Studying the Nervous System Flashcards
Diversity in the nervous system is a result of
splice variants (variable messages transcribed from the same gene) and mutations (altered structure of a gene)
cellular components of the nervous system
reticular theory (Golgi): each nerve cell connected to its neighbours by protoplasmic links
neuron doctrine (santiago ramon y cajul): nerve cells are discrete entitites –> cemented by Sherrington’s identification of synapses
Function of neurons
specialised for electrical signalling over long distances and intercellular communication by means of synapses
specialisation of neurons
Presence of an axon
- most have 1 axon
- specialised for relaying electrical signals by action potentials
- local circuit neurons / interneurons = short axon
- projection neurons = long axon
Elaborate arborisation of dendrite
- primary targets for synaptic input from the axon terminals of other neurons
- spinous or aspinous
Degree of convergence and divergence
convergence: number of inputs to a single neuron
divergence: number of targets innervated by any one neuron
Communication between neurons
- axon terminal of the presynaptic neuron is immediately adjacent to the target cell
- communcate through the secretion of molecules (neurotransmitters) from presynaptic termainals that bind to the receptors in the post synaptic cell
Function of glial cells
- modulating the rate of nerve signals propagation
Glial stem cells
- retain capacity to proliferate and generate additional precursors or differentiated glia
- 2 categories (Astrocytes) (Oligodendrocytes)
Specialisation of astrocytes (glial)
- restricted to CNS
- local processes
- maintains an appropriate chemical environment for neuronal signalling - formation of the blood-brain barrier, and secrete substances that influence construction of new synaptic connections
oligodendrocytes
- restricted to CNS
- function: lay down myelin around axons
afferent, efferent and interneurons
afferent: arrive at synapse
efferent: exit synapse
interneurons: local circuit neurons that participate in local aspects of the circuit
Myotatic reflex
- hammer stretches tendon, which stretches sensory receptors in leg extensor muscle
2a) sensory neuron synapses with and excites motor neuron in spinal cord
2b) sensory neuron also excites spinal interneuron
2c) interneurons synapse inhibits motor neuron to flexor muscles
3a) motor neuron conducts action potential to synapses on extensor muscle fibres, causing contraction
3b) flexor muscle relaxes because the activity of its motor neurons has been inhibited - leg extends
Types of electrophysiological recording
Measuring the activity of a nerve cell
Extracellular: electrode placed near the nerve cell of interest to detect its activity
Intracellular: electrode is placed inside the cell of interest (can detect smaller graded changes in electrical potential)
Calcium imaging
records transient changes in intracellular [Ca] with action potential firing
optogenetics
transduction of light energy into chemical signal that activates channel proteins –> opsins modulate membrane currents when they absorb photons, light can be used to control nerve celll activity
