Flashcards in Neurology Deck (85):
What are the functions of the medulla oblongata
Vasomotor centre located here, controls a lot of autonomic life functions – heart rate, respiratory rate, blood pressure. The cardiovascular centre is here.
What are the functions of the pons?
Is latin for bridge, it is the bridge between the midbrain and the medulla. It relays signals between the midbrain and the medulla, which ultimately leads signals to the cerebral cortex.
What are the functions of the midbrain?
Involved in auditory signaling and relaying and has a role in eye movement.
What are the functions of the thalamus?
Part of the diencephalon. It is the final common pathway for sensory information, it is a sort of relay centre. It is not active whilst you are sleeping.
What are the functions of the hypothalamus?
Part of the diencephalon. Has a neural and portal system connecting it to the pituitary gland. It is a neuroendocrine organ and is in charge of a lot of homeostasis. It produces ADH and oxytocin which is then released from the posterior pituitary. It releases GnRH, Thyrotropin releasing hormone, Corticotropin releasing hormone, Growth hormone releasing hormone.
What are the functions of the pituitary gland?
Posterior pituitary releases Oxytocin and Vasopressin/ADH
Anterior pituitary releases prolactin, TSH, FSH, LH, Corticotropin hormone, GH
What are the functions of the cerebellum?
Unconscious proprioception, it is the executive centre for movement. It regulates your movement. Size matters here.
What are the functions of corpus callosum?
Connects the two cerebral hemispheres.
What are the functions of the ventricles?
Part of the circulation system of the CSF, cushions the brain.
Within each ventricle is a choroid plexus that contains ependymal cells which produce CSF.
What are the functions of internal capsule?
Houses axons of motor neurons
Contains all the pathways that allow information to be transferred between the cerebral cortex and the spinal cord, brain stem and subcortical structures (thalamus etc.).
What are the functions of the limbic system?
Emotion, behaviour, motivation, long-term memory
What are the main lobes of the brain and what do they do at large?
Frontal lobe: site of primary motor cortex, site of higher thinking/cognition, involved in personality
Parietal lobe: site of primary sensory cortex, involved in processing sensory information regarding parts of the body as well as interpreting visual information, language and mathematics.
Temporal lobe: holds the primary auditory cortex, high level auditory processing
Occipital lobe: visual processing, contains the primary visual cortex
Where are the primary motor and sensory cortices?
Primary motor cortex: pre-central gyrus, in frontal lobe anterior to central sulcus.
Primary sensory cortex: post-central gyrus, in parietal lobe posterior to central sulcus.
Where are Wernicke’s and Broca’s areas? What sort of aphasia would result due to a lesion in each of these areas?
Broca’s aphasia is an expressive aphasia – can understand and interpret speech but cannot make words to reply.
Wernicke’s aphasia is a receptive aphasia – can talk fluently but make no sense, cannot make coherent replies
What branches of the circle of Willis mainly arise from the internal carotid arteries?
Middle cerebral arteries and Anterior cerebral arteries.
What branches of the circle of Willis mainly arise from the Vertebral arteries which then form the Basilar artery?
Posterior cerebral arteries
What arteries do vertebral arteries arise from?
Blood from the superior saggital sinus, inferior sagittal sinus and great cerebral vein drain into the confluence of sinuses and then what major vein?
Internal jugular vein
Between what layers of the dura mater is the superior sagittal sinus?
The superior sagittal sinus is between the periosteal and meningeal layers of the dura mater
What sort of cellular junctions comprise the blood brain barrier?
What is the name of the structures that make CSF?
What are some of the main functions of CSF?
Protects, nourishes brain, removes metabolites, contains chemical messengers, it’s composition is similar to blood plasma, only that it has significantly less protein in it. High levels of protein in CSF can be indicative of infection.
Describe how CSF is circulated in the ventricular system.
CSF is produced in the choroid plexus(es)
It goes from the lateral ventricles to the 3rd ventricle via the interventricular foramen. From the 3rd ventricle it enters the 4th ventricle via the cerebral aqueduct. From the 4th ventricle it enters the subarachnoid space via the central canal, from the subarachnoid space it enters the venous system via subarachnoid granulations in the superior sagittal sinus.
What are the two cranial nerves that originate in the cerebrum?
Olfactory and optic nerves originate in the cerebrum.
What are the two cranial nerves that originate in the midbrain?
Oculomotor and trochlear nerves originate in the midbrain.
What are the four cranial nerves that originate in the pons?
Trigeminal, Abducens, Facial and Vestibulocochlear nerves originate in the pons.
What are the four cranial nerves that originate in the medulla?
Glossopharyngeal, Vagus, Accessory and hypoglossal originate in the medulla.
What are the two cranial nerves that are purely sensory?
The olfactory and optic cranial nerves are the only two cranial nerves that are purely sensory in function.
How does the superior oblique muscle move the eye?
The superior oblique moves the eye downwards and internally rotates it. A palsy to the trochlear nerve which innervates the superior oblique muscle would lead to an upwards and outwards facing eye.
What would a palsy in the 6th cranial nerve look like?
The 6th cranial nerve is the abducens nerve which innervates the lateral rectus muscle, which abducts the eye away from the midline. A palsy in the 6th cranial nerve would therefore result in an eye that is unable to be abducted past the midline.
What are the 3 sensory branches of the trigeminal nerve called? (the dermatomes on the face) What motor function does the trigeminal nerve fulfill?
Opthalmic, Maxillary and Mandibular branches. It innervates the muscles of mastication.
Describe the motor, sensory and taste innervation of the tongue.
Motor: all motor innervation of the lingual muscles is by the hypoglossal (CN XII) nerve, apart from the palatoglossus muscle which receives vagal innervation (CN X).
Sensory and taste to the posterior 1/3 of the tongue is by the glossopharyngeal nerve (CN IX).
Sensation to the anterior 2/3 of the tongue is by the lingual branch of the trigeminal nerve (CN V).
Taste to the anterior 2/3 of the tongue is by the lingual branch of the facial (VII).
At what vertebral level does the spinal cord end and what does it form at this point?
Spinal cord ends at L1-L2 vertebral level and forms the conus medullaris, then the cauda equina.
There are two enlargements of the spinal cord, what are these enlargements called and what arises at these enlargements?
Cervical and lumbar enlargements. The brachial plexus arises at the cervical enlargement and the sacral and lumbar plexi arise at the lumbar enlargement.
What are the three main layers of the spinal meninges?
Pia mater, Arachnoid mater, Dura mater
What spinal nerves arise from the cauda equina?
What blood vessels supply the spinal cord?
Anterior spinal artery, posterior spinal arteries, anterior and posterior segmental medullary arteries
How many neurons are involved in most motor and sensory pathways?
Motor: 2 neuron pathway
Sensory: 3 neuron pathway
What is the main motor spinal tract? Where does it decussate?
Main motor tract is the lateral corticospinal tract. That carries about 85% of motor information, whereas the anterior corticospinal only carries about 15% of it.
What spinal tract carries sensory information about delicate touch and proprioception? Where does it decussate?
Dorsal Column-Medial Lemniscus tract. It decussates in the medulla.
There are two parts to the DCML tract, what are these two columns called and what signals do they carry?
Fasciculus gracilis – carries signals from the lower limb (it is the narrower part)
Fasciculus cuneatus – carries signals from the upper limb (it is the wedge-shaped larger part)
What spinal tract carries sensory information about pain, temperature and crude touch? Where does it decussate?
The spinothalamic tract. It decussates at spinal level.
What is a brown-sequard spinal lesion?
A Brown-sequard lesion is a lesion to half of the spinal cord down (with the cord being split in a sagittal fashion)
On what sides would you lose pain, temperature and crude touch?
Pain, temperature and crude touch sensation would be lost on the opposite side below the lesion site as the spinothalamic tract which conveys this sensory information decussates at spinal level.
On what sides would you lose proprioception, motor function and delicate touch?
Proprioception, motor function and delicate touch would be lost on the same side below the lesion site as the DCML and corticospinal tracts which carry this information have already decussated higher up, in the medulla.
Name 3 key clinical features of upper and lower motor neuron lesions.
Up-going plantars (Babinski's sign positive)
Increased muscle tone
Name 3 key clinical features of an upper motor neuron lesion
Up-going plantars (Babinski's sign positive)
Increased muscle tone
Name 3 key clinical features of a lower motor neurone lesion
Downgoing plantars (Babinski's sign negative)
Decreased muscle tone/wasting
What is syringomyelia? What symptoms would it present with?
A chronic and progressive disease in which longitudinal cavities form in the cervical region of the spinal cord around the central canal. It normally presents with a cape-like distribution of loss of pain and temperature sensation, because it interferes with where the spinothalamic tract decussates at those spinal levels.
Why are not all neurons myelinated?
Myelination is metabolically expensive – only neurons that need to relay very quick signals need to be myelinated.
What sort of pain do myelinated A fibres and unmyelinated C fibres carry?
Myelinated A fibres (remember ‘a’ for acute) carry acute, sharp pain.
Unmyelinated C fibres (remember ‘c’ for chronic) carry slow, dull, burning pain
What cells form the myelin sheaths in the CNS and PNS?
Ogliodendrocytes form the myelin sheaths in the CNS
Schwann cells form the myelin sheaths in the PNS.
What are some of the functions of glial cells?
There are many different subtypes of glial cells so they can have many different functions. Glial cells are very small cells that stain very purple on HE staining. They perform such functions as CSF production, removal of pathogens and debris, reuptake of neurotransmitters, myelination of axons, control inflammation in the brain, phagocytose microbes. Astrocytes are special types of glial cell that provide nutrients for neurons, comprise the blood brain barrier and maintain a proper chemical environment in the brain.
Would loss of sensation be ipsilateral or contralateral if the lesion of the neuron pathway is above or below the level of decussation?
If lesion is below the level of decussation, sensory loss will be ipsilateral to the lesion site. If lesion is above the level of decussation, sensory loss will be contralateral to the lesion site.
What is meant by the terms dysphasia, dysarthia, dysphonia, hemiplegia and hemiparesis?
Dysphasia: problems with the comprehension or generation of language
Dysarthia: problems with the MECHANICAL CREATION of words, can be caused by problems with the NMJ, pharyngeal muscles, motor pathways
Dysphonia: problems with sound production i.e. larynx problems, problems with the vocal cords/nerves to them
Hemiplegia: paralysis to one side of body
Hemiparesis: weakness to one side of body
What is the main excitatory neurotransmitter?
Glutamate is the main excitatory neurotransmitter
What are the main inhibitory neurotransmitters?
GABA is the main inhibitory neurotransmitter, along with glycine
What hemisphere of the brain is dominant in most people?
THE LEFT HEMISPHERE IS DOMINANT IN MOST PEOPLE
What shape would a subdural haemorrhage have on CT? Subdural haemorrhages and extradural haematomas are both caused by trauma, other than shape of blood pooling on CT, how can they be distinguished from one another in a history?
Subdural haemorrhage would be crescent shaped on CT and extradural would be convex shape. A subdural haemorrhage can be acute or chronic. Chronic ones can be much later on presentation, often weeks after relatively minor trauma (common in older people). Extradural haematomas often present with a lucid period immediately after trauma, before symptoms become evident.
Damage to what spinal nerve causes an absent Achilles/ankle jerk reflex?
Why is ophthalmic shingles a medical emergency?
Because it can damage the optic nerve and lead to loss of sight.
What is the layer called that surrounds a nerve fibre (not a neuron!)?
What neurotransmitter is a precursor to GABA?
Glutamate is a precursor to GABA.
Glutamate decarboxylate does this conversion.
What is the initial substrate in serotonin production?
Tryptophan is the initial substrate in serotonin production.
What is the role of alpha-2 adrenergic receptors?
They are found in the peripheral sympathetic NS and presynaptic Alpha-2 receptors inhibit further release of noradrenaline, like a negative feedback mechanism.
What enzyme regulates the presynaptic stores of catecholamines? Where is it stored and released from?
Monoamine oxidase is an enzyme that regulates presynaptic stores of catecholamines. It controls the levels of dopamine and noradrenaline. It is released from the post ganglionic pre-synaptic neuron in the sympathetic NS.
What is adrenaline made from?
Adrenaline is made from noradrenaline. They have a similar structure so they can both act at the same receptors.
What is noradrenaline made from?
Noradrenaline is made from dopamine.
Why does hyponatraemia cause a loss of consciousness?
It can cause cerebral oedema, water enters brain cells by osmosis, which can cause loss of consciousness and death.
Name a common enzyme inducer (drug name) and what does it do to the activity of warfarin?
Carbamazepine is a common enzyme inducer (it is an anti-epileptic drug). It decreases the activity of warfarin as it induces the enzymes that metabolise warfarin, meaning less active drug remains in the body so it has less of a therapeutic effect.
Why can B12 deficiency cause a neuropathy?
Vitamin B12 plays an important role in myelination. Lack of vitamin B12 can cause a lack of myelination so neuropathy can result.
What is the main factor that establishes and maintains a neuron’s resting potential?
K+ leaving cells.
Why does a sensory block occur before a motor block in anaesthesia?
A sensory block occurs before a motor block in anaesthesia because thick, myelinated motor fibres are harder to anaesthetize whereas thinner, unmyelinated sensory fibres are easier to anaesthetise.
If the left knee jerk is absent and there is some sensory loss over the left medial calf, what vertebral disk do you expect could have herniated?
The disc between L3 and L4 which will compress the L4 nerve root.
Under what circumstances would lumbar puncture be contraindicated?
If the patient has raised intracranial pressure.
Mr Truro, a 60 year old retired schoolteacher, has attended his local GP complaining of a "droopy eyelid". On examination you find a right sided ptosis and, upon lifting the eyelid, you find that the right eye is gazing down and to the right.
Which cranial nerve has most likely been affected in this situation?
A 72 year old woman visits you, her GP, complaining of diplopia (double vision) when walking down stairs. You carry out a cranial nerve examination and note that her left eye has a limited range of movement inferiorally and medially, but other eye movements are normal. When you test her diplopia, she reports that double vision is worst when looking down to her right.
What is the most likely cause of the diplopia?
A 52-year-old woman woke in the morning with a severe headache, of greater intensity than she had ever had before. She noticed that she could not raise her right eyelid. On examination she had a complete right-sided ptosis, an inability to adduct the right eye, and a dilated right pupil that was not responsive to light.
What condition best explains her eye signs?
Oculomotor nerve lesion
A 55 year old female presents to your GP surgery complaining of sudden attacks of excruciating, lightening-like jabs of facial pain. The pain can last for 15 minutes, and only affects one side of her face. She informs you that the pain is so intense that her husband has noticed her wincing. Which nerve is most likely to be affected?
What sort of cranial haemorrhage would present with a “thunderclap headache” like being hit over the head with a baseball bat?
What percentage of stoke's are ischaemic?
Through which structure does the vertebral artery travel to the brain?
What artery is most likely to have been occluded in a stroke?
Middle cerebral artery
What is the arterial supply to the cervical spine? Is the cervical spine equally supplied by the posterior and anterior vertebral arteries?
No, the anterior vertebral artery supplies 2/3 of the spinal cross-section
If the anterior vertebral artery becomes occluded, anterior spinal syndrome can result
- wipes out corticospinal tract and spinothalamic tract