Physiology Flashcards
According to Fick’s law, what two things is the diffusion of small, water-soluble substances across a capillary wall dependent on?
Permeability and the concentration gradient
Ultrafiltration typically occurs at the (arteriolar/venular) end of capillary beds?
Arteriolar end
What occurs at the venular end of capillary beds?
Reabsorption
How are exchangeable proteins typically moved across capillary walls?
Vesicular transport
(T/F) Plasma proteins generally cannot cross the capillary wall
True
What is the term for the osmotic pressure due to the presence of colloids dissolved in the blood plasma?
Oncotic pressure
What results from the increased oncotic pressure contained in capillaries due to the inability of colloids to readily diffuse across the capillary wall?
Tendency for movement of water into capillaries
At the arteriolar end of a capillary, the hydrostatic pressure outward is (higher/lower) than the oncotic pressure inward, resulting in ultrafiltration predominating.
Higher
At the venular end of a capillary, the hydrostatic pressure outward is (higher/lower) than the oncotic pressure inward, resulting in reabsorption predominating.
Lower
What type of vessels collect the small volume of fluid and plasma protein that is filtered but not absorbed by capillaries?
Lymphatic vessels
What is the term for the clinical condition in which excess fluid accumulates in the tissues, usually in the interstitial spaces?
Edema
Abnormalities of which Starling force causes the forcing of excess fluid out of the capillaries?
Hydrostatic forces
Right sided heart failure tends to result in high pressure edema, describe the issue.
Pressure in veins is too high → hydrostatic pressure on venular end is too high → decreased reabsorption → edema
What type of Starling force is primarily affected by hypoalbuminemia?
Oncotic pressure
Increased capillary pressure ________ (favors/diminishes) fluid filtration into tissues and __________ (favors/diminishes) reabsorption from tissues.
Favors, diminishes
Pulmonary edema is associated with right/left heart failure.
Left
Edema of what is promoted by right heart failure?
Systemic organs; liver, GI tract
What is released in immune hypersensitivity/allergic reactions that increases vascular permeability leading to edema?
Histamine
The highest level of vascular control is regulation by hormones (Epinephrine, norepinephrine, and angiotensin II) and what type of nerves?
Vasomotor nerves
What are the two principal factors responsible for basal vascular tone?
Tonic sympathetic autonomic nervous system activity and arteriolar smooth muscle cell myogenic activity
An increase in alpha1 receptor activity leads to what? What effect on resistance and blood flow does that then lead to?
Vasoconstriction; increased resistance and decreased blood flow
What two things can cause passive vasodilation?
Decreased alpha1 receptor activity and increased blood pressure
What does increased beta2 receptor activity and increased cholinergic receptor activity cause?
Active vasodilation
Vasodilation is associated with ________ (increased/decreased) resistance and __________ (increased/decreased) blood flow.
Decreased resistance, increased blood flow
In what two areas are high-pressure baroreceptors located in the body?
Carotid sinus and aortic arch
What type of baroreceptors are largely located on the venous side of systemic circulation?
Low-pressure baroreceptors
Besides circulatory effects, what other effects do low-pressure baroreceptors have?
Renal
What type of hormones do low-pressure baroreceptors produce changes in the secretion of?
Hormones that control retention and intake of salt and water
What two receptor families does acetylcholine interact with?
Nicotinic and muscarinic
What receptor family does norepinephrine interact with?
Adrenergic
What are the 4 peripheral effector organs in the neural control of arterial pressure?
Heart, arteries, veins, and adrenal medulla
Parasympathetic innervations of the heart are restricted to the (atria/ventricles) and exerts a negative/positive chronotropic effect.
Atria, negative
Sympathetic innervations to the heart exert two positive effects on the heart, what are they and what do they mean?
Positive chronotropic → increasing the heart rate; positive inotropic → increasing the force of contraction
What structure in the microstructure of an arterial wall provides control of resistance to flow, protection from thrombosis, and regulation of permeability?
Endothelial cells
What are the three kinds of autonomic vasomotor nerves?
Sympathetic vasoconstrictor nerves, sympathetic vasodilator nerves, and parasympathetic vasodilator nerves
What type of innervation do most blood vessels only receive?
Sympathetic
What type of sympathetic vasomotor fibers make up the majority and are considered the most important physiologically?
Vasoconstrictors
(T/F) Vasodilation is often induced not by vasodilator fibers but by reduced activity in sympathetic vasoconstrictor fibers.
True
Sympathetic vasodilator nerves are only found in what type of tissues?
Skeletal muscle
In what layer of the walls of blood vessels do postganglionic sympathetic neurons predominate?
Tunica adventitia
There are two nerve fiber plexuses that are listed below, give their location within the wall of a blood vessel.
- Primary plexus
- Terminal/ground plexus
- Primary plexus (Middle to outer third of adventitia)
- Terminal/ground plexus (Boundary between the adventitia and media)
What are varicosities?
Neurotransmitter storage sites along the length of a neuron
(T/F) The larger the vessel, the greater its neuroeffector junction (the distance from the axonal varicosity to the vascular smooth muscle effector cells) will be.
True
What is the origin of parasympathetic vasodilator nerves within the brainstem?
Medulla
(T/F) Parasympathetic vasodilator nerves regulate blood flow within specific organs rather than playing a significant role in the regulation of systemic vascular resistance and thereby arterial blood pressure
True
Angiotensin II, epinephrine, norepinephrine, and atrial natriuretic peptide are all examples of what type of agents?
Humoral
(T/F) Humoral agents arrive by way of the circulatory system and are partially under CNS control
True
The combination of the top tier of vascular control coming under CNS control and humoral agents (which are partially under CNS control) means that vascular regulation is largely under control of what part of the body?
Brain
Humoral agents can cause vasodilation, vasoconstriction, or sometimes both depending on what two things?
Agent concentration and receptor subtypes present
Where do humoral and neural influences on vascular control interact frequently?
Nerve terminals
(T/F) Humoral agents only work directly to cause their effects on vascular control i.e. directly bind to a receptor to cause vasodilation, vasoconstriction, or both.
F, can act indirectly i.e. angiotensin II potentiating norepinephrine
Listed below are the different receptors of cardiac/vascular control, give their affinity for norepinephrine (NE) versus epinephrine (E).
- Beta1
- Beta2
- Alpha1 and alpha2
- Beta1 (bind equally with both)
- Beta2 (greater affinity for E)
- Alpha1 and alpha2 (greater affinity for NE)
Listed below are the different receptors of cardiac/vascular control, give their high density locations in the body.
- Beta1
- Beta2
- Alpha1
- Beta1 (Heart)
- Beta2 (Coronary vessels, liver vessels, and vessels of skeletal muscle beds)
- Alpha1 (Most other vessels)
Listed below are the different receptors of cardiac/vascular control, give their effect on the heart/vessels when activated by epinephrine/norepinephrine.
- Beta1
- Beta2
- Alpha1,2
- Beta1 (Sympathetic NS responses in the heart i.e. increased contractility and heart rate)
- Beta2 (Smooth muscle relaxation)
- Alpha1,2 (Smooth muscle constriction in peripheral vessels)
Pair the systemic effects below with the appropriate catecholamine that would induce those effects.
- Increased cardiac output via increased cardiac contractility and heart rate; decreased systemic vascular resistance via vasodilation
- Increased cardiac output via increased cardiac contractility and heart rate; increased systemic vascular resistance via vasoconstriction
- Increased cardiac output via increased cardiac contractility and heart rate; decreased systemic vascular resistance via vasodilation (Epinephrine)
- Increased cardiac output via increased cardiac contractility and heart rate; increased systemic vascular resistance via vasoconstriction (Norepinephrine)
(T/F) Low-pressure baroreceptors are largely located on the venous side of systemic circulation
True
What percentage of change in venous volume must occur before low-pressure baroreceptors are activated?
5-10%
(T/F) Angiotensin II is a powerful vasodilator hormone with important roles in hypovolemia, hypertension, and heart failure.
F, vasoconstrictor
Angiotensin II formation is mediated by endothelial angiotensin converting enzyme (ACE) and what other enzyme?
Renin
Angiotensin II enhances sympathetic nervous system output by potentiating the release of what catecholamine?
Norepinephrine
Angiotensin II not only causes vasoconstriction which increases stroke volume to aid in increasing arterial blood pressure when it falls below normal, it also increases the release of what hormone in the adrenal cortex?
Aldosterone
How does the above hormone (Aldosterone) increase blood volume to increase cardiac output and thus increase arterial blood pressure?
Increases renal sodium and water reabsorption
(T/F) Atrial natriuretic peptide (ANP) is a direct vasodilator
True
What does ANP do to the excretion of urinary sodium and water?
Increases it
What indirect effect does ANP have on angiotensin II?
Suppresses angiotensin II production
What are the overall net effects of ANP on the body?
Lower blood volume and reduce systemic blood pressure
What are nitric oxide, endothelium-derived hyperpolarizing factor (EDHF), and prostacyclin (PGI2) examples of?
Vasodilators of endothelial origin
Angiotensin II, when produced locally, acts as a vasoconstrictor/vasodilator.
Vasoconstrictor`
Endothelin (ET-1) can be a vasoconstrictor or vasodilator depending on what?
Which if its receptors is present
Give examples of markers of high metabolic activity. There are 4 answers.
CO2, lactate, adenosine, and K
What do most of the markers of high metabolic activity (metabolites) do to vessels in terms of contraction/dilation?
Most act as vasodilators
(T/F) Metabolites both exert direct inhibitory effect on contraction of vascular smooth muscle and interrupt the vasoconstrictor signals of the sympathetic nerves.
True
Histamine, bradykinin, serotonin, thromboxane, and platelet activity factor are all examples of what?
Autacoids
What are autacoids?
‘Local hormones’, biological factors that have a brief duration and act near their site of synthesis
Histamine and bradykinin _______ (dilate/constrict) arterioles while __________ (dilating/constricting) venules.
1 - Dilate, 2 - constricting
Serotonin is an arteriolar constrictor that is released in response to what and why?
Released in response to blood vessel damage to prevent blood loss
While the prostaglandin prostacyclin is a vaso________ (dilator/constrictor), the prostaglandin thromboxane is a vaso________ (dilator/constrictor).
1 - Dilator, 2 - constrictor
What mechanism works to stabilize local blood flow in face of large fluctuations in systemic arterial pressure?
Autoregulation
What three organs is the above mechanism prominent in?
Heart, brain, and kidneys
(T/F) Autoregulation does not mean that blood flow is unchangeable at the site of action, only that it is less sensitive to changes in arterial pressure.
True
What is the name for the autoregulatory vasoconstriction that occurs in response to increased perfusion pressure and sudden vessel stretch?
Bayliss myogenic response
What two things mediate the Bayliss myogenic response?
Depolarization and calcium
Within the same myogenic response, a reduction in intravascular pressure results in what to increase local blood flow?
Smooth muscle relaxation → vasodilation
What is reactive hyperemia?
An increase in blood flow in response to a period of vessel occlusion/cessation of flow
(T/F) The longer the period of occlusion, the greater the increase in blood flow above pre-occlusion blood flow.
True
What is the term for an increase in blood flow to match an increase in metabolic activity?
Active hyperemia
Hemorrhagic/hypovolemic shock usually results in __________ (competition/synergism) between global and local control of cardiac/vascular regulation.
Competition
Exercise usually results in ____________ (competition/syngersim) between global and local control of cardiac/vascular regulation.
Synergism
What effect do beta blockers such as propranolol have on the heart?
Decreased heart rate and cardiac output by antagonizing norepinephrine at Beta1 receptors in the heart
Calcium channel blockers would have what effect on vascular regulation?
Block contraction by reducing calcium, prevents vasoconstriction, promotes vasodilation
Nitric oxide donors such as nitroglycerin would have what effect on vascular regulation?
Increase opposition of contractile signaling, prevents vasoconstriction, promotes vasodilation
ACE inhibitors such as enalapril would have what effect on vascular regulation?
Prevents creation of angiotensin II from angiotensin I, prevents vasoconstriction and increased aldosterone, lowers blood pressure
What effect does diuretics have on vascular regulation?
Increased renal sodium/water excretion → decreased blood volume → decreased cardiac output → decreased arterial blood pressure
The ventricles contract, increasing ventricular pressure, to pump blood to the circulation during ____________ and relax, reducing ventricular pressure, to fill with blood during _____________.
Systole, diastole
(T/F) In a resting state, the majority of a patient’s blood volume is in the systemic veins.
True
If the output of the right heart is not equal to the output of the left heart, what can occur overtime?
Congestion
Which of the circulation systems is higher pressure?
Systemic circulation
Differences in what determines the flow within the cardiovascular system?
Pressure
Give the definitions of the variables in BP = CO x R.
- BP
- CO
- R
- BP (Blood pressure)
- CO (Cardiac output)
- R (Systemic vascular resistance)
What is the calculation for BP that contains CO and R?
BP= CO*R
What two factors influence vascular resistance?
Radius of the vessel and viscosity of blood
(T/F) Vascular resistance is directly related to viscosity of blood while inversely related to the radius of the vessel.
True
Give the definitions of the variables in CO = SV x HR
- CO
- SV
- HR
- CO (Cardiac output)
- SV (Stroke volume)
- HR (Heart rate)
What is the calculation for CO knowing SV and HR?
CO= SV*HR
What is the functional unit for cardiac pumping?
Contractile cardiomyocytes
What do specialized cardiomyocytes do for cardiac pumping?
Determine rate of pumping and coordinate pumping
What is the functional unit of contractile cardiomyocytes?
Sarcomere
What type of muscle is found in the heart?
Striated muscle
What features do intercalated discs have that favor cell to cell transmission?
Gap junctions
(T/F) The sinus (SA) node spontaneously depolarizes
True
What electrolyte interacts with ryanodine receptors on the sarcoplasmic reticulum of cardiomyocytes resulting in a large amount of calcium to be released into the cytosol of the cell?
Calcium
The released calcium interacts with what protein to favor cross bridge cycling, sarcomere shortening, and muscle contraction?
Troponin C
What results from the reduction of cytosolic calcium (which occurs due to sarcolemma calcium channels closing and calcium being pumped back into the sarcoplasmic reticulum) after the contraction phase of excitation-contraction coupling?
Sarcomeres return to resting length, muscle is in a relaxed state
What does enhanced contractility lead to that increases stroke volume?
Smaller end systolic volume
(T/F) Contractility to a feature of the myocardium that is independent of preload and afterload.
True
What effect do positive inotropic drugs have on the heart?
Enhance contractility
Give the neurotransmitters for the sympathetic and parasympathetic nervous systems.
Sympathetic - norepinephrine and epinephrine; parasympathetic - acetylcholine
Give the cardiac receptors for the sympathetic and parasympathetic nervous systems.
Sympathetic - beta adrenergic; parasympathetic - muscarinic
Which of the nervous systems (sympathetic or parasympathetic) is a positive chronotrope and which is a negative chronotrope?
Sympathetic - positive; parasympathetic - negative
What is lusitropy?
Myocardial relaxation
Which nervous system (sympathetic or parasympathetic) is a positive lusitrope?
Sympathetic
What does the phosphorylation of myosin ATPase by the sympathetic nervous system increase the rate of?
Contraction
What does the phosphorylation of phospholamban by the sympathetic nervous system increase the rate of?
Relaxation
How does the sympathetic nervous system increase contractility and what does that action result in that increases contractility?
Phosphorylation of calcium channels, results in more calcium → increased contractility
What is the term for the period in time when the ventricles are very high in pressure and volume prior to ejection?
Isovolumetric contraction
What event occurs that causes the volume to finally decrease causing the heart to then enter the ventricular ejection phase?
Pulmonic and aortic valve opening
What simultaneous event(to the described event above) occurs that prevents the ejected blood from regurgitating back into the atriums?
AV valve closure
The opening of the pulmonic and aortic valves can only happen after what?
The pressure in the ventricles exceeds the pressure in the pulmonary artery and aorta
During isovolumetric contraction/relaxation, the AV valves are ________ (open/closed) while the semilunar valves are _______ (open/closed).
Both closed
If you want to increase stroke volume by changing the end diastolic volume, what would you change and how?
Change preload specifically increase preload → increases EDV
If you want to increase stroke volume by changing the end systolic volume, what would you change and how?
Change afterload specifically decrease afterload → decreases ESV and/or change contractility specifically increase contractility → decreases ESV
What two things influence contractility?
Drugs and autonomic nervous system
What is the transportation of oxygen in the air to the cells in the body and transportation of carbon dioxide from the cells back out to the atmosphere?
Respiration
What are the boundaries of the conducting airway?
Rostral - nares, caudal - bronchioles
Why are the conducting airways considered physiological ‘dead space’?
No gas exchange occurs
The alveolar ducts down to the alveoli are what type of airways?
Exchange airways → location of gas exchange
How thick are the alveoli and pulmonary capillaries to facilitate gas exchange?
One cell thick
What do type II pulmonic cells secrete that lowers surface tension to keep the alveoli open?
Surfactant
Distribution of resistance is species-dependent but a great proportion of the resistance for brachycephalic breeds is provided by the ___________ (upper/lower) airways.
Upper
Increased resistance to airflow is __________ (inversely/directly) related to the radius of the airways.
Inversely
Give two examples of diseases that cause impairment of ventilation at the upper conduction airways.
Laryngeal paralysis in dogs and dorsal displacement of the soft palate in horses
What determines alveolar ventilation? Two answers.
Respiratory rate and tidal volume
Contraction of what two muscles results in decreased intrathoracic pressure related to inspiration?
Diaphragm and external intercostal muscles
What is done to enhance inspiration during heavy breathing?
Nasal flare
What muscle system is recruited during heavy breathing to enhance expiration? Don’t need a specific answer.
Abdominal muscles
Alveolar pressure is _________ (greater than/equal to/less than) pleural pressure.
Greater than
(T/F) Pleural pressure is always negative.
True
During inspiration, the alveolar pressure is __________ (higher/equal/lower) than the atmospheric pressure while during expiration it is __________ (higher/equal/lower).
Lower, higher
What is the importance of the pleural pressure being subatmospheric?
Aids in prevention of lung collapse
Respiratory centers in the brain receive information from chemoreceptors to modulate the respiratory rate in response to the levels of what? Three answers.
Oxygen, CO2, and hydrogen ions/acid
What is the term for the additional volume resulting from the deepest possible breath you can take?
Inspiratory reserve volume
What is the term for the volume of air left in the lungs after you exhale your expiratory reserve volume?
Residual volume
The tidal volume of a breath is the addition of what two volumes of air?
Vdead space+Valveolvus
What is the equation for alveolar minute ventilation?
Tidal volume minus dead space volume all multiplied by respiratory rate, Alveolar minute ventilation = (V tidal - V dead space)*RR
What three things can cause alveolar hypoventilation?
Reduced respiratory rate, reduced tidal volume, and increased dead space
What is the primary sign of poor gas exchange at the alveolar-capillary interface?
Cyanosis
What reduction is cyanosis related to?
Reduced partial pressure of oxygen in arterial blood → hypoxemia
What can cause hypoxemia? Four answers.
Reduced inspired oxygen, alveolar hypoventilation, ventilation-perfusion mismatch, and a diffusion barrier
What is the fraction of inspired oxygen (FiO2) when breathing atmospheric air?
0.21
What are the main differences between inspired air and alveolar air?
Alveolar has less oxygen, more water and carbon dioxide than inspired air
What is the driving force for the exchange of gases between alveoli and capillary?
Difference in partial pressure
What is perfusion?
Circulation of blood through a capillary bed
What must perfusion match for effective gas exchange to occur at the alveolar-capillary interface?
Alveolar ventilation
What four factors is diffusion of gases at the alveolar capillary interface dependent on?
Pressure gradient, diffusion coefficient, diffusion distance, and membrane area
Anything that alters tidal volume or respiratory rate will alter what?
Alveolar ventilation)
What can alter perfusion causing a mismatch in ventilation-perfusion?
Anything that alters flow through the capillaries → vasoconstriction, physical obstruction, anatomic abnormalities
Give an example of an anatomic abnormality that would alter perfusion.
Shunt
What do pulmonary arterioles do in response to low partial pressure of oxygen?
Hypoxic pulmonary vasoconstriction → constrict to reduce blood flow
What is the typical response to hypoxic areas in the rest of the body?
Dilate to increase blood flow
What is the result in the constriction of the pulmonary arteries?
Increased pulmonary artery pressure)
What effect can hypoxia mediated vasoconstriction have on the heart?
Increases afterload for right ventricle → right sided heart failure
How do you calculate the A-a gradient?
Subtract the O2 arterial partial pressure from the calculated O2 alveolar partial pressure
What does an increase in the A-a gradient suggest?
Ventilation-perfusion mismatch or a shunt
What is the diffusion coefficient of a gas related to? Two answers.
It’s solubility and molecular weight
What does it mean in terms of the alveolar-capillary interface that the diffusion coefficient for carbon dioxide is 20x that of oxygen?
CO2 diffuses more easily across the alveolar-capillary interface
Since CO2 has a high diffusion coefficient, high arterial CO2 only occurs during hypoventilation and not with diffusion issues, how is this useful?
CO2 arterial partial pressure can be measured via blood gas and reflects the ventilation status of a patient
What two surface areas are important aspects of membrane surface area, which is a determinant of diffusion of gasses at the alveolar-capillary interface?
Alveolar epithelial surface area and capillary endothelial surface area
What two factors contribute to diffusion distance that can be increased with disease?
Alveolar membrane thickness and interstitial space
What pressure does left heart failure increase in the pulmonary capillaries that can lead to the increase in diffusion distance?
Left heart failure increases hydrostatic pressure of pulmonary capillaries → extra fluid in pulmonary interstitial space → increase diffusion distance
