Neuronal Tissues Flashcards
What is the Broadmann Area of the Primary Visual Cortex?
Broadmann Area 17
What is the Broadmann Area of the Primary Motor Cortex?
Broadmann Area 4
What Are the Broadmann Areas of the cerebral cortex?
Regions of the cerebral cortex with their own distinct function
52 in total
Each area has its own particular inputs and outputs
What are the components of a typical neurone?
Cell body (containing the nucleus)
Dendrites
Axon hillock
Axon
Axon collaterals
Axon terminals
Myelin sheath
What are the functions of neurones?
Receive and integrate incoming information from sensory receptors or other neurones
Chemically transmit information to other neurones or effector organs
What are dendrites?
Branched protoplasmic extensions
They propagate the electrochemical input from other cells to the cell body of a neurone
They branch off from the cell body to receive incoming action potentials from other neurones
How much of a neurone can a dendrite occupy?
Up to 95%
What is the role of the cell body in a neurone?
Houses the organelles (nucleus, cytoplasm, mitochondria, ribosomes, etc.)
Produces neurotransmitters which are subsequently stored in synaptic vesicles
What is the role of the axon hillock?
It is a part of the cell body with a high density of voltage gated Na channels
Is the sight at which action potentials are triggered due to the high density of voltage gated Na channels
Myelinated axons
Have a diameter greater than 1 micrometer
Myelination allows saltatory conduction
Action potential passes between nodes of ranvier
This is very rapid (up to 120m/s)
What is the role of a sensory neurone?
Sends information from the sensory organs (receptors) into the CNS
Therefore also called Afferent neurones
What is the role of a motor neurone?
Carry messages from the CNS to operate muscles and glands
Also referred to as efferent neurones
What is the role of an interneurone?
These carry messages from one set of neurones to another
Bring information from different sources into one location In the CNS
What are neuronal pathways?
These are used to link separate neurones
What is the role of oligodendrocytes?
Oligodendrocytes are responsible for producing and maintaining the myelin sheath in the CNS to create white matter
Each oligodendrocyte can myelinate multiple axons
What are the components of myelin?
Myelin basic protein and proteolipid protein make up approximately 80% of myelin
Other proteins include myelin associated glycoprotein (which facilitates the interactions between the axon and myelin
What are the benefits of myelinated axons?
Increases the nerve conduction and velocity
Decreases the size of nerves as a result
What is the role of microglia in the CNS?
Act as the macrophages of the CNS essentially
Begin inactivated but become activated by pathogens
Comprise 5% of the cells in the brain
They are phagocytic and immune cells but also promote repair
Apoptotic clearance
What are the roles of Astrocytes in the CNS?
Provide structural support to the CNS
Supply glucose
Maintain the ionic environment via removal of K
Uptake leftover neurotransmitters in the synaptic clefts
Repair the CNS
Form the blood brain barrier
What are the developmental functions of Astrocytes?
Regulate neuro and gliogenesis (they’re stem elements of the CNS)
Neuronal pathfinding
Regulate synaptogenesis
What are the structural functions of astrocytes?
Form the scaffold of the CNS, therefore defining the functional architecture of the brain and spinal cord
Astrocytes form a continuous syncytium and integrate other neural cells into this syncytium
What are the blood brain barrier related functions of Astrocytes?
Form the glial-vascular interface
Regulate the cerebral microcirculation
What are the metabolic functions of astrocytes?
Provide energy substrates for neurones
Collect neuronal waste
What are the homeostatic functions of astrocytes?
Control the microenvironment of the CNS
Regulate the concentrations of K following the fluctuations which occur after neuronal activity
Regulate extracellular pH
Remove neurotransmitters from the extracellular space
What are the signalling functions of astrocytes?
Modulate synaptic transmission
Metabolise and synthesise neurotransmitters
Release neurotransmitters
What are the 2 subtypes of astrocytes and how do they differ?
Fibrous astrocytes are located in white matter areas
Protoplasmic astrocytes are located in grey matter
What is the role of astrocytes in the glutamate-glutamine shuttle?
They take up approximately 80% of glutamate released at the synapse
They then convert this to glutamine and release it so the presynaptic terminal can uptake it
It is then converted back to glutamate
What are the roles of ependymal cells in the CNS?
They line the ventricles of the brain and the central canal of the spinal cord
Aid in homeostasis of the CSF due to the close contact with it as well as the Brain parenchyma
Also contribute towards the formation of CSF and assist in its circulation via cilia movement
What is the blood brain barrier?
Highly selective permeability barrier which has evolved to determine substances can enter the brain and provides immune privilege to the CNS
What cells are present in the blood brain barrier?
Astrocytes
Peri yes
Blood endothelial cells
These are arranged in neurovascular bundles
How does the permeability of the blood brain barrier change with age?
Decreases
Dysregulation of the blood brain barrier is evidenced in Alzheimer’s disease and delirium, as well as other neurodegenerative disorders
What are the roles of Schwann cells and how do they differ from oligodendrocytes?
They are the Neuroglia of the PNS
Aren’t present in the CNS
Important for regeneration and they provide substrate for the axon to grow along
Myelinates a single axon
What are Satellite cells?
Located exclusively in the peripheral ganglia (sensory, parasympathetic and sympathetic)
Wrap around neuronal cell bodies forming a complete envelope
Function isn’t 100% clear but considered to support neurones, supply nutrients, regulate exchange of materials between the interstitial fluid and neurones
Similar to what astrocytes do in CNS
How are Neuroglia different to neurones?
Do not generate any action potentials
Are able to divide
Form the myelin sheathes
What are gliomas?
Tumours derived from glial cells
Highly malignant and grow rapidly
Difficult to access surgically so radiotherapy is the go to treatment option
Usually inside the cranium so also referred to as intra-axial tumours
What is a neuroblastoma?
Rare tumour
Outside of the cranium, typically the adrenal glands, abdomen, thoracic cavity, neck and spine
Derived from the neural crest cells from the nervous system
Survival rates vary depending on the subtype
Initial prognosis is typically good
However survivors often develop neurological problems approximately 30 years later
Treatment depends on the subtype
