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Life Cycle and Reproduction Systems (LCRS) > Neurology > Flashcards

Neurology Flashcards

1
Q

What are the two branches of the PNS?

A

The somatic PNS, which controls motor and sensory functions for the body wall, e.g. skin (sensory neurones) and skeletal muscles (motor neurones).
The autonomic nervous system, which regulates function of the viscera. It has sympathetic and parasympathetic arms.

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2
Q

What do the different lobes of the brain, cerebellum and brainstem do?

A

The frontal lobe is responsible for personality and conscious thought.
The parietal lobe contains the somatosensory cortex.
The occipital lobe contains the visual cortex.
The temporal lobe has auditory functions, as well as where anxieties are formed.
The cerebellum is responsible for fine motor skills
Brain-stem = breathing, HR, BP etc.

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3
Q

What is the corpus collosum?

A

A nerve tract in the centre of the brain allowing communication between the right and left hemispheres.

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4
Q

What are the meninges?

A

A thick covering over the outside of the brain comprising 3 layers: dura mater, arachnoid mater and pia mater.

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5
Q

Describe the basic structure of spinal nerves.

A

They contain both afferent and efferent axons (each surrounded by endoneurium), which are bundled into fascicles surrounded by perineurium. The whole nerve is in a tough epineurium capsule.

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6
Q

Name the 12 cranial nerves.

A

Olfactory ooh
Optic ooh
Oculomotor ooh
Trochlear to
Trigeminal touch
Abducens and
Facial feel
Vestibulocochlear very
Glossopharyngeal good
Vagus velvet
(Spinal) Accessory such
Hypoglossal heaven.

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7
Q

Describe the structure of the region around the nodes of Ranvier.

A

The nodes themselves have sodium ion channels. The region which immediately neighbours this is called the paranode and is where the myelin attaches to the axon. The juxtaparanode has a high density of potassium ion channels.

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8
Q

What are the 3 types of synapse?

A

Axo-dendritic (often excitatory)
Axo-somatic (often inhibitory)
Axo-axonic (often modulatory)

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9
Q

What are the four neuronal shapes, and examples for each?

A

Pseudounipolar (dorsal root ganglion cells)
Bipolar (retinal bipolar cells)
Golgi type I multipolar ((highly branches dendritic trees with long axon)) (pyramidal cells of cerebral cortex).
Golgi type II multipolar ((highly branched, with short axon)) (stellate cells of cerebral cortex and cerebellum)

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10
Q

What are the functions of astroglia?

A

Scaffold for neuronal migration and axon growth during development.
Formation of blood-brain barrier.
Transport of substances from blood to neurons.
Removal of neurotransmitters; potassium ion buffering.

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11
Q

What are oligodendroglia? What do they do?

A

Myelin forming cells of the CNS. They are metabolically very active with a small spherical nucleus and prominent ER and Golgi complex.
Each cell produces multiple myelin sheaths (1-40).

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12
Q

What are microglia and what do they do?

A

The resident macrophage population of CNS, derived from the bone marrow during early development. Involved in immune surveillance. They present antigens to invading immune cells (they are the first cells to react to infection and damage).

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13
Q

What are peripheral glia (Schwann cells) and what do they do?

A

They produce myelin in the PNS. Each cell produces only one myelin sheath. Functions of astrocytes in the CNS are carried out by these cells in the PNS.

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14
Q

What is flux?

A

It is the rate of transfer of molecules: the number of molecules that cross a unit area per unit of time, i.e. molecules/m^2/s
At dynamic equilibrium there is no net flux.

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15
Q

What comprises the electrochemical gradient of an ion?

A

It is the net effect of the voltage gradient across a membrane and the concentration gradient of the ion across the membrane.
The equilibrium potential is where these 2 forces are balanced.

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16
Q

What is the equilibrium potential?

A

The potential at which electrochemical equilibrium has been reached. It’s the potential which prevents diffusion of the ion down its concentration gradient.

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17
Q

In the Goldman-Hodgkin-Katz (GHK) equation, what is denoted by P?

A

Permeability / channel open probability.

0 = 100% closed, 1 = 100% open, 0.5 = open 50% of the time

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18
Q

What is meant by graded depolarisations/hyperpolarisation?

A

It is the decremental spread of potentials as the effect of the stimulus decreases with distance.

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19
Q

Describe depolarisation in terms of the permeability of the membrane to different ions.

A

P(Na) increases dramatically as voltage gated Na+ channels open QUICKLY. Na+ enters down electrochemical gradient.
P(K) increases as voltage gated K+ channels open SLOWLY. K+ leaves cell down electrochemical gradient slowly –> less than Na+ entering.
Em moves towards Na+ equilibrium potential.

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20
Q

Describe repolarisation in terms of the permeability of the membrane to different ions.

A

P(Na) is 0 as voltage gated Na+ channels become inactive.
P(K) increases as more voltage gates K+ channels open and remain open. K+ leaves.
Em moves towards K+ equilibrium potential.

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21
Q

Describe the ball and chain hypothesis.

A

During initial repolarisation, the Na+ channel activation gate is open, yet the Na+ channel inactivation gate is closed. This is the absolute refractory period as another AP can’t be sent.

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22
Q

Describe the relative refractory period.

A

The inactivation gate of the Na+ channel is open, the Na+ channel activation gate is closed. A stronger than normal stimulus is required to trigger an action potential.

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23
Q

Define a neuromuscular junction.

A

A specialised synapse between a distal axon terminal and the muscle membrane, allowing for unidirectional chemical communication between peripheral nerve and muscle.

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24
Q

What are miniature end plate potentials (MEPPs)?

A

Detectable voltage changes due to individual vesicles releasing ACh.

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25
Q

How does botulism affect NMJs?

A

Botulinum produces irreversible disruption in ACh release.

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26
Q

What is myasthenia gravis (MG)?

A

An autoimmune condition where antibodies are directed against ACh receptors.

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27
Q

What is Lambert-Eaton myasthenic syndrome (LEMS)?

A

An autoimmune condition where antibodies are directed against VGCCs. Associated with lung cancer.

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28
Q

Describe electromyography (EMG).

A

Extra-cellular recording of action potentials in skeletal muscle fibres. Both electrodes are outside the muscle fibre: it measures the emf between 2 locations outside the cell.

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29
Q

What are the 3 key terms used to describe EMGs?

A

Twitch, twitch summation, fused/tetanic contraction.

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30
Q

What are the 3 classes of neurotransmitters?

A

Amino acids: glutamate, gamma amino butyric acid (GABA).
Amines: noradrenaline, dopamine.
Neuropeptides: opioid peptides.

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31
Q

How is neurotransmitter released from pre-synaptic knobs?

A

Synaptic vesicle proteins and synaptic membrane ‘docking’ proteins interact. When Ca2+ binds to a Ca2+ sensor in the protein complex, the neurotransmitter is released into the synaptic cleft.

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32
Q

What responses do glutamate and GABA illicit?

A 
Glutamate = excitatory (GLUR)
GABA = inhibitory (GABAR)
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33
Q

Describe the 2 types of glutamate receptors.

A

AMPA receptors: majority of fast excitatory synapses. Rapid onset, offset and desensitisation. Influx of Na+.
NMDA receptor: slow component of excitatory transmission. Influx of Na+ and Ca2+. Ca2+ modifies the AMPA receptor, potentiating the AMPA receptor response by activating protein synthesis which modifies synapse formation.

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34
Q

How is glutamate removed from the synaptic cleft?

A

Excitatory amino acid transporters (EAATs) on glial cells take up glutamate.
In the glial cell, glutamine synthetase converts glutamate to glutamine.

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35
Q

What is epilepsy?

A

Abnormal cell firing leading to seizures due to excess glutamate in synapse:
“Disorder of brain function characterised by periodic and unpredictable occurrence of seizures”

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36
Q

Define seizure.

A

Transient alteration of behaviour due to the disordered, synchronous and rhythmic firing of populations of brain neurones.

37
Q

What is the difference in structure between glutamate and GABA?

A

A COOH group is removed from glutamate to produce GABA.

38
Q

Which enzyme converts glutamate to GABA?

A

Glutamic acid decarboxylase (GAD).

39
Q

How is GABA removed from a synapse?

A

GABA transporters on the presynaptic knob’s membrane and glial cell membrane. In the cells, GABA-transaminase (GABA-T) converts it to succinate semialdehyde. This can be converted to succinate and used in the TCA cycle.

40
Q

Detail 4 drugs used to increase the effects of GABA at a synapse.

A

Benzodiazepine and phenobarbital bind to the GABAa receptor to enhance its effects (cause an influx of chloride ions). Tiagabine inhibits the GABA transporter, so less GABA is removed from the synaptic cleft. Vigabatrin inhibits GABA-T, preventing the conversion of GABA to succinate semialdehyde and removing a concentration gradient.

41
Q

What is the diencephalon?

A

A structure in the brain which sits on the brain stem and consists of the hypothalamus and thalamus. ((The thalamus relays information between the cerebral cortex and lower structures)).

42
Q

What is the cerebral cortex?

A

The outer layer of the cerebrum. 2-4mm thick. Roughly 30% is exposed and 70% is found within sulci.

43
Q

What is the limbic system?

A

A set of structures either side of the thalamus, including the hypothalamus, hippocampus, involved in motivation, instinctive behaviour, emotion and memory.

44
Q

What are the 3 types of white matter fibres in the brain?

A

Commissural fibres are between hemispheres.
Association fibres are within hemispheres.
Projection fibres are vertical.

45
Q

How much CSF is produced daily and how much is in your body at any one time?

A

500ml produced daily. Total is around 150ml.

46
Q

What is the central sulcus?

A

A sulcus in the cerebral cortex (also known as the central fissure) which separates the parietal lobe from the frontal lobe (the primary somatosensory cortex from the primary motor cortex).

47
Q

What is the difference between white and grey matter?

A

White matter is mainly bundles of axons: grey matter is mainly cell bodies (somata).

48
Q

In the spinal inner core of grey matter, what is it divided into?

A

Dorsal (posterior) horns with SENSORY function.

Ventral (anterior) horns with MOTOR functions.

49
Q

What is the foramen magnum?

A

The hole at the base of the skull through which the spinal cord passes.

50
Q

Where does the CSF flow?

A

Produced in the right and left lateral ventricles. Passes into third ventricle via the interventricular foramina and then through the cerebral aqueduct into the fourth ventricle. It then flows through the central canal in the spine, which is continuous with the ventricular system. It also passes from the fourth ventricle into the subarachnoid space.

51
Q

Outline the vertebrae, spinal nerves and their relationships.

A

7 cervical vertebrae with 8 spinal nerves. C1-7 above, C8 below.
12 thoracic vertebrae and 12 spinal nerves. All below.
5 lumbar vertebrae and 5 spinal nerves. All below.
5 sacral vertebrae and 5 spinal nerves. All below.
1 coccyx (may be 4). Below, unless unfused.
Total of 30 (33) vertebrae and 31 spinal nerves.

52
Q

Where is a lumbar puncture performed and why?

A

Between L3 and L4 in adults, L4 and L5 in children.
The spinal cord terminates at the conus medullaris (below either L1 or L2). Nerves continue down the spine below this, but in a loose bundle called the cauda equina. There is therefore a lower risk inserting a needle here as the loose fibers move out of the way without being damaged.

53
Q

Outline differences in the composition of CSF and blood plasma.

A 
CSF has:
Lower pH (7.33)
Lower glucose
Lower protein
Lower calcium and potassium ion levels.
Higher chloride and magnesium ion levels.
54
Q

How many nerves does the PNS consist of?

A

43 pairs: 12 cranial nerves and 31 spinal.

55
Q

Describe basically how information is sent from the CNS to effectors in the motor branch of the SNS and ANS.

A

In the SNS, a somatic motor neurone sends an impulse directly from the CNS to the effector, such as a muscle cell.
In the ANS, there is a preganglionic neurone from the CNS to the ganglion, and a postganglionic neurone from there to the effector, e.g. blood vessels.

56
Q

Describe basically how information is sent from receptors to the CNS in the sensory branch of the SNS.

A

Impulse travels directly from the receptor to the CNS, via a ganglion. There are no synapses in dorsal root ganglions.

57
Q

What is a nerve plexus?

A

A network of successive ventral rami which exchange fibres (criss-cross and redistribute) and innervate the limbs.

58
Q

What is the name for neuropathy where there is no axonal discontinuity?

A

Neuropraxia.

59
Q

What is the name for neuropathy where there is demyelination and axonal loss, yet the epineurium and perineurium are still in tact?

A

Axonotmesis.

60
Q

What is the name for neuropathy where the axon is disrupted, support cells are destroyed and the epineurium is damaged?

A

Neurotmesis.

61
Q

Where do dorsal rami innervate?

A

The muscle and skin of the back.

62
Q

What is Wallerian degeneration?

A

The degeneration of the distal part of a peripheral nerve where macrophages come and phagocytose axonal and myelin debris.

63
Q

What is chromatolysis?

A

In peripheral nerve damage, the proximal part of the axon and soma usually survive but undergo metabolic changes.

64
Q

What factors can decrease conduction velocity of peripheral nerve axons?

A

Hypothermia, increased pressure to nerve, bundle loss of myelin.

65
Q

Describe briefly the structure of the parasympathetic branch of the ANS.

A

The nerves arise from the cranial and sacral regions of the spinal cord. The preganglionic fibres are very long, and postganglionic fibres very short. The parasympathetic ganglia are located in or very close to the target tissue.

66
Q

Describe briefly the structure of the sympathetic branch of the ANS.

A

The sympathetic nerves arise in the thoracic and lumbar regions of the spinal cord. The pre-ganglionic fibre is short and the ganglia are located in a chain close to the vertebral column (paravertebral ganglia) and also closer to the target tissue (e.g. coeliac ganglion). The connections between these ganglia allow for mass activation of the sympathetic system in for example conditions of stress. Also included in the sympathetic system is the adrenal medulla which also acts as a modified ganglion but releases its products directly into the blood stream.

67
Q

Describe the autonomic innervation of the penis.

A

Sympathetic nerves involved in penis flaccidity and ejaculation. Parasympathetic nerves involved in erections.

68
Q

Which neurotransmitter is used in the sympathetic ganglia (including the adrenal medulla)?

A

ACh

69
Q

Describe the ACh receptors in the parasympathetic nervous system.

A

Receptor following the preganglionic neurone is a NICOTINIC ACh receptor.
Receptor following the postganglionic neurone is a MUSCARINIC ACh receptor.

70
Q

Which neurotransmitter is used at different parts of the body by postganglionic sympathetic neurones?

A

NA: heart, kidneys, vessels
ACh: sweat glands (MUSCARINIC RECEPTOR)
DA: renal vessels.

71
Q

Give features of the cephalic response.

A

Pancreas releases insulin.

Release of gastric juices from stomach.

72
Q

What is the intermediolateral cell column?

A

Where sympathetic preganglionic neurons arise in the spinal cord, present between T1 - L3.

73
Q

Describe the central respiratory centre in the brainstem.

A

Consists of the pontine respiratory centre and the medullary respiratory centre. The PRC is responsible for rate and pattern of breathing: the MRC is split into the ventral group, responsible for coordinating rhythmicity, and the dorsal group, responsible for inspiration and control of diaphragm.

74
Q

What is the difference between peripheral chemoreceptors and central chemoreceptors (in the ventral group)?

A

The central chemoreceptor doesn’t respond to oxygen levels, only pH and CO2.

75
Q

Describe the ANS innervation of the bladder.

A

Activation of the PNS = contraction of the detrusor muscle.
Activation of the SNS = contraction of the internal sphincter.
((External sphincter innervated by motor neurones, giving voluntary control).

76
Q

What are tubocurarine and atropine?

A

Tubocurarine is a nicotinic antagonist. However, it is rarely used as nicotinic receptors are used at NMJs.
Atropine is a muscarinic antagonist.
The PARASYMPATHETIC NS uses these cholinoceptors.

77
Q

Describe the distribution of the adrenoceptors used by the SYMPATHETIC NS.

A

A2 at end of postganglionic neurone innervating smooth muscle.
A1 on smooth muscle. (Contraction)
B1 Heart.
B2 On smooth muscle. (Relaxation). Causes sphincters of GI tract to contract.

78
Q

What does medetomidine do?

A

A2 AGONIST: inhibits NA release.

79
Q

What does doxazosin do?

A

A1 antagonist: smooth muscle dilation.

80
Q

What does atenolol do?

A

B1 antagonist

81
Q

What does salbutamol do?

A

B2 AGONIST: relaxes smooth muscle.

82
Q

What is craniosacral outflow?

A

Preganglionic fibres of PNS found in cranial and sacral nerves.

83
Q

What is the sympathetic trunk?

A

A chain of ganglia next to vertebrae for the entire length of the vertebral column. Allows dispersion of sympathetic outflow from a small region of the spinal cord to peripheral regions via all spinal cords.

84
Q

How is tyrosine converted into adrenaline?

A

Tyrosine –> DOPA (tyrosine hydroxylase)
DOPA –> dopamine (DOPA-decarboxylase)
Dopamine –> noradrenaline (dopamine B-hydroxylase)
NA –> adrenaline (phenyl-N-methyl transferase)

85
Q

How is DA broken down?

A

Transported into support cells - degradation by COMT (catechol-O-methyl transferase).
Transported into presynaptic neurone and metabolised by MAO-A (monoamine oxidase A)

86
Q

What is the enteric nervous system?

A

It is a division of the ANS consisting of a mesh-like system of neurones which govern the function of the GI tract.
Capable of acting independently of the sympathetic and parasympathetic nervous systems - although it may be influenced by them.
Myenteric plexuses = motility.
Submucosal plexuses = regulation of GI secretion, endocrine function & blood flow.

87
Q

What are Broca’s and Wernicke’s areas of the brain responsible for?

A

Broca’s area = speech production

Wernicke’s area = speech comprehension.

88
Q

What is special about the modified ependymal cells in the choroid plexus?

A

They secrete and filter blood from adjacent capillaries to produce CSF.

89
Q

Define twitch

A

The force and/or movement response to a single action potential.

Life Cycle and Reproduction Systems (LCRS) (4 decks)

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