Cardiovascular System Flashcards Preview

ESA 2 - Jake and Ron > Cardiovascular System > Flashcards

Flashcards in Cardiovascular System Deck (44):

Give the range of blood flow delivered to the body the CVS must be able to provide.



What is the minimum blood flow required to the brain at all times?

This doesn't change with exercise


Which organs require a constant blood flow?

Heart muscle


What is capacitance in terms of the CVS?

The ability to cope with changes in cardiac output. It's a store of blood able to be called upon when there's a temporary imbalance between the venous return and cardiac output.
The blood is mostly stored in the veins.


Describe the distribution of blood volume over the major parts of the circulation.

11% in arteries and arterioles
5% in capillaries
17% in heart and lungs
67% in veins


Describe the route blood takes through the various vessels on its journey around the CVS.

Large/elastic arteries
Conducting/muscular arteries
Post capillary venules
Large veins


Name the three layers in blood vessels.

Tunica intima (closest to lumen)
Tunica media
Tunica adventitia 


What are vasa vasorum?

Vasa vasorum are capillaries supplying the walls of the arteries as they are to thick for simple diffuson of blood from the lumen.


Describe the tunica intima in an elastic artery.

Endothelial cells
Narrow subendothelium of connective tissue with discontinous internal elastic lamina


Describe the tunica media of elastic arteries

40-70 fenestrated elastic membranes
Smooth muscle and collagen between these lamellae
Thin external elastic lamina may be present


Describe the tunica adventitia of elastic arteries.

A layer of fibroelastic connective tissue containing vasa vasorum, lymphatic vessels and nerve fibres.


Describe the tunica intima of muscular arteries

Subendothelial layer
Thick internal elastic lamina


Describe the tunica media of muscular arteries

40 layers of smooth muscle cells connected by gap junctions for coordinated contraction
Prominent external elastic lamina 


Describe the tunica adventitia of muscular arteries

Thin layer of fibroelastic connective tissue containing vasa vasorum, lymphatic vessels and nerve fibres.


At what diameter does an artery become an arteriole?



Describe the srtucture of an arteriole. What is the difference between a large and a small arteriole?

Thin internal elastic lamina in larger arterioles, this is absent in smaller ones.1-3 layers of smooth muscle cells in the tunica media. External elastic lamina is absent.Tunica adventitia is scant. Large arterioles are larger than small arterioles.


What are metarterioles and how are they different to arterioles?

Metarterioles are arteries which supply blood to capillary beds.Their smooth muscle layer is not continous, instead each smooth muscle cell acts as a pre capillary sphincter.


Describe capillaries.

Capillaries are made of a single layer of endothelium and the associated basement membrane. Largest surface area for gas/nutrient exchange(600m2), RBCs fill almost entrie lumen (7-10μm) 


What are continous capillaries?

Pericytes form a branching network on the outer network of the endothelium. These cells facillitate angiogenesis.


What are fenestrated capillaries?

Pericytes are present with fenestrations in the endothelium. The fenestrations are covered by a thin diaphragm. 


What are sinusoidal capillaries?

Similar to fenestrated capillaries with larger openings which allow blood cells through the discontinous basal lamina.
Found in bone marrow, lymph nodes and the adrenal gands.


What are discontinuous sinusoidal capillaries and where are they found?

Sinusoidal capillaries which don't have tight junctions and allow for greater movement of cells and materials.
Found in liver and spleen.


What are post capillary venules?

Similar to capillaries in that they consist of only a thin endothelium and associated pericytes.
Diameter = 10-30μm
They are more permeable than capilalries and are at a lower pressure than the surrounding tissue, so fluid drains into them.


Describe venules.

As venules merge and their diameter grows (>50μm), smooth muscle cells begin to become associated with the endotheliun, Valves begin to appear.


Describe veins.

Normally larger diameter than accompanying artery
Thinner wall with more connective tissue but less elastic/muscle tissue
Well developed adventitia
Superficial veins in the legs have a well defined muscular wall to resist gravity.


Describe large veins and give an example.

Well developed longitudinal smooth muscle in tunica adventitia in addition to the circular smooth muscle in the tunica media.
Examples include: vena cavae, pulmonary vein, portal, renal, internal jugular, iliac and azygous.


Describe the structure of the heart.

4 chambers - right atrium and ventricle, left atrium and ventricle
Atrioventricular valves - tricuspid (right) and mitral (left)
Inflow vessels - superior/inferior vena cavae and coronary sinus (right), pulmonary veins (left)
Outflow vessels - pulmonary artery (right), aorta (left)


Describe the features of cardiac muscle cells.

Centrally positioned nuclei - 1 or 2
Intercalated discs
Adherens type junctions - anchor cells and provide anchorage for actin
Gap junctions
T tubules in line with Z band


Define systole and diastole.

Systole - period when the myocardium is contracting
Diastole - relaxation between contractions


Describe the spread of excitation during systole.

1. SAN fires AP which spreads over atria causing atrial systole. AP reaches AVN and delayed for 120ms
2. AP spreads down Bundle of His in septum
3. Excitation spreads from endocardial (inner) to epicardial (outer) surface
4. Ventricles contract from the apex up Insert diagram


How is ventricular muscle organised?

It is organised into 'figure of eight' bands


Which valves open during ventricular contraction and what causes them to open?

Pulmonary valve and aortic valve
They open because the intraventricular pressure is higher than that in the pulmonary artery/aorta


Which valves open during diastole an what causes them to open?

Tricuspid and mitral valves.They open becasue the atrial pressure is high than the intraventricular pressure.


Explain the LUP DUP sounds of the heart.

LUP - closing of AV valves (tricuspid and mitral) at begining of systole
DUP - closing of semilunar valves (aortic and pulmonary) at end of systole 


In the sympathetic nervous system: 
1. Where are cell bodies?
2. What is the length of the pre and post ganglionic nerve fibres?
3. What are the pre and post ganglionic neurones?
4. What are the exceptions? 

1. Thoracolumbar outflow - T1-12 and L1-2
2. Short pre, long post
3. Pre is cholinergic, post is noradrenergic
4. Perspiraton and ejactulation - post is cholinergic


In the parasympathetic nervous system: 
1. Where are cell bodies?
2. What is the length of the pre and post ganglionic nerve fibres?
3. What are the pre and post ganglionic neurones? 

1. Craniosacral outflow
2. Long pre, short post
3. Both cholinergic


Describe the ANS receptors and effects in the heart.

Sympathetic - β1 - increases rate and force of contraction
Parasympathetic - M2 - decreases rate of contraction


 Describe the ANS receptors and effects in the lungs. 

Sympathetic - β2 - relax smooth muscle in the airways
Parasympathetic - M3 - contract smooth muscle in the airways


Describe the ANS receptors and effects in the pupils.

Sympathetic - α1 - causes dilation
Parasympathetic - M3 - causes contraction


 Describe the ANS receptors and effects in the sweat glands. 

Sympathetic - α1 - locallised secretion                     
M3  - general secretion 

There is no parasympathetic innervation


State the ANS receptors, their G protein and the subsequent effector.

α1 - Gq - +phospholipase C (PLC)
α2 - Gi - -adenylyl cyclase (AC)
β1 - Gs - +AC
β2 - Gs - +AC
M1 - Gq - +PLC
M2 - Gi - -AC
M3 - Gq - +PLC


Explain vasomotor tone.

Only sympathetic nervous system - activty causes vasoconstriction by α1 adrenoreceptor. There is a baseline level of constant activty which forms vasomotor tone which varies from organ to organ.
Increased activation causes vasoconstriction.
Decreased activation causes vasodilatation.


Where are the baroreceptors and how do they influence the ANS?

Arch of aorta and carotid sinuses.
Sends signal to medulla obongata in response to stretch. The medulla oblongata then coordinates a response.
Eg. increased stretch would increase parasympathetic activty to the heart to decrease rate


Which branch of the ANS dominates the heart at rest? What role do they have in increasing heart rate?

Parasympathetic dominates at rest.
Initial increase caused by reduction in parasympathetic activity. Further increase caused by increased sympathetic activity.