Cardiovascular System Flashcards
What is the heart?
A hollow muscle the pumps blood
What are blood vessels (vasculature)?
They carry blood
How much blood circulates the human body?
4-6 litres of blood circulates the human body
What side of the body is the heart apex on?
Left
What side of the body is the base of the heart on
Centre of body but near the right
Where is the heart located?
Within the thoracic cavity
Surrounded by the rib cage
The lungs are positioned on the left and right sides of the heart
The apex of the heart sits just above the diaphragm
Draw a cross section of the chest including the heart, ribs, lungs, trachea and diaphragm
See lecture notes
What is the size and orientation of the heart?
The heart is a hollow muscular organ and weights between 250 and 300 grams
The apex of the heart sits by the 5th intercostal space, above the diaphragm facing towards the right hip
The base of the heart is roughly 9cm long, facing towards the right shoulder
The majority of the heart is located to the left of the midline
Draw and label a diagram of the heart
See lecture notes
Describe the process of blood being pumped around the body
See lecture notes
Which part of the heart has a thicker muscular wall?
The left ventricle
What is the function of the septum?
To separate the two halves of the heart
What is the function of valves in the heart?
They ensure a one way flow around the heart
Prevent back flow of blood between chambers
Backflow can cause a stroke, heart failure, blood clots or cardiac arrest
What is the pericardium and what is the function of the pericardium?
It is a tough fibrous tissue
It protects the heart from physical damage and over-expansion
It anchors the heart at the right position
What is the endocardium?
Smooth squamous vascular endothelium
It minimises friction as the blood flows through the heart
What is the myocardium?
Striated muscles
Cardiomyocytes: branch and connect via inter calculated discs
Blood supply to the coronary arteries (the first branches off the aorta)
Draw and label a diagram showing the wall of the heart
See lecture notes
Pericardium on outside
Myocardium in middle
Endocardium on inside
What rate cardiac muscle cells called?
Myocytes
Describe myocytes
Striated appearance
All have a nucleus
Branch
Connect via intercalated disks
Intercalated discs contain two types of cell junctions; gap junctions and desmosomes
What are desmosomes?
Strong protein fibres
Composed of complexes of adhesion proteins found on the lateral side of the cells plasma membrane
It holds cardiac muscles together during contraction
Draw and label a diagram of a desmosome
See lecture slides
Are cardiac muscle cells excitable or contractile?
They can be both
Muscle cells communicate through gap junctions
Local ionic currents flow from one muscle to the next through gap junctions
Draw and label a diagram of the heart and show the direction of blood flow
See lecture notes
What is an artery?
Any vessel carrying blood away from the heart
What is a vein?
Any vessel carrying blood to the heart
When does each atria contact?
Both at the same time
When do both of the ventricles contract?
At the same time
What does lub mean?
Mitral and tricuspid valves shut
What does dub mean?
Semilunar valves shut
Draw the systemic circuit and pulmonary circuit showing how blood travels around the body to the heart
See lecture slides
Draw the systemic circuit showing how blood travels around the body
See lecture notes
Draw the pulmonary circuit to show how blood travels to the lungs
See lecture notes
What is the vascular system?
Consists of arteries, capillaries and veins
It plays an active role in regulating blood pressure
Plays an active role in distributing blood to various tissues
Smaller arteries are called arterioles
Smaller veins are called venules
Capillaries permeate almost every tissue in the body. At any given time, 5% of circulating blood goes through the capillaries
What are small veins called
Venules
What are small arteries called?
Arterioles
What are arteries? And describe the three layers:
All arteries carry blood away from the heart
All arteries carry oxygenated blood except form the pulmonary attires which carry deoxygenated blood form the heart to the lungs
The three layers:
Innermost layer: Tunica Intima
- made of simple squamous epithelium called endothelium
- the only part that is in contact with blood
Middle layer: tunica media:
- made of smooth muscle and elastic connective tissues
- involved in the maintenance of normal blood pressure
Outer layer: tunica externa
- made of strong fibrous connective tissues
- provides support and protection
What are veins? Describe the layers
All veins carry blood to the heart
Veins carry deoxygenated blood from tissues to the heart however, pulmonary veins carry oxygenated blood from the lungs to the heart
3 layers:
The inner layer: Tunica intima
- smooth endothelium
The middle layer: tunica media
- thin layer of smooth muscle
The outer layer: tunica externa
- thin layer of fibrous connective tissue
Discuss the differences between an artery, a vein and a capillary
Artery: Thick outer wall Small lumen Thick layer of muscles and elastic fibres Thicker due to higher blood pressure
A vein:
Thin layer of muscle and elastic fibres
Large lumen
Fairly thin outer wall
A capillary:
Very small lumen
Wall made of a single layer of cell
What are capillaries?
They carry blood from arterioles to venules
Capillaries are exchange sites of materials (nutrients, waste)
Their walls are thin - simple squamous epithelium lining
They have contractile cells called pericytes
Draw and label a cross section of a capillary:
Remembered
Pericyte
Basal membrane
Epithelial cell
See lecture notes
Draw and label a diagram showing how blood is supplied to the heart
See lecture notes
Draw and label a diagram showing the electrical conduction in a heart
See lecture notes
What is the intrinsic conduction system in the heart
Internal regulating system responsible for rhythmic contraction of the heart
Consists of auto-rhythmic cells: Sinoatrial (SA) node - specialised myocardial tissue Internodal tracts Atrioventricular (AV) node AV bundle (bundle of his) Bundle branches Purkinje fibres
The SA node depolarises spontaneously, it fires at regular intervals generating the sinus rhythm
SA node is the pacemaker of the heart
Name the auto-rhythmic cells
sinoatrial (SA) node - specialised myocardial cells
Internodal tracts
Atrioventricular (AV) node
AV bundle (bundle of his)
Bundle branches
Purkinje fibres
How is sinus rhythm generated?
SA node depolarises spontaneously, it fires at regular intervals which generates the sinus rhythm
Which part is the pacemaker of the heart
The SA node
What is the average beats per minute of the heart?
60-70 beats per minute
Explain the intrinsic conduction system of the heart
Use a Diagram to help
See lecture notes
Name the two factors which affect heart rate:
The sympathetic nervous system increases heart rate
The parasympathetic nervous system decreases heart rate
What neurotransmitters of the sympathetic nervous system increase heart rate?
Adrenergics
Norepinephrine
What neurotransmitters of the parasympathetic nervous system reduce heart rate?
Cholingeric
Acetylcholine
Draw and label a diagram showing how the parasympathetic and sympathetic nervous system impact heart rate
What is the resting membrane potential?
Inside cell negative voltage (mV) with reference to the outside
What is action potential?
Sequence of electrical changes due to movement of ions through channels - includes depolarisation and depolarisation
What three ion channels are found in the heart?
Sodium channel
Potassium channel
Calcium channel
Describe action potentials of cardiac auto-rhythmic cells
Unlike non-pacemaker action potentials in the heart, and most other cells that elicit action potentials (e.g. nerve cells and muscle cells) the depolarising current is carried into the cell primarily by relativity slow Ca++ currents instead of the fast Na+ currents
Slower action potentials mean an unstable resting potential
What is the depolarisation phase?
Once the pacemaker potentials reaches threshold, Ca++ channels open
A rapid influx of Ca++ occurs, leading to a self-induced action potential
What is the depolarisation phase?
Falling phase of the action potential because rapid release of K+ due to the activation of the K+ channels
How does the myocardium communicate through gap junctions?
Allows cytoplasmic connections between two cells
Facilitate the spread of action potentials from one cell to another
Ensures all cells contract as a single co-ordinated unit
Draw and label a diagram showing the impulse conduction through the heart
See lecture notes
What does ECG mean and what does it do?
Electrocardiogram
Measure the electrical activity of the heart
Draw and label a normal ECG
What is the P wave on an ecg?
Is the first positive deflection on the ECG
Lasts about 0.08 seconds
Results from movement of the depolarisation wave from the SA node
Represents atrial depolarisation
What is the PR segment in a normal ECG?
Is the flat, usually isoelectric segment between the end of the P wave and the start of the QRS complex
Atrial depolarisation complete and the impulse is delayed at the AV node
What is the QRS complex?
Results from ventricular depolarisation (begins at the apex) and precedes ventricular contraction
Atrial depolarisation occurs
Average duration is 0.08s
What is the ST segment?
Is the flat, isoelectric section between the end of the QRS complex and the beginning of the T wave
It represents the interval between ventricular depolarisation and depolarisation
What is a T wave in an ECG?
The T wave is the positive deflection after each QRS complex
It presents ventricular re-polarisation
Ventricular re-polarisation begins at the apex
What is the TP interval?
Time during which the ventricles are relaxing and filling
Draw and label a diagram showing what happens to ventricles and atrial during systole and diastole conditions
See lecture notes
What does systole and diastole mean?
And where do these events take place?
In the ventricles
Systole: period of ventricular contraction and blood ejection
Diastole: ventricular relaxation and blood filling
How long is systole and how long is diastole?
How long does the cardiac cycle last in a patient with a typical heart rate?
Systole: 0.3 seconds
Diastole: 0.5 seconds
For a typical heart rate of 72 bpm, the cardiac cycle lasts 0.8 seconds
What are the four basic principles of the cardiac cycle?
1: blood flows from higher to lower blood pressure
2: contraction increases the pressure
3: relaxation decreases the pressure
4: valves open/close according to pressure gradients
When do the AV valves open and close?
The AV valves open when pressure is higher in the atria and close when the pressure gradient is reversed
When do the semilunar valves open?
The semilunar valves open when ventricular pressures are higher than aortic and pulmonary pressures
What is cardiac output?
The volume of blood each ventricle pumps expressed in litres/minute
What does heart rate mean?
Number of heart beats per minute
What does stroke volume mean?
Volume of blood ejected from each ventricle during systole (litres/beat)
What is the equation to find out cardiac output?
CO = HR x SV
Co: cardiac output
Hr: Heart rate
SV: stroke volume
How do you calculate the factors that affect stroke volume?
Sv: volume of blood pumped out of each ventricle during each heart beat (litre/beat)
Sv represents the difference between end diastolic volume (EDV) and end systolic volume (ESV)
SV= EDV - ESV
EDV= volume of blood in each ventricle at the end of ventricular diastole
ESV= volume of blood in each ventricle at the end of the ventricular systole
The relationship between SV and EDV is known as frank-starling mechanism
How does preload affect stroke volume?
Preload: the degree to which the myocardium is stretched before contraction
Determined by venous return and EDV
The bigger the EDV, the higher the preload, the higher the SV
The greater the end diastolic volume, the greater the stretch and the more forceful the contraction will be
How does after-load affect stroke volume?
After load: the peripheral resistance that the contracting ventricular muscle has to work against when it is ejecting blood
Back pressure exerted but arterial blood in aorta and pulmonary artery
In healthy individuals, after load is relativity constant
The higher the afterload, the higher the ESV, the lower the SV
What factors affect cardiac output:
1: autonomic nervous system
Sympathetic: increases heart rate
Parasympathetic: decreases heart rate
2: chemicals
Noradrenaline
Acetylcholine
Pressure that the blood exerts on the walls of the vessels that contain the blood (mmHg)
Blood pressure is the measurement of force applied to artery walls
What does systole mean?
Period of ventricular contraction and blood ejection
What does diastole mean?
Ventricular relaxation and blood filling
What is systolic pressure?
The pressure that blood exerts on the arterial wall when the ventricles of the heart contract to pump blood out
What is diastolic pressure?
The pressure blood exerts on the arterial wall when ventricles of the heart are relaxed
What is the systemic blood pressure?
120/80mmHg
What is pulmonary blood pressure?
25/8mmHg
What is venous blood pressure?
E.g. the top of the arm
Approximately 6-8 mmHg
What is the blood pressure in capillaries?
Arterial end of the capillary
Roughly 32 mmHg
Venous end of the capillary:
12mmHg
How is blood pressure calculated?
Blood pressure (BP) = cardiac output (CO) x peripheral vascular resistance (PVR)
BP = CO x PVR
What is the equation for cardiac output?
Cardiac output (CO) = Heart rate (HR) x stroke volume (SR)
How is stroke volume calculated?
Stroke volume (SR) =end diastolic volume (EDV) - end systolic volume (ESV)
What is the definition of hypertension?
High or raised blood pressure, is a condition in which the blood vessels have persistently raised pressure
What are the risk factors of hypertension?
Male
Genetic
Family history
Excessive salt intake
Excessive alcohol intake
Unhealthy diet
Sedentary lifestyle
Obesity
Stress
What does the NICE guidelines recommend if a patients blood pressure is over 140/90mmHg
Offer ambulatory blood pressure monitoring (ABPM) to confirm the diagnosis of high blood pressure
What is ABPM?
Ensure that at least two measurements per hour are taken during the persons usual waking hours
Or 24 hour monitoring at home (HBPM)
Persistent high blood pressure can increase the risk of a number of serious and potentially life threatening health conditions, such as?
Heart disease Stroke Heart attack Herbert failure Aortic aneurysms Kidney disease Vascular dementia
What are some anti-hypertensive drugs?
Calcium channel blockers e.g. nifedipine
Beta adrenergic receptor blockers e.g bisoprolol
Angiotensin converting enzyme inhibitors (ACE) e.g. ramipril
Angiotensin II (Ang-II) receptor antagonists e.g. loser tan
Diuretics e.g. indapamide
If a blood pressure is less that 120 systole and less than 80 diastole,
What blood pressure rating does the patient have?
Normal
A patients systole blood pressure is 120-139 and diastole 80-89.
Do they have high blood pressure?
They have prehypertension
A patients systole blood pressure is 140-159 and diastole 90-99
Do they have high blood pressure?
They have high blood pressure (hypertension) stage 1
A patients systole blood pressure is 160 or higher and diastole 100 or higher
Do they have high blood pressure?
They have high blood pressure (hypertension) stage 2
A patients systolic blood pressure is over 180 and diastolic is over 110
Do they have high blood pressure?
The patient is in hypertensive crisis
Emergency care is needed
