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Nervous system Flashcards

(129 cards)

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1
Q

What is a membrane potential?

A

Difference in the concentration of different ions across the cell

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2
Q

What ions contribute to the resting membrane potential

A

Na+
K+
A- - anions which have a negative charge due to amino acids

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3
Q

Concentration of ions inside cell

A 
Na+ = 15mM
K+= 150mM 
A- = 60mM
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4
Q

Concentration of ions outside the cell

A 
Na+ = 150mM
K+ = 5mM
A- = 0
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5
Q

What contributes most to the membrane potential?

A

Potassium ions

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6
Q

What is resting potential?

A

-70mV

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7
Q

What are the stages of an action potential?

A 
Resting potential
Stimulus
Threshold
Action potential
Repolarisation
Hyperpolarisation 
Returns to resting
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8
Q

Sodium voltage gated channel proteins

A

have 2 separate gates - inactivation and activation

in resting state the inactivation gate is open but the activation gate is closed

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9
Q

Process of action potential generation

A
  1. Stimulus causes sodium ion channels to open and sodium moves into the cell
  2. Once threshold is reached the sodium voltage gated channel is activated and both gates open
  3. there is an influx of sodium ions
  4. causes depolarisation and more channels to open, increasing depolarisation
  5. Potassium channels open and there is an outflow of potassium ions
  6. Inactivation gate of voltage gated sodium ion channels close
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10
Q

Repolarisation

A

The leaky sodium ion channels and potassium ion channels allow outflow of sodium and potassium ions causing repolarisation

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11
Q

Hyperpolarisation

A

Outflow of potassium ions can be large enough to cause hyperpolarisation so the cell becomes more negative than resting potential. The potassium ion voltage gated channels close and the membrane potential is restored by the sodium/ potassium pump

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12
Q

Types of refractory period

A
  1. Absolute

2. Relative

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13
Q

Absolute refractory period

A

No stimulus can initiate a second action potential because the inactivated sodium gate is closed/ cannot reopen

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14
Q

Relative refractory period

A

period of time when a second action potential can only be initiated with there is a larger than normal stimulus are this is when the potassium channels are still open and so there is hyperpolarisation

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15
Q

How are action potentials propagated?

A

Influx of sodium ions causes adjacent voltage gated channels to open and cause the action potential to travel along the membrane

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16
Q

Continuous conduction

A

step by step depolarisation and repolarisation of the adjacent segment of the membrane . Occurs in unmyelinated neurons and muscle fibres

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17
Q

saltatory conduction

A

Occurs in myelinated neurons becaus there is an uneven distribution of voltage gated channel proteins - few where there is myelin sheath and many at nodes of ranvier

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18
Q

How does saltatory conduction work?

A

An electric current flows through the ECF surrounding the myelin and through the cytosol from one node to the next causing the sodium ion channels to open at the next node.

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19
Q

What is special about saltatory conduction

A

The action potential leaps from one node to the next and so is energy efficient as there are smaller regions of depolarisation

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20
Q

what factors affect the speed of propagation?

A

Myelination
axon diameter - larger diameter the faster rate of conduction due to larger surface area
temperature - quicker when warmer due to rate of diffusion

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21
Q

What are the different types of neurotransmitter?

A

Excitatory and inhibitory

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22
Q

Excitatory neurotransmitter

A

One that causes depolarisation of the post-synaptic membrane - brings it closer to threshold

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23
Q

Inhibitory neurontransmitter

A

Causes hyperpolarisation of the post synaptic membrane

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24
Q

Main neurotransmitters

A 
Glutamate
Serotonin
Dopamine
Histamine
ATP
Acetylcholine
Noradrenaline
Glycine 
Neuropeptides
GABA
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25
Glutamate
Main excitatory in CNS
26
GABA
Main inhibitory in adult brain
27
Glycine
Main inhibitory in spinal cord
28
Acetylcholine
excitatory at NMJ and inhibitory at heart
29
Receptors of acetlycholine
Nicotinic and muscarinic Nicotinic at NMJ Muscarinic is inhibitory only at heart muscle
30
Histamine
Excitatory
31
Noradrenaline
Excitatory and inhibitory
32
Receptors of noradrenaline
Alpha 1&2 | Beta 1-3
33
Neuropeptides
excitatory and inhibitory - they assist neurotransmitters
34
ATP
Excitatory
35
Serotonin
Inhibitory and excitatory
36
How many receptors does serotonin have?
13 - all GPCRs except 5-HT3 | main controller of mood
37
Dopamine
Excitatory and inhibitory
38
Dopamine receptors
D1-5 linked to schizophrenia and parkinsons
39
What neurotransmitter works in the sympathetic NS post-ganglionic?
Noradrenaline
40
Formation of noradrenaline
Tyrosine-DOPA-Dopamine-Noradrenaline
41
What controls the presynaptic levels of serotonin, noradrenaline, adrenaline and dopamine at the presynaptic membrane?
Monoamine oxidase
42
What neurotransmitter works at an adrenal medullary cell assisting adrenal catecholamine release?
Adrenaline
43
Formation of adrenaline
Tyrosine-DOPA-Dopamine-Noradrenaline-Adrenaline
44
What inhibits noradrenaline release?
Presynaptic reuptake | Catechol-o-methyltransferase (COMT) which breaks it down at postsynaptic neuron
45
Serotonin formation
Tryptophan-5hydroxytryptophan-5hydroxytryptamine (5-HT)
46
What does serotonin act on?
CNS Gut CVS Blood
47
Serotonin role in CNS
``` Mood memory aggression appetite sleep addiction ```
48
Serotonin role in Gut
increased motility | emesis
49
Serotonin role in CVS
Vasoconstriction | increases heart rate
50
Serotonin role in blood
Platelet activation
51
Alpha 1 adrenergic receptor
Arterioles and bladder Vasoconstriction and constriction Affected by adrenaline and noradrenaline
52
Alpha 2 adrenergic receptor
Central and presynaptic Inhibition and inhibition of release of adrenaline and noradrenaline
53
Beta 1 adrenergic receptor
Heart | Increases heart rate and contractility. Affected by adrenaline and noradrenaline
54
Beta 2 adrenergic receptor
Bronchi and muscle blood vessels and uterus causes bronchodilation and dilation of muscle blood vessels and relaxation of uterus Affected by adrenaline only
55
Beta 3 adrenergic receptors
Fat cells - lipolysis Thermogenesis Affected by adrenaline and noradrenaline
56
Catecholamines
Adrenline and noradrenaline
57
GPCR classification
Gs Gi Gq
58
Gs receptor
Adrenergic Beta 1 and heart Stimulates adenylate cyclase to increase cAMP concentration and activate protein Kinase A. Increases rate and strength of contractions
59
Gi receptor
cholinergic muscarinic 2 in heart . Inhibits adenylate cyclase decrease cAMP. Decreases rate and strength of contractions
60
Gq receptor
Adrenergic alpha 1 in blood vessels. IP3 opens calcium ion channels and activates protein kinase C. Causes vasoconstriction
61
Peripheral neurotransmitters
Acetylcholine | Noradrenaline
62
CNS neurotransmitters
``` Acetylcholine Noradrenaline Dopamine Serotonin GABA Glutamate Endorphins/ enkephalins Substance P Glycine ```
63
Role of acetylcholine
motor function regulation emotion arousal
64
Role of noradrenaline
memory arousal circadian rhythm endorphin release in spinal cord which inhibits nociception
65
Role of dopamine
Motor function regulation memory emesis regulation of hormone release
66
Role of serotonin
``` mood memory appetite sleep endorphin release in spinal cord and inhibits nociception ```
67
GABA receptors
GABA a - chlorine channel linked | GABA b - GPCR
68
Glutamate receptors
NMDA and non-NMDA - KA and AMPA
69
what do Endorphins/ Enkephalins do?
Inhibits nociception in dorsal horn of spinal cord
70
Substance P
amplifies nociception in the dorsal horn of spinal cord
71
What are the types of sensory cells/ receptors
``` Chemoreceptors Thermoreceptors Mechanoreceptors Photoreceptors Baroreceptors Hydroreceptors Magnetoreceptors Nociceptors Osmoreceptors Proprioceptors ```
72
Autonomic
regulates functions with little or no voluntary control, via a pair of opposing systems = sympathetic and parasympathetic
73
Parasympathetic NS
Comfort
74
Sympathetic NS
Crisis
75
What tissues can be innervated by the autonomic NS
``` smooth muscle cardiac muscle exocrine glands endocrine glands fat cells ```
76
What does the parasympathetic nervous system affect?
``` Pupils salivary glands heart rate bronchi gut bladder ```
77
What does PSNS do to pupils?
constricts
78
What does PSNS do to salivary glands?
stimulates
79
What does PSNS do to heart rate?
decreases
80
What does PSNS do to bronchi?
constricts
81
What does PSNS do to gut?
stimulates peristalsis and gastric acid secretion
82
What does PSNS do to bladder?
stimulates contraction, allows urine to be passed
83
What are the pathways of the parasympathetic NS?
Craniosacral
84
What does the sympathetic NS affect?
``` Arterioles sweat glands pupils salivary glands heart rate bronchi gut bladder ```
85
What does SNS do to arterioles?
constricts
86
What does SNS do to sweat glands?
stimulates via ACh receptors
87
What does SNS do to pupils?
dilates
88
What does SNS do to salivary glands?
inhibits
89
What does SNS do to heart rate?
increases
90
What does SNS do to bronchi?
dilates via circulating adrenaline
91
What does SNS do to gut?
inhibits peristalsis
92
What does SNS do to bladder?
inhibits contraction - cannot pass urine
93
What are the pathways of the sympathetic NS?
Thoracolumbar - only input between T1 and L2
94
Which cranial nerves are autonomic?
oculomotor, facial, glossopharyngeal and vagus
95
Parasympathetic pathway
2 neurones | long pre-ganglionic and short post-ganglionic
96
Sympathetic pathway
2 neurone pathway | short pre-ganglionic and long post-ganglionic
97
Ganglia of sympathetic NS
ascends to supply head, descends to supply pelvis directly innervates adrenal medulla directly from pre-ganglionic neurone releases adrenaline
98
Horner's syndrome
Damage to the sympathetic nerves of face causing miosis, ptosis, lack of sweating and facial flushing. could be a sign of cancer at the top of the thorax.
99
What is miosis?
Pupil constriction
100
What is ptosis?
Droopy eyelid
101
Autonomic neurotransmitterS
acetylcholine | noradrenaline
102
Muscarinic 1 receptor
autonomic ganglia, synaptic transmission
103
Muscarinic 2 receptor
stomach - acid secretion
104
Muscarinic 3 receptor
``` bronchi - constriction bladder - contraction gut - increases peristalsis eye - accommodation salivary glands - saliva secretion stomach - acid secretion ```
105
Muscarinic 4 receptor
CNS - multiple roles
106
Muscarinic 5 receptor
CNS - multiple roles
107
Atropine
blocks muscarinic receptor to increase heart rate
108
Isoprenaline
can be used to activate beta 1 receptors
109
how to treat Hyperhidrosis
can be treated locally by botox injections which prevent synaptic ACh release
110
Pilocarpine
selective M3 agonist used to treat glaucoma by constricting the pupil
111
Anaphylaxis
results in profound histamine induced hypotension and bronchospasm - adrenaline is used to treat it as it stimulates both alpha 1 and beta 2
112
Ear drum
Tympanic membrane
113
Middle ear
``` Made up of 3 bones oval window round window stapedius muscle tensor tympanic muscle eustachian tube ```
114
bones of middle ear
OSSICLES malleus incus stapes
115
Membranes of ear
vestibular basilar tectorial
116
Organ of Corti
on top of the basilar membrane and beneath the tectorial membrane with hair cells on the surface which have stereocilia the organ of corti is embedded in endolymph
117
Fluid spaces
Scala vestibuli - perilymph Scala tympani - perilymph Scala media - endolymph electrochemical potential between the spaces
118
Hair cells
inner hair cells - responsible for transducing the mechanical energy outer hair cells stereocilia
119
How is an action potential generated in the ear?
waves of vibration in scala media causes membranes to move and hair cells bend - moving ions and creating an action potential
120
What happens in the hair cells when an action potential is generated in the ear
as the membranes move the hair cells move. The hair cells have thick bases containing potassium solution and stereocilia on the top which is bathed in endolymph which is rich in potassium ions. When the stereocilia move the tip links stretch and mechanical gates channels open and potassium diffuses, opening calcium ion channels to open and cause neurotransmitter release forming an action potential .
121
Pitch
Varied frequencies which are detected at different positions along the basilar membrane
122
Mechanism of damage from noise
damage to hair cells/ cilia inflammation excitotoxicity
123
Acoustic reflex
method to try and dampen the sound tensor tympani attached to the tympanic membrane and stapedius to the stapes the muscles contract in response to loud noise contraction of stapedius pulls stapes and reduces the intensity of the sound reaching the cochlea
124
Ineffectiveness of acoustic reflex
muscles fatigue quickly
125
Rinnes test
normal result = air conduction>bone conduction sensorineural deafness = air conduction>bone conduction conductive deafness = bone conduction> air conduction
126
Webers test
normal = sound heard equally in both ears sensorineural deafness = sound is louder on side of intact ear conductive deafness = sound is louder on side of affected ear
127
vestibular apparatus
``` near to cochlea: semi circular canals utricle saccule contains endolymoh and perilymph ```
128
balance
rotation of head movements can be detected in all planes as the semi circular canals are in all 3 planes.each canal is an ampulla which contains the crista ampullaris
129
Crista ampullaris
the sensing mechanism linked to vestibular nerve

Physiology (46 decks)

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