Higher Human Biology Unit 3 Behaviour Populations and

Higher Human Biology Unit 3: Behaviour, Populations and environment Chapter 25: The Brain 10/31/2020 Mrs Smith Ch 25 The Brain 1

Learning Intentions Success Criteria To examine the workings of the brain and the nervous system. 10/31/2020 1. Outline the structure of the human brain with reference to; a. Size b. The cerebrum and its convoluted surface c. Localisation of function in discrete areas of the cerebrum d. The relationship between size of a discrete are and the function carried out e. The importance of the corpus callosum in transferring information between two hemispheres Mrs Smith Ch 25 The Brain 2

The brain is a very complex organ not fully understood by scientists VARIABLES 10/31/2020 Mrs Smith Ch 25 The Brain 3

FYI: The Brain • Weighs 1300 - 1400 g • Made up of about 100 billion neurons. • “The most complex living structure on the universe” Society for Neuroscience • Makes us who we are. 10/31/2020 Mrs Smith Ch 25 The Brain 4

“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 17 th 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, 10/31/2020 Mrs Smith Ch 25 The Brain these experiences 5

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 10/31/2020 Mrs Smith Ch 25 The Brain body size. 6

Why is it appropriate to say the weight of the brain determines intelligence? Animal Wt. of 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. 10/31/2020 Mrs Smith Ch 25 The Brain 7

Evolution of the Brain: Fossil evidence 10/31/2020 Mrs Smith Ch 25 The Brain 8

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. 10/31/2020 Mrs Smith Ch 25 The Brain 9

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 10/31/2020 Mrs Smith Ch 25 The Brain 10 to teach an ape to speak.

Ape Brains Compared to the brain of modern apes the human brain is about 3 times larger. Image source: http: //www. nature. com 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. 10/31/2020. Mrs Smith Ch 25 The Brain 11

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 10/31/2020 Mrs Smith Ch 25 The Brain 12

Brain Structure: ~ Revision 10/31/2020 Mrs Smith Ch 25 The Brain 13

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Cerebrum Structure • Controls conscientious thought, voluntary actions, determines personality etc 10/31/2020 Mrs Smith Ch 25 The Brain 15

The Cerebrum: localisation of function The cerebral hemisphere has several distinct regions each with a particular function. 10/31/2020 Mrs Smith Ch 25 The Brain 16

• Largest part of human brain • Split into 2 halves called cerebral hemispheres Cerebrum: Con’t 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. 10/31/2020 Mrs Smith Ch 25 The Brain 17

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Each side of the brain controls the other side of the body 10/31/2020 Mrs Smith Ch 25 The Brain 19

Cerebrum: Grey and white matter • inner cerebrum • made of nerve cell fibres • surface of cerebrum • made of nerve cell bodies 10/31/2020 Mrs Smith Ch 25 The Brain 20

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Cerebrum: Convolution • The cerebrum’s surface is convoluted (folded) to give it a large surface area allowing many cell bodies to be close together. Cerebrum • This maximises the potential for interconnections and the transmission of messages. 10/31/2020 Mrs Smith Ch 25 The Brain 22

Task: Torrance-TYK pg 206 Qu 1 -4 10/31/2020 Mrs Smith Ch 25 The Brain 23

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. hw. ac. uk/vle/sch olar/session. controller? action=view. Co ntent&content. GUID=2 ba 96 ae 7 -1 effe 695 -8 b 5 d-5 f 08 e 2 cc 8533 10/31/2020 Mrs Smith Ch 25 The Brain 24

Roles of the 3 discrete functional areas Association areas Sensory areas Receive info as Analyse & Interpret sensory impulses from body’s e. g. Make decisions receptors e. g. touch receptors in skin and thermoreceptors in hypothalamus 10/31/2020 Motor areas Receive info from association areas & send motor impulses to the effectors e. g. muscles Mrs Smith Ch 25 The Brain 25

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Association areas Premotor association area Somatosensory association area 10/31/2020 Auditory association area Mrs Smith Ch 25 The Brain Visual association area 27

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. 10/31/2020 Mrs Smith Ch 25 The Brain 28

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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 Association area This allows the human brain to cope with several sensory impulses at once (sophisticated perception) e. g. channel flicking 10/31/2020 Motor area They then cause more exchange of impulses between cerebral areas allowing a sophisticated response e. g. singing & dancing Mrs Smith Ch 25 The Brain 30

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 10/31/2020 Mrs Smith Ch 25 The Brain nerve endings in the body part 31

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 10/31/2020 Mrs Smith Ch 25 The Brain 32 its movement.

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. 10/31/2020 Mrs Smith Ch 25 The Brain 33

Who is Homunculus? • Imaginary human whose body parts have been drawn in proportion to – Mobility and fine motor control – Sensory perception 10/31/2020 • The more control needed of a task, the larger the area of the 34 Mrs Smith Ch 25 The Brain brain that is required

MOTOR HOMUNCULUS The motor area of the left cerebral hemisphere Motor homunculus—larger parts of the brain control larger parts of the body such as the hand 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. View the Scholar animation: http: //courses. scholar. hw. ac. uk/vle/scholar/session. con troller? action=view. Content&content. GUID=8 af 4 bea 210/31/2020 600 b-deeb-baec-d 7517 d 578 e 46 "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. " Mrs Smith Ch 25 The Brain 35

SENSORY HOMUNCULUS The sensory area of the left cerebral hemisphere Sensory homunculus—Similar to motor homunculus but it tells the brain how much power is needed for sensory perception of different body parts. 10/31/2020 "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. " Mrs Smith Ch 25 The Brain 36

Cerebellum • Attached to underside of brain • Unconscious fine control of voluntary muscle movement and balance 10/31/2020 Mrs Smith Ch 25 The Brain 37

Medulla Oblongata • Connects brain to spinal cord • Unconscious coordination of basic functions – breathing, heart rate, digestion, reflex actions Medulla oblongata 10/31/2020 Mrs Smith Ch 25 The Brain 38

Studying the Brain • The evidence that there is localisation of brain functions (i. e. that different parts of the brain have different functions) include: A. Electroencephalograms (EEG’s) B. Brain Scans • • 10/31/2020 Cat Scan f. MRI Scan Mrs Smith Ch 25 The Brain 39

Brain Scans Speech involves several specific regions of the brain. These show up in brain scans as areas of high metabolic activity. FYI: You DON’T need to know the names of these areas!! View the Scholar animation: 10/31/2020 Mrs Smith Ch 25 The Brain http: //courses. scholar. hw. ac. uk/vle/scholar/session. controller? action=view. Content&content. GUID=c 622 c 31 f-213 c-2853 -d 6 e 0 -e 311 a 44 d 055 f 40

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Studying the Brain- EEG Electroencephalograms A record of the cerebrum’s 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. 10/31/2020 Mrs Smith Ch 25 The Brain 42

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 Infants, problem (e. g. dense Sleeping spikes are shown adults during epileptic attacks), but the EEG doesn’t show the area of the brain responsible. 10/31/2020 Mrs Smith Ch 25 The Brain 43 Epilepsy

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 This brain scan shows a tumour in pale blue. for certain actions and 10/31/2020 Mrs Smith Ch 25 The Brain 44 emotions. Image source: www. sciencemuseum. org. uk/on

Studying the Brain: Brain Scans f. MRI 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 f. MRI (functional magnetic resonance imaging) brain scans obtained during a visual memory task. 10/31/2020 Mrs Smith Ch 25 The Brain 45

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. 10/31/2020 Mrs Smith Ch 25 The Brain 46

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. 10/31/2020 Mrs Smith Ch 25 The Brain 47

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. 10/31/2020 Mrs Smith Ch 25 The Brain 48

Split-brain studies • Split brain happens when a person’s corpus callosum has been cut. • Because of this exchange of information between cerebral hemispheres doesn’t occur. • Learn more. . . • http: //www. nobelprize. org/educational/medicine/splitbrain/background. html • Play the split brain game. . . . • http: //www. nobelprize. org/educational/medicine/split 10/31/2020 Mrs Smith Ch 25 The Brain brain/index. html 49

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 10/31/2020 Mrs Smith Ch 25 The Brain 50

Normal Visual Pathway Information passed across corpus callosum 10/31/2020 Mrs Smith Ch 25 The Brain 51

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 View the Scholar animation: information from the left eye http: //courses. scholar. hw. ac. uk/vle/scholar/session. controller? action=v iew. Content&content. GUID=a 3 d 7028 a-e 33 c-5447 -e 177 -1457682 f 9206 & vice versa. 10/31/2020 Mrs Smith Ch 25 The Brain 52

Abnormal Visual Pathway 10/31/2020 Mrs Smith Ch 25 The Brain 53

If a person with a split-brain (severed corpus callosum) is…. a) 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 10/31/2020 Mrs Smith Ch 25 The Brain the left hemisphere. 54

Watch this!!!! http: //www. youtube. com/watch? v=ZMLz. P 1 VCANo 10/31/2020 Mrs Smith Ch 25 The Brain 55

• See Scholar – Split Brain Studies http: //courses. scholar. hw. ac. uk/vle/scholar /session. controller? action=view. Content&c ontent. GUID=a 3 d 7028 a-e 33 c-5447 -e 1771457682 f 9206 10/31/2020 Mrs Smith Ch 25 The Brain 56

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 to: http: //serendip. brynmawr. edu/bb/blindspot 1. html 10/31/2020 Mrs Smith Ch 25 The Brain 57

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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. • LET’S PROVE IT!!! 10/31/2020 Mrs Smith Ch 25 The Brain 59

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 10/31/2020 Mrs Smith Ch 25 The Brain 60 all about that particular part of the picture.

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 10/31/2020 Mrs Smith Ch 25 The Brain 61 about the way the brain works.

Damaged frontal lobe 10/31/2020 • 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 illtempered, unreliable and could no longer stick to a plan. • This is because our FRONTAL LOBES are required in planning, goal setting and personality. Mrs Smith Ch 25 The Brain 62

Wife or Hat? 10/31/2020 • 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 wife’s head and tried to lift it to put it on, thinking it was a hat. • HE HAD A PROBLEM WITH HIS Mrs Smith Ch 25 The Brain 63 VISUAL ASSOCIATION CENTERS

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. 10/31/2020 Mrs Smith Ch 25 The Brain 64

The cost of war: Washington Post 04/10/2010 • • • 10/31/2020 http: //voices. washingtonpost. com/blogpost/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 Mrs Smith Ch 25 The Brain 65

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. 10/31/2020 Mrs Smith Ch 25 The Brain 66

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. 10/31/2020 Mrs Smith Ch 25 The Brain 67

Task: Torrance-TYK pg 211 Qu’s 1 -4 10/31/2020 Mrs Smith Ch 25 The Brain 68

Task: Torrance AYK pg 211/212 Qu’s 1 -6 10/31/2020 Mrs Smith Ch 25 The Brain 69

Task: Can you answer these? 10/31/2020 Mrs Smith Ch 25 The Brain 70

Task: Can you answer these? 10/31/2020 Mrs Smith Ch 25 The Brain 71

More Questions 10/31/2020 Mrs Smith Ch 25 The Brain 72

Answers 10/31/2020 Mrs Smith Ch 25 The Brain 73

Even more Questions 10/31/2020 Mrs Smith Ch 25 The Brain 74

Answers 10/31/2020 Mrs Smith Ch 25 The Brain 75

And Again!! 10/31/2020 Mrs Smith Ch 25 The Brain 76

Answer Again!! 10/31/2020 Mrs Smith Ch 25 The Brain 77

Essay style Questions Scholar Describe the appearance of the human brain, commenting on localised structures and their functions (10) 10/31/2020 Mrs Smith Ch 25 The Brain 78

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') 10/31/2020 Mrs Smith Ch 25 The Brain One mark is deducted if a detailed explanation of negative feedback control is given. 79