Nerves Flashcards
Axon Hillock
Critical Threshold
All the information for making action potentials is arranged
Closer the stimulus to axon hillock the less it degrades
Glia
Astrocytes - maintain external neural environment, surround blood vessels and maintain BBB
Microglia - Phagocytic hoovers mapping up infection
Oligodentrocytes - Form myelin sheaths in CNS
Graded Potential Examples
Determine when an Action Potential is Fired
Generator Potential at sensory receptors
Post-synaptic Potentials at synapses
Endplate Potentials at neuromuscular Junction
Pacemaker Potentials in pace make tissues
Graded Potential Examples
Determine when an Action Potential is Fired*
Generator Potential at sensory receptors
Post-synaptic Potentials at synapses
Endplate Potentials at neuromuscular Junction
Pacemaker Potentials in pace make tissues
Graded Potential Properties
Graded (signal stimulus intensity in their amplitude)
Electrotonic Potentials
Decremental Potentials
Non-Propagated Potentials
Local Potentials
Can summate (Temporal, Spatial) - Synaptic Integration
Hyperpolirising Postsynaptic Potentials
Cl- Fast IPSP
K+ Slow IPSP
GABA, Glycine
Depolarising Postsynaptic Potentials
Block leaky K channels
Open Na and K - non specific monovalent cation channels
Ligand-gated ion channels
Postsynaptic potentials produced by a neurotransmiter opening or closing ion channels.
Voltage-gated ion channels
Action potentials are produced by depolarisation of the membrane potential opening ion channels
Spatial Summation
a + b synaptic integration
Temporal Summation
b + b synaptic integration
Action Potentials
They have a threshold They are all or none They cannot encode stimulus intensity in their aplitude only in their frequency Self Propagate Have a refractory period Voltage Gated Travel Slowly
Aa Aβ Aγ Aδ B C
Nerve Fibres MOST SENSITIVE TO ANOXIA LEAST SENSITIVE TO ANAESTHETICS Aa Proprioception, Motoneurones Aβ Touch, Pressure Aγ Motorneurones of muscle spindles Aδ Touch, Cold, ''fast'' pain B preganglionic autonomic fibres C Heat, ''slow'' pain
Refractory Period
Period following stimulation during which a nerve or muscle is unresponsive to further stimulation
The neuromuscular junction
Action potential in motor neurone
Opens voltage-gated Ca2+ channels in presynaptic terminal
Triggers fusion of vesicles
Acetylcholine (ACh) released
Diffuses across synaptic cleft
Binds to ACh (nicotinic) receptors
Opens ligand-gated Na+/K+ channels
Evokes graded (local) potential (end plate potential)
Always depolarises adjacent membrane to threshold
Opens voltage-gated Na+ channels - evokes new AP
ACh removed by acetylcholinesterase
