circulatory system

Question 1

why do humans need a transport system

Answer 1

larger organisms with tissues and organs have a smaller surface area to volume ratio
many organisms are protected by hair, scales, shells and skin are not semipermeable
diffusion is not fast or efficient enough to allow substances to move through the body and reach every cell quickly enough for them to survive
a transport system is necessary to get important and needed substances to every single cell and transport waste to toxic substances away from every cell

Question 2

list the three components of the circulatory system

Answer 2

the heart: a pumping device which propels blood around the body by contracting and relaxing
blood vessels: network of tubes which blood flows to get to and from cells
blood: circulatory fluid pumped around the body transporting necessary nutrients to where it is required and taking waste away from the cells

Question 3

define blood

Answer 3

medium by which substances around the body
tissue
consisting of red blood cells white blood cells and platelets found in a liquid medium known as plasma
plasma makes up 55% of the volume of blood while the other 45% comprises red blood cells and platelets

Question 4

how much blood does the average human has

Answer 4

5 Litres

Question 5

define blood plasma

Answer 5

plasma is made up of 90% water and 10% dissolved substances
dissolved food – amino acids, glucose, fatty acids, glycerol
waste products – urea, hydrogen carbonate ions
hormones – oestrogen, testosterone, adrenaline, insulin
dissolved gases– oxygen and nitrogen
mineral salts – sodium, potassium, chloride, calcium, hydrogen carbonate , phosphate
water soluble vitamins– b12 and c
plasma proteins – functions include transport of lipids, hormones, vitamins and minerals in circulatory system and regulation of cellular activity and functioning of immune system – fibrinogen, albumin, prothrombin, antibodies

Question 6

define blood platelets

Answer 6

platelets are cell fragments which often do not have a nucleus
formed in bone marrow of long bones by disintegration of certain cells
260 000 platelets per mm^3 blood
help the blood to clot at a wound or cut forming a temporary plug to prevent further blood loss

Question 7

define red blood cells

Answer 7

shape described to as a biconcave disc
have a large surface area compared to a small volume so that gases can diffuse in and out easily
slightly elastic allowing them to squeeze through narrow capillaries
have no nucleus and only live about 3 months
contain a red pigment called haemoglobin which is able to bind to oxygen
makes red blood cells good at transporting oxygen to cells that need it
small amounts of carbon dioxide which are made by cells during respiration are also transported
about 5 million red blood cells per mm blood

Question 8

phagocytes

Answer 8

type of white blood cell
variable shape
granular cytoplasm
nucleus with two or more lobes
move by pseudopodia
phagocytes engulf pathogens
formed in red bone marrow

Question 9

define lymphocytes

Answer 9

round in shape
large round nucleus
small amount of non-granular cytoplasm
nucleus controls production of antibodies (special proteins which work against foreign proteins made by pathogens)
antibodies can adhere to outer surface of bacteria and so make it easier for phagocytes to ingest them cause bacteria to stick together in clumps thereby preventing them from invading tissues, dissolve outer coats of pathogens causing them to dissolve or neutralise poisonous toxins produced by pathogens
formed in lymph nodes adn spleen

Question 10

define arteries

Answer 10

carry blood away from heart
carries high blood pressure
blood moves in pulses created by ventricle contractions
blood flow is rapid
caries oxygenated blood except pulmonary artery
most lie deep within body where protected
no valves present
thick elastic walls composed of 3 layers to withstand high pressure of blood

Question 11

define capillaries

Answer 11

carry blood throughout all tissue linking arteries to veins
pressure decreases along length of capillaries
smooth blood flow
moves along length of capillary
run throughout all tissue
no valves present
walls comprise of single layer of endothelial cells extremely narrow in diameter and branch repeatedly

Question 12

define veins

Answer 12

carry blood towards heart
low blood pressure
smooth blood flow
slow blood flow
carries deoxy blood except pulmonary vein
many lie close to body’s surface
possess valves to stop backflow if low pressure, slow blood flow
thin elastic walls composed of 3 layers as do not have to withstand high pressure
large lumen offers little resistance to low blood pressure

Question 13

structure of heart

Answer 13

heart pumps blood so that it can get around body
walls made up of cardiac muscle
cardiac muscle contracts and relaxes regularly and throughout life
never gets tired but may stop working if it is not supplied with oxygen and glucose that it needs to make energy in respiration
coronary artery supplies those nutrients to cardiac muscle and coronary vein removes waste products from cardiac muscle
heart is divided into right side and left side separated by septum
each side has 2 chambers atrium which receives blood and ventricle which pump blood away

Question 14

action of the heart

Answer 14

deoxy blood from the body flows into right atrium via vena cava
right atrium is relaxed (atrial diastole) as it fills with blood and the tricuspid valves are closed
right atrium contracts (atrial systole) forcing the tricuspid valves to open and push blood down into right v
right v is relaxed
(vd) as it receives blood from the right atrium
th right v then contracts (vs) pushing blood upward into pulmonary artery
tricuspid valves close and semilunar valves open
blood goes to lungs via pulmonary artery to become oxygenated
oxy blood from lungs enter left a via pulmonary vein
left a relaxes (AD) as it fills with blood and bicuspid valves close
left a then contracts (AS) forcing the bicuspid valves open and pushing blood into left v
left v is relaxed(vd) as it fills with blood
then contracts vs pushing blood up into aorta
bicuspid valve closes and semilunar valve opens
aorta carries oxygen to body to be used by cells

Question 15

define heart rate

Answer 15

number of heartbeats per minute
average rate of a person at rest is 70 beats per minute

Question 16

define pulse rate

Answer 16

number of blood pulses per minute

Question 17

define pacemaker

Answer 17

sinoatrial node or sinus node is the heart’s natural pacemaker
small mass of specialised cells in top of right atrium
produces electrical impulses which cause heart to beat
sometimes heart rate needs to be sped up while other times it needs to be slowed down
controls heart rate

Question 18

explain pacemaker

Answer 18

messages sent along accelerator nerve from medulla in brain to pacemaker causes heart to beat with more force which also increases bp increasing heart rate
messages sent along decelerator nerve from medulla in brain to pacemaker causes heart to beat with less force which decreases bp decreasing heart rate
sensors in aorta and carotid artery detect changes in carbon dioxide levels in blood and send impluses to medulla which in turn responds by sending messages along either accelerator or decelerator nerves to pacemaker in heart

Question 19

effect of exercise on heart rate

Answer 19

as level of difficulty increases heart rate increases
heart beats faster to pump more blood to muscles in shorter period of time
this provides the muscles with more oxygen which it uses for respiration to relapse energy
energy is then needed for the muscles to contract and relax
when stop exercising heart rate remains high for a whiel

Question 20

define recovery period

Answer 20

length of time it takes for your heart rate to return to normal

Question 21

effect of exercise on breathing rate

Answer 21

breathing rate is the breaths we take per minutes
during exercise breathing increases
allows more oxygen to enter lungs in shorter period of time so that more oxygen can from the alveoli in the lungs into blood of capillaries
oxygen is needed by our cells to make energy in process of respiration
muscles use this energy to work and bring about movement needed for exercise

Question 22

define clotting

Answer 22

when a tissue is wounded blood flows from it and coagulates to form a blood clot