Movement Through the Capillary Wall

These flashcards cover the key concepts related to the movement of fluids through capillary walls, focusing on the processes of diffusion, filtration, and reabsorption, as well as the pressures involved.

What are the three main processes of movement through capillary walls?

Diffusion, Filtration, Reabsorption.

What is diffusion?

The movement of a substance from an area of high concentration to an area of low concentration.

What does hydrostatic pressure refer to in the context of filtration?

The pressure exerted by a fluid at rest and is a key factor in the filtration process.

In which part of the body does diffusion occur between alveoli and capillaries?

In the lungs.

What gas moves from the capillary to the alveolus?

Carbon dioxide (CO2).

What gas moves from the alveolus to the capillary?

Oxygen.

Does diffusion require energy?

No, diffusion does not require energy.

What is hydrostatic pressure?

The pressure exerted by a fluid within a system.

What is colloid hydrostatic pressure (CHP)?

The pressure of blood inside the capillary.

What is interstitial fluid hydrostatic pressure (IHP)?

The pressure of fluid outside the capillary in the interstitial space.

How is net hydrostatic pressure calculated?

Net hydrostatic pressure = colloid hydrostatic pressure (CHP) - interstitial fluid hydrostatic pressure (IHP).

What is the direction of movement during filtration?

From inside the capillary to outside.

How can hydrostatic pressure be illustrated with a garden hose analogy?

The pressure inside the hose is like colloid hydrostatic pressure, while the pressure in the surrounding water is like interstitial fluid hydrostatic pressure.

What happens to fluid in a hose with tiny holes under pressure?

Fluid will pass out through the holes due to higher internal pressure compared to external pressure.

What is the role of the alveolar endothelium in gas exchange?

It allows gases to diffuse through its thin cells during the exchange process.

What is the significance of capillary walls in filtration?

They allow for the movement of fluid based on hydrostatic pressure differences.

What is reabsorption in the context of capillary movement?

The process by which materials are taken back into the capillary from the surrounding tissue.

What is the primary driving force for filtration in capillaries?

Hydrostatic pressure.

What is the relationship between concentration gradients and diffusion?

Substances move along their concentration gradient from high to low concentration.

What type of cells facilitate gas diffusion in the alveoli?

Thin endothelial cells.

What is the effect of increased hydrostatic pressure in capillaries?

It promotes the filtration of fluid out of the capillaries.

What is the role of interstitial fluid in capillary function?

It exerts pressure that influences fluid movement into and out of capillaries.

What does osmotic pressure do?

Osmotic pressure pulls water from areas of low osmotic pressure to areas of high osmotic pressure.

How does osmotic pressure affect water movement?

Water moves towards areas of high osmotic pressure, which contain fluids with many dissolved substances.

What is an example of osmotic pressure in action?

In a beaker with a balloon filled with a sugary solution, water from outside the balloon moves in due to higher osmotic pressure inside the balloon.

What is blood colloid osmotic pressure (BCOP)?

BCOP is the osmotic pressure inside a capillary, which is higher due to dissolved substances like plasma proteins.

What is interstitial fluid osmotic pressure (IFOP)?

IFOP is the osmotic pressure outside the capillary.

What is the net colloid osmotic pressure?

Net colloid osmotic pressure is the difference between blood colloid osmotic pressure and interstitial fluid osmotic pressure.

What is reabsorption in the context of osmotic pressure?

Reabsorption is the movement of fluid from outside to inside the capillary, driven by osmotic pressure.

What two forces oppose each other in capillary filtration?

Hydrostatic pressure pushes water out of the capillary, while osmotic pressure pulls water into the capillary.

What is net filtration pressure?

Net filtration pressure is the net hydrostatic pressure minus the net colloid osmotic pressure.

What is vascular regulation?

Vascular regulation refers to factors that directly alter blood flow and blood pressure in blood vessels.

What are the three mechanisms of vascular regulation?

The three mechanisms are autoregulatory processes, nervous system influences, and endocrine system influences.

How can heart activity affect blood flow?

Changes in heart activity can modify blood flow and blood pressure.

What role do autoregulatory processes play in vascular regulation?

Autoregulatory processes adjust blood flow based on the needs of tissues.

How does the nervous system influence vascular regulation?

The nervous system can alter blood vessel diameter and blood flow through sympathetic and parasympathetic responses.

What is the role of the endocrine system in vascular regulation?

The endocrine system releases hormones that can affect blood vessel constriction and dilation.

What happens if net hydrostatic pressure equals net colloid osmotic pressure?

If they are equal, no filtration will take place.

What is the effect of high osmotic pressure in a solution?

High osmotic pressure in a solution indicates a high concentration of dissolved substances, which attracts water.

What is the significance of plasma proteins in blood osmotic pressure?

Plasma proteins contribute to the higher osmotic pressure inside capillaries, helping to retain fluid within the bloodstream.

What is the relationship between osmotic pressure and fluid balance?

Osmotic pressure plays a crucial role in maintaining fluid balance between blood vessels and surrounding tissues.

What is a semi-permeable membrane?

A semi-permeable membrane allows certain substances, like water, to pass through while blocking others.

What is autoregulation in the context of blood vessels?

The ability of blood vessels to respond on their own to changes in metabolic activity without input from the nervous or endocrine systems.

How does blood flow adjust during exercise?

Blood flow adjusts to meet changing metabolic demands through autoregulation.

What are the two main factors that affect blood flow and blood pressure in autoregulation?

Local factors within and around the blood vessels.

What role do arterioles play in autoregulation?

Arterioles adjust their diameter to regulate blood flow through the capillaries.

What are pre-capillary sphincters?

Rings of smooth muscle at the openings of capillaries that can contract and relax to adjust blood flow.

What is the effect of vasodilation?

Widening of blood vessels to allow more blood flow.

What is the effect of vasoconstriction?

Narrowing of blood vessels, resulting in reduced blood flow.

What are chemical mediators in the context of autoregulation?

Chemicals released locally that help adjust blood flow by causing vasodilation or vasoconstriction.

How do local cells influence autoregulation?

They release chemical mediators that affect blood vessel diameter and blood flow.

What is the relationship between metabolic activity and blood flow?

Increased metabolic activity requires increased blood flow, which is regulated through autoregulation.

What happens to blood flow when chemical mediators cause vasoconstriction?

Blood flow is reduced due to the narrowing of blood vessels.

Why is autoregulation important for tissues?

It allows tissues to receive adequate blood supply based on their metabolic needs.

What is vasodilation?

The widening of blood vessels.

What chemical mediator can cause vasodilation due to exercise?

Lactic acid.

How does lactic acid affect blood flow during exercise?

It causes arterioles and pre-capillary sphincters to widen, increasing blood flow to flush away lactic acid and deliver more oxygen.

Which mediator is released from mast cells and contributes to vasodilation?

Histamine.

What role does nitric oxide play in blood vessels?

It causes vasodilation when released from endothelial cells.

What effect do increased levels of carbon dioxide have on blood vessels?

They cause vasodilation.

What happens to blood vessels when oxygen levels decrease?

Vasodilation occurs.

What is vasoconstriction?

The narrowing of blood vessels.

Which chemical mediator is released from activated platelets and causes vasoconstriction?

Thromboxane.

What is the role of endothelin in blood vessels?

It causes vasoconstriction when released from damaged endothelial cells.

What is the purpose of vasoconstriction during blood vessel damage?

To reduce blood flow and minimize blood loss.

Where is the vasomotor centre located?

In the medulla oblongata of the brain.

What type of receptors provide input to the vasomotor centre?

Baroreceptors and chemoreceptors.

What is the primary nervous system involved in vascular regulation?

The sympathetic nervous system.

What is vasomotor tone?

The continual state of partial constriction of arterioles due to constant sympathetic stimulation.

What happens to arterioles in the absence of sympathetic activation?

They would be wider than they are under sympathetic stimulation.

How do axons from the vasomotor centre travel to the blood vessels?

They travel down from the brain into the spinal cord and then out to the arterioles.

Are there many parasympathetic axons involved in vascular regulation?

No, hardly any parasympathetic axons go to blood vessels.

What is the effect of sympathetic stimulation on arterioles?

It causes them to be constantly partially constricted.

What is the main function of the vasomotor centre?

To regulate blood vessel diameter based on blood pressure and chemistry.

What happens to blood vessels during an inflammatory response?

Histamine is released, causing vasodilation.

What is the effect of tonic sympathetic input on arterioles?

It causes slight constriction of the arterioles.

What happens to arterioles with increased sympathetic stimulation?

The smooth muscle contracts more, leading to greater vasoconstriction and narrower arterioles.

What occurs in arterioles with reduced sympathetic stimulation?

The smooth muscle is less contracted, resulting in vasodilation.

What would happen if an arteriole received no sympathetic stimulation?

It would be maximally dilated, with no further dilation possible.

What neurotransmitter is released by sympathetic axons to cause vasoconstriction?

Noradrenaline.

What type of receptors does noradrenaline act on in arterioles?

Alpha 1 receptors on the smooth muscle in the arteriole wall.

What is the exception to the typical sympathetic release of noradrenaline?

Some sympathetic nerve cells release acetylcholine (ACh) instead.

What effect does acetylcholine have on arterioles in skeletal muscle?

It causes vasodilation by acting on beta 2 receptors.

In which other area besides skeletal muscle do arterioles experience vasodilation due to ACh?

In the brain.

Why is vasodilation in skeletal muscle and the brain important during sympathetic activation?

These tissues need increased blood flow for oxygen and nutrients during emergencies.

What is the primary role of the sympathetic nervous system?

To prepare the body for 'fight-or-flight' responses.

What is the result of sympathetic activation on blood pressure?

It generally increases blood pressure throughout the body.

What is the function of the vasomotor center located in the medulla oblongata?

It regulates sympathetic output to arterioles.

How many nerve cells are typically involved in the sympathetic pathway to arterioles?

Two nerve cells.

What happens to arterioles during sympathetic activation?

Most arterioles undergo vasoconstriction, increasing overall blood pressure.

What is the physiological significance of vasodilation in the brain during sympathetic activation?

It ensures that the brain receives adequate blood supply during stress or emergencies.

What is the relationship between sympathetic stimulation and arteriole diameter?

Increased sympathetic stimulation leads to decreased diameter (vasoconstriction), while reduced stimulation leads to increased diameter (vasodilation).

What is the primary neurotransmitter involved in vasodilation of arterioles in skeletal muscle?

Acetylcholine (ACh).

What happens to the smooth muscle in arterioles during vasodilation?

The smooth muscle relaxes, allowing the arteriole to widen.

What hormones cause vasoconstriction?

Adrenaline, noradrenaline, and antidiuretic hormone (ADH).

How does ADH affect blood pressure?

ADH causes increased water reabsorption in the kidneys, indirectly increasing blood pressure.

What is the renin-angiotensin-aldosterone system (RAA)?

A system involved in vascular regulation, involving the liver, kidneys, adrenal glands, lungs, and arterioles.

What substance does the liver produce in the RAA system?

Angiotensinogen, an inactive plasma protein.

What triggers the release of renin from the kidneys?

Reduced blood flow through the kidneys due to low blood pressure.

What does renin convert angiotensinogen into?

Angiotensin I.