1. The Human Brain
HL Only

2. E Label, on a diagram of the human brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemisphere.

3. Label the brain

5. E.5.2 Outline the functions of each of the parts of the brain listed in E.5.1

7. The brain is the most complex organ in the body.
Weighs about 1.4 kg
Contains over 100 billion neurones with thousands of synapses
New connections made daily
Regulates & monitors unconscious body processes
Receives & interprets information from our senses
Controls voluntary movement

8. E.5.3 Explain how animal experiments, lesions and fMRI (functional magnetic resonance imaging) scanning can be used in the identification of the brain part involved in specific functions.

9. Brain Lessions
Accidents to the brain, stroke and tumours can damage specific parts of the brain, the damaged area is a lesion. From the position of the lesion, we can determine functions of that part of the brain by observing what the patient can no longer do.

10. Broca’s area
The most famous study is of a region known as Broca’s area, in the 1860’s. One patient, Leborgne, could only speak one word. Lelong could only speak a few words.

11. When they died, Broca examined their brains
Broca’s area
When they died, Broca examined their brains
Lesions were found in the same area
Deduced this region was responsible for language
Broca’s area – interferes with localization
Wernicke’s area – affects the ability to put words into sentences
fMRIs have confirmed this
Brain divided into left & right hemispheres
Connected by the corpus callosum
Not the same functions

12. Right & Left Hemisperes
Right Hemisphere
Left Hemisphere
Specializes in receiving & analyzing information from all of our senses
Problem identifying faces
Problems locating an object correctly in space
can’t identify melodies
Important for all forms of communication
Difficulty speaking
Difficulty doing complicated movements of the hands/arms
Deaf people with damage here – can’t use sign language

13. How do we know about the functions of the brain?
fMRI
How do we know about the functions of the brain?
“Brain Mapping” – uses radio waves & a strong magnetic field (not Xrays)
Can see the blood flow in the brain as it occurs
Increased blood flow to regions of the brain is detected and overlayed on a brain map
Allows us to see which sections of the brain are most active during particular tasks

14. fMRI
Studies have been used to discover the functions of various regions of the brain
To show differences and similarities between groups of people and are a useful diagnostic tool in medicine

15. Animal Experiments
Are often controversial
Have led to many advances in science
Key to 19th century discoveries

16. Animal Studies
Studies involved
dissection of human brains (post-mortem) –compared to animal specimens
Removal of sections of animal brains - to observe impaired function (Flouren – exp. on pigeons. Removal of the cerebellum led to its discovery as the movement centre of the brain)
Electrical stimulation of living primate and dog brains in order to observe movement and actions in the body

17. Animal Studies
One type of animal experiments is to expose animal models to addictive substances in controlled situations.
Want more and more of the substance
Spend lots of time and energy getting it
Keep taking it despite adverse conditions
Have withdrawal symptoms on withdrawal of the substance
Go back to the substance when stressed
Go back to the substance with another exposure to that substance

18. To test if a chemical meets the criteria for addiction
An animal is trained to press a lever to get a reward
The animal is given an injection of the addictive substance. The lever must automatically give the injection if it is pushed by the animal. (self-administration)
In order for this to be a controlled experiment, 2 levers must be available, one which gives the substances & one that doesn’t
If the substance is ‘reinforcing’, the animal will seek to repeat the experience by pushing that lever much more frequently

19. Animal Experiments

20. E. 5.4 Explain sympathetic and parasympathetic control of the heart rate, movements of the iris and flow of the blood to the gut

21. Sympathetic & Parasympathetic control
Central Nervous System
Brain & Spinal Cord
Peripheral Nervous System
Somatic & Autonomic

22. Cardiac muscle Smooth muscle PNS (involuntary) Autonomic sympathetic
parasympathetic
(voluntary)
Somatic
From senses to muscles
Cardiac muscle
Smooth muscle

23. Antagonistic

24. Target
Sympathetic
Parasympathetic
Heart rate
Increase heart rate
Decrease in heart rate
Blood vessels
Decreases diameter of major arteries therefore increasing blood pressure
Increases diameter of major arteries therefore decreasing blood pressure
Flow of blood to intestines (gut)
Decreased flow to intestines
Increased flow to intestines
Iris movement
Iris muscles cause pupil to dilate
Iris muscles cause pupil to constrict

25. Heart Rate

26. Gut Blood Flow

27. Iris Control

28. E.5.5 Explain the pupil response

29. Pupil Reflex

30. Pupil Reflex
Cranial reflex
Not spinal cord reflex

31. E.5.6 Discuss the concept of brain death and the use of the pupil reflex in testing for this.

32. Determining Brain Death
We can artificially maintain the body using ventilation & circulation
Brain stem controls heart rate, breathing rate and blood flow
That time when a physician has determined that the brain and brain stem have irreversibly lost all neurological function.
What is the definition of brain death?

33. Profound or deep state of unconsciousness
Coma vs Brain Death?
Coma
Brain Death
Profound or deep state of unconsciousness
Still have neurological signs
No eye-opening
Unable to follow instructions
No speech or other forms of communication
No purposeful movement
Must perform a toxicology test
Examination
Movement of extremities
Eye movement
Corneal reflex
Pupil reflex
Gag reflex
Respiration response

34. Spinal reflexes may still function – knee jerk

35. E.5.7 Outline how pain is perceived an dhow endorphins can act as painkillers.

36. Stimulus: Pressure, heat or penetration (nocioreceptors)
Perception of Pain
Stimulus: Pressure, heat or penetration (nocioreceptors)
Housed in the skin, muscles, bones, joints & membranes around organs
Impulse: relayed to brain via spine
Perception: in cerebral cortex leads to feelings of pain
Function: pain acts as a ‘stop’ signal to prevent more damage to the body
Muscles stop the action causing the pain stimulus
Alerts the autonomic nervous system if the pain requires change in heart rate or breathing
Can direct other brain cells to release pain-suppressing
endorphins

37. Pain is in the Brain!

39. Endorphins
First discovered by scientists studying opium addiction
Found receptors for opiates, morphine & heroin in brain cells
Morphine & heroin bound to the brain receptors because they were mimicking endorphins
Endorphins are CNS neurotransmitters with pain-relieving properties
They are small peptides which bind to opiate receptors & block the transmission of impulses at synapses involved in pain perception

40. Endorphins