10 - Sleep and Wake Cycle

Question 1

the change from sleep to wakefulness is mediated by what?

Answer 1

reticular activiating mechanism

Question 2

the biological clock detects what?

Answer 2

decreases in light levels as night approaches

Question 3

what is the site of circadian control of homeostatic function?

Answer 3

SCN - suprachiasmatic nucleus

Question 4

where is the SCN located?

Answer 4

anterior hypothalamus

Question 5

what happens when the SCN is activated?

Answer 5

• impulse travels to synapse in paraventricular nucleus of hypothalamus
• descend into IML zone (intermediolateral) in lateral horns of spinal cord
• modulates neurons of superior cervical ganglia
• axons project into pineal gland = melatonin secretion

Question 6

what happens to melatonin as light in the environment decreases?

Answer 6

increases

Question 7

what system mediates wakefulness and increases arousal?

Answer 7

ascending arousal system

Question 8

what are the two components of the ascending arousal system?

Answer 8

1. thalamus to cerebral cortex
2. lateral hypothalamus –> basal forebrain –> cerebral cortex

Question 9

what is orexin?

Answer 9

a neurotransmitter that regulates arousal, wakefulness and
appetite

Question 10

during REM sleep, what happens to the activity of orecin neurons?

Answer 10

reduces

Question 11

what does sleep consist of?

Answer 11

non-REM stages and REM stage

Question 11

how is sleep different to a coma or general anaesthetic?

Answer 11

sleep is readily reversible

Question 12

how many sleep cycles are there usually in a 8h sleep period?

Answer 12

4-6

Question 13

how much of the sleep cycle is spent in non-REM sleep? how much of the sleep cycle is spent in REM sleep?

Answer 13

non-REM = 80%
REM = 20%

Question 14

non-REM sleep is induced by what?

Answer 14

• GABA neurons in hypothalamus
• serotonin from raphe nuclei

Question 15

non-REM sleep is characterised by what on an EEG?

Answer 15

progressively sychronised EEG

Question 16

how many stages of non-REM sleep are there?

Answer 16

4

Question 17

Fill in this table of NREM sleep

Answer 17

Question 18

REM sleep is characterised by what change on EEG?

Answer 18

synchronised > desynchronised EEG

Question 19

during NREM sleep what happens to skeletal muscle?

Answer 19

skeletal muscles relax and maintain their tone

Question 20

what happens to muscle tone in REM sleep?

Answer 20

atonia - loss of muscle tone

Question 21

non-REM sleep lasts roughly how long?

Answer 21

90 mins

Question 22

when do most dreams occur?

Answer 22

REM sleep

Question 23

what are the two theories about why we sleep?

Answer 23

• theory of restoration
• theory of adaptions

Question 24

what is consciousness?

Answer 24

alert cognitive state in which ou are continualy aware of external and internal environements

Question 25

for a person to be fully conscious they must be both what?

Answer 25

awake (ascending reticular activating system) and aware (functioning cerebral cortex)

Question 26

what is a concussion?

Answer 26

reversible state of unconsciousness that lasts only a brief amount of time, without strucutral or pathological alteration

Question 27

what is a coma?

Answer 27

profound state of unconsciousness that is associated with depressed cerebral activity

Question 28

what scale is used to assess consciousness>

Answer 28

GCS

Question 29

what are the 3 sections of the GCS?

Answer 29

• eye opening
• verbal response
• best motor response