History, Pathology, Physiology Flashcards
Where do parasympathetic preganglionic nerve fibres originate?
cranio-sacral
Where do sympathetic preganglionic nerve fibres arise?
Thoracolumbar
What neurotransmitters are released from preganglionic fibres of sympathetic and parasympathetic nerves?
ACh bind nicotinic ACh receptors
What neurotransmitters are released from postganglionic sympathetic and parasympathetic nerve fibres?
Sympathetic postganglionic fibres release NA or ACh
Parasympathetic postganglionic fibres release ACh
*ACh binds muscarinic ACh receptors
What are the 2 functional classes of sympathetic ganglion neurons?
- paravertebral ganglia (source of vasoconstrictor neurons)
- prevertebral ganglia (innervate non-vascular smooth muscle)
What are the locations of parasympathetic cranial preganglionic neurons?
Edinger-westfal nucleus in midbrain
Salivary nuclei
Dorsal motor nucleus of vagus and nucleus ambiguous
What is white matter?
Myelinated axons and glia
Oligodendrocytes give fat the white colour
What is grey matter?
Neuron somata, dendrites and glia
What is the appearance of white matter in a T2-weighted image?
White matter appears darker than grey matter
What is the anatomical direction of dorsal in the CNS?
In brainstem and spinal cord, dorsal is behind
In midbrain, dorsal structures are toward top of head
What splits the cerebral hemispheres?
Longitudinal fissure
What divides frontal lobe from parietal lobe?
central sulcus
What structure links the left and right hemispheres?
corpus callosum
What is the anatomy of the spinal cord?
Core is grey matter surrounded by white matter
Dorsal horns - incoming sensory information (ascending pathways)
Ventral horns - outgoing motor information (descending pathways)
Where do the spinal nerves end?
Level of L1/2
Where is CSF resorbed?
Major veins at arachnoid granulations in the subarachnoid space
What dural petition divides the cerebral hemispheres?
Falx cerebri
Which dural petition separates cerebellum from occipital lobes?
Tentorium cerebelli
How many closure events of neural tube are there?
Failure of zone closures is associated with what developmental defects?
5 independent closure events
failure of zone 5 closure = spina bifida
failure of zone 2 closure = anencephaly
What are the 3 vesicles of the neural tube and what do they form?
Prosencephalon - forebrain
Mesencephalon - midbrain
Rhombencehalon - hindbrain
What structures does the prosencephalon split into?
Telencephalon and diencephalon
What is the neural crest and what are its derivatives?
Cells at the top of the neural tube migrate away from neural tube
Form peripheral NS - DRG, Symp and parasymp ganglia
Melanocytes
Muscle cartilage and bone (skull, jaw, face, pharynx)
What is the consequence of no formation of the floor plate?
motor neurons don’t form
Which cells guide migration in the cortex?
Radial glia
What cells direct spinal cord development?
Notochord
What are possible consequences of damage to central axons/neurons?
- neurons die
- neurons sprout and make new local connections
- neurons not able to regrow
Why are central neurons/axons unable to regenerate?
Glial scar inhibits regrowth (oligodendrocytes)
What is Wallerian degeneration?
degeneration of axon and myelin sheath of peripheral nerve below site of injury
macrophages phagocytose
muscle fibre atrophy
What happens 3 weeks post-injury to peripheral nerve?
Schwann cells proliferate and form compact cord
growing axons penetrate Schwann cell cord
*Schwann cells support axon regrowth
What can happen is peripheral nerves unsuccessfully regenerate?
neuroma formation - bundle of nerve fibres which can cause pain or unusual sensations
What are mechanisms that inhibit CNS neural regeneration?
- astrocytic gliosis (forms barrier between undamaged tissue and injury site)
- myelin proteins (Rho signalling inhibits axon growth)
- upregulation of axon guidance molecules (Rho kinase pathway causes axon to retract)
What processes lead to secondary neuronal injury?
- degenerative insults (ischaemia, Ca++ influx, ROS, excititoxicity)
- immune infiltration and microglial activation
- inflammatory mediators
Where is memory stored?
hippocampus in medial temporal lobe
How is short-term memory formed?
Insertion of AMPA receptors
Enhanced presynaptic release
How is long-term memory formed?
Protein synthesis
Structural changes
What are the 2 main subtypes of cerebral oedema?
- Vasogenic (BBB disruption with increased vascular permeability)
- Cytotoxic (secondary to injury)
What are the 3 sites of herniation?
- subfalcine (under falx cerebri)
- transtentorial
- uncal (cerebellum through foramen magnum)
What pathological processes are involved in stroke?
- infarction (75%)
- intracerebral haemorrhage (20%)
- subarachnoid haemorrhage (5%)
What are risk factors for cerebral infarction?
- age
- hypertension
- CVD
- dyslipidaemia
- DM
- smoking, obesity
What is cerebral infarction?
necrosis of cerebral tissue in a particular vascular distribution due to vessel occlusion or systemic hypotension
What are mechanisms of cerebral infarction?
- inadequate supply of blood due to pump failure
- inadequate supply of blood due to narrowed vessel lumen (atherosclerosis, thrombosis, vessel thickening)
- vessel occlusion by embolus
What are cardiac causes of cerebral infarction?
- non-bacterial thrombotic endocarditis (rheumatic fever, hypercoagulable states, abnormal valve formation)
- probe-patent interatrial septum due to increased RA pressure or abnormal valve formation
What is a common site for atherosclerosis?
CCA bifurcation
What sort of necrosis occurs in the brain?
Liquifactive necrosis
Macrophages phagocytose dead tissue which eventually causes cystic changes
What is the cause of a lacunar infarct?
- small vessel occlusion leads to small infarct
- usually due to small vessel disease ad hypertention
- lacunar infarct can lead to cystic changes
What are causes of intracerebral haemorrhage?
- hypertensive small vessel disease
- cerebral amyloid angiopathy
- blood disorders
- tumour
- drugs
What particular sites do hypertensive haemorrages tend to occur?
- basal ganglia and thalamus
- white matter
- cerebellum
- pons
What is cerebral amyloid angiopathy?
-deposition of A beta amyloid in walls of superficial blood vessels above the tentorium
If there are multiple haemorrhage sites in the brain, what is the most likely cause?
Coagulopathy issue
Hypertension not likely to cause multiple sites
What are causes of subarachnoid haemorrage?
- rupture of berry aneurysm
- extensive intracerebral haemorrage
What are risk factors for berry aneurysm formation?
- adult females
- polycystic kidney disease
- coarctation of aorta
- hypertension
- smoking and alcohol
Where do berry aneurysms typically occur?
sites of congenital weakness at arterial bifurccations
more likely in anterior circulation
bifurcation site of MCA
junction of ICA and posterior communication artery
anterior communicating artery
What are complications of aneurysm rupture?
- subarachnoid haemorrhage
- cerebral oedema and increased ICP
- vasospasm and infarction
- ventricular obstruction (hydrocephalus)
What cells induce ventral horn motor neurons?
Floor plate
