Nerves Flashcards
How many pairs of spinal nerves are in human body
31 pairs of spinal nerves:
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
Label the structure of the spinal cord
What is the action of different nerves in CNS and PNS
Afferent(sensory)->interneurons->Efferent(motor)
What are the different types of glia in CNS
Astrocytes- Maintain external env.
Surround blood vessels
Oligodendrocytes- Form myelin sheaths
Microglia- Macrophages of CNS
Ependymal- produce CSF
What do the different parts of the Neurons do
Dendrite-recieves info
Initial segment(axon hillock)- triggers AP
Cell body- Contains nucleus
Axon- Sends AP
Axon(end of neuron)- releases neurotransmitter
What are the different Afferent, inter, and efferent neuron
Afferent- Bipolar, Pseudounipolar
Inter- Multipolar, Anaxonic
Efferent- multipolar
What are the different types of glia in PNS
Schwann- Form myelin sheath
Satellite- Support neuron cell bodies
What is the resting membrane potential of neurones
-70mV
What are the different types of membrane potentials
Action Potential- Transmit signals over large distances
Graded Potentials- Decide when AP fired
Resting membrane potential- keeps cells ready to respond
What helps to create a resting membrane potential
Leaky K+ channels
How does leaky K+ channels affect electrical gradient
K+ leak out of cell down c.g
Builds up electrical gradient
Electrical gradient equal and opposite to c.g
What are some properties of graded potentials
- Are graded- small/big stimulus=small/big response
- Decremental- become smaller as they travel across membrane
- Hyperpolarising/Depolarising properties
- Summate- two potentials can be added together
What are the different hyperpolarising postsynaptic potentials
Fast IPSP via ionotropic receptor
Slow IPSP via metabotropic receptor
What are the different depolarising postsynaptic potentials
Fast EPSP via ionotropic receptor
Slow EPSP via metabotropic receptor
What is synaptic integration
Summation of synaptic inputs to decide if cell reaches threshold to depolarise
What do the stages of an action potential involve
Ligand binding causes Na+ to open- cell depolarises
Na+ channels close- K+ open- cell hyperpolarises
Na+ channels reset- cell depolarizes to resting potential
What are the properties of Action potentials
Threshold
All cell depolarise or none
Self-propogating
Refractory period
Travel slowly
Encoded stimulus in firing frequency
What mediated AP firing
Voltage gated channels
What are two ways to speed up conduction velocity
Large Axons- Na+ channels spaced out
Myelination- Layers of myelin around axon
Causes: Increased membrane resistance-less current leaked out
Decreases capacitance-less current wasted up charging
AP spread node to node
What are the different nerve fibre types
What is in the structure of neuromuscular junction
Presynaptic terminal with vesicles (containing acetylcholine)
Synaptic cleft
Postsynaptic end plate
What are the stages of the Neuromuscular junction
- Action potential in motor neuron
- Opens Ca2+ channels in presynaptic terminal
- Fusion of vesicles
- Ach diffuses across synaptic cleft
- ACh binds to ACh receptor(nicotinic)
- Opens ligand gated Na+/K+ channels
- Evokes end plate potential
- Depolarises membrane to threshold
- Opens Na+ channels
- Evokes AP
- Muscle contracts
- ACh cleaned by ACh-ase
What are the key characteristics of Neuromuscular junction
Na/K+ channels evoke end plate potential
Large graded potential
No synaptic integration
What prevents repeated firing once AP has been fired
Inhibitory neurotransmitter
What is the difference between mono and polysynaptic reflex
Mono synaptic doesnt involve interneurones
Polysynaptic involves interneurones
Describe the consequences of demyelinating diseases
Attack myelin sheath
Decreased membrane resistance
Increased membrane capacitance
Failed conduction
MS in the CNS and Guillain-Barré syndrome in PNS
