Nerves Flashcards
Describe the anatomical organisation of the nervous system
Central nervous system- brain, spinal cord
31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coxyl)
Peripheral nervous system- autonomic (parasympathetic & sympathetic), somatic
Describe structure of a neuron
Dendrites- information
Soma- cell body
Intitial segment- action potential
Axon- sends action potentials, presynamptic terminals
Define different types of glia
Non- neuron cells of the nervous system
E.g. nodes of rangier, Schwann cells, satellite cells, Astro types, oligodendrocytes,micro glib, ependymal cells
What causes the resting membrane potential to be reached
Leaky K+ channels causes K+ to leak out of the cell down its conc. gradient which builds up an electrical gradient.
Describe the resting membrane potential
When equilibrium is reached ( when the electrical gradient is equal and opposite to the conc. gradient)
What equation is used to predict the equil
The Nernst equation E=RT/zF ln [ion]o/ [ion]i
Simplified: E= 61 log10 [ion]o/ [ion]i
Give examples of graded potentials
Generator- sensory, postsynaptic- at synapses, end plate- neuromuscular junctions,pacemaker- pacemaker tissues
Describe the properties of graded potentials
Graded- stimulus= response
Decremental- become smaller as they travel along membrane (useful for short distances)
Depolarising- (less negative inside cell) can open channels that excite or inhibit
Hyperpolarising- more negative inside cell
Summate- when synapses postsynaptic potiential joins to create a bigger graded potiential
How are EPSPs generated (excitatory postsynaptic potential’s)
By opening NA+/K+ channels or closing leaky K+ channels
How are IPSPs generated (inhibitory postsynaptic potentials)
Opening Cl- channels or K+ channels
Explain the role of synaptic intergration in neuronal function
Evoke slow or fast EPSPs/ IPSPs, adding them together causes the cell to reach threshold and fire an action potential or stops it from reaching threshold
Explain the properties of action potientials
Have a threshold, are all or none, can only encoded stimulus intensity in their firing frequency, have a refractory period (period after firing an action potential in the excitable state when it cant fire another) , self- propagating, travel slowly
How is an action potiential generated
Depolarising state- voltage gated Na+ channels
Hyperpolarising state- voltage gated K+ channels
How can action potientials be sped up
Large diameter axons (allows NA+ channels to be more spaced along the membrane) , myelination
Describe demyelination diseases
Multiple sclerosis in the CNS, gullain- barre syndrome in the PNS. Attack myelin sheath- decreased membrane resistance, conduction failure
