Neurons and Networks Flashcards
Physiological properties of low threshold spiking cells
- lower frequency firing pattern
- adaptation
- fires spikes at the start of the current pulse
- lower current stimulation required
Physiological properties of fast spiking cells
- high frequency firing pattern
- no adaptation
- fires spikes at the end of the current pulse
- higher current stimulation required
Similarities between LTS and FS cells
- occupy same layers in cortex
- both interneurons releasing GABA
- stimulation of one results in hyperpolarissation of the other
- electrically coupled (RS cells are not)
FS cells innervate (release GABA) onto
- other FS cells
- RS cells
- LTS cells
LTS cells innervate (release GABA) onto
- FS cells
- RS cells
- not LTS!!
RS cells innervate (release glutamate) onto
- LTS cells
- RS cells
- FS cells
Synchronicity of LTS cells
- ACPD stimulation activates LTS cells, causing synchronous IPSPs in FS cells
- measure synchrony via cross-correlations
- subthreshold depolarisations in LTS cells reflect synchronous IPSPs in FS cells
- consequently, all RS cells are inhibited synchronously
Granule cells
- cerebellum
- release glutamate
Purkinje cells
- cerebellar cortex
- release GABA
Inferior Olivary cell
- medulla oblongata
- release glutamate
Events necessary for sensation to arise
- stimulation of sensory receptor
- transduction of the stimulus
- generation of nerve impulses
- integration of sensory input
Define receptor potentials
sensory receptors that are separate cells produce graded potentials
Define generator potential
when large enough to reach threshold, it triggers one or more nerve impulses in the axon of a first-order sensory neuron
Mechanoreceptors
sensitive to deformation
Thermoreceptors
detect changes in temperature
Nociceptors
respond to painful stimuli
Photoreceptors
activated by photons of light
Chemoreceptors
detect chemicals in mouth, nose and body fluids
Osmoreceptors
detect the osmotic pressure of body fluids
Sensory unit
primary sensory neuron with all recceptor endings or associated sensory receptor cells
Receptive field
- area of the body surface in which a stimulus leads to activation of the sensory unit
- adding inhibitory interneurons into the circuit can reduce the size of the RF or complicate its response
Two main functions of sensory system
- detection of a signal
- estimation (discrimination of aspects)
What must be estimated from the input
- modality
- intensity
- duration/frequency
- location
How is modality represented in the brain
the most basic mechanism for identifying the nature of a sensory input is via labelled lines
Coding for stimulus duration
- coded by interspike interval
- adaptation = decrease in frequency of APs with sustained stimulus
Stimulus intensity
- larger receptor potential
- activation of more sensory receptors of sensory unit
- activation of sensory receptors on neighbouring sensory units
- coded for by total response generated in sensory organ
Stimulus localisation
topographic mapping -> points close together on the sensory surface are represented closer in the brain
Lateral inhibition
- exaggerates the difference in stimulus intensity detected by adjacent neurons
- aids with localisation
- central neuron forms feed-forward inhibition
- release of GABA inhibits lateral
- signal is strongest at point of stimulus
