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Phase 1 Med (Liv) > Neuro (summary sheets) > Flashcards

Neuro (summary sheets) 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 is the function of oligodendrocytes?

A

Myelinate axons in the brain (CNS)

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4
Q

What is the function of Schwann cells?

A

Myelinate axons in the rest of the body (PNS)

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5
Q

What is a tract (brain)?

A

Location of pathway e.g. spinothalamic tract

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6
Q

What is a commissure (brain)?

A

Tract connecting one hemisphere to the other, tracts that cross the midline

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7
Q

What is the lemnisci (brain)?

A

Narrow strip of fibres

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8
Q

What is the funiculi (brain)?

A

Rope or chord

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9
Q

What is a fasiculi (brain)?

A

Bundle e.g. gracile fasiculus

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10
Q

What is a capsule (brain)?

A

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

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11
Q

What is a column (brain)?

A

Longitudinally running fibres separates by other structures e.g. dorsal column

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12
Q

What is the cortex (brain)?

A

Laminated grey matter on outside of the brain e.g. motor cortex

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13
Q

What are the nuclei (brain)?

A

Collection of nerve cell bodies within the CNS e.g. arcuate nucleus (in the thalamus, arises from the diencephalon)

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14
Q

What are the ganglia (brain)?

A

Collection of nerve cell bodies outside the CNS i.e. in the PNS e.g. dorsal root ganglia (derived from neural crest cells) AND some inside CNS that have a capsule e.g. basal ganglia

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15
Q

What are afferents (brain)?

A

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

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16
Q

What are efferents (brain)?

A

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

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17
Q

What are reticular (brain)?

A

‘Netlike’ where grey & white matter mix e.g. reticular formation of brainstem

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18
Q

How are axons gathered?

A

Into tracts

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19
Q

Define rostral

A

Towards the nose (anterior)

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20
Q

Define caudal

A

Towards tail (posterior)

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21
Q

Define dorsal (brainstem/cord)

A

Posterior

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22
Q

Define ventral (brainstem/cord)

A

Anterior

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23
Q

Define dorsal (cerebrum)

A

Superior

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24
Q

Define ventral (cerebrum)

A

Inferior

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25
Q

Define sulci (brain)

A

Grooves

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26
Q

Define gyri (brain)

A

Ridges

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27
Q

What is the function of the frontal lobe of the brain?

A
  • Voluntary movement on opposite side of body

- Intellectual functioning, thought processes, reasoning and memory

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28
Q

What does the frontal lobe of dominant hemisphere control?

A
  • Speech (Broca’s area)

- Writing (if right handed, left side is dominant)

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29
Q

What does Broca’s area do?

A

Controls speech

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30
Q

What is the function of the parietal lobe of the brain?

A

Receives and interprets sensation (proprioception)

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31
Q

What is the function of the temporal lobe of the brain?

A
  • Understanding spoken word (Wernicke’s area)

- Memory & emotion

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32
Q

What does Wernicke’s area do?

A

Understanding spoken word

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33
Q

What is the function of the occipital lobe of the brain?

A

Understanding visual images and meaning of written words

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34
Q

What underlies the cortex of the brain?

A

The white matter

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35
Q

Where are grey matter structures found in the body?

A
  • Deep in the white matter

- Surround ventricles

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36
Q

What is the general function of the thalamus?

A

Relay centre direction inputs to cortical areas

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37
Q

What is the general function of the hypothalamus?

A

Links endocrine system to brain and involved in homeostasis

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38
Q

What is the general function and structure of the basal ganglia

A
  • Caudate nucleus, putamen & globus pallidus

- Motor control, cognition & non-motor behaviour

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39
Q

What is the striatum of the basal ganglia?

A

The caudate nucleus and putamen

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40
Q

What is the lentiform nucleus of the basal ganglia?

A

Globus pallidus and putamen

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41
Q

What is the function of the cerebellum?

A

Coordination of voluntary motor movement, balance, equilibrium and muscle tone

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42
Q

What is the structure of the cerebellum?

A

Lies over the dorsal surface of the brain stem and attached to it by 3 peduncles

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43
Q

Which peduncle joins the cerebellum and the midbrain?

A

Superior

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44
Q

Which peduncle joins the cerebellum and the pons?

A

Middle

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45
Q

Which peduncle joins the cerebellum and the medulla?

A

Inferior

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46
Q

How is the cerebellum separated from the dorsal brainstem?

A

By the 4th ventricle, which forms part of its roof

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47
Q

What is the cerebellum made of?

A

Folded cortex, white matter and deep inner nuclei

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48
Q

What does a cerebellar injury result in?

A

Movements which are slow and uncoordinated

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49
Q

What are the functions of the brainstem?

A
  • Special senses
  • Sensory & motor for head & neck via cranial nerves
  • Autonomic regulation of the body
  • Regulates consciousness
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50
Q

What is the pathway between the brain and spinal cord?

A

Brainstem

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51
Q

What are 3 components of the brainstem?

A

Midbrain, pons and medulla oblongata

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52
Q

What are the two components of the mid-brain?

A

Tectum (superior & inferior colliculi) and cerebral peduncle (tegmentum & crus cerebri)

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53
Q

What structure surrounds the cerebral aqueduct?

A

The midbrain

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54
Q

What bridges the brainstem to the cerebellum?

A

Pons

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55
Q

What is the medulla oblongata continuous with?

A

The spinal cord

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56
Q

What are the two types of specialised cell in the CNS?

A
  • Nerve cell or neurones

- Neuroglia (astrocytes, oligodendrocytes & microglia)

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57
Q

What is gastrulation?

A

Single layer blastula developing into a triple-laminar disc (gastrula)

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58
Q

Define neuraltion

A

The process of formation of the embryonic nervous system

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59
Q

What is the process of neuraltion?

A
  • Ectoderm thicks to form the neural plate in the 3rd week
  • Undergoes mitosis to form the mid-line groove (neural goove)
  • This deepens and detaches to form the neural tube
  • The presumptive neural crest cells run dorso-laterally along the neural groove
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60
Q

What cells do the neural crest cells develop to form?

A
  • Sensory (dorsal root) ganglia of the spinal cord and cranial nerves V,VII, IX &X
  • Schwann cells
  • Pigment cells
  • Adrenal medulla
  • Bony skull
  • Meninges
  • Dermis
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61
Q

What does the rostral part of the neural tube form in an adult?

A

The brain (CNS), grows faster than the caudal portion

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62
Q

What does the caudal part of the neural tube form in an adult?

A

The spinal cord

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63
Q

What are the 3 primary brain vesicles present by the 5th week of embryonic development?

A
  • Prosencephalon (forebrain)
  • Mesencephalon (midbrain)
  • Rhombencephalon (hindbrain)
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64
Q

What are the secondary brain vesicles which are present by the 7th week of embryonic development?

A
  • Prosencephalon —> Telencephalon & Diencephalon
  • Mesencephalon —>
    Mesencephalon
  • Rhombencephalon —>
    Metencephalon & Myelencephalon
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65
Q

What does the telencephalon give rise to in the mature brain?

A

Cerebral hemisphere & lateral ventricles

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66
Q

What does the diencephalon give rise to in the mature brain?

A

Thalamus, hypothalamus & third ventricle

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67
Q

What does the mesencephalon give rise to in the mature brain?

A

Midbrain (colliculi) & aqueduct

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68
Q

What does the metencephalon give rise to in the mature brain?

A

Cerebellum, pons and upper part of 4th ventricle

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69
Q

What does the myelencephalon give rise to in the mature brain?

A

Medulla oblongata & lower part of 4th ventricle

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70
Q

When does the neural tube usually close?

A

At the end of the 4th week

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71
Q

What is spina bifida?

A

Failure of the tube to close in the spinal cord

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72
Q

What is anencephalus?

A

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

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73
Q

What may cause spinal cord abnormalities?

A

Faulty induction or environmental factors, which act on the neuroepithelial cells

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74
Q

When is the eye formed in embryo?

A

3 weeks

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75
Q

When is there cerebral expansion and commissures in embryo?

A

10 weeks

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76
Q

When are the basic structures of the brain established in embryo?

A

3 months

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77
Q

When does myelination occur in embryo?

A

5 months

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78
Q

When has the lobes cerebrum formed in embryo?

A

7 months

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79
Q

When has the gyri and sulci formed in embryo?

A

9 months

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80
Q

When do abnormalities to the CNS tend to occur?

A

Dependent on time of infection - generally 2nd trimester

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81
Q

What are the basic functions of the brainstem?

A
  • Basic vital functions (breathing & heart rate)

- Delivers basic responses

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82
Q

What is the corpus callous?

A

A huge fibre bundle that connect the left and right hemispheres together

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83
Q

Which part of the brain delivers much more complex responses?

A

The cerebral cortex

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84
Q

What percentage of the basic cerebellum contains neurones?

A

70% - very high percent

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85
Q

Which part of the brain does the most complex tasks?

A

The cerebellum

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86
Q

How do all sensorimotor, cognitive and motivational/effect structures connect to the cerebellum?

A

By re-entrant loops

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87
Q

Where does the basic cerebellum receive input from?

A

The motor cortex, brain stem nuclei and sensory receptors

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88
Q

Which part of the brain modulates upper motor neurones?

A

Basic cerebellum

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89
Q

What is the structure of the cortex like?

A

Very uniform over its entire surface

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90
Q

What may damage to the cerebellum do?

A

Makes many movements inaccurate, slow & uncoordinated

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91
Q

Which part of the brain makes sure movement commands are done properly?

A

The cerebellum - other parts can issue the commands but its the cerebellum which ensures it’s done properly

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92
Q

Where in the brain is responsible for fine coordinated voluntary movement?

A

Cerebellum

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93
Q

What are the main components of the basal ganglia?

A
  • Dorsal striatum (caudate nucleus & putamen)
  • Ventral striatum (nucleus accumbens & olfactory tubercle)
  • Globus pallidus (internal and external segment)
  • Ventral pallidum
  • Substantia nigra
  • Subthalamic nucleus
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94
Q

What makes up the dorsal striatum?

A

Caudate nucleus & putamen

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95
Q

What makes up the ventral striatum?

A

Nucleus accumbens and olfactory tubercle

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96
Q

What makes up the globus pallidus?

A

Internal and external segment

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97
Q

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

A

By recurrent loops

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98
Q

What does the basal ganglia do in the sense of the competing systems in the brain?

A

Selects which one to do out of:

  • Emotions
  • Cognitions
  • Sensorimotor
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99
Q

What are the outputs of the basal ganglia like?

A

Inhibitory & tonically active (slow & continuous)

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100
Q

What is the function of the hippocampus?

A
  • Critical for episodic memory
  • Essential for the construction of mental images
  • Vital role in short term memory
  • Important for spatial memory & navigation
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101
Q

What is the hippocampus part of?

A

The limbic system

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102
Q

What is anterograde tract tracing?

A

Transport from neuronal cells bodies to axon terminals

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103
Q

What is retrograde tract tracing?

A

Transport from axonal terminals to neuronal cell bodies

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104
Q

How can an increase in neural activity be detected by lumbar puncture?

A
  • Results in the increase in the release of neurotransmitter
  • More breakdown product
  • Detected in CSF by lumbar puncture
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105
Q

How can an increase in neural activity be detected by imaging techniques?

A
  • More active regions require more oxygen
  • So require more blood
  • Imaging can detect haemodynamic changes
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106
Q

What can a EEG detect?

A

Gives an indication of regional brain activity underlying electrodes

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107
Q

What is the basic cellular unit of the nervous system?

A

Neurones

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108
Q

How can neurones be adapted?

A

They are specialised for different functions

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109
Q

What are the basic components of all neurones?

A
  • Dendrites
  • Cell body/soma
  • Axon
  • Presynaptic terminal
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110
Q

What are the functions of the neurones?

A
  • Receive information via dendrites which transmit to the cell body (soma)
  • Transmit information via axons and action potentials are propagated from the axon hillock
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111
Q

What are neurones stained with H&E?

A
  • Haemotoxylin stains the nuclei acids blue

- Eosin satins the proteins red

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112
Q

What can stain myelin?

A

Luxor fast blue (LFB)

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113
Q

What can stain RER in the neurones?

A

Cresol violet (CV)

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114
Q

Define neural plasticity

A

The basis of learning and memory

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115
Q

What is an early marker of Alzheimer’s?

A

The loss of dendritic spines

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116
Q

What are the three functional classes that neurones can be divided into?

A
  • Afferent (sensory)
  • Efferent (motor)
  • Interneurons (within the CNS)
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117
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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118
Q

What is a nerve fibre?

A

A single axon

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119
Q

What is a nerve?

A

A bundle of axons (fibres) bound together by connective tissue

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120
Q

Where do afferent neurones convey information to?

A

From the tissues to organs TOWARDS the CNS

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121
Q

What do afferent neurones have at their peripheral ends?

A

Furthest from the CNS, afferent neurones have sensory receptors

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122
Q

What happens at the ends of afferent neurones?

A

The sensory receptors respond to various physical or chemical changes in their environment by generating electrical signals in the neurone

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123
Q

How do the axons of the afferent neurones divide?

A
  • The peripheral process begins where the dendritic branches converge from the receptor ends
  • The central process enters the CNS to form junctions with other neurones
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124
Q

What is the only part of the afferent neurone which enters the CNS?

A

The central process. The cell body & long axon (peripheral process) are outside the CNS

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125
Q

Where do efferent neurones convey information to?

A

Away from the CNS to effector cells such as muscle, gland or other cell types

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126
Q

Which part of efferent neurones are present within the CNS?

A
  • Cell bodies and dendrites are within the CNS

- The axons extend out to the periphery

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127
Q

What is the function of interneurones?

A

Connect neurones within the CNS - form the majority of neurones

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128
Q

Which parts of the interneurones lie within the CNS?

A

They lie entirely within the CNS

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129
Q

What do sheaths of myelin usually consist of?

A

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

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130
Q

What does the myelin compromise of?

A

70% lipid & 30% protein

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131
Q

What are the myelin-forming cells of the CNS?

A

Oligodendrocytes - each one of these may branch to form meylin on as many as 40 axons

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132
Q

What are the myelin-forming cells of the PNS?

A

Schwann cells - they form individual myelin sheaths surrounding segments at regular intervals along the axons

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133
Q

What are nodes of Ranvier?

A

The spaces between adjacent sections of myelin where the axons’ plasma membrane is exposed to extracellular fluid

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134
Q

What is a function of myelin?

A

Increases the speed of conduction along the axons

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135
Q

Where are myelinated axons usually found?

A

In the somatic nerves - they are thicker

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136
Q

Where are unmyelinated axons usually found?

A

In the post-ganglionic autonomic fibres, fine sensory fibres, olfactory neurones and interneurones

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137
Q

What are the two cell types in the CNS?

A

Neurones and glial cells

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138
Q

What is the function of glial cells?

A

Surround the cell body, axon and dendrites of the neurones and provide them with physical and metabolic support

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139
Q

What are the 5 types of glial cells?

A
  • Oligodendrocytes
  • Schwann cells
  • Astrocytes
  • Microglia
  • Ependymal cells
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140
Q

What is the function of oligodendrocytes?

A
  • Glial cells of the CNS
  • Myelinating cells for rapid nerve conduction
  • Provides metabolic support for axons and transports metabolic products directly into axons
  • Myelinate multiple axons
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141
Q

What is the function of Schwann cells?

A
  • Glial cells of the PNS
  • Myelinating cells
  • Myelinate single axons
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142
Q

What is the function of astrocytes?

A

Help regulate the composition of the extracellular fluid in the CNS by removing K ions and neurotransmitters around synapses

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143
Q

What is the astrocytes function with glutamate?

A

Astrocytes take it up, covert it into glutamine and release it, then neurones can take it up ad convert it back to glutamate for reuse

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144
Q

What is the astrocytes function with the formation of tight junctions?

A
  • They stimulate this between the walls of the capillaries found in the CNS - this forms the blood-brain barrier
  • This is done by foot processes closely applied around capillaries
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145
Q

How do astrocytes sustain the neurones metabolically?

A

By providing glucose and removing ammonia

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146
Q

What is the structure of astrocytes?

A

Star-like cells

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147
Q

What are the most numerous glial cells in the CNS?

A

Astrocytes

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148
Q

Where are protoplasmic astrocytes found?

A

In grey matter

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149
Q

Where are fibrous astrocytes found?

A

In white matter

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150
Q

What are radial glia?

A

Crucial in guiding developing neurones - these are only developmental and aren’t found in the adult brain

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151
Q

What are Muller glia?

A

Specialised radial glia of the retina

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152
Q

What are Bergmann glia?

A

Found in the cerebellum, support Purkinje cell dendrites and synapses

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153
Q

What is the structure of microglia?

A

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

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154
Q

What are microglia derived from?

A

Progenitors that migrate into the CNS from the periphery

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155
Q

Which glial cell is proliferative at injury?

A

Microglia

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156
Q

What is the structure of microglia in the cortical grey matter?

A

They are more ramified (branched)

157
Q

Which glial cell is phagocytotic?

A

Microglia

158
Q

Which glial cells contributes to synaptic plasticity?

A

Microglia

159
Q

Where are ependymal cells found?

A

Line the fluid-filled cavities within the brain (ventricles) and spinal cord

160
Q

What is the structure of ependymal cells?

A

Have cilia, microvilli and desmosomes

161
Q

What are the functions of the ependymal cells?

A
  • Regulate the production and flow of CSF

- Provides a barrier between CSF and brain

162
Q

What is the blood-brain barrier formed by?

A

Endothelial cells, pericytes and 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 blood-brain barrier?

A
  • Endothelial tight junctions
  • Astrocyte end feet
  • Pericytes
  • Continuous basement membrane (lacks fenestrations)
  • Requires specific transported for glucose, essential ions etc.
165
Q

What are circumventrular organs?

A

Parts of the brain which lack the blood-brain barrier e.g. posterior pituitary

166
Q

Why may some parts of the brain lack the blood-brain barrier?

A

Need to be in contact with the blood for a sensory role to monitor

167
Q

Where does the CSF circulate?

A
  • In the subarachnoid space (around the brain and spinal cord)
  • Within the ventricles
168
Q

What is the main function of CSF?

A

Offers protection by cushioning brain from gentle movements

169
Q

What are the four ventricles of the brain?

A
  • Lateral (paired)
  • III
  • IV
170
Q

How do ventricles and subarachnoid spaces connect?

A

Via cisterns

171
Q

What is the normal volume of CSF?

A

120ml

172
Q

What is the appearance/structure of CSF?

A

A clear, colourless liquid which contains: protein, urea, glucose & salts

173
Q

Where is CSF mainly produced?

A

By the ependymal cells in the choroid plexuses of the lateral ventricles

174
Q

What is the choroid plexus formed from and what does it form around?

A
  • Formed from modified ependymal cells

- They from around a network of capillaries, large surface area

175
Q

How is CSF absorbed?

A

By arachnoid granulations (villi) e.g. in the superior sagittal sinus

176
Q

What is hydrocephalus and what is it caused by?

A
  • Abnormal accumulation of CSF in ventricular system

- Often due to a blocked cerebral aqueduct

177
Q

What does hydrocephalus cause in adults?

A

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

178
Q

What is the resting membrane potential?

A

When the inside of the cell of the neurone is negatively charged compared to the outside

179
Q

What is the typical resting potential?

A

-70mV

180
Q

How is the resting membrane potential met?

A
  • The Na/K ATPase pump in the membrane develop conc. gradients by pumping 3 Na out for every 2 K in (by active transport)
  • Na is concentrated outside axon while K is inside
  • Very few Na gated channels are open, meaning small diffusion of Na back in
  • However, leak K channels are open, resulting in K diffusing out the axon, making inside more negative than outside
181
Q

What is the process of the changes in action potential?

A
  • A neurotransmitter binds to specific ligand-gated ion channels, on post synaptic membrane, Na ions enter neurone
  • This inflow allows the inside of the neurone to become more +ve - initial depolarisation
  • This stimulates the opening of some voltage-gated Na channels, resulting in further entry & depolarisation
  • When the membrane reaches the critical threshold potential, depolarisation becomes a +ve feedback loop of Na entry
  • At around 30mV, the channels are closed and the influx stops
  • The K diffuses out the neurone by voltage gated K channels down a conc. gradient, causing repolarisation
  • Once it reaches a -ve potential, it causes the channels to close
182
Q

What is the critical threshold potential?

A

Around -55mV

183
Q

When does an absolute refractory period occur?

A

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

184
Q

What follows the absolute refractory period?

A

The relative refractory period

185
Q

What happens in the relative refractory period?

A

Where a second action potential can be produced - but only if the stimulus strength is considerably greater than usual

186
Q

What is the purpose of the refractory period?

A
  • Limit the number of action potentials an excitable membrane can produce in a given period of time
  • They allow action potentials to be separated so that individual electrical signals are able to pass down the axon
187
Q

What causes current to flow in the neurone membrane?

A
  • The generation of an action potential at particular segment on the neurone
  • This is due to the difference in potential between the dopalirsed membrane and adjacent segements at resting potential
188
Q

What does the propagation speeds along a membrane depend on?

A
  • Fibre diameter

- Myelination

189
Q

How does the fibre diameter determine the speed of transport along the membrane?

A

The larger the diameter, the faster the action potential propagates

190
Q

How does myelination determine the speed of transport along the membrane?

A

Increases propagation speeds, as action potentials only occur at the nodes of Ranvier

191
Q

What is saltatory conduction?

A

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

192
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 post synaptic neurone

193
Q

What happens at an excitatory synapse?

A

The membrane potential of a postsynaptic neurone is brought closer to threshold

194
Q

What happens at an inhibitory synapse?

A

The membrane potential of a postsynaptic neurone is either driven further from threshold or stabilised at its resting potential

195
Q

What are the two types of synapse?

A

Electrical and chemical

196
Q

How are the presynaptic and postsynaptic cells joined in an electrical synapse?

A

By gap junctions

197
Q

How does conduction occur in a electrical synapse?

A
  • Local currents arriving from action potentials flow directly across the junction through the connecting channels
  • This depolarises the membrane of the second neurone to threshold
198
Q

Is the communication at electrical synapses quick?

A

Extremely rapid

199
Q

Which synapses allow for synchronised transmission?

A

Electrical

200
Q

Where are electrical synapses found?

A

In brainstem neurones e.g. breathing & hypothalamus, hormone secretion

201
Q

How are the presynaptic and postsynaptic neurones joined in a chemical synapse?

A

Joined by the synaptic cleft

202
Q

How is direct propagation prevented in a chemical synapse?

A

By the synaptic cleft

203
Q

How does the presynaptic vesicle look like as it has received an action potential?

A

Ends in a slight swelling at the axon terminal, which holds the synaptic vesicles

204
Q

How are signals transmitted across the synaptic cleft in a chemical synapse?

A

By a chemical messenger - neurotransmitter - which is released by the presynaptic axon terminal

205
Q

What is a cotransmitter?

A

When there is more than one neurotransmitter simultaneously released from an axon

206
Q

What are chemical synapses covered by and why is this important?

A
  • Covered by astrocytes (glial cells)

- Essential for the reuptake of excess neurotransmitter

207
Q

What is the process of neurotransmitter release?

A
  • Ca ion channels open when an action potential reaches the pre-synaptic terminal
    • Ca ions cause vesicles to move to release sites and fuse with the presynaptic cell membrane and discharge their contents
    • Neurotransmitter diffuses across the synaptic cleft and attaches to receptor sites on the post-synaptic membrane
208
Q

What does a higher concentration of neurotransmitter release mean?

A

The more likely there will be binding to receptor and thus action potential propagation

209
Q

What are the 5 processes of synaptic transmission?

A
  • Manufacture
  • Storage
  • Release
  • Interact with post-synaptic receptors
  • Inactivation
210
Q

On what system do drugs of the brain work on?

A

The 5 processes of synaptic transmission

211
Q

What is the neurotransmitter used in the brain & neuromuscular junction?

A

Acetylcholine

212
Q

What are the 2 main acetylcholine receptors?

A

Muscarinic & nicotinic

213
Q

What happens once acetylcholine has been bound to the post-synaptic receptor?

A
  • The enzyme, acetylcholine esterase, breaks it down into choline & acetyl
  • The choline can then be reabsorbed by the presynaptic neurone to make more acetylcholine
214
Q

What is the effect when neurotransmitters bind to excitatory channels?

A

Depolarisation will occur - many Na leave and few K enter

215
Q

What is the effect when neurotransmitters bind the inhibitory channels?

A

Hyperpolarisation will occur - many K leave OR many Cl enter

216
Q

What happens once a neurotransmitter has bound?

A

Results in propagation of action potentials (if excitatory)

217
Q

What is temporal summation?

A

Input signals arrive from the sam presynaptic cell at different times. These summate since there are a greater number of open ion channels and thus a greater flow of positive ions

218
Q

What is spatial summation?

A

Where two inputs occur at different locations in the postsynaptic neurone

219
Q

What is the function of spatial and temporal summation?

A

Increases the inward flow of +ve ions and bring the postsynaptic membrane to threshold so action potentials are initiated

220
Q

When are unbound neurotransmitters removed from the synaptic cleft?

A
  • They are actively transported back into the presynaptic axon terminal or by near glial cells
  • Diffuse away from receptor site
  • Are enzymatically transformed into inactive substances, some are transported back into the presynaptic neurone for reuse
221
Q

What are fast neurotransmitters?

A

Short lasting effects, tend to be involved in rapid communication

222
Q

Give 3 examples of fast neurotransmitters

A
  • Acetylcholine
  • Glutamate (excitatory)
  • GABA (inhibitory)
223
Q

What are neuromodulators?

A
  • Cause change in synaptic membrane that last longer times

- Associated with slower events such as learning, development, motivational states

224
Q

Give 3 examples of neuromodulators

A
  • Dopamine
  • Noradrenaline
  • Serotonin
225
Q

How do local anaesthetics work?

A
  • Interput axonal transmission

- They block sodium channels preventing neurones from depolarising - no action potential

226
Q

What is the major neurotransmitter of the PNS at the neuromuscular junction?

A

Acetylcholine (also used in brain & spinal cord)

227
Q

What are cholinergic neurones?

A

Neurones which release ACh

228
Q

What is acetylcholine synthesise from?

A

Choline (common nutrient in food) & acetyl choline A, stored in synaptic vesicles

229
Q

What is the function of acetylcholinesterase?

A

Rapidly destroys ACh, releasing choline & acetate. The choline is transported back to the presynaptic neurone to be reused

230
Q

What are the two general types of ACh receptors?

A

Nicotinic & muscarinic

231
Q

What is the receptor in a nicotinic receptor?

A

An ion channel

232
Q

What do nicotinic receptors respond too?

A

ACh & nicotine

233
Q

Where are nicotinic receptors found?

A

The neuromuscular junction

234
Q

Why are nicotinic receptors important in the brain?

A

They are important in cognitive functions and behaviour

235
Q

Why are tobacco products so addictive?

A

Due to the presence of nicotinic receptors on presynaptic terminals in reward pathways of the brain

236
Q

What do muscarinic receptors respond too?

A

ACh and the mushroom poison muscarine

237
Q

Where are muscarinic receptors present?

A

In the brain and at junctions where a major division of the PNS innervates peripheral glands & organs

238
Q

Where is noradrenaline the main neurotransmitter?

A

In the peripheral heart and central nervous systems

239
Q

How is noradrenaline affected by antidepressants?

A
  • Blocks the reuptake of noradrenaline

- Increases the amount of noradrenaline by inhibiting the enzyme which breaks it down

240
Q

How do stimulates affect noradrenaline?

A

Increases release and blocks uptake

241
Q

Which neurotransmitter is important in the basal ganglia?

A

Dopamine

242
Q

How is dopamine affected by antipsychotic drugs?

A

Blocks receptor so other neurotransmitter can’t activate receptor

243
Q

How is dopamine affected by stimulants?

A

Increases release and blocks reuptake

244
Q

How is dopamine affected by anti-parkinsons drugs?

A

Increases dopamine manufacture

245
Q

What is the effect of serotonin?

A

Has an excitatory effect on pathways that mediate sensations

246
Q

How is serotonin affected by antidepressants?

A

Results in an increase in conc. of synaptic serotonin

247
Q

How is serotonin affected by ecstasy?

A

Neurotoxic - destroys the terminal of axons

248
Q

What is the main excitatory neurotransmitter?

A

Glutamate

249
Q

What is the main inhibitory neurotransmitter?

A

GABA

250
Q

What is the normal hearing range?

A

20 - 20,000 Hz

251
Q

What is the function of the outer ear?

A

Helps collect sound

252
Q

What is the function of the middle ear?

A

Transmission of sound

253
Q

What is the function of the inner ear?

A

The conversion of sound into neural impulses

254
Q

How is sound transmitted in the external ear?

A
  • Enters through the pinna/auricle (exterior of ear)
  • Enters ear via external auditory canal
  • Makes its way through the canal to the tympanic membrane
  • As air molecules push against the membrane, it causes the tympanic membrane to vibrate at the same frequency
255
Q

What can help amplify and direct sound in the outer ear?

A

The shape of the pinna and external auditory canal

256
Q

What is the pattern of vibration of the tympanic membrane at different frequencies?

A
  • Vibrates slowly to low frequency sounds

- Vibrates very rapidly to high frequency sounds

257
Q

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

A

The tympanic membrane

258
Q

What is the middle ear?

A

An air-filled cavity in the temporal bone of the skull

259
Q

What is sensation of the middle ear provided by?

A

The glossopharyngeal nerve (CN9)

260
Q

What are the pressures in the external auditory canal and middle ear canal?

A

Normally equal to atmospheric pressure

261
Q

How is the middle ear exposed to atmospheric pressure?

A

By the Eustachian tube

262
Q

How is the middle ear connected to the pharynx?

A

By the Eustachian tube

263
Q

How does the Eustachian tube open into the pharynx?

A

Through a slit-like opening which is normally closed

264
Q

What causes the opening of the Eustachian tube into the pharynx to open?

A

Muscle movements e.g. swallowing, yawning or sneezing

265
Q

What causes a difference in pressure between the middle and external ear?

A

Changes in altitude

266
Q

What happens once the pressure outside the ear and in the external auditory meatus change?

A
  • The middle ear initially remains constant as the Eustachian tube is closed
  • The constant pressure can stretch the tympanic membrane to stretch
267
Q

How can the pain of the tympanic membrane due to pressure changes be relived?

A
  • By yawning/swallowing
  • Allows the opening of the Eustachian tube
  • Allows pressure in the middle ear to equilibrate with the external atmospheric pressure
268
Q

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

A

Through a moveable chain of three bones (ossicles)

269
Q

What is the order of the ossicles which the vibrations have to travel through?

A

Malleus, incus and stapes

270
Q

What is the joint between the ossicle bones?

A

Synovial

271
Q

What are the functions of the ossicles?

A

To couple the total vibrations of the tympanic membrane to the oval window

272
Q

What is the oval window?

A

A membrane covered opening between the middle and inner ear

273
Q

Why is it useful that the oval window is much smaller than the tympanic membrane?

A

To ensure a greater force per area, which is needed to adequately transmit the sound energy through the fluid filled cochlea

274
Q

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

A

By the contraction of two small muscles of the middle ear (the tensor tympani and stapedius)

275
Q

Which nerve innervates the contraction of tensor tympani?

A

The mandibular branch of trigeminal nerve (CN5)

276
Q

Which nerve innervates the contraction of stapedius?

A

Facial nerve (CN7)

277
Q

Where does the tensor tympani muscle attach to?

A

The malleus

278
Q

What does contraction of tensor tympani do?

A

Dampens the movement of malleus

279
Q

What does the stapedius attach to?

A

The stapes

280
Q

What do tensor tympani and stapedius reflexively act to and why?

A
  • Continuous loud noise

- To protect the delicate receptor apparatus in the inner ear

281
Q

What can’t the sensory tympani and stapedius protect against?

A

Sudden intermittent loud sounds

282
Q

What is the inner ear?

A

The cochlea

283
Q

What is the organ of hearing?

A

Cochlea

284
Q

What is the cochlea?

A

A spiral-shaped, fluid filled space in the temporal bone

285
Q

How is the cochlea divided?

A

Almost completely lengthwise by a membranous tube (cochlear duct)

286
Q

Where are the sensory receptors of the auditory system found?

A

The cochlear duct of the cochlea

287
Q

What is the cochlea duct filled with?

A

Endolymph - a compartment of extracellular fluid containing high K and low Na

288
Q

What is the structure of endolymph similar to?

A

Intracellular fluid

289
Q

What is either side of the cochlear duct filled with?

A

Perilymph

290
Q

What is the structure of perilymph similar to?

A

Cerebrospinal fluid (CSF)

291
Q

Where is the Scala vestibuli located?

A
  • Above the cochlear duct
  • Begins at the oval ducts
  • Forms the entrance to the inner ear from the oval window
292
Q

Where is the Scala tympani located?

A
  • Below the cochlear duct

- Connects to the middle ear via a second-membrane covered opening, the round window

293
Q

At which point do the Scala vestibuli. and tympani become continuous?

A

At the far end of the cochlear duct (the helicotrema)

294
Q

What do sound waves from the external acoustic channel cause the tympanic membrane to do?

A

Move in and out which in turn is transmitted to ossicles, which transmit this to the oval window

295
Q

What do the sound waves at the oval window cause?

A

Causes the oval window to move in and out of the Scala vestibuli. This movement causes waves of pressure at the Scala vestibuli

296
Q

What do the waves of pressure in the Scala vestibuli cause?

A
  • They are transmitted across the cochlear duct with some being transmitted toward the helicotrema
  • Goes into the Scala tympani where pressure is relieved by the movements of the membrane of the round window
297
Q

What is the side of the cochlear duct closest to the Scala tympani formed by and what sits in it?

A
  • Formed by the basilar membrane

- Organ of corti sits inside it

298
Q

What does the organ of Corti contain?

A
  • The ear’s sensitive receptor cells

- Pressure difference across the duct membrane to vibrate

299
Q

What is the structure of the base of the basilar membrane of the ear and why is this significant?

A
  • Is narrow & stiff

- Sensitive to high frequencies

300
Q

What is the structure of the apex of the basilar membrane of the ear and why is this important?

A
  • Is wider & less stiff

- Sensitive to low frequencies

301
Q

What are the hair cells of the organ of corti?

A

The receptor cells of the organ of corti

302
Q

What are the functions of tue hair cells of the organ of Corti?

A

They are mechanoreceptors which have hair-like stereo-cilia protruding from one end

303
Q

What can damage the sterocilia of hair cells?

A

Antibiotics

304
Q

What is the anatomical groups of the hair cells of the Organ of Corti?

A
  • A single row of inner hair cells

- 4-5 rows of outer hair cells

305
Q

Where do the stereocilia of the inner hair cells extend into and what are their functions?

A
  • The endolymph fluid

- They convert pressure waves caused by the movement of fluid in the cochlear duct into receptor potentials

306
Q

Where do the stereocilia of the outer hair cells extend into and what are their functions?

A
  • Embedded in the overlying tectorial membrane

- Mechanically alter its movement to sharpen frequency tuning at each point along the basilar membrane

307
Q

What is the tectorial membrane and what is its function?

A
  • It overlies the organ of Corti in the ear
  • As the pressure waves displace the basilar membrane, the hair cells move in relation to the stationary tectorial membrane resulting in the bending of the stereocilia
308
Q

What happens when the stereo cilia bends towards the tallest member of the bundle?

A
  • Fibrous connections pull open the mechanically gated K+ channels
  • Results in an influx of K+ from the surrounding endolymph
  • Depolarises the membranes
309
Q

What happens after the membrane which holds the stereocilia (hair cell) is depolarised?

A
  • Triggers the opening of voltage-gated Ca ions

- Triggers the release of neurotransmitter

310
Q

What happens when the stereocilia are bent in the opposite way to ‘usual’?

A

This closes the channels (K) which allows the cell to rapidly repolarise

311
Q

What is the neurotransmitter of the hair cells?

A
  • Glutamate

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

312
Q

What happens as the sound waves vibrate the basilar membrane?

A
  • The stereocilia are bent back and forth
  • The membrane potential of the hair cells rapidly oscillates
  • Bursts of glutamate are released on the afferent neurones
313
Q

What do the bursts of glutamate from the sound waves vibrating on the basilar membrane do?

A
  • Generation of action potentials in the neurones

- The axons join the cochlear branch of the vestibulocochlear nerve (CN8)

314
Q

What does a greater energy (loudness) of a sound wave cause?

A

A greater frequency of action potentials generated in the afferent nerve fibres

315
Q

Why do each hair cell respond to a limited range of sound frequencies?

A
  • Due to its position on the basilar membrane

- One particular frequency stimulates it the most strongly

316
Q

Where do cochlear nerve fibres make dendritic contact with the hair cells of the organ of Corti?

A
  • Within the cochlear duct

- The cell bodies of these fibres lie within the cochlea and are collectively called the spiral ganglion

317
Q

What are the spiral ganglion?

A

The cell bodies of the cochlear nerve which lie within the cochlea

318
Q

At what level does the cochlear nerve join the brainstem?

A

At the level of the rostral medulla

319
Q

What happens to the fibre of the cochlear nerve once they have met the rostral medulla?

A
  • They bifurcate (split into 2)

- End in the dorsal and ventral cochlear nuclei

320
Q

Where do the dorsal and ventral cochlear nuclei lie close too?

A

The inferior cerebellar peduncle

321
Q

What happens to the cochlear nerve fibres after the cochlear nuclei?

A
  • The second-order neurones ascend into the pons

- The fibres travel to the superior olivary nucleus

322
Q

Where does the superior olivary nucleus travel to?

A
  • Fibres leave the brainstem in the vestibulocochlear nerve and end in the organ of corti
  • Some also travel to the inferior colliculus of the midbrain
323
Q

What is the function of the fibres of the superior olivary nucleus in the ear?

A
  • Have an inhibitor function
  • Adjust transmission of auditory information through the cochlear nerve by mediating contractions of the tensor tympani and stapedius in response to loud noises
324
Q

What happens to the superior olivary nucleus fibres once they are in the inferior colliculus of the midbrain?

A

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

325
Q

Where do the nerve fibres of the superior olivary nucleus travel to from the medial geniculate body of the thalamus?

A
  • Travel through the internal capsule

- Goes to the primary auditory cortex of the temporal lobe

326
Q

Where is the primary auditory cortex located?

A

Situated on the dorsal surface of the superior temporal gyrus

327
Q

What is the region of the temporal lobe which surrounds the primary auditory cortex?

A

Wernicke’s area

328
Q

What is the function of Wernicke’s area?

A
  • Where auditory information is interpreted and understood

- Also important in the processing of language in the brain

329
Q

Where is Wernicke’s area located?

A

The superior temporal lobe

330
Q

What will happen in a patient if Wernicke’s area is damaged?

A
  • Unable to understand questions

- Speech will be incomprehensible

331
Q

Summarise the path of the cochlear branch of the vestibulocochlear nerve (CN8)

A
  • Cochlear nuclei
  • Superior olivary nucleus
  • Inferior colliculus
  • Medial geniculate body - via the inferior brachium (nerve)
  • Primary auditory cortex, in Wernicke’s area
332
Q

Which parts of the colliculus and geniculate body are used for auditory information?

A
  • Inferior colliculus
  • Medial geniculate body
  • I’MAuditory (way to remember)
333
Q

Which parts of the colliculus and geniculate body are used for auditory information?

A
  • Superior colliculus

- Lateral geniculate body

334
Q

What is the simplified pathway of chords tympani (branch of facial nerve CN7)?

A

Conveys taste information from the tongue and runs through the middle ear to carry taste messages to the brain

335
Q

How does inflammation of the facial nerve (CN7) potentially cause pain behind the ear?

A

It exits the cranial cavity into the internal acoustic meatus behind the cochlea

336
Q

What type of cell can also be found in the vestibular apparatus of the inner ear?

A

Hair cells

337
Q

What is the vestibular apparatus?

A

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

338
Q

What is the function of the hair cells in the vestibular apparatus of the inner ear?

A

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

339
Q

What does the vestibule apparatus consist of?

A
  • Three membranous semicircular canals

- Two sack-like swellings (utricle & saccule)

340
Q

Where does the vestibule apparatus lie?

A

In the temporal bone on the side of the head

341
Q

What is the function of the semi-circular canals?

A
  • Detect angular acceleration during the rotation of the head along three perpendicular axes
342
Q

When do the semicircular canals detect angular acceleration?

A
  • When nodding the head up and down
  • Shaking the head from side to side
  • Tipping the head so the the ear touches the shoulder
343
Q

What do the receptor cells of the semicircular canals contain?

A

Stereocilia

344
Q

Where are the stereocilia encapsulated in the semicircular canals?

A
  • Within the capula, a gelatinous mass

- This extends across the lumen of each semicircular canal at the ampulla

345
Q

Wha happens to the semicircular canal when the head moves?

A
  • The attached bodies of the hair cells all move with it
346
Q

What happens to the endolymph (fluid) filling the duct when the head moves?

A
  • It is not attached to the skull

- Due to inertia (staying in the same place), remains in its original position

347
Q

What happens to the ampulla when the head moves and what does this cause?

A
  • The moving ampulla is pushed against the stationary fluid
  • This causes bending of the stereocilia
  • This causes an alteration in the rate of release of glutamate from the hair cells
348
Q

What happens to glutamate after it is released from the hair cells after the movement of the head?

A
  • Crosses the synapse and activates neurones associated with the hair cells
  • This initiates the propagation of action potential towards the brain
349
Q

What determines the direction the stereocilia are bent and which hair cells are stimulated?

A

The speed and magnitude of rotational head movements

350
Q

What can vary the glutamate release from the hair cells compared to at rest?

A
  • At rest glutamate is released
  • An increase in release occurs if there is bending of the stereocilia towards the largest hair
  • A decrease in release occurs if there is being of the stereocilia away from the largest hair
351
Q

How are hair cells of the ear depolarised?

A
  • Has one direction of maximum neurotransmitter release
  • When stereocilia are bent in that direction, the receptor cell depolarises
  • When the stereocilia are bent in the opposite direction, the cell hyperpolarises
352
Q

What happens to endolymph when the head continuously rotates at a steady velocity?

A
  • The endolymph begins to move at the same rate at the rest of the head
  • Stereocilia slowly return to resting position
  • Hair cells are only stimulated during acceleration or deceleration
353
Q

What are the otolithic organs?

A

The utricle and saccule

354
Q

What is the function of the utricle and saccule?

A

Provide information about linear acceleration of the head, and about the changes in head position in relation to gravity

355
Q

What is the position of the hair cells in the utricle and what do they respond to?

A
  • Point nearly straight up when standing
  • Respond when the head is tipped away from the horizontal plane
  • Also respond to linear accelerations in the horizontal plane
356
Q

What is the position of the hair cells of the saccule and what do they respond to?

A
  • Project at right angles to those of the utricle
  • They respond when moving away from lying to a standing position
  • They also respond to vertical accelerations (e.g. jumping on trampoline)
357
Q

What are stereocilia projecting from the hair cells covered by?

A

A gelatinous substance in which tiny stones (otoliths) are embedded

358
Q

Where do the stereocilia project in the vestibular system?

A

The otolithic membrane

359
Q

What are otoliths?

A

Calcium carbonate crystals which make the gelatinous substance heavier than that of the surrounding endolymph

360
Q

What response does the gelatinous otolithic material do in response to a change in position?

A
  • Moves according to the forces of gravity
  • Pulls against the hair cells so that the stereocilia on the hair cells bend
  • The receptor cells are stimulated
  • The action potential is propagated via the vestibular nerve (branch of vestibulocochlear nerve - CN8)
361
Q

What are the uses of vestibular information?

A
  • Control of eye muscles so if head moves, the eyes can remain fixed
  • Reflex mechanisms of maintaining upright posture and balance
  • Conscious awareness of the position & acceleration of the body (proprioception)
362
Q

What is proprioception?

A
  • Conscious awareness of the position
  • Acceleration of the body
  • Perception of the space surrounding the body
  • Memory of spatial information
363
Q

Where do the central processes of the vestibular fibres mostly end?

A

In the vestibular nuclei of the rostral medulla

364
Q

What are the three coats of the eye?

A
  • Outer
  • Middle (uvea)
  • Inner
365
Q

What are present in the outer layers of the eye?

A

Cornea & sclera

366
Q

What are the two main functions of the cornea?

A
  • Transmission of light

- Refraction

367
Q

Name two things that the cornea must be

A
  • Transparent

- Have a smooth spherical surface

368
Q

What is significant of the dehydrate endothelium of the cornea?

A

Doesn’t repair

369
Q

What is the innermost layer of the cornea?

A

Dehydrate endothelium

370
Q

What is the function of the dehydrate endothelium of the cornea?

A

Maintain corneal clarity by plumping water out (since water molecules alter the regular spacing between collagen fibres & cause opacity)

371
Q

What is significant about the surface epithelium of the cornea?

A

Capable of repair - many layers that slough off and are constantly regenerated

372
Q

What is the outer layer of the eye (and cornea)?

A

The surface epithelium

373
Q

What is the sclera of the eye?

A

Forms the white capsule around the eye, except at its anterior surface where it is specialised into the clear cornea

374
Q

What is the function of the sclera?

A
  • Offers protection; formed of a tough outer layer of collagen
  • Serves as an insertion point for the external muscles of the eye
375
Q

Which part of the eye is a continuation of the dura matter and cornea?

A

The sclera

376
Q

What does the middle (uvea) of the eye consist of?

A
  • Iris
  • Ciliary body
  • Choroid
377
Q

Which part of the eye is a specialised section of choroid?

A

Iris

378
Q

What is the function of the iris?

A

Contains & controls the size of the pupil - which lets light in

379
Q

What makes the pupil smaller and what system does so?

A
  • Sphincter muscles (circular fibres)

- Parasympathetic

380
Q

What makes the pupil larger and what system does so?

A
  • Dilator muscles (radial fibres)

- Sympathetic

381
Q

Which part of the eye is coloured?

A

Iris

382
Q

What is the epithelium of the ciliary body of the eye and what does it produce?

A
  • Glandular epithelium

- Produces aqueous humour & nutrients for cornea/lens

383
Q

What is aqueous humour?

A
  • Mainly water and electrolytes
  • Located in the anterior chamber
  • Important in maintaining intraocular pressure
384
Q

What is the ciliary body made of?

A

Smooth muscle

385
Q

What is the function of the ciliary body?

A

Controls accommodation; the adjustment of the lens in the eye so that clear images of objects at different distances are formed on the retina

386
Q

Where does the ciliary body receive innervation from?

A

The parasympathetic system

387
Q

What is the choroid important for?

A

The nutrition of the outer retina (photoreceptors)

388
Q

What are the components of the inner of the eye?

A
  • Retina

- Tear film

Phase 1 Med (Liv) (13 decks)

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