Neuronal Signalling and Brain Rhythm (Voltage-gated channels and Action…
Neuronal Signalling and Brain Rhythm
The opposite is TMS (transcranial magnetic stimulation) application of an external magnetic field induces a current flow (magnetic induction)
Functional Zones of nuerons are determined by the ion channels it controls
Dendrites Soma are chemically gated channels, Axon hillock and Axons are voltage-gated Na and potassium channels, Voltage-gated CA channels are int the terminal buttons.
Ionic Basis of Resting potential
4 major ionic species
Na, K,Cl, and organic matter A-
4 major forces
Selective permeability of the nueron membrane
Sodium potassium pump
Membrane is a phospholipid bilayers like water Hydrophilic hate water hydrophobic
Different Receptors- binding of neurotransmitter causes a conformational change in the channel protein.
G protein coupled receptors(Indirectly coupled)
Glutamate-major excitatory nuerotransmitters in CNS
Ionic species environment
Inside the cell -Negative
Organic protein- with a concentration and electrical gradient of wanting to go outside of the cell .
Potassium+ - concentration gradient wanting to go outside of the cell whilst it s electrostatic gradient wants to go inside.
Outside the cell is mainly -positive
Na +- Concentration and electrostatic gradient all wants to go inside the cell
Cl- concentration gradient wants to go inside the cell but electrostatic wants to go outside.
Depolarisations and repolarisation
Depolarisation- Concentration gradient and Electrostatic gradient goes into the cell.
Repolarisation- Concentration and electrostatic gradient goes outside of the cell.
Potassium also goes outside of the cell
Voltage-gated channels and Action potential
Sodium and Pottassium
Myelinated Axons -Voltage gated potassium and sodium channels
Voltage gated calcium channel
Presynaptic channel- Calciium
Binds to the vesicles releasing it of the cytoskeleton, bringing it to the presynaptic terminals.
Post Synaptic channels -Acetycholine
Rhythms of the brain - population of neurones that align their activities to societies
Classes of Biological Rythms
Circadian-Sleep/wake, growth hormone secretion, cortisol secretion
Suprachiasmic nucleus of the hypothalamus controls the circadian clock
Intrinsically photosensitive retinal ganglion cells
Project to suprachiasmatic nucelus and other control centres
Infradian -Menstrual rhythms, hibernation
Ultradian- Periods of less than a day brain metabolic rhythms
Circardian Rhytmicity- sleeping and feeding patterns, Body Temperature, hormone production, cell regeneration
Entrainment- Lock of rythm to outside world
Zeitgeber (time giver)
Photoperiodism (sensitivity to daylenghth)
Theta (4-8 HZ) sleep but also waking memory and spatial navigation, Alpha 8-10 hz , Beta 13-30 hz, Gamma 35-80 hz. Sleeping rytms- deep sleep, general anaaesthesia
Rolandic mu Rhythm- idling rhythm when motor cortex is not doing anything.
Hippocampal Theta rhythm
Rat hippocampus generates a 5-10 hz electrical rhythm called theta rhythm
Place cells increase their firing rate when rats are in a specific region of the environment (Place field). The place cells will fire at a specific phase of a theta cycle
Theta oscillation is a timing mechanism that ties together information in a temporal sequence. Code of representing a multiple items in a ordered ay
Default Mode Network- Areas that decreases during task performance;
Default Mode (Resting State) Network- Areas that decrease activity during task performance.
Spontaneous fMRI BOLD signal oscillates slowly over many seconds during resting state.
The coherence of resting oscillations reveals functional connectivity that parallel task-related activity decreases.
Middle of the brain post cingulate, middle lobe, temporal lobes, less active when your in a task
Focus on evoked brain response to a greater interest in spontaneous intrinsic brain activity.
Speech perception and cortical oscillations emerging computational principles (intrinsic oscillations phase-lock to speech signals)
Theta oscillation locks to syllable rate, gamma (40HZ locks to phoneme rate)
Oscillatory phase locking provides a mechanism to parase and decode speech signals at diffirent times scales (multiplexing).
Restructring of power, intrinsic oxcillation of your brain track and lock into speech signals
Magnetoencephalography (superconducting quantum interference Device (SQUID)
ION currents in nuerons create electromagnetic fields that can be measured at distance.
Cellular currents in an active neuron population give rise to extra cranial electric potentials and magnetic fields
Imaging Principles and Methods
Pet -nueronal metabolism
FmMRI-regional blood blow
EEG-electric fields from ionic currents