Nerve Flashcards
Functional regions of the brain?
Temporal: around and speech recognition
Parietal: sensory and motor function (proprioception)
Gyri: ridges
Sulci: valley
- Hemispheres are most visible components of brain
Structures of regions of brain?
Brainstem: descending order midbrain–>pons–>medulla (in descending order)
- Many cranial nerves arise here - Primarily grey matter
Cerebellum: hindbrain attached to brainstem
Spinal cord: extends from medulla
- Neurotransmission conduit - Coordinates some reflex actions
What are the 4 types of neurones?
- Only ever have one axon
Unipolar: cell body and 1 axonal projection
- Rare in CNS - Mainly found in retina
Pseudounipolar: single axonal projection that splits in 2
- Rare in CNS - Mainly pain pathways in PNS (ganglia)
Bipolar: 2 projections from cell body
- Rare in CNS
Multipolar: numerous projections from cell body
- 1 axon, the rest are dendrites
- Cell body small relatively small in comparison to
rest of cell
- Can have many morphologies:
Give examples of multipolar cell types:
- Pyramidal cell: pyramid shaped body
- Purkinye cells: GABA neurones in cerebellum
- Golgi cells: GABA neurones in cerebellum
What are the common features of neurones?
- Soma (cell body)
- Nucleus and ribosomes
- Protein production
- Neurofilaments: intermediate filament providing
structural integrity and within cell body
the cell body with nucleus and intracellular organelles
- Axon
- Long process originating from soma at axon hillock
- Can branch into collaterals
- Myelinated
thin outgrowth responsible for the conduction of an action potential
- Dendrites
- Non myelinated
- Highly branched cell body
- Receive info
highly branched outgrowths of the soma.
What is the most abundant cell type in brain
Astrocyte
What is the characteristics of neuroglia of an astrocyte?
- Non excitable
- Can proliferate
What are the functions of astrocytes?
- Structural cells acting as glue - maintain structural integrity
- Repair - providing nutrients
- Facultative macrophages: can turn into macrophages when necessary
- Homeostasis - mop up neurotransmitter and other substances (water) released in CNS
- Important in maintaining blood brain barrier
cell repair, synapse formation, neuronal maturation and plasticity.
What is the function of oligodendrocytes?
myelin produced by glial cells and extends in spiral membrane around axons of many neurones
What is the structure of oligodendrocytes?
- Variable morphology and function
- Numerous projection
- Smaller and denser than astrocytes
- No intermediate filaments or glycogen in cytoplasm
- 1 oligodendrocyte myelinates many axons
What are Schwann cells?
- produce myelin for peripheral nerves
- Each cell myelinates 1 axon segment
What are Microglia?
- CNS immune cells, similar to macrophages
- Not the same as neuroglia (which are all CNS cell types except neuronal cells)
What are ependymal cells?
- CNS epithelial cells
- Line fluid filled ventricles (filled with cerebrospinal fluid)
- Regulate production and movement of cerebrospinal fluid
How is resting membrane potential maintained?
- Na+, K+, Ca2+, Cl-
- Cells impermeable to ions so regulated by pumps and channels
- High ECF: Na and Cl (goes into cell)
- Low ECF: K (goes out of cell)
- Ca low in cell - high concentration gradient for it (goes into cell)
- This creates potential across membrane with negative charge inside
- RMP ranges -40 - -90 mV
- -40 more depolarised
- -90 more hyperpolarised
- Positive and negative charges concentrated around membrane
- At RMP VGSC and VGKC are closed
How is an Action potential produced?
- When pd -40mV VGSC opens quite quickly and Na enters
- Depolarisation because increased voltage
- VGKC opens at slower rate and K efflux so repolarisation/hyperpolarisation
- Na-K pump restores membrane p.d (repolarisation)
How does Sodium-Potassium ATPase work?
1- Resting configuration: Na enters vestibule and upon phosphorylation transported through proteins
2- Active configuration: Na removed from cell –> K enter vestibule
3- Pump returns to resting configuration–> K+ transported back into cell
- 3 Na in for every 2 K out
What is the difference between repolarisation and hyperpolarisation?
Repolarisation: getting more negative but returning from depolarized state
Hyperpolarisation: as getting more and more negative
What is the purpose of saltatory conduction?
- If no myelin conduction is slow via cable transmission
- Myelin prevents AP spreading because high resistance and low capacitance
- Nodes of Ranvier: small gaps of myelin intermittently along axon - have high VGSC and VGKC concentration so AP jumps between nodes so faster conduction
How is a synapse propagated?
- AP propagated by VGSC opening so AP moves long neurone
- AP arrives at presynaptic membrane (end of axon), depolarisation causes VGCC (concentrated here) to open and Ca influx
- Ca fuses with neurotransmitter containing vesicles causing vesicular exocytosis
- NT binds to post synaptic membrane receptor and converts chemical signal into electrical signal
- Receptors modulate post synaptic activity
- NT unbinds from receptor - reuptake either metabolised by enzymes in cleft and taken back up by axon terminal or recycled by transport proteins
Define neurone
A mature neuron is a non-dividing excitable cell whose main function is to receive and transmit information in the form of electrical signals.
What is the pd of an action potential
+10 mV
