4 Nerve Flashcards
Q: What are the 4 primary components of the CNS?
A: cerebral hemisphere
brain stem
cerebellum (hindbrain)
spinal cord
Q: What is the structure of the cerebral hemisphere? Surface? 4 functional regions?
A: There are lots of fold - there is lots of white matter so the brain folds up to make sure that it can fit in the cranium.
highly convoluted surface of gyri (ridges) and sulci (valleys)
- Frontal - front
- Occipital - back
- Temporal - side
- Parietal - middle top
Q: What’s the role of the parietal lobe?
A: Sensory and motor function (proprioception)
Q: What’s the role of the frontal lobe?
A: executive function
Q: What’s the role of the temporal lobe?
A: sound perception and speech recognition
Q: What’s the role of the occipital lobe?
A: visual processing
Q: What is the brain stem primarily made of? Consists of which 3 structures? Relation to cranial nerves?
A: Primarily grey matter (cell bodies)
Descending Order:
- Midbrain
- Pons
- Medulla
target or source of all cranial nerves
Q: What is the cerebellum also called? It’s attached to? Importance in?
A: Hindbrain
structure attached to the brainstem
Important in fine-tuning motor function (balance and posture)
Q: Which one of the 4 main structures of the brain can you live without?
A: You can exist without the cerebellum but life will be more difficult
Q: Where does the spinal cord extend out from? Conduit for? Coordinates?
A: Extends down from the medulla in the brain stem
Conduit for neural transmission
Co-ordinates some reflex actions
Q: Name 4 neurones and an additional 3.
A: unipolar
Pseudo-unipolar
bipolar
multipolar (Pyramidal Cells, Purkinje Cells, Golgi Cells)
Q: What are unipolar neurones made of? Found? (2) Important in?
A: Has a cell body and one axon in one direction.
Rarely found in the CNS
Mainly found around the retina (front)
important in visual processing
Q: What is the structure of pseudo-unipolar neurones? Found? (2)
A: Single axonal projection which splits into two (bifurcates)
Rarely found in the CNS
Mainly found in the pain pathway in the PNS
Q: What is the structure of bipolar neurones? Found?
A: Two projections from the cell body (axon and dendrite)
Rarely found in the CNS
Q: What is the structure of multipolar neurones? Morphologies? (3)
A: Numerous projections coming from the cell body
ONLY ONE AXON - the rest are dendrites
Multipolar neuronal cells can have many morphologies
- Pyramidal Cells - pyramid shaped cell body
- Purkinje Cells - GABA neurones found in the cerebellum
- Golgi Cells - GABA neurones found in the cerebellum
Q: Which neurone type is most abundant?
A: multipolar
Q: How many axons and dendrons can a neurone have?
A: only 1 axon
can have many dendrites
Q: What are the 3 properties of a neurone?
A: Excitable - ability to change membrane potential and send action potentials along axon (only ones in CNS)
Heterogenous Morphology - lots of different types of cells
Non-dividing
Q: Describe 3 common structural features between neurones.
A: Soma (cell body, perikaryon)
- contains nucleus and ribosomes
- Neurofilaments - type of intermediate filament provides structural support and transport
Axon (only one)
- Originates from soma at axon hillock
- Can branch off into collaterals
- usually myelinated
- send signals to other cells
Dendrites
- NOT MYELINATED
- highly branched cell body
- Receive information
Q: What are astrocytes? Appearance? Abundance? Proliferate? Excitation? Functions (4)
A: Neuroglia - ‘neuro glue’
Astrocytes - ‘astro’ like appearance
MOST ABUNDANT CELL TYPE IN THE MAMMALIAN BRAIN
able to proliferate
don’t excite
Functions:
- Structural cells - support by acting as a ‘glue’
- Repair - provide nutrients for repair of neuronal cells when damaged
- Facultative Macrophages - can turn into macrophages when necessary (are immune cells)
- Homeostasis - mop up neurotransmitter and other substances that are released within the CNS - sort of like a sponge
Q: What are the 2 myelin producing cells? Key difference? Draw.
A: schwann cells and Oligodendrocytes
ONE OLIGODENDROCYTE MYELINATES MANY AXONS
ONE SCHWANN CELL MYELINATES ONE AXON SEGMENT
Q: What are glial cells (neuroglia)? Examples? (6)
A: cells in the CNS that are not neurones
role of supporting neuronal cells
oligodendrocytes, astrocytes, ependymal cells, Schwann cells, microglia, and satellite cells.
Q: What’s the role of a schwann cell?
A: Produces myelin for peripheral nerves
ONE SCHWANN CELL MYELINATES ONE AXON SEGMENT
Q: What are the 3 differences between oligodendrocytes and astrocytes?
A: Oligodendrocytes are smaller
Oligodendrocytes have a denser cytoplasm and nucleus
Absence of intermediate filaments and glycogen in the cytoplasm
Q: Describe oligodendrocyte morphology. Projections?
A: variable morphology and function
numerous projections that form internodes of myelin
ONE OLIGODENDROCYTE MYELINATES MANY AXONS
Q: What are microglia? Similar to?
A: Immune cells of the CNS
Similar to macrophages
Q: What are ependymal cells? Full of? Role?
A: Epithelial Cells of the CNS
Line fluid filled ventricles - full of cerebrospinal fluid
Regulate production and movement of cerebrospinal fluid
Q: Summarise the neurones and neuroglia. (5)
A: Neurone: Excitable cells of the CNS (Responsible for electrical transmission)
Oligodendrocyte: Glial cell - produces myelin
Astrocyte: Most abundant cell type in the CNS (provide support to neurones)
Microglia: Neuronal macrophages (functional during immune response and inflammation)
Ependymal Cells: Epithelial cells lining ventricles
Q: What are the 4 major ions involved in neurotransmission and resting membrane potential? Cell permeability? Causes?
A: Na+
K+
Ca2+
Cl-
Cell membranes are impermeable to these ions - transport is regulated by pumps and channels
This causes uneven distribution of ions
Q: Describe the uneven distribution of the 4 major ions? What does this cause?
A: High Extracellular - Na+ and Cl-
Low Extracellular - K+
High concentration gradient into the cell of Ca2+ because of very low concentrations inside the cell
The differences in concentration creates a potential difference across the membrane
Q: What are the normal values for K+ concentration (mM) inside and outside a cell?
A: Conc outside/mM
4
Conc inside/mM
150
Q: What are the normal values for Na+ concentration (mM) inside and outside a cell?
A: Conc outside/mM
140
Conc inside/mM
10
Q: What are the normal values for Ca2+ concentration (mM) inside and outside a cell?
A: Conc outside/mM
2
Conc inside/mM
0.0001
Q: What are the normal values for Cl- concentration (mM) inside and outside a cell?
A: Conc outside/mM
120
Conc inside/mM
5
Q: What is the resting membrane potential of neuronal cells?
A: Negative Charge Inside (intracellular)
Resting Membrane Potential = -40 to -90mV
Q: What happens when an AP leaves a cell/area? What happens as a result? (3)
A: NA+ and K+ imbalance -> need to be restored
-Na+K+ATPase (pump) restores the ion gradients
- resting configuration: Na+ enters vestibule and upon phosphorylation -> ions are transported through protein
- active configuration: Na+ removed from cell-> K+ enters the vestibule
- pump returns to resting configuration -> K+ is transported back into the cell
Q: What a Na K pump exchange? Uses?
A: 3 Na+ leave cell
2K+ enter cell
uses 1 ATP
Q: What is happening with the VGSC and VGKC at rest? How is an action potential created?
A: at resting membrane potential
-voltage gated Na+ channels (VGSCs) and voltage gates K+ channels (VGKCs) are closed (-70mV)
- membrane depolarisation: opening of VGSC (around -40mV) -> Na+ influx -> further depolarisation
- VGKCs opens at slower rate and causes -> efflux of K+ from cell-> membrane repolarisation
Q: Without myelination, what is electrical conduction like? What does myelin do?
A: get slow movement of action potentials along the axon via cable transmission
Myelin prevents the action potential from spreading because it has high resistance and low capacitance
Q: What is saltatory conduction?
A:
Nodes of Ranvier have a dense concentration of VGSCs and VGKCs
Action Potentials jump between Nodes of Ranvier allowing faster conduction
Q: What happens in a synapse? (3)
A: neurotransmitter is released from vesicles
- AP opens voltage gated Ca2+ channels at presynaptic terminal
- Ca2+ influx -> vesicle exocytosis
activation of post synaptic receptors
- NT bind to receptor on post synaptic membrane
- receptors modulate post-synaptic activity
neurotransmitter reuptake
- NT dissociates from receptor and can be:
i) metabolised by E in synaptic cleft
ii) recycled by transporter protein
