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🧬 > 3.1.2 - Transport In Animals > Flashcards

3.1.2 - Transport In Animals Flashcards

1
Q

Why does a multicellular organism need a transport system whereas the unicellular organism does not?

A
  • The multicellular organism has a smaller SA:V ratio
  • The multicellular organism has a higher metabolic rate than the unicellular organism
  • Oxygen takes longer to diffuse into the multicellular organism
  • The multicellular organism has a longer diffusion distance than the unicellular organism
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2
Q

The cardiac cycle

A
  • Sequence of contraction and relaxation of the heart chambers during one heartbeat
  • Both sides of the heart contract at the same time
  • Blood passes through the heart and around the body due to differences in pressure
  • Differences in pressure are created by the contacting & relaxing of the heart muscle
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3
Q

Systole

A

When the heart muscle is contracted

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4
Q

Diastole

A

When the heart muscle is relaxed

  • Pressure is higher in the veins than the atria, (achieved by atrial muscles relaxing) The atria increases in volume = Pressure falls
  • Blood enters the atria, increasing pressure = Higher pressure in atria than ventricles
  • Blood moves atria -> ventricles by pushing open the atrioventricular valves
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5
Q

Atrial systole

A
  • Atria contract causing a further decrease in volume = increases pressure
  • Any blood remaining is forced from the atria to the ventricles
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6
Q

Ventricular systole

A
  • Ventricular volume decreases as blood fills them = increase pressure = further increase when ventricular walls contract
  • Atrioventricular valves are forced to shut
  • Semilunar valves are forced open as blood enters arteries = continues until arterial pressure < ventricular pressure
  • Blood then falls back = Semilunar valves shut
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7
Q

Circulatory system: Mammals

A

Closed, double circulatory system

  • Blood passes through the heart twice
  • When blood passes through the lungs = lower pressure (HP would damage alveoli) = Return to heart increases pressure
  • Blood stays in vessels
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8
Q

Circulatory system: Fish

A

Closed, single circulatory system

  • Blood passe through the heart once
  • Blood travels at low pressure = high prepare would damage the gills
  • Limits organism size
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9
Q

Circulatory system: Insects

A

Open system

-No vessels
- Fluid (haemolymph) circulates through the body cavity (haemocoel)
- Muscles circulate the haemolymph during movement

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10
Q

Exam question

‘State the meanings of the terms single circulatory system and closed circulatory system’

A

Single circulatory system: Blood passes through the heart once each circuit of the body

Closed circulatory system: The blood is maintained inside vessels

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11
Q

Blood vessels

A

Artery: Blood away from heart -> Arterioles
Arterioles: Arteries -> capillaries
Capillaries: Arterioles -> veins (allow exchange of CO2 & O2 between tissues and blood)
Veins: capillaries -> heart

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12
Q

Blood vessels: General structure

A

Tunica externa = The outermost layer made of collagen

Tunica media = The middle layer made of smooth muscle & elastic tissue

Tunica intima = Layer of squamous epithelial cells, called endothelium (lines the lumen)

lumen = Space blood passes through

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13
Q

Structure of an artery

A

Tunica externa = Thin (Collagen prevent bursting under high pressure)
Tunica media = Thick (Layer of elastic tissue allows pressure maintenance & moth flow due to elastic recoil)
lumen = Narrow (Increases pressure & smooth to prevent friction)

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14
Q

Arteriole: Structure related to function

A

The muscle layer is relatively thick compared to arteries - the muscle can contract (vasoconstriction) and narrow the lumen, controlling blood flow into capillaries.

The elastic layer is thin compared to an artery = lower pressure

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15
Q

Structure of capillary

A

1 cell thick (squamous epithelial cells) = short diffusion distance

  • Smooth to prevent friction

Fenestrations = allows passage of substances

Low pressure = high volume (& tissue fluid leaving)

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16
Q

Structure of a vein

A
  • Large lumen = reduced friction & increased spreed of blood flow
  • Tunica intima: smooth endothelium reduces friction
  • Tunica media: Thin layer of elastic tissue (Blood is at lower pressure)
  • Tunica externa: Collagen layer to provide strength
  • Valves to prevent back flow of blood (skeletal muscles contracting pushes blood towards the heart)
17
Q

Tissue fluid

A

= fluid by which substances are exchanged between the blood and cells. Supplies tissues with essential solutes in exchange for waste products between blood and cells at the site of capillaries’ endothelial cells.

  • Made up of substances which are small enough to escape through fenestrations in the capillaries wall. This includes nutrients such as: oxygen, glucose, water, amino acids, fatty acids and ions.
18
Q

Hydrostatic pressure

A

residual pressure from the heart beating created when blood is forced through the capillaries.

19
Q

Oncotic pressure

A

movement of fluid out of the capillaries (due to hydrostatic pressure), the water potential of the capillaries becomes more negative (though this is usually stable).

20
Q

Tissue Fluid Formation

A
  1. High hydrostatic pressure exists at the arterial end. The hydrostatic pressure inside the capillary is higher than the hydrostatic pressure in the tissue fluid.
  2. Pressure difference forces water and other small molecules out of the capillary, forming tissue fluid. Proteins and cells stay inside the capillary (too large).
  3. The hydrostatic pressure in the capillary reduces = volume decreases
  4. Water potential at the venule end is lower than that of the tissue fluid. (Due to the loss of fluid from the capillary & an increasing concentration of proteins and cells that don’t leave the capillary.)
  5. Some of the tissue fluid re-enters the capillary from the venule end via osmosis. The tissue fluid loses most of its oxygen and other nutrients to the cells but has gained carbon dioxide and waste materials.
  6. Excess tissue fluid is drained into the lymphatic system and then back into the circulatory system.
21
Q

Flow of blood through the heart

A

Vena cava (superior & inferior) -> R. Atrium -> Tricuspid valve -> R. Ventricle -> Semi lunar valve -> Pulmonary artery ->

Lungs

-> Pulmonary vein -> L. Atrium -> Bicuspid valve -> L. Ventricle -> Semilunar valve -> Aorta

22
Q

Safety during dissection

A
  • Goggles
  • Disinfect before & after
  • Take care with scalpel
  • Dispose of all waste in designated bin bag
23
Q

How the heart contracts

A
  1. Cells in the SAN send nerve impulses through atria -> atria simultaneously contract (atrial systole)

Blood pressure = Higher in atria than ventricles
- Valves open & blood flows into ventricles

  1. Nerve impulse spread from atria to ventricles through AVN -> VN introduces a delay so ventricles can fill & contract after atria
  2. Ventricle contract from the apex upwards = force blood into surrounding blood vessels = Ventricular systole

Blood pressure = Higher in ventricles than atria
- Semilunar valves open & blood flows into ventricles
- Valves to atria close

24
Q

Exam question:

‘Describe how the action of the heart is initiated and coordinated’ (5)

A
  • SAN initiates excitation (acts as pacemaker)
  • Wave of excitation spreads over atrial muscle towards AVN
  • The atria contract simultaneously (atrial systole)
  • There is a delay at the AVN
  • Excitation spreads down the septum towards the bundle of His
  • Ventricles contract from apex upwards (ventricular systole)
25
Q

ECG - Wave meanings

A

P Wave: Atrial systole
QRS Complex: Ventricular systole
T Wave: Diastole

26
Q

Tachycardia

A

Fast heartbeat

27
Q

Brachycardia

A

Slow heartbeat

28
Q

(Atrial/Ventricular) Fibrillation

A

Irregular heartbeat

Ventricular fibrillation = A lot of QRS
Atrial fibrillation = Indistinct P wave

29
Q

Oxygen Transport

A
  • O2 is transported in erythrocytes
  • O2 is transported in the blood bound to the haem group in haemoglobin

Hb + 4O2 <-> HbO8
Haemoglobin + oxygen <-> oxyhaemoglobin

  • The partial pressure of O2 is a measure of oxygen concentration (Higher partial pressure = higher concentration)
30
Q

% of CO2 transported

A

5% dissolved in plasma
10% forms carbaminohaemoglobin
85% transported as hydrogencarbonate ions

31
Q

Formation of hydrogencarbonate ions

A
  1. CO2 diffuses into erythrocytes
  2. Carbonic anhydrase (enzyme) combines CO2 & H2O
  3. Carbonic acid then dissociates & HCO3- moves out of the erythrocyte
  4. Cl- shifts in to maintain charge in erythrocyte & Haemoglobonic acid forms (Chloride shift)

The H+ is taken up by haemoglobin, acting as a buffer to maintain pH

32
Q

Why is there a shift in the curve of a Bohr curve at high concentrations of CO2

A

The shape of Hb is altered; Hbs affinity for O2 is reduced; there is more dissociation of oxyhaemoglobin therefore more O2 available for respiring tissues; Hb acts a a buffer; by binding to the H+ forming haemoglobonic acid; Hb binds to CO2 to form carbaminohaemoglobin

33
Q

Fetal haemoglobin

A

Bohr curve shifts left

Higher affinity for O2 than adult haemoglobin; Fetal Hb takes up O2 at a lower partial pressure of O2; the placenta has a lower partial pressure of O2; at a low partial pressure the adult oxyhaemoglobin will dissociate

34
Q

Exam question:

‘Explain why the curve for fetal oxyhaemoglobin is to the left of the curve for adult haemoglobin’ (4)

A
  • Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin
  • Fetal Hb takes up oxygen at a lower partial pressure of oxygen than adult Hb
  • The placenta has a low partial pressure of oxygen
  • At a low partial pressure of oxygen (eg the placenta), adult oxyhaemoglobin will dissociate
35
Q

Exam Question:

‘Most carbon dioxide is transported as hydrogencarbonate ions in the plasma

Describe how the hydrogen carbonate ions are produced in the erythrocytes’ (4)

A
  • CO2 diffuses into erythrocytes
  • CO2 reacts with water, the reaction is catalysed by the enzyme carbonic anhydrase
  • Carbonic acid is formed
  • Carbonic acid dissociates to form hydrogencarbonate ions and hydrogen ions
36
Q

Exam question:
‘High concentrations of carbon dioxide in the blood reduce the amount of oxygen transported by haemoglobin

Name this effect and why it occurs’ (3)

A

Name: Bohr effect

Explanation:

  1. Reduces affinity of Hb for oxygen
  2. Formation of haemoglobonic acid/ H+ interacts with haemoglobin
  3. Provides a buffering effect, preventing fall in pH
  4. Alters the structure of haemoglobin
  5. More oxygen released where needed (due to increased respiration)
  6. CO2 binds to haemoglobin forming carbaminohaemoglobin

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