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D.4 THE HEART Flashcards

1
Q

The heart is composed of

A

cardiac muscle cells which have specialised features that relates to their function

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2
Q

Cardiac muscle cells contract

A

without stimulation by the central nervous system (contraction is myogenic)

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3
Q

Cardiac muscle cells are branched

A

allowing for faster signal propagation and contraction in three dimensions

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4
Q

Cardiac muscles cells are not fused together, but

A

are connected by gap junctions at intercalated discs

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5
Q

Cardiac muscle cells have more mitochondria, as

A

they are more reliant on aerobic respiration than skeletal muscle

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6
Q

Cardiac muscle has a longer period of

A

contraction and refraction, which is needed to maintain a viable heart beat

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7
Q

The heart tissue does not become

A

fatigued (unlike skeletal muscle), allowing for continuous, life long contractions

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8
Q

The interconnected network of cells is separated between atria and ventricles, allowing

A

them to contract separately

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9
Q

The heart contains a number of hear valves

A

which prevent the backflow of blood

This ensures the one-way circulation of blood around the body

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10
Q

There are two sets of valves located within the heart

A

Atrioventricular

Semilunar

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11
Q

Semilunar

A

valves (pulmonary and aortic) prevent blood in the arteries from flowing back into the ventricles

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12
Q

Atrioventricular

A

valves (tricuspid and bicuspid) prevent blood in the ventricles from flowing back into the atria

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13
Q

Heart sounds are made when

A

the two sets of valves close in response to pressure changes within the heart

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14
Q

The first heart sound is caused

A

by the closure of the atrioventricular valves at the start of ventricular systole

lubb

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15
Q

The second heart sound is caused by

A

the closure of the semilunar valves at the start of ventricular diastole

dubb

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16
Q

The cardiac cycle describes

A

the series of events that take place in the heart over the duration of a single heart beat

It is comprised of a period of contraction (systole) and relaxation (diastole)

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17
Q

The cardiac cycle can be mapped by

A

recording the electrical activity of the heart with each contraction

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18
Q

activity of cardiac cycle is measured

A

using a machine called an electrocardiograph to generate data called an electrocardiogram

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19
Q

Each normal heart beat should follow the same sequence of electrical events:

A

The P wave represents depolarisation of the atria in response to signalling from the sinoatrial node (i.e. atrial contraction)

The QRS complex represents depolarisation of the ventricles (i.e. ventricular contraction), triggered by signals from the AV node

The T wave represents repolarisation of the ventricles (i.e. ventricular relaxation) and the completion of a standard heart beat

Between these periods of electrical activity are intervals allowing for blood flow (PR interval and ST segment)

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20
Q

Tachycardia

A

elevated resting heart rate = >120 bpm

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21
Q

bradycardia

A

depressed resting heart rate = < 40 bpm

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22
Q

Arrhythmias

A

irregular heart beats that are so common in young people that it is not technically considered a disease

23
Q

Fibrillations

A

unsynchronised contractions of either atria or ventricles leading to dangerously spasmodic heart activity

24
Q

heart conditions

A

Fibrillations

Arrhythmias

bradycardia

Tachycardia

25
Cardiac output describes
the amount of blood the heart pumps through the circulatory system in one minute It is an important medical indicator of how efficiently the heart can meet the demands of the body
26
There are two key factors which contribute to cardiac output
heart rate and stroke volume Equation: Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV)
27
Heart rate can be affected by a number of conditions
including exercise, age, disease, temperature and emotional state
28
An individual’s heart rate is controlled by
both nervous and hormonal signals: Heart rate is increased by the sympathetic nervous system and decreased by parasympathetic stimulation (vagus nerve) Heart rate can also be increased hormonally via the action of adrenaline / epinephrine
29
the body will attempt to compensate for any changes to stroke volume with
a corrective alteration to heart rate
30
The typical pulse rate for a healthy adult is between
60 – 100 beats per minute
31
Heart rate describes
he speed at which the heart beats, measured by the number of contractions per minute (or bpm)
32
Stroke volume is
the amount of blood pumped to the body (from the left ventricle) with each beat of the heart It is affected by the volume of blood in the body, the contractility of the heart and the level of resistance from blood vessels
33
Changes in stroke volume will affect the blood pressure
more blood or more resistance will increase the overall pressure
34
Systolic blood pressure is
higher, as it represents the pressure of the blood following the contraction of the heart
35
Diastolic blood pressure is
lower, as it represents the pressure of the blood while the heart is relaxing between beats
36
Blood pressure readings will vary depending on
the site of measurement (e.g. arteries have much higher pressure than veins)
37
Blood pressure can be affected by
posture, blood vessel diameter (e.g. vasodilation) and fluid retention or loss
38
Hypertension is defined
as an abnormally high blood pressure – either systolic, diastolic or both (e.g. > 140/90 mmHg)
39
Common causes of hypertension include
a sedentary lifestyle, salt or fat-rich diets and excessive alcohol or tobacco use
40
High blood pressure can also be
secondary to other conditions (e.g. kidney disease) or caused by some medications
41
Hypertension itself does not cause symptoms but
in the long-term leads to consequences caused by narrowing blood vessels
42
Thrombosis is
the formation of a clot within a blood vessel that forms part of the circulatory system
43
Thrombosis occurs in
arteries when the vessels are damaged as a result of the deposition of cholesterol (atherosclerosis)
44
Atheromas | thrombosis
(fat deposits) develop in the arteries and significantly reduce the diameter of the vessel (leading to hypertension)
45
The high blood pressure damages | thrombosis
the arterial wall, forming lesions known as atherosclerotic plaques
46
If a plaque ruptures | thrombosis
blood clotting is triggered, forming a thrombus that restricts blood flow
47
If the thrombus becomes dislodged | thrombosis
it becomes an embolus and can cause blockage at another site
48
Thrombosis in the coronary arteries leads to
heart attacks, while thrombosis in the brain causes strokes
49
There are several risk factors for coronary heart disease (CHD), including:
Age – Blood vessels become less flexible with advancing age Genetics – Having hypertension predispose individuals to developing CHD Obesity – Being overweight places an additional strain on the heart Diseases – Certain diseases increase the risk of CHD (e.g. diabetes) Diet – Diets rich in saturated fats, salts and alcohol increases the risk Exercise – Sedentary lifestyles increase the risk of developing CHD Sex – Males are at a greater risk due to lower oestrogen levels Smoking – Nicotine causes vasoconstriction, raising blood pressure Mnemonic: A Goddess
50
An artificial pacemaker is
is a medical device that delivers electrical impulses to the heart in order to regulate heart rate Modern pacemakers are externally programmable, allowing cardiologists to make adjustments as required
51
Artificial pacemakers are typically used to treat one of two conditions:
Abnormally slow heart rates (bradycardia) | Arrhythmias arising from blockages within the heart’s electrical conduction system
52
Fibrillation is
he rapid, irregular and unsynchronised contraction of the heart muscle fibres This causes heart muscle to convulse spasmodically rather than beat in concert, preventing the optimal flow of blood
53
Fibrillation is treated by
applying a controlled electrical current to the heart via a device called a defibrillator This functions to depolarise the heart tissue in an effort to terminate unsynchronised contractions Once heart tissue is depolarised, normal sinus rhythm should hopefully be re-established by the sinoatrial node

Biology (40 decks)

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