Lecture 4- Nerves Flashcards
What are the valleys and ridges called
Gyri- ridges
Sulci- valleys
What are the four regions of the cerebral hemisphere
frontal
parietal
temporal
occipital
What are the three sections of the brainstem?
Midbrain
Pons
Medulla
What originates from the brain stem?
Cranial nerves
What is the role of the cerebellum?
Motor coordination
Balance
Posture
What is the role of the spinal cord?
Coordinates reflex actions
For nerve transmission
What are the 4 types of neurones and what do they look like?
1) Unipolar: 1 axonal projection
2) Pseudo-unipolar: single axonal projection that divides into two
3) Bipolar: 2 projections
4) Multipolar: Numerous projections
Name three types of Multipolar cells
Pyramidal cells
Purkinje cells
Golgi cells
Describe the structure of a neurone
1) Soma (cell body): contain nucleus & ribosomes
2) Axon: nerve fibre, from axon hillock on soma, branches into collaterals, covered in myelin
3) Dendrites: highly branched, not myelinated, receive signals
What are neurones?
Excitable cells of CNS
Non-dividing
What are the functions of astrocytes?
- structural cells
- cell repair
- immune cells (facultative macrophages)
- neurotransmitter release and reuptake)
CAN PROLIFERATE
Which two cells produce myelin? What is the difference between them two?
Oligoendrocytes and Schwann cells
1 Oligo–> myelinates many axons
but…
1 Schwann –> myelinates one axon segment and PNS nerves
What are microglial cells?
- Similar to macrophages
- perform immune functions in CNS
What are Ependymal cells
- Epithelial cells which line fluid filled ventricles
- regulate production and movement of CSF
What are the relative concentrations of ions at rest?
High EC- Na+ and Cl-
Low EC- K+
High conc gradient- K+
What is the RMP of neuronal cells?
-40mV to -90mV
Which two channels are found in neuronal membranes and what are their states at RP?
Voltage gated Na+ channels (VGSCs)
Voltage gated Ca2+ channels (VGCCs)
Both are closed at RP
What happens when membranes depolarise?
VGSCs open–> Na+ influx –> further depolarisation
What happens when membranes repolarise?
VGKCs open–> efflux of K+ from cell –> membrane repolarisation
What is the purpose of the Na+/ K+ ATPase pump after repolarisation?
- After AP, there is an imbalance in Na+ and K+
- the pump restores the ion gradients
Explain how the ATPase pump transports K+ and Na+
- Resting configuration- Na+ enters and when channel is phosphorylated ions are transported
- Active configuration- Na+ removed from cell–> K+ enters vestibule
- Returns to Resting configuration- transported back into cell
What are the characteristics of myelin which allow saltatory conduction?
- high resistance
- low capacitance (ability to store electrical charge)
What is saltatory conduction?
AP jumping between nodes of Ranvier
Describe the sequence of events that allow transmission of an AP at a synapse
1) AP arrives at synapse
2) Causes VGCC to open
3) Ca2+ influx
4) Causes vesicles containing neurotransmitters to fuse with the presynaptic membrane
5) Neurotransmitter diffuses across synaptic cleft
6) NT binds with receptors on postsynaptic membrane, AP propagated here
7) Neurotransmitter broken down by synaptic enzymes
8) Reuptake of neurotransmitter by presynaptic knob
