Thalamus/Cortex 2: Physiology Flashcards
What (in this lecture) were described as the two main functions of the thalamus?
Relaying information, and controlling wakefulness.
Does the “relay” function of the thalamus only work one way?
No. The cortex provides feedback to the thalamus.
On what does the generation of representations of the world and consciousness depend?
Recurrent loops between the thalamus and cortex…
How do brain waves change, very simplistically, between wakefulness and sleep?
Awake: high frequency, low amplitude
Asleep: high amplitude, low frequency (aka. delta waves)
What’s the pattern of firing in an awake thalamus?
tonic, single spikes that change in response to stimuli
What happens when a thalamus falls asleep?
It begins to fire in rhythmic bursts.
How does the resting membrane potential change in the neurons of a sleeping thalamus? What is the effect of this?
The cells become hyperpolarized. Hyperpolarization allows Ca++ channels to become active -> leading to spikes.
What kind of Ca++ channel is involved in the spikes of the sleeping thalamus?
T type, all-or-nothing, Low-Threshold-Spike (LTS) Ca++ channels…
What two ions are involved in the spikes of sleeping thalami? Which one flows first?
Ca++ and Na+. Ca++ flows first.
With regard to the fidelity with which the thalamus transfers signals, how is a sleeping thalamus different from an awake one?
Waking: faithfully transmits the signal.
Sleeping: thalamus says a bunch of random shit
What are 3 consequences, visible on EEG, of the sleeping thalamus burst-mode?
- Thalamus doesn’t reliably transmit signals.
- Oscillations.
- Large scale synchrony (that produces delta waves).
What do the rhythmic burst of a sleeping thalamus have in common with the heart?
Uses the same ion channels that the pacemaker cells use.
What in the brain makes the thalamus fall asleep?
Loss of signals from other nuclei keep the thalamus cells that normally keep them a little depolarized.
How does the sleeping thalamus suddenly wake up (i.e. when your alarm clock goes off)?
Sensory input from brainstem -> ACh release -> depolarizes hypothalamus cells, shutting down the rhythmic T-type Ca++ channel spikes.
