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
Describe the structure of the neuromuscular junction
The synapse between the motor neurons and skeletal muscle
1st step in muscle contraction is to evoke an action potential in skeletal muscle membrane
Describe the process of neuromuscular transmission
Logan gated Na+/K+ evoke end plate potiential
Very large graded potential/ always reaches threshold
No synaptic integration
Post- junctional folds increase voltage gated Na+ channels
Describe common excitatory/ inhibitory transmitters
Acetylcholine, amines (adrenaline, dopamine, serotonin), amino acids ( glutamine, glycine), peptides (endorphins), purines (ATP), gases (nitric oxide)
Explain the range of postsynaptic potientials
Fast EPSPs (ionotropic), slow EPSPs (metatropic), fast IPSPs (iontropic), low IPSPs (metabotropic)
Explain the anatomical arrangement of CNS synapses
Axo- dendritic, axo-somatic, axo-axonal
