Circulatory System

Question 1

Arteries?

Answer 1

? 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

Question 2

Capillaries?

Answer 2

?
• 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

Question 3

Veins

Answer 3

?
• 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

Question 4

What happens at the systolic phase

Answer 4

Chambers contract and eject blood into the arteries - active phase

Question 5

What happens in the diastolic phase

Answer 5

Chambers relax and fill up with blood - resting phase

Question 6

What is Pulse pressure?

Answer 6

The difference between the diastolic and systolic pressure

Question 7

Are vasoactive substances endogenous or exogenous?

Answer 7

Endogenous

Question 8

What do vasoactive substances do

Answer 8

They increase or decrease BP through their effects on the blood vessels

Question 9

Vasoactive substances are released by..

Answer 9

• endothelium lining
• endocrine glands
• myoctyes

Question 10

Examples of vasoconstrictors?

Answer 10

• catecholamines
• vaso pressin
• angiotensin II
• Thromboxane a2

Question 11

Examples of vasodiablotors

Answer 11

• nitric oxide
• prostacylins

Question 12

Equation for cardiac output ?

Answer 12

Cardiac output = HR x stroke volume

Question 13

Define stroke volume

Answer 13

The volume of blood put out of the heart (via left ventricular) per heart beat

Question 14

What factors contribute to the regulation of SV

Answer 14

• HR
• preload
• afterload
• contractibility of myocardium
• length of diastole

Question 15

What facts control HR

Answer 15

• Body temp
• Catacolamines
• autonomic nervous system

Question 16

What affects does the sympathetic nervous system have on HR and vasoconstriction or vasodilation

Answer 16

Sympathetic nervous system increases HR this increase vasoconstriction - norepinephrine

Question 17

What affects does the parasympathetic nervous system have on HR and vasoconstriction or vasodilation

Answer 17

Parathympathetic nervous system decreases HR and causes vasodilation - acetylecholine

Question 18

Which chemical changes signal vasodilation

Answer 18

• decrease oxygen
• increase: CO2, H ions& K ions

Question 19

The myocardial is the thickest, where?

Answer 19

Left ventricle

Question 20

In the ECG what does the P wave signify

Answer 20

Atria depolarisation

Question 21

In the ECG what does the QRS wave signify

Answer 21

Ventricular depolarisation

Question 22

In the ECG what does the T wave signify

Answer 22

Ventricular repolarisation

Question 23

Describe the steps of cardiac conduction

Answer 23

1. SA generates electrics signals causing atria to contract
2. Electrics signals travel to AV, where they are slightly delayed before being transmitted to ventricles
3. Impulses travel through bundle of his and purkinje fibres and cause ventricles to contract
4. Heart relaxes, waiting for next heart beat

Question 24

How does muscle contraction occur (contraction coupling)

Answer 24

• levels of Ca rice
• Ca binds to troponin
• a formation of cross bridges occur between actin and myosin filaments cause muscle contraction

Question 25

What happens during depolarisation

Answer 25

Na voltage gated channels active, allowing Na to enter making it more positive

Question 26

What happens during repolarisation?

Answer 26

Na voltage gated channels inactive and K channels open