cardiac anatomy and physiology Flashcards
what are the 3 key features of cardiac muscle?
- striated
- intercalated discs
- cells communicate via gap junctions
why does cardiac muscle contraction last longer than skeletal muscle contraction?
after initial depolarisation there is a plateau phase (due to the slow Ca2+ channels)
what is the main metabolite used by cardiac muscle during aerobic respiration?
free fatty acids
what is the A band?
thick, myosin filaments
what is the I band?
- thin, actin filaments
- extend from Z line towards centre
- also contains troponin and tropomyosin
what are the Z lines?
- contain T tubules which transport action potentials into myofibrils
- contain L-type calcium
channels which open in response to chemical stimuli - triggers opening of further calcium channels on sarcoplasmic reticulum
what is a sarcomere?
functional unit, between a pair of Z lines
what is the sarcoplasmic reticulum?
- membrane network surrounding contractile proteins
- contains calcium channels
what are the key features of myosin?
- 2 heavy chains, 4 light chains
- dual heads- perpendicular at rest, bend towards centre of sarcomere during contraction
- 2 forms- alpha and beta
what are the key features of actin?
- globular protein
- double stranded macromolecular helix
- thin filament
what are the key features of tropomyosin?
- elongated muscle made of 2 helical peptide chains
- occupies longitudinal grooves between 2 actin strands
- partially covers binding sites- regulates interaction
what are the key features of the troponin complex?
- troponin I- inhibits- binds to tropomyosin and holds in actin binding site
- troponin T- binds troponin complex to tropomyosin
- troponin C- high affinity calcium binding sites, when bound to Ca2+ TnI detaches and actin site is exposed
what does the right atrium receive blood from?
- inferior vena cava
- coronary veins
- superior vena cava
what separates the 2 parts of atrium and what are the 2 parts of the atrium?
- crista terminalis
- sinus venarum and atrium proper
what is found on the wall of the inter atrial septum?
fossa ovalis- remnant of foramen vale
what divides the inflow and outflow portions of the right ventricle?
supraventricular crest
what is contained within the inflow portion of the right ventricle?
trabeculae carnae
what is the outflow portion of the right ventricle known as?
conus arteriosus
what is the outflow portion of the right ventricle derived from?
bulbus cordis
what structures prevent the atrio-ventricular valves from opening during ventricular contraction?
papillary muscles- which attach to the valves via chordae tendonae
what is the outflow portion of the left atrium lined by?
pectinate muscles
what forms the first heart sound?
closing of the mitral and tricuspid valves
what forms the second heart sound?
closing of the aortic and pulmonary valves
where do the coronary arteries originate from?
aortic sinuses of the ascending aorta
what are the branches of the right coronary artery?
- conus artery
- sinus artery
- right marginal branch
- atrioventricular nodal artery
- posterior descending artery
- posterior left ventricular branch
what are the 2 terminal branches of the left coronary artery and what do they supply?
- circumflex- obtuse marginal branches off this- circumflex supplies left atrium, marginal supplies left ventricle
- left anterior descending artery- supplies most of front surface of heart and inter ventricular septum
what are the 3 layers of the pericardium?
1- fibrous outer layer
2- serious parietal layer
3- serous visceral layer
where are vagal fibres mainly distributed to?
artia- as it works to decrease heart rate rather than decrease the strength of contraction
what is the path of the left vagus nerve?
passes between left subclavian and left common carotid, crosses arch of aorta, reaches oesophagus, branches to oesophagus, cardiac plexus and pulmonary plexus
which vein does the right vagus cross?
arch of the azygos vein
which vertebrae do the phrenic nerves arise from?
C3, C4, C5
what are the functions of the pericardium?
- protection of the heart
- provide a friction- free surface for the heart to accommodate its sliding movements- aided by pericardial fluid
what does each letter on the ECG represent?
P- atrial depolarisation
Q- left- right depolarisation
R- depolarisation of main mass of ventricles
S- depolarisation at ventricular base
T- ventricular repolarisation
U- repolarisation of interventricular septum
what is myogenic auto- regulation?
increased stretching in blood vessels can stimulate contraction in arteriolar smooth muscle
what local factors can cause vasoconstriction?
- endothelin 1
- internal BP
what local factors can cause vasodilation?
- hypoxia
- adenosine, bradykinin
- NO
- K+, CO2, H+
what vasodilators are secreted by the endothelium?
- NO
- prostacyclin
what vasoconstrictors are secreted by the endothelium?
endothelin
in neural regulation, what receptors does ACh from the parasympathetic nervous system act upon?
- M2 receptors
- inhibits adenyl cyclase- reducing cyclic AMP
In neural regulation, what receptors does adrenaline from the sympathetic nervous system act upon?
- type 1 beta adrenoreceptors
what are peripheral chemoreceptors stimulated by?
- fall in PaO2 or pH
rise in PaCO2
what do central chemoreceptors respond to?
increase in PaCO2
where are the central and peripheral chemoreceptors found?
- central- medulla
- peripheral- aortic and carotid bodies
what does stimulation of central chemoreceptors cause?
- vasoconstriction
- increased peripheral resistance and blood pressure
what are the 2 types of baroreceptors?
- primary (arterial- carotid sinus and aortic arch)
- secondary (veins- myocardium and pulmonary vessels)
what does stimulation of baroreceptors cause?
- inhibition of SYMP centre in medulla
- inhibition of angiotensin
- ADH release
what is the firing rate from baroreceptors proportional to?
mean arterial pressure (MAP) and pulse pressure (PP)
what are the main hormonal vasoconstrictors?
- epinephrine (acting on alpha receptors)
- angiotensin II
- ADH/ vasopressin
what are the main hormonal vasodilators?
- epinephrine (acting on beta receptors)
- atrial natriuretic peptide (from atria)
what is an inotropic effect?
an effect that changes the force of cardiac contraction
what is a chronotropic effect?
an effect that changes the heart rate
what is starlings law?
within physiological limits, the larger the volume of the heart, the greater the energy of its contraction and the amount of chemical change at each. contraction
how does a pacemaker action potential occur?
- hyperpolarisation (-60mV) activates HCN channels- allow slow Na+ influx- slow diastolic depolarisation
- at -40Mv, activates Ca2+ channels- influx
- +20mV- K+ channels open- efflux
- repolarisation followed by hyperpolarisation
what can alter to transfer of Na+ via a HCN channel?
- catecholamines (e.g. adrenaline) increase transfer
- ACh slows rate of transfer
in Einthovens triangle, where do leads I, II and III run?
- lead I- right arm (-ve) to left arm (+ve)
- lead II- right arm (-ve) to left leg (+ve)
- lead III- left arm (-ve) to left leg (+ve)
what does an ST elevation in leads V1-V6 or avL indicate?
occlusion of the left anterior descending artery
what does an ST elevation in leads II, III or avF indicate?
occlusion of the right coronary artery
what does an ST elevation in leads II, III or V4 indicate?
occlusion of the left circumflex artery
what is haematopoiesis?
formation of blood cells
what are the 3 main processes involved in haematopoiesis?
- erythropoiesis
- myleopoiesis
- thrombopoiesis
what is acute anaemia?
- blood loss due to injury
- RBC and plasma lost in equal amounts, so haematocrit remains at 45%
what is chronic anaemia?
- loss of RBC due to inflammatory disorders or malignancy
- haematocrit drops to around 20%
what is iron-deficiency anaemia?
- caused by malabsorption, poor diet
- haematocrit remains at 45%- reduction in mean corpuscular Hb and a reduction in mean corpuscular volume
what is megaloblastic anaemia?
- macrocytosis (produces very large RBC)
- caused by vitamin B12/ folate deficiency
- reduced haematocrit
what is pernicious anaemia?
- autoimmune
- antibodies produces against gastric parietal cells and intrinsic factor
- results in B12 malabsorption
what is haemolytic anaemia?
- shorter lifespan of RBC (less than 30 days)
- increased RBC turnover and production
- leads to jaundice and anaemia
what growth factor stimulates white blood cell maturation?
granulocyte-macrophage colony stimulating factor (GM-CSF)
what can monocytes differentiate into?
- macrophages (phagocytose foreign material)
- dendritic cells (present antigens to immune system)
what is the function of basophils?
- migrate to tissues, become mast cells
- filled w/ histamine-containing granules
express surface IgE
what is the function of eosinophils?
- inflammation
- allergic response
- protection against parasites
what is acute leukaemia?
- haemopoietic stem cells proliferate without differentiation
- bone marrow precursor cells replaced
- causes anaemia, neutropenia and thrombocytopenia
what is acute myeloblastic anaemia?
proliferation of myeloblasts (neutrophil precursor)
what is acute lymphatic leukaemia?
proliferation of lymphoblasts
what is a high grade lymphoma?
malignant tumour developing from lymphocytes
how are platelets formed?
- myeloid stem cell differentiates into megakaryoblast
- undergoes endomitosis to form a megakaryocyte
- packages proteins into granules- forms platelet precursor extensions
what happens when platelets are activated?
- undergo a shape change- from smooth discord to speculated and pseudopodia
- increases SA
- number of glycoprotein 11b/11a receptors increases
- affinity of receptors for fibrinogen increases
- fibrinogen links receptors- platelet aggregation
what are coagulation proteins?
series of enzymes that circulate in an inactive state- sequentially activated in a cascade sequence
which blood type is recessive?
O
what differentiates one blood type from another?
antigenic and immune properties
what antibodies does O serum contain?
anti A and anti B
what antibodies does AB serum contain?
NONE
what are agglutinogens?
antigens
what antigens does rhesus blood contain?
C, D and E
what is the function of VWF?
required for platelets to bind to damaged blood vessels
what is released the na blood vessel is damaged?
endothelin-1 - to constrict the blood vessel to reduce blood flow to the damaged area to prevent blood loss
what are there vasa vasorum?
blood vessels found within the adventitia layer of the walls of blood vessels
