Brain Rhythms

Question 1

What neurons do EEGs take readings from primarily?

Answer 1

Pyramidal neurons in the cerebral cortex being synaptically excited. EEGs do not record from single neurons and electrodes are placed in pairs to observe differences between two or more points on a scalp

Question 2

Why must many neurons be sampled from in an EEG recording?

Answer 2

Single neuron electrical output is really small and must travel through non-neural tissue like the meninges and skull.

Question 3

What type of recording can sense the magnetic fields of neurons firing in synchrony and their location in the brain?

Answer 3

Magnetoencephalography (MEG)

Question 4

What is the frequency range of beta waves, what do they signal?

Answer 4

Anything greater than 14 Hz, activated cortex

Question 5

What is the frequency range of alpha waves, what do they signal?

Answer 5

8-13 Hz, quiet, waking states

Question 6

What is the frequency range of theta waves, what do they signal?

Answer 6

4-7 Hz, some sleep states

Question 7

What is the frequency range of delta waves, what do they signal?

Answer 7

Less than 4 Hz, large in amplitude, hallmark of deep sleep

Question 8

What are two ways in which synchronous rhythms of the brain can arise?

Answer 8

1. From thalamic pacemaker cells
2. From the collective behaviour of all participating neurons (think audience clapping falling in sync) by mutually inhibiting and exciting each other

Question 9

What is a generalized seizure?

Answer 9

A seizure of the entire cerebral cortex of both hemispheres

Question 10

What is a seizure that only affects a circumscribed area of the cortex called?

Answer 10

A partial seizure

Question 11

Why do EEGs record very large patterns during seizures?

Answer 11

Neurons within an effected area fire with synchrony that is not seen during normal behaviour

Question 12

What is the definition of sleep?

Answer 12

Sleep is a readily reversible state of reduced responsiveness to, and interaction with, the environment.

Question 13

What is sleep paralysis called in clinical terms?

Answer 13

Atonia, a complete loss of muscle tone

Question 14

What is more active during REM sleep, the sympathetic or parasympathetic ANS?

Answer 14

Sympathetic, causing increased (though irregular) heartbeat and breathing.

Question 15

What are ultradian rhythms? How do they differ from circadian rhythms?

Answer 15

They are transitions through the cycles of sleep, therefore they are much quicker than circadian rhythms.

Question 16

What type of brain rhythms are prevalent during REM sleep?

Answer 16

beta

Question 17

What are spindles and K complexes? What stage of sleep do they occur in?

Answer 17

Spindles - High frequency
K complex - High amplitude

Occur during stage 2 non-REM sleep

Question 18

How many stages of sleep are there in a single cycle?

Answer 18

4, non including REM and awake.

Question 19

Lesioning the ascending reticular activating system (midline tegmentum and other) causes what?

Answer 19

A state similar to non-REM sleep

The locus coeruleus in also involved in waking, along with serotonergic diffuse modulatory systems

Question 20

What diffuse modulatory systems go silent and become active with the onset of REM?

Answer 20

Silent

• Serotonergic
• Locus Coeruleus (norepinephrine)

Active
- Cholinergic

All within the brain stem, especially the pons. These may regulate REM sleep

Question 21

What are common molecules that stimulate sleepiness?

Answer 21

Peptides that effect the immune system such as interleukin-1 and muramyl

Adenosine levels increase during the day with increasing sleepiness and decrease during sleep

Question 22

Caffeine is an antagonist to what type of receptor?

Answer 22

Adenosine receptors

Question 23

How does adenosine work to increase sleepiness?

Answer 23

It inhibits diffuse modulatory systems that maintain wakefullness, the locus coeruleus, serotonergic and cholinergic ones

Question 24

What are zeitgebers?

Answer 24

German for time givers. Things that can calibrate a biological clock, such as the rise and fall of the sun.

Question 25

Which nuclei are human’s biological clock for wake and sleep? Where is it located?

Answer 25

The suprachiasmatic nuclei, located in the hypothalamus. Smallest neurons in the brain

Question 26

How can a retina without rods and cones detect light levels?

Answer 26

Ganglion cells with melanopsin directly innervate the suprachiasmatic nuclei in the hypothalamus.

Question 27

What happens when suprachiasmatic nuclei neurons are isolated form the rest of the brain? What happens when they are treated with tetrodotoxin?

Answer 27

Isolated
- Still keep 24 hour cycle, can’t be calibrated with light

Tetrodotoxin
- Don’t make action potentials, but still keep 24 hour cycle

Question 28

How do clock genes work?

Answer 28

mRNA is made and then translated into protein which stops transcription. When transcription is stopped, the protein is not made and the inhibition is slowly lessened until more protein inhibitor is made. This whole cycle takes about 24 hours.