The human heart-transport in animals

Question 1

Heart summary

Answer 1

• 4 chambers
• enclosed in ribs and sternum
• deoxygenated blood flows through right side to lungs, oxygenated through left to body
• made of cardiac muscle, contracts and relaxes in regular rhythm, does not get fatigues
• coronary arteries supply cardiac muscle with oxygenated blood it needs
• surrounded by inelastic pericardial membranes which prevent heart from over distending with blood

Question 2

inelastic pericardial membranes

Answer 2

prevent heart from over distending with blood

Question 3

function of heart (deoxygenated side)

Answer 3

• deoxygenated blood enters right atrium via vena cava (superior/inferior) at low pressure
• as blood flows in, slight pressure builds up until atrioventricular valve opens to let blood pass to right ventricle
• when both atrium and right ventricle are filled with blood, the atrium contracts and forces all blood into right ventricle
• as right ventricle starts to contract, tricuspid/ atrioventricular valve closes
• the tendinous cords make sure valves are not turned inside out by pressure
• right ventricle contracts fully and pumps deoxygenated blood through semi lunar valves into pulmonary artery, which transports it to capillary bed of the lungs

Question 4

function of heart (oxygenated side)

Answer 4

• oxygenated blood enters left atrium via pulmonary vein
• as pressure in atrium builds, the bicuspid valve opens between left atrium and ventricle= both filled with blood
• when both are full the atrium contracts, forcing all blood into left ventricle
• left ventricle then contracts and pumps blood through semilunar valves into the aorta and around the body
• as ventricle contracts the bicuspid valve closes

Question 5

septum

Answer 5

-the inner dividing wall of the heart which prevents the mixing of deoxygenated and oxygenated blood

Question 6

why do the walls on left and right differ in thickness

Answer 6

• left much thicker because has to pump blood around body.
• left has to produce sufficient force to overcome the resistance of the aorta and arterial systems whereas right only has to overcome the resistance of pulmonary circulation

Question 7

Diastole- cardiac cycle

Answer 7

• the heart relaxes, the atria and then the ventricles fill with blood.
• the vol and pressure of blood build as heart fills, but the pressure in arteries is at a minimum

Question 8

Systole- cardiac cycle

Answer 8

• the atria contract, atrial systole, closely followed by the ventricles (ventricular systole)
• pressure inside heart increases dramatically and blood is forced out of right side of the heart to the lungs and from left side to body
• vol and pressure are low at the end of systole and b.p in arteries is at a maximum

Question 9

Sino atrial node, natural pacemaker

Answer 9

• a wave of electrical excitation begins in the pacemaker area, causing atria to contract and so initiating the heartbeat
• a layer of non-conducting tissue prevents the excitation tissuepassing directly to the ventricles (purkyne )

Question 10

atrio ventricular node

Answer 10

• electrical activity from sino atrial node picked up by it

- imposes a slight delay before stimulating the bundle of his

Question 11

Bundle of His

Answer 11

• a bundle of conducting tissue made up of Purkyne fibres which penetrate through the septum between ventricles
• splits into 2 branches and conducts the wave of excitation to the apex of the heart

Question 12

Purkyne fibres

Answer 12

-at apex, spread out through walls of the ventricles. The spread of excitation triggers the contraction of the ventricles, starting at the apex

Question 13

wave of excitation

Answer 13

-basic rhythm of heart maintained by a wave of excitation

Question 14

electrocardiograms

Answer 14

-measure the spread of excitation and records whats happening on graph

Question 15

Tachycardia

Answer 15

-when heartbeat is v rapid

Question 16

Bradycardia

Answer 16

-when heart rate slows down below 60bpm, many fit ppl have it

Question 17

ectopic heartbeat

Answer 17

extra heartbeats that are out of the normal rhythm

Question 18

atrial fibrillation

Answer 18

• example of arrhythmia= abnormal rhythm of heart
• rapid electrical impulses generated in the atria
• heart does not pump blood effectively

Question 19

Most carbon dioxide is transported as hydrogencarbonate ions in the plasma.
Hydrogencarbonate ions are produced in the erythrocytes and diffuse into the plasma.
(i) Describe how the hydrogencarbonate ions are produced in the erythrocytes

Answer 19

carbon dioxide, enters / diffuses into, erythrocytes ;
2 (carbon dioxide) combines / reacts, with water ;
3 correct ref to carbonic anhydrase;
4 forms carbonic acid ;
5 (carbonic acid) dissociates to form hydrogencarbonate
ions and, hydrogen ions / protons ;

Question 20

High concentrations of carbon dioxide in the blood reduce the amount of oxygen
transported by haemoglobin.
Name this effect and explain why it occurs.
name
explanation .

Answer 20

Name
1 Bohr (effect / shift) ;
Explanation (any 2 of the following marks)
2 reduces affinity (of Hb) for oxygen ;
3 formation of haemoglobinic acid / hydrogen ions interact
with haemoglobin ;
4 prevents, fall in pH / build-up of H+, in cells
OR provides buffering effect ;
5 alter, structure / shape, of haemoglobin ;
6 more oxygen released where, needed / more
respiration / carbon dioxide concentration high ;
7 CO2 binds to haemoglobin forming
carbaminohaemoglobin ;
3 max Maximum 2 marks if effect not named correctly
ACCEPT phonetic spelling
IGNORE ref to ‘curve shifting’
ACCEPT hydrogen ions, combine / bind, with Hb
ACCEPT HHb for haemoglobinic acid
ACCEPT H+ + Hb → HHb
ACCE

Question 21

State what is meant by the term health.

Answer 21

• mental and physical wellbeing

- in a state of no diseases

Question 22

Curve A represents fetal haemoglobin.

Explain why the fetal haemoglobin curve is to the left of the adult haemoglobin curve

Answer 22

placenta has low pO2 ;
2 adult (oxy)haemoglobin will, release O2 / dissociate,
(in, low pO2 / placenta) ;
3 fetal haemoglobin has higher affinity for oxygen /
described ;
4 fetal haemoglobin, is (still) able to take up
(some) oxygen, in placenta / at low(er) pO2

Question 23

Sickle cell anaemia is an inherited disorder in which haemoglobin crystallises when the
partial pressure of oxygen (pO2) is low. The red blood cells change shape and oxygen
transport is disrupted.
Treatment with drugs, such as hydroxyurea, can stimulate adults to produce fetal
haemoglobin rather than adult haemoglobin.
Suggest why this treatment might be of benefit to adults with sickle cell anaemia.

Answer 23

(fetal) haemoglobin may not crystallise (much)
(at low pO2) ;
red blood cells do not change shape ;
(fetal) haemoglobin can pick up more oxygen at low pO2
(than sickle haemoglobin);
idea that more oxygen, transported / delivered
(around body)

Question 24

Describe and explain how substances that are dissolved in the blood plasma, such as oxygen
or glucose, enter the tissue fluid from the capillaries

Answer 24

diffusion ;
from high concentration to low concentration / down
concentration gradient;
(hydrostatic) pressure in capillary high(er than in tissue fluid) ;
capillary (walls) leaky / described ;
fluid / plasma, forced out (of capillary)
OR
fluid / plasma, moves, from higher pressure to lower
pressure / down pressure gradient ;
(as the fluid / plasma moves out) glucose / oxygen / small molecules, leave with, fluid / plasma ;

Question 25

Explain why lignin is essential in the wall of a xylem vessel.

Answer 25

provides, strength / support ;
to keep, it / the vessel / the tube, open
OR
prevent collapse of, vessel / tube ;
(because) transpiration produces, tension / negative
pressure ;
to waterproof the, cell / vessel / tube / wall ;
(so) cell, dies / content decays ;
to create a hollow, tube / vessel
OR
to create a continuous column / allow unimpeded flow ;
to limit lateral flow of water ;
ref to adhesion (between water molecules and wall)

Question 26

Explain why cartilage is essential in the trachea

Answer 26

(provides) strength / support, to keep, it / trachea / airway,
open
OR
(provides) strength / support, to prevent collapse ;
during, inspiration / inhaling / breathing in ;
volume of, chest cavity / thorax / lungs, increases ;
low(er) / negative, pressure in, trachea / thorax / lungs

Question 27

During the electrical stimulation of the heart, there is a short delay between the excitation
of the atria and excitation of the ventricles.
Explain why this delay is essential

Answer 27

(to allow time) for the atria to (fully) contract ;
to allow (time for), atria to empty / blood to move /
ventricles to fill ;
so that ventricle(s) do not contract, too early

Question 28

) The Purkyne tissue carries the excitation wave down the septum to the apex of the heart.
Explain why the excitation wave is carried to the apex.

Answer 28

so that (ventricular) contraction starts at, apex / base /
bottom ;
to push blood upwards
OR
into/ towards, (named) arteries ;
complete / efficient, emptying of ventricles

Question 29

The pressure fluctuates as the blood flows along the aorta, as shown in Fig. 3.1.
(i) Explain what causes this fluctuation.

Answer 29

systole / contraction, increases pressure ;
diastole / relaxation/ blood flowing onwards, decreases
pressure ;
(contraction of) ventricle, muscle / wall ;
left (ventricle) ;

Question 30

Explain why the wall of the left ventricle is thicker than the wall of the left atrium

Answer 30

(more muscle to create) more force ;
2 (needs to create) higher pressure ;
3 push blood against greater , resistance / friction ;
4 (left ventricle) pumps blood further /
pumps blood to all parts of body /
 supplies systemic circulation