxia, Hypoxemia
insufficient O2 supply to a region or to entire body
Hypoxemia
net low amount of oxygen in arterial blood.
refers to the whole arterial system
Ischaemia
insufficient blood flow to a region
Anoxia
no oxygen locally
Angina Pectoris: symptom
chest pain due to:
- over-exertion or damage to heart tissue
Angina Pectoris: Treatment
Nitrates, opens blood vessels in the heart
Myocardial Infarction: treatment
- Immediate reperfusion (within 2 hours)
- PCI
- removing plaque ore thrombus
- MONA
what does MONA stand for and when is it applied
- Morphine
- Oxygen
- Nitrates (vasodilation)
-Aspirin
treatment for MI
what is PCI
Percutaneous coronary intervention: balloon angioplasty
Syncope
loss of consciousness
due to insufficient blood flow to the brain
- Shock
- Arrhythmia
Pulse Pressure
= P(systolic) - P(diastolic)
the difference between the diastolic and systolic pressure
Mean Arterial Pressure
= P(diastolic) + [P(systolic) - P(diastolic)]/3
Cardiac Output
Stroke volume x Heart rate
Stroke volume
volume of blood pumpes out of a ventricle during one beat of the heart
Heart rate
reciprocal is RR interval (ECG r-waves)
Atrial Systole cardiac cycle fact
adds final 20/25% of total to fill the ventricles
End Diastolic Volume
120ml
- volume of blood in a ventricle at the end of diastole
End Systolic Volume
50ml
- volume of blood remaining in a ventricle at the end of systole
Ejection fraction
55-70%
Exercise and Vasomotor system
- peripheral vasodilation (skin/muscle)
- Vasoconstriction in the splanchnic circulation
Standing up and Vasomotor
- initial drop in BP followed by compensatory recovery
- Peripheral vasoconstriction
- arterial + venous
- increase HR
- BP no systolic change, diastolic increases
Control of Systemic BP
Local - endothelial, NO
Neurological- the autonomic system
Humoral - renal/ pituitary/adrenal
Shear force
the force on the endothelium in the direction of the flow of blood
- increased by laminar flow
- atheroprotective
