Biological Process Flashcards
Endogenous Pacemaker
The sleep-wake cycle is controlled by an a small area of the hypothalamus called the suprachiasmatic nucleus
(SCN). This is our internal ‘biological clock our circadian rhythm’. The electrical activity of the SCN has an endogenous (built in) circadian rhythm.
The SCN sends regular daily impulses via nerves to the pineal gland to produce the hormone melatonin. Melatonin is the sleep hormone - High levels of melatonin stimulate sleep Evidence to support this come Siffre (1962) and Stephen and Zucker (1972).
Exogeneous Pacemaker
Naturally occurring external factors that can affect our sleep-wake cycle the main one being light. The retina of the eye is also connected to the SCN via a nerve pathway. Therefore light also affects the SCN and the pineal gland. Light REDUCES melatonin production. Darkness INCREASES melatonin production
Endogenous sleep regulating substance
A chemical called adenosine builds up in our cerebrospinal fluid during our waking hours which has the effect of increasing the pressure to sleep the more it accumulates. Adenosine inhibits some neurotransmitters associated with wakefulness for e.g serotonin,. Sleep pressure is only released by the act of sleeping itself, during which the levels of Adenosine decrease to normal levels
Oswald restoration theory pt. 1
Oswald (1966) restoration theory of sleep states that the main function of sleep is to allow the brain and body to carry out repair tasks such as:
•Repairing minor bodily injuries
•Removal of waste chemicals in the muscles
•Replenishing neurotransmitters and/or energy in the brain
Newborns can sleep for up to 20 hours a day.
Oswald points out that over 50% of this sleer is usually REM. Rapid growth and development occurs immediately after birth, so increased REM would allow this growth to happen.
Oswald restoration theory pt. 2
There is an increase in growth hormone production during SWS 3 and 4, suggesting sleep has a key role in growth and repair.
Burn injuries on rats heal slower if they are sleep deprived.
Oswald also argued that sleep allows the brain neurotransmitters to ‘normalise, aiding psychological recovery.
Stressed or depressed people tend to sleer for longer periods than healthy people.
This might also explain why people generally report feeling better after a long sleep if they are ill.
Evidence to support this theory is from Shapiro et al (1990), Peter Tripp, and others.
Circadian rhythms
A circadian rhythm is a body rhythm that cycles over 24 hours. Sleep is a perfect example.
The clock is used to anticipate the differing demands of the 24-hour day and fine-tune physiology and behaviour in advance of changing conditions In anticipation of going to bed, body temperature drops, blood pressure decreases, cognitive performance declines and tiredness increases. Before dawn, metabolism is geared up in anticipation of increased activity when we wake
REM and NREM
Stage 1
(NREM) stage between wakefulness and sleep. You are easily woken at this stage and you can still hear noise around you. 5-10 minutes. 4-5% of total sleep Alpha brain waves.
REM and NREM
Stage 2
(NREM) This is light, dreamless sleep. The person’s muscles relax and brain slows.
Snoring may develop if throat and tongue muscles relax too much. Sleep spindles may cause the person to twitch. 20 minutes Theta brain waves
REM and NREM
Stage 3
(NREM) Sleep spindles become less common. Heart rate, metabolic rate, respiration rate and temperature all fall. This is heavier but still dreamless sleep. You are now unresponsive and hard to wake up. 15 minutes, 4-6% of total sleep. Theta into Delta brain waves
REM and NREM
Stage 4
(NREM) Metabolic rate is at its lowest, and the arousal threshold (i.e. how hard it is to wake someone up) is very high
This is very heavy sleep. Skeletal muscles are slowly ‘switched off’, meaning movement is difficult. If woken, the person is likely to be extremely groggy and confused. 30 minutes 12-15% total sleep . Delta brainwaves
REM and NREM
Stage 5
(REM) the deepest form of sleep
They are almost impossible to wake and their muscles are so relaxed they are essentially paralysed. 20-25% of total sleep. Brainwaves mimic those when awake
Strengths of biological process
• There is a lot of evidence to support the biological process explanation of the function of sleep and is therefore reliable.
• The methods used in studies that support the biological process are rigorous which makes the process more reliable.
• The biological process gives insight to way to help treat sleep disorders and has real world applications.
weaknesses of biological process
• The Biological process fails to take into account other explanations of sleep,, there is evidence in the cognitive process to support sleep aids learning and memory. Therefore the biological process is reductionist.
• Research to support the biological process is mainly lab experiments, this means the the process can’t be used to explain behaviour in a real world setting as it lack ecological validity
Key study
Dement and Kleitman (1957)
