circulatory systems Flashcards
What are functions of a circulatory system?
distribution of nutrients, support for metabolism, distribution of water and electrolytes, transportation of hormones
What re the two types of circulatory system?
open and closed
What are features of open systems?
fluid is open to body cavities and cells, lower pressure system, less efficient, incomplete system of vessels, haemolymph flows around the body
What system do insects use?
open - they have a tracheal system to transport nutrients and CO2
What are features of a close system?
complete system of blood vessels, intercellular spaces filled with interstitial fluid, lymph in lymphatic vessels
What are requirements of an efficient circulation system?
efficient O2 carriers in blood, efficient gas exchange in respiratory system, efficient delivery of nutrients and O2, efficient gas exchange in tissues
What is flow rate equation?
flow rate = ΔP/R
What do P and R stand for?
P = driving force R = resistance
What is the equation for R?
R = 8ηL/πr^4
What is the ΔP and R in a closed system?
ΔP is high and R is high
What is cardiac output?
the total volume of blood pumped by the heart in one minute
What is the cardiac output equation + units?
CO (L/min) = HR (bpm) x SV (L/beat)
What can we use to investigate cardiac function?
ultrasound, ECG, MRI, electrode monitoring
How does the heart generate its own rhythm?
pacemaker cells set the pace of the heart rate and generate action potentials which are conducted around the rest of the heart
On an ECG what do the P wave, QRS complex, and T wave correspond to?
P wave = atrial depolarisation. QRS = ventricular depolarisation. T wave = ventricular repolarisation
What happens in the PR interval?
conduction of the AV node
What is heart rate modified by?
autonomic nervous system and circulation hormones
What cells make the heart contract?
cardiac myocytes
What happens during EC coupling in cardiac myocytes?
an action potential occurs and calcium channels open and enter cell. causes more calcium ions to be released into the cardiac muscles so the calcium can bind to myofilaments and allow shortening of muscles to occur
What are the phases of the cardiac cycle?
systole - contraction and ejection of blood. diastole - relaxation and filling
What are the events of the cardiac cycle?
- Atrial systole (ventricular diastole)
- Isovolumic contraction of the ventricles (ventricular systole)
- Ventricular ejection
- Isovolumic relaxation of the ventricles
- Passive ventricular refilling
What is Starling’s law?
increased ventricular filling causes an increase in the forces of contraction of the ventricular muscle
Where is in the heart?
in the chest cavity, behind the sternum. on top of the diaphragm and is between the lungs
Why is the left lung smaller than the right lung?
the heart bulges into the left side
What is the pericardium?
fibrous bag around the heart - serous (visceral and parietal) and fibrous
What does the serous pericardium contain?
lubricating fluid
What is the function of the pericardium?
free movement
Which pericardium prevents the heart from over expansion?
fibrous pericardium
What is the visceral layer attached to?
the heart
What do the coronary arteries split into?
smaller vessels - anastomoses
What is bypass surgery?
when the coronary arteries become blocked - harvest veins from lower leg and sew them in the aorta and coronary artery
What are the heart chambers lined with?
the endocardium
Where is the tricuspid valve?
between right atrium and ventricle
What is the foramen ovale?
site of a flap-like valve between R and L atria
Why was the foramen ovale needed?
in the foetus blood O2/CO2 exchange occurred in the placenta. therefore, most blood bypassed the lungs by going through the foramen ovale
Where was the ductus arteriosus?
between pulmonary trunk and aorta
When does the foramen ovale close?
closes when baby takes first breath and then seals permanently
What is another name for the bicuspid valve?
mitral valve
What do the chorda tendinae do?
prevent valves inverting
What are the three layers of the heart?
endocardium (lining), myocardium (muscle layer), epicardium (visceral pericardium)
What is the structure of the endocardium?
appears ridged (trabeculae carnae) - underlying bundes of muscle fibres. made up of endothelium + underlying connective tissues
What makes up the myocardium?
cardiac muscle fibres + connective tissue
What are the three types of cell-cell junctions that link the heart muscle cells?
adherens junction links the actin cytoskeleton, desmosomes link intermediate filaments, gap junctions link cytosol
What are the components of blood vessels?
endothelium, smooth muscle, connective tissue
What does the endothelium do?
allows transfer between vessels and surroundings, keeps blood in system
What are the endothelium cells like?
thin and flat
What is the junctional complex?
bridge between cells
What are the three layers of blood vessels?
tunica intima, tunica media, tunica adventitia
What makes up the tunica intima?
endothelium + connective tissue
What makes up the tunica media?
smooth muscle and connective tissue
What makes up the tunica adventitia?
connective tissue
What surrounds the tunica media?
external elastic lamina
What surrounds the tunica intima?
internal elastic lamina
What is the arrangement of smooth muscle?
circular
What are vasa vasora?
little blood vessels in the walls of large arteries
What controls blood flow to capillary beds?
terminal arterioles
What are the three types of endothelium?
continuous (in most capillaries), fenestrated (in endocrine glands - exchanges hormones), discontinuous (found in sinusoids - exchanges whole cells)
What does the walls of a vein contain?
small tunica media, substantial tunica adventitia
What are valves?
folds on tunica intima for one way flow
What is blood pressure?
difference between pressure in the system and the ambient pressure (surrounding air, gas or liquid)
What are two components of blood or haemolymph pressure?
dynamic pressure produced by the pump, hydrostatic pressure of the fluid
What do changes in smooth muscle tone lead to?
vasoconstriction (higher resistance) and vasodilation (lower resistance)
What can smooth muscle tone be altered by extrinsically?
neurotransmitters, hormones
What can smooth muscle be altered by intrinsically?
endothelium-derived substances, metabolites, other locally-produced factors
What is total fluid energy?
potential energy acquired from the beating of the heart, kinetic energy of the fluid itself, potential energy of the fluid that it possesses because of its position in the gravitational field
What is the effect of gravity above the heart?
arteriole pressure increases with height
