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Questions and Answers
What primarily regulates blood flow in resting skeletal muscle?
What primarily regulates blood flow in resting skeletal muscle?
- Increased metabolic activity
- External compression by surrounding tissues
- Sympathetic nervous system activity (correct)
- Increased heart rate
What happens to capillary perfusion during muscle activity?
What happens to capillary perfusion during muscle activity?
- More capillaries are perfused (correct)
- Blood flow decreases
- All capillaries are constricted
- There is no change in perfusion
What is the primary effect of metabolic byproducts on blood flow regulation during exercise?
What is the primary effect of metabolic byproducts on blood flow regulation during exercise?
- Decrease blood viscosity
- Cause vasodilation of arterioles (correct)
- Narrow blood vessels
- Increase sympathetic nervous system activity
What is reactive hyperemia?
What is reactive hyperemia?
How do isotonic exercises affect blood flow in skeletal muscles?
How do isotonic exercises affect blood flow in skeletal muscles?
What happens to blood flow in skeletal muscles during rest due to sympathetic activation?
What happens to blood flow in skeletal muscles during rest due to sympathetic activation?
What is the role of capillaries in skeletal muscle circulation?
What is the role of capillaries in skeletal muscle circulation?
What physiological change occurs during active hyperemia?
What physiological change occurs during active hyperemia?
Which of the following statements is true regarding terminal arterioles in skeletal muscle?
Which of the following statements is true regarding terminal arterioles in skeletal muscle?
What characterizes isometric contractions in terms of blood flow?
What characterizes isometric contractions in terms of blood flow?
What is the primary function of the tight junctions in cerebral capillary endothelial cells?
What is the primary function of the tight junctions in cerebral capillary endothelial cells?
Which of the following factors allows for the autoregulation of cerebral blood flow?
Which of the following factors allows for the autoregulation of cerebral blood flow?
What type of substances can readily diffuse across the capillary wall of the blood-brain barrier?
What type of substances can readily diffuse across the capillary wall of the blood-brain barrier?
Which condition is primarily associated with ischemic strokes?
Which condition is primarily associated with ischemic strokes?
How do cerebral resistance vessels respond to increased levels of Pco2?
How do cerebral resistance vessels respond to increased levels of Pco2?
What role do transporters in the blood-brain barrier serve?
What role do transporters in the blood-brain barrier serve?
What is a significant outcome of hypertension in relation to stroke risk?
What is a significant outcome of hypertension in relation to stroke risk?
What impact does decreased Pco2 have on the cerebral blood vessels?
What impact does decreased Pco2 have on the cerebral blood vessels?
How does the chemical barrier of the blood-brain barrier operate?
How does the chemical barrier of the blood-brain barrier operate?
Which area is categorized as a sensory circumventricular organ (CVO)?
Which area is categorized as a sensory circumventricular organ (CVO)?
What is the primary action of endothelial-derived hyperpolarizing factor (EDHF)?
What is the primary action of endothelial-derived hyperpolarizing factor (EDHF)?
Which type of prostaglandins are known to function as potent vasodilators?
Which type of prostaglandins are known to function as potent vasodilators?
What physiological response occurs during sudden loss of blood volume?
What physiological response occurs during sudden loss of blood volume?
How do endothelins contribute to vascular function?
How do endothelins contribute to vascular function?
What mechanism causes edema during heart failure?
What mechanism causes edema during heart failure?
Which of the following agents can induce vasoconstriction via increased calcium levels?
Which of the following agents can induce vasoconstriction via increased calcium levels?
How does calcium concentration affect blood vessel diameter?
How does calcium concentration affect blood vessel diameter?
What role do prostaglandins play in endothelial function?
What role do prostaglandins play in endothelial function?
What is the consequence of decreased Pc in the venous system during blood loss?
What is the consequence of decreased Pc in the venous system during blood loss?
Which description accurately reflects the blood-brain barrier's function?
Which description accurately reflects the blood-brain barrier's function?
What physiological change occurs in cerebral blood flow when carbon dioxide levels increase?
What physiological change occurs in cerebral blood flow when carbon dioxide levels increase?
During which state does the brain show higher blood flow to the frontal areas?
During which state does the brain show higher blood flow to the frontal areas?
How does the brain adapt its blood flow during specific experiences such as reading or writing?
How does the brain adapt its blood flow during specific experiences such as reading or writing?
What is a characteristic of cerebral blood flow in a patient experiencing a permanent coma?
What is a characteristic of cerebral blood flow in a patient experiencing a permanent coma?
What is the relationship between carbon dioxide levels in the arterial blood and cerebral blood flow?
What is the relationship between carbon dioxide levels in the arterial blood and cerebral blood flow?
What happens to cerebral blood flow during a stroke?
What happens to cerebral blood flow during a stroke?
What factors could lead to changes in blood flow dynamics during muscle activity?
What factors could lead to changes in blood flow dynamics during muscle activity?
How is metabolic control of blood flow primarily achieved?
How is metabolic control of blood flow primarily achieved?
What role does the sympathetic nervous system have regarding blood flow during rest?
What role does the sympathetic nervous system have regarding blood flow during rest?
Which statement differentiates isotonic and isometric exercises in terms of blood flow?
Which statement differentiates isotonic and isometric exercises in terms of blood flow?
What is the driving factor behind active hyperemia in skeletal muscles?
What is the driving factor behind active hyperemia in skeletal muscles?
During exercise, how do the arterioles respond in relation to metabolic control of blood flow?
During exercise, how do the arterioles respond in relation to metabolic control of blood flow?
What is the relationship between capillary perfusion and muscle activity?
What is the relationship between capillary perfusion and muscle activity?
What mechanism primarily controls blood flow in skeletal muscles during rest?
What mechanism primarily controls blood flow in skeletal muscles during rest?
Which physiological response is associated with reactive hyperemia?
Which physiological response is associated with reactive hyperemia?
What happens to capillary perfusion levels during periods of muscle rest?
What happens to capillary perfusion levels during periods of muscle rest?
Which factor primarily triggers an increase in sympathetic nervous system activity regarding blood flow?
Which factor primarily triggers an increase in sympathetic nervous system activity regarding blood flow?
How does metabolic control influence local blood flow during active muscle contractions?
How does metabolic control influence local blood flow during active muscle contractions?
What is the primary role of the sympathetic nervous system when arterial pressure is low?
What is the primary role of the sympathetic nervous system when arterial pressure is low?
Which type of exercise is specifically associated with active hyperemia?
Which type of exercise is specifically associated with active hyperemia?
What is the difference between active hyperemia and reactive hyperemia?
What is the difference between active hyperemia and reactive hyperemia?
How does skeletal muscle blood flow change immediately after exercise stops?
How does skeletal muscle blood flow change immediately after exercise stops?
What best characterizes the blood flow dynamics during isotonic exercises?
What best characterizes the blood flow dynamics during isotonic exercises?
Which statement best describes the role of local metabolites during exercise?
Which statement best describes the role of local metabolites during exercise?
What type of exercise is primarily linked to reactive hyperemia?
What type of exercise is primarily linked to reactive hyperemia?
Which physiological phenomenon is likely to occur immediately after prolonged isotonic exercise?
Which physiological phenomenon is likely to occur immediately after prolonged isotonic exercise?
Flashcards
Calcium and Vasoconstriction
Calcium and Vasoconstriction
Increased calcium concentration in cells leads to blood vessel constriction.
Calcium and Vasodilation
Calcium and Vasodilation
Decreased calcium concentration in cells causes blood vessels to widen.
Prostaglandins
Prostaglandins
Molecules produced by the endothelium; some cause vessel widening (vasodilation) and others cause vessel narrowing (vasoconstriction).
Endothelium-Derived Hyperpolarizing Factor (EDHF)
Endothelium-Derived Hyperpolarizing Factor (EDHF)
A vasodilator released by the endothelium which opens potassium channels in smooth muscle cells.
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Endothelins
Endothelins
Potent vasoconstrictors produced by endothelial cells.
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Sudden Blood Loss and Venous Pressure
Sudden Blood Loss and Venous Pressure
During a sudden loss of blood volume, venous pressure drops more compared to arterial pressure.
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Heart Failure and Fluid Edema
Heart Failure and Fluid Edema
In heart failure, fluid backs up in the venous system raising pressure in venous vessels, pushing fluid out of capillaries causing edema.
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Fluid Movement in Capillaries
Fluid Movement in Capillaries
The balance between pressure inside capillaries (Pc) and the pressure outside (interstitial fluid pressure) and osmotic pressure, decides the net movement of fluid in capillary beds.
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Blood-Brain Barrier (BBB)
Blood-Brain Barrier (BBB)
A selective barrier that protects the brain from harmful substances in the bloodstream.
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Bulk Flow
Bulk Flow
Movement of large quantities of fluid across the capillary wall, blocked by tight junctions in the BBB.
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Diffusion
Diffusion
Movement of small, lipid-soluble molecules like O2 and CO2 across the capillary wall.
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Transporters (BBB)
Transporters (BBB)
Specialized proteins in the BBB that facilitate the movement of glucose, amino acids, and other important molecules.
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Cerebrovascular Center (CVOs)
Cerebrovascular Center (CVOs)
Locations where the Blood-Brain Barrier is interrupted to allow direct blood-brain interaction.
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Cerebral Blood Flow Autoregulation
Cerebral Blood Flow Autoregulation
The brain's ability to maintain stable blood flow even when blood pressure changes significantly.
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Cerebral Autoregulation Range
Cerebral Autoregulation Range
The range of blood pressure (60-150 mmHg) over which the brain maintains stable blood flow.
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PCO2 Sensitivity in Brain Blood Flow
PCO2 Sensitivity in Brain Blood Flow
Brain blood vessels are highly sensitive to changes in carbon dioxide partial pressure (PCO2), causing vasodilation or vasoconstriction.
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Ischemic stroke
Ischemic stroke
A stroke caused by a blockage in the blood supply to the brain.
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Stroke Pathophysiology
Stroke Pathophysiology
Poor blood flow to the brain, causing cell death, typically due to a blood clot or blockage.
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Stroke Risk Factors
Stroke Risk Factors
Conditions like high blood pressure, obesity, and high blood pressure can increase stroke risk.
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Skeletal Muscle Circulation
Skeletal Muscle Circulation
Skeletal muscles rely heavily on blood vessels to deliver oxygen and nutrients, remove waste, and regulate temperature.
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Capillary Network
Capillary Network
Skeletal muscles have a dense network of capillaries to efficiently exchange substances with muscle fibers.
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Local Controls (Muscle)
Local Controls (Muscle)
Muscle's blood flow is adjusted in response to its metabolic activity. Inactive muscles have constricted arterioles, and active muscles have dilated arterioles.
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Local Metabolites
Local Metabolites
Byproducts of muscle activity (e.g., CO2, lactate). They cause arterioles to dilate, increasing blood flow.
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Central Controls
Central Controls
The sympathetic nervous system (SNS) controls background blood flow to muscle, which can be increased in an emergency (low blood pressure).
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Active Hyperemia
Active Hyperemia
Increased blood flow caused by increased cellular activity, like in exercising muscles.
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Reactive Hyperemia
Reactive Hyperemia
Increased blood flow to an area after a period of reduced blood flow, such as after a temporary blockage.
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Isotonic Exercise
Isotonic Exercise
Exercise involving rhythmic cycles of muscle contraction and relaxation, such as jogging or swimming, leading to a variable blood flow pattern.
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Isometric Exercise
Isometric Exercise
Exercise involving muscle contraction without changing muscle length, potentially temporarily reducing blood flow, such as weightlifting
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Role of Sympathetic Nervous System (Exercise)
Role of Sympathetic Nervous System (Exercise)
At rest, the sympathetic nervous system controls blood flow to muscles. During exercise, local metabolites take over, influencing vasodilation.
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Active Hyperemia
Active Hyperemia
Increased blood flow to an area due to increased metabolic activity (e.g., during exercise).
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Reactive Hyperemia
Reactive Hyperemia
Increased blood flow after a period of reduced blood flow (e.g., during a brief blockage).
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Isotonic Exercise
Isotonic Exercise
Exercise involving rhythmic contraction and relaxation (e.g., jogging).
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Active Hyperemia (Process)
Active Hyperemia (Process)
Increased blood flow in muscles, with a period of increased blood flow to the muscles, followed by an elevated level of blood flow well after the exercise. This is in contrast to a rapid increase and decrease of blood flow.
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Local Metabolites (Blood Flow)
Local Metabolites (Blood Flow)
Products of cell activity (e.g., CO2, lactate) that cause blood vessel dilation and increased blood flow.
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Stroke Warning Signs
Stroke Warning Signs
Sudden headache, facial drooping (one side), weakness (one side), slurred speech, blurred vision.
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Stroke Prevention
Stroke Prevention
Measures to reduce clot formation and ischemic events.
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Skeletal Muscle Circulation
Skeletal Muscle Circulation
Unique network of blood vessels surrounding muscle fibers to support high metabolic needs.
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Muscle Capillary Arrangement
Muscle Capillary Arrangement
Skeletal muscle fibers are surrounded by 3-4 capillaries each, ensuring efficient oxygen delivery and waste removal.
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Local Blood Flow Control
Local Blood Flow Control
Blood flow to muscles is adjusted based on their activity level.
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Active Muscle Vasodilation
Active Muscle Vasodilation
Increased metabolic activity in muscle leads to increased blood flow to the area.
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Central Blood Flow Control
Central Blood Flow Control
Sympathetic nervous system regulates baseline blood flow to muscle; increases during emergencies.
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Brain Blood Flow and CO2
Brain Blood Flow and CO2
Brain blood flow directly relates to the concentration of carbon dioxide in the blood (PCO2). Higher CO2 leads to increased blood flow.
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Brain Blood Flow Adaptation
Brain Blood Flow Adaptation
The brain dynamically adjusts blood flow based on activity and experience to prioritize blood to specific brain areas.
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Cerebral Blood Flow and Coma
Cerebral Blood Flow and Coma
Assessing brain blood flow patterns can help identify a coma, as there are distinct flow patterns in permanent comas compared to normal shifts.
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Stroke and Blood Flow
Stroke and Blood Flow
Stroke is related to abnormal or inadequate blood flow to the brain. Changes in blood flow patterns reveal this.
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CO2 and Cerebral blood flow relationship
CO2 and Cerebral blood flow relationship
A linear relationship exists between the partial pressure of CO2 (PCO2) in arterial blood and cerebral blood flow.
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Brain blood flow redistribution
Brain blood flow redistribution
In response to mental activity or external stimuli, the brain can adjust blood flow to different regions according to the regions in need.
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Lecture #26: Vascular Phys II & Special Circulations
- Lecture delivered by Julia M. Hum, Ph.D.
- Monday/Wednesday/Friday schedule: 2:00 PM - 2:50 PM
- Office hours: Monday/Wednesday/Friday, 11:00 AM - 12:00 PM
- Email: jmhum@marian.edu
- Website: marian.edu/medicalschool
Endothelial Control of Blood Flow: Prostaglandins
- Endothelium produces prostaglandins.
- Prostaglandins are a family of molecules that can act as vasodilators or vasoconstrictors.
- The effect depends on the specific prostaglandin type and receptor.
Endothelial Control of Blood Flow: EDHF
- "Endothelium-Derived Hyperpolarizing Factor" is a vasodilator.
- Opens K+ channels in vascular smooth muscle cells (VSMCs).
- Leads to hyperpolarization, limiting Ca²⁺ permeability, decreasing intracellular Ca²⁺ levels.
Endothelial Control of Blood Flow: Endothelins
- A potent vasoconstrictor.
- Synthesized and released by endothelial cells in response to various factors (e.g., Ang-II, trauma, hypoxia).
- Binds to ETA receptors on VSMCs, triggering intracellular Ca²⁺ release via IP₃ pathway.
Fluid Movement in Capillary Beds
- Sudden blood loss reduces venous pressure.
- Fluid shifts from interstitium into blood vessels to compensate.
- Heart failure: Fluid builds up in the venous system.
- Fluid is then pushed into the interstitium leading to edema.
What's Next?
- Dr. Skinner's lectures, focusing on anticoagulants and antiplatelets begin Monday and Wednesday.
- Students are encouraged to review Dr. Skinner's case studies if missed.
L26: Learning Objectives
- Blood-brain barrier function.
- Comparison of sensory and secretory circumventricular organs (CVOs).
- Autoregulation of cerebral blood flow in relation to CO₂.
- Significance of regional patterns in cranial blood flow.
- Mechanism of stroke related to blood clots
- Description of skeletal vasculature.
- Contrasting local vs. central control over skeletal muscle circulation.
- Differentiating isometric vs. isotonic muscle exercise and its effects on hyperemia.
Circulation Needs
- Anatomical considerations of blood flow pathways.
- Regulation of blood flow to organs.
- Local metabolic control over blood flow.
- Neural control of blood flow.
- Capacity to respond to blood pressure.
- Autoregulation capability of circulatory system.
"Special" Circulations
- List of specific circulations (cerebral, hepatic, skeletal muscle, coronary, splanchnic, and renal).
Cerebral Circulation
- Brain accounts for 2% of body weight but needs 15% of cardiac output.
- High metabolic rate driving demand.
- Limited metabolic reserves hence heavily dependent on cerebral circulation.
Blood Brain Barrier
- Characteristic feature of brain vasculature.
- Prevents solutes in capillaries from entering brain extracellular fluid.
- Unique chemical barriers exist, with enzymes to degrade hormones and NTs.
- Protects brain from abrupt changes in blood composition.
- Can become damaged in specific brain regions.
- Composed of capillaries featuring tight junctions between cells to limit the passage of large molecules.
Blood Brain Barrier - CVOs
- CVOs (Circumventricular organs): allow direct access between cerebrospinal fluid and blood.
- Categorized as sensory and secretory CVOs for sensing certain blood factors.
- Sensory CVOs (hypothalamus, brainstem) are responsive to various substances and regulate hormones.
- Secretory CVOs (hypothalamus, posterior pituitary, pineal gland) release and regulate hormones.
Cerebral Blood Flow Autoregulation
- Maintains stable blood flow to the brain despite fluctuations in mean arterial pressure (60-150mmHg).
- Wider autoregulatory range than in other vascular beds.
Cerebral Blood is Sensitive to Pco2
- Cerebral vessels dilate in response to metabolic change, especially CO2 levels.
- High CO2 promotes vasodilation, increasing blood flow.
- Low CO2 causes vasoconstriction decreasing blood flow.
Regional Changes in Cranial Blood Flow
- Blood flow patterns shift based on cognitive/physical activity.
- Flow can remain steady during focused mental activities.
- Changes in blood flow can happen in case of injury or disease.
Clinical Connection: Stroke
- Stroke is a leading cause of serious disability.
- Causes of stroke include cardiovascular disease, thrombotic events, or embolic events leading to poor brain circulation.
- Ischemic stroke is the most common type, accounting for 87% of all strokes.
- Prevention strategies include measures to lessen clots, lower blood pressure, and lower cholesterol.
- Medical interventions, Lifestyle modifications,
Skeletal Muscle Circulation
- Muscle tissue is richly supplied with capillaries for efficient oxygen and nutrient exchange to facilitate metabolic demands.
- Skeletal vasculature is supplied by arteries that branch and form arterioles.
- Arterioles in turn create capillary networks, optimizing oxygen/nutrient exchange and waste removal.
Skeletal Muscle Circulation - Regulation: Local vs Central
- Local control:
- Resting muscle: limited capillary perfusion due to vasoconstriction in terminal arterioles.
- Active muscle: increased metabolite concentrations trigger vasodilation, increasing capillary perfusion for heightened metabolic activity.
- Central control:
- Sympathetic nervous system (SNS) maintains minimal blood flow at rest.
- During activity, the local control factors take over, increasing blood flow.
Skeletal Muscle - Extravascular Compression
- Contractions compress blood vessels.
- Isometric exercises inhibit blood flow (short term).
- Active hyperemia (increased blood flow after exercise) occurs as blood vessel constriction relaxes.
- Reactive hyperemia (temporary increase in blood volume) occurs after an occlusion.
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