Cardiovascular system Flashcards
What is the pulmonary circulation?
Oxygen depleted blood
Passes from heart to lungs
Returns oxygenated blood to heart
What is the systemic circulation?
Oxygen rich blood
Passes from heart to rest of body
Returns deoxygenated blood to heart
What is the mediastinum?
A membranous partition between two body cavities or two parts of an organ, especially that between the lungs
What is the structure of the heart wall?
Fibrous layer
Pericardium - parietal, cavity, visceral
Myocardium
Endocardium
What does the ductus venosus do?
Shunts a portion of the left umbilical vein bloos flow directly to the IVC, thus allowing oxygenated blood from the placenta to bypass the liver
What is the foramen ovale?
A small hole located in the septum, it is an anatomic adaptation in the foetus to allow oxygenated blood coming from the umbilical vein via the inferior vena cava to bypass the pulmonary circulation
What does the ductus arteriosus do?
Blood vessel connecting the main pulmonary artery to the proximal descending aorta. Allows most the blood from the right ventricle to bypass the foetus’ fluid-filled non-functioning lungs.
What is the fossa ovalis?
Depression in right atrium, remnant of foramen ovale
Where are the pulmonary arteries located?
Right side of the heart, they carry deoxygenated blood from the heart to the lungs
What do the papillary muscles and chordae tendineae do?
Once the AV valves close the muscles contract and tendinaeae tighten preventing valve flaps from everting into atria during ventricular contraction
What is endocarditis?
Infection of the endocardium
Most common is subacute bacterial endocarditis (SBE) - caused by Strep viridans or staph aureus
What is atrial fibrillation?
Rapid, irregular contraction of different parts of the atria
What is ventricular fibrillation?
Rapid, irregular contraction of the ventricles
Most disorganised form of dysrhythmia, and leads to cardiac arrest
What is the purpose of recoil in the arterial system?
To maintain arterial blood pressure during diastole
What are the 3 layers of the arterial system?
Tunica intima
Tunica media
Tunica adventitia
What are the different types of arteries and where are they found?
Elastic - aorta, pulmonary, common carotid, subclavian
Muscular - radial, femoral, coronary and cerebral
Arterioles - terminal branches supplying capillary bed
What are the characteristics of the venous system?
Low pressure
Passive movement down pressure gradient
Negative pressure in chest on inspiration
Contains valves in lower limb veins
What is normal arterial blood pressure?
120 - systolic
80 - diastolic
What are the four main control systems involved in cardiovascular control?
- Arterial blood pressure
- Cardiac output (stroke volume and HR)
- The local circulation and blood
- Extracellular fluid volume
What is the nerve that carries information from the carotid sinus to the brain?
Glossopharyngeal (hering branch)
What is the nerve that carries information from the aortic arch to the brain?
Vagus nerve
Where are the CVS baroreceptors located?
Carotid sinus and aortic arch - respond to stretching
Carotid more important - more sensitive (60-180)
Input to Nucleus tractus solitari
What is the response to a decrease in arterial pressure?
Decrease in arterial baroreceptors firing
- Increase SNS outflow to heart/arterioles/veins
- Decrease PNS outflow to heart
What does the alpha2 subsection of the NTS do?
Inhibits Bulbar circulatory centres
Activates Vagal nucleus
What does the beta1 section of the NTS do?
Activates bulbar circulatory centres
Inhibits vagal nucleus
What does the bulbar circulatory centres do?
Releases noradrenaline - acts on alpha and beta 1 receptors
- Increases peripheral resistance
- Increases CO
What does the vagal nucleus do?
Releases ACh - acts on M2 receptor
- Decreases CO
How to control arteriolar radius?
Alpha 1 - CONSTRICT
Beta 2 - DILATE
K+ - DILATE
Acetlycholine muscarinic - DILATE
What is an example of local control of BP?
Adenosine produced by metabolsing tissue
Blood gases - hyperventilation and rebreathing
Nicorandil - opens ATP sensitive potassium channels
What is capillary fluid shift?
The movement of fluid across the capillary membrane between the blood and the interstitial fluid compartment
Caused by reduced proximal capillary hydrostatic pressure
When is blood pressure greatest and lowest?
Greatest on waking, lowest in sleep
Increases in exercise, stress, sensory stimuli
Hypertension > 90mmHg Diastolic
What is primary and secondary hypertension?
Symptomless
Primary - Idiopathic (95%)
Secondary - known cause (5%) - Renal hypertension, aortic coarctation, drug induced
What are treatments of hypertension?
Reduce HR - beta adrenoreceptor antagonists
Reduce SV - beta antagonists, Calcium channel blockers
Reduce TPR - alpha blockers
Reduce volume - diuretics
Central control systems - clonidine (alpha 2 agonist)
What are the types of blood vessels in the CVS?
Large arteries Arterioles Capillaries Veins Venules
What is the function of endothelial cells?
Local BP control - constrictors (endothelin), dilators (prostacyclin)
Prevent platelet aggregation and blood clot formation (NO)
Angiogenesis+vessel remodelling
Permeability barrier
Where is smooth muscle found and what is its function?
In all BV’s but capillaries
Determine vessel radius
What is found in the tunica intima?
Endoethilium
Subendothelial layer
Internal elastic lamina
What is found in the tunica media?
Smooth muscle, collagen and ground substance
Elastin
External elastic lamina
What is found in the tunica adventitia?
Mostly collagen fibres
Elastic fibres not elastin
Fibroblasts/Macrophages
Vasa Vasorum
What is MAP?
Average pressure pushing blood round the system
MAP = DiastolicBP + 1/3PP
What is PP?
Difference between systolic and diastolic BPs
How much blood do the venules, veins and venae cavae carry?
70% - very distensible
How much blood do capillaries carry?
5% - make up 25,000 miles in total
What are the factors influencing transport within capillaries?
Blood in capillaries exert a pressure on capillary wall - hydrostatic pressure - OUT
Plasma has intrinsic osmotic pressure due to plasma proteins - COLLOID pressure - IN
Which is higher pulmonary or systemic hydrostatic pressure?
Pulmonary hydrostatic pressure is much lower
Colloid pressure is equivalent
What is an indication of heart failure to do with blood vessels?
In heart failure, capillary hydrostatic pressure increases, particularly in extremities
What is the condition where tissue fluid builds up in the tissue?
Oedema
Uses lymph capillaries and vessels to move this fluid back into blood
What is the other function of lymph apart from moving fluid from tissue to blood?
Moving absorbed fat into the circulation
How can you modify TPR and therefore MAP?
alpha-adrenoreceptor anatgonists -
alpha1-selective - PRAZOSIN - decrease vasoconstrictor tone (post-synaptic), no direct change in HR or CO
alpha2-selective - phentolamine - decrease vasoconstrictor tone (pre/post-synaptic) - not used therapeutically
What are local controls for arterioles?
Changes in O2 and Co2 can dilate arterioles
Blocking blood flow temporarily induces hyperaemia
Flow can be maintained by flow autoregulation
What is the P wave?
Atrial depolarisation
What is the QRS wave?
Ventricular depolarisation
What is the T wave?
Ventricular repolarisation
What is the P-R interval?
Delay through AV node
What is the S-T interval?
Plateau phase of AP
What are the 3 SA node AP phases?
Phase 0 - Calcium in
Phase 3 - Potassium out
Phase 4 - Calcium in and reduced potassium out
What triggers contraction in cardiac muscle?
Entrance of calcium ions
either from exterior of myocyte or from SR
What is sarcoplasmic reticulum?
Specialised ER - regulates calcium ion conc in cytoplasm of striated muscle cells
What node does the right vagus modulate?
SA
What node does the left vagus modulate?
AV
On an ECG what does the P wave represent?
P wave is a record of the electrical activity through the atria
On an ECG what does the QRS complex represent?
Movement of electrical impulses through the ventricles
On an ECG what does the ST segment represent?
When the ventricle is contracting but no electricity is flowing through it, usually appears as a straight level line between QRS and T wave.
On an ECG, what does the T wave represent?
When the lower heart chambers (ventricles) are resetting electrically and preparing for their next muscle contraction
