Ch26: The Heart And Blood Vessels Flashcards
Do small organisms have circulatory systems?
Why do we need a circulatory system?
-Small organisms (e.g. amoeba) have no circulatory systems, and use diffusion to transport nutrients instead
-Larger organisms need circulatory systems to supply cells with materials they require
What are the 2 types of circulation? Explain them
-Open blood system: heart pumps blood into open ended blood vessels, e.g. crabs, snails
-Closed circulatory system: blood remains in a continuous system of blood vessels, e.g. humans
What are the advantages of a closed system?
-Blood can be pumped around the body faster, which allows nutrients and oxygen to reach cells faster causing the animal to be more active
-Allows blood flow to different organs to be increased or decreased, e.g. more blood can be supplied to leg muscles when running
What is the composition of the human circulatory system?
-Blood
-Heart
-Blood vessels
Explain arteries
-Carry blood away from the heart
-Carry blood under high pressure
-Have a thick muscle layer
-Have a narrow lumen
Describe arterial bleeding
-Spurting
-Bright red blood
-Can bleed to death in minutes
Explain veins
-Carry blood to the heart
-Carry blood under low pressure
-Have a thinner muscle layer
-Have a wide lumen
Describe venous bleeeding
-Steady flow
-Maroon coloured blood
Describe and explain the layers in the walls of blood vessels
- Outer layer of tough, inelastic protein (collagen)
-Prevents the walls from over-expansion - Middle layer of muscle and elastic fibres
-Allows vessels to expand during exercise or when we are hot
-Elastic fibres return vessel to shape when muscle relaxes - Inner single layer of cells called endothelium
What is blood pressure?
The force of the blood exerts against the wall of the blood vessels
Explain blood pressure in arteries
-Blood pressure is highest in arteries when the heart contracts
-This pressure causes the artery to expand slightly and is detected as a pulse
Explain blood pressure in veins
-Blood pressure in veins is low
-Blood flow is slow
-When skeletal muscles contract, they squeeze on the veins to push the blood along
-Valves prevent backflow
Name 3 smaller blood vessels
-Arterioles: connect arteries and capillaries
-Venules: connect capillaries and veins
-Capillaries: tiny vessels that link arteries and veins, made of a single layer of endothelial cells
Where is the heart located?
Between the 2 lungs, slightly to the left
What is the heart made of?
-Made of cardiac muscle, surrounded by a double membrane called the pericardium
-Pericardial fluid between the membranes reduces friction during heartbeat
What type of muscle is cardiac muscle
Cardiac muscle is involuntary muscle, that is slow to fatigue
Name the parts of the heart
-Pulmonary artery
-Pacemaker
-Right atrium
-Vena cava
-Tricuspid valve
-Right ventricle\
-Pericardium
-septum
-Semilunar valves
-Cardiac muscle
-Aorta
-Pulmonary vein
-Left atrium
-Bicuspid valve
-Left ventricle
Describe the structure of the atria
Atria have thin walls as they only pump blood a short distance to the ventricles
Where does each ventricle pump blood to?\
-Right ventricle to lungs
-Left ventricle to head and body
Describe the structure of ventricles
Wall of left ventricle is thicker as blood travels further from left ventricle
What separates the atria and ventricles?
-Separated b valves which are held in place by tendons (chordae tendineae)
Describe the overall function and individual function of valves
-Overall: prevent backflow in the heart
-Semi-lunar: prevent backflow into heart
-Tricuspid: prevent backflow into right atrium
-Bicuspid: prevent backflow into left atrium
Describe the flow of deoxygenated blood in the heart
-Enters through the vena cava into the right atrium
-Then moves into the right ventricle
-Before leaving through the pulmonary artery
Describe the flow of oxygenated blood in the heart
-Enters through the pulmonary veins into the left atrium
-Then moves into the left ventricle
-Before leaving through the aorta
What are the two parts of the double circulation circuit? Where do they pump blood?
-Pulmonary circuit: to the lungs and back to the heart
-Systemic circuit: to the head and body and back to the heart
Which part of the double circulation circuit is longer?
Systemic circuit is longer so the walls of the left ventricle are thicker
What are the advantages of double circulation?
-Allows separation of oxygen-rich and oxygen-poor blood
-Ensures blood pressure is high enough to reach all parts of the body
What is the portal system?
A blood pathway that begins and ends in capillaries
What does the hepatic portal vein connect?
The stomach and the intestines to the liver
Where do the coronary arteries branch from?
Branch from the aorta just above the semi-lunar valves
What do the coronary arteries do?
-Supply heart with blood
-Drains blood from heart muscle
-Return blood directly to the right atrium
What does blockage of coronary arteries cause?
-Chest pain called angina and sometimes heart attack
What is pulse?
THe alternate expansion and contraction of arteries
What causes a pulse?
When the left ventricle contracts a wave of expansion, followed by contraction by the elastic walls, passes along all the arteries
Where can pulse be best felt?
-Wrist (radial pulse)
-Neck (carotid pulse)
What is the average adult pulse, and the normal range?
-Average adult pulse is 72bpm
-Normal range 60-100bpm
What is blood pressure?
The force exerted by the blood against the walls of the blood vessels (mainly arteries)
How does blood pressure change?
-As blood passes from the aorta to capillaries and veins, the pressure drops
How is blood pressure measured?
By recording the pressure required to stop the blood flow in the major artery of the upper arm
-the higher value records the pressure as a pulse passes through the artery (systolic pressure)
-The lower value records the pressure in between pulses (diastolic pressure)
What causes high blood pressure?
Blockages in blood vessels
What is a diastole?
When the heart chambers relax
What is a systole?
When the heart chambers contract
How does smoking effect the circulatory system?
-Nicotine increases heart rate and blood pressure, which increases workload on the heart
-Carbon monoxide reduces the amount of oxygen carried by the blood, which reduces energy levels
-Other chemicals increase the likelihood of blood clots, lung cancer, bronchitis etc.
How does diet effect the circulatory system?
-Fats increase cholesterol levels which can cause blockages in blood vessels and lead to heart attacks and strokes
-High salt intake causes high blood pressure
-Being overweight contributes to high blood pressure and heart attacks
How does exercise effect the circulatory system?
-ENlarges and strengthens heart
-Improves overall circulation and reduces body weight
-Aerobic exercises increases the amount of oxygen we transport
Pacemaker
1. Function
2. Location
3. How it works
- Controls heartbeat
- Right atrium
- The pacemaker sends a signal to the atria, which contracts and further causes the ventricles to contract
The brain can cause the pacemaker to speed up or slow down
Explain a detailed description of heartbeat control
- The pacemaker (SA Node) signals to the atria to contract
- THe signal from the SA node stimulates the AV node (located further down the right atrium)
- AV node sends a signal down the septum
- The signal passes out the walls of the ventricles, causing them to contract
What influences heart rate?
-Exercise, temperature and emotion increase heartrate
-Relaxation, sleep and alcohol decrease heart rate
What are the 3 stages of heartbeat?
- Blood enters the heart
- Blood is pumped from atria to ventricles
- Blood leave the heart
Explain the 1st stage of a heartbeat
-Atria and ventricles are relaxed
-Blood enters atria
-All valves are closed
Explain the 2nd stage of a heartbeat
-Electrical impulses from pacemaker causes atria to contract
-Blood is pumped into ventricles
-Bicuspid and tricuspid valves open
-Vena cava and pulmonary veins close to stop blood from entering atria
-Semilunar valves remain closed
Explain the 3rd stage of a heartbeat
-Atria relax
-Impulses from AV node contract ventricles
-Blood is forced out of the heart into the pulmonary artery and aorta
-The semi-lunar valves open
-The pressure closes the bicuspid and tricuspid valves
-Ventricles relax
-Semi-lunar valves close
-Vena cava and pulmonary veins open and the cycle repeats
