Unit 3: Behaviour, Populations and environment

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Unit 3 Behaviour, Populations and environment
Higher Human Biology

• Chapter 25 The Brain

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• Learning Intentions

• Success Criteria

• To examine the workings of the brain and the
  nervous system.

• Outline the structure of the human brain with
  reference to
• Size
• The cerebrum and its convoluted surface
• Localisation of function in discrete areas of the
  cerebrum
• The relationship between size of a discrete are
  and the function carried out
• The importance of the corpus callosum in
  transferring information between two hemispheres

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Variables

• The brain is a very complex organ not fully
  understood by scientists

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FYI The Brain

• Weighs 1300 - 1400g
• Made up of about 100 billion neurons.
• The most complex living structure on the
  universe Society for Neuroscience
• Makes us who we are.

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• We are like chameleons, we take our hue and the
  colour of our moral character, from those who are
  around us.

No man's knowledge here can go beyond his
experience.

• John Locke was an influential philosopher from
  the 17th century. He has provided many important
  ideas and bases on philosophy, one of which was
  his theory of personal identity. Locke believed
  all true knowledge came from the senses and human
  experience.
• Basically each of us are a combinations of all
  the experiences we ever had and how we perceive
  these experiences. This can only happen with a
  brain to perceive, process, store, these
  experiences

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The brain size of the brain

• The brain is a large organ composed of billions
  of nerve cells (neurones).
• Compared with other animals, the human brain is
  disproportionally large, relative to body size.

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Why is it appropriate to say the weight of the
brain determines intelligence?

• Animal Wt. of Brain Brain/Body wt ratio
• Whale 15 lbs 1/10000
• Elephant 3 lbs 1/1000
• Human 3 lbs 1/50
• The human brain is more developed and has a
  larger weight in proportion to total body weight.

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Evolution of the Brain Fossil evidence
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Increase in Brain Size
Fossil evidence has shown that the human brain
has increased in capacity (volume of skull
occupied by the brain) over a fairly rapid
evolutionary timescale.
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Apes

• When compared with the brains of modern apes, the
  human is found to be approximately three times
  larger.
• Humans have much larger centres responsible for
  higher mental faculties such as intelligence,
  speech, hearing and sight.
• An apes area controlling speech is so small and
  poorly developed it is impossible to teach an ape
  to speak.

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Ape Brains
Compared to the brain of modern apes the human
brain is about 3 times larger.
Humans have much larger centres responsible for
higher mental faculties such as intelligence,
speech, hearing and sight. An apes area
controlling speech is so small and poorly
developed it is impossible to teach an ape to
speak. .
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Dominant Species

• Compared to other animals humans are physically
  weak.
• However humans have become a dominant species on
  earth because the human brain has
• a larger size
• complex internal development
• complex organisation

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Brain Structure Revision
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Cerebrum Structure

• Controls conscientious thought, voluntary
  actions, determines personality etc

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The Cerebrum localisation of function
The cerebral hemisphere has several distinct
regions each with a particular function.
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Cerebrum Cont

• Largest part of human brain
• Split into 2 halves called cerebral hemispheres

• 2 sides of the brain are joined by the corpus
  callosum - a large bundle of nerve fibres. This
  allows information to be transferred from one
  side to the other.

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Each side of the brain controls the other side
of the body
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Cerebrum Grey and white matter

• inner cerebrum
• made of nerve cell fibres

• surface of cerebrum
• made of nerve cell bodies

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Cerebrum Convolution

• The cerebrums surface is convoluted (folded) to
  give it a large surface area allowing many cell
  bodies to be close together.
• This maximises the potential for interconnections
  and the transmission of messages.

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Task Torrance-TYK pg 206 Qu 1-4
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Discrete Functional Areas
The cerebrum has 3 main types of functional area,
which are all discrete (they have their own
function)

• Sensory
• Association
• Motor

View the Scholar animation http//courses.scholar
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Roles of the 3 discrete functional areas
Association areas Analyse Interpret sensory
impulses e.g. Make decisions
Motor areas Receive info from association areas
send motor impulses to the effectors e.g. muscles
Sensory areas Receive info as sensory impulses
from bodys receptors e.g. touch receptors in
skin and thermoreceptors in hypothalamus
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Association areas
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Speech

• Each region of the left cerebral hemisphere is
  duplicated on the right cerebral hemisphere
  except speech.

Each person only has one speech area. In 90 of
people this is in the left cerebral hemisphere.
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Interconnections in the Brain
Tiny nerve fibres interconnect the different
areas of the brain. Messages constantly pass
between them.
Sensory area
This allows the human brain to cope with several
sensory impulses at once (sophisticated
perception)
They then cause more exchange of impulses between
cerebral areas allowing a sophisticated response
e.g. channel flicking
e.g. singing dancing
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Motor Area

• The motor area is one of the largest regions of
  each cerebral hemisphere.
• Each motor area consists of motor neurons which
  sends out impulses to bring about voluntary
  movement of skeletal muscles
• However, the size of the part of the motor area
  is not in proportion to the actual size of the
  body part.
• The size of the motor area is in proportion to
  the number of nerve endings in the body part

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Discovery of the motor area
In 1870, Hitzig and Fritsch electrically
stimulated parts of a dog's motor cortex.
Depending on what part of the cortex they
stimulated, a different part of the body
contracted. When they destroyed this same small
area of the cortex, the corresponding part of the
body became paralysed.
They concluded that every part of the body has a
particular region of the primary motor cortex
that controls its movement.
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Motor or sensory area allocated to a particular
body part is found to be in relative proportion
to its mobility/sensory. e.g. the more mobile a
part the larger the motor area.
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Who is Homunculus?

• Imaginary human whose body parts have been drawn
  in proportion to
• Mobility and fine motor control
• Sensory perception
• The more control needed of a task, the larger the
  area of the brain that is required

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Motor homunculus

• The motor area of the left cerebral hemisphere

Motor homunculuslarger parts of the brain
control larger parts of the body such as the hand
and mouth, which require a lot of motor or
motion signals. That is, if the human body
were to be built in proportion to its motor
significance because of the brain power needed to
motor them, the hands and mouth would be
proportionally bigger.
"This model shows what a man's body would look
like if each part grew in proportion to the area
of the cortex of the brain concerned with its
movement."
View the Scholar animation http//courses.scholar
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Sensory homunculus

• The sensory area of the left cerebral hemisphere

Sensory homunculusSimilar to motor homunculus
but it tells the brain how much power is needed
for sensory perception of different body parts.
"This model shows what a man's body would look
like if each part grew in proportion to the area
of the cortex of the brain concerned with its
movement."
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Cerebellum

• Attached to underside of brain
• Unconscious fine control of voluntary muscle
  movement and balance

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Medulla Oblongata

• Connects brain to spinal cord
• Unconscious co-ordination of basic functions
  breathing, heart rate, digestion, reflex actions

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Studying the Brain

• The evidence that there is localisation of brain
  functions (i.e. that different parts of the brain
  have different functions) include
• Electroencephalograms (EEGs)
• B. Brain Scans
• Cat Scan
• fMRI Scan

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Brain Scans
Speech involves several specific regions of the
brain. These show up in brain scans as areas
of high metabolic activity.
FYI You DONT need to know the names of these
areas!!
View the Scholar animation http//courses.schola
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Studying the Brain- EEG
Electroencephalograms
A record of the cerebrums electrical activity.
Electrodes are placed on the different regions of
the scalp. They detect impulses which are
displayed on a monitor. Different brain wave
patterns show different levels of mental
activity.
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EEG wave patterns
The more densely packed the spikes, the higher
the level of electrical activity in the brain.
EEGs are not very precise because they reflect
the activity of many brain cells.
Children, Sleeping adults
EEGs can show abnormal patterns that indicate a
problem (e.g. dense spikes are shown during
epileptic attacks), but the EEG doesnt show the
area of the brain responsible.
Infants, Sleeping adults
Epilepsy
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Studying the Brain Brain Scans CAT SCANS

• Often referred to as CAT (Computer Assisted
  Tomography) scans.
• These give a clear image of the brain without any
  surgery
• used mainly to diagnose abnormalities
• Can indicate areas of high metabolic activity
  so can be used to determine which part of the
  brain is responsible for certain actions and
  emotions.

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Studying the Brain Brain Scans fMRI SCANS

• Brain scans provide pictures of very active parts
  of the brain
• The parts of the brain which are active show up
  as brightly coloured areas
• The following diagrams show four fMRI (functional
  magnetic resonance imaging) brain scans obtained
  during a visual memory task.

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Scan 1

• In scan 1, a subject is asked to remember a face.
  Areas at the rear of the brain that process
  visual information are active during this task,
  as is an area in the frontal lobe.

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Scan 2

• In scan 2, the subject is asked to "think about
  this face." The hippocampus is activated. The
  hippocampus was already known to be important for
  memory, but these results show that this part of
  the brain is specifically active during the time
  when we are remembering new information.

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Scans 3 and 4

• In scans 3 and 4, the subject was asked to
  compare another face to the remembered face. Some
  of the same visual areas are activated as during
  the initial memory task, but other areas, such as
  part of the frontal lobe, are involved in making
  a decision about the memory.

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Split-brain studies

• Split brain happens when a persons corpus
  callosum has been cut.
• Because of this exchange of information between
  cerebral hemispheres doesnt occur.
• Learn more.............
• http//www.nobelprize.org/educational/medicine/spl
  it-brain/background.html
• Play the split brain game.................
• http//www.nobelprize.org/educational/medicine/spl
  it-brain/index.html

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Split Brain Studies Visual Pathways Normal
situation

• Each cerebral hemisphere only receives half the
  information of the visual field.
• Everything to the left Is represented by the
  right cerebral hemisphere
• Everything to the right is represented by the
  left cerebral hemisphere.

When the corpus callosum is intact both
hemispheres perceive all information from both
eyes as each hemisphere quickly communicates so
the whole picture is in view
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Split Brain Studies Visual Pathways Abnormal
situation

• If the corpus callosum is cut (e.g. during
  surgery required due to intractable epilepsy),
  exchange of information is prevented because the
  corpus callosum does not connect the 2 cerebral
  hemispheres.
• So each hemisphere only perceives half of the
  information. The right hemisphere only gets
  information from the left eye vice versa.

View the Scholar animation http//courses.schola
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• If a person with a split-brain (severed corpus
  callosum) is.
• shown an object with their right eye open and
  left eye closed, they will be able to say the
  name of the object
• b) shown an object with their left eye open and
  right eye closed they will be able to use the
  object (e.g. a spoon), write the name of the
  object, but NOT say the word!

Because the speech area is only found in the left
hemisphere.
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Watch this!!!! http//www.youtube.com/watch?vZML
zP1VCANo
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• See Scholar Split Brain Studies
• http//courses.scholar.hw.ac.uk/vle/scholar/sessi
  on.controller?actionviewContentcontentGUIDa3d70
  28a-e33c-5447-e177-1457682f9206

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Blind Spot

• Because each eye has an optic nerve at the back,
  there is an area of the retina which has no light
  sensitive neurones. This area is called the blind
  spot.
• To find out about your blind spot, go
  tohttp//serendip.brynmawr.edu/bb/blindspot1.htm
  l

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Task

• Look around. Do you see a blind spot anywhere?
  Maybe the blind spot for one eye is at a
  different place than the blind spot for the other
  (this is actually true), so you don't notice it
  because each eye sees what the other doesn't.
  Close one eye and look around again. Now do you
  see a blind spot? Hmm. Maybe its just a little
  TINY blind spot, so small that you (and your
  brain) just ignore it. Nope, its actually a
  pretty BIG blind spot.
• LETS PROVE IT!!!

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Try this!!

• Close your left eye and stare at the cross mark
  in the diagram with your right eye. Off to the
  right you should be able to see the spot. Don't
  LOOK at it just notice that it is there off to
  the right (if its not, move farther away from the
  computer screen you should be able to see the
  dot if you're a couple of feet away). Now slowly
  move toward the computer screen. Keep looking at
  the cross mark while you move. At a particular
  distance (probably a foot or so), the spot will
  disappear (it will reappear again if you move
  even closer). The spot disappears because it
  falls on the optic nerve head, the hole in the
  photoreceptor sheet.
• So, as you can see, you have a pretty big blind
  spot, at least as big as the spot in the diagram.
  What's particularly interesting though is that
  you don't SEE it. When the spot disappears you
  still don't SEE a hole. What you see instead is a
  continuous white field (remember not to LOOK at
  it if you do you'll see the spot instead). What
  you see is something the brain is making up,
  since the eye isn't actually telling the brain
  anything at all about that particular part of the
  picture.

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Brain Injury Studies
Brain damage is usually caused by Tumours,
disease or accidents

• Studies for brain injuries include
• Phineas Gage frontal lobe determines
  personality.
• A man with visual agnosia mistook his wife for a
  hat.
• Soldiers with shrapnel wounds
• People with brain lesions
• Stroke sufferers

Studying this damage has allowed experts to learn
more about the way the brain works.
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Damaged frontal lobe

• In 1848 an accident happened to a railroad
  worker.
• A rod entered beneath his left eye and through
  the top of his head.
• He survived and eventually returned to work......
  BUT....
• He changed personality becoming ill-tempered,
  unreliable and could no longer stick to a plan.
• This is because our FRONTAL LOBES are required in
  planning, goal setting and personality.

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Wife or Hat?

• A musician of great ability developed a problem
  in later life.
• He no longer recognised people or objects and
  failed to remember the past visually.
• He would chat to furniture thinking it was a
  person.
• On one occasion he reached out, took hold of his
  wifes head and tried to lift it to put it on,
  thinking it was a hat.
• HE HAD A PROBLEM WITH HIS VISUAL ASSOCIATION
  CENTERS

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Shrapnel wounds

• Experts studied soldiers blinded or paralysed be
  cause of shrapnel.
• There findings provided early evidence that the
  rear of the cerebrum is responsible for vision
  and the area we call the MOTOR AREA controls
  movement.

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The cost of war Washington Post 04/10/2010

• http//voices.washingtonpost.com/blog-post/2010/10
  /traumatic_brain_injuries_18000.html
• Robert Warren, three weeks after leaving
  Afghanistan, could not remember the name of the
  country he was just in. Shrapnel tore into his
  skull and a chunk of it had to be removed. "That
  country," he called Afghanistan, unable to grasp
  the right word.
• A piece of shrapnel pierced John Barnes's brain,
  tearing through his frontal lobe, the region in
  charge of decision making, reason and morality.
  As a result, Barnes exhibits impulsive behaviour
  and is unable to live on his own

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Lesions

• Lesions are small regions of damage.
• The location of the brains language centres is
  verified by the fact that lesions in these areas
  give rise to speech defects.

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Strokes

• Stroke suffers often loose the function of part
  of their brain (sometimes permanent) , by
  matching the area of the brain affected to the
  lost bodily function experts can identify which
  parts of the brain are responsible for which
  bodily functions.

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Task Torrance-TYK pg 211 Qus 1-4
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Task Torrance AYK pg211/212 Qus 1-6
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Task Can you answer these?
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Task Can you answer these?
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More Questions
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Answers
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Even more Questions
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Answers
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And Again!!
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Answer Again!!
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Essay style Questions Scholar

• Describe the appearance of the human brain,
  commenting on localised structures and their
  functions (10)

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ANSWER Describe the appearance of the human
brain, commenting on localised structures and
their functions (10)

• Each numbered point is worth 1 mark. The
  information in brackets is not a required part
• Correct facts (8 marks)
• The brain consists of a central core, including
  medulla and cerebellum.
• The medulla controls unconscious activities such
  as peristalsis and rates of breathing and
  heartbeat.
• The limbic system, including the hippocampus, is
  found in above the medulla.
• The outer layer of the brain is called the
  cerebrum or cerebral hemispheres.
• Conscious activities are co-ordinated by the
  cerebrum.
• The outer surface of the cerebrum (cortex) is
  folded to increase the numbers of connections
  possible between neurones.
• A visible cleft in the cerebrum is the location
  of the somatosensory area.
• Sensory messages are received in the latter part
  of the cleft and motor responses are sent out by
  the frontal part.
• The areas allocated are directly proportional to
  the degree of sensation and control required.
• Large areas are devoted to the lips and hands,
  particularly the fingers.
• The right side of the brain controls the left
  side of the body and vice versa.
• The corpus callosum is a massive bundle of nerves
  that transfers information across the cerebral
  hemispheres.
• Coherence (1 mark) One mark is given if at least
  5 relevant points provided.
• Relevance (1 mark) It causes glycogen to be
  (rapidly) converted to glucose (not 'converts')
• One mark is deducted if a detailed explanation of
  negative feedback control is given.

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Humour Toddler brain
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Humour Teenage brain
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Humour Adult brain
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Humour Canine brain
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Humour Feline brain