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Biosciences > Heart and Transport systems, gas exchange and digestion > Flashcards

Heart and Transport systems, gas exchange and digestion Flashcards

1
Q

Transport systems

A

Move substances to & from exchange surfaces

prevents build-up of substances at exchange surface and maintains concentration gradients.

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2
Q

Mass transport

A

Bulk movement of substances via a transport system

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3
Q

Atrio-ventricular valves

A

Open to allow blood into ventricles. They close as ventricles contract, preventing back-flow of blood into the atria

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4
Q

Semilunar valves

A

Open to allow blood into the pulmonary artery & aorta as the ventricles contract. They close as the ventricles relax, preventing backflow of blood into ventricles

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5
Q

Systole

A

Contraction of any heart chamber

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6
Q

Diastole

A

Relaxation of any heart chamber

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7
Q

Cardiac cycle

A
  • Left ventricle contracts, pressure increases above that of atrium & atrioventricular valve closes.
  • Semilunar valve opens when ventricular pressure is greater than aortic. Blood flows into aorta.
  • Ventricle relaxes & semilunar valve closes as aortic pressure is greater ventricular.
  • Ventricular pressure falls below atrio pressure. Atrio-ventricular valve opens, letting blood into ventricle.
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8
Q

Sinoatrial node

A

Patch of modified muscle cells in the right atrium. Produces regular waves of depolarisation across the atria, causing contraction

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9
Q

Atrioventricular node

A

Receives impulses from SAN, and experiences delay before sending impulse itself through the Bundle of His, stimulating ventricular contraction.

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10
Q

Bundle of His

A

Made up of purkyne fibres, extends through ventricular muscle, allowing impulse from AVN to extend through ventricles.

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11
Q

Heart rate controlled by

A

Medulla in brain. Cardioaccleratory sends impulses via sympathetic NS (noradrenaline) cardioinhibitory sends via parasympathetic (acetylcholine).

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12
Q

What occurs when too much CO2 dissolves in the blood, forming carbonic acid and lowering pH?

A

Chemoreceptors in the medulla and in the aortic and carotid bodies are stimulated. Send impulses to:

  • Respiratory centre in medulla increasin ventilation rate
  • Cardiac centre in medulla, increasing heart rate by activating the cardioacceleratory centre.
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13
Q

Venous return

A
  • Exercise causes muscles contract strongly, pressing on veins, increasin rate blood returns to the heart.
  • Causes cardiac muscle to contract more strongly, pumping out an increased volume of blood.
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14
Q

Arteries

A

Thick wall, small lumen, contain more elastic fibres and smooth muscle tissue than veins.

  • No valves except for aorta & pulmonary artery;
  • transport oxygenated blood at a high pressure
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15
Q

Arterioles

A
  • Don’t have to stand very high pressure, so posses a higher proportion of smooth muscle than elastic fibres. - - Regulate blood flow to different tissues or organs by contraction/relaxation of smooth muscle in their walls.
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16
Q

Veins

A
  • Thin walls with little elastic fibres & smooth muscle.
  • Large lumen to reduce resistance to blood flow
  • Contracting muscles in legs & body press on veins, squeezing blood along.
  • Semi-lunar valves at intervals, prevent back-flow
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17
Q

Capillaries

A
  • Have short diffusion pathway for exchange due to thin walls, short distance from cells, and large number.
  • Very high total cross-sectional area of capillaries, producing a large frictional resistance, reducing rate of blood flow, giving more diffusion time.
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18
Q

Diffusion of oxygen in the lungs

A
  • Alveoli contain high conc. of O2, giving concentration gradient for diffusion of O2 through alveolus & capillary
    cells walls into blood plasma, red cells & for combining w/ haemoglobin.
  • O2 taken by blood, maintaining conc, gradient.
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19
Q

Formation of tissue fluid in capillaries/arterioles

A
  • At arteriole end of a capillary, blood pressure is high.
  • This causes filtration of plasma containing H2O, glucose, amino acids, minerals, hormones etc. through the permeable capillary wall.
  • Blood cells & plasma proteins remain in capillary.
  • This forms tissue fluid which surrounds body cells.
  • O2, glucose, minerals etc. diffuse into body cells & metabolic waste diffuse out
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20
Q

How does tissue fluid become lymph fluid?

A
  • Following formation and release of compounds, there is loss in frictional resistance causing blood pressure to reduce as blood flows through capillaries.
  • At the venous end, hydrostatic pressure is reduced and some filtered plasma is reabsorbed into the blood down a water potential gradient.
  • Large plasma proteins remaining in the blood capillaries reduce water potential, causing osmotic uptake at the venous end.
  • It’s too slow to reabsorb all filtered plasma, some of the tissue fluid becomes lymph.
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21
Q

Lymph capillaries

A

Blind-ending vessels present between the body cells.

They jooin to form lymph vessels and empty into subclavian veins, returning the tissue fluid to the blood.

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22
Q

What causes flow of lymph through vessels?

A

Pressure created by the build up of tissue fluids, and the vessels being squeezed as muscles contract. The vessels also contain valves preventing backflow.

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23
Q

Why are cartilage rings present on the trachea?

A

Prevent collapsing during pressure changes

24
Q

Gill arch

A

Rows of gill filaments which possess lamellae. Large number of gill filaments & lamellae provide a large SA

25
Q

Inspiration in fish

A

1) Mouth opens and floor of buccal cavity is lowered increasing volume.
2) This decreases pressure in buccal cavity, water enters through mouth.
3) Simultaneously, the opercular valve is shut and the opercular cavity is enlarged reducing pressure inside.
4) Water is forced into the opercular cavity and over the gills from the buccal cavity.

26
Q

Expiration in fish

A

1) Mouth is closed and floor of buccal cavity is raised reducing volume.
2) This raises pressure in the buccal cavity, forcing water into the opercular cavity, over gills & out gill slits.
3) Pressure in opercular cavity rises & water is forced out through the opercular valve

27
Q

Increased respiration in insect

A

Spiracles open, increasing rate of gas diffusion into the body. Lactic acid build up causes water to enter cells by osmosis, drawing in even more oxygen.

28
Q

Adaptations of plants for gas exchange

A
  • Numerous stomata w/ small diameter increase rate of diffusion.
  • Leaves are thin, producing short diffusion pathway for gaseous exchange
29
Q

Stomata

A

Pore in epidermis of the leaf, surrounded by two guard cells. Gases diffuse in & out of leaves through here.

30
Q

Gaseous exchange in plants

A
  • Respiration & photosynthesis maintain diffusion gradients by using & producing O2 & CO2
  • Numerous mesophyll cells lining intercellular air spaces in leaf provide large SA for gaseous exchange.
  • Gases diffuse in through stomata & rapidly through intercellular air spaces.
  • Gases dissolve in moist cell walls of mesophyll cells and across their thin cell wall & cell membrane.
31
Q

Where are chemoreceptors involved in respiration found?

A

Carotid and aortic bodies

Medulla

32
Q

Effect of exercise on rate of breathing

A
  • Chemoreceptors are stimulated by increase in pH, caused by increased CO2 from increased respiration.
  • More nerve impulses are transmitted to inspiratory centre in the medulla.
  • Which transmits more impulses to external intercostal & diaphragm muscles increasing rate of breathing
  • This remains high until blood CO2 returns to normal.
33
Q

Control of inspiration

A
  • Inspiratory centre transmits nerve impulses along motor neurones to external intercostal & diaphragm muscles;
  • Muscles contract, inspiration occurs and lungs inflate
34
Q

Control of expiration

A
  • Following inspiration, lungs inflate, stretch receptors in bronchioles are stimulated, send impulses to expiratory centre which inhibits inspiratory centre, inhibiting transmission of impulses to respiratory muscles;
  • Respiratory muscles relax, lungs expire and deflate;
  • Lungs deflate, stretch receptors arno longer stimulated and inspiratory centre no longer inhibited.
35
Q

Peristalsis

A

Contraction of circular muscle behind the bolus and the relaxation of longitudinal muscle in the oesophagus. Muscles work antagonistically to each other.

36
Q

Bolus

A

Food ball

37
Q

Components of gastric juice

A

Pepsinogen, HCl and mucus

38
Q

Main functions of HCl in the stomach

A
  • kills some of the bacteria present in the food.
  • provides optimum pH (1-2) for the enzyme Pepsin.
  • activates Pepsin.
39
Q

Mucus in stomach

A

Aids passage of food and also helps to prevent breakdown of the lining

40
Q

Churning of food in stomach

A

Food is churned by peristaltic and antiperistaltic contractions of muscle in stomach wall, into acidic chyme. At intervals, this is released into the duodenum.

41
Q

Bile

A
  • Alkaline fluid containing NaHCO3 and bile salts.
  • Produced in liver, stored in gall bladder, entering the duodenum by the bile duct.
  • It neutralises the acidic chyme and provides a slightly alkaline optimum pH for the pancreatic enzymes.
42
Q

Bile salts

A

Component of bile

Emulsifies lipids causing them to form small droplets, increasing their SA speeding up hydrolysis by pancreatic lipase.

43
Q

Pancreatic juice

A

Alkaline fluid, containing NaHCO3 and enzymes:

Amylase, lipase, trypsin and exopeptidase.

44
Q

Amylase

A

Breaks down starch into maltose

45
Q

Lipase

A

Breaks down lipids into fatty acids and glycerol

46
Q

Trypsin

A

Endopeptidase - hydrolyses specific internal peptide bonds, breaking down larger polypeptides into smaller polypeptides.

47
Q

Exopeptidases

A

Hydrolyse terminal peptide bonds at the ends of polypeptide chains releasing individual amino acids.

48
Q

Adaptiations of the ileum

A 
Large surface area
Numerous mitochondria
Numerous carrier proteins
Multiple blood capilarries
Moist lining
49
Q

Cephalic phase in stimulating release of gastric juices

A

During chewing of food in the mouth, nerve impulses are transmitted along parasympathetic nerves to the stomach lining, stimulating release of gastric juice.

50
Q

Gastric phase in stimulating release of gastric juices

A

Nerve impulses, food in the stomach & products of peptide digestion stimulate release gastrin from the stomach lining, stimulating release of gastric juices.

51
Q

Gastrin

A

Hormone released from stomach lining. Travels in blood to gastric glands stimulating release of gastric juices.

52
Q

What factors stimulate release of gastric juices?

A

Cephalic phase
Gastric phase
Presence of food and digested food products

53
Q

What 3 substances does acidic chyme stimulate the release of the duodenum?

A

Cholecystokinin

Secretin - also stimulates release of bile by hepatic cells

54
Q

Cholecystokinin

A

Hormone, stimulated by acidic chyme in the duodenum.
Travels in blood to the gall bladder & pancreas. Stimulates secretion of enzymic components of pancreatic juice, which enter the duodenum.

55
Q

Secretin

A

Hormone, stimulated by acidic chyme in the duodenum.
Travels in blood to pancreas stimulating secretion of NaHCO3. Enters duodenum w/ pancreatic enzymes.
ALso stimulates release of bile by hepatic cells.

56
Q

Starch agar plates

A

1) Starch mixed w/ molten agar before being poured into Petri dishes and left to cool and solidify.
2) Equal sized mycelial discs from different fungi species are placed on separate starch-agar plates
3) Kept at same temperature for 24 hours
4) Plates flooded w/ iodine solution for one minute and then washed off. Clear zone is measured.

Biosciences (24 decks)

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