Cardiovascular Physiology Flashcards
List the layers of the heart superficial to deep
Pericardium = Membrane surrounding heart
- Fibrous pericardium
- serous pericardium
- Parietal Pericardium
- Visceral pericardium
Myocardium = cardiac muscle
Endocardium = internal lining of the heart
Explain the blood flow in the pulmonary and systemic circuit
Pulmonary circuit
- Superior / inferior vena cava - poorly oxygenated blood to R atrium
- Blood flows through tricuspid valve to R ventricle
- blood passes through the pulmonary valve to the pulmonary trunk - pulmonary artery into lungs for gas exchange.
Systemic circuit
- Pulmonary veins carry oxygenated blood into L atrium
- blood gets pushed through the mitral valve to the L ventricle
- oxygenated blood passes through the aortic valve into the ascending aorta to be pumped to the rest of the body
Compare the microscopic features of skeletal muscle to cardiac muscle
Cardiac Muscle - Striated - Branched - 1-2 nuclei - intercalated discs contract via sliding phylament theory - involuntary - aerobic metabolism - Extracellular calcium - Ratio 99% contractile to 1% pacemaker cells
Musculoskeletal muscle
- striated
- multinucleated
- voluntary - ATP
Describe the intrinsic conductive system of the heart
Sinoatrial Node - Primary pacemaker begins depolarization
Atrioventricular Node - Delay depolarizarion in atrium by 0.1sec
Atrioventricular bundle - spread the impulse to the ventricles
Pujenkie fibre - help with contraction of ventricular walls and excite ventricles
What is the intrinsic conducting system of the heart (ICS)?
A network of non-contractile cells that distribute impulse in a sequential manner
works with pacemaker cells to maintain the rhythm of the heart.
What is a pacemaker cell/
Keeps sinus rhythm of the heart
What is the cardiac cycle
All events that occur in the hear in one heartbeat
What is the difference between the electrocardiogram (ECM) and electrocardiograph (ECG)?
ECM - the display of a person heartbeat
ECG - the machine that reads the signals
What are the three typical ECG deflections and their electrical/mechanical events
P wave: Atrial depolarization and contraction
QRS: ventricular depolarization and contraction
T wave: ventricular repolarization and relaxation
What causes S1/ S2 sound
S1: the closing of atrioventricular valves mitral + tricuspid
S2: closing of semilunar valves pulmonary + aortic
What is a cardiovascular centre and what are the three types?
Centres found in the medulla that influence the supply of the heart.
- Cardioaccelatory
- Cardioinhibitory
- Vasomotor
What is the interaction of Cardioaccelatory centre with CNS and ANS
Influences the SNS supply to the heart with neural projections to the horns of T1-T6
What is the interaction of Cardioinhibitory centre with CNS and ANS
Influences the PNS supply with neural projections to the Dorsal motor nucleus of Vagus
What is the interaction of vasomotor y centre with CNS and ANS
Influences sympathetic nerve supply to the anterior smooth muscle
What is the difference between systole and diastole?
Systole - Contract
Diastole - relax
List the stages of the cardiac cycle
Stage 1. Mid to late Diastole
- Ventricular filling
- Atrial contraction
Stage 2. Ventricular sistole
- Ventricular Isometric contraction
- Ventricular ejection
Stage 3. Early ventricular diastole
- Isovolumetric relaxation
Describe how ventricular volume and ventricular pressure fluctuate during cardiac cycle
Systole
Blood returning to the heart will flow into the atria and ventricles as the pressure in them is lower (due to low volume of blood)
When ventricles are ~70% full, atria will contract (atrial systole), increasing pressure in the atria and forcing blood into ventricles
As ventricles contract, ventricular pressure exceeds atrial pressure and AV valves close to prevent back flow (first heart sound)
With both sets of heart valves closed, pressure rapidly builds in the contracting ventricles (isovolumetric contraction)
When ventricular pressure exceeds blood pressure in the aorta, the aortic valve opens and blood is released into the aorta
Diastole
As blood exits the ventricle and travels down the aorta, ventricular pressure falls
When ventricular pressure drops below aortic pressure, the aortic valve closes to prevent back flow (second heart sound)
When the ventricular pressure drops below the atrial pressure, the AV valve opens and blood can flow from atria to ventricle
Throughout the cycle, aortic pressure remains quite high as muscle and elastic fibres in the artery wall maintain blood pressure
What is cardiac output
The amount of blood pumped out by each ventricle in a minute
CO = HR X SV
What is heart rate? and what is a normal adult heart rate?
Number of heartbeats per minute
Adult 60-100
What is Bradycardia?
Slow heart rate < 60
Effective system - mostly fitness
What is Tachycardia?
Rapid resting heart rate > 100
What is stroke volume? How is it calculated?
the volume of blood pumped per beat per minute.
SV = ESV - EDV
What are the three determinants of stroke volume?
Preload: Degree at which muscle cells are stretched
- venous return
- Exercise
Contractability: Independent of pre and afterload
- SNS stimuli - Myocardium and beta 1
- Hormone ion - Ca2
Afterload: Pressure ventricles must overcome
- The decrease in vessel size = increase resistance
What are the determinants of heart rate?
- Sympathetic innervation
- Parasympathetic innervation
- stress
- caffeine
- smoking
- Age
- Gender
- Body temperature
- Hormones
- Ions
What are the terms EDV and ESV?
EDV - The filled volume of the ventricle before contraction 120mlg
ESV - Residual volume left in the ventricle after contraction 50ml
What are the elastic arteries?
Conductive arteries - Aorta and Trunks
Walls contain elastin which allows them to recoil and receive the pressure from the heart
What are muscular arteries?
Distributing arteries
Have the thickest tunica media and supply blood to organs
What are arterioles?
Resistance vessel
Smallest arteries
constrict with hormonal chemical and neural stimuli
determine blood flow to capillaries
What are capillaries?
Smallest vessel
Have thin tunica intima - capillary beds
Exchange material between blood and Interstitial fluid
WHat are venules?
Smallest vein
capillaries unite to form venules
what are veins?
Take blood back to the heart
have 3 tunics same as arteries
walls thinner and lumen larger than arteries
Accommodate 65% of blood
Differentiate Systolic BP from Diastolic BP?
Systolic = pressure by blood on vessel wall
Diastolic = Arterial blood as a result of diastole
What is Pulse pressure?
Difference between systolic and diastolic.
Measures the elasticity
What is the mean arterial pressure and how is it calculated?
Average pressure during one cardiac cycle
MAP = DBP + (Pulse pressure (PP)/3)
What is the formula for BP?
BP = CO X TPR
TPR = Increase vessel length, vessel diameter and blood viscosity
HR = Caffeine, Stress, Calcium, SNS
SV = Preload (venous return, exercise), contractability (Adrenaline), afterload (HBP)
What is total peripheral resistance TPR?
How big or small is the diameter of a blood vessel.
Small diameter = greater resistance
Factors that affect TPR?
Resistance
- Diameter of vessel small diameter greater resistance
- Viscocity: thickness of blood more thickness more resistance (water, altitude, anemia)
- Lenght: Longer the vessel the more resistance
Describe the Baroreceptor Reflex loop
- Stimuli = decrease BP
- Receptors = baroreceptor in aortic arch (CNX) and carotid sinus (CN IX) pick stimuli
- Afferent Pathway = Vagus and Gasophalangeal pick up stimuli
- Integrating centre = Medulla - Solitary Nucleus - Control centre
1) Cardioaccelerating CAC- Stimulate
2) Cardioinhibitry CIC - inhibit
3) Vasomotor VMC - Stimulate - Efferent Pathway = Effectors SA node + smooth muscle
- CAC uses SNS pathway Beta 1 stimulate SA node to increase HR and myocardium to increase contractability
- VMC uses SNS uses Apha 1 in tunica media to stimulate a neurogenic receptor in blood vessels and create vasoconstriction
- Response = CAC increase HR and contractability
VMC increase vasodilation
What is the mechanism responsible for short-term BP regulation?
neural reflexes associated with cardiovascular control centres which receive information taken from the baroreceptor reflexes that identify changes in BP.
Explain the role that the Renin-Angiotensin-aldosterone system plays in the long-term regulation of blood pressure
1) Decrease in BP
2) Inc. Renin in Kidney
3) Release Angiotensinogen (Liver)
4) Renin + Angiotensinogen = Angiotensin 1 (Liver)
5) Angiotensin-converting-enzyme (ACE) ( lungs and kidney)
6) ACE + Angiotensin I = Angiotensin II
7) Angiotensin II acts on the body to Increase BP
What are the 4 actions of Angiotensin II?
1) Adrenal Cortex - Release Aldosterone- Inc. sodium reabsorption - Inc. water reabsorption - increase MAP - increase BP (CO)
2) increase antidiuretic hormone ADH - Inc. water reabsorption - Increase Map increase BP (CO)
3) Inc. Thirst - Increase water intake - Inc. MAP - Inc. BP (Viscosity, CO)
4) Inc. Vasoconstriction - Inc. MAP - Inc. BP (TPR)
What are the routes which nutrients can be exchanged on the capillary wall?
- Diffusion across cell membrane (Gas)
- Diffusion across the intercellular cleft (amino acid)
- Actively transported protein
Schematic of a capillary bed
- terminal arteriole
- precapillary sphincter
- True capillary
- Thorofare channel
- Postcapillary venule
What is capillary filtration vs. capillary reabsorption
Capillary Filtration: The movement of fluid from the capillary into interstitial fluid via hydrostatic pressure
Capillary reabsorption: The movement of fluids back into the capillaries through osmotic pressure
how does the lymphatic system act in the interstitial space of a capillary?
The lymphatic vessel filtrates the interstitial fluid back into the lymphatic capillaries to return fluids back to the body.
What is NFP?
The net filtration pressure: the interaction between hydrostatic and osmotic pressure driving fluid through the capillary.
What is Oedema and what are four causes?
Swelling or pooling of interstitial fluid in capillaries caused by:
1) Increased capillary hydrostatic pressure
2) Increased interstitial fluid osmotic pressure
3) decreased capillary osmotic pressure
4) Other: poor lymph drainage
