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Option A: Neurobiology &
Behavior
A2: THE HUMAN BRAIN
USE THE INFO IN THE PRESENTATION TO COMPLETE A1 NOTES
GUIDE
INFORMATION TAKEN FROM:
HL BIOLOGY 2 ND EDITION DAMON, MCGONEGAL , TOSTO, AND
WARD
BIOLOGY FOR THE IB DIPLOMA PREPARATION GUIDE WALPOLE
How does the brain develop from the neural tube?
• Anterior embryonic neural tube develops to become the brain
•
Nerve cells migrate to the outer edge of the neural tube and causes the walls
to thicken
• At 3 months in utero, the complete structure is in tact
•
Neural tube develops into entire brain and spinal cord
• Rapid growth continues after this point
• Fibers of the nervous system form
• After birth, growth continues … up to 4 times bigger by age 6
Brain Development
Functions of different parts of the brain
• You should be able to label a diagram showing the main areas of
the brain
Hypothalamus
• Pituitary gland
• Medulla oblongata
• Spinal cord
• Cerbellum
• Cerebrum
•
Functions of different parts of the brain
• You should be able to label a diagram showing the main areas of
the brain
Hypothalamus – controls ANS, coordinates endocrine & nervous systems by
regulating pituitary gland secretions
• Pituitary gland – posterior lobe stores & releases oxytocin and ADH from the
hypothalamus; anterior lobe produces & secretes hormones (FSH, GH)
• Medulla oblongata – brain stem, controls automatic and homeostatic
activities (breathing, swallowing, heart rate)
• Spinal cord
• Cerebellum – coordinates movement, posture, balance
• Cerebrum – coordination center for learning, memory, language, reasoning;
receives info from the sense organs, and organizes motor functions
•
Spotlight on the Medulla
• Regulatory Center
Swallowing center: coordinates the muscles of the mouth, pharynx, and
larynx
• Breathing center: monitors level of carbon dioxide in the blood; if increased
level the rate and depth of breathing increase
• Cardioaccelerator center: under the influence of exercise heart rate will
increase by direct stimulation of the cardioaccelorator center
•
The ANS
• Autonomic Nervous System: controls involuntary processes in the
body (swallowing, breathing, heart rate regulation)
• 2 divisions of the ANS (both receive impulses from the medulla)
•
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Sympathetic Nervous System – emergency responses, fight or flight, is
excitatory in effect; ntm = noradrenaline
Parasympathetic Nervous System – controls non-urgent events, relaxed
situations, is inhibitory in effect; ntm = acetylcholine
Autonomic Nervous System
The ANS examples
Parasympathetic System:
Eye: causes contraction of circular muscles of the iris to control the
pupil
Heart: heart rate slowed down, stroke volume reduced as body
relaxes
Digestive System: blood vessels are dilated, increasing blood flow to
the digestive system
The ANS examples
Sympathetic System:
Eye: causes contraction of radial muscles of the iris, dilating the pupil
Heart: heart rate increased, stroke volume increased so that more
blood can pump to the muscles
Digestive System: blood flow to the digestive system is restricted as
blood vessels constrict
Pupil Reflex
Cerebral Cortex Evolution in Humans
• Cerebral cortex of a human brain is the outer layer of the 2 cerebral
hemispheres known as grey matter
• Controls functions like speech and decision making
• Only found in mammals
• Is folded so that its large surface area can fit into the skull
Cerebral Hemispheres
• Control higher order functions
•
Learning, memory, recall, speech and emotions
• The right and left hemispheres contain different types of cells and
different neurotransmitters
• Different areas of the cerebral cortex
also have different functions
Left and Right sides of the brain
• Right hemisphere receives info from the left side of the body
• Left hemisphere from the right side of the body
• Both hemispheres process information, but with different functions
Broca’s area: speaking and writing
Wernicke’s area: understanding of language
Left Hemisphere: communication (speaking, sign language)
Right Hemisphere: understanding words, recognizing faces, spatial reasoning
Correlation between body and brain size
• E:S Ration: Weight of the brain compared to weight of the body
•
E = brain weight S = body weight
Powering Brain Activity
• Very energy costly to fuel neurons and maintain membrane
potentials of brain cells
• 25% of the body’s metabolic energy requirement goes to the brain
• Most of the energy supplied by aerobic respiration
• Active regions of the brain use more energy than non-active regions
• fMRI scanning can be used to identify areas of activity during
different actitivies
Brain imaging technologies
• Neurobiology/Neuroscience: study of complex processing occurring
in the nervous system
• Animal studies – behavior studies
• Brain injury studies – how different areas are affected when
damaged by studying lesions
• MRI Scanning – locates abnormalities
• fMRI (functional magnetic resonance imaging) scans monitor brain
activity from the blood flow to different areas
Brain Death
• That time when a physician has determined that the brain and brainstem
have irreversibly lost all neurological function
• In a coma, there are signs that can be measured
• Testing for brain death:
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Movement of extremities
Eye Movement
Pupil Reflex
Corneal reflex (blinking)
Gag reflex
Respiration response
Check for understanding
1. Name 2 higher order functions and the area of the brain which
controls the functions.
2. If a person suffered an injury to Broca’s area of the brain, what
functions might be affected?
3. Draw and annotate a diagram of the human brain.
4. Explain why brain metabolism requires a large input of energy.