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FEATURES OF SLEEP
A light-driven cycle helps to control body rhythms and sleep cycles. At night, the lack of light
stimulation triggers the pineal gland to release a hormone called melatonin. The pineal
gland is located in the centre of the brain, between the two hemispheres, and helps regulate
body rhythms and sleep cycles. Melatonin levels in the bloodstream respond to cycles of
light and dark by rising at dusk and peaking around midnight. This increased production of
melatonin makes us feel drowsy. The higher the melatonin level, the higher the level of
sleepiness. Melatonin levels then fall again as morning approaches.
PURPOSE OF SLEEP
There are two main theories in the study design on the purpose of sleep:
RESTORATIVE THEORY
The restorative theory suggests that sleep is vital for replenishing and revitalising the
physiological processes that keep the mind and body functioning at optimal level. NREM
sleep is essential for the restoration of the body, including repair of muscle and tissue
damage and muscle fatigue. REM sleep is essential for the restoration of mental processes,
allowing the brain time to regenerate and re-focus.
Evidence for this theory stems from research conducted into the amount of time that
individuals who partake in strenuous physical activity (such as marathon runners) spend in
NREM sleep. It has been found that after completing vast amounts of physical exercise the
amount of time spent in NREM sleep increases during that night’s sleep, and continues to
stay above average on subsequent nights following the activity.
However, one criticism of restorative theory is that people who are bedridden (and therefore
get no physical activity) still experience the same amount of NREM sleep as non-bedridden
individuals who undertake average amounts of activity.
It is thought that REM sleep may stimulate the developing brain early in life. Newborn babies
spend nine or ten hours a day – approximately 50 per cent of their total sleep time – in REM
sleep. In adulthood, REM sleep only occupies approximately 20 per cent of our sleep time.
The decrease in the amount of time spent in REM sleep also supports the restorative theory,
as it explains that as we age and are not learning so much new information, the need for
REM sleep also decreases. Further evidence to support this theory stems from research that
shows that during periods of high mental stress and emotional problems there is an increase
in the amount of REM sleep an individual experiences.
© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 1
THE SURVIVAL OR ADAPTIVE THEORY
The survival theory of sleep suggests that we undertake periods of inactivity, or sleep,
when we do not need to engage in activities that are important to our survival. The survival
theory takes into consideration the amount of time an animal needs to stay awake in order to
complete the activities required for their survival, such as hunting and eating. According to
this theory, the remaining hours of the day are best spent asleep, because sleep does not
expend much energy and also keeps the animal out of sight of predators.
For example, large, grazing animals such as elephants and cows need to consume a lot of
calories in order to obtain the energy they need to live. As the type of food (vegetation) they
eat contains few calories, they must consume a lot of it in order to meet their requirements.
This takes a lot of time, and this is why elephants only sleep for between three and four
hours a day – it is all they have time for! If elephants slept for eight hours a day, they
probably wouldn’t have enough wake time for all their necessary activities and requirements.
Smaller animals such as bats and possums do not need to consume very much food in order
to meet their calorific requirements, so they need few waking hours to eat and conduct other
activities necessary for survival. They spend approximately 20 out of 24 hours asleep. As
adult humans, we need approximately 16 waking hours to sustain our lifestyle. Therefore, we
spend an average of eight hours sleeping per day.
Some interesting facts about other species’ sleep patterns:
•
All mammals experience REM and NREM sleep. Birds do as well; however, their cycles
are shorter.
•
Small mammals sleep for 10 to 20 hours a day, whereas large mammals sleep for two
to 10 hours a day.
•
Brown bats are the champion sleepers, needing almost 20 hours a day, while giraffes
get by on only two hours a day.
•
Another facet to the adaptive theory is the proposal that sleeping actually protects
animals from attack. When an organism is asleep, it is not moving, and is therefore less
likely to attract the attention.
•
Hippopotamuses sleep under the water and then wake up to go to the surface to
breathe.
•
Dolphins keep one half of their brain awake so they are always only half asleep and
can keep on swimming while sleeping.
•
Horses lock their knees into the standing position so they don’t fall over while they
sleep.
•
Elephants and rhinoceroses cannot sleep lying on their sides for too long, as they
would drown from the fluid entering their lungs. This is due to the pressure of their
bulky bodies.
© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 2
QUESTION 16
Compare and contrast the two different theories of sleep.
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QUESTION 17
According to the survival theory of sleep:
A
B
C
D
We must sleep to conserve energy.
Sleep is unnecessary.
Sleep decreases our susceptibility to disease.
Sleep depends on the animal’s vulnerability to predators.
SLEEP DEPRIVATION
Sleep Deprivation refers to going without sleep.
One reason it is difficult to conduct experiments testing total sleep deprivation in humans is
their likelihood of lapsing into a brief snatch of sleep called a microsleep. A microsleep
involves a brief period of sleeping while seeming awake, where the EEG shows brainwave
patterns similar to the early stages of NREM sleep.
A number or studies on rats have shown they die without sleep after two or three weeks.
In humans, sleep deprivation for periods of time up to 11 days show there are no lasting long
term effects of prolonged sleep deprivation. All hours of lost sleep do not need to be caught
up. The most common reaction is that a person sleeps longer hours than usual for
two or three nights (i.e. Randy Gardner).
More serious but far rarer effects of sleep deprivation include:
•
Experiencing hallucinations (having false sensory experiences like seeing and hearing
things which don’t exist).
•
Experiencing delusions and paranoia (having false beliefs of a persistent nature).
•
Depression (i.e. Peter Tripp).
Common psychological effects of sleep deprivation include:
•
A decline in the ability to concentrate – especially on monotonous tasks.
•
Thinking can become illogical.
•
Difficulty making decisions.
•
Difficulty problem solving.
•
Feeling of irritability.
•
Heightened feeling of anxiety.
© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 3
Common physiological effects of sleep deprivation include:
•
Drooping eyelids.
•
Shaking hands.
•
Difficulty focusing eyes.
•
Feeling increased sensitivity to pain.
•
Slurred speech.
PSYCHOLOGICAL AND PHYSICAL EFFECTS
OF SLEEP DEPRIVATION
Psychological
Physical
Irritability
Shaking, particularly hands
Memory lapse
Drooping eyelids
Poor concentration on simple repetitive
tasks, better on difficult tasks
Difficulty focusing the eyes
Disorientation and confusion
Heightened pain sensitivity
Headaches
Heightened emotional responses
Reduced muscle strength
No permanent damage – recovery after good night’s sleep.
QUESTION 18
If you suffered sleep deprivation, what type of effect would occur first?
A
B
C
D
Hallucinations and delusions
Loss of ability to pay attention and perform simple routines
Both long-term and short-term memory loss
Coma
QUESTION 19
One psychological symptom of sleep deprivation includes:
A
B
C
D
Headaches
Drooping eyelids
Heightened pain sensitivity
Heightened emotional responses
© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 4
CHANGES IN SLEEP PATTERNS OVER THE LIFESPAN
Extracted from Grivas, Down, Letch and Carter (2010) page 150
The amount of time we spend sleeping decreases as we get older. In addition, the proportion
of total sleep time spent in REM sleep decreases markedly from infancy to adolescence, and
then remains relatively stable into adulthood and old age. The amount of NREM sleep time
also decreases, but compared to the drop in REM sleep up to adolescence, NREM sleep
tends to remain relatively stable. REM rebound is a phenomenon that occurs when we
spend significantly larger amounts of time in REM sleep following a period of being deprived
of REM sleep.
Adolescents need 9 hours and 15 minutes of sleep. Children need 10 hours and adults need
8 1/4 hours. They rarely get that much due to early school start time, inability to fall asleep
until late at night, work, social life and homework. Parents may need to adjust their child's
schedule to allow more sleep. Most teens are chronically sleep deprived and try to "catch
up" on their sleep by sleeping in on the weekends. Ultimately they should go to bed and
wake up at the same time.
QUESTION 20
Studies have shown that people deprived of REM sleep will experience ________________
periods of REM sleep on subsequent nights:
A
B
C
D
Shorter
Longer
No
Only
QUESTION 21
List down three key trends throughout the lifespan, ensuring that you refer to sleep onset;
REM episodes; NREM 1 and 2 episodes; awakenings.
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© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 5
ADOLESCENT SLEEP
In adolescents, there are characteristic changes in sleep patterns due to the rapid
physiological, emotional and social changes that take place. Ideally, teenagers need more
sleep, but do not get the required amount of sleep and therefore cope with sleep debt.
Biological ‘phase delay’ leads adolescents to experience a later shift of the sleep/wake cycle
due to changes to their internal body clock controlling circadian (24 hour) biological rhythms
that occur at puberty.
Adolescents are more susceptible to delayed sleep phase syndrome (DSPS), which involves
the inability to reset the sleep/wake cycle in response to environmental time cues. Possible
symptoms of DSPS include the inability to fall asleep until after midnight and the tendency to
wake up later than their desired time. Refer to Box 3.8 page 157 of textbook.
Biological influences on an adolescent’s sleep patterns and subsequent issues involve the
internal ‘biological clock’. Each day, our body goes through a cycle whereby hormones are
produced to control bodily functions. This is called the circadian rhythm and the sleep
hormone, melatonin, causes us to feel sleepy at night. There is a hormonally induced shift of
the body clock forward by about 1 – 2 hours during adolescence, resulting in the later onset
of sleepiness by 1 – 2 hours. This is known as the sleep-wake cycle shift and affects the
adolescent’s ability to fall asleep at the earlier times expected of them as a child. This shift in
onset of the sleep period also means there is a biologically driven need to sleep 1 – 2 hours
longer. However, the early start of school (or work) doesn’t allow for the adolescents to sleep
in and have the additional sleep needed. This nightly sleep loss can accumulate as sleep
debt. This sleep debt refers to sleep that is owed and needs to be made up. For example, a
nightly sleep debt of 90 minutes between Monday and Friday will lead to a total sleep debt of
seven and a half hours. Then, during the weekend, adolescents will often tend to sleep in to
compensate for the sleep loss during the week. However, on the weekend, adolescents may
go to bed at a later time still than on weekdays, which can temporary shift the sleep period
further forward so that by Monday morning, getting out of bed to go to school (or work) is
harder than on any other day of the week.
Problems that arise from insufficient sleep in adolescents may include:
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© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 6
QUESTION 22
Helen is 17 years old and has gone to a sleep clinic as she is having difficulty sleeping at
night. How much sleep would the staff at the clinic recommend Helen gets each night?
A
B
C
D
15 hours
12 hours
8 hours
4 hours
NEURONS: THE LEGO OF THE NERVOUS SYSTEM
As Area of Study 1 for Unit 3 Psychology involves studying the brain and the nervous
system it will be helpful for you to learn some basic information about neurons or nerve cells.
The term human nervous system refers to the entire system of neurons throughout the
human body.
THE BRAIN AND NERVOUS SYSTEM
The Human Nervous System


Central Nervous
System transmits
messages to the PNS
and receives them from
PNS.

Brain organises,
integrates,
initiates, and
interprets neural
messages.
Peripheral Nervous
System carries
messages to and from
the CNS.


Spinal Cord
connects brain
and the
peripheral
nervous system.

Cerebral
Cortex
Sympathetic
Nervous
System
activates
internal
muscles, organs
and glands
enabling body to
deal with
strenuous
activity or threat.
© The School For Excellence 2016
Autonomic
Nervous System
carries messages
from CNS to
modify or change
activity in
muscles, organs
and glands in
PNS.
Somatic Nervous
System carries
sensory messages
from PNS to CNS,
and controls
voluntary movement
of skeletal muscles
via messages sent
from CNS to PNS.
Parasympathetic
Nervous System
maintains a
balanced internal
body state, and
returns body to
calm state after
activation of the
sympathetic
nervous system
(homeostasis).
The Essentials – Unit 3 Psychology – Book 1
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Made up of the brain, spinal cord, and the nerves which connect to our muscles and organs,
the nervous system is our communication centre. The nervous system allows us to interact
with the external world and the world inside our bodies. It carries information to the brain
from our senses so the brain can interpret the incoming information and respond to it by
transmitting messages initiating action or movement in nerves in different parts of our
bodies. It is helpful to think of the vast and precisely organised network of neurons in the
human nervous system as a huge railway network linking places across a vast landscape we
call our own body.
The human nervous system involves thousands of millions of neurons each linking with up to
a thousand other neurons at connection points called synapses. A neuron is simply a
single nerve cell. Playing cricket, preparing a meal and eating it, watching television, writing
poetry or completing a complex essay all rely on neurons which are organised in precise
networks. Even a simple tap on the shoulder involves messages being passed through
sensory neurons in the shoulder to the spinal cord and onto the brain until they arrive in an
area of the brain associated with touch (the primary somatosensory cortex) which interprets
the message, and then sends further messages to a different area of the brain responsible
for initiating movement so you can turn around and look at the person to decide how to
respond to them.
Nerve impulses are responsible for the way information is transmitted from one neuron to
another throughout the nervous system in a rapid manner. Neurons are able to communicate
through bodily chemicals called neurotransmitters which are released at connection points
called synapses. When neurotransmitters cross the tiny gap (synaptic gap) they attach
themselves to receptor sites on the dendrites of the next neuron. If there are enough
neurotransmitters the neuron will fire an impulse and so on.
There are three main types of neurons (or nerve cells) in the human nervous system which
all have a similar structure.
•
Sensory (or afferent) neurons are specialist neurons that transfer messages away
from the sense organs in the PNS up the spinal cord to the brain in the CNS.
•
Interneurons transmit messages between sensory and motor neurons which don’t
make direct connections, and from one neuron to another within the CNS. The most
numerous neurons, they are only found within the CNS.
•
Motor (or efferent) neurons are specialist neurons which transfer messages away from
the CNS to the muscles, organs and glands in the PNS enabling bodily movement,
activation of internal organs and glandular secretions.
© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 8
Neurons may be specialised to perform particular functions. Motor neurons are specialised
to convey messages away from the brain to the body’s skeletal muscles to produce
movement. Sensory neurons are specialised to carry messages away from the sensory
receptors scattered throughout the body to the brain for processing.
REMEMBER — S A M E
Sensory (Afferent nerves) Arrive at CNS for processing.
Motor (Efferent nerves) Exit the CNS to initiate a response.
QUESTION 23
Neurons that are responsible for transmitting information from the PNS to the CNS are
known as:
A
B
C
D
Sensory or afferent neurons.
Sensory or efferent neurons.
Motor or afferent neurons.
Motor or efferent neuron.
QUESTION 24
Explain why it is misleading to state that “motor neurons take information from the motor
cortex in the CNS to the PNS”.
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© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 9
THE CEREBRAL CORTEX
Unfolded the cerebral cortex would approximate the area of a 63 cm TV screen. Its
convoluted and folded form enables more brain space. Valleys between folds are termed
sulci or fissures, and the high areas are called gyri (both terms are plural).
The cerebral cortex has a range of functions. It enables our higher-order information
processing functions like learning, using language, thinking, problem-solving, memory,
decision-making, recognising and planning. However, it can’t act alone. It communicates
with other areas of the brain and body through neurons – the basic building blocks of the
entire human nervous system. About three millimetres thick, the cerebral cortex contains
about three-quarters of nerve cells or neurons in the brain.
The cerebral cortex is divided into two halves or hemispheres which are separated by a
deep grove termed the longitudinal fissure running from front to back. Both hemispheres are
alike in their shape and structure. The main connecting structure is a bundle of nerve tissue,
10 centimetres in length, called the corpus callosum. The corpus callosum allows both
hemispheres to share information and coordinate their functions. This means both
hemispheres are involved in most functions, even simple ones.
The cerebral hemispheres are contralaterally organised, meaning the left hemisphere
receives sensory information from the right side of the body and controls movement on the
right side; while the right hemisphere receives sensory information from the left side of the
body and controls movement on the left side.
The cerebral cortex covering each hemisphere can be divided into four regions called
cortical (from cortex) lobes. Each lobe has a different primary function.
In addition to the primary function each lobe has its own association areas which make up
the remaining 75% of the cerebral cortex. The association areas integrate diverse
information between lobes, and sensory and motor information from other areas of the brain
(allowing them to associate with each other). They are involved in more complex higherorder mental or cognitive process such as thinking, planning, making decisions and
perceiving so we can act purposefully. Interaction between lobes is necessary for even
simple behaviours.
© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 10
THE LOBES OF THE CEREBRAL CORTEX
FRONTAL LOBES
The frontal lobes contain the primary motor cortex which initiates specific voluntary body
movements of skeletal muscles.
Frontal lobe association areas:
•
Play an executive role in thinking, feeling and behaviour because it is an end point for
much of the sensory information received and processed in the other lobes.
•
Coordinate functions of other lobes to determine behavioural responses.
•
Are important in the processes of planning and thinking.
•
Are associated with expression of personality. Refer to case study of Phineas Gage
who didn’t seem to be the same person to his wife and friends after an accident
damaging his frontal lobes caused a dramatic change of personality.
•
Are involved with control and expression of emotion.
The frontal lobe in the left hemisphere contains Broca’s area which is involved in the
production of clear and fluent speech. Damage to the Broca’s area causes Broca’s
aphasia.
Damage to the frontal lobes association areas can cause impairment to mental abilities such
as judging, planning and using initiative.
Extra Notes:
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© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 11
PARIETAL LOBES
The parietal lobes contain the primary somatosensory cortex which receives analyses and
interprets information on touch, temperature, pressure, and muscle movement and position
of limbs from sensory receptors in the muscles, tendons and joints.
Parietal lobe association areas:
•
Integrate information about the body’s position in space.
•
Are associated with paying visual attention.
•
Are involved in spatial reasoning to determine where an object is located in space.
Damage to the right parietal lobe (only) can cause Spatial Neglect where a patient does
not attend to the left side of their visual field.
Extra Notes:
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© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 12
OCCIPITAL LOBES
The occipital lobes contain the primary visual cortex which receives analyses and interprets
visual information from sensory receptors in the eyes.
Occipital lobe association areas:
Interact with other lobes to integrate visual information with information from memory,
language and sounds so we can interpret a visual stimulus.
The occipital lobes also contain the visual association areas which integrate information
from other areas of the cerebral cortex – allowing us to form visual perceptions, to think
visually and to remember visual images. Oliver Sacks described a patient with damage to
the association areas of the occipital lobes. The man could identify a rose by smell (not
sight) even though he could see and describe the basic features of it (its colour shape,
contour, etc.). However, he could not integrate the information with other information in the
visual and olfactory parts of his memory.
The neural pathway of visual information is an area of this study that is very easily
confused. Take time to study it carefully, in particular the diagram and information on p79.
Each eye receives information from two visual fields – left and right. Information received in
the right visual field will be seen in both eyes, but transmission is divided. The left half of
each eye receives information from the right half of the visual field, sends information only
to the visual cortex in the left side of the brain. The right half of each eye, receives
information from the left half of the visual field, sends information only to the visual cortex in
the right side of the brain.
So information flashed to the left visual field will be seen in both eyes, on the right side, and
will be sent to the right hemisphere. Information flashed to the right visual field will be seen in
both eyes, on the left side, and will be sent to the left hemisphere.
Extra Notes:
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© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 13
TEMPORAL LOBES
The temporal lobes contain the primary auditory cortex which receives analyses and
interprets auditory information or sound from sensory receptors in the ears.
Temporal lobe association areas:
•
Are involved in determining the appropriate emotional response to sensory information.
•
Help with the memory of facts.
•
Are involved with memory of how to do things (procedural memory).
•
Associated with memory for faces or facial recognition.
•
Are associated with memory of personal experiences like birthdays, holidays, accidents
etc. (Episodic memory.)
•
Helps with memory for identification objects so we can determine what an object is.
The temporal lobe in the left hemisphere contains Wernicke’s area which is involved in
interpreting and understanding sounds. Damage to the Wernicke’s area causes Wernicke’s
aphasia which results in speech that is garbled but fluent.
People with partial or total memory loss often have damage to the temporal lobes.
Extra Notes:
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© The School For Excellence 2016
The Essentials – Unit 3 Psychology – Book 1
Page 14