Cardiovascular System Flashcards
How many litres of blood does the body circulate?
5L
What are the 2 major types of blood vessels?
Veins - transport blood to the heart
Arteries - transport blood away from the heart
Which blood vessel type bificate?
Arteries bificate into smaller arteries and then eventually into arterioles.
What do arterioles drain into?
Capillaries
What do capillaries drain into?
Venules
What do venules drain into?
Veins and back to the heart
What does the blood transport(5)?
Oxygen
Nutrients
Hormones
Carbon dioxide
Cellular waste products
What are the 2 components of the circulatory system?
- blood circulatory system
- lymphatic system
What percent of fluid that passes through the capillaries into the tissues, is returned?
90%
What happens to the 10% of the tissue fluid that remains in the tissues?
Drains back into lymphatic capillaries > into lymphatic vessels > into vena cava
What do lymphatic vessels look like?
Veins
How does the heart pump blood around the body?
By the contraction of cardiac muscle
What drives/fuels the contraction of the cardiac muscle?
ATP produced by aerobic respiration
What is the major source of energy for the heart?
Lactate / lactic acid
From anaerobic respiration
Where is the heart located?
Behind sternum
How big is the heart?
12-14 cm (size of clenched fist)
Extends from 2nd to 5th rib
How much does the heart weigh?
250 - 350 g
What does the systemic circulatory system include?
Arteries and arterioles in the head and neck.
These drain into the superior vena cava
Blood from the lower region of the body returns to the heart via the….
Inferior vena cava
Where does returned blood in the vena cava go?
The right atrium
The systemic system provides oxygenated blood to all tissues in the body except……
Lungs
What does the pulmonary system do?
Supplies the lungs with deoxygenated blood from the right ventricle via the pulmonary artery
Which is the only artery that transports deoxygenated blood?
Pulmonary artery / pulmonary trunk
What is the name of the only vein that transports oxygenated blood?
Pulmonary vein - takes oxygenated blood from the lungs to the heart
Why is the left ventricular wall really thick?
It’s a high pressure environment and blood needs to be pumped to the entire systemic circulatory system
What causes high pressure in the systemic circulatory system?
Thick arterial walls and thin lumen combined with lots of capillaries (these increase resistance to flow)
Where is the tricuspid value found?
On right hand side of heart
Where are the bicuspid valves found?
On the left hand side of the heart
What is the function of the bicuspid and tricuspid valves?
Prevent backflow of blood from ventricles into atria
Where are the semi lunar valves found? What do they do?
Pulmonary artery and aorta
Stop blood flowing back into heart
How many pulmonary veins are there? What do they do?
4
Carry oxygenated blood back into the left atrium of the heart
What does the aorta do?
Carries oxygenated blood through the systemic system to the tissues
How many layers does the heart wall have?
3
What is the name of the innermost layer of the heart?
Endocardium - formed by squamous endothelial cells
Squamous = thin flat
What is the middle layer of the heart called?
Myocardium - contains cardomyocytes (cardiac muscle)
Thickest layer
Myo = muscle
What is the name of the outermost layer of the heart?
Epicardium (aka visceral pericardium) - thin layer of connective tissue. Contains coronary arteries
What surrounds the 3 layers of the heart?
Pericardial sac - filled with fluid that lubricates the membrane which helps the heart move
What can an infection of the pericardial lead to?
Swelling / inflammation which makes contraction of heart harder
What are the 3 circuits of the cardiovascular system?
1) pulmonary circuit (lungs)
2) systemic circuit (rest of body)
3) Coronary circuit (heart)
What is the coronary circulation associated with?
The coronary arteries - supply blood to the heart muscle
What are the 2 main coronary arteries?
The right and left - form a ring like a crown
What do the braches of the right and left coronary arteries do?
They sit within fat deposits in the sulci of the heart
The fat acts as an energy source
What are sulci?
Groves between chambers of the heart
What is systole?
Contraction if the heart
What is diastole?
Resting of the heart
Describe the process of blood traveling in coronary system
Heart contracts > blood vessels are squeezed > blood is forced from coronary arteries out down towards the tissues > blood drains into venous system > back into coronary sinus > contraction of heart leads sinus back into right atrium > heart relaxes and blood is pulled back into the coronary arteries due to pressure
What is dorsal?
Top
What is ventral?
Front
What is the histology of heart muscle?
Made up by cells single branched striated muscle cells called the cardiomyocytes
What are the characteristics of heart muscle cells?
- Highly branched
- Rich in mitochondria (lots of APT generation)
-contain a nucleus - connected together at intercalated discs containing gap junctions
What are gap junctions in heart muscles cells formed from?
conexin - membrane spanning proteins
What is the function of gap junctions in heart muscle cells?
Their connexin rod like structures, pass through adjacent membranes forming a channel large enough to allow for rapid transmission of electrical impulses between cells.
-This enabling synchronized contraction of the heart
What are the 4 pacemakers of the heart?
- Sinoatrial node
- AV node
- Bundle of His
- Purkinje fibres
What does the sinoatrial node contain?
Pacemaker cells - 100 potentials per minute innate firing rate
Where is the AV node located?
Just anterior to the opening of the coronary sinus
What does the AV node do?
Provides the only point of electrical contact between the atria and the ventricles - with an innate firing rate of 40-60 potentials/min
Where does the bundle of His extend to?
From AV node down into the ventricular septum where it divides into two bundles, the left and right. These then extend down to the apex of the heart.
What are the Purkinje fibres?
Large diameter extensions of the bundle of His
Extend from the apex of the heart up into the ventricular walls
What is the innate firing rate of the Bundle of His and Purkinje fibres?
20-35 potentials/min
Does a pacemaker cell have a steady resting membrane potential?
NO!
What is a pacemaker potential?
Slow depolarizations that precede each action potential in pacemaker cells
What happens after an action potential?
The membrane immediately begins to depolarise until threshold is reached and another AP is triggered
What brings about pacemaker potentials in pacemaker cells?
Changes in the permeability of the cell membrane to Na+, K+, and Ca2+ ions
What does the P wave correspond to in the ECG?
Atrial depolarization
When does the P wave occur in the cardiac cycle?
Just before atrial contraction begins
What does the QRS complex correspond to in the ECG?
Ventricular depolarization - Begins just before isovolumetric contraction
What does the T wave represent in the ECG?
It represents ventricular repolarization - takes place during the reduced ejection
What is the duration of the cardiac cycle?
0.8 seconds
What is cardiac output defined as?
The volume of blood pumped by each ventricle per unit time
What are the most commonly used units to express cardiac output?
litres per minute (L.min-1)
What is the formula to calculate cardiac output?
(CO) = Heart Rate (HR) x Stroke Volume (SV)
What is the heart rate and stroke volume for a “standard” 70 kg male at rest?
Heart rate = 75 beats.min-1
Stroke volume is around 70 mL
What are the two branches of the autonomic nervous system that innervate the SA node?
sympathetic (S) and parasympathetic (P) branches
What transmitter is released by postganglionic S fibers?
Noradrenaline
What transmitter is released by P fibers?
Acetylcholine (ACh)
What receptors mediate the effects of S fibers?
β1-adrenoceptors
What receptors mediate the effects of P fibers?
Muscarinic receptors
Which part of the autonomic nervous system causes an increase in heart rate?
The sympathetic division
What is the term for an increase in heart rate?
TACHYCARDIA
Which part of the autonomic nervous system causes a decrease in heart rate?
The parasympathetic division
What is the term for a decrease in heart rate?
BRADYCARDIA
What are the two most fundamental heart sounds?
S1 and S2
What causes the first heart sound (S1)?
The closure of the AV valves
Tensing of the valves and muscles during contraction (Lub)
What causes the second heart sound (S2)?
The closure of the semilunar valves (Dub).
Where in the systemic blood pressure, is the pressure the greatest?
Closer to the pump
What does blood flow along?
A pressure gradient
What causes pressure in vessels?
Flow which is opposed by resistance
Where is systemic blood pressure greatest?
Aorta
Where is systemic blood pressure lowest?
In the right atrium - 0 mmHg
Where is the steepest drop in pressure in the circulation?
In the arterioles, which offer the greatest resistance to flow.
What are the heart contractions synchronised by gap junctions to do?
- Completely empty the heart
- Prevent blood getting trapped in the ventricle
What is disrithmia?
When the atria and ventricles don’t have a synchronised contraction
What is one of the first symptoms people with disrithmia encounter?
Loss of time - insufficient oxygen is supplied to the brain
What membrane potential are individual pacemaker cells maintained at?
-65 to -70 mV
What is the sympathetic nervous system associated with?
Fight or flight - heart rate increases
What happens to the heart rate during stimulation of the parasympathetic nervous system?
Heart rate decreases - makes membrane less leaky, so it takes longer to reach threshold and fire an action potential
Where are the parasympathetic cell bodies located?
Medulla oblongata - extend long axons to peripheral ganglia (which are located close to target tissue)
What mediates the communication between preganglionic neurons and ganglionic neurons in parasympathetic nervous system?
Acetylcholine (ACh) binding to muscarinic and nicotinic receptors
These makes ganglionic neurons fire action potentials
Normal systolic and diastolic blood pressure
Systolic = 120
Diastolic = 80
