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Peer teaching > Neuro > Flashcards

Neuro Flashcards

1
Q

what does white matter contain?

A

myelinated axons

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2
Q

what does grey matter contain?

A

cell bodies and no myelin sheaths

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3
Q

what myelinates axons in the CNS and PNS?

A

CNS: oligodendrocytes

PNS: schwann cells

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4
Q

what is a tract?

A

location of a pathway

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5
Q

what is a commissure?

A

tract connecting one hemisphere to the other - tracts that cross the midline

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6
Q

what is a lemnisci?

A

narrow strip of fibres

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7
Q

what is a funiculi?

A

rope or cord

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8
Q

what is a fasiculi?

A

bundle e.g. gracile fasiculus

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9
Q

what is a capsule?

A

sheet of white matter fibres that border a nucleus of grey matter

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10
Q

what is a column?

A

longitudinally running fibres separated by other structures e.g. dorsal column

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11
Q

what is a cortex?

A

laminated grey matter on outside of brain e.g. motor cortex

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12
Q

what are nuclei?

A

collection of nerve cell bodies within the CNS

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13
Q

what are ganglia?

A

collection of nerve cell bodies the CNS (e.g. dorsal root ganglia in PNS) and some inside the CNS with a capsule e.g. basal ganglia

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14
Q

what are afferents?

A

axons taking information towards the CNS e.g. sensory fibres

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15
Q

what are efferents?

A

axons taking information to another site from the CNS e.g. motor fibres

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16
Q

what is reticular?

A

netlike, where grey and white matter mix e.g. reticular formation of brainstem

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17
Q

what is the coronal plane?

A

vertical/frontal - parallel with coronal suture of skull

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18
Q

what is the horizontal plane?

A

transverse, cuts body in half unequally

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19
Q

what is the sagittal plane?

A

cuts down nose, parallel with sagittal suture

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20
Q

what is ipsilateral/contralateral?

A

ipsilateral: same side
contralateral: opposite side

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21
Q

what is medial/median?

A

medial: towards midline
median: at midline

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22
Q

what is lateral?

A

away from midline

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23
Q

what is rostral/caudal?

A

rostral: towards nose (anterior)
caudal: towards tail (posterior)

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24
Q

what is dorsal/ventral in brainstem and cord?

A

dorsal: posterior
ventral: anterior

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25
Q

what is dorsal/ventral in cerebrum?

A

dorsal: superior
ventral: inferior

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26
Q

what are sulci?

A

grooves

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27
Q

what are gyri?

A

ridges

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28
Q

what is the function of the frontal lobe?

A

voluntary movement on opposite side of body

frontal lobe of dominant hemisphere controls speech (Broca’s area) and writing (if right handed, then left hemisphere is dominant etc)

intellectual functioning, thought processes, reasoning and memory

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29
Q

what is the function of the parietal lobe?

A

receives and interprets sensations, including pain, touch, pressure, size, shape and body-part awareness (proprioception)

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30
Q

what is the function of the temporal lobe?

A

understanding the spoken word, sounds and memory/emotion

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31
Q

what is the function of the occipital lobe?

A

understanding visual images and meaning of written words

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32
Q

what underlies the cortex?

A

white matter

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33
Q

where are grey matter structures located in the brain?

A

deep in white matter, surround ventricles

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34
Q

what grey matter structures are in the brain?

A

thalamus, hypothalamus, basal ganglia

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35
Q

what is the function of the thalamus?

A

relay centre direction inputs to cortical areas

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36
Q

what is the function of the hypothalamus?

A

links endocrine system to brain and involved in homeostasis

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37
Q

what does the basal ganglia consist of? what is its function?

A

caudate nucleus, putamen and globus pallidus

motor control, cognition and non-motor behaviour

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38
Q

what is the striatum?

A

caudate and putamen

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39
Q

what is the lentiform nucleus?

A

globus and putamen

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40
Q

what is the cerebellum? what is its function?

A

coordinates voluntary movement and balance, equilibrium and muscle tone

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41
Q

what is the structure of the cerebellum?

A

lies over dorsal surface of brains stem, attached to it by 3 peduncles

separated from dorsal brainstem by 4th ventricle which forms part of its roof

folded cortex, white matter and deep inner nuclei

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42
Q

how is the cerebellum attached to the brainstem? which side is it attached to?

A

dorsal

superior peduncle: midbrain
middle peduncle: pons
inferior peduncle: medulla

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43
Q

how is the cerebellum separated from the dorsal brainstem?

A

4th ventricle - forms part of its roof

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44
Q

what do cerebellar injuries lead to?

A

slow and uncoordinated movement

asynergia, intention tremor, hypotonia, nystagmus

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45
Q

what is asynergia?

A

loss of coordination of motor movement

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46
Q

what is intention tremor?

A

movement tremors

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47
Q

what is hypotonia?

A

weak muscles

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48
Q

what is nystagmus?

A

abnormal eye movements

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49
Q

what are the functions of the brainstem?

A

special senses, sensory/motor for head and neck via CNs, autonomic regulation of the body, regulates consciousness, pathway between brain and spinal cord

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50
Q

what does the midbrain consist of?

A 
tectum (superior and inferior colliculi) 
cerebral peduncle (tegmentum and crus cerebri)

surrounds cerebral aqueduct?

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51
Q

what does the midbrain surround?

A

cerebral aqueduct

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52
Q

what cell types does the CNS contain?

A

nerve cell/neurones: pyramidal, stellate, Golgi, Purkinje

neuroglia: astrocytes, oligodendrocytes, microglia

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53
Q

where does fertilisation occur?

A

uterine tube

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54
Q

what are the first clump of cells after fertilisation

A

morula

16 cells

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55
Q

what does the morula develop into?

A

blastocyst (more than 16 cells) with hole in the middle called blastocele

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56
Q

what is gastrulation?

A

single layer blastula developing into trilaminar disc (gastrula)

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57
Q

what is a gastrula?

A

trilaminar disc

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58
Q

what is neurulation?

A

process of formation of the embryonic nervous system

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59
Q

what happens in neurulation?

A

ectoderm thickens in midline to form neural plate in third week of development

ectoderm undergoes differential mitosis to cause formation of midline groove (neural groove

groove deepens and eventually detaches from the overlying ectoderm to form the neural tube

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60
Q

how is the neural plate formed?

A

ectoderm thickens in the midline to form the neural plate in 3rd week

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61
Q

how is the neural groove formed?

A

ectoderm undergoes differential mitosis

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62
Q

what lies lateral to the neural plate?

A

presumptive neural crest cells which run dorso-laterally along neural groove

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63
Q

how do presumptive neural crest cells run?

A

dorsolaterally along neural groove

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64
Q

what do neural crest cells develop into?

A

sensory (dorsal root) ganglia of spinal cord and CNs V, VII, IX, X

Schwann cells

pigment cells

adrenal medulla

bony skull

meninges

dermis

a lot of the head and neck

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65
Q

development of the brain and spinal cord

A

rostral portion of neural tube develops into brain (CNS)

caudal portion of the neural tube develops into the spinal cord

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66
Q

what does the central cavity within the spinal cord develop into?

A

central canal of spinal cord and ventricles of the brain

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67
Q

what happens in the 5th week of embryonic development?

A

three primary brain vesicles can be identified

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68
Q

when can primary brain vesicles be identified?

A

5th week

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69
Q

what are the 3 primary brain vesicles?

A

prosencephalon (forebrain)

mesencephalon (midbrain)

rhombencephalon (hindbrain)

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70
Q

how do secondary brain vesicles form? when?

A

further differentiation

7th week

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71
Q

what does the prosencephalon differentiate into?

A

telencephalon and diencephalon

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72
Q

what does the mesencephalon differentiate into?

A

mesencephalon

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73
Q

what does the rhombencephalon differentiate into?

A

metencephalon and myelencephalon

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74
Q

what does the telencephalon give rise to?

A

cerebral hemisphere and lateral ventricles

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75
Q

what does the diencephalon give rise to?

A

thalamus, hypothalamus, third ventricle

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76
Q

what does the mesencephalon give rise to?

A

midbrain (colliculi) and aqueduct

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77
Q

what does the metencephalon give rise to?

A

cerebellum, pons and upper part of 4th ventricle

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78
Q

what does the myelencephalon give rise to?

A

medulla oblongata and lower part of 4th ventricle

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79
Q

what does the central cavity of the brain develop into?

A

forming system of chambers (ventricles) which contain CSF

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80
Q

when does the neural tube usually close?

A

end of 4th week

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81
Q

what is spina bifida?

A

failure of the tube to close in the spinal cord

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82
Q

what is anencephalus?

A

failure of the tube to close in the cephalic region (brain)

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83
Q

why may the neural tube fail to close?

A

due to faulty induction or environmental teratogens (any agent that can disturb the development of the embryo) acting on neuroepithelial cells

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84
Q

developmental milestones at 3 weeks, 10 weeks, 3, 5, 7 and 9 months

A

3 weeks: eye formation

10 weeks: cerebral expansion and commissures

3 months: basic structures established

5 months: myelination has begun

7 months: lobes of cerebrum have formed

9 months: gyri and sulci formed

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85
Q

what are abnormalities to the CNS dependent on?

A

time of infection

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86
Q

what are critical periods?

A

6th week: eye malformation, e.g. cataracts

9th week: deafness can occur e.g. malformation of organ of Corti

5th to 10th week: cardiac malformation

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87
Q

when do CNS disorders generally occur?

A

2nd trimester

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88
Q

when does the risk of CNS disorders fall? why?

A

after 16 weeks

most structures have already developed

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89
Q

development of sensation

A

innervation of dermal skin, dorsal root ganglion connecting to spinal cord, C-fibre connection, organised thalamus, retinal inputs, myelination, connections from thalamus to cortex

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90
Q

when is the dermal skin innervated?

A

28 weeks

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91
Q

when does the dorsal root ganglion connect to the spinal cord?

A

from 8 weeks

non-noxious (no pain detected)

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92
Q

when is there C-fibre connection?

A

from 19+ weeks

noxious (painful) stimuli

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93
Q

when is the thalamus organised?

A

from 8+ weeks

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94
Q

when do retinal inputs arrive?

A

14-16 weeks

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95
Q

when does myelination occur?

A

from 25 weeks

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96
Q

when does the thalamus connect to the cortex?

A

from 24 weeks

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97
Q

what is the function of the brain stem?

A

basic vital functions

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98
Q

what is the corpus callosum?

A

fibre bundle connecting left and right hemispheres together

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99
Q

how many neurons does the cerebellum have?

A

70% neurones

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100
Q

how do structures connect to the cerebellum?

A

all sensorimotor, cognitive and motivational/effective structures connect to cerebellum via re-entrant loops

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101
Q

where does the cerebellum receive input from?

A

motor cortex, brain stem nuclei, sensory receptors

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102
Q

what is the output of the cerebellum?

A

modulates UMNs

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103
Q

skill development of the cerebellum

A

always working, predicting the consequences and correcting actions so they can be improved if there’s error

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104
Q

what are the main components of the basal ganglia?

A

dorsal striatum (caudate nucleus and putamen)

ventral striatum (nucleus accumbens and olfactory tubercle)

globus pallidus (internal and external segment)

ventral pallidum

substantia nigra

subthalamic nucleus

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105
Q

how does the basal ganglia connect to inputs of the brain?

A

by recurrent loops

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106
Q

competing systems in the brain and what the basal ganglia does with them

A

emotions, cognitions, sensorimotor

selects which one to do

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107
Q

what are the outputs of the basal ganglia?

A

inhibitory and tonically active (slow and continuous)

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108
Q

what are the functions of the hippocampus?

A

episodic memory

essential for the construction of mental images

vital role in STM

important for spatial memory and navigation

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109
Q

what is the hippocampus part of?

A

limbic system

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110
Q

what is anterograde tract tracing?

A

transport from neuronal cell bodies to axon terminals

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111
Q

what is retrograde tract tracing?

A

transport from axonal terminals to neuronal cell bodies

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112
Q

how do neurones project?

A

not A -> B, but A -> B -> C -> D

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113
Q

what are class A experiments?

A

diagnosis

some behavioural, physiological or pharmacological variable is manipulated and consequent effects on brain activity/structure are measured

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114
Q

critical evaluation of class A experiments

A

diagnosis

are there adequate controls to ensure that observed changes are produced only by claimed behavioural/physiological/pharmalogical manipulations?

are measured changes specific to claimed regions in brain?

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115
Q

what are type B experiments?

A

treatment

some aspect of brain structure (lesion) or activity (stimulation/inhibition) is manipulated and effects on behaviour/physiology/endocrinology is measured

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116
Q

critical evaluation of type B experiments

A

are effects of brain manipulation to claimed changes?

is used brain manipulation specific to intended neural structures?

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117
Q

basis of detection of brain activity

A

increases in activity -> increase in release of neurotransmitters and breakdown products (CSF via lumbar puncture)

active regions need more O2/blood (haemodynamic changes detected by modern imaging)

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118
Q

what does EEG do?

A

electroencephalogram

regional brain activity underlying electrodes

signs of epilepsy

(overexcitation of neurons -> cell death)

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119
Q

what are EEGs sensitive/insensitive to?

A

sensitive to activity in temporal regions, less to spatial regions

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120
Q

components of neurones

A

dendrites, cell body/soma, axon, presynaptic terminal

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121
Q

how do neurons receive and transmit information?

A

receive info via dendrites, transmit to soma

transmit info via axons and action potentials are propagated from the axon hillock

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122
Q

neurons stained by H&E

A

haemotoxylin stains nucleic acids blue

eosin stains proteins red

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123
Q

what stains myelin?

A

luxor fast blue (LFB)

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124
Q

what stains Nissl (RER)?

A

cresol violet (CV)

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125
Q

what is neural plasticity?

A

basis of learning and memory

ability of the brain to change throughout an individual’s life

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126
Q

what is an early marker of Alzheimers?

A

loss of dendritic spines

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127
Q

functional classes of neurons

A

afferent (sensory), efferent (motor), interneurons (within CNS)

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128
Q

what forms the nerves of the PNS?

A

groups of afferent and efferent neurone axons together with connective tissue and blood vessels

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129
Q

what is a nerve fibre?

A

single axon

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130
Q

what is a nerve?

A

bundle of axons (fibres) bound together by connective tissue

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131
Q

what do afferent neurons do?

A

convey information from tissues and organs towards the CNS

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132
Q

structure of afferent neurons

A

sensory receptors at peripheral ends (farthest from CNS)

axon divides after leaving cell body

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133
Q

what do sensory receptors do? where are they located?

A

at peripheral ends of afferent neurons

respond to various physical/chemical changes in their environment by generating electrical signals in neurone

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134
Q

what does the axon of an afferent neuron divide into?

A

peripheral process begins where dendritic branches converge from receptor endings - long

central process enters CNS to form junctions with other neurons - shorter

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135
Q

are afferent process inside or outside of the CNS?

A

cell body and peripheral process are outside the CNS/in PNS

a part of the central process enters CNS

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136
Q

what do efferent neurons do?

A

convey information away from CNS to effector cells, e.g. muscle, gland, etc

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137
Q

are efferent neurons inside or outside of the CNS?

A

cell bodies and dendrites are within the CNS, axons extend out to periphery

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138
Q

what do interneurons do? where do they lie?

A

connect neurons within CNS - form majority of neurons

lie entirely within CNS

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139
Q

what is myelin?

A

20-200 layers of highly modified plasma membrane wrapped around axon by nearby supporting cell

highly compacted - 70% lipid and 30% protein

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140
Q

what are the myelin-forming cells in the CNS?

A

oligodendrocytes - can branch to form myelin on up to 40 axons

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141
Q

what are the myelin-forming cells in the PNS?

A

Schwann cells - form individual myelin sheaths surrounding 1-1.5 mm long segments at regular intervals along axons

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142
Q

what are nodes of Ranvier?

A

spaces between adjacent sections of myelin where axon’s plasma membrane is exposed to ECF

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143
Q

what does myelin do?

A

increases speed of conduction along axons

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144
Q

what are features of myelinated axons?

A

thicker

found in mostly somatic nerves e.g. fast sensory/motor systems, muscle and spinal systems

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145
Q

what are features of unmyelinated axons?

A

thinner

post-ganglionic autonomic fibres, fine sensory fibres, olfactory neurones and interneurons - where speed is not of the essence e.g. hypothalamus

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146
Q

what do glial cells do?

A

surround soma, axon, dendrites of neurones and provide them with physical and metabolic support

147
Q

function of oligodendrocytes

A

myelinating multiple axons

insulates axon segments, enabling rapid nerve conduction

metabolic support - transport metabolic products directly into axons

148
Q

functions of astrocytes

A

regulate composition of ECF in CNS by removing K+ ions and neurotransmitters (e.g. glutamate)

take up glutamate and convert it to glutamine and release it, then neurons can take it up and convert back to glutamate for reuse

BBB

sustain neurones metabolically - provide glucose and remove ammonia

149
Q

what are astrocytes in the grey matter called?

A

protoplasmic

150
Q

what are astrocytes in the white matter called?

A

fibrous

151
Q

what are specific types of astrocytes?

A

radial glia, Mueller glia and Bergmann glia

152
Q

what are radial glia?

A

guide developing neurones

only developmental, not found in adult brain

153
Q

what are Mueller glia?

A

specialised radial glia of the retina

154
Q

what are Bergmann glia?

A

found in cerebellum

support purkinje cell dendrites and synapses

155
Q

what are microglia? what are they derived from?

A

specialised macrophage-like cells that perform immune functions in the CNS

derived from progenitors that migrate into the CNS from the periphery

156
Q

what do microglia do?

A

proliferate at sites of injury (phagocytic)

phagocytose debris/microbes

contribute to synaptic plasticity - can eat unwanted dendritic spines

157
Q

what are microglia like in the cortical grey matter?

A

more ramified (branched)

158
Q

when can be microglia be bad?

A

being too sensitive and causing excessive inflammation and destruction of dendritic spines

159
Q

what are ependymal cells? what do they do?

A

line fluid filled cavities within brain (ventricles) and spinal cord

regulate production and flow of CSF

cilia, microvilli, desmosomes

provide barrier between CSF and brain

160
Q

diseases of neurons, glia or both?

epilepsy
MND
depression
Alzheimers
MS
A

epilepsy: neurone

MND: neurons and glia

depression: neurons and glia

Alzheimers: neurons and glia

MS: neurons and glia (oligodendrocytes attacked)

161
Q

what is attacked in MS?

A

oligodendrocytes

162
Q

what forms the BBB?

A

endothelial cells, pericytes, astrocytes

163
Q

what are pericytes?

A

contractile cells that wrap around the endothelial cells of capillaries and venules

164
Q

what are the features of the BBB?

A

endothelial tight junctions

astrocyte end feed

pericytes

continuous BM (lacks fenestrations)

requires specific transporters for glucose, essential ions etc

165
Q

what are circumventricular organs?

A

parts of brain that lack the BBB

need to be in contact with blood for sensory role to monitor

posterior pituitary

166
Q

what is CSF?

A

clear, colourless liquid containing protein, urea, glucose and salts

167
Q

where does CSF circulate?

A

through subarachnoid space (around brain and spinal cord) and within ventricles

offers protection by cushioning brain from gentle movements

168
Q

what connects ventricles and subarachnoid spaces?

A

cisterns

169
Q

what is the volume of CSF?

A

120mls

170
Q

what is CSF produced by?

A

ependymal cells in choroid plexuses of lateral ventricles

171
Q

what is the choroid plexus?

A

formed from modified ependymal cells

around a network of capillaries, large SA

172
Q

how is CSF absorbed?

A

via arachnoid granulations (VILLI) e.g. in superior sagittal sinus

173
Q

what is hydrocephalus?

A

abnormal accumulation of CSF in ventricular system

often due to blocked cerebral aqueduct

174
Q

what does hydrocephalus lead to?

A

build up of pressure which can damage brain tissue as skull is hard in adults

in children with soft skulls, the pressure causes the skull to bulge and look abnormal, and damage the brain

175
Q

what is the resting membrane potential?

A

all cells under resting conditions have a potential difference across their plasma membranes, with the inside of the cell negatively charged with respect to the outside

176
Q

what is the magnitude/typical resting potential?

A
  • 40 to -90mV

typical: -70mV

177
Q

how is the concentration gradient established?

A

Na+/K+ ATPase pumps in neurone membrane develop conc. gradients by pumping 3 Na+ ions out of neurone for every 2 K+ ions that are pumped in, against their concentration gradients, via active transport

Na+ ions concentrated outside, K+ ions inside

178
Q

what channels are open in a resting membrane potential?

A

very few Na+ voltage gated channels - few Na+ ions can diffuse back into the axon

K+ voltage gated channels closed

leak K+ channels are open, increasing membrane permeability -> K+ ions diffusing out of axon down conc. gradient

179
Q

what makes Na+ ions able to enter the neurone?

A

when a neurotransmitter binds to a specific ligand-gated ion channel on the post synaptic membrane

180
Q

what is initial depolarisation?

A

inflow of Na+ ions results in the inside of the neurone to become slightly more positive

181
Q

what does the initial depolarisation stimulate?

A

opening of some voltage-gated Na+ channels, leading to further entry of Na+ ions into the neurone and further depolarisation

182
Q

what does further depolarisation lead to?

A

when the membrane reaches critical threshold potential (-55mV), depolarisation becomes a positive feedback loop

183
Q

what is the critical threshold potential? what does it lead to?

A

-55mV

positive feedback loop - Na+ entry causes depolarisation, which opens more voltage-gated Na+ channels, which leads to more depolarisation etc

184
Q

what is reverse polarisation? what does it lead to?

A

+30mV

voltage-gated Na+ channels are inactivated and Na+ influx stops

185
Q

what opens in a delayed response to the initial depolarisation? what does this lead to?

A

sluggish voltage-gated K+ channels

K+ diffuses out of the neurone, down the concentration gradient, causing rapid repolarisation

186
Q

what causes rapid repolarisation?

A

delayed opening of the sluggish voltage gated K+ channels in response to initial depolarisation

187
Q

what causes hyperpolarisation?

A

return of the neurone to negative potential causes voltage gated K+ channels to close, but slowly

membanes permeability to K+ remains above resting levels -> continued outflow, more negative than -70mV

188
Q

when is the resting membrane restored?

A

when voltage-gated K+ channels finally close

189
Q

what is the absolute refractory period? when does it occur?

A

a second stimulus, no matter how strong, won’t produce a second action potential

voltage-gated Na+ channels are already open or have proceeded to their inactivated state after during the first potential

190
Q

what is the relative refractory period?

A

interval where a second action potential can be produced following the absolute refractory period, only if stimulus strength is greater than usual

lasts until membrane returns to the resting potential

191
Q

what is the function of the refractory periods?

A

limit the number of action potentials an excitable membrane can produce in a given period of time

separate action potentials so individual signals can pass down the axon

192
Q

what causes a current to flow? what does it do?

A

generation of an action potential at a particular segment on the neurone membrane

difference in potential between depolarised membrane and adjacent segments at resting potential

depolarises adjacent membrane, causing voltage-gated Na+ channels to open

193
Q

what causes action potential propagation along the membrane?

A

new action potential generates local currents of its own

depolarise region adjacent to it

etc

194
Q

why can’t the impulse travel backwards?

A

propagation travels in the direction of the region of membrane that has recently been active

adjacent membrane behind potential is in its absolute refractory period - can’t depolarise

195
Q

what does propagation along a membrane depend on?

A

fibre diameter and myelination

196
Q

how does fibre diameter affect propagation speeds?

A

larger the fibre diameter, the faster the action potential propagates, as a larger fibre offers less internal resistance to local current - adjacent regions are able to reach threshold faster

197
Q

how does myelination affect propagation speeds?

A

increases it

less leakage of charge across the myelin - local current can spread farther along axon

conc. of Na+ channels in myelinated region is low - action potentials can only occur at nodes of Ranvier (high conc. of Na+ channels)

198
Q

what is saltatory conduction?

A

action potentials appear to jump from one node to the next as they propagate along a myelinated fibre

faster than in non-myelinated fibres of same axon diameter

199
Q

how do conduction velocities vary?

A

0.5m/s in small-diameter fibres to 100m/s in large-diameter myelinated fibres

200
Q

what is axonal transmission?

A

transmission of information from point A to B

201
Q

what is MS?

A

most common disease of nervous system in young adults

autoimmune

degeneration of myelin an development of scar tissue which disrupts and eventually blocks neurotransmission along myelinated axons

202
Q

what are the symptoms of MS?

A

uncontrolled eye movements - seeing double

slurred speech

partial/complete paralysis

tremor

loss of coordination

weakness

sensory numbness, prickling, pain

203
Q

what is a synapse?

A

an anatomically specialised junction between two neurones at which the electrical activity in a presynaptic neurone influences the electrical activity of a postsynaptic neurone

204
Q

what is an excitatory synapse?

A

membrane potential of a postsynaptic neuron is brought closer to threshold (depolarised)

205
Q

what is an inhibitory synapse?

A

membrane potential of a postsynaptic neuron is either driven further from threshold (hyperpolarised) or stabilised at its resting potential

206
Q

what happens if the membrane of a postsynaptic neuron reaches threshold?

A

generate action potentials that are propagated along its axon to terminal branches which influence the excitability of other cells

207
Q

what types of synapses are there?

A

electrical and chemical (majority)

208
Q

what is the structure of electrical synapses?

A

plasma membranes of presynaptic and postsynaptic cells are joined by gap junctions

allow local currents from arriving action potentials to flow directly across the junction

209
Q

what is the speed of conduction in electrical synapses?

A

extremely rapid

synchronised transmission

210
Q

where are electrical synapses found?

A

brainstem neurons e.g. breathing and hypothalamus and hormone secretion

211
Q

what is the structure of a chemical synapse?

A

plasma membranes of neurons are joined by the synaptic cleft

212
Q

what is the axon terminal?

A

axon of the presynaptic neurone ends in a slight swelling which holds the synaptic vesicles containing neurotransmitter molecules

213
Q

what is the synaptic cleft? what does it do?

A

separates the presynaptic and postsynaptic neurons and prevents direct propagation of the current

214
Q

how are signals transmitted across the synaptic cleft?

A

chemical messenger (neurotransmitter)

more than one may be simultaneously released

215
Q

what is a cotransmitter?

A

more than one neurotransmitter may be simultaneously released from an axon

216
Q

what are synapses covered by? what do they do?

A

astrocytes (glial cell) - reuptake of excess neurotransmitter

217
Q

what happens in the process of neurotransmitter release?

A

calcium ion channels open when an action potential reaches the presynaptic terminal

calcium ions cause vesicles to move to release sites and fuse with cell membrane and discharge their contents

218
Q

what role do calcium ions have in neurotransmitter release?

A

calcium ions cause vesicles to move to release sites and fuse with cell membrane and discharge contents

219
Q

what happens when an action potential reaches a presynaptic terminal?

A

calcium ion channels open

220
Q

what are the 5 processes of synaptic transmission?

A

manufacture - intracellular biochemical processes

storage - vesicles

release - action potential

interaction with post-synaptic receptors - diffusion across synapse

inactivation - breakdown or reuptake

221
Q

what is an example of the processes involved in synaptic transmission?

A

acetylcholine

222
Q

where is acetylcholine used?

A

brain and neuromuscular junction

223
Q

what are the main acetylcholine receptors?

A

muscarinic and nicotinic

224
Q

breakdown/reabsorption of acetylcholine

A

once bound to the postsynaptic receptor, the enzyme acetylcholine esterase breaks it down into choline and acetyl

choline is reabsorbed to be recycled

225
Q

what enzyme breaks down acetylcholine in the synaptic cleft?

A

acetylcholine esterase

226
Q

what are receptors on the postsynaptic neurone called?

A

transmitter-gated ion channels

227
Q

?are transmitter-gated ion channels sensitive to?

A

specific neurotransmitters

228
Q

what happens in an EPSP?

A

many Na+ leave and a few K+ enter

229
Q

what happens in an IPSP?

A

many K+ leave or many Cl- enter

230
Q

what are the two means of combined effects?

A

temporal or spatial summation

231
Q

what is temporal summation?

A

input signals arrive from same presynaptic cell at different times

potentials summate as there are a greater number of open ion channels, thus a greater flow of positive ions into the cell

232
Q

what is spatial summation?

A

two inputs occur at different locations in the postsynaptic neuron

233
Q

when are unbound neurotransmitters removed from the synaptic cleft?

A

actively transported back into the presynaptic axon terminal or by nearby glial cells

diffuse away from receptor site

enzymatically transformed into inactive substances - some reused

234
Q

what are fast neurotransmitters?

A

short lasting effects, tend to be involved in rapid communication

235
Q

what are examples of fast neurotransmitters?

A

acetylcholine, glutamate (excitatory), GABA (inhibitory)

236
Q

what are neuromodulators? what do they do?

A

cause change in synaptic membrane that lasts for longer times

alterations in enzyme activity or influences DNA transcription in protein synthesis

slower events e.g. learning, development, motivational states

237
Q

what are examples of neuromodulators?

A

dopamine, noradrenaline/norepinephrine, serotonin

238
Q

what are the most common local anaesthetics?

A

procaine and lignocaine

239
Q

how do local anaesthetics work?

A

interrupting axonal neurotransmission

blocking sodium channels -> preventing neurons from depolarising, so threshold isn’t met -> no action potential is developed to be propagated

240
Q

what effect do local anaesthetics produce?

A

pain relief as pain isn’t transmitted

241
Q

what can local anaesthetics diffuse through? what does this mean?

A

mucus membranes

act on muscles

242
Q

what is acetylcholine?

A

major neurotransmitter of the PNS at the neuromuscular junction

also used in brain and spinal cord

243
Q

what are neurons that release ACh called?

A

cholinergic neurons

244
Q

synthesis and storage of ACh

A

synthesised from choline (common nutrient in food) and acetyl coenzyme A in cytoplasm of synaptic terminals and stored in synaptic vesicles

245
Q

what stops activation of ACh receptors?

A

conc. decreases due to enzyme acetylcholinesterase

246
Q

where is acetylcholinesterase? what does it do?

A

postsynaptic and presynaptic membranes

rapidly destroys ACh, releasing choline and acetate

247
Q

what are 2 general types of ACh receptor?

A

nicotinic and muscarinic

248
Q

what are nicotinic receptors?

A

respond to ACh and nicotine

contains ion channel

249
Q

where are nicotinic receptors found?

A

neuromuscular junction and brain

250
Q

what are the functions of nicotinic receptors?

A

ones in brain are important in cognitive functions and behaviour

one cholinergic system using them plays role in attention, learning and memory by reinforcing the ability to detect and respond to meaningful stimuli

on presynaptic terminals in reward pathways - tobacco products are addictive

251
Q

what are muscarinic receptors?

A

respond to ACh and mushroom poison muscarine

252
Q

what do muscarinic receptors do?

A

couple with G proteins, which alter the activity of different enzymes and ion channels

253
Q

where are muscarinic receptors present? give examples?

A

brain

junctions where a major division of the PNS innervates peripheral glands and organs

salivary glands, heart and lungs (bronchoconstriction M3)

254
Q

what do cigarettes contain?

A

nicotine (agonists) - interact and open receptor

255
Q

what does sarin do? what does this lead to?

A

inhibits the action of acetylcholinesterase

buildup of ACh in synaptic cleft -> overstimulation of postsynaptic ACh receptors

initially, uncontrolled muscle contractions

eventually, receptor desensitisation and paralysis

256
Q

where is noradrenaline found?

A

transmitter in the peripheral heart and CNS

257
Q

what is noradrenaline affected by?

A 
antidepressant drugs (imipramine and monamine oxidase)
amphetamine (stimulant)
258
Q

how does imipramine affect noradrenaline?

A

blocks reuptake of noradrenaline

therapeutic effect only seen after 3-5 weeks

blockage of reuptake doesn’t cause therapeutic effect, but brain’s response to it does

259
Q

how does monoamine oxidase inhibitor affect noradrenaline?

A

increases amount of noradrenaline by inhibiting enzyme monoamine oxidase which breaks down noradrenaline

260
Q

what causes the breakdown of noradrenaline?

A

monoamine oxidase enzyme

261
Q

how does amphetamine affect noradrenaline?

A

stimulant

increases release and blocks reuptake

262
Q

where is dopamine found?

A

basal ganglia

263
Q

what is dopamine affected by?

A

antipsychotic drugs, stimulants, anti-parkinsons drug

264
Q

how do antipsychotics affect dopamine?

A

e.g. chlorpromazine

antagonist - blocks receptor so other neurotransmitter can’t activate it

265
Q

how do stimulants affect dopamine?

A

amphetamine/cocaine

increases release and blocks reuptake

266
Q

how do anti-parkinsons drugs affect dopamine?

A

L-DOPA increases dopamine manufacture

267
Q

what is serotonin?

A

excitatory effect on pathways that mediate sensations

268
Q

what is serotonin affected by?

A

antidepressants, ecstasy

269
Q

how do antidepressant drugs affect serotonin?

A

e.g. Prozac/Zoloft/sertraline

Selective Serotonin Reuptake Inhibitor

increase in conc. of synaptic serotonin

270
Q

how does ecstasy affect serotonin?

A

neurotoxic to serotonin neurons

destroy terminal of axons

271
Q

what is glutamate?

A

main excitatory neurotransmitter

272
Q

what is GABA?

A

main inhibitory neurotransmitter

273
Q

what happens in Parkinsons? what is L-DOPA?

A

degradation/death of dopaminergic neurons

precursor for dopamine

274
Q

what happens when L-DOPA is given to patients?

A

able to cross BBB

taken up by serotonin neurones and converted and released as dopamine - serotonin neurons have same enzyme needed to convert L-DOPA to dopamine as the dopaminergic ones have

275
Q

what is the interaction between L-DOPA and serotonin neurones?

A

taken up by them, then converted and released as dopamine as they share the enzyme needed to convert L-DOPA to dopamine

276
Q

what is the human hearing range?

A

20 to 20000 Hz

277
Q

at what is the ear most sensitive?

A

1000 - 4000 Hz

278
Q

what are the functions of the outer, middle and inner ear?

A

outer: collect sound
middle: transmission of sound
inner: conversion of sound into neural impulses

279
Q

how does sound enter the ear?

A

through pinna/auricle (exterior part of ear)

then via the external auditory canal/meatus

280
Q

what do features of the points of entry of sound into the ear do?

A

shape of pinna and external auditory canal/meatus help amplify and direct the sound

281
Q

what does the sound reach when travelling though the canal? what does it do?

A

to tympanic membrane (eardrum)

as air molecules push against the membrane, it causes the tympanic membrane to vibrate at same frequency as sound wave

282
Q

vibration of tympanic membrane

A

slowly to low frequency sounds

rapidly to high frequency sounds

283
Q

what marks the end of the external ear and the start of the middle ear?

A

tympanic membrane (ear drum)

284
Q

what is the ear drum?

A

tympanic membrane

285
Q

what is the middle ear?

A

an air filled cavity in the temporal bone of the skull

286
Q

what provides the sensation of the middle ear?

A

glossopharyngeal nerve (CNIX)

287
Q

what are the normal pressures in the external auditory canal and middle ear cavity?

A

normally equal to atmospheric pressure

288
Q

how is the middle ear exposed to atmospheric pressure?

A

via the eustachian tube (auditory tube) - connects the middle ear to the pharynx

289
Q

what is the eustachian tube?

A

connects middle ear to the pharynx - opens into pharynx through a slit-like opening which is normally closed

exposes the middle ear to atmospheric pressure

290
Q

when is the opening of the eustachian tube into the pharynx opened/closed?

A

normally closed

muscle movements e.g. swallowing, yawning or sneezing -> opening of tube

291
Q

when does a difference in pressure between the middle and external ear occur?

A

changes in altitude

292
Q

what can cause pain in the ear? how can it be relieved?

A

constant pressure in the middle ear -> stretching tympanic membrane

yawning/swallowing -> opening of eustachian tube -> pressure in middle ear equilibrates with external atmospheric pressure

293
Q

how are the vibrations of the tympanic membrane transmitted to the inner ear?

A

moveable chain of three bones - ossicles

294
Q

what are ossicles?

A

smallest bones in the body

malleus, incus, stapes

synovial joints between them

295
Q

what do ossicles do?

A

transmit vibrations from the tympanic membrane into the inner ear

act as a piston - couple the vibrations of tympanic membrane to oval window

296
Q

what is the oval window?

A

a membrane covered opening between the middle and inner ear

total force of a sound wave applied to tympanic membrane is completely transferred

297
Q

what is a feature of the oval window that makes it effective for its function?

A

much smaller than membrane

force per area is much greater - adequately transmits sound energy through fluid filled cochlea

298
Q

how can the amount of energy transmitted to the inner ear be lessened?

A

contraction of 2 small muscles in inner ear - tensor tympani and stapedius

299
Q

what muscles lessen the amount of energy transmitted to the inner ear?

A

tensor tympani and stapedius

300
Q

what is the tensor tympani? what is its innervation?

A

small muscle in inner ear

attaches to malleus, contraction dampens the bones movement

mandibular division of trigeminal nerve (V3)

301
Q

what bone does the tensor tympani attach to?

A

malleus

contraction -> dampening its movement

302
Q

what is the stapedius? what is its innervation?

A

small muscle in inner ear

attaches to stapedius, contraction dampens bones movement

facial nerve (VII)

303
Q

what bone does the stapedius attach to?

A

stapes

contraction -> dampening its movement

304
Q

what is the function of the tensor tympani and stapedius muscles?

A

act reflexively to continuous loud noise to protect delicate receptor apparatus in inner ear

can’t protect inner ear from sudden intermittent loud sounds

305
Q

what is the inner ear?

A

cochlea

306
Q

what is the cochlea?

A

inner ear, organ of hearing

spiral shaped, fluid filled space in the temporal bone

307
Q

how many times does the cochlea spiral?

A

2.5 - 2.75 times

308
Q

how is the cochlea divided?

A

almost completely divided lengthwise by membranous tube (cochlea duct)

309
Q

what is the cochlea duct? what does it contain?

A

membranous tube

contains sensory receptors of the auditory system

endolymph - compartment of ECF containing high conc. of K+ and low conc. of Na+

310
Q

what is endolymph?

A

compartment of ECF containing high conc. of K+ and low conc. of Na+

found in cochlea duct

311
Q

what is on either sides of the cochlea duct?

A

compartments filled with perilymph - similar in composition to CSF

scala vestibuli and scala tympani

312
Q

what is perilymph?

A

similar in composition to CSF

in scala vestibuli and tympani

313
Q

what is the scala vestibuli?

A

above the cochlear duct

begins at oval window

entrance to inner ear from the oval window

314
Q

what is the scala tympani?

A

below cochlear duct

connects to middle ear via round window

315
Q

what is the helicotrema?

A

where the scala vestibuli and tympani are continuous, at the far end of the cochlear duct

316
Q

where are the scala vestibuli and tympani continuous?

A

at the helicotrema, at the far end of the cochlear duct

317
Q

how does the oval window transmit sound waves?

A

they receive input from the ossicles

moves in and out of the scala vestibuli, creating waves of pressure

transmitted toward the helicotrema and into the scala tympani where pressure is relieved by movements of the membrane of the round window

318
Q

what is the side of the cochlear duct closes to the scala tympani formed by?

A

basilar membrane

319
Q

what sits on the basilar membrane in the inner ear?

A

organ of corti

320
Q

what is the organ of corti?

A

contains sensitive receptor cells

pressure difference across the duct causes the basilar membrane to vibrate

321
Q

what is the basilar membrane sensitive to?

A

base: narrow and stiff - high frequencies
apex: wider and less stiff - low frequencies

322
Q

what are the receptor cells of the organ of Corti? what are they called?

A

hair cells

mechanoreceptors with hairlike stereocilia protruding from one end

323
Q

what are the groups of hair cells?

A

2 anatomically separate

single row of inner hair cells

4-5 rows of outer hair cells

324
Q

where do the stereocilia lie? what do they do?

A

extend into endolymph fluid and convert pressure waves caused by movement of fluid in cochlear duct into receptor potentials

embedded in overlying tectorial membrane - mechanically alter its movement to sharpen frequency tuning at each point on basilar membrae

325
Q

what leads to bending of the stereocilia?

A

pressure waves displace basilar membrane - hair cells move in relation to the stationary tectorial membrane

326
Q

what causes the membrane of hair cells on organ of Corti to depolarise?

A

stereocilia bend towards tallest member of bundle -> TIP LINKS pull open mechanically gated K+ channels -> influx of K+ from endolymph

327
Q

what are TIP LINKS? what do they do?

A

fibrous connections

when stereocilia bend towards tallest member in bundle, tip links pull open mechanically gated K+ channels -> flow in from endolymph

depolarises membranes

328
Q

what does the influx of K+ from endolymph lead to?

A

change in voltage triggers opening of voltage-gated Ca2+ channels near base of cell -> triggers neurotransmitter release

329
Q

what happens when tip links slack?

A

bending hair cells in opposite direction

closes K+ channels and cell rapidly depolarises

330
Q

what is the neurotransmitter released from the hair cells of organ of Corti? what does it do?

A

glutamate - binds to and activates protein binding sites on terminals of afferent neurones

331
Q

what happens as sound waves vibrate basilar membrane?

A

stereocilia bend back and forth, membrane potential rapidly oscillates and bursts of glutamate are released onto afferent neurons

332
Q

what makes up the cochlear branch of the vestibulocochlear nerve (VIII)?

A

axons from afferent neurons

333
Q

where does the cochlear nerve join the brainstem?

A

at the level of the rostral medulla

334
Q

what happens to the cochlear nerve after it joins the brainstem?

A

fibres bifurcate and end in the dorsal and ventral cochlear nuclei (close to inferior cerebellar peduncle)

335
Q

where are the dorsal and ventral cochlear nuclei?

A

close to inferior cerebellar peduncle

336
Q

what happens from the cochlear nuclei?

A

second-order neurons ascend into the pons where fibres travel to superior olivary nucleus

337
Q

what happens in the superior olivary nucleus?

A

has fibres that leave the brainstem in the vestibulocochlear nerve and end in the organ of Corti - inhibitory function

adjust transmission of auditory info through cochlear nerve by mediating contractions of tensor tympani to loud noises

338
Q

where do fibres travel from the superior olivary nucleus?

A

inferior colliculus of the midbrain

339
Q

what happens from the inferior colliculus of the midbrain in the auditory pathway?

A

inferior brachium (nerve fibre carries auditory information to medial geniculate body of the thalamus

340
Q

what happens from the medial geniculate body in the auditory pathway?

A

fibres travel through the internal capsule to the primary auditory cortex of the temporal lobe

341
Q

where is the primary auditory cortex located?

A

temporal lobe - dorsal surface of the superior temporal gyrus

342
Q

what is the overall neural auditory pathway?

A

cochlear nerve -> brainstem at rostral medulla -> bifurcation, end in dorsal and ventral cochlear nuclei -> superior olivary nucleus -> inferior colliculus (midbrain) -> medial geniculate body (via inferior brachium) -> internal capsule -> primary auditory cortex (Wernicke’s area)

343
Q

where is the medial geniculate body?

A

thalamus

344
Q

where is the inferior colliculus?

A

midbrain

345
Q

what does the inferior brachium do?

A

nerve - transmits auditory info from inferior colliculus to medial geniculate body

346
Q

what is Wernicke’s area? what does it do?

A

region of the temporal lobe surrounding the primary auditory cortex

auditory information is interpreted and understood

superior temporal lobe

processing language in the brain

347
Q

what is Wernicke’s aphasia?

A

patient can’t understand questions and speech will be incomprehensible

348
Q

what is involved in the visual pathway?

A

superior colliculus

lateral geniculate body

349
Q

what is the chorda tympani? what does it do?

A

branch of facial nerve (CNVII)

taste information from tongue

runs through middle ear to carry taste messages to brain

350
Q

what is Bell’s palsy?

A

acute unilateral inflammation of the facial nerve - pain behind ear (chorda tympani and facial nerve in internal acoustic meatus)

paralysis of facial muscles and failure to close eye

351
Q

where does the facial nerve exit the cranial cavity?

A

internal acoustic meatus behind the cochlea - inflammation may result in pain behind ear

352
Q

what is the vestibular apparatus?

A

connected series of endolymph filled, membranous tubes that also connect with the cochlear duct

353
Q

what does the vestibular apparatus consist of?

A

3 membranous semicircular canals and 2 saclike swellings - utricle and saccule

lie in temporal bone on either side of head

354
Q

what do the hair cells in the vestibular apparatus detect?

A

changes in motion and position of the head by stereocilia transaction mechanism

355
Q

what do semicircular canals detect?

A

angular acceleration during rotation of the head along 3 perpendicular axes

activated when nodding head up and down, shaking from side to side and tipping head so ear touches the shoulder

356
Q

what is the structure of the stereocilia in the receptor cells of the semicircular canals?

A

encapsulated within a gelatinous mass (capula)

capula extends across lumen of each semicircular canal at the ampulla (slight bulge in wall of each duct)

357
Q

how are signals about the movement of the head sent to the brain?

A

semicircular canal and attached bodies of hair cells move with head when moving

endolymph - not attached to skull. remains in position (inertia)

moving ampulla pushed against stationary fluid -> bending of stereocilia and alteration in rate of release of glutamate from hair cells

glutamate crosses synapse and activates neurones associated w/ hair cells, initiating propagation of action potential towards brain

358
Q

what determines the direction in which stereocilia are bent in?

A

speed and magnitude of rotational head movements

359
Q

stereocilia in the semicircular canals and neurotransmitter release

A

each hair cell receptor has one direction of maximum neurotransmitter release

stereocilia bent in this direction -> receptor cell depolarises
other direction -> hyperpolarises

360
Q

what happens when the head continuously rotates at a steady velocity?

A

duct fluid begins to move at same rate as rest of the head

stereocilia return to resting position

hair cells only stimulated by acceleration/deceleration

361
Q

what are hair cells stimulated by?

A

acceleration/deceleration

362
Q

what does damage to the semicircular canals of one side lead to?

A

nystagmus

363
Q

what is nystagmus?

A

rapid, jerky, back and forth movement of eyes

slow phase towards damaged side and rapid reset away from damaged side

364
Q

what else can cause nystagmus?

A

pouring ice cold water into external auditory meatus -> convection currents in semicircular canals

Peer teaching (10 decks)

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