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Flashcards in Physiology Deck (84):
1

Which part of the brain is involved in thermoregulation?

Hypothalamus

2

Outline the composition of intracellular fluid

Cytoplasm: high in K+, low in Na+ and Cl-

3

Outline the composition of extracellular fluid

Interstitial fluid and plasma; Low K+, high Cl- and Na+

4

Define 'osmolarity'

Number of osmoles of solute per litre of solution (Osm/L)

5

Define 'osmolality'

Osmoles of solute per kg of solvent (Osm/kg)

6

Define 'colloid'

Large molecular weight particles present in solution

7

What is the 'Donnan effect'?

If cell doesn't do anything to control osmolarity --> higher solutes inside --> water flow inwards --> lysis/rupture

8

Define 'tonicity'

Actual effect of solution on living cell

9

What is tonicity influenced by?

By solutes which can't cross membrane

10

Where is sodium absorbed in the kidney?

Distal convoluted tubule regulated by aldosterone

11

Where is water reabsorbed in the kidney?

Collecting duct, regulated by ADH

12

Describe 'hyponatraemia'

Decrease in extracellular osmolarity as total body water increases and there is decrease in plasma electrolytes - often caused by overhydration

13

Describe 'hypernatraemia'

Increase in extracellular osmolarity as total body water decreases so there is increase in plasma electrolytes, often due to dehydration

14

Define 'buffer system'

Substances present in body fluids and limit pH change by ability to accept or donate hydrogen ions

15

Define 'buffer'

Solution which can maintain a constant pH if solution is diluted or strong acids/bases added - consists of weak acid and it's conjugated base, or weak base and it's conjugate acid

16

Describe the phosphate buffer system (include equation)

Present in intracellular fluid (cytoplasm) only:
H+ + HPO42- H2PO4-

17

Describe the haemoglobin buffer system

Present in RBCs only:
H+ + Hb HHb

18

Describe amino acid buffers

Proteins accept or donate proton (present in ICF and ECF)

19

Describe the carbonic acid-bicarbonate buffer system (include equation)

Present in ECF:
CO2 + H2O H2CO3 H+ + HCO3-

20

Describe respiratory regulation of pH

Alter rate/depth of respiration to retain or eliminate CO2 --> changes are rapid

21

Describe renal regulation of pH

Excretion or conservation of bicarbonate/hydrogen ions --> changes are slow

22

What should serum pH be?

7.35-7.45

23

State the equation to calculate pH

pH = -log10[H+]

24

Define 'acidemia'

pH less than 7.35

25

Define 'alkalemia'

pH greater than 7.45

26

What can affect serum pH?

Bicarbonate rise/drop and CO2 rise/drop

27

What is the cause of respiratory acid-base disorders?

Abnormal respiratory function --> rise /fall in CO2 in ECF

28

What is the cause of metabolic acid-base disorders?

Generation of acids (organic or fixed) which affects concentration of bicarbonate ions in ECF

29

Explain how to interpret arterial blood gases

1. Look at the pH to see if primary problem is acidosis or alkalosis
2. Check the CO2 levels (respiratory indicator)
3. Check the HCO3- (metabolic indicator)
4. Decide which is the primary disorder (respiratory or metabolic); whichever is concurrent with the change in pH (carbon dioxide is acidic and bicarbonate is alkali)

30

Describe 'paracrine signalling'

Molecules act locally and include neural communication systems

31

How does the Na+/K+ pump contribute to establish resting membrane potential?

3 Na+ ions in for 2 K+ out --> negative inside, positive outside

32

Describe voltage-sensitive Na+ channels

Activation gate: closed at rest, opens on depolarisation (fast)
Inactivation gate: open at rest and closes in response to depolarisation (close is slow)

33

Describe voltage-sensitive K+ channels

Closed at rest, open on depolarisation (slightly more slowly than Na+ activation gate) --> stays open throughout depolarisation

34

Describe a normal action potential curve

Resting (-70mV) --> depolarisation (Na+ activation gate opens, influx) --> threshold potential --> action potential --> repolarisation (Na+ activation gate closes, K+ channel opens) --> hyperpolarisation (K+ channel overshoots) --> Na+/K+ pump re-establishes resting membrane potential

35

What is the 'absolute refractory period'?

Cannot open voltage-gated Na+ channels regardless of size of stimulus

36

What is the 'relative refractory period'?

Difficulty in producing another action potential during hyperpolarisation

37

Describe the mechanism of action of local anaesthetics

Bind to open voltage-gated sodium channels --> prevents them from responding by re-opening --> no action potentials generated

38

Why do axons with greater diameter conduct faster?

Cytoplasmic resistance decreases with increased diameter

39

Describe Aα axons

Motor neurones; thick myelin and large diameter --> fast conduction

40

Describe Aβ axons

Mechanical touch/pressure receptors so thick myelin

41

Describe Aδ axons

Pain receptor so thick myelin to allow sudden response

42

Describe C axons

Slow pain receptor, thin diameter and no myelin (for things such as itch)

43

What are the most common excitatory neurotransmitters in the nervous system?

Glutamate

44

What are the most common inhibitory neurotransmitters in the nervous system?

GABA and glycine

45

Describe how excitatory post-synaptic potentials are created

Glutamate-gated channels cause depolarisation on post-synaptic neurone

46

Describe how inhibitory post-synaptic potentials are created

GABA/Glycine-gated channels cause net influx of Cl- --> hyperpolarisation

47

What are axosecretory synapses?

Axon secretes directly into bloodstream

48

What are axoaxonic synapses?

Axon terminal secretes into another axon

49

What are axodendritic synapses?

Axon terminal ends on a dendritic spine

50

What are axoextracellular synapses?

Axon with no connection secretes into ECF

51

What are axosomatic synapses?

Axon terminal ends on soma

52

What are axosynaptic synapses?

Axon terminal ends on another axon terminal

53

What type of receptor binds Ach?

Nicotinic

54

What does an ionotropic response involve?

Opening of ligand-gated ion channels (fast response)

55

What does a metabotropic response involve?

Where a ligand activates a receptor which then activates G proteins --> effects enzymes

56

Outline 3 ionotropic receptors

Nicotinic receptors, glutamate receptors, GABAa receptors

57

Describe nicotinic receptors

Activated by binding of 2 ACh molecules causing Na+ to flow into post-synaptic cell

58

Describe G protein-coupled receptors

7 transmembrane segments and involve: G-protein receptor, G-protein, enzyme and second messengers

59

What are the 3 main types of second messenger?

Hydrophilic water-soluble, hydrophobic lipid-soluble, gases

60

Name 4 sensory skin receptors

Pucinian corpuscle, Meissner corpuscles, Merkel cells and Ruffini endings

61

What do Meissner corpuscles do?

Register light touch (rapidly adapting)

62

What do Merkel cells do?

Register pressure texture (slow adapting)

63

What do Pacinian corpuscles do?

Register vibration (rapidly adapting)

64

What do Ruffiini endings do?

Register skin stretching (slow adapting)

65

What do parasympathetic afferents detect?

Physiological information

66

What do sympathetic afferents detect?

Pathophysiological information e.g. pain

67

What are the parasympathetic cranial nerves?

Oculomotor, facial, glossopharyngeal and vagus (III, VII, IX, X)

68

Where does the sympathetic nervous system run?

Thoracolumbar (T1-L2)

69

How does the adrenal medulla act as a modified post-ganglionic cell?

From thoracic spinal cord, sympathetic preganglionic fibres project directly to adrenal medulla cells --> secrete adrenaline and noradrenaline into blood

70

What is the myenteric plexus?

In small intestine between circular and longitudinal muscle layers --> controls motility

71

What is the submucosal plexus?

In intestines: located between submucosa and circular muscle layer; controls secretion and muscle function of mucosae

72

What nervous input goes to the enteric nervous system?

Extrinsic efferent information from vagal preganglionic fibres and sympathetic post-ganglionic fibres

73

What do nicotinic receptors respond to?

ACh

74

What do muscarinic receptors respond to?

ACh and Bethanechol

75

What neurotransmitters are used in the autonomic nervous system?

ACh between pre and post-ganglionic, then noradrenaline/ACh at effector

76

How are muscarinic receptors targeted clinically?

Antagonists: anti-secretory, anti-spasmodics ad bronchodilators
Agonists: stimulate gut and bladder function

77

What neurotransmitter do adrenoreceptors respond to?

Noradrenaline

78

What do alpha 1 adrenoreceptors do?

Agonist: vasoconstriction and inhibition of GI and bladder sphincters
Antagonist: vasodilation (treat hypertension)

79

What do beta 1 adrenoreceptors do?

Agonist: increase HR and force
Antagonist: decrease HR (beta blockers)

80

What do beta 2 adrenoreceptors do?

Agonist: bronchodilation and vasodilation
Antagonist: asthma

81

What is the resting membrane potential?

-70mv

82

What is the threshold potential?

-55mV

83

What membrane potential does an action potential peak at?

+30mV

84

What do all GPCRs respond to?

Noradrenaline