Neurones and Neuroglia Flashcards
What are the features of neurones?
Dendrites
Cell body/ perikaryon/ soma
Axon
Synapse
What are dendrites?
Short processes arising from the cell body
May contain dendritic spines
Site of synaptic contacts
What happens at the cell body?
Houses the nucleus
Site of protein, hormone and neurotransmitter production
Gives rise to a single axon
What is an axon?
Long cylindrical and slender process, with an axon hillock and initial segment
Axolemma (plasma membrane)
Axoplasm (cytoplasm)
Can be myelinated or unmyelinated
What are the features of a neuronal synapse?
Presynaptic terminal
Synaptic cleft
Post synaptic terminal
What controls the ion permeability of cells?
Gated ion channels
Alternate between open and closed to allow/ prevent movement
What types of gated ion channels are there?
Mechanically gated
Chemically gated
Voltage gated
What types of electrical signals are there?
Graded potentials (short distance)
Action potentials (rapid over long distances)
What are the features of graded potentials?
They can vary in strength
Lose strength over distance
Slower than APs
Can be excitatory
Can be inhibitory
What ways can you describe a graded potential?
Subthreshold - too weak (No AP)
Suprathreshold - generates AP
What types of neurones are there?
Pseudounipolar
Bipolar
Multipolar
Anaxonic
Describe pseudounipolar neurons
A single process arises from the cell body and divides into two branches, one travels to the PNS and the other to the CNS.
Information at the PNS terminal is transmitted to the CNS (bypasses the cell body)
Signals are relayed from the receptor to the CNS without modification
Describe bipolar neurons
They have two processes which arise from the elongated cell body
One process ends in dendrites
The other forms an axon
They integrate multiple inputs
The modified, processed information passes onto the next neuron in the chain
Describe multipolar neurons
The possess three or more dendrites which branch off directly from the cell body
They also have a single long axon issuing from the axon hillock
Describe what anaxonic neurons are
They are a form of interneuron in the CNS
They only have dendrites
No axon can be determined
Describe the movement of anterograde transport
Towards the synapse / nerve terminal
Describe the movement of retrograde transport
Towards the cell body
What types of neurogoial cells are found within the CNS?
Astrocytes
Oligodendrocytes
Microglia
Polydendrocytes
Ependymal cell
Which neuroglial cells are found in the PNS?
Satellite cells
Schwann cells
Describe the appearance of astrocytes
They’re the largest glial cell
With stellate appearance and centrally located nuclei
What types of astrocytes are found where?
Fibrous - white matter
Protoplasmic- gray matter
Muller cells - the retina
What are the functions of astrocytes and how do they do these?
They shuttle excess ions
Pick up metabolites and glucose from vasculature and carry to neurons
Have a major role in the tripartite synapse
Dues to their processes making contact with thousands of neurons
And forming ‘feet’ on blood vessels
What happens at tripartite synapses?
Glutamate released from presynaptic membranes activates metabotropic receptors
Calcium is released from astrocytes
Releases of gliotransmitters
Which modulates neuronal function
And can regulate local circulation of the brain
Describe oligodendrocytes
Smaller than astrocytes and with fewer processes
myelinating cells within the CNS
Can myelinated multiple axons
Describe microglia
Smallest of all glial cells
Derived from monocyte-macrophage lineage
Immune cells of CNS
Activated by inflammatory markers
Phagocytic function
Describe polydendrocytes
Recently defined
Stem cell pool
Recruited as oligodendrocyte precursors in remyelination
Can provide link between neuronal signalling network and glial cells
Describe ependymal cells and their different types
Epithelial cells (EP) that separate CSF from tissue
Ependymocytes - line ventricle and central canal, posses microvilli and cilia
Tanycytes- found in 3rd ventricle, transport hormone from CSF to capillaries
Choroidal EP - choroid plexus, produce and secrete CSF
Describe satellite cells and where there found
Similar to Schwann cells
Found in sensory, sympathetic and parasympathetic ganglia
Describe Schwann cells and where they’re found
They are myelinating cells of the PNS
One Schwann cell per axon
Found at neuromuscular junction and can take up excessive neurotransmitter
Why is white matter white?
It is the myelinated processes of axons
What is found in the gray matter of the brain?
Nerve cell bodies
Dendrites
Axon terminals
Bundles of unmyelinated axons
Neuroglia
What are the resting membrane potentials of:
Neurons
Smooth muscle
Cardiac muscle
Neuron = -70mV
Smooth muscle = -40mV
Cardiac muscle =-90mV
What maintains the difference between electrical charges on the inside compared to the outside of the cell?
Na+/K+ ATPase pump
3 Na+ pushed out, 2K+ taken in
