NNN 2 Flashcards
what is a quanta
refers to the release of neurotransmitter from single vesicle
the number of quanta released varies with the stimulus
the number of quanta released by stimulation of the neuron can vary for every neuron, for every stimulus.
Factors influencing the outcome of neurotransmission
1) Neurotransmitter may be excitatory or inhibitory - (GABA, glutamate)
2) A neuron may have different receptor types responding to a single presynaptic event
3) The influence of a synapse depends on the distance the current has to travel to the neurones trigger zone
4) Neurotransmitter is released in discrete packages called quanta; varying quanta may be released
5) A neuron typically has multiple synaptic contacts from multiple cells
6) Excitatory and inhibitory synapses have competitive actions
what are strategies to increase quantal release extensive innervation
e.g. purkinje cell - inferior olivary neuron synapse - climbing fiber innervation of purkinje cells, average 500 synapses formed by a single IO - PC cell
the inhibitory basket cell. common in the cerebellum, hippocampus and cortex
mega humongous pre synapse e.g. the Calyx of Held synapse
what is the purkinje cell - inferior olivary neuron (PC - ION) synapse
a unique crucial connection within the cerebellum, a brain region involved in motor coordination and learning. The ION (inferior olivary neuron) provides powerful excitatory input to purkinje cells. Increasing quantal release at this synapse involves strategies to enhance the release of neurotransmitters, such as glutamate, from the presynaptic terminals of the inferior olivary neurons onto the postsynaptic Purkinje cells.
what are basket cells
a type of inhibitory interneuron found in the central nervous system particularly the cerebral cortex and cerebellum. Play crucial role in regulating the activity of surrounding neurons by inhibiting their firing. Basket cells are named after their appearance as their axonal arborization forms a “basket-like” structure around the cell bodies of other neurons.
what is the calyx of Held synapse
specialized synapse found in the auditory brainstem, specifically in the cochlear nucleus and the medial nucleus of the trapezoid body. It is known for its remarkable size and its role in transmitting auditory information with high temporal precision.
how many parallel fibers come into contact with a single purkinje cell
400
what is a climbing fiber
a type of excitatory axon that forms synapses onto purkinje cells in the cerebellum, a region of the brain in motor control and coordination. The climbing fibers originate from the ION, located in the medulla oblongata of the brainstem. These fibers play a crucial role in regulating the activity of purkinje cells and consequently, contribute to motor learning and coordination.
what does simultaneous activation of excitatory and inhibitory inputs do
results in a reduced EPSP (inhibitory input shunts the excitatory current)
in the absence of an inhibitory input neurone discharges are what
rhythmic.
An inhibitory input suppresses some action potentials resulting in a distinct pattern of discharge
what is the synaptic intergration
summation of post synaptic membrane potentials allows multiple synaptic inputs to be integrated
what is spatial summation
Spatial summation involves the integration of signals from multiple presynaptic neurons that are active simultaneously. If the combined effect of these signals, whether excitatory or inhibitory, reaches the threshold, it can trigger an action potential in the postsynaptic neuron.
EPSPs and IPSPs are spatially distributed but timed together.
what is temporal summation
EPSPs occur in temporal sequence such that threshold is triggered.
Temporal summation occurs when a neuron receives repeated signals from the same presynaptic neuron over a short period. Even if individual signals are subthreshold (below the threshold for triggering an action potential), their cumulative effect over time can reach the threshold and lead to the generation of an action potential
Practice feedback and feedforward loops
what is low threshold spiking
type of neuronal firing pattern characterized by the generation of action potentials in response to relatively small depolarizing inputs. Neurons exhibiting low-threshold spiking typically have a lower threshold for firing compared to regular spiking neurons.
what is fast spiking
specific firing pattern exhibited by certain types of neurons, characterized by the ability to generate action potentials at a high frequency. Neurons with fast-spiking properties are capable of firing action potentials with rapid and precise timing
name the different physiological properties between LTS and FS
high frequency firing pattern for FS, lower for LTS
adaptation for LTS none or minimal for FS
FS fires spikes at the end of the current pulse, LTS at the start
FS requires higher current stimulation, LTS lower
what do both LTS and FS release
these interneurons release GABA. stimulation of LTS evokes hyperpolarizing responses in FS and vice versa
what do FS cells release GABA onto
other FS cells
LTS cells
RS cells
what do LTS cells release GABA onto
FS cells
RS cells
but not LTS cells
what do RS cells release glutamate onto
LTS cells
RS cells
FS cells
which cells are electrically coupled
FS and LTS cells are electrically coupled
but RS cells are not
what is electrical coupling
refers to the direct flow of ions and electrical current through gap junctions, specialized channels that connect the cytoplasm of adjecent cells
what are consequences of electrical coupling between LTS cells and also FS cells
synchronization of activity. when one neuron depolarises, the electrical current flows directly to the connected neuron, leading to coordinated firing.
what is ACPD
a metabotropic glutamate receptor agonist, evokes Aps and subthreshold oscillations from the LTS cell network.
what is used to measure synchrony of electrical coupling
cross-correlation analysis
what does ACPD stimulation activate
LTS cells which cause synchronous IPSPs in FS cells
what is a granule cell
types of neuron found in various regions of the brain mainly the cerebellum. Granuales receive excitatory input from mossy fibers, which carry sensory information from the spinal cord and brainstem to the cerebellum. Glutamate is the neurotransmitter for granule cells.
what are parallel fibers
nerve fibres found in the cerebellum, a region of the brain that plays a crucial role in motor control, coordination and certain cognitive functions.
where are parallel fibres located and what is their function
parallel fibres are axons of granule cells, which are the smallest and most numerous type of neuron in the cerebellum. These fibers run perpendicular to the long axis of the folia (convolutions) in the cerebellar
transmit information from granule cells, which are the main output neurons of the cerebellar cortex
what is responsible for purkinje cell simple spikes (SS)
parallel fibres
what is each purkinje cell each innervated by
climbing fibres. they make approximatley 600 synaptic contacts as it entwines the purkinje cell dendritic tree. Climbing fibres regulate the relativley low discharge of purkinje cell complex spikes CSs; (0.5 - 8 imp/s)
what is the cerebellar circuit
a neural network located at the back of the brain, plays crucial role in motor control, cognitive function.
what are the input sources of the cerebellar circuit
mossy fibres - carry sensory information from various sources, including spinal cord
climbing fibres: covey error signals and play a critical role in motor learning and adaptation.
revise cerebellar circuit
