6a. Heart and blood vessels Flashcards
What is the jounrney of blood through the heart
Vena Cava - Right atrium - AV Valve - Right ventricle - SL Valve - Pulmonary artery - Pulmonary vein - Left atrium - AV Valve - Left ventricle - SL Valve - Aorta
What are the different types of circulation in a mammal
-Pulmonary circulation - deoxygenated blood from body to the lungs
-Systematic circulation - oxygenated blood to rest of the body
Why is it an advanatge to have two seperate pumps
RHS generates pressure to send blood through the lungs where pressure drops
LHS generates more pressure so the blood can travel around body at a fast enough rate
what is the function of the atrioventricular and semilunar valves
Prevent backflow of blood
AV Valves prevent backflow from V to A
SL Valves prevent backflow from arteries to ventricles
What is a cardiac cycle
One complete sequence of contraction and relaxation
What is atrial systole
The contraction of the atria
What is ventricular systole
Contraction of the ventricular muscles
What is diastole
Relaxation of the heart muscle
How does blood flow
From regions of high to regions of low pressure
What happens during diastole
Heart relaxes
Artia fill with blood from the vena cava and pulmonary veins
SL Valves are closed
AV valves close until pressure in atria is too high and forces the valves open
What happens during atrial systole
Blood fills atria from vena cava and pulmonary veins
Artial muscle contracts, increases pressure in atria over the ventricals
AV Valves forced open and blood flows into the ventricles
What happens during ventricular systole
Ventricular muscles contract
Volume of ventricles increases, decreases pressure
AV Valves close
Blood pushed upwards, towards arteries
SL Valves open, blood flows into aorta and pulmonary artery
How does the heart muscle contract
Cardiac muscle is myogenic
Contractions arise from within the cardiac muscle
Sinoatrial node (SAN) is a group of cell within the wall of the right atrium
SAN originates the initial stimulus for contraction
What is the sequence of events that controls the cardiac cycle
SA Node sends an impulse spreading across both atria causing them to contract
Impluses then reach the AV Node where it is delayed
Delay allows the atria to fully empty and the ventricles to fill with blood
Impulses then sent down to the ventricles by the bundle of His - contains specialised conducting tissue - Purkyne fibres
Impulse spread up the ventricle wall from the base via Purkyne fibres causing ventricles to contract from the base up
Blood forced up into the arteries
What is the stroke volume
The volume of blood pumped out from one ventricle during each contraction.
What is the cardiac output
the total volume pumped out from one ventricle per minute
How do you calculate cardiac output
CO (dm3min-1) = Stroke volume (cm3) x Heart rate (bpm)
What happens to the cardiac output with the effect of excerise
During exercise heart rate, stroke volume and cardiac output increase from the resting values
An athlete’s heart will get bigger over time so resting stroke volume will be bigger.
This means their resting pulse rate will drop.
This gives them more capacity to increase their cardiac output during exercise
How does cardiac ouput relate to the muscles
more glucose and oxygen to be delivered to the working muscles.
What is mass flow
The bulk movment of substances from one area to another due to differences in pressure
Why are the types of blood vessels in mammals
-Arteries - carry blood away from heart, Branch into arterioles
- Capillaries - Branch from arterioles
-Veins - carry blood towards the heart
What are arteries and veins an example of
Organs as they are a collection of different tissures working together to achieve a particular function
What are some characteristics of arteries
Carry blood at high pressure
Thick walls to withstand the high pressure
Lumen is relatively small
Walls have an inner coat of a single endothelium layer
Walls have lots of elastic tissues
During diastole, elastic recoils when pressure falls to keep the blood under pressure and pushes it along
Smooth walls to stop pressure fluctuations
What are characteristics of aterioles
Control blood flow to the capillaries
Walls have lots of muscle tissue
Walls are thinner then arteries
Walls have a single layer endothelium coat
Muscles can contract to narrow lumen and reduce blood flow (Vasoconstriction)
Muscles can relax to widen lumen and increase blood flow (Vasodilation)
During exercise - vasodiliation to muscles. Vasoconstriction to the gut.
What are characteristics of the veins
Fewer elastic tissues as low blood pressure
Walls are very thin
Walls have SL valves
Many veins run close to leg muscles which temporarily raises the pressure when muscles contract
What are characteristics of the capillaries
Rate of blood flow is reduced- allows more times for diffusion
Walls made form a single squamous endothelial cell - short diffusion pathway
Small pores in wall - Highly permeable - Many substances can be forced out forming tissue fluid
Small size but large quantity provides a large SA:vol
What happens in CHD
- Layers of fatty material (atheroma) build up inside coronary arteries
-This narrows and reduced blood flow resulting in lack of oxygen for the heart muscles
-It will build over time and can lead to thrombosis (blood clot) - Clot can block coronary artery causing a myocardial infarction, some heart tissues could be damaged and may die
What is a risk factor
Any factor that increases the probability of developing a disease. They are in correlation with disease but may not be causation
What are unavoidable risk factors for CHD
-Inheritance / genetics - history og heart disease, high BP , or high cholesterol can lead to an early CHD
-Gender - Males are more likley to suffer from heart attacks. Oestogen protects females
-Increasing age - Blood vessels tend to lose their elasticity and become narrower
What are the avoidable risk factors of CHD
-Smoking
-Diet
-High BP
How can smoking lead to CHD
Nicotine increases heart rate and acts as a vasoconstrictor, increasing BP
Can lead to atheroma and thrombosis
How can diet lead to CHD
-High blood cholesterol. Eating lots of saturated fats or cholesterol leads to elevated levels of LDL Cholesterol in the blood and can lead to atheroma
Eating less can reduce LDL levels and increase LDH levels
- Statins. Keep open narrow arteries .Reduce blood cholesterol which slows down rate of fatty deposits
-High levels of salt. Raise BP
How does high blood pressure lead to CHD
Prolonged stress, certain diets and lack of excerices leads to high BP
The higher the BP the greater risk of damage to the artery
Starting atheroma formation
High BP increase risk of thrombosis
