Neuro Flashcards
1
Q
What is sound?
A
Displacement of air particles following a sinusoidal pattern of compression and rarefaction.
2
Q
What is the range of hearing for humans?
A
20Hz -> 20kHz.
3
Q
What are the four components of the auditory system?
A
- The outer ear.
- The middle ear.
- The inner ear.
- Central auditory pathways.
4
Q
What does the outer ear consist of?
A
- Pinna.
- Ear canal.
- Tympanic memebrane.
5
Q
What is the function of the pinna?
A
- Shaped to gather sound waves and direct them into the ear canal.
- Filters out lower frequency sounds.
- Each pinna is unique.
6
Q
What is the function of the ear canal?
A
Directs sound waves towards the tympanic membrane.
7
Q
What happens when sound hits the tympanic membrane?
A
It vibrates like the surface of a drum and transmits the sound waves deeper into the ear towards the cochlea.
8
Q
What does the middle ear consist of?
A
- The ossicles.
- The Eustachian tube.
- Tensor tympani and stapedius muscles.
9
Q
Describe the ossicles and how they function.
A
- Malleus (hammer): rests against tympanic membrane, head of the ‘hammer’ connects to incus.
- Incus (anvil): when struck by ‘hammer’ sound waves are transmitted to the stapes.
- Stapes (stirrups): receives sound waves, transmitting them to oval window.
10
Q
Discuss the importance of the superior and inferior openings of the auditory tube.
A
- Superior: middle ear cavity.
- Inferior: nasal cavity.
- Therefore, connection of airflow from external environment and middle ear.
- Vital for maintaining equal air pressure either side of the tympanic membrane, preventing pain and rupture.
11
Q
What is the main role of the tensor tympani and stapedius muscles?
A
To dampen sound vibrations and reduce perceived volume.
12
Q
What does the inner ear consist of?
A
- The cochlea.
- The vestibular system.
13
Q
What does the cochlea allow us to perceive?
A
Sound.
14
Q
What does the vestibular system consist of?
A
- Semicircular canaks.
- Utricle.
- Saccule.
15
Q
What does the vestibular system allow us to perceive? Which structures within it allow these perceptions?
A
Movement - semicircular canals.
Linear acceleration - utricle and saccule.
16
Q
What are the 2 openings of the cochlea?
A
Round window and oval window.
17
Q
What are the 3 components of the cochlea?
A
- Scala vestibuli.
- Scala media.
- Scala tympani.
18
Q
Which ionic fluid is found in the scala media?
A
Perilymph, high in K+.
19
Q
Which ionic fluid is found in the scala vestibuli and scala tympani?
A
Endolymph, rich in Na+.
20
Q
What affect on hearing can ion channel abnormalities have?
A
Can cause deafness.
21
Q
Describe the basilar membrane.
A
- Narrow and stiff at base.
- Wide and floppy at apex.
22
Q
What is tonotopy and which membrane has this feature?
A
- The organisation of sound frequencies along an axis.
- Basilar membrane.
- High frequencies detected at base.
- Low frequencies detected at apex.
23
Q
Where is the organ of Corti?
A
In the scala media.
24
Q
Are the basilar and tectorial membranes mobile or fixed in place?
A
Basilar - mobile.
Tectorial - fixed.
25
Discuss the importance and basic roles of the hair cells of the organ of Corti.
Inner hair cells - important, mechanical transduction.
Outer hair cells - helpful, fine tuning.
26
How do the inner hair cells perform mechanical transfuction?
Basilar membrane moves -> inner hair cells move -> activate attached cochlear nerve fibres -> cochlear nerve -> activated central auditory pathway.
27
What will occur upon loss of inner hair cells?
Deafness.
28
How do the outer hair cells fine tune sound?
Stiffen basilar membrane either side of the maximum stimulated inner hair cells, to focus on that sound and dampen others.
29
What will occur upon loss of outer hair cells?
Loss of sharpness of hearing.
30
What is interaural time difference?
One ear hearing a sound first, as that ear is closer to the sound.
31
What is interaural intensity difference?
One ear hearing a sound louder, as that ear is closer to the sound.
32
What type of hearing loss occurs with a defective outer/middle ear?
Conductive hearing loss.
33
What type of hearing loss occurs with a defective inner ear?
Sensorineural hearing loss.
34
What are neurons specialised for?
Electrical signalling.
35
When are neurons mainly formed?
During development, but small areas of the brain may continue making neurons e..g the hippocampus.
36
Which are formed first; neurons or glia?
Neurons.
37
What are the two forms of neuronal synapse?
Chemical and electrical.
38
How do chemical synapses work? Give an example.
Via neurotransmitters e.g. glutamate.
39
How do electrical synapses work? Give an example.
Via a direct flow of ions e.g. hypothalamus for hormone secretion.
40
Define neural plasticity.
Changes in neuronal/synaptic structure and function in response to neural activity. It is the basis of learning and memory.
41
Give an example of neuronal heterogenity.
Neocortex. 6 layers of varying cells/structures.
42
What is the key role of oligodendrocytes?
Myelinating cells of the CNS.
43
Describe the role of myelin.
Insulates axon segments, enabling rapid nerve conduction.
44
Describe the structure of the myelin sheaths.
Interrupted by nodes of Ranvier, to allow saltatory conduction (faster).
45
Describe microglia.
Resident immune cells of the CNS. Phagocytic.
46
Describe the origin of microglia.
Originate from yolk sac progenitors that migrate into the CNS, therefore closer to macrophages in origin.
47
Describe the varying structure of microglia in different states.
Resting state - highly ramified.
Activated - retract processes, become amoeboid.
48
Give 3 functions of microglia.
- Immune surveillance.
- Phagocytosis.
- Synaptic plasticity.
49
Describe astrocytes.
Star-like cells, most numerous glial cells in the CNS, highly heterogenous.
50
Give 5 functions of astrocytes.
- Define brain micro-architecture.
- Envelope / tripartite synapses, buffer K+ etc.
- Metabolic support.
- Neurovascular coupling.
- Proliferate in disease.
51
Name 3 specialised astrocytes.
- Radial glia.
- Bergmann glia.
- Müller cells.
52
What are radial glia important for?
Brain development.
53
What are Bergmann glia important for?
Structure (cerebellum).
54
What are Müller cells important for?
Providing a scaffold for other cells to form on (retina).
55
Define motor neurone disease.
Adult-onset neurodegenerative disease, characterised by loss of upper and lower motor neurones.
56
Define multiple sclerosis.
Autoimmune demyelinating disease, where immune cells attack the myelin sheath of oligodendrocytes.
57
Give the 4 features of the blood-brain barrier.
- Endothelial cell tight junctions.
- Basement membrane.
- Astrocyte end feet.
- Pericytes.
58
Give 4 events that the blood-brain barrier is sensitive to.
- Inflammation.
- Hypertension.
- Trauma.
- Ischaemia.
59
Where can ependymal cells be found?
Lining ventricles and the central canal of the spinal cord.
60
What is the function of ependymal cells?
- CSF production, flow and absorption.
- Allowing solute exchange between nervous tissue and CSF.
61
Describe the structure of ependymal cells.
- Epithelial-like.
- Ciliated to facilitate flow,.
62
What is the main site of CSF production?
Choroid plexus.
63
How is the choroid plexus formed?
From modified ependymal cells.
64
What does the term myoclonus refer to? Give an example of a form of myoclonus.
- A quick jerking movement that you cannot control.
- E.g. the hiccups.
65
Describe the McGurk Effect.
Occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound.
66
What % of your brain is far?
60%.
67
What % are the neocortex and language centres of your brain?
76%.
68
What are the primitive reflexes?
The reflex actions arising from the brainstem that are typically present in childhood, but not in healthy or neurological intact adults, in response to particular stimuli.
69
What is the rooting reflex?
Turn head and mouth in direction of stroking of cheek.
70
What is the sucking reflex?
Sucking objects that touch the lips.
71
What is the moro (startle) reflex?
Back arches, legs and arms flung out and then brought back towards chest in hugging motion.
72
What is the grasping (palmar) reflex?
Grasping objects pressed against palms.
73
What is the stepping reflex?
Mimicking walking when held upright.
74
What is the babinski reflex?
Fanning toes when feet are stroked.
75
What is the tonic-neck reflex?
Turning head to one side, extending arm and leg.
76
How long are infants usually ambidextrous?
Until 3 years old.
77
Define anencephaly.
A serious birth defect in which a baby is born without parts of the brain and skull, a form of NTD.
78
Define lishencephaly.
A smooth brain, a neuronal migration disorder.
79
Describe cystic periventricular leukomalacia and its rarity.
- Death of oligodendrocytes -> virtually no plasticity,
- Around 5% of babies less than 32 weeks.
80
What can mutations of the PHOX2B gene affect?
The development of the key structures that regulate chemical control of breathing.
81
Give 5 things neural crest cells form.
- Sensory ganglia.
- Schwann cells.
- Adrenal medulla.
- Meninges.
- Dermis.
82
Where can the tectum be found?
A region of the midbrain posterior to the cerebral aqueduct of Sylvius.
83
What does the tectum contain, and what are these involved in?
- Nuclei of the superior and inferior colliculi.
- Colliculi process stimuli before they reach their corresponding primary processing centres.
- Superior = visual stimuli.
- Inferior = auditory stimuli.
84
Where can the tegmentum be found?
Between the cerebral aqueduct and the pars compacta of the substantia nigra.
85
What are the names of the two areas of the tegmentum named after colours?
- The red nucleus.
- The periaqueductal grey.
86
Describe the substantia nigra.
- Part of basal ganglia.
- Two parts: pars compacta and pars reticular.
- Pars compacta = basal ganglia input.
- Pars reticular = basal ganglia output.
87
What is the red nucleus involved in?
The co-ordination of movements.
88
What is the periaqueductal grey involved in?
Pain processing.
89
What is the limbic system made up of (not inclusive)?
- Amygdala.
- Hippocampus.
- Fornix.
- Cingulate gyrus.
- Septum.
- Mammillary body.
- Hypothalamus.
- Thalamus.
90
What is the limbic system involved in?
- Emotion.
- Motivation.
- Emotional associations within memory.
91
Define a neuron.
The basic cellular unit of the nervous system.
92
How many neurons are there in the average human brain?
~ 100 billion.
93
How many synapses are there in the average human brain?
~ 150 trillion.
94
Although neurons can be specialised, which 4 basic components do they all have?
- Dendrites.
- Cell body.
- Axon.
- Presynaptic terminals.
95
Define axonal transmission.
Transmission of information from location A to location B.
96
Define synaptic transmission.
Integration/processing of information and transmission between neurons.
97
At rest, describe the neuron's electric charge? Why is it this way?
- Negative ~ -70mV.
- Large organic proteins are the reason.
98
Describe the permeability of the neuronal cell membrane. Give some examples of what can/cannot pass through.
- Semi-permeable.
- K+ and Cl- cross readily.
- Na+ cross with difficulty.
99
What are the 2 forces determining the distribution of charged ions?
- Diffusion.
- Electrostatic attraction/repulsion.
100
Describe the locations of these ions at rest:
- Anions (proteins)
- Na+
- K+
- Cl-
- Anions (proteins) = restricted to inside of cell.
- Na+ = mostly outside cell.
- K+ = mostly inside cell.
- Cl- = mostly outside cell.
101
Describe the sodium-potassium pump of a neuron.
- Transports Na+ out of neuron.
- Transports K+ into neuron.
- 3 Na+ out for every 2 K+ in.
- Requires energy supplied by ATP.
102
What do excitatory neurotransmitters do to the cell membrane?
- Depolarise it.
- Increasing the chance of an action potential.
- Causes an excitatory post synaptic potential (EPSP).
103
What do inhibitory neurotransmitters do to the cell membrane?
- Hyperpolarise it.
- Decreasing probability of an action potential being generated.
- Causes an inhibitory post synaptic potential (IPSP).
104
Explain the generation of an action potential via EPSPs.
Will only be generated if the membrane potential is depolarised beyond the threshold of excitation, which may take multiple triggers to create a big enough EPSP).
105
What is the excitation threshold for an action potential to be generated?
~ - 60mV.
106
Give 7 symptoms of multiple sclerosis.
- Uncontrolled eye movements/seeing double.
- Slurred speech.
- Partial/complete paralysis.
- Tremor.
- Loss of co-ordination.
- Weakness/fatigue.
- Numbness/prickling/pain.
107
Which groups of people get multiple sclerosis?
- Young adults (20 -> 40).
- Slightly more women then men.
108
What is the affect of Novichok?
- Disrupts synaptic neurotransmission for ACh, as it is an AChE inhibitor (stops breakdown of acetylcholine).
109
How can the effects of Novichok be treated?
By using atropine (an ACh receptor blocker.
110
What 2 processes prevent neurotransmitters remaining active in a synapse?
- Enzymatic degradation.
- Re-uptake.
111
What does acetylcholine do?
- It is a key neurotransmitter at the neuromuscular junction.
- Activates muscles, not just skeletal for voluntary, but also the heart, respiratory muscles, GI tract, eye muscles, and muscles around blood vessels.
112
What are the 5 fundamental processes of synaptic tranmission?
1. Manufacture.
2. Storage.
3. Release.
4. Interact with post-synaptic receptors.
5. Inactivation.
113
Name 3 'fast' neurotransmitters.
- Acetylcholine.
- Glutamate.
- Gamma-aminobutyric acid.
114
Name 3 neuromodulators.
- Dopamine.
- Noradrenaline.
- Serotonin.
115
Name 4 things that can affect acetylcholine, and how they affect it.
- Cigarettes (agonist).
- Poison arrows (antagonist).
- Spider toxins (release.
- Nerve gas (blocks break down).
116
What is gamma-aminobutyric acid?
The main inhibitory neurotransmitter.
117
Name 3 things that affect gamma-aminobutyric acid, and how they affect it.
- Anti-anxiety drugs (inhibit receptors).
- Anticonvulsant drugs (inhibit receptors).
- Anaesthetics (potentiate the effects).
118
Name 3 things that affect dopamine, and how they affect it.
- Antipsychotic drugs (block receptors).
- Stimulants (increase release, block re-uptake).
- Anti-Parkinson drugs (increases manufacture).
119
Name 2 things that affect noradrenaline, and how they affect it.
- Antidepressants (block re-uptake and block breakdown).
- Stimulants (increases release and blocks re-uptake).
120
Name 3 things that affect serotonin, and how they affect it.
- Antidepressants (SSRI = re-uptake inhibitor).
- Hallucinogens (receptor agonist).
- Ecstasy (increases release, reduces re-uptake).
121
What are 2 problems for drug design regarding neurotransmitters?
- A region of the brain engaged in a particular function uses several neurotransmission systems.
- Regions of the brain engaged in different function use the same neurotransmission systems.
122
What are the 4 types of motor control?
- Voluntary.
- Goal-directed.
- Habit.
- Involuntary.
123
In what manner to individual muscles fibres act?
In an 'all or none' way.
124
What % of body weight does muscle take up?
~ 40%.
125
What is the smallest muscle in the body?
Stapedius.
126
What is the largest muscle in the body?
Gluteus maximus.
127
What is the strongest muscle in the body?
Masseter.
128
How does the number of muscle fibres an individual has vary?
Appears genetically determined, very little change with time or training.
129
Describe the composition of a skeletal muscle.
- Attached to a bone by a tendon.
- Comprises several muscle fasciculi.
- Each muscle fasciculus comprises several muscle fibres.
- Each muscle fibres comprises of several myofibrils.
- Myofibrils contain actin and myosin protein filaments.
130
How do muscles contract?
When muscle fibre is depolarised, actin and myosin slide past each other - producing muscle contraction.
131
Define a motor unit.
A single alpha motor neuron and all the muscle fibres it innervates.
132
How many muscle fibres are innervated by a motor neuron?
Different motor neurons innervate different numbers of muscle fibres.
133
What is possible when motor neurons innervate fewer muscle fibres? Give 2 examples.
Fewer fibres = greater movement resolution.
E.g. finger tips and tongue.
134
What does activation of an alpha motor neuron cause?
Depolarisation, contraction of all muscle fibres in that motor unit.
135
What 2 things does the CNS need to know about muscles to be a good control system?
- How much tension is on the muscle.
- What is the length/stretch of the muscle.
136
What senses tension on a muscle?
Golgi tendon organs.
137
Under conditions of extreme tension, what can golgi tendon organs do?
Inhibit muscle fibres, via a circuit in the spinal cord, to prevent damage.
138
What senses stretch of a muscle?
Muscle spindles.
139
Describe muscle spindles.
- Muscle sensory receptors.
-Embedded within most muscles.
- Composed of intrafusal fibres with sensory fibres coiled around them.
140
How are intrafusal fibres innervated?
Separately to extrafusal, by gamma motor neurons.
141
What is the simplest reflex?
The stress reflex.
142
Why do cats always land on their feet?
The vestibular righting reflex.
143
What does the "Myosin Cross-Bridge Cycle' require?
- ATP.
- Calcium ions.
- Magnesium ions.
144
Which neurotransmitter triggers the Myosin Cross-Bridge cycle?
Acetylcholine.
145
Why does rigor mortis occur?
As ATP is required for the Myosin Cross-Bridge cycle, and ATP is produced by oxidative metabolism - which stops after death -> muscle contraction and stiffness = rigor mortis.
146
Discuss slow vs fast twitch muscle fibres, and fatigue.
Slow = fatigue resistant.
Some fast = fatigue after a while.
Some fast = fatigue rapidly.
147
Where does motor command originate?
In motor cortex pyramidal cells (upper motor neurones).
148
How accurate is the homoculus?
- Oversimplification.
- In reality, more complex and overlapping.
- Few motor commands require isolated activation of a single motor unit.
149
What 2 routes do the dorsolateral tracts contain?
- A direct corticospinal route.
- An indirect corticorubrospinal route.
150
What does the indirect dorsolateral tract route (corticorubrospinal) go via?
The red nucleus.
151
Which side do dorsolateral tracts innervate?
The contralateral side of one segment of the spinal cord.
152
Which muscles do the dorsolateral tracts project to?
Distal muscles e.g. fingers.
153
What 2 routes do the ventromedial tracts contain?
- A direct corticospinal route.
- An indirect cortico-brainstem-spinal tract.
154
What does the indirect ventromedial tract route (cortico-brainstem-spinal) go via?
- Tectum.
- Vestibular nuclei.
- Reticular formation.
- Cranial nerve nuclei.
155
What % of the total brain weight does the cerebellum make up?
10%.
156
DISINHIBITORY PATHWAY
157
What is the autonomic nervous system divided into?
Parasympathetic and sympathetic.
158
In terms of male sexual function, explain which acts are parasympathetic vs sympathetic.
Parasympathetic = erection.
Sympathetic = ejaculation.
159
What are the 3 forms of output for the autonomic nervous system?
- Parasympathetic.
- Sympathetic.
- Enteric NS.
160
Which type of receptor would be present in the sympathetic system opposed to the parasympathetic system?
Adrenergic receptor.
161
Which type of receptor would be present in the parasympathetic system opposed to the sympathetic system?
Muscarinic receptor.
162
Which type of receptor would be present in both parasympathetic and sympathetic systems?
Nicotinic receptors.
163
Name an input of the autonomic nervous system.
The carotid baroreceptors.
164
How are ANS disorders divided?
Primary and secondary ANS disorders.
165
Give an example of a primary ANS disorder.
- Multiple system atrophy (Shy-Drager syndrome).
- Autonomic failure with Parkinson's disease.
166
Give an example of a secondary ANS disorder.
- Diabetes mellitus.
- Chronic renal failure.
- Chronic liver disease.
- Guillain-Barre syndrome.
- Tetanus.
- HIV.
- Brain tumours.
167
What is the easiest way of measuring ANS function?
Cardiovascularly:
- Heart rate and blood pressure beat-by-beat.
- Head-up tilt test.
- Baro-reflex testing (phenylephrine test).
168
Give 5 non-cardiovascular ways to measure ANS function.
- Pupillometry.
- Sweat measurement.
- Skin blood flow (thermoregulation).
- Gastric acid secretion.
- Sexual function.
169
What 3 groups of disorders may be associated with basal ganglia dysfunction?
- Motor disorders.
- Psychiatric disorders.
- Secondary damage.
170
Give 4 motor disorders associated with basal ganglia dysfunction.
- Parkinson's disease.
- Huntington's disease
- Dystonia.
- Gilles de la Tourette syndrome.
171
Give 2 psychiatric disorders associated with basal ganglia dysfunction.
- Obsessive compulsive disorder.
- Attention deficit hyperactivity disorder.
172
Give 2 forms of secondary damage associated with basal ganglia dysfunction.
- Cerebral palsy.
- Wilson disease.
173
How many dopamine receptors are there? How many classes are there?
5:
- D1 - D5.
2:
- D1 = D1 and D5.
- D2 = D2, D3, and D4.
174
Describe the pathway to dopamine.
L-Tyrosine -> L-DOPA -> Dopamine.
175
Describe Parkinson's disease in terms of muscle tone, movement and dopamine.
- Increased muscle tone.
- Reduced movements.
- Not enough dopamine.
176
Describe Huntington's disease in terms of muscle tone, movement and dopamine.
- Decreased muscle tone.
- Overshooting movements.
- Too much dopamine.
177
Give 3 key features of Parkinson's disease.
- Brady/akinesia.
- Tremor.
- Rigidity.
178
Give 3 key features of Huntington's disease.
- Chorea.
- Dementia/psychiatric illness.
- Personality change.
