1. E.5 The Brain

3. IB Assessment Statement
E.5.1 Label, on a diagram of the brain, the medulla oblongata, cerebellum, hypothalamus, pituitary gland and cerebral hemispheres.

5. Function of the Parts of the Human Brain
Medulla oblongata: controls automatic and homeostatic activities, such as swallowing, digestion and vomiting, and breathing and heart activity.
Cerebellum: coordinates unconscious functions, such as movement and balance.
Hypothalamus: maintains homeostasis, coordinating the nervous and endocrine systems, secreting hormones of the posterior pituitary, and releasing factors regulating the anterior pituitary.
Pituitary gland: the posterior lobe stores and releases hormones produced by the hypothalamus and the anterior lobe, and produces and secretes hormones regulating many body functions.
Cerebral hemispheres: act as the integrating centre for high complex functions such as learning, memory and emotions.

6. IB Assessment Statement
E.5.2 Outline the functions of each of the parts of the brain listed in E.5.1.

7. IB ASSESSMENT STATEMENT
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.

8. Types of techniques that are used to find out what the function of each part of the brain is:
Functional magnetic Resonance Imaging:
Lesions:
Animal Experiments:

9. E.5.3 Techniques used to discover the function of the brain (fMRI)
FMRI (functional magnetic resonance imaging) scanning
Is a technique used to discover which part of the brain are activated by a specific process.
The experimental subject is placed in a scanner and a high resolution scan of the brain is taken.

10. E.5.3 Techniques used to discover the function of the brain (fMRI)
FMRI (functional magnetic resonance imaging) scanning
The fMRI shows areas of the brain which have increased blood flow.
Increased blood flow is associated with increased neuron activity.
During experiments, when presented with a stimulus the fMRI is taken and the region of the brain with increased blood flow is linked to with the processing of that stimulus information.

13. E.5.3 Lesions
Lesions: Accidents, stokes, and tumors can be damage specific parts of the brain.
These damaged areas are called lesions.
From these damaged areas function of these areas can be deduced.
For example, lesions in the Broca’s area of the left hemisphere of the brain cause dysphasia (inability to speak), but reading and writing is still possible…..thus from this scientists know the Broca part of the brain is important for processing speak.

15. E.5.3 Lesions case study Lesion Studies:
As is often the case in medicine improved understanding of normal function often comes from the study of disease or injury.
Study of when things go wrong often provides insight into normal function.
Lesions of brain result in a loss or alternation of behaviour linked to the region of the brain affected by the lesion.
Example: Phuneas Cage 1848

Was working on a construction when an explosion sent a long metal rod through his skull penetrating near the eye and exiting through the roof of the skull. Phineas did not die, but the rod had passed through the frontal lobes of the cerebral cortex. Whilst he survived the accident his personality was altered and his ability to interact socially was impaired. This is an extreme example

16. E.5.3 Animal Testing
Many experiments have been performed of animals, including primates.
Often the procedures involve surgical procedures – parts of the skull have to be removed to access the brain.
The animal must be keep alive so that the brain is still functioning.
Experimental procedures are carried out on the brain and the effects of the animal are then observed, either during the operation or afterwards.

18. IB ASSESSMENT STATEMENT
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.

19. IB Assessment Statement
E.5.4 Explain sympathetic and parasympathetic control of
the heart rate,
movements of the iris
and flow of blood to the gut.

20. E.5.4 Sympathetic and Parasympathetic Nervous system
Heart rate is controlled by the autonomic system which is also divided into two parts,
the sympathetic
and parasympathetic nervous system.

22. "Rest and Digest" responses Fight or Flight" responses
Parasympathetic
"Rest and Digest" responses
Sympathetic
Fight or Flight" responses

23. E.5.4 Nervous Control Of the Heart Beat
Nerve control (extrinsic control):
The cardiac center in the medulla oblongata (located at the base of the brain) controls cardiac output (both heart rate and stroke volume).  
stroke volume (SV) is the volume of blood pumped from one ventricle of the heart with each beat
Opposing sympathetic (stimulatory) and parasympathetic (inhibitory) impulses control the pacemaker.

24. E.5.4 Slowing Down the Heart Rate
Vagus nerve is a cranial nerve that is part of the parasympathetic division of the autonomic (automatic) system.
It arises from the medulla oblongata.
Carries impulses to the heart continuously.
Secretes a chemical called acetylcholine on the heart.
This chemical inhibits the pacemaker, causing the heart rate to slow and the contractile strength of the muscle to weaken.

25. E.5.4 Speeding up the Heart Rate
Accelerator nerve is part of the sympathetic division of the autonomic nervous system.
It arises from the medulla oblongata
The nerve secretes epinephrine (also called adrenalin).
Epinephrine stimulates the pacemaker, causing the heart rate to increase, and contraction strength to increase.

26. http://highered. mcgraw-hill

27. E.5.4 Blood Flow to the Gut
Parasympathetic System: Blood vessels are dilated, this increases blood flow to the gut.
Sympathetic System: Blood vessels are constricted, decreases blood flow to the gut.

29. E.5.4 Iris of the eye
The iris reflex is under the control of the autonomic system.
If light is particularly bright the receptors cells of the retina can be come over stimulated.
To prevent over stimulation the iris is able to reduce the amount of light entering through the constriction of the pupil that as much light as possible reaches the retina the pupil dilates.
The mechanisms in the eye is based on two sets of muscles, the circular and radial muscles.
This antagonistic pair of muscles makes up the iris

30. E.5.4 Iris of the eye
Parasympathetic System: causes circular muscle fibres contract so the pupil constricts to protect the pupil
Sympathetic System: Causes Radial muscles to contract, dilating the pupil to give it a better image.

31. E.5.4 Iris of the eye

34. IB Assessment Statement
E.5.5 Explain the pupil reflex.

35. IB Assessment Statement
Discuss the concept of brain death and the use of the pupil reflex in testing for this.

36. E.5.6 Death and the pupil reflex
Descriptions of death at the biological level:
Cardiac Death Criteria:
No heart beat
Ventilation has stopped
Machines required to carry out basic life processes
Brain Death
Brain no longer responds to stimuli
No purposeful movement or response

37. E.5.6 Death and the pupil reflex
To determine if the brain is still functional stimuli are presented such as shining light into the eye and looking for the associated pupil reflex. A reflex would indicate some function at the basic brain level of the medulla oblongata.
Absence of the pupil reflex indicates no basic brain function and allow surgeons to progress towards harvesting organs.
Much of this issue depends on ones definition of 'living' and on local and national laws.
In the event of death cardiac output and ventilation can be maintained artificially. Some people may have decided to donate their organs for transplant but if organs are harvested it would be necessary to establish that the person was no longer capable of any brain function that would be associated with the concept of the person being 'living'.

38. E.5.7 Pain perception and the role of endorphins
When a pain receptor in the skin is stimulated impulses are transmitted to the central nervous system to the sensory areas of the cerebral cortex.
The pituitary secretes Endorphins into the blood stream and the hypothalamus secretes them into the brain to block the receptor molecules at synapses. In doing so the pain is reduced.
An awareness of pain allows one to avoid acute injury being aggravated into chronic injury.
An awareness of pain allows one to avoid noxious substances.
Perception of pain is also used in aspect of social organisation e.g lion cubs mock fighting
Having the perception of pain has a distinct survival benefit however there comes a point at which the pain needs to be blocked.