Blood pressure, heart, thermoregulation

What is the cardiovascular system

A closed system of the heart and blood vessels.

What is the function of the cardiovascular system

Transport of nutrients and other materials, via the blood, to and from various parts of the body.

what needs to happen in order for the cardiovascular system to function

The blood must be continuously circulated

What is blood

Blood is a fluid connective tissue

What 3 layers are visible in blood after centrifugation

• Plasma

• Leucocytes

• Erythrocytes

What layer of blood is not visible after centrifugation

Platelets

What total blood volume is made up by plasma

30-60% of total blood volume

What does plasma consist of

• water, dissolved organic and inorganic nutrients

• dissolved O₂, waste products of metabolism

• Hormones

• Proteins (important for blood clotting)

• pH buffers

What is the function of leucocytes

Defend body against infection and disease

Function of erythrocytes

They are red blood cells, transport oxygen and carbon dioxide.

What is Haematocrit

Volume of blood that is composed of red blood cells (40-65%)

How many haemoglobin molecules are found in the blood

~250 million haemoglobin molecules

How many subunits do haemoglobin consist of

4

What does each subunit of haemoglobin contain

Each protein subunit contains one heme molecule that binds one O₂ molecule

How many O₂ molecules can each haemoglobin bind

4

Function of capillaries

Capillaries are the site of gas and nutrient exchange

Role of platelets

Play a crucial role in the formation of blood clots

label the heart

• superior vena cava

• systematic arteries

• aorta

• pulmonary trunk

• left pulmonary artery

• left pulmonary veins (from left lung)

• left atrium

• left ventricle

• fat deposits

• inferior vena cava

• right ventricle

• right atrium

• right pulmonary veins (from right lung)

• right pulmonary artery

Label the interior of heart

• left atrium

• left AV valve

• left ventricle

• septum

• semilunar valve

• right ventricle ]right AV valve

• right atrium

What is the size of a single cardiac muscle cell

20µm

Function of electrocardiogram

record the electrical activity of the heart

Name the 2 types of circulations

• Pulmonary circuit

• systemic circuit

Describe the distribution of blood at rest

Some organs (kidney, liver, gastrointestinal tract) receive blood in excess of their metabolic needs

What organ can least tolerate disrupted blood supply

The brain

What causes irreparable damage to the brain

Irreparable damage to brain if blood supply is disrupted >4 mins

Formula for blood pressure

What is a pressure gradient

Pressure gradient is the difference in pressure between the beginning and end of vessel

In what direction does blood flow

Blood flows from area of high pressure to an area of low pressure

What is the main driving force for blood flow through a vessel?

When heart contracts, it exerts pressure on the blood, which is main driving force for flow through a vessel.

What occurs as result of resistance in the vessel

The pressure drops as blood flows

What is resistance

Measure of hindrance or opposition to blood flow through a vessel, caused by friction between the blood in the vessel wall.

What happens if resistance to flow increases

If resistance to flow increases, it is difficult for blood to pass through a vessel, therefore, flow rate decreases

What are the main determinants of resistance

• viscosity of blood

• length of blood vessel

• radius of the blood vessel

What does a slight change in radius of the vessel do to the blood flow?

Produces significant change in blood flow

What does the vascular tree consist of

• arteries

• arterioles

• capillaries

• venules

• veins

Function of arteries

Carry blood away from heart to tissues. Serve as rapid-transit passageways for blood from heart to organs.

What are arterioles

Smaller branches of arteries

What are capillaries

Smaller branches of arterioles

Smallest of vessels across which all exchanges are made with surrounding cells

What are venules

Formed when capillaries rejoin

Return blood to heart

Features of large vein

• few layers of smooth muscle and connective tissue

• few elastin layers

• wide lumen

• endothelium

features of venule

• connective tissue

• endothelium

Differences between fenestrated and continuous capillary

Both have endothelial cells, only fenestrated capillaries have pores

Features of large artery

• many layers of smooth muscle and connective tissue

• several elastin layers

• lumen

• endothelium

features of arteriole

• smooth muscle fibres

• lumen

• endothelium

What effect does the structure of arteries have on their resistance to blood flow and pressure

Due to their large radius, arteries offer little resistance to blood flow.

Act as pressure reservoir to provide driving force for blood when heart is relaxing

What do arterial connective tissues contain

• collagen fibres (provide tensile strength)

• elastin fibres ( provide elasticity to arterial walls)

Name the two invasive measurement of blood pressure

1. systolic pressure

2. diastolic pressure

What is systolic pressure

Peak pressure when blood is ejected

What is diastolic pressure

Minimum pressure when blood is draining off into vessels downstream.

What is a normal measurement of blood pressure

120/70 mmHg (systolic / diastolic )

What is a high measurement of blood pressure

>140/>90mmHg

What percentage of the UK population have a high blood pressure

~40% of the UK population

What are factors affecting blood pressure

• peripheral vascular resistance - diameter of blood vessels ( an inc in pressure gradient and resistance)

• cardiac output

• blood volume

• vessel elasticity

Function of arterioles

Controllers of blood pressure and tissue blood flow. Major resistance vessels.

What do arterioles convert

Convert the pulsatile systolic to diastolic pressure swings in the arteries into the non-fluctuating pressure present in the capillaries.

Why can the radius of the arteriole be adjusted

Radius of the arteriole can be adjusted to:

• distribute cardiac output among systemic organs, depending on body momentary needs

• help regulate arterial blood pressure

What is arteriole vasoconstriction caused by

• ↑ myogenic activity

• ↑ oxygen

• ↓ carbon dioxide and other metabolites

• ↑ endothelin

• ↑ sympathetic stimulation Vasopressin, angiotensin II

• Cold

What is arteriole vasodilation caused by

• ↓ myogenic activity

• ↓ oxygen

• ↑ carbon dioxide and other metabolites

• ↑ Nitric oxide

• ↓sympathetic stimulation Vasopressin, angiotensin II

• Heat

What is the internal core temperature

37℃

• subject to precise regulation

What makes up our internal core temperature?

• Abdominal and thoracic organs, central nervous system, skeletal muscles.

Why is it important to maintain an internal core temperature?

Tissues function best at relatively constant temperature.

What makes up our outer shell

Consists of skin and subcutaneous fat

What temperature is the skin

Skin temperature varies between 20℃ and 40℃ without damage

What effect does an increase in core temperature have on reactions

• speeds up cellular chemical reactions

Is overheating or cooling more serious, why

overheating more serious than cooling, can cause:

• nerve malfunction, irreversible protein denaturation

• internal body temperature 41℃ causes convulsions, 43℃ upper limit compatible with life

What effect does a decrease in core temperature have on reactions

Slows down cellular reactions

What does a prolonged fall in body temperature cause

Pronounced, prolonged fall in body temperature slows metabolism to fatal level.

How does the skin regulate heat exchange on a cold day?

• warm blood enters arteries

• vessels dilate to allow blood to bypass the colder surface vessels

• vessels constrict to reduce heat loss

• blood leaves veins retaining most of its heat

How does the skin regulate heat exchange on a hot day?

• warm blood enters from arteries

• vessels constrict to shunt the blood to skin surface

• heat is lost due to dilated vessels

• blood leaves veins having lost some of its heat

Name the mechanisms of heat transfer

• radiation

• conduction

• convection

• evaporation

What is the role of the hypothalamus in regulation of temperature

Hypothalamus acts as thermostat that speeds u heat loss or heat production as needed

How is the hypothalamus activated for temperature regulation

Activated in 2 ways:

1. Thermal receptors in skin provide input to central command

2. Direct stimulation of hypothalamus through changes in blood temperature perfusing this area