18 Questions
What is responsible for driving fluid out of capillaries?
Hydrostatic pressure
Which of the following substances are exchanged in capillaries?
Glucose and oxygen
What is the mechanism involved in glucose and oxygen exchange in capillaries?
Diffusion
What is the function of baroreceptors in the body?
Detect changes in blood pressure
What is the condition characterized by the accumulation of excess fluid in tissue?
Edema
Which system absorbs about 15% of the fluid filtered by capillaries?
Lymphatic system
What is the main function of the lymphatic system?
Supporting both cardiovascular and immune systems
Which type of shock is triggered by severe immune reactions to antigens?
Anaphylactic shock
What is the main consequence of ischemia?
Restricted blood flow and oxygen in a body part
Which receptors are responsible for sensing pressure changes in the body?
Baroreceptors
What is the consequence of pH down triggering vasodilation?
Increased blood flow
What causes sudden death of brain tissue due to ischemia?
Stroke (cerebral vascular accident)
What is the role of carotid sinuses in the human body?
Monitoring blood pressure
Which nerve transmits information from carotid bodies to the brainstem respiratory center?
Glossopharyngeal nerve (CNIX)
How do veins manage to return blood to the heart despite having low pressure?
Constriction by the sympathetic nervous system and muscle milking
Which nerve transmits information from aortic bodies to the brain?
Vagus nerve (CNX)
In what way do varicose veins differ from normal veins?
They suffer from blood pooling and valve dysfunction
What is a common function of capillaries in the circulatory system?
Exchange of gases and nutrients with tissues
Study Notes
Types of Shock
- Septic shock: caused by bacterial toxins, triggers vasodilation
- Anaphylactic shock: severe immune reaction to antigen, histamine release, vasodilation
- Compensated shock: response to hemostatic mechanisms, causing spontaneous recovery
- Decompensated shock: response fails, life-threatening, positive feedback loops occur, condition worsens, causing damage to cardiac and brain tissue
Brain Blood Flow
- Brain blood flow fluctuates less than in any other organ
- Seconds without oxygen cause loss of consciousness
- 4-5 minutes without oxygen cause brain damage
- The brain regulates its own blood flow, shifting blood to more active parts as needed
- Cerebral arteries dilate and constrict as blood pressure changes
Chemical Stimuli
- pH is the main chemical stimulus
- pH down triggers vasodilation, pH up triggers vasoconstriction
- Change in pH is due to CO2 accumulation or too little CO2 in the blood
Baroreceptors and Chemoreceptors
- Baroreceptors: pressure sensors
- Chemoreceptors: vasodilation/constriction sensors
- Carotid sinuses: baroreceptors in internal carotid artery walls, monitoring blood pressure
- Carotid bodies: chemoreceptors monitoring blood chemistry
- Aortic bodies: chemoreceptors similar to carotid bodies, transmitting information through Vagus nerve (CNX 10)
Lymphatic System
- Plays a vital role in supporting both cardiovascular and immune systems
- Maintains homeostasis by returning most of the fluid diverted back to the blood
Capillaries
- Exchange vessels between blood and tissue fluid
- Exchange gases, nutrients, waste, hormones in capillary beds
- Two-way movement of fluid (in and out)
- Substances exchanged include: H2O, O2, glucose, other nutrients, antibodies, hormones, CO2, and waste
Mechanisms of Capillary Exchange
- Diffusion: glucose and O2 diffuse out of blood, CO2 and waste diffuse in
- Transcytosis: vesicle-mediated transport
- Filtration and reabsorption: fluid filters out of arterial end of capillary and osmotically reenters the venous end
- 2 pressures that determine capillary exchange: hydrostatic pressure and colloid osmotic pressure (COP)
Veins
- Capacitance vessels
- Thin-walled, collapse when empty
- Greater capacity for blood than arteries
- At rest, 64% of blood is in veins
- Low-pressure system
- Sympathetic nervous system innervates tunica media to constrict
- Muscle milking and respiratory pump aid in blood return to heart
Circulatory Routes
- Simple and most common route: heart → arteries → capillaries → veins → heart
- Portal system: blood flows through 2 consecutive capillary networks before returning to heart
Edema
- Accumulation of excess fluid in tissue
- Capillaries absorb about 85% of the fluid they filter, the other 15% is absorbed by the lymphatic system
Test your knowledge on how blood rerouting occurs in response to changes in artery constriction and capillary exchange of substances like water, oxygen, glucose, and hormones. Understand the principles behind pressure changes and blood flow adaptation in different body regions.
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