History, Pathology, Physiology Flashcards by Linglee Downey

Where do parasympathetic preganglionic nerve fibres originate?

cranio-sacral

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Where do sympathetic preganglionic nerve fibres arise?

Thoracolumbar

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What neurotransmitters are released from preganglionic fibres of sympathetic and parasympathetic nerves?

ACh bind nicotinic ACh receptors

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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

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What are the 2 functional classes of sympathetic ganglion neurons?

paravertebral ganglia (source of vasoconstrictor neurons)

- prevertebral ganglia (innervate non-vascular smooth muscle)

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What are the locations of parasympathetic cranial preganglionic neurons?

Edinger-westfal nucleus in midbrain
Salivary nuclei
Dorsal motor nucleus of vagus and nucleus ambiguous

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What is white matter?

Myelinated axons and glia

Oligodendrocytes give fat the white colour

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What is grey matter?

Neuron somata, dendrites and glia

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What is the appearance of white matter in a T2-weighted image?

White matter appears darker than grey matter

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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

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What splits the cerebral hemispheres?

Longitudinal fissure

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What divides frontal lobe from parietal lobe?

central sulcus

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What structure links the left and right hemispheres?

corpus callosum

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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)

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Where do the spinal nerves end?

Level of L1/2

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Where is CSF resorbed?

Major veins at arachnoid granulations in the subarachnoid space

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What dural petition divides the cerebral hemispheres?

Falx cerebri

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Which dural petition separates cerebellum from occipital lobes?

Tentorium cerebelli

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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

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What are the 3 vesicles of the neural tube and what do they form?

Prosencephalon - forebrain
Mesencephalon - midbrain
Rhombencehalon - hindbrain

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What structures does the prosencephalon split into?

Telencephalon and diencephalon

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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