Neurology Flashcards
What is the most common pathophysiology of stroke?
Blockage of blood vessel.
Haemorrhage is often associated with…
Hypertension
What causes changes in membrane potential?
The electrochemical and concentration gradients.
How are ion channels generally closed?
By hyperpolarisation/ repolarisation
What returns a cell to its resting membrane potential?
Potassium efflux from cell.
What is Saltatory conduction?
Electrical conduction moving from one node of ranvier to another to speed up conduction.
Name two factors which affect conduction velocity
Myelination and axon diameter
Will conduction velocity be faster in a smaller diameter or a larger diameter?
Larger; less internal resistance
What is the main issues in Multiple Sclerosis? Apart from this what else may you see under a microscope?
Demyelination of axons. Can also see a lower cell density.
What is the neuromuscular junction?
A specialised synapse between a motor neuron and a muscle fibre.
What is the characteristic pathology of Multiple Sclerosis?
Inflammation and Loss of myelin within the CNS.
Are receptors on the pre-synaptic or post synaptic membrane?
The post-synaptic membrane
Which is the neurotransmitter for voluntary striated muscle?
Acetylcholine
What are MEPPs?
Miniature end-plate potentials = Small potentials at rest caused by individual vesicles releasing ACh.
What is the name of the cytoplasm within the muscle?
The sarcoplasm
What is the sarcolemma?
The plasma membrane which covers the myofibre.
Estimate the diameter of the myofibre.
1-2um.
What is another name for the dark band?
The A band
What is another name for the light band?
The I band
Does the A band’s length change during contraction?
No. The A band remains at the same length.
What is the name of the neuromuscular disease which does not allow ACh to be released into the synaptic cleft?
Botulism.
Which is the neuromuscular disease which causes antibodies to bind to ACh receptors on the post synaptic cleft?
Myasthenia Gravis
What is Lambert Eaton Myasthenia syndrome?
An autoimmune disorder where channels at the pre-synaptic cleft do not allow calcium in.
What is an electromyogram?
Records action potentials in the skeletal muscle.
What is Lambert-Eaton Myasthenic syndrome associated with?
Lung Cancer
Define Multiple Sclerosis
A chronic inflammatory disease of the CNS causing oligodendroglial and axonal pathology.
What two diagnostic components are involved in diagnosing Multiple Sclerosis?
MRI and CSF analysis to show inflammation
Name x5 neurological diseases
Stroke, Multiple Sclerosis, Epilepsy, Parkinson’s, Carpel Tunnel syndrome
A 50 year old man who smokes and has high blood pressure collapses at work. He is unable to speak, and move the right side of his face. He is unable to move his right arm or leg. Where is the problem?
Brain
Name the two types of stroke and which is more common?
Ischaemic - 80%
Haemorrhagic - 20%
What is the word used to describe symptoms felt on the opposite side of the brain legion?
Contralateral
Which side of the brain is responsible for language?
The left side
Which artery is most commonly affected in strokes?
The Middle cerebral artery
What sign is most commonly seen in middle cerebral artery strokes?
Weakness and loss of sensation contralaterally
What sign is most commonly seen in posterior cerebral artery strokes?
Visual Loss contralaterally
What sign is most commonly seen in anterior cerebral artery strokes?
Leg weakness contralaterally
Which part of the brain is affected in Parkinson’s Disease?
The Basal Ganglia
Name x3 clinical features of Parkinson’s Disease
Rigidity, Tremor and Bradykinesia
What does bradykinesia mean?
Reduced movement
What is the name of the chemical affected in Parkinson’s which does not cross the blood brain barrier?
Dopamine
Absent reflexes are associated with a lesion situated where?
The Lower motor neurone
Present reflexes are associated with a lesion situated where?
The Upper motor neurone
Name x2 common causes of acute neuromuscular weakness
Guillain Barre Syndrome and Acute Inflammatory Demyelinating Polyneuropathy (GBS/AIDP)
To measure Cerebrospinal fluid, what diagnostic method is used?
Lumbar puncture
From which part of the brain do seizures arise?
The Cerebral cortex
What is the cause of epilepsy?
A decrease in the inhibitory action of GABA or an increase in excitatory action of Glutamate.
What are anticonvulsants?
A group of treatments used to prevent seizures e.g. glutamate receptor antagonist.
Name x5 anti-epileptic drugs
Valproate, Phenobarbital, Benzodiazepines, Vigabatrin, Tiagabine.
Which class of anti-epileptic drugs enhance GABA action
Benzodiazepines e.g. Diazepam and Phenoarbitals.
What is the mechanism of action of Vigabatrin?
Inhibits GABA transaminase
What is the mechanism of action of Tiagabine?
Inhibits GABA reuptake
What is the mechanism of action of Phenobarbital?
Enhanced GABA action
What is the mechanism of action of Valproate?
Weak effect on GABA transaminase and Na+ channels
Which anti-epileptic medications are used on all forms of epilepsy?
Benzodiazepines and Vigabatrin.
Which anti-epileptic medication can be used in all forms of epilepsy apart from absence seizures?
Phenoarbital
Which anti-epileptic medication is used on focal seizures?
Tiagabine
What is the name of the enzyme which converts GABA to glutamate?
GABA Transaminase
What are spines?
Protrusions which sit on the dendrite. These protrusions receive the majority of synapses.
What are axons made up of?
Intermediate filaments and microtubules
What are the three types of neurone synapses?
Axo-dendritic, axo-somatic and axo-axonic.
What is the range length of an axon in humans?
um-1m
What is the cytoskeleton made up of?
Microfilaments, intermediate filaments and microtubules.
What are the differences between Golgi I multipolar and Golgi II multipolar neurones?
Golgi I multipolar neurones = long axons
Golgi II multipolar neurones = short axons
What is the group name of astrocytes, schwann cells, oligodendrocytes and microglia
Neuroglia
Which is the most abundant nerve cell in the human body?
Astrocytes
Give x5 functions of astrocytes
- Formation of blood-brain barrier
- Removal of neurotransmitters
- Axonal Growth during development
- Glial Scar formation
- K+ buffering
Which receptors on astrocytes allow glutamate in?
EAAT-2 receptors
Which are the myelin forming cells of the CNS?
Oligodendrocytes
Describe the structure of oligodendrocytes
Small nuclei, few thin processes, many ER and GA
What is the main function of microglia?
Immune function. Present antigens to invading immune cells, act as macrophages.
Which is the phagocytic nerve cell?
The microglia
Which are the myelin forming cells of the PNS?
The Schwann cells
What is the average length of time between two action potentials?
2ms
Name the three stages of synaptic transmission
- Biosynthesis, packaging and release of neurotransmitter
- Receptor activation
- Inactivation
Glutamate and GABA are examples of what type of neurotransmitter?
Amino acid neurotransmitter.
Noradrenaline = amine
Which ion is essential for neurotransmitter release?
Ca2+
Approximately how many molecules are there per synaptic vesicle?
4000- 10,000
How do vesicles release neurotransmitters into the synaptic cleft?
The vesicle fuses with the membrane and release their neurotransmitters via exocytosis.
How do vesicles rapidly release neurotransmitters?
Interaction between the synaptic vesicle and synaptic membrane proteins = rapid response. The vesicle is docked in a ‘prime’ zone close to Calcium channel. Entry of calcium through channel activates a sensor in the protein complex.
What is the protein complex made up of?
The synaptic vesicle, proteins and membrane.
Which transmission is faster - impulses through ion channel receptors or G-Protein coupled receptors?
Ion channel receptors
ACh at nicotine receptors moves through which type of receptor?
Ion channel receptors
ACh at muscarinic receptors moves through which type of receptor?
G-Protein coupled receptors
Compare the ion flow through Glutamate receptors Vs GABA receptors
Glutamate = Na+ flow GABA = Cl- flow
GLUR, AMPA and NMDA receptors are examples of what type of receptor?
Glutamate receptors
Which receptor is the fast excitatory synapse receptor?
AMPA
Which receptor is the slow excitatory synapse receptor?
NMDA
Where are glutamate and GABA transporters found?
On the Glial cell
What is the name of the glutamate transporter on the glial cell?
EAAT - Excitatory amino acid transporter
What does glutamate break down to?
Glutamine
What is the name of the GABA transporter on the glial cell?
GAT - GABA Transporter
What chemical does GABA break down to and by which enzyme?
Succinate semialdehyde (SSA) via GABA Transaminase.
What is the name of the enzyme which breaks Glutamate down to GABA?
Glutamic acid decarboxylase
Describe the structure of the GABA receptor.
Pentameric. Different binding sites for barbiturates, benzodiazepines, GABA, ethanol and steroids.
The sympathetic and parasympathetic system are parts of which type of control?
Autonomic control
How is the peripheral system divided?
Somatic control and autonomic control
Where is the visual cortex?
In the occipital lobe
Where is the somatosensory cortex?
In the parietal lobe
Which is the longest cranial nerve?
The vagus nerve
What is the name of the connective tissue that covers the brain?
The meninges
Name the 12 cranial nerves
Olfactory I, Optic II, Oculomotor III, Trochlear IV, Trigeminal V, Abducens VI, Facial VII, Vestibulocochlear VIII, Glossopharyngeal IX, Vagus X, Accessory XI, Hypoglossal XII.
Which are the three layers of the meninges?
Dura mater, arachnoid, subarachnoid space.
What is another word for anterior?
Ventral
Which is the afferent pathway in the spinal cord?
The Dorsal horn
What is the cell body of a neurone also known as?
The soma
Can a nerve impulse travel down a demyelinated neurone?
Yes albeit much slower than a myelinated neurone.
Give an example of an unmyelinated neurone.
Nociceptive (pain) fibres
At what membrane potential do potassium channels open to repolarise the cell?
+40mV
Which nerve system can regenerate more easily?
The Peripheral nervous system
Which are the two sensory pathways?
The Dorsal column-medial lemniscus pathway +
Spinothalamic pathway
Which are the two motor pathways?
Lateral corticospinal tract + Vestibulospinal tract
Which pathway conveys fine- touch, vibration and discrimination?
The Dorsal column medial lemniscus pathway
What is the difference between the dorsal column medial lemniscus pathway and the spinothalamic pathway?
Dorsal column medial lemniscus = enters spinal column and leaves on same side.
Spinothalamic = enters spinal column and leaves on opposite side of the body.
What is the word for the same side of the body?
Ipsilateral
Is the vestibulospinal tract contralateral or ipsilateral?
Ipsilateral
What is the neuromuscular junction?
A specialised synapse between a motor neurone and a muscle fibre
What is the typical diameter of the chemical synapse?
10-50 nm
‘Bouton’ refers to….
the pre-synaptic terminal
Which is the neurotransmitter for voluntary striated muscle?
Acetylcholine
What is electromyography?
The recording of action potentials within muscle fibres.
Define twitch
A short, sudden jerking or convulsive movement
Define tetanus
Prolonged contraction of a muscle due to a rapidly repeated stimuli.
Define summation
The additive effect of several electrical impulses at a neuromuscular junction.
Define electromyogram
Measures action potentials in skeletal muscle fibres.
What is the difference between intracellular and extracellular electromyography?
Intracellular = one electrode inside the cell and the other outside. Extracellular = both electrodes are outside of the muscle fibre.
What does GABA break down to?
Succinate semialdehyde
Explain how a resting membrane potential can arise across a selectively permeable membrane.
Diffusion of ions through a selectively permeable membrane
=generates membrane potential.
What is the typical resting potential of a neuron?
-70mV
Define electrochemical equilibrium
When electrical forces balance diffusion forces and prevent further diffusion across membranes.
Define equilibrium potential
The potential at which the electrochemical equilibrium has been reached. It prevents further diffusion.
What is the Nernst equation?
Used to calculate equilibrium potential.
What is the typical value of potassium inside and outside of the cell?
Intracellular K+ = 150mM
Extracellular K+ = 5mM
What is the typical value of sodium inside and outside of the cell?
Intracellular Na+ = 10mM
Extracellular Na+ = 150mM
Why does potassium exert a stronger affect than sodium on the resting membrane potential?
The membrane is more permeable to potassium.
What is an action potential?
Nerve impulses which travel along an axon upon stimulus in an excitable cell.
Define threshold
Once this potential is reached an action potential is triggered
Define refractory period
Absolute = No action potential can be stimulated - even with a strong stimulus. Na+ inactivation gate is closed. Relative= Na+ inactivation gate is open. The Na+ activation gate is closed meaning a stronger stimulus is needed, but if strong enough CAN generate action potential.
Refractive state = unresponsiveness to threshold depolarization
Define ‘all or nothing’ behaviour
Once triggered, a full sized action potential occurs
Define depolarisation
The department becomes less negative.
Define repolarisation
The department becomes more negative - usually caused by K+ efflux.
Define hyperpolarisation
The department becomes more negative than at its resting membrane potential.
Define saltatory conduction
Action potential jumps across nodes of ranvier enabling faster propagation of nerve impulses.
What is a voltage-gated channel?
A channel which allows ions through and is activated upon sodium influx.????????
Across an axon, do GRADED potentials continue at the same speed?
No. GRADED potentials work via decremental spread meaning they become less powerful further along the axon. Action potentials maintain speed.
What is positive feedback?
A continuous loop e.g. When there is depolarisation of a cell, sodium channels are activated increasing Na+ permeability allowing Na+ influx which causes further depolarisation.
How does the cell return to its resting membrane potential after hyperpolarisation?
Some K+ channels close, making the cell a little less negative.
Recall the size and duration of a neuronal action potential
Large diameter, myelinated = 120m/s
Smaller diameter, unmyelinated = 1m/s
What is regenerative conduction
The positive feedback loop between sodium voltage gated channel activation, increased sodium permeability, sodium influx and depolarisation of the cell.
Name x3 conditions which may affect conduction along the axon
Demyelination e.g. multiple sclerosis
Smaller axon diameter
Drugs, cold, anoxia
What is one key thing to remember about the upstroke of the action potential?
Both Na+ and K+ channels are open but the Na+ influx is QUICK whereas K+ influx is slow. More Na+ coming in than K+ leaving.
When is the membrane potential closer to the sodium equilibrium potential?
During depolarisation (the upstroke).
When is the membrane potential closer to the potassium equilibrium potential?
During repolarisation/ hyperpolarisation.
How many cervical, thoracic, lumbar, sacral and coccyx vertebrae are there?
7, 12, 5, 5, 4
How many spinal vertebrae are there in total?
33
How many cervical, thoracic, lumbar, sacral and coccyx nerves are there?
8, 12, 5, 5, 1
How many spinal nerves are there in total?
31
What are the functions of the dorsal and ventral horns?
The dorsal horn receives sensory information from the body. The ventral horn carries signals away from the CNS and toward the limbs/ organs.
What is one way to check if an individual has a higher intracranial pressure?
Check behind the eyes for papilloedema.
What is the level of a lumbar puncture?
Adults: L3-L4
Children: L4-L5
What is the difference between bacterial and viral meningitis?
Bacterial = High protein, low glucose Viral = Low protein, normal/high glucose
How would you distinguish between an epitdural and subdural haemorrhage?
Epidural is bleeding between the dura mater and the skull.
Subdural is bleeding between the dura mater and the arachnoid.
Epidural is arterial (expands with arterial blood), subdural is venous.
How may hydrocephalus be treated?
Drain cerebrospinal fluid from the head.
Which part of the brain passes through the foramen ovale?
The spinal cord.
The dorsal ramus supplies which region?
The posterior region
The ventral ramus supplies which region?
The anterior region
What is the difference between myotomes and dermatomes?
Dermatomes have a single supply whereas myotomes have more than one supply.
If there were a lesion at the mixed spinal nerve would you see weakness or paralysis?
Weakness; not paralysis as the myotome has more than one supply.
Paralysis is seen in what type of lesion?
A lesion affecting the motor (ventral) nerve.
Weakness is seen in what type of lesion?
A lesion affecting the sensory (dorsal) nerve
What do you find a lot of in the node of ranvier?
Na+ channels
Describe the sequence of peripheral denervation to regeneration.
Normal - destroyed axon and arriving phagocytes - demyelination and axon budding off ‘sprouts’ to regeneration of axon to myelin reformation.
Which part of the brain lies in the anterior cranial fossa?
The frontal lobe
Which part of the brain lies in the middle cranial fossa?
Parietal and temporal lobe
Which part of the brain lies in the posterior cranial fossa?
Brainstem and the cerebellum
Which part of the brain lies directly above the body of the sphenoid bone?
The hypothalamus
Which part of the brain passes through the foramen magnum?
The spinal cord
Nifedipine is an example of what type of drug?
Calcium channel antagonist
Which channel is responsible for bringing the ventricular myocyte fully back to its resting membrane potential?
IK1.
What is a difference between T type and L type calcium channels?
T type channels are activated at more negative potentials than L type channels.
Name x3 differences between the action potential in the SAN compared with the ventricular myocyte.
SAN does not have a resting membrane potential.
Ventricular myocyte has IK1 channel, ventricular myocyte does not.
Depolarisation in SAN is mainly due to Ca2+, in ventricular myocyte = mainly due to Na+ and so slower upstroke in SAN.
Chronotropy relates to what?
Heart rate
Inotropy relates to what?
Contractility
Lusitropy relates to what?
Myocardial relaxation
What is special about the atrioventricular node?
It allows a small delay of conduction following atrial contraction.
What are the function of gap junctions within the cardiac myocytes?
Allow current to easily leak from cell to another and reduces membrane resistance between cells.
Intercellular communication and impulse conduction rely on what?
Gap Junctions
The brainstem contains how many nuclei of the cranial nerves?
10 out of the 12.
Which part of the brain is affected in Parkinson’s Disease?
The substantia nigra of the midbrain.
What is the role of the thalamus?
Emotion and motor reponse
What is the role of the hypothalamus?
Regulates temperature, hunger and thirst.
What are the 3 layers of the meninges from inward out?
Pia mater, (subarachnoid space), Arachnoid mater, Dura mater
Which structure produces the cerebrospinal fluid?
The choroid plexus
What is the difference between the cerebrospinal fluid and plasma?
The CSF has lower protein content, lower glucose and lower pH. CSF also has higher Cl- and higher Mg2+.
Name x4 functions of the Cerebrospinal fluid.
Cushioning, nutrition, removal of waste and immune function.
What is a ganglion?
A collection of cell bodies.
What are the two divisions of the motor response in the peripheral nervous system?
The somatic and the autonomic nervous system.
The propagation speed of a nerve impulse is related to its stimulus strength. True or false?
False.
Why do myelinated fibres conduct nerve impulses faster?
Larger fibres?
Myelinated fibres conduct nerve impulses faster due to saltatory conduction. Larger fibres conduct nerve impulses faster due to there being less resistance.
Order the nerve fibres in order of size and therefore propagation speed.
A > B > C. A is the fastest at 130m/s. B = 15m/s, C = 2m/s.
What are the 3 divisions of the autonomic system?
Sympathetic, parasympathetic and enteric
What is the function of the autonomic system?
Maintains homeostasis of internal environment and involuntary control of viscera and glands.
In the ANS, a sequence of how many neurones are there between the CNS and innervated structure?
2; Preganglionic neuron to ganglion to postganglionic fibre.
Which CNS structure provides high level regulation of autonomic activity?
The hypothalamus
Where do neurones synapse in the sympathetic system?
At the paravertebral ganglia
Where do neurones synapse in the parasympathetic system?
At the ganglia close to the organ in which they innervate.
Where is there NO synapse for sympathetic innervation?
The adrenal gland
Where along the spinal cord do the pre-ganglionic neurons emerge from in the sympathetic system?
The thoracic and upper lumbar regions. (T1-T12) and (L1-L3).
Which structures are innervated for the sympathetic and parasympathetic system?
The eye, blood vessels, glands, mucosal membranes, thoracic, abdominal and pelvic viscera.
Which has a longer pre-ganglionic neurone - the sympathetic or parasympathetic?
The parasympathetic
From what spinal cord segments do the preganglionic parasympathetic neurones emerge from?
Cranio-sacral regions. (S2-S4).
Which cranial nerves are associated with the parasympathetic nervous system?
The vagus nerve and the glossopharyngeal nerve
Which are the cranial nerves?
III, VII, IX and X – Oculomotor, facial, glossopharyngeal and vagus.
Why do you think the anatomy of the symp. & parasymp. nervous systems differs?
The sympathetic system has a mass response around the body whereas the parasympathetic response is more localised and discrete which conserves energy.
What are the ramus communicans?
The ramus communicans connects the spinal nerves to the sympathetic chain.
What is the difference between the white and grey ramus communicans?
White ramus communicans is associated with the pre-ganglionic axon in the sympathetic system
Grey ramus communicans is associated with the post-ganglionic axon in the sympathetic system
Which is cranial nerve III?
Oculomotor nerve
What is ‘accomodation’ within the eye?
A reflex action of the eye where lens and pupil shape change.
What is ‘accomodation’ within the eye?
A reflex action of the eye where lens, ciliary muscle and pupil shape change.
Where does the posterior ramus innervate?
The back
Which is larger - the anterior or posterior ramus?
The posterior ramus
Where does the anterior ramus innervate?
The rest of the body apart from the head - which is innervated predominantly by cranial nerves.
Give x5 functions of the vascular endothelium.
Vascular tone Prevents thrombosis Absorption and secretion Barrier Growth
Where does the sensory neuron derive from?
Neural crest cells
Which fibres are unmyelinated?
C fibres.
The UMN is part of which system compared with the LMN?
UMN = central nervous system LMN = peripheral nervous system
Where do Lower motor neurones (LMN) derive from?
The basal plate
The peripheral nervous system consists of how many nerves?
43; 12 cranial nerves + 31 spinal nerves.
How many neurones in the ANS compared with the SNS?
Autonomic nervous system = 3
Somatic nervous system = 2
Where does the hypothalamic nuclei go to?
Either the spinal cord or the brainstem nuclei.
In which nerve is no ganglia found - only a pre-synaptic and post-synaptic neurone?
The vagus nerve
From where do pre-synaptic neurones derive?
The basal plate (in the spinal cord).
From where do post-synaptic neurones derive?
The neural crest
