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Foundations of Medicine JMO > Action potentials and membranes > Flashcards

Action potentials and membranes Flashcards

1
Q

What is influx?

A

The movement of ions into the cell

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2
Q

What is efflux?

A

The movement of ions out of the cell

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3
Q

What drives the passive movement of ions across the cell membrane?

A

The electrochemical gradient, which combines concentration and electrical gradients

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4
Q

Which side of the cell membrane contains a higher concentration of Na+?

A

The outside of the cell

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5
Q

which side of the cell membrane contains a higher concentration of K+?

A

The inside of the cell

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6
Q

What are some examples of common membrane lipids?

A

Phosphatidylserine
Phosphatidylinositol
Phosphatidylcholine
Sphingomyelin
Galactocerebroside

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7
Q

What are the 2 broad classes of membrane proteins?

A

Peripheral proteins
Integral proteins

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8
Q

What are peripherally associated membrane proteins?

A

Proteins that are not embedded in the cell membrane but are usually associated with the cytoplasmic or extracellular surfaces of the membrane

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9
Q

What is the role of membrane bound carbonic anhydrase?

A

It plays a role in the reabsorption of bicarbonate in the kidneys

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10
Q

What is the collective name for the layer of glycoproteins and glycolipids on the cells surface?

A

The glycocalyx

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11
Q

What is cystinuria?

A

A genetic disorders which prevents the reabsorption of cysteine (Amino acid) into the blood, so it crystallises and build up in the kidneys

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12
Q

What is meant by an isotonic solution?

A

A solution that has an equal water potential to the cells in it

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13
Q

What is meant by a hypotonic solution?

A

A solution that has a greater water potential to the cells in it - movement of water into the cells

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14
Q

What is meant by a hypertonic solution?

A

A solution that has a lower water potential to the cells in it - movement of water out of the cells

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15
Q

What is the modified Fick’s equation for calculating the net rate of diffusion?

A

Q = ∆C x A x P
Q = Net rate of diffusion
∆C = Concentration gradient
A = Surface area of membrane
P = Membrane permeability

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16
Q

What is the Goldman-Hodgkin-Katz equation for calculating membrane potential?

A

. ( Pk [K]out x Pna [Na]out)
.Em = 61 x Log10 (————————————)
. (Pk [K]in x Pna [Na]in )

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17
Q

How is permeability linked to equilibrium potential?

A

The greater the permeability for a given ion, the greater the tendency for that ion to drive the membrane potential towards the ion’s own equilibrium potential

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18
Q

What is the simplified Nernst equation for calculating the equilibrium potential of a monovalent ion at 37ºC?

A

. [ion]outside
Ion = 61 x Log10 (——————–)
[ion]inside

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19
Q

What is the relative membrane permeability for Na+?

A

1

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20
Q

What is the relative membrane permeability for K+ for a skeletal muscle cell?

A

100

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21
Q

How is an electrical gradient set up in a cell?

A

Excess charges on one side of the cell are attracted to the membrane edge

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22
Q

What are the 2 types of refractory period?

A

Absolute refractory period - no stimulus can cause AP
Relative refractory period - Greater than usual stimulus can cause AP

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23
Q

What is the name of the start of the axon?

A

The axon hillock

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24
Q

What are the two types of conduction?

A

Contiguous conduction
Saltatory conduction

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25
Q

What is the name given to the spaces between the schwann cells or oligodendrocytes?

A

Nodes of Ranvier

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26
Q

What are some examples of demyelinating disorders?

A

Multiple sclerosis (CNS)
Guillian-Barré syndrome (PNS)

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27
Q

What are the 3 divisions of the peripheral nervous system?

A

Somatic efferent
Somatic afferent
Autonomic

28
Q

What are the 3 divisions of the autonomic nervous system?

A

Sympathetic
Parasympathetic
Enteric

29
Q

What are the 3 main sections of the motor autonomic nervous system?

A

Preganglionic neurone
Autonomic ganglion
Postganglionic neurone

30
Q

What type of neurotransmitters are found in the preganglionic neurone of the autonomic nervous system?

A

Acetylcholine

31
Q

What types of neurotransmitters can be found in the postganglionic neurone of the parasympathetic division?

A

Acetylcholine - rapid
Nitric oxide - Intermediate
Vasoactive Intestinal Peptide (VIP) - slow

32
Q

What types of neurotransmitters are found in the postganglionic neurone of the sympathetic division?

A

Adenosine TriPhosphate (ATP) - rapid
Noradrenaline - intermediate
Neuropeptide Y - slow

33
Q

What effect does parasympathetic stimulation have on heart rate and contraction force?

A

Decreased heart rate and force by stimulation of M2 muscarinic acetylcholine receptors

34
Q

What effect does parasympathetic stimulation have on the bronchi

A

Bronchi contraction and mucus production by stimulation of M3 muscarinic acetylcholine receptors

35
Q

What effects does parasympathetic stimulation have on the intestine?

A

Increased intestinal motility (Movement) and secretions by stimulation of the M3 muscarinic acetylcholine receptors

36
Q

What effects does parasympathetic stimulation have on the sphincters of the GI tract?

A

Relaxation of sphincters by stimulation of the Nitric oxide and M3 muscarinic acetylcholine receptors

37
Q

What effects does parasympathetic stimulation have on vasculature?

A

Mostly no effect

38
Q

What effects does parasympathetic stimulation have on the bladder?

A

Constriction of the bladder wall by stimulation of M3 muscarinic acetylcholine receptors

39
Q

Which receptors are stimulated by the parasympathetic division, leading to penile erection?

A

Nitric oxide and M3 muscarinic acetylcholine receptors

40
Q

What effect does sympathetic stimulation have on heart rate and force of cardiac contraction?

A

Increased heart rate and force of contraction caused by stimulation of ß1 adrenoceptors

41
Q

What effect does sympathetic stimulation have on bronchi?

A

Relaxation of bronchi and reduced mucus production due to stimulation of ß2 adrenoceptors

42
Q

What effect does sympathetic stimulation have on intestinal motility and sphincters of the GI tract?

A

Reduced intestinal motility and constrction of sphincters by stimulation of α1, α2 and ß2 adrenoceptors

43
Q

What effect does sympathetic stimulation have on vasculature?

A

Constriction in most locations due to α1 adrenoceptor stimulation
Relaxation of skeletal muscle due to ß2 adrenoceptor stimulation

44
Q

What effect does sympathetic stimulation have on the adrenal glands?

A

Release of adrenaline from adrenal medulla by stimulation of nicotinic acetylcholine receptors

45
Q

What is the detrusor muscle?

A

A muscle found in the bladder wall that contracts during urination

46
Q

What effect does sympathetic stimulation have on the bladder?

A

Relaxation of the detrusor muscle of the bladder due to ß1 and ß2 adrenoceptor stimulation, and constriction of the internal urethral sphincter due to α1 stimulation

47
Q

Which receptors are stimulated by the sympathetic division, leading to ejaculation?

A

α1 receptors

48
Q

Which enzyme breaks down acetylcholine?

A

Acetylcholinesterase

49
Q

What occurs during synaptic transmission at a cholinergic synapse?

A

Precursor molecules are chemically altered to form the neurotransmitter
These are enveloped in vesicles
Ca2+ influx caused by action potential, moves vesicle to membrane along microtubules
Exocytosis of neurotransmitters
Binding of neurotransmitters to Nicotinic or muscarinic acetylcholine receptors causing effect

50
Q

What type of molecule is A234 (Novichok Nerve agent)?

A

Acetylcholinesterase inhibitor

51
Q

What occurs in myasthenia gravis?

A

Antibodies target the acetylcholine receptors, causing a reduced muscle tone and so muscle weakness

52
Q

What are the 2 precursor molecules of acetylcholine?

A

Acetyl-Coenzyme A
Choline

53
Q

What enzyme converts acetyl-coenzyme A and choline into acetylcholine?

A

Choline Acetyltransferase

54
Q

What type of receptor are nicotinic acetylcholine receptors?

A

Ligand-Gated Ion Channels

55
Q

What type of receptor are muscarinic acetylcholine receptors?

A

G-Protein Coupled Receptors

56
Q

How many glycoprotein subunits form a cation conducting channel?

A

5

57
Q

What are the different types of glycoprotein subunits, forming the cation conducting channels?

A

α1-10
ß1-4
γ
𝛿
ε

58
Q

How does varenicline act upon α4ß7 receptors in the CNS?

A

It acts as a partial agonist on α4ß7 receptors in the forebrain

59
Q

How does varenicline act upon α7 receptors in the CNS?

A

It acts as a full agonist on α7 receptors in the forebrain

60
Q

What is the medical name given to pupil contraction?

A

Mydriasis

61
Q

What is the medical name given to focussing of the eye for far vision?

A

Cycloplegia

62
Q

What is the medical name given to dry mouth?

A

Xerostomia

63
Q

What is the medical name given to the absence of sweating?

A

Anhidrosis

64
Q

What are some of the effects caused by stimulation of the M1 muscarinic acetylcholine receptor?

A

Gq causes stimulation of phospholipase C increases stomach acid secretion

65
Q

What are some of the effects caused by stimulation of the M2 muscarinic acetylcholine receptor?

A

Gi causes inhibition of adenylyl cyclase, causing opening of K+ channels and decreasing heart rate

66
Q

What are some of the effects caused by stimulation of the M3 muscarinic acetylcholine receptor?

A

Gq causes stimulation of phospholipase C, leading to increased salivation and broncho-constriction

Foundations of Medicine JMO (56 decks)

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