The Heart Flashcards
1
Q
What are cardiac muscles and what do they do?
A
- Type of striated muscle found in the wall of the heart
- Their structure allows spreading of stimuli through the heart wall
- They are myogenic, they contract without stimulation by the nervous system
2
Q
Explain the structure of cardiac muscles.
A
- Muscle has muscle fibres with myofibrils
- The cells are rich in mitochondria and glycogen granules, found close to myofibrils
- Has many short and cylindrical cells arranged in branched fibres, allows fast signals and contractions
- Muscles are connected intercalated discs
3
Q
What are intercalated discs?
A
- The attachment site between cardiac muscle cells, it appears as a linear structure diagonal to the muscle fibres
4
Q
What are the functional properties of cardiac tissue?
A
- They have a longer period of contraction and refraction, maintain heart beat
- The heart tissue does not fatigue
- Network of cells is separated between atria & ventricles, separate contractions
- Allow faster transmission of electrical signals
- Once a cell is activated, it produces maximum contraction, long refractory period, cell cannot contract again, ensure rest periods
5
Q
What is a refractory period?
A
- Time for cardiac muscle cell membrane to be ready for a second stimulus
6
Q
What are gap junctions?
A
- Densely packed protein channels that permit inter-cellular passage of ions and small molecules
- Current passes through the gap junctions to activate the heart
- Are found in intercalated discs
7
Q
What are artificial pacemakers and what do they do?
A
- Medical device that delivers electrical impulses to heart to regulate the heart rate
- Used to treat bradycardia (heart beats too slow), tachycardia (too quickly) or arrhythmia (irregular)
- Pacemaker can sense a fast or slow beat
- Connected to right atrium
8
Q
What is fibrillation and how can it be treated?
A
- Fibrillation is the rapid, irregular and unsynchronised contraction of the heart muscle fibres
- Prevents optimal flow of blood
- Defibrillator depolarises the heart tissue to terminate the unsynchronised contractions
- Return to normal sinus rhythm
9
Q
How does a defibrillator work?
A
- The defibrillator sends an electrical impulse to depolarise the heart muscle
- The electrode is a metal paddle that is placed on the patient’s chest
- A series of electrical shocks are delivered through the electrodes
- And ICD monitors heart rhythms and sends out shocks when necessary to increase or decrease the heart rhythm
10
Q
What are causes and consequences of hypertension?
A
- Hypertension is an abnormally high blood pressure, systolic, diastolic or both
- Caused by sedentary lifesytle, fat-rich diets, excessive alcohol use
- Can lead to kidney disease, stroke, blindness, arteriosclerosis, heart attack
- Long term effects caused by narrowing blood vessels
11
Q
What are causes and consequences of thrombosis?
A
- Formation of a clot within a blood vessel that forms part of the circulatory system
- Occurs in arteries when the vessels are damaged as a result of the deposition of cholesterol (reduce diameter), atherosclerosis
- Can lead to hypertension, the high blood pressure damages the arterial wall
- Plaque can rupture, restrict blood flow
- Thrombosis in coronary arteries leads to heart attacks
12
Q
How do you measure blood pressure?
A
- Pressure of blood on the walls of an artery during a systole and diastole
- Systolic pressure is higher, represents pressure of blood following the contraction of the heart
- Diastolic pressure lower, represents pressure of blood when heart relaxes between beats
- Measured with sphygomomanometer in mm/Hg
- Measures the oscillation in the blood flow caused by the pulse
- Oscillations increase in amplitude then decrease as cuff pressure falls again
Check systolic pressure and diastole pressure in book
13
Q
What is and ECG diagram and what does it monitor?
A
- Electrocardiogram checks the electrical activity of the heart
- The electrodes detect electrical changes on the skin, they are produced from muscle electrical activity due to cardiac conduction
14
Q
Explain the different sections of an ECG.
A
- A graph of voltage variations in time
- P-wave: represents depolarisation of atria in response to the electrical activity of SA node
- PR-interval delay of AV node to allow filling of ventricles
- QRS complex shows the depolarisation of ventricles, main pumping contractions, triggers signal from AV node
- ST-segment beginning of ventricle repolarisation
- The T-wave is the repolarisation of the ventricles at the end of the contraction
- Heart rate measured by no. of R-waves
15
Q
What does ventricular depolarisation and repolarisation mean?
A
- Depolarisation: contraction
- Repolarisation: relaxation
16
Q
What is the cardiac cycle?
A
- Series of events that take place in the heart over the duration of a heart beat
- Periods of contraction (systole) and relaxation (diastole) of atria and ventricles
See book
17
Q
What is epidemiology?
A
- Investigates the factors and effects that determine the presence or absence of diseases and disorders in a population
18
Q
Analyse the epidemiology data to CHD.
A
- CHD: ischemic heart disease
- CHD mortality rates worldwide have declined, yet remains major cause of death in developed countries
- Men much more effected than women
- CHD is caused in more developed countries by malnutrition, delay in onset coronary problems
19
Q
What are risk factors of CHD?
A
- Smoking, alcohol, blood pressure, obesity, genetic predisposition, exercise, sex, age
- The condition caused by the build up of plaque within the coronary arteries
20
Q
What is the function of the two nodes in the heart?
A
- The nodes regulate the heartbeat
- The beat is initiated in the sinoatrial node (SA) that sends signals to cause contraction
- The impulse spreads along the atria to the atrioventricular node (AV) and then ventricle
- There is a delay between arrival and passing on of a stimulus at the AV node, which allows atrial systole before the atrioventricular valves close
21
Q
Explain the atrial contraction and the role of the two nodes.
A
- The nodes regulate the heartbeat
- The beat is initiated in the sinoatrial node (SA) that sends signals to cause contraction
- The impulse spreads along the atria to the atrioventricular node (AV) and then ventricle
- The impulse cannot directly pass from the atria to ventricles
- There is a delay between arrival and passing on of a stimulus at the AV node, which allows atrial systole before the atrioventricular valves close
22
Q
What is the sinoatrial (SA) node and where is it positioned?
A
- Group of specialised cardiac muscle cells found where the superior vena cava joins the right atrium
23
Q
Explain the ventricular contraction and the role of the two nodes.
A
- The delay in time following the atrial systole allows for blood to fill the ventricles before the atrioventricular valves close
- The AV node sends signals down the septum that pass via specialised fibres, Bundle of His
- From the Bundle of His two Purkinje fibres branch off at every heart beat which carry the impulse at very high speed
- This impulse causes the ventricles to contract, blood flows out of the heart via aorta/pulmon.
24
Q
What do Purkinje fibres ensure?
A
- They are conducting fibres that ensure coordinated contraction of the entire ventricular wall
25
Q
What happens during the period of heart relaxation?
A
- After every contraction of the heart, there is a period of refractory (diastole)
- Allows heart to passively refill with blood between beats
- This is a long recovery period helps prevent heart tissue becoming fatigued
26
Q
How are heart sounds generated?
A
- Generated by the beating of the heart and the closing of the heart valves
- The first sound is the closing of the atrioventricular valves at the beginning og the ventricular systole (Lubb)
- Immediately after the semilunar valves close, just after the ventricular systole and beginning of the diastole causes the second sound (Dupp)
- A stethoscope is used to listen to heart sounds, acoustic device
27
Q
What is the heart rate? What factors can increase it? What factors can decrease it?
A
- The number of times the heart contracts in one minute, take ones pulse, healthy 60-100
- Gender, physical activity, body size, temperature, altitude, stress, eating, sodium and calcium ions in blood (dehydration), drugs
- Age, potassium ions
28
Q
What is the cardiac output?
A
- The amount of blood the heart pumps through the circulatory system in one minute
- Indicates how efficiently the heart can meet the demands of the body
29
Q
What is the equation for cardiac output?
A
Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV)
30
Q
How it the heart rate controlled?
A
- Controlled by nervous signals and hormonal signals
- Heart rate is increased by the sympathetic nervous system and decreased by parasympathetic stimulation
- Heart rate increased by adrenaline/epinephrine
31
Q
What is the stroke volume and what does it effect?
A
- The amount of blood pumped to the body with eat beat of the heart
- Affected by the volume of blood in body, level of resistance of blood vessels
- Changes in stroke volume can affect the blood pressure
32
Q
What is an action potential?
A
- An electrical event associated with different concentrations of ions across membranes
- The membrane action potential leads to an increase in calcium ions, it is much longer than in nerve cells
- There is a plateau of action potential in cardiac muscle, prevents heart from contracting before time
- Balance between potassium ions leaving and calcium ions coming in
- Contraction initiated by cardiac muscle cells is myogenic coordination of heartbeats
