Circulatory System Flashcards
Arteries?
? Carry blood away from heart
Structure:
• thick & strong
• has muscles, elastic fibres and fibrous tissue
Lumen:
• narrow
Valves:
• none
Structure fits function:
• prevent bursting
• maintain high BP
• prevent back flow of blood
Capillaries?
?
• removes waste products
• provided cells with requirments
Structure of wall
• one cell thick
Lumen
• very narrow
Valve
• n/a
Structure fits function:
• strong walls not required - as most BP has been lost
• thin walls - facilitating diffusion of materials between capillaries
Veins
?
• returns blood to heart
Structure of wall
• thin
• mainly fibrous
• less elastic or muscles compared to arteries
Lumen
• wide
Valve
• yes - to prevent backflow
Structure first function
• no need to strong walls as BP has already been lost
• wide lumen - means less resistance to blood flow
What happens at the systolic phase
Chambers contract and eject blood into the arteries - active phase
What happens in the diastolic phase
Chambers relax and fill up with blood - resting phase
What is Pulse pressure?
The difference between the diastolic and systolic pressure
Are vasoactive substances endogenous or exogenous?
Endogenous
What do vasoactive substances do
They increase or decrease BP through their effects on the blood vessels
Vasoactive substances are released by..
• endothelium lining
• endocrine glands
• myoctyes
Examples of vasoconstrictors?
• catecholamines
• vaso pressin
• angiotensin II
• Thromboxane a2
Examples of vasodiablotors
• nitric oxide
• prostacylins
Equation for cardiac output ?
Cardiac output = HR x stroke volume
Define stroke volume
The volume of blood put out of the heart (via left ventricular) per heart beat
What factors contribute to the regulation of SV
• HR
• preload
• afterload
• contractibility of myocardium
• length of diastole
What facts control HR
• Body temp
• Catacolamines
• autonomic nervous system
What affects does the sympathetic nervous system have on HR and vasoconstriction or vasodilation
Sympathetic nervous system increases HR this increase vasoconstriction - norepinephrine
What affects does the parasympathetic nervous system have on HR and vasoconstriction or vasodilation
Parathympathetic nervous system decreases HR and causes vasodilation - acetylecholine
Which chemical changes signal vasodilation
• decrease oxygen
• increase: CO2, H ions& K ions
The myocardial is the thickest, where?
Left ventricle
In the ECG what does the P wave signify
Atria depolarisation
In the ECG what does the QRS wave signify
Ventricular depolarisation
In the ECG what does the T wave signify
Ventricular repolarisation
Describe the steps of cardiac conduction
- SA generates electrics signals causing atria to contract
- Electrics signals travel to AV, where they are slightly delayed before being transmitted to ventricles
- Impulses travel through bundle of his and purkinje fibres and cause ventricles to contract
- Heart relaxes, waiting for next heart beat
How does muscle contraction occur (contraction coupling)
• levels of Ca rice
• Ca binds to troponin
• a formation of cross bridges occur between actin and myosin filaments cause muscle contraction
What happens during depolarisation
Na voltage gated channels active, allowing Na to enter making it more positive
What happens during repolarisation?
Na voltage gated channels inactive and K channels open
