1. THE HUMAN BRAIN
AHL Option E.5
IB Biology
Miss Werba

2. OPTION E - NEUROBIOLOGY
STIMULUS and RESPONSE
E.2
PERCEPTION of STIMULI
E.3
INNATE and LEARNED BEHAVIOUR
E.4
NTs and SYNAPSES
E.5
THE HUMAN BRAIN
E.6 FURTHER STUDIES IN BEHAVIOUR
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3. THINGS TO COVER Structure of the human brain
Function of brain structures
Use of animal experiments, lesions & FMRI scanning to identify brain regions involved in specific functions
Sympathetic & parasympathetic control of heart rate, iris movement & blood flow to the gut
Pupil reflex
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4. THE HUMAN BRAIN Command term = LABEL
cerebral hemisphere
cerebellum
brainstem
outer view
cross-section
spinal cord
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5. THE HUMAN BRAIN: STRUCTURE Command term = LABEL
CEREBRAL HEMISPHERE
HYPOTHALAMUS
PITUITARY GLAND
CEREBELLUM
MEDULLA OBLONGATA
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6. THE HUMAN BRAIN: FUNCTION Command term = OUTLINE
CEREBRAL HEMISPHERE
Complex thought
Learning
Memory
Problem solving
Emotions
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7. THE HUMAN BRAIN: FUNCTION Command term = OUTLINE
HYPOTHALAMUS
Maintains homeostasis via coordination of the nervous and endocrine systems
Regulates secretion of pituitary hormones
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8. THE HUMAN BRAIN: FUNCTION Command term = OUTLINE
PITUITARY GLAND
Produces and secretes hormones regulating many body functions
eg. ADH (for osmoregulation)
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9. THE HUMAN BRAIN: FUNCTION Command term = OUTLINE
MEDULLA OBLONGATA
Controls automatic and homeostatic activities
eg. swallowing, digestion, vomiting, breathing rate, heart rate
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10. THE HUMAN BRAIN: FUNCTION Command term = OUTLINE
CEREBELLUM
Coordinates muscle movement and balance
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11. IDENTIFYING BRAIN FUNCTIONS Command term = EXPLAIN
How can fMRI (functional magnetic resonance imaging) be used in the identification of the brain part involved in specific functions?
‘Brain mapping’ experiments are performed using fMRI
Allow us to see which sections of the brain are most active during particular tasks.
Increased blood flow to particular regions is detected and overlayed on an MRI image.
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12. IDENTIFYING BRAIN FUNCTIONS Command term = EXPLAIN
How can fMRI (functional magnetic resonance imaging) be used in the identification of the brain part involved in specific functions?
fMRI studies show the functions of various regions
Also show differences and similarities between groups of people
eg. those with autism and those without
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14. IDENTIFYING BRAIN FUNCTIONS Command term = EXPLAIN
How can lesions be used in the identification of the brain part involved in specific functions?
Lesions are areas of damage or tissue death.
Lesions in the brain will impair functions.
By observing differences in behaviour or function, the normal function of the damaged area can be determined.
This type of research lead to the discovery of Broca’s area in the 1860s, the area of the brain responsible for language.
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16. IDENTIFYING BRAIN FUNCTIONS Command term = EXPLAIN
How can animal experiments be used in the identification of the brain part involved in specific functions?
Controversial , but has led to many scientific advances.
Studies involve:
Post-mortem brain dissection
Lesioning of the brain to observe results
Electrical brain stimulation to observe results
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17. AUTONOMIC NERVOUS SYSTEM Command term = EXPLAIN
The Autonomic Nervous System (ANS) is part of the Peripheral NS.
It is responsible for maintaining homeostasis.
It acts through involuntary control of muscles and glands.
There are 2 parts to the ANS:
Sympathetic NS – “fight or flight”; release norepinephrine or noradrenaline
Parasympathetic NS – “rest and digest”; release acetylcholine
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18. AUTONOMIC NERVOUS SYSTEM Command term = EXPLAIN
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19. AUTONOMIC NERVOUS SYSTEM Command term = EXPLAIN
How does the ANS control of heart rate?
Sympathetic NS
Increases heart rate b/c:
body is stressed
more blood flow is needed to get more oxygen to muscles and remove carbon dioxide
Parasympathetic NS
Decreases heart rate b/c:
body is relaxed
less blood flow is needed
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20. AUTONOMIC NERVOUS SYSTEM Command term = EXPLAIN
How does the ANS control movements of the iris?
Sympathetic NS
Contracts radial muscles of the eye (relaxes circular muscles)
Dilates the pupil
allows more light to enter eye, providing a better image of perceived threats
Parasympathetic NS
Contracts circular muscles of the eye (relaxes radial muscles)
Constricts the pupil
allows less light to enter, protecting the retina from damage
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21. AUTONOMIC NERVOUS SYSTEM Command term = EXPLAIN
How does the ANS control blood flow to the gut?
Sympathetic NS
Decreases blood flow to the gut
allows blood to flow to other tissues (eg. muscles) which need more glucose and oxygen
digesting food is a low priority in emergencies
Parasympathetic NS
Increases blood flow to the gut
facilitates digestion
builds up nutrient stores and supplies muscles & tissues with fresh glucose
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23. THE PUPIL REFLEX Command term = EXPLAIN
The pupil reflex is a cranial reflex originating at the brainstem and under the control of the autonomic nervous system
Bright light hitting the retina can potentially overstimulate photoreceptors and damage the retina
The iris will automatically resize to regulate the amount of light that reaches the retina.
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24. THE PUPIL REFLEX Command term = EXPLAIN
DIM LIGHT
Relay neurons stimulate the sympathetic NS
Radial muscles in iris contract
The pupil dilates
BRIGHT LIGHT
Relay neurons stimulate the parasympathetic NS
Circular muscles in iris contract
The pupil constricts
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25. TESTING FOR BRAIN DEATH Command term = EXPLAIN
Doctors can use the pupil reflex to test for brain death in an unconscious patient in need of life support.
If the pupils are unreactive to light, it is an indicator of brain death.
This is because:
It is controlled by the brainstem, so needs brain activity
It is a simple reflex, in need of no conscious decision making
It is under autonomic control, so should be involuntary
If simple reflexes don't work, it is unlikely that higher-order brain function will be possible.
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26. THE PAIN RESPONSE Command term = OUTLINE
The stimulus for pain could be pressure, heat or penetration of the skin
Receptors include nociceptors (pain receptors), stretch receptors, baroreceptors (pressure), thermoreceptors, etc
Spinal nerves relay the impulses to the brain.
These nerves connect with the sensory cortex and the brain perceives “pain”.
This should alert the brain to try to stop the action to prevent further damage.
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28. THE PAIN RESPONSE Command term = OUTLINE
Body tries to reduce the intensity of the pain by producing natural pain killers
to allow the individual to keep functioning and improve survival chances
These pain killers are called endorphins.
Endorphins block NT receptors at synapses involved in pain signal transmission, thus “blocking” the pain.
Endorphins effectively hyperpolarise the postsynaptic membrane of the relay neuron, inhibiting the impulse from being passed on.
These substances are destroyed quickly so that their effects are not long-lasting.
Opiates (like morphine and heroin) mimic endorphins.
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29. THE PAIN RESPONSE Command term = OUTLINE
pain control neuron
sensory neuron
association neuron in brain
motor neuron
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30. Sample questions Q1
Explain sympathetic and parasympathetic control of blood flow to the gut. [6] Q2
Discuss the concept of brain death and how it can be diagnosed. [6] Q3
Outline how pain is perceived and the role of endorphins in this process. [3] Q4
Explain how fMRI scanning can be used in investigation of how the human brain functions. [6]
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31. Sample questions A1
sympathetic NS and parasympathetic NS are part of the autonomic system; have antagonistic actions;
smooth muscle in blood vessels controlled by sympathetic and parasympathetic nerves;
sympathetic system release norepinephrine/noradrenaline; constricting blood vessels to gut; decreasing blood flow to gut;
parasympathetic system release acetylcholine; dilating blood vessels/arterioles to gut; increasing blood flow to gut; 6 max
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32. Sample questions A2 it is a legal/medical definition of death;
some cases of coma are irreversible;
damage in the medulla oblongata is generally permanent;
doctors have to diagnose damage to decide treatment; use tests of brain stem function to decide whether to preserve patient’s life /without brain stem function life cannot continue;
more than one test used to diagnose brain death;
test pupil reflex / shine light into eye; if pupils do not constrict with light this suggests brain death;
no response to pain or cranial reflexes;
definition needed for organ donation / long term use of life-support machines may be inappropriate / bioethical considerations; max
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33. Sample questions A3
impulses passed from pain receptors to sensory areas;
pain is perceived in these sensory areas in the cerebral cortex / feelings of pain in the areas of the cerebral cortex;
endorphins act as painkillers; which block transmission of impulses at the synapses involved in pain transmission; max
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34. Sample questions A4
fMRI records changes in blood flow; active parts of the brain have increased blood flow;
but not all brain activity is detected by MRI;
a subject is given a stimulus which is designed to stimulate brain activity; links stimulus with certain part of the brain; brain activity visualized by coloured images; degree of activity can be represented (by different colours);
temporal activities can be recorded as well; allowing sequential use of the brain to be visualized; collaboration between brain parts; non invasive; max
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