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Intro to Clinical Biochemistry > Heart physiology > Flashcards

Heart physiology Flashcards

1
Q

Function of CVS

A

Transport mechanims of:

O2, CO2, nutrients, antibodies, hormones, waste products and thermoregulation

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2
Q

Describe the heart and how blood flows through it.

A

The heart is a muscular sack found at the center of the CVS. Blood is received by the superior vena cava (deoxygenated) into the right atrium. The right atrium feeds into the right ventricle which contracts following depolarisation. The deoxygenated blood moves to the lungs for gas exchange and returns to the heart to pump oxygenated blood to oxygen deficient organs.

Oxygenated blood enters via pulmonary vein into the left atrium. The oxygenated blood enters the left atrium which pumps oxygenated blood via the aorta to the rest of the body for gas exchange at organs in action.

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3
Q

Name all the valves and the function.

A

Mitral, aortic, pulmonary and tricuspid. All function to prevent backflow

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4
Q

What is the heart enclosed by and how do they facilitate heart function?

A

Heart is enclosed by pericardium and myocardium.

Pericardium -a fibrous sac that encloses the heart and great vessels. Keeps the heart in stable location in the mediastinum and facilitates its movements

Myocardium - muscle of the heart. Make up the middle and the thickest layer of the heart wall. Lies between single cell endocardium layer and the outer epicardium

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5
Q

What is found inbetween pericardium and musclular wall of the heart?

A

The pericardial cavity filled with fluid to aid the contraction by preventing friction

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6
Q

How does the heart meet its own oxygen demnds?

A

Occurs via the coronary artery found running on the outside of the heart. Often the site for disease.

Coronary arteries branch directly from the aorta

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7
Q

What are the 3 main blood vessesl?

A

Vein, Aorta and capillary

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8
Q

Describe the artery compositions

A

Thick smooth muscle layer and elastic layer, since the arteries are under high pressure – these two components allow the arteries to expand and contract

Elastic layer function to recoil to normal configuration following contraction

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9
Q

Describe the veins compositions

A

Unlike arteries the veins do no recieve blood under high pressure, thus, have a smaller elastic layer.

Carries blood against the gravitational pull - tendency for backflow - counteracted by valves found in veins

Movement of blood is assisted by skeletal muscles.

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10
Q

Describe the capillary beds compostions

A

As blood passes through the artery it branches off into smaller and smaller blood branches called arterioles and then into capillaries
- Capillaries carries blood through an organ or tissue

They then combine back together to venules and then to veins

At the arteriole the fluid is squeezed out of the capillary due to higher blood pressure, whilst fluid enters capillary in venule due to osmotic attraction

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11
Q

What cells exist in the heart to aid contraction?

A

Conducting cells - specialised cells co-ordinate heart beat (cardiac conduction system aka action potential)

Contractile cells - generate pressure to move blood using myocardium

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12
Q

Describe how the electrical impulses induce the contractility of the heart.

A

The action potential begins in the sinoatrial node (SA) found in the right atrium. Here the action potential passes through to the left atrium causing them to contract simoultaneously. The action potential is then passed down through the atrium to the atrioventricular node. The action potential reaches apex of the heart via the bundle of his fibres. At the apex the action potential passes up via the purkinjo fibres causing contraction of the ventricles bottom up. Thus, forcing blood to move out the heart

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13
Q

What is the most accurate tool to investigate the hearts function?

A

ECG (electrocardiogram)

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14
Q

Basics of an ECG

A

Produces 12 views of the heart using electrodes placed 1x right arm, 1x left arm, 1x left leg, 1x right leg, and 6x chest.

Uses the action potential between the different electrodes, known as leads, to produce an accurate oversight of the heart. LEAD two is the most useful

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15
Q

ECG what do the different intervals represent. (look at a pic)

A

First peak (PQ interaval/P wave) is atrial depolarisation

Second (and largest) peak (QRS complex) is ventricular depolarisation

Final peak (T wave) - is ventricular repolarisation

Remember the atrial repolarisation is hidden in the QRS

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16
Q

What does lead 2 in an ECG measure?

A

Action potential through the heart, by looking at right arm and left leg

17
Q

Describe what happens during cardiac muscle contraction

AP

A

Begin with the resting potential, the imbalance of electrical charge that exists between the interior of electrically excitable neurons (nerve cells) and their surroundings
- Unstimulated cell are slightly negative

When the action potential reaches the cardiac muscle:
Depolarisation (contraction) - occurs as there is an influx of postively charged ions Ca2+ and Na+. This occurs because channels begin to open making the cell more permeable to the ions.
- Ca2+ is released by ECF and sacroplasmic reticulum
- This all occurs simoultaneously as the potassium channels close, forcing them to be contained intracellularly

18
Q

Describe how contraction is achieved.

A

Involves sacromeres which are made up of a thin (actin) and thick filament (myosin).
Ca2+ binds troponin T to expose binding sites on the actin. ATP is hydrolysed and the myosin will be in a cocked state (cross-bridge broken and ready to fire). New cross-bridge is formed when myosin binds to new places in the actin.
As Pi is released myosin head conformation changes to cause power stroke causing filaments to slide over each other

19
Q

What is end diastolic volume (EDV)? What is it determined by?

A

How much blood is reaching the heart. Determined by:

  • Filing rate - heart rate
  • Venous return - amount of blood returned to heart. Also affects HR - atrial reflex
20
Q

What is end systolic volume (ESV)? What is it determined by?

A

Volume of blood in each ventricle following a complete contraction. Determined by:

  • Preload - amount of blood present
  • Contractility - strength of cardiac contraction
  • Afterload - the pressure which the heart must work, the force that impede the flow of blood out the heart. Primarily composed of the pressure in the peripheral vasculature, the compliance of the aorta, and the mass + viscosity of the blood.
21
Q

What is stroke volume?

A

Amount of blood that leaves the ventricles per cycle.

=EDV-ESV

22
Q

Regulation of cardiac output, with examples.

A

Autonomic nervous system - from cardiovascular centre in medulla oblagata. Feeds both para and sympathetic nervous system.

  • Sympathetic: increases BP. Norephrine
    • increase HR, ventricles contractility, vasoconstriction

Parasympathetic NS - decrease BP acetylcholine
- Decreases HR and vasodilation occurs

23
Q

How is cardiac output calculated?

A

CO (mL/min) = stroke volume x Heart rate

24
Q

What receptors in the brain network act to regulate heart rate and stroke volume (aka cardiac output)?

A

Baroreceptors - monitor BP. Detect arterial BP via stretch receptors

Chemoreceptors - monitor blood chemistry. Detect O2 and CO2 levels

Proprioreceptors - monitor movement. Detect changes in position (spinal cord)

25
Q

Hormones regulating cardiac output and BP.

A

Hormones:
- Increased BP: RAAS (angiotensin II) , ADH (pre-load), epinephrine/norephrine (afterload)(increase HR and vasoconstriction), Thyroxine (increase HR)

Decrease BP:

  • ANP (vasodilation). Inhibits RAAS
  • Nitric oxide -vasodilation
26
Q

Other factors regulating cardiac output and BP.

A

Potassium - affects SA node and HR

  • Hyperkalamia: weak irregular contractions
  • Hypokalaemia: decrease HR

Calcium - affects contractility SV

  • Hypocalcaemia. Weak contractions, arrhythmias
  • hypercalcaemia. strong and lengthy contractions, arrythmias

Gender - female higher HR
Body temp- high temp = higher HR

27
Q

How does potassium affect the heart?

A. The AV node and BP
B. BP and HR
C. The SA node and HR
D. Decreases contractility

A

C

28
Q

How does hypokalaemia affect the heart?

A. Decreases HR
B. Decrease the contractility of the ventricles
C. Effect is too minor to observe effect
D. Weak irregular contractions

A

A

29
Q

How does hyperkalaemia affect the heart?

A. Decreases HR
B. Increase the contractility of the ventricles
C. Effect is too minor to observe effect
D. Weak irregular contractions

A

D

30
Q

How does hypercalcaemia affect the heart?

A. Increases HR
B. Arrhythmia - Weak contractions
C. Arrhythmia - Strong lengthy contractions
D. Increases the afterload

A

C

31
Q

How does hypocalcaemia affect the heart?

A. Increases HR
B. Arrhythmia - Weak contractions
C. Arrhythmia - Strong lengthy contractions
D. Increases the afterload

A

B

32
Q

By what does the sympathetic nervous control cardiac output and what effect does it have?

A. Norephrine - increases BP - increase HR, ventricle contractility, vasoconstriction
B. Acetylcholine - increases BP - increase HR, ventricle contractility, vasoconstriction
C. Acetylcholine - decreases BP - decreases HR and vasodilation occurs
D. Norephrine - decreases BP - decrease HR, vasodilation

A

A

33
Q

By what does the parasympathetic nervous control cardiac output and what effect does it have?

A. Norephrine - increases BP - increase HR, ventricle contractility, vasoconstriction
B. Acetylcholine - increases BP - increase HR, ventricle contractility, vasoconstriction
C. Acetylcholine - decreases BP - decreases HR and vasodilation occurs
D. Norephrine - decreases BP - decrease HR, vasodilation

A

C

34
Q

Pair the following:

A. Baroreceptors
B. Chemoreceptors
C. Proprioceptors

  1. Monitor blood chemistry via detection of O2 and CO2 levels
  2. Monitor movement via detection changes to position
  3. Detect arterial BP via stretch receptors
A

A3
B1
C2

Intro to Clinical Biochemistry (12 decks)

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