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CGIER 2-4 > CGIER 4 - The Heart: Structure, Physiology, Cardiac Cycle, Arterial Blood Pressure. > Flashcards

CGIER 4 - The Heart: Structure, Physiology, Cardiac Cycle, Arterial Blood Pressure. Flashcards

1
Q

The heart is the organ responsible for the _____________ of the blood.

A

circulation

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2
Q

Found in the thorax in a cavity of its own called the…

A

pericardium

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3
Q

The pericardium is lined by a layer of simple squamous epithelium called ______________ - forming part of the pericardial membrane.

A

mesothelium

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4
Q

The outer covering of the heart, the _________________, is covered by a mesothelium

A

epicardium

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5
Q

Cardiac muscle is __________ but arranged into individual cells separated by areas of _______________.

A

striated, intercalated discs

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5
Q

What are intercalated discs?

A

These are special membranes with numerous gap junctions allowing a free diffusion of ions from cell to cell.

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6
Q

Heart rate is regulated by the…

A

cardiovascular/cardiac centre in the medulla oblongata which responds to pressure receptors in the walls of blood vessels and other stimuli.

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7
Q

The adult human heart normally contract at about…

A

72 beats/min

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7
Q

The SA node or pacemaker consists of…

A

a modified cardiac muscle mixed with nerve fibres of the autonomic nervous system (i.e. Sympathetic and Parasympathetic [Vagus nerve, cranial nerve X] nervous systems).

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8
Q

Contraction begins spontaneously in an area called the…

A

sino-atrial (SA) node, in the right atrial wall near the entry of the superior vena cava.

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9
Q

The heart-beat originates spontaneously at the _________ because of the _________ of cardiac muscle (-the SA node generates ‘100 beats per min’ )

A

SA node, myogenic nature

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10
Q

How is the heart beat made to slow down or speed up?

A

By the autonomic nervous system (ANS).

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11
Q

Sympathetic fibres…

A

normally discharge at a slow rate but can increase heart rate by up to 100%.

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12
Q

Parasympathetic fibres can…

A

reduce the heart rate by 30%.

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13
Q

The atria are separated from the ventricles by the connective tissue of the _______________ (cannot carry the action potential) so the contraction wave stops.

A

annulus fibrosus

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14
Q

Because of the annulus fibrosus there is…

A

a delay of 0.11 sec between atrial and ventricular contraction.

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15
Q

Impulses travelling to the base of the right atrial wall near the centre of the heart, stimulate another special region which is called the…

A

Atrio-Ventricular (AV) node.

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16
Q

The AV node transmits an impulse to the muscles of the ventricles, via the _____________________ which cause the muscles to _______.

A

His-Purkinje system’ of specialized fibres, contract simultaneously.

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17
Q

The His-Purkinje system consists of the following parts:

A

Bundle of His/atrioventricular bundle (the start of the system)
Right bundle branch
Left bundle branch
Purkinje fibres (the end of the system

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18
Q

What is the contraction of heart chambers know as?

A

Systole

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19
Q

What is the relaxation of heart chambers known as?

A

Diastole

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20
Q

The cardiac cycle starts with the contraction of the _________, the impulse originating in the __________, causing the blood to be pumped into the ventricles.

A

two atria, sino-atrial node

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20
Q

The period from the end of one contraction to the end of the next is called the…

A

cardiac cycle

21
Q

The frequency of the cardiac cycle is described by the…

A

heart rate, which is typically expressed as beats per minute.

22
Q

Blood normally flows continuously into the atria from the…

A

vena cavae and pulmonary vein.

23
Q

70% of atrial blood flows directly into the…

A

ventricles

23
Q

During ventricular diastole the chambers fill to a volume of…

A

120-130 ml blood in each.

23
Q

The remaining volume in each ventricle is called the…

A

end-systolic volume, usually 50 – 60 ml.

24
Q

The remaining 30% is pushed by…

A

atrial systole

24
Q

At the start of ventricular systole the rise in pressure causes the atrioventricular valves to _____, followed 0.02 to 0.03 sec later by the sudden _____ of the semilunar valves.

A

close, opening

24
Q

70 ml of blood is ejected from the ventricle which is called the …

A

stroke volume output

24
Q

Cardiac output is defined as the…

A

volume of blood ejected into the aorta by the left ventricle in a time period of 1 minute, but normally it isalsothe amount of blood pumped into the pulmonary circulation by therightventricle.

25
Q

Note that __________ increases cardiac output (HR x SV) and ___________ decreases it.

A

sympathetic stimulation, parasympathetic stimulation

25
Q

The atria act as ___________ for the ventricles.

A

primer pumps

26
Q

Cardiac output is measured as…

A

stroke volume x heart rate = 70 ml x 72/min = 5040 ml / minute  ~ 5 litres / min.

26
Q

Frank - Starling Law of the heart explains the…

A

the intrinsic ability of the heart to adapt to changing loads of inflowing blood;
“within physiological limits, the heart pumps all the blood that comes to it without allowing excessive damming of blood in the veins”

26
Q

Stroke volume depends mainly on ______________

A

venous return to the atria.

27
Q

The P in an ECG chart is the…

A

atrial depolarization, which triggers atrial contraction.

28
Q

The QRS in an ECG chart is the…

A

depolarization of AV node and conduction of electrical impulses through the ventricles. Ventricular contraction begins at R.

29
Q

The T in an ECG chart is the…

A

repolarization of ventricles.

30
Q

The P to R interval in an ECG chart is the…

A

time required for impulses to travel from SA node to ventricles.

31
Q

What are the two heart sound heard using a stethoscope?

A

Lub and Dub

32
Q

Lub is the first sound due to the…

A

closing of the bicuspid and tricuspid valves between the left and right atria and ventricles respectively, during ventricular systole.

33
Q

Dub is the second sound due to the…

A

closing of semilunar valves in the pulmonary artery and the aorta, at the beginning of ventricular diastole.

34
Q

Arterial blood pressure is measured using a…

A

sphygmomanometer.

35
Q

The blood pressure in a young healthy adult is about…

A

120 mmHg at systole dropping to 80 mmHg at diastole
Written as 120/80

36
Q

Equation for calculating blood pressure is…

A

Mean Arterial Pressure = Diastolic + 1/3rd (Systolic – Diastolic)

37
Q

Mean pressure in the aorta is…

A

100 mmHg

37
Q

Pressure is about _______ at the start of the arterial capillary bed

A

25 mmHg

37
Q

Resistance is greatest in the arterioles at start of the capillaries where pressure drops to…

A

30 mmHg.

38
Q

The venous capillary pressure is _________ and it continues to drop in the venous system being almost exactly _________ in the vena cava at the right atrium.

A

10 mmHg, 0 mmHg

39
Q

The pulse pressure curve of high systolic and low diastolic pressures becomes less as…

A

blood passes through the smaller arteries until it almost disappears in the capillaries (1mm Hg).

40
Q

What is pulse pressure?

A

The difference between the systolic and diastolic pressure readings.

41
Q

The maximal systolic pressure is terminated by a sharp drop or __________ at the ______________.

A

incisura, commencement of ventricular diastole

42
Q

This sharp drop or incisura is explained by a…

A

falling intraventricular pressure causing a backflow of blood from the aorta into the ventricles which causes a drop in aortic pressure but rapidly the aortic semi-lunar valves snap closed which causes a brief rebound in aortic pressure.

CGIER 2-4 (3 decks)

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