Cardiovascular System

Question 1

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

Answer 1

5.0-25.0L/min

Question 2

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

Answer 2

0.75L/min

This doesn’t change with exercise

Question 3

Which organs require a constant blood flow?

Answer 3

Heart muscle
Brain
Kidneys

Question 4

What is capacitance in terms of the CVS?

Answer 4

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.

Question 5

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

Answer 5

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

Question 6

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

Answer 6

Heart
Large/elastic arteries
Conducting/muscular arteries
Arterioles
Metarterioles
Capillaries
Post capillary venules
Venules
Veins
Large veins

Question 7

Name the three layers in blood vessels.

Answer 7

Tunica intima (closest to lumen)
Tunica media
Tunica adventitia

Question 8

What are vasa vasorum?

Answer 8

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

Question 9

Describe the tunica intima in an elastic artery.

Answer 9

Endothelial cells

Narrow subendothelium of connective tissue with discontinous internal elastic lamina

Question 10

Describe the tunica media of elastic arteries

Answer 10

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

Question 11

Describe the tunica adventitia of elastic arteries.

Answer 11

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

Question 12

Describe the tunica intima of muscular arteries

Answer 12

Endothelium
Subendothelial layer
Thick internal elastic lamina

Question 13

Describe the tunica media of muscular arteries

Answer 13

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

Question 14

Describe the tunica adventitia of muscular arteries

Answer 14

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

Question 15

At what diameter does an artery become an arteriole?

Answer 15

0.1mm

Question 16

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

Answer 16

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.

Question 17

What are metarterioles and how are they different to arterioles?

Answer 17

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.

Question 18

Describe capillaries.

Answer 18

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)

Question 19

What are continous capillaries?

Answer 19

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

Question 20

What are fenestrated capillaries?

Answer 20

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

Question 21

What are sinusoidal capillaries?

Answer 21

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.

Question 22

What are discontinuous sinusoidal capillaries and where are they found?

Answer 22

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

Question 23

What are post capillary venules?

Answer 23

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.

Question 24

Describe venules.

Answer 24

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

Question 25

Describe veins.

Answer 25

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.

Question 26

Describe large veins and give an example.

Answer 26

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.

Question 27

Describe the structure of the heart.

Answer 27

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)

Question 28

Describe the features of cardiac muscle cells.

Answer 28

``` Striations Branching 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 ```

Question 29

Define systole and diastole.

Answer 29

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

Question 30

Describe the spread of excitation during systole.

Answer 30

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

Question 31

How is ventricular muscle organised?

Answer 31

It is organised into 'figure of eight' bands

Question 32

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

Answer 32

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

Question 33

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

Answer 33

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

Question 34

Explain the LUP DUP sounds of the heart.

Answer 34

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

Question 35

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? 

Answer 35

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

Question 36

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? 

Answer 36

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

Question 37

Describe the ANS receptors and effects in the heart.

Answer 37

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

Question 38

 Describe the ANS receptors and effects in the lungs. 

Answer 38

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

Question 39

Describe the ANS receptors and effects in the pupils.

Answer 39

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

Question 40

 Describe the ANS receptors and effects in the sweat glands. 

Answer 40

Sympathetic - α1 - locallised secretion                      M3  - general secretion  There is no parasympathetic innervation

Question 41

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

Answer 41

``` 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 ```

Question 42

Explain vasomotor tone.

Answer 42

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.

Question 43

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

Answer 43

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

Question 44

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

Answer 44

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