How nerves work Flashcards
What is the somatic nervous system?
Part of PNS
Voluntary control of body movement
What is the autonomic nervous system?
Part of nervous system controlling functions not directed consciously
Breathing, heartbeat etc
What is the enteric nervous system?
Part of ANS
Governs function of Gastrointestinal tract
What is the function of the Meninges?
Protect the central nervous system
True or false
Sulcus are the tops of the folds, and the gyrus are the part within the fold
False
Gyrus = Tops
Sulcus = Bottom
The Cerebrum is composed of what lobes? (4)
Frontal
Temporal
Parietal
Occipital
What part of the brain contains the thalamus and hypothalamus?
Diencephalon
What is the function of the thalamus?
Relay motor and sensory nerve signals
What does the Hypothalamus do?
Hormone control/release
Body temperature
The midbrain, pons and medulla oblongata are in what part of the brain?
Brainstem
How many sets of cranial nerves are there?
12
How many pairs of spinal nerves are there?
31
“Catch the large snake carefully”
What does this refer to?
Cervical - 8 Thoracic - 12 Lumbar - 5 Sacral - 5 Coccygeal - 1
Spinal nerve pairs
What type of matter makes up the Ventral and dorsal horn?
Grey matter
What horn is associated with Afferent signals?
Dorsal horn
Where are the cell bodies of sensory fibres contained?
Ganglions
Where are nerve tracts found?
Up spinal chord
In the white matter
Describe the simple purpose of the axon hillock.
Decides and triggers action potentials
What is the simple purpose of the presynaptic terminal?
Transmitter release
What is the name of the support cells of the CNS?
Glia
What 3 types of Glia is there?
Astrocytes
Oligodendrocytes
Microglia
What is the function of astrocytes?
Maintains external environment for neurones:
- surrounds blood vessels and transports nutrients from the blood to neurones
- produces blood-brain barrier
Describe the purpose of Oligodendrocytes.
Form myelin sheaths in CNS
What do Microglia do?
Phagocytic hoovers
Why do neurones need a resting membrane potential?
Allows depolarisation etc
So signals can be transmitted
In terms of K+ and Na+, why is there a RMP?
K+ moved into cell, Na+ moved out by pump
K+ leaks out
More +ve outside
What equation predcits the RMP for a single ion species?
Nernst equation
Why is the RMP not -90mV but is -70mV?
3
Other leaky channels
Electrogenic Na/K pump
Large -ve intracellular molecules
What is the purpose of a Graded potential?
Move the RMP to/away from threshold to trigger/inhibit an action potential
What are the 4 types of Graded potential?
Generator
Post-synaptic
Endplate
Pacemaker
Why are graded potentials decremental?
Axons are poor conductors
Current leaks out
Why are graded potentials graded?
Strength of stimulus is encoded in change of membrane potential
What are the 2 IPSP’s?
Ionotropic chloride - fast
Metabotropic potassium (opener) - slow
What are the 2 EPSP’s?
Ionotropic sodium/potassium - fast
Metabotropic potassium (closer) - slow
What is the significance of GABA and Glycine in graded potentials?
Neurotransmitters
Simply describe how post-synaptic potentials are made.
Neurotransmitters open/close ligand-gated ion channels
Causing MP to be de/hyperpolarised
Voltage-gated ion channels are used to produce what?
Action potential
What does summation of graded potentials mean?
They can add to each other
What is the difference between spatial and temporal summation?
Temporal = same synapse input repeated quickly
Spatial = different synapse inputs integrating
What is pre-synaptic inhibition?
Synapse with inhibitory input attached to excitatory synapse
Reduces transmitter release - inhibits that one input
What is post-synaptic inhibition?
Inhibitory input synapsed actually onto the neurone
Inhibits all inputs
What must happen for an action potential to fire?
MP must reach threshold
-55mV
What happens when membrane potential reaches threshold?
VG Sodium channels open
Sudden massive depolarisation
What causes a cell to re/hyperpolarise when an action potential fires?
Sodium channels close
More potassium channels open - K+ goes out
What does the frequency of an action potential encode?
Stimulus intensity
Describe self propagation of action potentials.
Threshold reached, VGSC open, depolarisation
Depolarises next VGSC along which opens - depolarises more
Repeated
What is the significance of the refractory period, in self propagation of action potentials?
Prevents AP from going backwards
What 2 ways can conduction velocity be improved in axons?
Enlarged axons
Myelination
Why is conduction velocity higher in large axons?
Lower axial resistance
Depolarisation spreads further
Less VGSC needed
Why does myelination increase conduction velocity?
Less leakage of current
Depolarisation spreads further
Less VGSC needed
What cells produce myelin for the PNS?
Schwann cells
What cells produce myelin for the CNS?
Oligodendrocytes
What are the purpose of Nodes of Ranvier?
Gaps for VGSCs
What is saltatory conduction?
Propagation of AP along myelinated axon
Depolarisation at each NOR
What is the effect of Multiple sclerosis and Guillain-Barre syndrome?
De-myelination
What causes the compound action potential to have different spikes on an electrode graph?
Different sizes and myelinations of different axons in nerve trunk
What are the 6 different axon types?
A(alpha) A(beta) A(gamma) A(delta) B C
What axon basic type is responsible for proprioception, motoneurones, touch, pain etc?
A
Whip or nae nae
In terms of sensitivity to local anaesthetics;
A is most sensitive, C is least sensitive.
Nae nae
A is most sensitive to anoxia
C is most sensitive to LA
Yeet or skeet
Action potentials have a refractory period whereas graded potentials have no refractory period.
Yeet
What are the 2 types of synapses?
Chemical
Electrical
What does the action potential do at the end of motor neurone?
Opens voltage gated Calcium channels in presynaptic terminal
What effect does opening Ca2+ channels have in presynaptic terminal?
Change in [Ca2+] causes fusion of vesicles with membrane
What happens after the vesicles in presynaptic terminal?
Acetylcholine released via exocytosis into synaptic cleft
What does ACh bind to after diffusing across the synaptic cleft?
Binds to Ach (nicotinic) receptors
What effect does ACh have when it binds to the ACh receptors? (3)
Opens ligand gates Na+/K+ channels
Evokes end-plate potential
Depolarises to threshold
Describe what happens after the end plate potential is triggered.
Opens VGSC
Evokes new AP
What enzyme breaks down ACh?
Acetylcholinesterase
In the CNS, synapses can be found on 3 different parts of the cell. What names are used for these synapses?
Axo-somatic
Axo-dendritic
Axo-axonal
True or false
Polysynaptic pathways are harder to predict because they are much more open to modulation at each synapse
True
On a scale of 1 to 10
How fucking boring is nerves
11
True or false
Feedback inhibition (synaptic) is found only at neuromuscular junction to stop muscles repeatedly twitching.
False
Only in CNS
Means neurone fires once then stops
