Neuro - Cells of Nervous System Flashcards
What does the CNS consist of?
2 cerebral hemispheres
brainstem
spinal cord
What does the PNS consist of?
Fibres originating from the CNS
What are the hemispheres?
Also called telencephalon - form the main cerebral cortex
How many lobes are in each hemisphere?
4
What are the main lobes of the hemispheres?
frontal
temporal
parietal
occipital
What is the role of the frontal lobe?
Executive functions: memory cognition recognition primary motor cortex
What is the role of the parietal lobe?
Contain primary somatosensory complex
What is the role of the temporal lobe?
Processing of sound with the primary auditory complex
What is the role of the occipital lobe?
Contains primary visual complex for sight perception
What does the brainstem consist of?
Mid brain
Pons
Medulla
What is the function of the brainstem?
Important functions such as control of respiration and heart rate, and is the target or source for the majority of cranial nerves
What is the role of the cerebellum?
Conscious motor coordination, balance and posture
What is the role of the spinal cord?
Acts as a channel for neural transmission and has some role in reflex responses.
What are gryi?
The outfoldings on the outermost layer of the cortex
What are sulci?
The valleys formed between gyri
What separates the frontal from the parietal lobe?
Central sulcus
Why can’t neurones be classified on the bases of their shape and size?
Due to their polymorphous structure
Define mature neurones
Non-dividing excitable cells whose main function is to receive and transmit information in the form of electrical signals
What are the 4 main classes of morphology of neurones?
Unipolar
Bipolar
Pseudo-unipolar
Multipolar
What is a unipolar neurone?
Starts of with nucleus and ends with a single axonal projection
What is a bipolar neurone?
Two projections on either side of the nucleus: axon and dendrite
What is a pseudo-unipolar neurone?
Starts of with one original projection from the nucleus but then bi-furcates into 2 projections
What is a multipolar neurone?
Multiple projections from the cell body.
What are the 3 main classes of multipolar neurone?
Pyramidal cells
Purkinje cells
Golgi cells
What are pyramidal cells?
Pyramid shaped cell body
What are purkinje cells?
GABA neurones found in the cerebellum (inhibitory)
What are Golgi cells?
GABA neurones found in the cerebellum (inhibitory)
What is the soma?
Cell body or perikaryon.
Contains nucleus and ribosomes as well as neurofilmaents which are important for structure and transport
What is the axon?
Long process (nerve fibre), originates from soma at axon hillock, and can branch off in collaterals
What usually covers the axon?
Myelin which allows for faster conduction
What are dendrites?
Projections from the cell body (every projection except for axons). They are responsible for receiving signals whereas axons are important for sending signals
What are astrocytes?
Most abundant cell type in the brain. Structural cells important for neuronal maturation, synapse formation and cell repair.
What are oligodendrocytes?
Myelin producing cells in the CNS
What are Schwann cells?
Myelin producing cells in the PNS
Aside from location, what is the main difference between oligodendrocytes and Schwann cells?
Oligodendrocytes can send numerous projections to cover multiple axonal segments. Schwann cells can only cover one segment each
What are microglia?
Immune cells of the CNS and act similarly to macrophages
What are ependymal cells?
Epithelial cells lining the inside of fluid filled vesicles - regulate the production and movement of CSF
Define the resting membrane potential
Ionic imbalance between the intracellular and extracellular of a neurone due to unequal ion distribution
What does an ionic imbalance of the cell membrane give?
electromotive force (EMF)/potential difference.
What do we call the outside of the cell?
Zero reference point
What is the typical range form resting membrane potential?
-50 to -90mV so we average to -70mV
Where is a greater potential (difference) found in neurones?
Areas adjacent to the membrane
What are the 4 main physiological impermeant ions?
Sodium
Potassium
Chloride
Calcium
What ions are found highly concentrated inside the cell?
Potassium
What ions are found highly concentrated outside the cell?
Sodium
Chloride
(Calcium found at low concentration but inside the cell is even lower)
At RMP, what channels are closed?
VGSCs, VGKCs
What causes the beginning of depolarisation?
Action potential begins to open VGSCs so sodium begins to enter the cell. Membrane potential goes to -40mV
What is the result of the beginning of depolarisation?
Threshold reached, massive sodium influx into cell to +10mV.
Why do sodium channels open first?
Naturally faster kinetics
What happens after the opening of VGSCs?
VGKCs open at a slower rate, causing a potassium efflux from the cell.
What is result of potassium efflux?
Repolarisation to a very low potential
We do we reconfigure the imbalance between sodium and potassium?
Na+/K+ ATPase
What is the resting configuration of Na/K ATPase?
Allows sodium ions inside the cell to enter the vestibule
What is the active configuration of Na/K ATPase?
Conformational change from phosphorylation of ATP leads to opening on the extracellular side so sodium leaves and potassium can enter there vestibule - transported back into cell as pump returns to resting configuration.
What about myelin prevents AP spreading across?
High resistance and low capacitance
How do Nodes of Ranvier induce saltatory conduction?
Intermittent gaps allow for AP to jump between nodes to the terminal.
What are synapses?
Small gaps between neurones
What is the need for synapses?
Electrical signal cannot jump between synaptic cleft therefore electrical energy use be converted to chemical energy via synapses.
What is stage 1 of synaptic transmission?
Action potential propagates along axon with VGSCs and VGKCs - causes calcium influx due to depolarisation.
What is stage 2 of synaptic transmission?
Neurotransmitter release due to calcium influx - exocytosis of NTs
What is stage 3 of synaptic transmission?
NTs diffuse across cleft and bind to post-synaptic terminal.
What is stage 4 of synaptic transmission?
Binding at the post synaptic terminal induces perpetuation of propagation and then the NTs are degraded or taken back into terminal via transporter proteins.
