The Cardiovascular System Flashcards
Describe the structural arrangement of the walls of the heart and pericardium
- Heart -
3 layers:
-Endocardium (inner layer - epithelium) -Myocardium (middle layer - cardiac muscle)
-Epicardium (outer layer - visceral pericardium. - Pericardium -
‘Sack’ that contains the heart.
Consists of: - Fibrous Pericardium (inelastic sac of fence connective tissue that wraps around heart)
- Serous Pericardium (two layers: paretial and visceral - separated by pericardial cavity which contains serious fluid)
Describe the location of the heart
- Located slightly to he left (2/3) of midline of ribs
- Between 2nd and 5th ribs
- Protected by sternum and ribs
Describe the structural and functional characteristics of the cardiac muscle and the cardiac conducting muscle.
- The Cardiac Muscle -
Forms a branching network of cells which are interconnected by interlaced discs which contain gap junctions. Allow ion transport between cells and promotes coordination contraction. - The Cardiac Conducting Muscle -
Coordinates heart contraction and consists of non-contractile cells that initiate electrical impulses.
Consists of the: sinoatrial (SA) node, atrioventricular (AV) node, AV bundle (of his), right and left bundle branches and purkinge fibres.
Distinguish between pulmonary and systemic circulation
- SYSTEMIC CIRCULATION -
- Delivers blood rich in O2 to most body tissues
- Leaves from left side and returns to right side
- Blood returns low in O2
- Forms an extensive network
- PULMONARY CIRCULATION -
- Delivers blood low in O2 to the lungs
- Leaves from right side, returns to left side
- Blood returns high in O2
- Low pressure system
Discuss how and why the foetal circulation differs from adult circulation
- Foetus receives O2 and nutrients from placenta via the unbiblical cord and needs to bypass the lungs (don’t want foetus to start breathing)
- Ductus Venosus connects the umbilical vein inferior vena cava
- Foramen ovale connects right as left atria
- Ductus arteriosus connects pulmonary artery to arch of aorta
Define the term blood pressure
- The force that the blood exerts on the walls of the blood vessels
What is the different between systolic and diastolic blood pressure?
SYSTOLIC BLOOD PRESSURE (SBP)
- Maximum pressure when ventricles contract
- ~120mmHg
DIASTOLIC BLOOD PRESSURE (DBP)
- Maximum pressure when ventricles relax
- ~80mmHg
Explain pulse pressure and mean arterial pressure (MAP)
PULSE PRESSURE
- SBP minus DBP = ~40mmHg
MEAN ARTERIAL PRESSURE
- DBP and one third of pulse pressure
- 80 + 40/3 = ~93mmHg
What is stroke volume? (SV)
- Volume of blood ejected per best
- ~ 70ml/beat EDV minus ESV
Describe End Diastolic Volume (EDV) and End Systolic Volume (ESV)?
EDV- Amount of blood in the ventricles at the end of diastole - before contraction
~ 130ml
ESC - Amount of blood in the ventricles at the end of systole after contraction
~ 60ml
What is cardiac output (CO)
- The volume of blood expelled by the heart in one minute
- Stroke Volume x Heart Rage
70ml/beat x 75 beats/min - CO = ~5,250ml/min
What is Total Peripheral Resistance (TPR)?
- The pressure in the peripheral vessels, resists flow and changes often according to need.
What is Heart Rate (HR)?
- How fast the heart beats
- ~120bpm newborn, ~64-80bpm in young adults
- Rises with age
What factors affect cardiac output (CO)
- Degree of stretch of myocytes (preload)
- Forcefulness of contraction (contractility)
- Pressure required to eject blood (after load)
What factors affect blood pressure?
- Local control (autoregulation, metabolites and vasoactive chemicals)
- Short-term Mechanisms (neural control, vasomotor centre, cardiac accelerator, cardiac inhibitor centre)
Define hypertension and it’s causes/risks
HYPERTENSION (high blood pressure)
- a sustained systolic blood pressure of >140mmHg or sustained diastolic blood pressure of >90mmHg
RISK FACTORS
- Genetics - Low birth weight - Environmental stress - Diet - Diabetes - Drugs - Kidneys/Cardiovascular Disease
Describe the normal electrocardiograph (ECG) and each of its components
- P WAVE - Depolarisation of the atria
- QRS COMPLEX - depolarisation of the ventricles
- T WAVE - repolarisation of the ventricles
Note: There is usually no wave associated with the repolarisation of the atria
Explain the structure and function of arteries
- carry blood AWAY from the heart
- Thick walls, small lumen
- pulsates - reflects heart activity
- Two types - ELASTIC (aorta, brachicephallic and common carotid) withstand changes in pressure and ensure continuous blood flow and MUSCULAR (most named arteries) distribute blood to muscles/organs
Explain the structure and function of arterioles
- capable of vasoconstriction and vasodilation
- small branches of arteries forming a connection between arteries and capillaries
Explain the structure and function of capillaries
- thin walls - one cell thick!
- enable the exchange of water, oxygen, carbon dioxide and other nutrients and waste chemicals
- connect arterioles to venules
Explain the structure and function of venules
- unite to form a vein - very small blood vessels
- collect blood from capillary bed and deliver it to veins
- 3 layers - extremely porous so that fluid and blood cells can move easily through them into blood stream
Explain the structure and function of veins
- blood RETURNS to the heart through veins
- closer to skin, contain valves to keep right direction of blood flow
- thin walled - low pressure
- holds 54% of blood volume
Explain the events of the baroreceptor response
- TO DECREASE BP -
1) stimulates cardio inhibitory centre to increase parasympathetic nervous system activity in the SA node to lower heart rate.
2) sympathetic nervous system activity is reduced and heart rate is decreased causing vasodilation - TO INCREASE BP -
1) Decreases firing rates to cardiac and Vasomotor centres stimulates cardioaccelerator to SA node which increases heart rate, force of contraction and vasoconstriction.
Contraction of the heart:
Is more forceful in the presence of adrenaline
