Neural tissues Flashcards
In the brain, what is dorsal, ventral, rostral and caudal?
Dorsal = up
Ventral = down
Rostral = front
Caudal = back
Which outdated theory suggested the nervous system was a single continuous network?
Reticular theory
Which concept suggests the nervous system is made of discrete individual cells which are mutually dependent upon one another?
Neuronal doctrine
What is the general name of the 52 areas of the cortex with each area having a particular set of inputs and outputs?
Brodmann areas
What is Brodmann area 17?
Primary visual cortex
What is Brodmann area 4?
Primary motor cortex
What are Brodmann areas of the cortex determined by?
Histological architecture.
What are axon collaterals?
Rare axonal protrusions that provide modulation of cell firing.
Neurons receive and integrate incoming information from what?
Sensory receptors or other neurons.
How do neurons transmit information to other neurons or effector organs?
Chemically
Where on a neuron does integration and protein synthesis occur?
Soma/cell body
Where on a neuron does conduction and transport occur?
Axon
Where on a neuron does transmission occur?
Axon terminals/Synaptic terminals/Terminal boutons
Each neuron is a _____ entity with a ____ cell membrane.
Separate
Limiting
What type of morphology is this neuron?
Unipolar
What type of morphology is this neuron?
Bipolar
What type of morphology is this neuron?
Pseudo-unipolar.
There is one extension from cell body.
What type of morphology are these neurons?
Multipolar
What are the small protrusions on dendrites that form functional contacts with neighbouring axons?
Dendritic spines.
Dendrites are branched protoplasmic extensions. What is their primary role?
To propagate the electrochemical input from other cells to soma.
Up to what % of a neuron can consist of dendrites?
95%
On a neuron, where is the nucleus, much of the cytoplasm, most of the metabolic activity and protein synthesis contained?
Soma
Where are neurotransmitters produced and stored?
Produced in soma.
Stored in synaptic vesicles.
The bigger the cell body, the ____ the neuron projects.
further
What is the axon hillock?
Specialised part of the cell body, at the interface between soma and axon.
Known as the ‘trigger zone’ due to the density of voltage gated Na+ channels (AP threshold can be reached triggering AP)
What are the benefits of myelinated axons?
Enables saltatory conduction
AP passes from node to node
Very rapid (Up to 120m/s)
What are the three basic types of neurons?
Sensory
Motor
Interneurons
Are sensory and motor neurons afferent or efferent?
Sensory - afferent
Motor - efferent
Where do interneurons carry messages from and to?
Carry messages from one set of neurons to another.
Can bring info from different sources together into one location in CNS.
What non-neuronal cells of the CNS are responsible for supporting neurons and providing a suitable environment in which the neurons can function?
Neuroglia (astrocytes, oligodendrocyte, microglia)
What is the role of oligodendrocytes?
Production and maintenance of myelin sheath
Can oligodendrocytes myelinate more than one axon at a time?
Yes - each cell myelinates multiple axons (up to 50)
What does myelin consist of?
Myelin Basic Protein
Proteolipid Protein
Myelin Associated Glycoprotein
What protein found in the PNS and CNS facilitates interactions between axon and myelin?
Myelin Associated Glycoprotein
Myelination by oligodendrocytes cause an increase and decrease in what?
Increase in nerve conduction velocity
Decrease in size of nerves
Axonal development is dependent on _____ and oligodendrocyte development is dependent on ____.
Oligodendrocytes
Axons
What cell in the CNS is activated by pathogens and is distributed in regular mosaic patterns?
Microglia
What is the main role of microglial cells?
Phagocytic and immune.
Promote repair.
Microglia appear in great numbers shortly before birth as what?
amoeboid (active) microglia
When do amoeboid microglia mature?
At birth when BBB forms, amoeboid matures and assumes it’s ‘resting’ state as microglia.
What are the core functions of embryonic macrophages/microglia?
Apoptotic clearance
Selective killers as well as ‘dustmen’
What are the main roles of astrocytes in the CNS?
Provides structural support
Supply nutrients (glucose)
Maintain ionic environment (remove K+)
Neurotransmitter uptake
Repair of nervous system
Form protective barrier around vessels (BBB)
Astrocytes regulate synaptogenesis. What is this?
The development of synapses between neurons.
Astrocytes form a continuous syncytium. What do they do to other neural cells in relation to the syncytium?
Integrate them in.
Astrocytes form and regulate the BBB. What does this involve?
Formation of the glial-vascular interface
Regulation of cerebral microcirculation
What metabolic functions do astrocytes have?
Provide energy substrates for neurons
Collect neuronal waste
Which extracellular ions do astrocytes regulate?
K+ - following fluctuations associated with neuronal activity.
What signalling functions do astrocytes have?
Modulation of synaptic transmission
Metabolism and synthesis of NT
Release of NT
What are the two broad classifications of astrocytes?
Fibrous astrocytes in WM
Protoplasmic astrocytes in GM
What is the glutamate-glutamine shuttle?
80% of glutamate released at synapse taken up by astrocytes -> astrocytes convert glutamate to glutamine -> release glutamine into synaptic cleft -> taken up by presynaptic terminal -> converted back to glutamate.
What are astrocytes connected via and what can they transport?
Gap junctions
Ca2+
What cells in the CNS line the brain’s ventricles and central canal of spinal cord?
Ependymal cells
How can ependymal cells control fluid homeostasis?
They have direct contact with CSF so can transport electrolytes/solutes between CSF and brain parenchyma
What structure offers immune privileged status to the CNS?
BBB
What does the BBB consist of?
Astrocytes
Pericytes
Blood endothelial cells bound tightly and acting as neurovascular units
What size particles can pass through the BBB?
<500 daltons in young adults
>500 daltons in old adults
BBB dysregulation is evidenced in what conditions?
Alzheimers
Delirium
What is the role of Schwann cells in the PNS?
Myelinate axons (spiral wrapping)
Provide substrate for axon to grow along
One Schwann cell myelinates one axon
What cells are located exclusively in the peripheral ganglia (same site as sensory, parasympathetic and sympathetic ganglia)?
Satellite glial cells
What distinctive morphology do satellite glial cells have?
They wrap around neuronal cell bodies, in most cases forming a complete envelope.
What are the main functions of satellite glial cells?
Unclear but thought to support neurons, supply nutrients + regulate the exchange of materials.
What are the glial cells of the PNS?
Schwann cells
Satellite cells
What are the glial cells in the CNS?
Oligodendrocytes
Microglial cells
Astrocytes
Ependymal cells
___ cells are the most common source of tumours of the nervous system, as they are able to ___.
Glial
Divide
Do glial cells have action potentials?
No
Where are gliomas usually present?
Inside cranium - intra-axial (in brain parenchyma)
What neural tumour is most common in children and infants?
Neuroblastoma
Where are neuroblastomas usually located?
Outside cranium e.g. adrenal glands, abdomen, thorax, neck, spine
What are neuroblastomas derived from?
Neural crest cells from sympathetic nervous system.
Are neurons pre or post mitotic and why is this relevant?
Post-mitotic
Could lead to a cascade of neuronal loss which cannot be replaced.
What is dendritic arborisation?
The formation of new dendritic trees and branches to create new synapses.
What does myelin associated glycoprotein do? Is it in the CNS or PNS?
Facilitates interactions between the axon and myelin.
Present in both CNS and PNS.
Astrocytes regulate neurogenesis and gliogenesis. What are they?
Gliogenesis - formation of glial cells
Neurogenesis - formation of neurons
How can ependymal cells assist in the movement of CSF?
They have cilia, so they use this to move CSF
