A&P II Exam #2

What two types of fluid are extracellular fluid?

1) Plasma

2) Interstitial fluid

Where does hydrostatic pressure originate?

The left ventricle

Which end of the circulatory has greater hydrostatic pressure?

The arteriole side

* It’s closer to the heart

What happens to hydrostatic pressure as you lose fluid?

You lose hydrostatic pressure

When is equilibrium in the pressure gradient achieved?

In the middle of the capillaries where fluid doesn’t move

What does hydrostatic pressure allow to occur?

Filtration

What is filtration?

A type of diffusion

* Fluid just passing through

What happens on the venous side of the capillaries?

Reabsorption

Why does reabsorption occur on the venous side?

Because the greater pressure is in the interstitial fluid

What does osmotic pressure do?

It resists fluid to make sure we don’t reabsorb everything

Where does osmotic pressure occur?

In capillaries

How does osmotic pressure change the pressure gradient in capillaries?

It narrows the pressure gradient

What is a visible sign of high blood pressure?

Edema

What is edema caused by?

Too much hydrostatic pressure causing an imbalance between hydrostatic pressure and osmotic pressure

How do arterioles affect the pressure gradient?

They expand and recoil to compensate for pressure

What happens to arterioles that have to constantly compensate for high pressure from high blood pressure?

They lose their elasticity

How do arterioles that have lost their elasticity affect edema?

It causes hydrostatic pressure to never decrease enough for osmotic pressure to take over on the venous side

* Fluid accumulates in the interstitial space

What is fluid through a capillary bed always reflective of?

The cells’ needs

What are the 2 types of vessels in the venous system?

1) Veins

2) Venules

What are venules?

Vessels that come off of capillary beds

* They merge and merge to become veins

Should blood on the venous side be mostly oxygenated or deoxygenated?

Deoxygenated

How much smooth muscle does the tunica in the venous system have?

Just a couple layers

How big is the lumen in veins?

Very big

What does the really large lumen of veins lead to?

Really low pressure

How does the makeup of the layers of the vessels change in types of veins and venules?

It doesn’t

* The layers just get smaller

What is venous return?

The process of getting blood back to the heart at the right atrium

How much blood can the heart eject?

Only the volume of blood returned to it

What are the 2 mechanisms for venous return?

1) Muscular pump

2) Respiratory pump

What is the biggest mechanism for venous return?

The muscular pump

What is the muscular pump?

When muscles contract, they squeeze down on veins due to proximity

What does the muscular pump cause?

An increase in pressure

For efficiency, do you want to increase or decrease venous return?

Increase venous return

What is the respiratory pump?

When you breathe in, you increase the pressure in the thoracic cavity

Do veins store blood?

Yes

* They act as a blood reservoir

Why are veins deeper than arteries in the body?

They hold more blood and are more dangerous to cut

How much blood is stored in veins?

64%

What is flow rate?

The volume of blood moving through a vessel

What is resistance?

The opposition of blood flow in a vessel

What is blood pressure?

The force of blood moving through a vessel

What is mean arterial pressure (MAP)?

The average pressure in the arteries

What 3 factors work together to create mean arterial pressure?

1) Flow rate

2) Resistance

3) Blood pressure

What is mean arterial pressure an indication of?

Profusion

What is profusion?

Gas exchange

What pressure is needed for profusion to occur?

60 mmHg

What must be happening if pressure is below 60 mmHg?

You’ll be bleeding out if you’re that low

What is the MAP for an average person?

90 mmHg

Why is too high of a MAP also a problem?

It makes it harder for blood flow to happen because resistance is too high

What is the pressure in the left ventricle during systole?

120 mmHg

What is the pressure in the left ventricle during diastole?

0 mmHg

Is pressure ever 0 outside of the heart in the body?

No

* Blood wouldn’t be flowing then which would be a problem

What causes the pressure in the left ventricle to reach 0 mmHg during ventricular diastole?

Isovolumetric relaxation

What 2 things affect flow rate?

1) The pressure gradient within the same vessels

2) Resistance

What happens to flow rate when the pressure gradient in a vessel is small?

It is slow

What is the speed of the flow rate when the pressure gradient is big?

The flow rate is fast

Where is the pressure gradient in a vessel located?

Between the arteriole and venous sides

How does resistance affect blood flow?

* Increased resistance decreases blood flow
* Decreased resistance increases blood flow

How does blood viscosity affect resistance?

* Increased blood viscosity increases resistance
* Deceased blood viscosity decreases resistance

How does vessel length affect resistance?

Increased vessel length increases resistance

Does vasoconstriction or vasodilation increase resistance?

Vasoconstriction decreases diameter which increases resistance

What way to change resistance is the most short-term and consistent?

Vasoconstriction and vasodilation to change vessel diameter

What is laminar flow?

When blood is flowing smoothly

What does vasoconstriction do to blood flow?

It turns laminar flow to turbulent flow

What has the greatest affect on pressure gradient?

Changes in vessel diameter

What is flow rate often reflective of?

Vasomotor tone

What is vasomotor tone?

The state in which your vessel is in

What is homeostasis a balancing act between in cardiovascular dynamics?

Profusion and maintaining blood pressure

Is the body constantly checking the volume and makeup of blood?

Yes

What 2 centers does the medulla oblongata house?

1) The cardiovascular center

2) The respiratory center

What controls the medulla oblongata and homeostasis?

The hypothalamus

* It always is sampling the blood

What are the 2 subcenters of the cardiovascular center?

1) The cardiac center

2) The vasomotor center

Where do motor neurons from the cardiac center go?

To the heart

What 2 types of responses can the cardiac center cause to the heart?

1) Cardioacceletory response

2) Cardioinhibitory response

Where do motor neurons from the vasomotor center go?

To vessels

What 2 responses can motor neurons from the vasomotor center cause?

1) Vasoconstriction

2) Vasodilation

What are important, specific mechanoreceptors?

Baroreceptors

What do baroreceptors sense?

Pressure

* Specifically stretch

Where are baroreceptors located?

In the aorta and carotid artery

What is the stimulus for baroreceptors?

The volume of blood

What is the effect of high blood volume on baroreceptors?

It will deform baroreceptors so they’ll send a signal to the medulla oblongata

What does the signal from high blood volume cause?

* Activates cardioinhibitory motor neurons to decrease blood flow
* Activates vasodilation motor neurons to decrease blood pressure

What do cardioinhibitory motor neurons cause?

They release acetylcholine on the heart making it harder to generate action potentials

How does low blood volume affect baroreceptors?

They don’t deform baroreceptors which acts as a stimulus so they send a signal to the medulla oblongata

What does the signal from low blood volume cause?

* Interneurons activate cardioacceletory motor neurons
* Interneurons activate vasoconstriction in the vasomotor center

What do the cardioacceletory motor neurons cause?

Increased heart rate

* They release norepinephrine

What do vasoconstriction motor neurons cause?

Vasoconstriction

* They release norepinephrine to cause smooth muscle in the tunica media to contract

Where do chemoreceptors sense chemicals (oxygen, carbon dioxide, and pH) in the blood?

In the aorta and carotid artery

What must be activated if oxygen levels are low?

The cardiovascular and respiratory centers

What has to happen in the cardiovascular system when oxygen levels are low?

* Increased heart rate with cardioacceletory motor neurons
* No vasomotor response

What has to happen in the respiratory center if oxygen levels are low?

The respiratory center must be activated to increase breathing rate

What structure is important for higher order thinking?

The hypothalamus

What activates the fight or flight response when we’re stressed?

The hypothalamus

How does the hypothalamus activate the fight or flight response?

By activated the medulla oblongata

What are the effects on the medulla oblongata when we’re stressed?

* In the cardiovascular center…
* Vasodilation to some areas such as muscles and respiratory areas
* Vasoconstriction to digestion, etc
* In the respiratory center…
* Increases in breathing rate