Unit 6 Flashcards
what are the 3 muscle layers of the heart?
Pericardium
The Myocardium
The Endocardium
what is the structure of the pericardium
Double layered structure consisting of a fibrous pericardium and a serous pericardium.
what are the two layers of the Serous pericardium
- visceral pericardium and parietal pericardium
- between these is the fluid filled pericardial cavity.
what are the 3 functions of the pericardium?
- to anchor the heart within the mediastinum
- to allow low friction movement between the heart and the thoracic cavity
- to prevent over distension of the heart.
what is the structure of the myocardium?
- Consists of cardiac muscle tissue and a rich supply of blood vessels, lymphatic vessels and nerves.
- Cardiac muscle fibres (cells) are involuntary, striated and branched and the tissue is arranged in interlacing bundles of fibres.
what is the function of the myocardium?
responsible for the pumping action of the heart.
what is the structure of the endocardium?
inner lining of the heart. It consists of endothelial cells and is continuous with the lining of the great vessels attached to the heart. It also covers the valves of the heart and the tendons attached to the valves.
what are the functions of the left and right side of the heart?
- Left side: Pumps Oxygenated blood (systemic circulation), much thicker due to pushing blood around body at higher pressure
- Right side: Pumps Deoxygenated blood (pulmonary circulation)
what are the two chambers of the heart?
Atria = upper collection chambers ventricles = lower distribution/pumping chambers
what is the role of the right atrium?
Right Atrium: receives deoxygenated blood from the Systemic circulation via the Superior and Inferior Venae Cava
what is the role of the right ventricle?
Right Ventricle: pumps the deoxygenated blood to the lungs via the Pulmonary artery
what is the role of the left atrium?
Left Atrium: receives oxygenated blood from the Pulmonary circulation via the Pulmonary vein
what is the role of the left ventricle?
Left Ventricle: Pumps the oxygenated blood to the rest of the body via the Aorta
what is the role of valves?
Valves ensure that blood flows in one direction and can be stopped, open and close in response to pressure changes
what are the two types of valves?
- Cuspid
- semilunar
describe the cuspid valves
- Valves between the atria and ventricles
- Consist of flaps or cusps (made of dense connective tissue)
- Right Atrioventricular valve = Tricuspid valve
- Left Atrioventricular valve = Bicuspid valve/Mitral valve
Describe the semilunar valves
- Valves between the ventricles and blood vessels.
- consist of 3 cusps, each attached along one edge to blood vessel wall, other edges project into lumen of blood vessel
what are the two semilunar valves?
- Pulmonary semilunar valve
- Aortic semilunar valve
Pulmonary semilunar valve
- at exit of pulmonary trunk
- regulates the opening of the right Ventricle into the Pulmonary trunk.
Aortic semilunar valve
- at exit of aorta
- regulates the opening of the Left Ventricle into the Aorta.
what are the 3 additional structures in the ventricles?
- Chordae Tendineae: Braces each flap/cusp of cuspid valves
- Papillary Muscles: connect chordae tendineae on the inner surface of the Ventricles.
- Trabeculae Carnae: deep grooves and folds on the Internal surface of the Ventricles
What is the step by step flow of blood through the heart?
Superior/inferior vena cava > right atrium > right ventricle > tricuspid valve > leaves heart through pulmonic valve > pulmonary artery > lungs > pulmonary vein > left atrium > left ventricle > mitral valve > leaves heart through aortic valve > aorta
what are the 3 types of circulation?
- Right (pulmonary circulation)
- Left (systemic circulation)
- Coronary circulation
describe pulmonary circulation
receives blood that has returned from body tissues and pumps it to lungs
describe systemic circulation
receives blood from lungs and circulates to body tissues
describe Coronary circulation
supplying blood to heart muscle itself through coronary arteries’
What are the steps in the flow of electrical current that creates a heart beat?
Sino Atrial Node (SA Node or Pacemaker) > Atrioventricular Node (AV Node) > Atrioventricular Bundle (AV Bundle or Bundle of His) > Right and Left Bundle Branches > Conduction myofibres (Purkinje Fibres)
what are the 3 readings of an ECG?
- P wave = Depolarisation of atria (spread of electrical impulse over atria)
- QRS complex = spread of depolarisation over ventricles
- T wave = Repolarisation of ventricles
what could enlargement of the P wave in an ECG mean?
enlargement of atrium (mitral stenosis)
• =
what could the lengthening between P and QRS waves in an ECG mean?
inflamed tissue between atria and ventricles (atherosclerotic heart disease and rheumatic fever)
what are the Systole and Diastole phases of the cardiac cycle?
Systole = Contraction = Emptying Diastole = Relaxation = Filling
- Atrial Systole
- Ventricular Diastole
- Ventricular Systole
- Atrial Diastole
what are the two heart sounds called and how are the caused?
Lubb: caused by closing of AV valves
Dupp: caused by closure of semilunar valves
what are the 3 major types of blood vessels?
- Arteries: Carry blood away from the heart towards caps.
- Veins: Carry blood from venules > heart.
- Capillaries: Microscopic vessels that connect arterioles > venules
what are the 3 types of arteries?
- Elastic arteries
- Muscular arteries
- Arterioles
describe structure and function of elastic arteries
- Thick-walled
- largest diameter
- closest to the heart (e.g., aorta, pulmonary trunk).
describe structure and function of muscular arteries
- Medium sized
- present on distal parts of elastic arteries
- mainly distribute blood (e.g., radial, femoral arteries).
describe structure and function of arterioles
- Smallest of the arteries
- carry blood to capillaries.
describe structure and function of veins
- Carry blood towards the heart from the capillaries.
- Generally have thinner walls and larger lumens.
- Divide into venules (Small vessels that drain blood from capillaries > veins.)
- Contain valves in their walls
what are the 3 types of capillaries?
- continuous: most common, least permeable
- fenestrated: large pores and increased permeability
- sinusoid: most permeable, least common
What is the function of capillaries?
- Connect arteries with veins via arterioles and venules respectively.
- Capillaries are the only place where ‘substances’ enter or leave the circulation.
what are the 3 layers of blood vessels (excluding capillaries)
- Tunica intima/interna
- Tunica media
- Tunica adventitia/externa
what is the structure of the tunica intima/interna?
- Endothelium: The inner coat of all blood vessels consists of endothelial cells and are in direct contact with the blood in the lumen.
- Some collagen fibres are present to provide strength (this is the only layer in capillaries).
what is the basement membrane?
- non-cellular
- thin
- proteinaceous layer of extracellular material
- separates the tunica interna from the tunica media.
what is the internal elastic lamina?
In arteries, a layer of elastic tissue called is present, it is not present in veins.
describe the structure of the tunica media
- consists mainly of smooth muscle cells arranged in concentric layers around the tunica interna.
Gap junctions: between the smooth muscle cells allow for transmission of electrical impulses
Elastin: give elasticity to the vessel walls.
Describe the structure of the tunica externa
- mainly longitudinal collagen and elastin fibres.
- In arteries, the external elastic lamina separates the tunica externa from the tunica media
what 4 factors effect BP?
- Cardiac output
- Peripheral resistance
- Blood volume
- Elasticity of blood vessels
how does cardiac output effect BP?
- The volume of blood pumped by one ventricle in one minute
- BP is directly proportional to cardiac output (increase in CO = increase in BP)
- controlled by the Cardiovascular control centre (CVC)
how does peripheral resistance effect BP and what are the two main components?
BP is directly proportional to peripheral resistance. Subject to variation in the short term
Two components:
- Diameter of the blood vessel
- Viscosity of the blood
how does diameter of blood vessel (in relation to peripheral resistance) effect BP?
- Can vary as a result of vasomotor activity (part of CVC is the vasomotor centre which controls diameter of blood vessels)
- The amount of friction created by the blood vessel is inversely proportional to the diameter of the blood vessel. Peripheral resistance = 1 / r 4.
- Arterioles offer the greatest resistance and can also vary the resistance by altering their diameters.
- -sympathetic nervous system maintains constant tone of arterioles = main influence on maintenance of normal BP
how do baroreceptors (in relation to peripheral resistance) effect BP?
- -located in aortic arch and carotid sinus
- -monitor BP of blood flowing through these vessels
- -info from baroreceptors relayed t CVC which responds to maintain homeostasis
- EX: If BP drops, cardiac centre increases HR and SV. Vasomotor centre causes vasoconstriction = increase peripheral resistance
how do peripheral chemoreceptors effect BP?
When O2 is low > peripheral chemoreceptors are stimulated > the VMC is stimulated > PR rises > BP rises
how does viscosity of the blood effect BP?
- Mainly determined by: Red blood cell count and condition of blood plasma only changes due to disease or loss of body fluids
How does polycythaemia effect BP?
RBC count increases > Viscosity of the blood increases > PR increases > hence BP increases
how does anaemia effect BP?
RBC count decreases > Viscosity of the blood decreases > PR decreases > hence BP decreases
how does elasticity of blood vessels effect BP?
- As blood vessels age or are affected by disease, they lose elasticity resulting in increase of pulse pressure (difference between systolic and diastolic pressure)
- The walls are stretched during systole and they recoil during diastole
why do we require high systemic blood pressure?
- To get blood to the tissues, especially the brain.
- The blood needs to have enough pressure behind it to return to the heart; has to overcome gravity.
- To provide the filtering force at the kidney.
what are 5 other factors that can influence BP?
- Higher brain centres: emotions stimulate or inhibit
- Resp centre: stimulates
- Chemoreceptors: stimulate or inhibit
- Sensory endings: stimulate or inhibit
- CO2 and H+: stimulate
what is Starlings law?
The greater the length of stretched cardiac muscle fibres, the stronger the contraction.
What effects and controls the regulation of stroke volume?
- Venous return affected by state of contraction of blood vessels (vessels constricted = restricted blood flow OR vessel dilated = increased blood flow)
- Affected by nerves and hormones
What factors influence the regulation of heart rate?
- Nervous influences
- Hormonal influences
- Chemical influences
- Temperature
- Age
- Gender
How do nervous influences regulate HR?
- Activity of heart influenced by cardiac centre in medulla oblongata
- Impulses to either:
sympathetic: Impulses cause release of noradrenaline at nerve endings = increase heart rate and strength of contraction
parasympathetic: vagus nerve carries parasympathetic fibres which release acetylcholine at nerve endings at sinoatrial and atrioventricular node = depresses heart activity by slowing HR and diminishing contraction strength
how do hormonal influences regulate HR?
Adrenaline and nor adrenaline are released from the adrenal medulla during stress and accelerate HR
how do chemical influences regulate HR?
- Concentration of certain ions has effect on HR
- Na+ in low concentration can increase HR
- K+ in high concentration can cause irregular HR
how does body temp effect HR?
Direct relationship between body temp and HR i.e. increase temp = increase HR
how does age effect HR?
Inverse relationship i.e increase in age = decrease in HR
How does gender effect HR?
Females tend to have faster HR than males
How is the distribution of cardiac output determined?
- Normally 5L of blood pumped from left ventricle/min
- Distribution depends on needs of organs at the time and is determined by state of constriction or dilation of vessels leading to that organ
- Active tissues receive a greater proportion of the cardiac output
what causes vasodilation?
- result of lesser number of impulses running down the nerve fibres from vasomotor centre (VMC) to the smooth muscle in the blood vessel wall.
- Causes relaxation of the smooth muscles in the walls of the blood vessels especially the arterioles.
what causes vasoconstriction?
- result of more number of impulses running down the nerve fibres from vasomotor centre (VMC) to the smooth muscle in the blood vessel wall.
- Causes contraction of the smooth muscles in the arteriole wall.
what happens to different organs in terms of blood flow during exercise?
- The brain generally remains constant
- Cardiac muscle triples
- Skeletal muscle increases tenfold
- Skin increases almost fourfold (as a means of temperature control)
- The kidney halves
- The gut halves
- Other areas decreases
