Circulatory System -Biology 20IB

What does the circulatory system do?

-transportation
-temperature regulation
-protection/repair

What does the circulatory system transport?

-gases
-nutrients
-waste
-hormones

What is the circulatory made up of?

-systemic, pulmonary and coronary (cardiac) systems

What are the major components of the circulatory system?

-the heart
-blood vessels
-blood cells

What is the atria and where is it located?

-two small chambers at the top of the heart
-left from the lungs
-right from the body

Where does blood enter the heart?

atria

What are the ventricles and where are they located?

-bottom two large chambers
-left to body therefore thickets
-right to lung

What do the ventricles do?

-receive blood from atria
-pushes blood out of the heart

What is the septum and what does it do?

-thick muscular wall
-separates left and right side of heart

What do the vena cavae do and how many are there?

-collect oxygen-poor blood from body (into right atrium)
-there are two

What does the superior vena cava do?

bring blood from head, chest and arms

What does the inferior vena cava do?

bring blood from the bottom half of body

What does the pulmonary trunk do and what does it branch into?

-carries oxygen poor blood from right ventricle to lungs
-branches into pulmonary arteries

What do the pulmonary veins do?

-carries oxygenated blood from lungs to the heart

What does the aorta do?

-carries oxygen rich blood from left ventricle to body?

Where does the aorta branch into?

-arteries (ie. Carotid artery)

What does the coronary artery do and where does it branch from?

-branches from the aorta
-supplies the heart muscle with nutrients and oxygen

What does the coronary vein do?

-removes CO2 and waste from the heart muscle

What is the bicuspid valve?

-valve between left atria and ventricle

How is the bicuspid and tricuspid valve attached to the ventricle wall

- attached with chord tendineae

What is another name for bicuspid?

Mitral

What type of valve is the bicuspid valve?

-an A-V
-atrioventricular valve

Where is the tricuspid valve located?

-between right atrium and ventricle

How many parts does the bicuspid valve have?

2

How many parts does the tricuspid valve have?

3

What type of valve is the tricuspid valve?

-the right AV
-atrioventricular valve

Where is the pulmonary semi-lunar valve located?

-between right ventricle and pulmonary trunk/arteries

Where is aortic semilunar valve located?

-between left ventricle and aorta

What is the 1st step in the pathway of blood through the heart?

enters right atrium from vena cavae (superior and inferior vena cava)

What is step 2 in the pathway of blood though the heart?

moves to right ventricle, then through pulmonary artery to lungs (where it picks up oxygen)

What is step 3 in the pathway of blood through the heart?

enters left atrium from pulmonary veins

What is step 4 in the pathway of blood through the heart?

moves to left ventricle then through aorta to body

What do the arteries do?

carry blood away from the heart

What is the blood pressure in the arteries?

high blood pressure

Why do the arteries have thick, muscular walls?

-keep lumen of the artery small to keep BP high
-can allow dilation (vasodilation) and constriction (vasoconstriction) to direct more or less blood to tissues

Why do the arteries have elastic walls?

-expand when ventricle contracts, then snap back to help push blood along

What is the expansion/constrition of the arteries?

pusle

What do the coronary arteries do?

-supply the heart with blood (oxygen and nutrients)

What are small arteries called?

arterioles

Why do arterioles have precapillary sphincters?

to control blood flow into capillary beds

What do open sphincters allow?

they allow for blood flow and therefore exchange with tissue

What do the capillaries connect?

arterioles to venules and veins

How thick are capillaries?

one thin cell thick

What are capillaries?

very small network of vessels

What do capillaries have permeable (leaky) walls?

so gas/nutrient exchange can occur here with surrounding tissues

What are venules?

small veins that lead from capillaries to the major veins

What do veins do?

carry blood towards heart

What is blood pressure in the veins?

low or no blood pressure

Why do veins have less elastic and larger lumens than arteries?

decrease resistance

What happens in veins to help move blood along?

skeletal muscle contractions

Why do veins have valves?

to prevent back flow of blood

What are varicose veins?

-twisted and enlarged veins
-happens to veins close to the skins surface
-most commonly happens to veins in the leg

What makes the heart contract?

SA (sinoatrial) node

Where is the SA node located?

in right atrial wall

What is the SA node made of?

a collection of uniquely structured cardiac muscle cells

What is the SA node called?

-natural pace maker

What does the SA node do?

-spontaneously initiates muscle contraction with our other nerve signals

Can your heart beat outside of your body?

yes

How are cardiac cells different from skeletal cells?

they are shorted, branched and only have one nucleus

How do cardiac muscle cells contract?

-involuntary control
-mnay contract in the absence of severe stimulation for life of cell ("myogenic")

What is the shape of cardiac muscle cells?

-y-shaped
-joined end to end

What are the ends/junctions of cardiac muscle cells called?

intercalated discs

Where do intercalated discs appear?

in cardiac muscles

What is the structure of intercalated discs and what does it do?

-double membrane with gap junctions
-allows rapid movement of ions and low electrical resistance

What do gap junctions in intercalated discs allows?

-chanels allowing cytoplasm to flow between cells

What happens during wave of depolarization?

-can pass easily from one cell to another
-both atria will contract as if one large cells (the ions changing the charge in the cell causes the contraction)

Where does electrical signal spread in the heart?

both atria

What is the path of electricity through heart?

-signal (ions) passes from SA node through gap junctions to other atrial cells (atria undergo rapid contraction (systole) as a result)

What happens to electrical conduction through ventricles?

-the electricity is briefly slowed down between atria and ventricles at A-C node
-cells of AV node take longer to become excited
-this gives a chance for the atria to empty into the ventricles before they contract

What is larger the ventricles or the atria and what does that means for the movement of ions?

-the ventricles are much larger so that means ions moving cell to cell would be inefficient

What are the special conducting fibres of the heart?

-bundle of HIS
-Purkinje fibres

What does special conducting fibres allow?

-the electricity to get to the cells of the ventricles faster

What is the bundle of HIS also called?

AV bundle

What modifications do the Bundle of His and Purkinje Fibres have to allow signals to travel at higher speeds?

-fewer myofibrils (fibres)
-bigger diameter
-higher densities of voltage-gated sodium channels
-high numbers of mitochondria and glycogen stores

Where does contraction of the ventricle being?

-at the apex (bottom) to push blood up toward the arteries exiting the top of the heart

What do ECG do?

monitors electrical signals through the heart

What is the P wave on a ECG?

electricity of the contraction of atria

What is the QRS wave on a ECG?

contraction of ventricle

What is the T wave on an ECG?

repolarization (recovery) where ions retiring ions return to starting cell

When does cardiac arrest occur?

when heart tissues are deprived of oxygen (among other reasons)

What is one of the first negative consequences of cardiac arrest?

-abnormal heart rhythms such as ventricular fibrillation (very fast beats, not strong)

What does a defibrillator do?

-applies a shock to stop the abnormal rhythm
-the SA node restores normal rhythm

What do artificial pacemakers do?

-surgically fitted to patients with a malfunctioning SA node
-can either provide regular electrical impulses or discharge when a beat is missed
-most common form silvers low voltage pulse ventricle

What is the signal for heart rate controlled by?

nerves from the medulla of the brain (just like breathing)

What does the sympathetic nerve do?

-speed up your heart rate

What does parasympathetic nerve do?

slow it down

What do hormones such as epinephrine do to the heart rate?

-increase the heart rate to prepare for vigorous physical activity

What is cardiac output?

amount of blood pumped by each side of the heart in a minute (will be equal)

What does cardiac output indicate?

-the level of oxygen delivered to body

What is the formula for cardiac output?

heart rate x stroke volume

What is the average cardiac output?

4900mL/min

What is the average heart rate and stroke volume?

-70bpms
-70mL/beat

What is stroke volume?

amount of blood forced out of the left ventricle on each beat

What does larger stroke volume mean?

increased fitness

What are factors that can increase both the rate and strength of heart contraction?

ie. Epinephrine speeds up the SA node

What are heart sounds caused by?

turbulence of blood when heart valves snap shut

What is the 1st heart sound and what is caused by?

-lub
-by closing of A-V valves during ventricular systole

What is the 2nd heart sound and what is caused by?

-dup
-by closing of semilunar valves during ventricular diastole

What do valves do?

prevent the back flow of blood

What are heart murmurs?

gurgling blood caused by valve leakage