10 - Neural Circuits Flashcards
Neural circuits
A group of neurons who are connected by synapses and carry out a specific function when they are activated.
3 important parameters
- that determine connection strength of neurons
- DUS enable specific neural circuits
- (currents)
1) Maximum current
2) Synaptic current
3) Time currents
Parameters
Features that can influence how neural circuits work, so how neurons are connected
Current
is electrical flow
Voltmeter allows to see ..
How a neuron is spiking (sending action potentials)
Maximum current
a parameter/property that determines the connection (synapse) strength between neurons
Synaptic current
Connection strength of neurons.
Depends on the concentration of neurotransmitter (in the cleft) and number of ion channels
Time constant of a synapse
Parameter for connection strength neurons
Indicates for how long the synapse is active following an incoming action potential.
What is important in the connection strength of neurons
Synaptic current, time constant of a synapse
High resistance of membrane for potassium, means
- not much current
- not much channels
EPSPs
EXCITETATORY POST SYNPATIC POTENTIAL
Inhibitory neurons
Cause IPSPs, hyperpolarization occurs, inhibits cell and then cannot produce action potentials
Time delay from one neuron to the next, how does this create a AP?
The differences in pace, one neuron is slow and other is fast. But the slow one is first activated and then second the other. They end up arriving at the same time and creating an action potential as a result in the next neuron. HAPPENS A LOT IN NERVOUS SYSTEM
lateral inhibition
inhibition to the side (lateral)
Audition is about perceiving
sound, which is the vibration in air
Amplitude
How loud a sound is.
Depends on pressure variation of the sound, amplitude is totale uitstrekking van wave.
Frequencies of sound
Corresponds to pitch, depends on how often the tones are (Quick up and down in the wavelength means high frequency)
`important in perception
Frequency is important in perception, it lets us distinguish between
Word and music e.g.
Function midyear
To get air vibrations in to the fluid vibrations
Cochlea base is sensitive to …. frequency sounds
High
Cochlea apex (end) is sensitive to … frequency sounds
Low
Cochlea membrane respondes differently to different frequencies according to place because
The psychical characteristics of membrane change over the length go the cochlea
- Narrow and stiff at base (high freq.)
- Thin and sloppy at end (low freq.)
Tonotopic mapping (of cochlea)
Mapping is according to tone frequency
mechanosensitive receptor cells are
sensitive to vibration
How are sound/auditory frequencies coded
1) Place coding
2) Temporal coding
3) Population coding
DIFFERENT SOUNDS EXCITED NEURONS IN DIFFERENT PLACES
Place coding
high frequencies excite membrane at beginning, low frequencies excite membrane at end. The hight of the frequency will determine in which place there is excited.
Temporal coding
Phase of acoustic waveform.
(Je hebt een waveform van geluid, waarin je een top hebt, op dat moment fired een neuron. In het dal van de wavelength wordt er niet gevuurd.)
Population coding
Collective firing of neurons
Rate coding
Intensity of a sound
Time delay
How much time it takes from 1 neuron to another
Duration
How long a signal lasts
Horizontal localization is sound coming from
the sides or front
If the time constant of an excitatory synapse increases, the post synaptic neuron:
Is more likely to fire
How does a neuron normally excite some neurons and inhibit other neurons at the same time?
By using interneurons for part of the connections
A function of lateral inhibition is to
Localize stimulus ‘edges’
A function of inhibition
Prevents too much excitatory epileptic seizures
The basilar membrane in the inner ear maps
Different frequencies to place
What is temporal coding in audition? Action potential patterns correspond to
Sound wave form phase
High frequencies are localised in horizontal space by determining the difference in
Sound intensity between the ears
Low frequencies are localised in horizontal space by determining the difference in
Sound latency between the ears
Latency
Differencing in timing (how fast or slow (sound is))
How can sound latency between the two ears be determined
A circuit with delay lines and coincidence detectors
How are different odours coded in the nervous system
Pattern coding
Spatial integration
Neurons will only fire AP to rest of position if they get input from both places at the same time.
Neurons are coincidence detectors
Pattern coding
You map a number of different receptor cells and combine them to code for many more compounds
(Each odourant has multiple targets for receptor binding sites. Activation pattern across the 4 receptors types thus enables 16 different odorant’s to be coded.
Why do neurons differ in firing speed
Because of myelination, it results in delay lines
Capacitance
Ability to temporarily hold on to charge
delay lines
a device in which a known delay time is introduced in the transmission of a signal. An acoustic delay line delays a sound wave by circulating it through a liquid or solid medium.
