Sleep and consciousness

Question 1

Describe the organisation of neurons in the brain cortex [1]

Answer 1

Organized in layers, or laminas, parallel to the surface of the brain

Question 2

Which lamina layer predominately generates the current that EEGs detect

Layer 1
Layer 2
Layer 3
Layer 4
Layer 5

Answer 2

Which lamina layer predominately generates the current that EEGs detect

Layer 1
Layer 2
Layer 3
Layer 4
Layer 5

Question 3

What are EEG recordings detecting when placed on the head? [1]

Answer 3

EEGs detect the summated post synaptic potentials create a field with positive and negative poles (dipole). The dipole vector, or direction of energy flow, is parallel to the orientation of the pyramidal cells generating the activity

EPSP (Excitatory postsynaptic potential; Na+ & K+ entering cell and source of current into extracellular medium)

Versus

IPSP (inhibitory postsynaptic potential; flow of negatively charged chloride ions entering the cell and source of current in the extracellular medium)

Question 4

Most of the electrical activity recorded in the EEG is generated by pyramidal neurons similarly oriented in space with synchronous firing created from which areas? [2]

Answer 4

created by thalamo-cortical oscillations:

• thalamic input from the sensory systems
• non-specific thalamic input generates rhythmic oscillations

Question 5

In wakefulness EEG is more [desynchronized / synchronized]?

In sleep the EEG is more [desynchronized / synchronized]?.

Answer 5

In wakefulness EEG is more desynchronized.

In sleep the EEG is more synchronized.

Question 6

Which area of the brain alters the frequency / desynchronizes the of EEG during wakefulness? [1]

Answer 6

Reticular activating system

Question 7

Which of the following EEG frequencies are responsbile for ‘active wakefullness & REM sleep’?

Gamma
Beta
Alpha
Theta
Delta

Answer 7

Which of the following EEG frequencies are responsbile for ‘active wakefullness & REM sleep’?

Gamma
Beta
Alpha
Theta
Delta

Question 8

Which of the following EEG frequencies are active during for ‘sleep & meditation’?

Gamma
Beta
Alpha
Theta
Delta

Answer 8

Which of the following EEG frequencies are active during for ‘sleep & meditation’?

Gamma
Beta
Alpha
Theta
Delta

Question 9

Which of the following EEG frequencies are active during ‘active information processing’’?

Gamma
Beta
Alpha
Theta
Delta

Answer 9

Which of the following EEG frequencies are active during ‘active information processing’’?

Gamma
Beta
Alpha
Theta
Delta

Question 10

Which of the following EEG frequencies are occur while resting with the eyes closed’?

Gamma
Beta
Alpha
Theta
Delta

Answer 10

Which of the following EEG frequencies are occur while resting with the eyes closed’?

Gamma
Beta
Alpha
Theta
Delta

Question 11

Which are the following EEG frequencies?

Answer 11

Question 12

EEG

Which of the following is eyes closed and eyes open?

Answer 12

A: eyes closed

B: eyes opened

Question 13

What does it mean physiologically if the EEG shows a ‘desynchronised’ appearance versus ‘synchronised’ appearance? [1]

Answer 13

Desynchronised:
* If individual neurons (eg A,B, C) are firing out of phase with each other

Synchronised:
* If individual neurons (eg A,B, C) are firing in phase with each other
* EEG shows high amplitude ‘slow wave’ appearance

Question 14

Describe how EEG recordings change from awakefullness to sleep and how these change during sleep. [4]

Answer 14

Awake: high frequency, unsynchronised EEGs

Stage 1: theta waves
Stage 2: sleep spindles
Stage 3 - 4: delta waves
REM: low voltage, random fast sawtooth waves

Then repeats 4 or 5 times per night

Question 15

Describe EEGs in epilepsy patients during an epileptic attack [1]

Answer 15

Epilepsy – waves are hypersynchronized: very high amplitude: causes patients to lose consciousness.

Question 16

Label A & B

Answer 16

A: alpha waves
B: beta waves

Question 17

Very large ‘theta’ and ‘delta’ slow waves can occur in which populations [2]

Answer 17

Very large ‘theta’ and ‘delta’ slow waves can occur in** young children and in sleeping adults**

Question 18

Label A & B

Answer 18

A: Awake normal

B: epileptic seizure

Question 19

Spindle waves are present in EEG waves in which stage of sleep:

Stage 1
Stage 2
Stage 3
Stage 4

Answer 19

Spindle waves are present in EEG waves in which stage of sleep:

Stage 1
Stage 2
Stage 3
Stage 4

Question 20

What is the function of slow wave sleep? [5]

Answer 20

Increased growth and maintenance of the immune, nervous, skeletal and muscular systems:

• Growth hormone is secreted mostly during slow wave sleep
• Wound repair and regrowth of injured tissue
• Glycogen stores in the brain also increase during slow wave sleep.
• Declarative and emotional memory consolidation
• Waste products removed from CSF

Question 21

Which hormone is released by the pineal gland? [1]

Answer 21

melatonin is released from the pineal gland into the blood and CSF

Question 22

Describe the role of melatonin during sleep [2]

Answer 22

Powerful free radical scavenger: neutralises the free radicals that have accumulated during waking, especially in neurons

(Maintaining GABA function

Preventing seizures in the brain)

Question 23

What is the function of REM sleep ? [3]

Answer 23

• Consolidate long-term memory (LTM)
• Removes unwanted memories or connections from the brain during sleep, “defragmenting” memories, strengthening wanted and deleting unwanted connections in long term memory
• Helps to cope with lifes stresses: increases during periods of stressful experiences

Question 24

Which area of the brain is key for controlling sleep and wakefulness [1].

Answer 24

Reticular formation

Question 25

The action of the reticular formation is controlled by signals from which organ? [1] How does the RFs structure help with its function? [1]

Answer 25

**hypothalamus** The reticular neurons have long and **widely branching axons that project diffusely** to most of the **cerebral cortex** Their activity keeps us awake and alert; when these neurons are switched off we sleep.

Question 26

In which part of the hypothalamus is the BBB 'leaky'? [1]

Answer 26

preoptic area

Question 27

# Pre-optic system State and explain three molecules that are stimuli for sleep [3]

Answer 27

1. **Adenosine**: high levels increase sleep 2. **Ghrelin**: reduces desire for sleep 3. **Leptin**: increase sleepiness

Question 28

Describe the pathway of the suprachiasmatic nucleus (SCN) involved in circadian rhythm [4]

Answer 28

Inputs from branches of **optic nerve** fibres leaving the retina synapse at **suprachiasmatc nucleus** Goes via **superior cervical ganglion** SVG synapses onto the **pineal gland** Pineal gland increases **melatonin** during the night

Question 29

Which of the following EEG frequencies are active during 'active information processing''? Gamma Beta Alpha Theta Delta

Answer 29

Which of the following EEG frequencies are active during 'active information processing''? **Gamma** Beta Alpha Theta Delta

Question 30

How does melatonin synchronise all the clocks of the body? [2]

Answer 30

All cells have own individual clocks Causes increase in **BMAL** and **CLOCK** **transcription products** in cytoplasm of cells that controls each cell clock

Question 31

State two systems that maintain wakefulness [2]

Answer 31

**1. The Orexin system**: * orexin neurons **excite the monoamine neurons** in the brainstem, especially the locus coeruleus and raphe nuclei. **2. Tuberomamillary (TMN) system**: * release **histamine** at their synapses. Are tonically active during wakefulness

Question 32

State the effect of the following on sleep / wakefulness during wakefulness, slow wave sleep (SWS) and REM sleep. * Noradrenaline neurons * Serotonin neurons * Cholinergic neurons

Answer 32

**Noradrenaline neurons:** * they are most active when the individual is aroused for ‘fight or flight’ * During both slow wave (SWS) and REM sleep their activity drops to a low level **Serotonin neurons**: * wakefulness: serotonin neurons fire spontaneously at at steady level that seems **independent of the level of alertness.** * Slow wave sleep: spontaneous activity in the **serotonin neurons is decreased** * REM sleep seratonin activity **ceases completely** **Cholinergic neurons:** * Awake: neurons are spontaneously active. * SWS: decreases to a low level * REM: **increase their activity to the same rate as during alert waking**

Question 33

What does EEG like look during REM sleep?

Answer 33

**motor cortex EEG** is **desynchonised** and just as **active as during waking**: sends motor commands down the **corticospinal tract.** Somehow these commands **do not activate the lower motor neurons.** The only two exceptions are the **extraocular muscles and the muscles of the diaphragm**

Question 34

What is sleep apnea? [1] What pathologies does this lead to? [3]

Answer 34

Motor **muscle paralysis** starts to affect **respiratory** **system**: causes **massive rush of adrenaline** and **person to wake up** Leads to **chronic fatigue** and **depression** Surge in sympathetic activity causes increase in BP: **strokes** due to ruptured BV