Cells and Tissues of the Nervous System Flashcards by Adam Davie

Describe the divisions of the nervous system

CNS (brain &amp; spinal cord) ->
PNS (cranial &amp; spinal nerves) ->
Sensory (afferent) 
Motor (efferent) ->
Somatic Motor
Autonomic -> 
Sympathetic
Parasympathetic

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Describe neurons

Structural and fictional units of the NS. They are excitable, their impulses are carried as action potentials

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Describe glial cells

Non-excitable supporting cells, they are much smaller than neurons

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What is the basic anatomy of a typical neuron?

Contains multiple dendrites and one axon

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What are the cell organelle of a neuron?

Mitochondria, rER, diffuse Golgi apparatus

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Is the metabolic rate of neurons high or low?

High

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What is the cytoplasm in the cell body called?

Perikaryon

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What is the cytoplasm in the axon called?

Axoplasm

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Are neurons amitotic?

Yes

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What is the determining factor in the regrowth of axons?

If only the axons are damaged, there is potential for them to grow back, but if the corresponding cell body is damaged, the axons cannot regrow

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What is the function of the myelin sheath?

To increase conduction speed across axons

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How are the myelin sheaths formed?

PNS - Schwann cells

CNS - Oligodendrocytes

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Describe the process of axon myelination

Schwann cells wrap around the axons
A mesaxon is formed
The cytoplasm of the Schwann cell gets extruded leaving only the cell membrane

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Outline the features of Multiple Sclerosis

Loss of myelin sheath in patches, results in abnormal axon conduction
Cause is unknown (idiopathic)
MRI shows whitish plaques of demyelination
Prognosis variable
Scotland has the highest incidence in the world

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What are the three kinds of neuron?

Multipolar, bipolar, pseudounipolar

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Where are bipolar neurons found?

Olfactory mucosa, retinal nerve fibres

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What type of neurons are sensory?

Pseudounipolar

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What type of neurons are interneurons and motor neurons?

Multipolar

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In what direction does the impulse travel in in the multipolar nerurons?

From the dendrites via the cell body and along the axon

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In wat direction do the impulses travel in unipolar neurons?

From the dendrites along the axon to the cell body and then along the rest of the axon

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What are the glial cells of the PNS?

Schwann cells

Satellite cells

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What is the function of satellite cells?

Surrounding the neuronal cell bodies in the PNS

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What are the glial cells of the CNS?

Ependymal cells
Microglia
Oligodendrocytes
Astrocytes

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What is the function of astrocytes in the CNS?

Have end feet which surround synapses and capillaries. They help in potassium buffering

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What is the function of the oligodendrocytes in the CNS?

Myelination

What is the function of the ependymal cells in the CNS?

Lining vesicles

What are the functions of the microglia in the CNS?

Phagocytosis, scar tissue formation

What are myelin sheaths made of?

Cell membrane

What are cell membranes made of?

Lipids (fats)

What colour are fats?

Yellow/White

How do myelinated axons together look in terms of colour?

White

What colour do bundles or neurones/non-myelinated axons look?

Grey

What do diffuse bundles of cell bodies and non-myelinated axons in the CNS form?

Grey matter

What do localised collections of cell bodies and non-myelinated axons in the CNS form?

Nucleii

What do diffuse collections of myelinated axons in the CNS form?

White matter

What do localised collections of myelinated axons in the CNS form?

Tracts

What do myelinated axons in the PNS form?

Nerves

What do cell bodies in the PNS form?

Ganglia

Describe the formation of the nervous system

Surface ectoderm of the embryo develops into a thickening called a neural groove and eventually tube This goes on to form the nervous system

Describe the formation of the vesicles

When the neural tube is formed, it divides into three primary vesicles in week 4. It then divides further into two tertiary vesicles in week 5 These vesicles develop into the adult brain

What are the derivatives of the telencephalon (first two lateral vesicles)?

Cerebral cortex, basal ganglia

What are the derivatives of the Diencephalon? (third vesicle)

Thalamus, hypothalamus

What are the derivatives of the mesencephalon?

Midbrain

What are the derivatives of the metencephalon?

Pons, cerebellum

What are the derivatives of the myelencephalon? (fourth vesicle)

Medulla

What do the ventricles contain?

CSF

Describe the lateral ventricles

C-shaped cavities which lie in the cerebral hemispheres

What is the inter ventricular foramen?

Connects the lateral ventricles with the third ventricle, the cavity within the diencephalon

Where does the cerebral aqueduct lie?

In the midbrain

What shape is the 4th ventricle and where does it lie?

Diamond shaped, hindbrain

What is the inner layer covering of the CNS?

The pia mater, it is thin and vascular

What is the middle layer covering the CNS?

The arachnoid matter, it is spider-web like

What is the outer layer covering the CNS? What feature does it have?

The dura mater, it is thick and tough | Dural folds

What is the subdural space?

A potential space traversed by blood vessels penetrating into the CNS

What does the subarachnoid space contain?

CSF

What is CSF?

Fluid found in the ventricles and central canal, responsible in part for maintenance of intracranial pressure Also present between the pia and arachnoid coverings of the meninges

Where is CSF produced?

The choroid plexus

How is SCF absorbed?

By the arachnoid villa

What are the three layers of the meninges?

Dura mater Arachnoid mater Pia mater

What are the key folds of the dura?

Falx cerebri, tentorium cerebelli, falx cerebelli, diaphragma sellae

What is the blood brain barrier?

A protective mechanism that helps maintain a stable environment for the brain and prevents harmful amino acids and ions entering the bloodstream and blood cells from entering the brain

What is the BBB made up of?

Endothelium - tight junctions Thick basal lamina Foot processes of astrocytes

Where in the brain is the BBB absent?

Parts of the hypothalamus, posterior pituitary

What is the clinical significance of the BBB in terms of drugs?

Plays a major role in delivery to CNS. Drugs must be lipid soluble or use suitable vectors