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Biology Option D > The Heart > Flashcards

The Heart Flashcards

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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
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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
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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
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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
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5
Q

What is a refractory period?

A
  • Time for cardiac muscle cell membrane to be ready for a second stimulus
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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
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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
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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
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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
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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
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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
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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

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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
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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
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15
Q

What does ventricular depolarisation and repolarisation mean?

A
  • Depolarisation: contraction
  • Repolarisation: relaxation
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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

Biology Option D (6 decks)

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