Cardiovascular System Flashcards
The CVS operates via 2 systems:
- Systemic
- Pulmonary
*united by heat
There is high pressure within the:
Left ventricle
Aorta
Systemic capillaries
Systemic circuit
There is low pressure within the:
Systemic capillaries
Right atrium
Right ventricle
Pulmonary circulation
Left atrium
Left ventricle
Blood pressure is calculated by…
Pressure = Force/Area
Flow is calculated by…
Flow = (Pressure1 - Pressure2) / Resistance
Primary functions of the cardiovascular system?
Delivery of O2 to tissues and cells
Removal of by-products and CO2
Enables metabolism, growth and repair by delivering necessary components to specific parts of the body
Intercalated discs
Interlocking of adjacent cardiomyocytes
Desmosomes:
Provide strength and anchor membranes together
Gap Junctions:
Allow for signalling with movement of ions between cells
Functional syncytium:
A single unit of electrically-coupled cardiomyoctes
*There are no gap junctions between atrial and ventricular cells.
Atrial and ventricular cells are separated by….
Non-conductive fibrous tissue that surrounds the AV valves
Purkinje fibres:
Modified muscle cells which contract depolarisation more rapidly than muscle cells
Found within ventricular walls and Bundle of Histamine
The AV node generates primary action potentials for heart contractility. T/F
False, SA node
The rate of AP production is limited by ____
how fast Na+ leaks through HCN c
HCN channels:
Hyperpolarization-activated cyclic nucleotide–gated channels
The AV node generates…
~40-60 AP/min
~40-60 AP/min
When conduction to the ventricles causes spontaneously contraction out of sync with the atria.
Ventricular myocytes have no capacity for generating action potentials and their resting membrane potential rests at a stable level until an action potential from arrives from the bundle of His. T/F
True
Ventricular myocytes have no capacity for generating action potentials and their resting membrane potential rests at a stable level until an action potential from arrives from the bundle of His.
This initiates the…
Ventricular action potential –> increase in Ca2+ entry –> contraction of the myocyte.
- Fast Na+channels open, rapidly depolarising the cell.
- This opens L-type Ca2+>channels, as in SA node cells. This Ca2+entry initiates contraction.
- Voltage-gated K+channels open as the Na+and Ca2+begin to close, causing hyperpolarisation and bringing the membrane potential back to its resting level
The ECG measures…
the electrical activity that reaches the skin surface, initiated by a cardiac impulse
Atrial repolarisation is shown on the ECG. T/F
False
Contraction:
Systole
Relaxation:
Diastole
Lead ll describes the positioning of…
1 lead on the right arm
1 lead on the left leg
P wave:
Atrial depolarisation –> contraction –> systole
- Small wave, because the atria has small muscle mass
Always positive in lead ll during sinus
QRS complex:
Depolarisation of the ventricles. –> contraction –> systole
- The electrical wave generated by the left ventricle is larger than the right
A short QRS complex shoes rapid depolarisation of ventricle (desirable)
Isovolumic contraction:
Closing of AV valves within a build-up of pressure ((Q)RS complex)
The AV node functions to…
Delay impulse speed
At what point in the ECG does arterial pressure increase?
R corresponds to innervation of the purkinje fibres.
–> depolarisation of the ventricles, –> contraction and thus increase arterial blood volume/pressure.
At what point in the ECG does arterial pressure increase?
T corresponds to repolarisation of the ventricle, –> decrease in arterial blood volume, –> increase in arterial volume.
Describe the movement of the electrical signal from the pacemaker to the purkinje fibres.
The electrical wave moves from the SA node to the internodal tracts –> small increase (P) on the ECG.
Arriving at the AV node there is a small delay on the ECG (PR interval).
The wave then travels to the bundle of HIS causing a small decrease on the ECG (Q).
After this the wave travels through the purkinje fibres, –> increase in ECG voltage (R), followed by a decrease as the purkinji fibes depolarise the top of the ventricle (S).
Blood pressure is highest during…
Systole
Hypertension is characterized by a bpm of…
140/90mmHg
Atherosclerosis:
If the blood vessel has a tear, –> WBC will coagulate around the tear; fat, cholesterol, and other substance can attach to the tear and cause a plague that stiffens the arterial wall.
If the tear ruptures, a blood clot can form and block the flow of oxygen –> heart attack or stroke
Angioplasty:
Widening of clogged blood vessels
Resistance is dependant on:
blood viscosity;
number or erythrocytes,
vessel length
diameter
Poiseulles Law:
The flow of Newtonian fluids for no turbulence
Central venous pressure:
Difference in arterial pressure and venous pressure
Total peripheral resistance:
Resistance across the whole systemic circuit
Cardiac suction occurs when the _____
atrial cavity enlarges during ventricular contraction (atrialpressure < 0mmHg)
Altering MAP:
Increasing cardiac output –> incr. Volume of blood in aorta
Increasing total peripheral resistance –> vasocontraction
If stroke volume, mean arterial pressure, and heart rate are known, it is possible to determine which of the following?
- Total peripheral resistance
- Cardiac output
Conducting arteries:
Arteries close to the heart; largest diameter
Disturbing arteries:
More muscular arteries (less elastin in tunica intima and more smooth muscle inthe tunica media)
Arteries offer low resistance. T/F
True, due to the large radii
Arterioles have a larger tunica ___
Media
Elastic arteries contain
Fibers for elasticity
Intrinsic Control of Vascular Tone:
Alters the radii of arterioles within a tissue through chemical or physical influences:
Nitric oxide and histamines initiate:
Vasodilation
Endothelin initiates:
Vasoconstriction
Myogenic receptors respond to:
Stretch
Extrinsic control of vascular tone is via the
the endocrine or nervous system
The sympathetic nervous system (SNS) releases noradrenaline which acts on:
α-1adrenoreceptors to induce vasoconstriction
The SNS releases adrenaline(from the adrenal medulla) which acts on:
β-2adrenoreceptors to induce vasodilation –> heart and skeletal muscle perfusion.
There is no direct parasympathetic nervous system innervation of blood vessels;
Acetylcholine (ACh) is released onto the vascular endothelium –> nitric oxide is release–> local vasodilation)
Extrinsic control: Angiotensin & Vasopressin initiate
Vasoconstriction
Extrinsic control: Atrial Natriuretic Peptide & Bradykinin initiate
Vasodilation
Question: Why doesn’t arterial pressure drop to 0 mmHg in arteries during diastole?
It is due to the elastic properties of the arterial walls –> driving force for blood flow during diastole.
The elastic recoil of the vascular wall functions to:
maintain the pressure gradient that drives the blood through the arterial system.
What would occur if artery walls were rigid and unable to expand and recoil?
Their resistance to blood flow would greatly increase –> blood pressure would rise to even higher levels, –> require the heart to pump harder to increase the volume of blood expelled by each pump (the stroke volume) and maintain adequate pressure and flow.
Why do muscular arteries need to be muscular? What can affect the radii of muscular arteries?
To allow for active constriction and relaxation based on the needs of the body.
For example, the autonomic nervous system can release noradrenaline, to induce vasoconstriction. This decreases the radii of muscular arteries, –> during the fight or flight response.
An adult has been diagnosed with endothelial dysfunction.
What are the likely future complications, if the condition is not managed correctly?
Endothelial dysfunction can lead to atherosclerosis. First blood pressure may become more difficult to manage as blood vessels are no longer elastic enough to adapt to increased pressures. Artery wall can thick as the vessel attempts to heal itself, forming plague from blood clots. This could eventually lead to heart attacks and strokes.
Capillaries consist of a…
Venous and arterial end
Net hydrostatic pressure at the arterial end
33mmHg out
Net hydrostatic pressure at the venous end:
13mmHg out
Net oncotic pressure at the arterial end:
20mmHg in
Net oncotic pressure at the venous end:
20mmHg in
Net filtration pressure at arterial end:
+13mmHg out
Net filtration pressure at venous end:
-7mmHg in
Precapillary spincters:
Control blood flow through capillary spincters
Squeeze down to inhibit blood flow –> blood flows through to the thoroughfare channel
There are two opposing important forces driving fluid movement across the endothelial cells:
hydrostatic pressure and oncotic pressure
Oncotic pressure:
a form of osmotic pressure induced by proteins, notably albumin, in a blood vessel’s plasma
Met-arteriole:
Smooth muscle within the wall
True capillaries extend all throughout the individual cells. T/F
True
Which of the following components exerts the highest net hydrostatic pressure to promote movement into the capillaries?
Proteins
What substances are reabsorbed in the venous end of capillaries?
Carbon dioxide and waste
i) How do nutrients such as oxygen move out of the capillaries into tissue?
ii) How do the arterial and venous sections of the capillaries function in capillary exchange?
As blood is pumped into the arteries it exerts a greater force out of the capillaries than force going in (Arterial section).
–> This allows fluid to exit the capillaries through spaces between cells.
Small molecules of nutrients such as oxygen are able to leave the capillary.
During the venous section, the force from being pumped into the capillary has decreased.
Here the concentration proteins i.e. albumin, and low concentration of gasses and small molecules attracts fluid back into the capillary i.e. C02 and waste
Compare and contrast the function of smooth muscle in muscular arteries, and pre-capillary sphincters.
Their function is similar. Capillaries do not have smooth muscle covering it (as it needs to be thin for nutrient exchange), it instead has pre-capillary muscular sphincters to regulate amount of blood flow depending on the body’s needs.
Capillary walls are 2 cells thick. T/F
False, 1 cell thick
Hormones are circulated via the….
Lymphatic system
Lymphatic cells are made of…
Endothelium, anchored by collagen filaments
The valves open when…
When pressure in the interstitial space is greater than within the capillary
Trunks of the lymph system:
- Lumbar (2)
- Broncho-mediastinum (2)
- Subclavian (2)
- Jugular (2)
- Intestinal
Thoracic duct includes _____ and drains into the ____
All excl. Right side of head and arm
–> left jugular and left subclavian vein
Right lymphatic duct includes ____ and drains ____
Right side of head and arm
–> jugular & subclavian vein
Lymphoid organs diffuse lymph tissue, within the GI, respiratory patch, and intestinal wall via the _____
Peyers patches
When an infection gets in a tissue:
- lymphatic capillary
- lymph node
- Detected by a dendritic cell
- Sample lymph and present antigens to B-cell to make anti-bodies
- plasma cell
- exit lymph node
Antibodies are generated in the…
White pulp of the spleen
The red pulp is responsible for…
Recycling old RBCs
Lymph ducts terminate in small, blind-ended capillaries. T/F
True
Reduced plasma proteins reduces…
Oncotic pressure in plasma
i.e. renal disease or cirrohis
Increased venous pressure initiates…
Greater hydrostatic pressure in plasma
i.e. heart failure
Increased permeability of capillary walls causes:
plasma proteinsto move into interstitial fluid
–> increasingoncotic pressure in interstitial space
–>fluid retention
i.e. local inflammation
Increased blood in veins causes a(n)
Increased hydrostatic pressure in plasma
–> filtration
Blockage of lymph vessels causes
A reduction in lymphatic drainage –> accumulation of interstitial fluid in tissues
i.e. surgical removal of lymph nodes in cancer
Pleural effusion:
Oedema accumulation in the lungs
Pericardial effusion:
Oedema accumulation in the heart
Peritoneum effusion/Ascites:
Oedema accumulation in the abdomen
Peripheral oedema:
Oedema accumulation in the lower-limb
Transudate:
Low in protein and cellular content
- Incr. Hydrostatic pressure
- Decr. Osmotic pressure
Excaudate:
High in protein and cellular content
- Inflammatory response
- Lymphatic obstruction
SPECgrav:
measuring of density of fluid; transudate or exudate?
An excess of instititual fluid causes….
- Incr. distance between blood and cells
- Decr. rate of diffusion
- Inadequate nutrient supply
Direct contributors to movement of fluid through the lymphatic system
- Smooth muscle
- Skeletal muscle
- Arterial pulse
Veins have low resistance to blood flow, however they are more compliment than arteries. T/F
True
The venous system is a reservoir for blood. T/F
True
Venous return:
The volume of blood entering the atrium each minute; stabilised and regulated by veins.
End diastolic volume:
Amount of blood in ventricles prior to contaction
End diastolic volume
Stroke volume
Cardiac output
are all dependant on…
Venous return
Venous pressure is highest in ___
and lowest in ___
Venules
Vena-cava and right ventricle
Venous return is affected by:
Skeletal muscles
Sympathetic nerve activity
Respiratory activity
Inspiration initiates…
- Pulls diaphragm down
- Decr. intrapleural pressure
- Lungs expand
- Incr. systemic venous return
Inspiration decreases ___
and increases ___
Decr. BP
Incr. HR
The paradoxical fall in pressure is explained by…
When the vagual tone is reduced, the HR increases
Expiration initiates…
- Relaxation of diaphragm
- Incr. in intrapeural pressure
- Deflating of lungs
- Decr. in venous return
- Compression of pulmonary vessels
Expiration decreases ___ and increases ___
Increases BP, decreases HR
Exhalation ___ venous return
Decreases
Which is one explanation for an increase in heart rate, when moving from a lying to a standing position?
Venous return
How does inhaling increase venous return?
During inhalation, the diaphragm moves down, –> decreasing thoracic pressure.
–> decreased right atrial pressure, facilitating venous return.
The downwards movement of the diaphragm also increases pressure on the abdomen, squeezes blood up towards the heart.
How does exhaling decrease venous return?
During exhalation, the diaphragm moves up,
-> increasing thoracic pressure.
-> This in turn results in increased right atrial pressure, decreasing venous return.
The heart rate depends primarily on the balance between sympathetic and parasympatheric nerve impulses. T/F
True
The vagal tone has a dominant effect at rest:
The SA node exhibits spontaneous pacemaker activity with an intrinsic rhythm of about 100-110 bpm. But normal HR is only about 60-70 bpm, which indicates that vagal (parasympathetic) tone has a dominant influence at rest.
To achieve a high HR, vagal tone must be
decreased
Parasympathetic preganglionic fibres originate from the dorsal motor nucleus of the vagus nerve and synapse on…
parasympathetic ganglia within the heart –> release acetylcholine on muscarinic receptors on the SA Node, atrial muscle and AV node.
It has been found that a natural compound decreases heart rate when inhaled.
Which of the following may be potential reasons why the natural compound decreases the heart rate?
Decr. Sympathetic output
Incr. Parasympathetic output
A patient undergoing septic shock, characterised by severe vasodilation, and subsequent inability for nutrients such as oxygen to reach areas of the body where it is needed.
Which hormones should be administered to help the patient?
Noradrenaline should be used to increase vasoconstriction and increase heart rate to help compensate for the vasodilation.
A patient with a blockage in the pulmonary artery, due to complications regarding deep vein thrombosis, exhibits symptoms of tachycardia and hyperventilation.
Explain why the patient is suffering these symptoms.
Blockage of the pulmonary artery causes the inability for oxygen to be taken from the lungs and distributed to the organs. This hypoxemia (low oxygen in blood) is one reason heart rate is increased.
Stroke volume is calculated by:
End Diastolic Volume - End Systolic Volume
Pre-load:
- Myocardial sarcomere length prior to contraction
- Ventricular filling
- Ventricular and pericardial compliance
- Wall thickness;
*Hypertrophy decreases pre-load
After-load
- Force that ventricles must contract to eject blood.
- Sum of all elastic and kinetic forces
- Resistance or impendence
Contractility is inhibited by:
Ca2+ and beta-blockers, high concentrations of K+ and Na+
Contractility (inotropy)
All other factors that are responsible for changes in myocardial performance
Positive chronotrophic agents:
Incr. production of sympathetic neurotransmitters
Noradrenaline
Adrenaline
Noradrenaline and adrenaline synapse on
β1 anderoceptors, incr. HR
An increase of Ca2+ will likely…
Increase heart contractility
Negitive chronotrophic agents:
Increase production of parasympathetic neurotransmitters
Decr. HR
PSNS incr. production of acetylcholine, to act on muscurinic2 receptors, to…
Decr. HR
A lack of Ca2+ and K+ will ____ heart contractility
Decrease
Bradycardia is characterized by a HR of:
<60bpm
Tachycardia is characterized by a HR of
> 100bpm
Frank Starling law:
The strength of cardiac contraction is dependant on initial fibre length
Frank Starling dictates that,
↑ tension is a result of ↑ length
and;
↑ contractilityis proportional to ↑ end-diastolic volume (EDV).
↑ tension is a result of ↑ length
and;
↑ contractilityis proportional to ↑ end-diastolic volume (EDV).
- An increase in venous return increases stroke volume and cardiac output
- The length tension relationship of muscle fibres and contractility
i) The longer the sarcomere the greater the contraction, why is this?
ii) It is possible for sarcomeres to be too long, resulting in decreased contraction, why is this?
The rationale for long sarcomeres and increased contractility is due to increased surface area –> greater calcium sensitivity.
However, sarcomeres that are too long there is less overlap of the thin and thick filaments.
Short term Mean Arterial Pressure is determined by
Cardiac Output
Long term Mean Arterial Pressure is determined by:
Arterial blood volume and arterial compliance
Low blood flow –>
organ failure, shock and death
High blood flow –>
extra load causes tissue damage –> cardiac, vascular and renal failure –> shock and death
The cardiovascular control center is located within the:
Medulla oblongata
The cardiovascular control center receives…
afferent impulses from baroreceptors; and efferent outputs via the ANS
Cardioaccelerator centres:
- Stimulate cardiac cells by regulating heart rate and stoke volume.
- SNS activation
Cardioinhibitory centres
- Decreases cardiac output and HR
- PNS; vagus nerve
Vasomotor centres
- Control vascular tone of smooth muscles within tunica media (arteries, arterioles, veins)
- SNS; noradrenaline –> vasoconstriction
Afferent Input is via the:
Cortex, limbic system, hypothalamus, and sensory receptors; baroreceptor, chemoreception, and proprioception
Blood pressure is monitored by:
High pressure baroreceptors
Baroreceptors regulate short-term control of blood pressure via;
High pressure arterial baroreceptors
and;
Low pressure volume receptors
High pressure arterial baroreceptors are located within the
Carotid sinus and aortic arch
Low pressure volume receptors are located within the…
Atria
ventricles
pulmonary vasculature
Distension depends on…
Venous return
The afferent neural pathway from stretch receptors are via the ____ nerve –> Nucleus Tractus Solitarius (NTS)
Vagus
MAP is controlled via a
Negitive feedback loop
Primary function of the baroreceptor reflex is to:
Minimize variations in systemic arterial blood pressure;
whether these variations are caused by postural changes of the animal, excitement, diurnal rhythm, or even spontaneous fluctuations of unknown origin.
Arterial baroreceptor afferents innervate:
carotid sinuses, aortic arch and the right carotid artery
-right subclavian artery juncture.
Cardiopulmonary baroreceptors innervate
Veno-atrial juncture, Atria,
Ventricles and Pulmonary vasculature.
The baroreflexes modulate:
paraSNA and SNA to numerous organ systems and vasopressin (AVP) release.
The primary function of the baroreceptor reflex is control of short term, minimisation of blood pressure changes. T/F
True
Baroreceptor reflex dysfunction or failure is a rare disorder.
What would be some of the symptoms/consequences of baroreceptor reflex dysfunction disorder?
- Increases blood pressure variability both in the short term, as well as chronically.
- Innocuous changes such as excitement, diurnal rhythm and postural changes can induce large fluctuations in blood pressure.
Chronically it can also increase incidence of hypertension.
Bainbridge Reflex:
Ensures cardiac output is proportional to effective circulating volume.
–> It is a counter-balance reflex to the baroreceptor reflex in the control of heart rate.
Low pressure baroreceptors trigger tachycardia…
Located within the atria and pulmonary artery
- Distension depends on venous return
- Renin-Angiotensin System
Regulate cardiac output
Chemoreceptor Reflex:
Regulate ventilation and cardiac output
Located in the medulla oblongata and, sense low brain pH, which –> high arterial carbon dioxide pressure.
CNS: Ischaemic Response
- When blood-flow to the brain is compromised; emergency pressure control –> preserves blood-flow to the brain
- Does not become active until systolic blood pressure < 60 mmHg and is
- Most effective around a systolic pressure of 15 to 20 mmHg.
An increase of HR may be due to:
- Activation of the Bainbridge reflex
- Stimulation of atrial baroreceptors
- Stretching of atrium
A patient arrives at the emergency after a car crash, where he received a serious blow to the head.
What are the three symptoms to watch for in the patient, and how are the symptoms related to one another?
After a head injury it is possible the brain will swell up
–> increases inter-cranial pressure and triggers the Cushing reflex.
If this increases above that of mean arterial blood pressure, then this could lead to a lack of blood flow to the brain as blood vessels in the brain become compressed by the pressure.
To compensate for this the body increases sympathetic activity in order to increase arterial pressure, resulting in the first symptom- hypertension. However, this hypertension (high blood pressure) triggers baroreceptors which up-regulate the parasympathetic nervous system, –> decreasing heart rate (bradycardia). This hypertension along with inter-cranial pressure presses on the respiratory centre in the cerebellum, causing irregular breathing.
Blood pressure =
(Stroke Volume * Heart Rate) * Peripheral Resistance
There is no known cause of Primary Hypertension. T/F
True
Primary hypertension is characterized by:
High blood volume,
high resistance
incr. In pressure
Explain the physiology of hypertension
When a person has hypertension their baroreceptors begin to maintain the blood pressure at a higher range. This is caused to the baroreceptors being reset to maintain this higher range.
- Acute resetting of baroreceptor pressure-activity relationship to higher mean pressures in hypertension
A man dies from a stroke. During autopsy it was found that the walls of his left ventricle has enlarged and thickened.
i) How could hypertension have contributed to the enlargement and thickening of the left ventricle?
ii) How could hypertension have contributed to the patient’s stroke?
Left ventricular hypertrophy can occur due to chronic hypertension, as the body attempts to increase the strength of the heart to provide organs with nutrients.
If this man had chronic hypertension, then it is possible that this could also be the cause of the stroke. With increased blood pressure, shear stress increases and can cause damage to blood vessels. This damage, over time could form plaques, and restrict bloodflow. A plaque could have developed in the man’s brain, causing stroke.
The best place to measure venous return is at the:
Right atrium
Venous return fluctuates with…
Respiration
Cardiac output is not influenced by reflexes. T/F
False. Reflexes alter CO
There is less resistance and pressure within the
Pulmonary circuit, because its shorter
Vasoconstriction enhances
Vasoconstriction
Factors affecting venous return:
- Valves
- Contraction of skeletal muscle
- Respiration
- Post-ganglionic noradrenaline
- Cardiac suction
Frank starling refers to the
Intrinsic input-output mechanism
The ischemic response:
Maintains blood flow to the brain and heart ONLY
Incr. in HR
Decr. in BP
- Vasodilation of arteries
- Decr. in MAP
- Hypoxia to CVS
- Big sympathetic release
- Last ditch effort to stay alive
An excess in fluids will cause an _____
Incr. in BP
An increased Total Peripheral Resistance will lead to…
An increase in MAP
The bainbridge reflex prevents…
Damming of blood in veins, atria, and pulmonary circuit
decreased sympathetic activity gives an increase in MAP. T/F
False
Positive chronotrophic agents:
- Increased temperature at SA node
- Sympathetic nervous system input to SA node
- Increased plasma Ca2+
- Adrenaline
Increased plasma K+ is a positive chronotrophic agent. T/F
False
___ inhibits venous return
Gravity
inspiration inhibits venous return. T/F
False
Vasoconstriction inhibits venous return. T/F
False
enlargement of the right atrium during contraction of the right ventricle inhibits venous return. T/F
False
The cerebral reflex involves…
Low blood perfusion of cardiovascular centre
Baroreceptors in the carotid sinus are…
At an appropriate position to protect the brain from changes in pressure
Baroreceptors in the carotid sinus monitor the volume of blood in the carotid arteries. T/F
False
Collectivly,
Increased venous pressure
Local inflammation resulting in ancreased capillary permeability
Surgical removal of lymph nodes and;
Reduced plasma protein concentrations can cause…
Oedema
