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Blood Flow

Terms in this set (13)

Factors affecting blood flow (5)

* Blood flow is higher in _______ & ________ animals.
Fat has a poor blood supply. Also higher in carnivores than ____________ - ___________ have a very large ___ with a large blood supply.
1. Blood volume

2. Blood pressure

3. Blood viscosity

4. Blood vessel length, diameter, geometry

5. Vessel compliance - ability for blood vessel to expand without recoiling back to their original size.
- High compliance - easily expands, doesn't recoil (veins, thin layer of smooth muscle, small pressure causes expansion).
- Low compliance - recoils back after expansion (arteries, need high pressure to expand even by a small amount).


* Blood flow is higher in SMALLER & LEANER animals.
Fat has a poor blood supply.
Also higher in carnivores than HERBIVORES - HERBIVORES have a very large GUT with a large blood supply.
Blood Volume:

Blood Volume determined by the amount of INGESTED ____ & _____
- NOT what is _________ by _________ into urine, lost through the ___ , lungs or skin.

Kidneys
- ______ and ___ regulation
- maintain water content of body and ________ of plasma
Blood Volume determined by the amount of INGESTED H20 & Na+.

- NOT what is EXCRETED by KIDNEYS into urine, lost through the GIT, lungs or skin.

Kidneys
- WATER and ION regulation
- maintain water content of body and TONICITY of plasma (the ability of a solution surrounding a cell to cause that cell to gain or lose water).
Hypervolemia:

______________ blood volume
INCREASED blood volume
Hypovolemia

____________ blood volume
DECREASED blood volume
Blood Pressure:

We need to be able to change flow when exercising
- _________ _______ needs greater blood supply
- more needs to get into lungs

Resistance of vessels means flow can be controlled.
We need to be able to change flow when exercising
- SKELETAL MUSCLE needs greater blood supply
- more needs to get into lungs

Resistance of vessels means flow can be controlled
Blood Pressure:

Pressure Difference (P) = Flow (Q) x Resistance (R)

Flow (Q) = supply of _____ to different tissues

Pressure = generated by _____

Resistance = blood vessel ________, _______ & blood ________.
Flow (Q) = supply of BLOOD to different tissues

Pressure = generated by HEART

Resistance = blood vessel DIAMETER, LENGTH & blood VISCOSITY.
Key roles of blood (2)
homeostasis & transport
Blood Viscosity
- how does it affect blood flow?

_______ ____ ________ (PCV) or haematocrit (between 30-55% depending on the species). Determined by number of ____________.
Haematocrit = the measurement of the proportion of ______ which is made up of ____. Low haematocrit = ________

Plasma viscosity is 1 1/2 that of water due to ______ ________.
Viscosity of normal blood = 3.5

increased viscosity = increased resistance
> decreased flow rate
Blood Viscosity
- how does it affect blood flow?

PACKED CELL VOLUME (PCV) or haematocrit (between 30-55% depending on the species). Determined by number of ERYTHROCYTES.
Haematocrit = the measurement of the proportion of BLOOD which is made up of CELLS. Low haematocrit = ANAEMIA.

Plasma viscosity is 1 1/2 that of water due to PLASMA PROTEINS.
Viscosity of normal blood = 3.5

increased viscosity = increased resistance
> decreased flow rate
Blood Viscosity: Polycythaemia

Increased blood VISCOSITY resulting in high _____ ________.
- higher viscosity require a greater change in _________ or reduced ________ to maintain the same rate of blood flow.

Q = P/R

This leads to the need for increased cardiac _______.

- causes increased cardiac _______ which can lead to _____ ________ if prolonged.
Polycythaemia

Increased blood VISCOSITY resulting in high BLOOD PRESSURE.
- higher viscosity require a greater change in PRESSURE or reduced RESISTANCE to maintain the same rate of blood flow.

Q = P/R

This leads to the need for increased cardiac OUTPUT.

- causes increased cardiac OUTPUT which can lead to HEART FAILURE if prolonged.
Blood Viscosity - how is it regulated?

Blood viscosity is regulated by erythrocyte cell surface _____ created by erythrocyte cell surface _______. Glycoproteins provide a charge to prevent __________ sticking together.

Rouleaux
- aggregates form due to the _____ shape of the RBCs which occurs due to increased _______ proteins.

Infection
- ___________ increases during inflammation, binds to COOH groups, preventing the negative repulsion between RBCs.

Polycythaemia
- increases Rouleaux RBCs as the number of ___________ increase due to the increased viscosity.
Blood Viscosity - how is it regulated?

Blood viscosity is regulated by erythrocyte cell surface CHARGE created by erythrocyte cell surface PROTEINS. Glycoproteins provide a charge to prevent ERYTHROCYTES sticking together.

Rouleaux
- aggregates form due to the DISC shape of the RBCs which occurs due to increased PLASMA proteins.

Infection
- FIBRINOGEN increases during inflammation, binds to COOH- groups, preventing the negative repulsion between RBCs.

Polycythaemia
- increases Rouleaux RBCs as the number of INTERACTIONS increase due to the increased viscosity.
Vessel Length , Diameter & Geometry
- how do these affect blood flow?

Change in blood vessel _________ is the main factor in determining blood flow to different organs.

Reducing diameter > increased resistance.

Vessel Geometry:
Laminar flow = _____ resistance
Turbulent flow = _____ resistance
* most vessels have branches & bumps that limit _______ flow.
Turbulence leads to ________ velocity and _________ resistance and therefore _________ blood flow rate.
Vessel Length , Diameter & Geometry
- how do these affect blood flow?

Change in blood vessel DIAMETER is the main factor in determining blood flow to different organs.

Reducing diameter > increased resistance.

Vessel Geometry:
Laminar flow = LESS resistance
Turbulent flow = MORE resistance
* most vessels have branches & bumps that limit LAMINAR flow.
Turbulence leads to INCREASED velocity and INCREASED resistance and therefore REDUCED blood flow rate.
Vessel compliance
how does this affect blood flow?

Compliance refers to the vessels ability to change _____ when there is a change in pressure.

Elastic fibres in the wall allows stretching.
_________ diameter > ___________ resistance > ______________ blood flow
If a vessel is COMPRESSED, elastic or not, the diameter will ________
which _________ resistance > ________ blood flow.
Vessel compliance
how does this affect blood flow?

Compliance refers to the vessels ability to change SHAPE when there is a change in pressure.

Elastic fibres in the wall allows stretching.
INCREASED diameter > REDUCED resistance > INCREASED blood flow.

If a vessel is COMPRESSED, elastic or not, the diameter will DECREASE which INCREASES resistance > REDUCES blood flow.
Velocity

The _____ of blood flowing through a vessel.

wider vessel = ___ velocity, smooth flow
narrow vessel = ____ velocity, not smooth flow

Velocity is inversely proportional to the total cross sectional area of all tubes in parallel.

This cross sectional surface area is highest in __________ beds (due to the increased vessel number, despite reduced diameter)
= reduces velocity, slower smooth flow.
Velocity

The SPEED of blood flowing through a vessel.

wider vessel = SLOWER velocity, smooth flow
narrow vessel = FASTER velocity, not smooth flow

Velocity is inversely proportional to the total cross sectional area of all tubes in parallel.

This cross sectional surface area is highest in CAPILLARY beds (due to the increased vessel number, despite reduced diameter) = reduces velocity, slower smooth flow.
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