Lecture 3: Neural Circuits and Their Function Flashcards
(41 cards)
What is a complete neural circuit?
from sensor (afferent) to effector (efferent) – can involve as few as two neurons
What are action potentials (spikes or nerve impulses) ?
electrical mechanism that nervous systems have evolved that allow for conduction of information across distances
What can extracellular recordings record?
AP – because of their large amplitude
What can intracellular recordings record?
PSP
What are post-synaptic potentials?
signals induced when a neurotransmitter activates receptors at a synapse
What is neuromodulation?
term for synapses whose effects are not simple PSPs
What are three classes of effects that can occur when a synapse is activated?
- excitation
- inhibition
- modulation
What is excitation?
activating the synapse causes EPSP
What is inhibition?
activating the synapse causes IPSP
What is modulation?
activating the synapse causes effects other than simple PSPs
these effects can often be changes to the strength of other neighbouring synapses on the postsynaptic cell – synapse ‘modulates’ its target
When is a synapse considered ‘activated’?
when AP occurs in presynaptic neuron’s axon (and axon terminal), which causes release of neurotransmitter from axon terminal – neurotransmitter will be detected by postsynaptic cell
What is grey matter?
CNS areas with somata and neuropil (dendrites, axon terminals and synapses)
What is white matter?
consists of (myelinated) axons linking the neurons in two or more regions of grey matter
Sensory vs. Motor Neurons
Polarity
SENSORY: often ‘pseudo-unipolar’ – dendrite joins axon, not soma
MOTOR: multipolar – one axon, many dendrites
Sensory vs. Motor Neurons
Location of Somata
SENSORY: outside CNS in dorsal root ganglion
MOTOR: (and dendrites) In ventral grey matter
Sensory vs. Motor Neurons
Location of Axon
SENSORY: enters spinal cord/hindbrain on dorsal side, into dorsal grey matter
MOTOR: Leaves spinal cord via ventral root and travels directly to skeletal muscle cells
Within a circuit, what is a neuron’s activity is generated from?
sum of its inputs across time and space – most neurons (including those involved in simple reflexes), receive synapses from many different neurons, and each synapse is activated every time its presynaptic axon fires an AP
What is spatial activation?
summation in different points of space (different synapses)
What is temporal activation?
summation in same space, but at different times (repeated activation)
What determines the postsynaptic neuron’s activity/output?
integrated total of all recent inputs, such as spatial and temporal summation (measured by APs generated in its axon hillock)
What is convergence?
property of postsynaptic neuron in which multiple inputs converge onto it – receiving information
Where does divergence occur?
in axons
Where does convergence occur?
in dendrites
Where does convergence occur?
in dendrites
