Neural tissues Flashcards
Role of afferent neuron
- Transmit sensory info to brain/spinal cord
Role of efferent neuron
- Motor neurons transmitting info from the brain to effector organ ie muscle
What is a ganglion
- Group of cell bodies outside CNS
Where are motor ganglia located
- Many motor ganglia are located in the sympathetic trunks, two long chains of ganglia stretching along each side of the vertebral column from the base of the skull to the coccyx, these are referred to as paravertebral ganglia
Where are prevertebral motor ganglia located
- Located near internal organs innervated by their projecting fibres, while terminal ganglia are found on the surfaces or within the walls of the target organs themselves
What are eccentric nuclei
- Eccentric nuclei aren’t in the centre
- Usually in smaller neurons
What type of ganglion is the dorsal root ganglion
- A sensory ganglion
What are the broadmann areas of the neocortex numbered between
- 1-52
- boundaries determined by cellular cortex
What does broadmann area 4 correspond to
- Primary motor cortex
What does broadmann area 17 correspond to
- Primary visual cortex
What are the protruding processes of a neuron also known as
- Neurites
What does arborization refer to
- Refers to the fact that the dendrite splits into branches that make it look like a tree
What are the two main factors that increase conduction velocity
- Myelin increases it
- Increase in diameter increases it
Describe the classification of neurons
- Multipolar
- Bipolar
- Unipolar
- All neurons have just 1 axon
- Majority of neurons have several dendrites ‘multipolar’
Where are pyramidal cells located
- Pyramidal cells are located in the neocortex
- Neocortex is the part of the mammalian brain involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language
What are the type of cells in the cerebellum
- Purkinje cells which are GABAergic
- Single layer of them in the cerebellum
What type of neurons are present in the dorsal root ganglion
- Pseudounipolar
- One axon
- One dendrite
Give an example of where bipolar neurons are present
- Retina
- One dendrite
- One axon
- least numerous
- Sensory neurons
Where are true unipolar neurons present
- Sensory cells such as rods and cochlear hair cells
How big is the gap of a chemical synapse on average
- 30nm
- Common throughout nervous system
- Signalling is not in retrograde direction(with some exceptions)
Give an example of divergent signalling
- Skin receptors
- A single neruon sends its output signal to many neurons
Give an example of convergent signalling
- Retina
- Multiple inputs influence a single neuron
What percentage of the brain is roughly composed of interneurons
- Brain is 80% interneurons
- Cortex is only 20-30% interneurons
How do interneurons receive signals from an alpha neuron
- Receive an excitatory collateral from the alpha neuron’s axon as they emerge from the motor root, and are thus ‘kept informed’ of how vigorously that neuron is firing
How do renshaw cells work
- Renshaw cells are inhibitory interneurons found in the gray matter of the spinal cord, and are associated in two ways with an alpha motor neuron
- They send an inhibitory axon to synapse with the cell body of the initial alpha neuron of the same pool
How do glial cells differ from neurons
Glia differ from neurons in that they:
- Have no action potentials
- Do not form synapses
- Are able to divide
- Form the myelin sheaths
Why are glial cells a common source of tumours
- Due to their ability to divide as adult cells
- Glial cells do not conduct electrical impulses
Role of oligodendrocytes
- Production/maintenance of myelin sheath in CNS
- One ligodendryocyte myelinates multiple axons(from different neurons)
Role of astrocytes(CNS)
- Supports neurons(star shaped)
- Assists neuronal development/growth(neurotrophic), protects neurons from harmful substances
- Its ‘feet’ on processes about blood vessel endothelium - influence blood and flow and blood-brain barrier
Role of microglia(CNS)
- Immune cells
- Protect neurons from disease, migrate to injury sites, engulf microbes/debris
- Of mesodermal origin(like other immune cells), also develop from monocytes
- Actually move around in real time
Role of ependymal cells(CNS)
- Line brain’s ventricles and central canal of spinal cord, forms CSF
Role of schwann cells(PNS)
- Production/maintenance of myelin sheath, PNS regeneration
- 1 axon wrapped per schwann cell
- Multiple lipid bilayers which allow for resistance, vital for regeneration in the event of trauma
Role of satellite cells(PNS)
- Support neurons, regulate exchange of materials between neurons and interstitial fluid
- Perform analogous role in PNS to what astrocytes do in CNS
What are gliomas
- Largest group of primary tumours derived from glial cells
- Usually highly malignant
- Grow rapidly
- Difficult to remove completely with surgery
- Usually inside cranium
What is a neuroblastoma
- Tumour(cancer)
- Most common in children and infants
- Outside cranium
- Derived from neural crest cells from sympathetic NS
What are the two most common metabolites made by the breakdown of epinephrine and norepinephrine
- Homovanillic acid(HVA)
- Vanillylmandelic acid(VMA)
- Neuroblastoma cells can also make these catecholamines, these two catecholamine metabolites can be measured in blood and urine
Prognosis for neuroblastomas
- Initial prognosis is typically good, survivors often develop neurological problems - 30 years later
- Treatment depends on type
