The Brain | Biology for Grade 10 PDF Download

The Brain: Basics

• The brain alongside the spinal cord is part of our central nervous system
• The brain is made of billions of interconnected neurones and is responsible for controlling complex behaviours
• Within the brain are different regions that carry out different functions

Structure of the Brain

• Scientists have discovered that different regions of the brain seem to be responsible for controlling different functions, these regions include:
  • The cerebral cortex: this is the outer layer of the brain which is divided into two hemispheres. It’s highly folded and is responsible for higher-order processes such as intelligence, memory, consciousness and personality
  • The cerebellum: this is underneath the cerebral cortex and is responsible for balance, muscle coordination and movement
  • The medulla: this region controls unconscious activities such as heart rate and breathing
    
    The brain is made from billions of interconnected neurones which are organised into regions

Investigating the Brain

Higher tier only

• The brain is an incredibly complex and delicate organ – this makes it extremely difficult for neuroscientists to study it to find out how it works
• Our understanding is limited because the brain is so complex and different regions can’t be studied in isolation
• Our limited understanding means that treating brain damage and disease is very difficult; in addition, any potential treatment carries risks of further damage occurring which can lead to increased problems
• Accidental damage could lead to speech or motor issues, or changes to personality which are permanent

Mapping regions of the brain

• Neuroscientists have been able to map the regions of the brain to particular functions by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques
• Patients with brain damage can be studied to see what effect it has on them physically or on their personality or capabilities
• The most famous example of this is Phineas Gage, a railroad construction worker who survived a large iron rod being driven completely through his head – his frontal left lobe was completely destroyed and his personality and temperament changed drastically
• Tiny electrodes can be pushed into different parts of the brain, tiny jolts of electricity stimulate these regions and the effects can be observed
• For example, if a region in the medulla responsible for movement is stimulated, the movement caused can be observed
• MRI scanners are very important diagnostic tools used to study the brain and other regions of the body using magnetic fields and the effect these have on protons in the water molecules of the body
• Functional MRIs can produce images of different regions of the brain that are active during different activities like listening to music or recalling a memory (the scanners can detect changes in blood flow – more active regions of the brain have increased blood flow)

Exam Tip: In the exam you may be asked to evaluate the benefits and risks of procedures carried out on the brain and nervous system. The benefits of procedures being carried out usually involve improving the quality of someone’s life (as the procedure is used to treat a disorder of some kind) but there are risks of more permanent damage, some of these will be because we still don’t fully understand how the brain and nervous system works!

Investigating the Brain - Higher

Modern science has allowed scientists to discover how different parts of the brain function. Neuroscientists have been able to map various regions of the brain to particular functions by studying patients with brain damage, electrically stimulating different parts of the brain and using MRI scanning techniques.

Brain damage

A well-documented example of brain damage is of Phineas Gage, who in 1848 had a serious accident whilst laying railway tracks and an iron rod went through his skull.
Phineas Gage

Phineas survived the accident, but it was documented that his personality changed following it. It was noted that he lost his inhibitions socially and emotionally.
Doctors realised the changes in Phineas were due to the damage in the particular parts of the brain that the iron rod had passed through. This important case allowed scientists to examine the effect of the injuries on his brain activity.

Non-invasive brain procedures include

Electrical stimulation
Scientists have stimulated different parts of the brain with a weak electrical current and asked patients to describe what they experienced. If the motor area is stimulated, the patient makes an involuntary movement. If the visual area is stimulated, they may see a flash of colour. EEGs (Electroencephalograms) can be created and studied, to observe the electrical activity in the brain.

MRI brain scans
Modern imaging methods such as MRI (Magnetic Resonance Imaging) scans, use strong magnetic fields and radio waves to show details of brain structure and function. Patients are asked to perform various tasks and, by looking at the scan, scientists can see which parts of the brain are active when the task is carried out.

Risks
Brain surgery may be needed to remove a tumour or excess fluid, such as blood. All surgery carries a level of risk, but due to the complexity and delicacy of the brain, investigating and treating brain disorders can be very difficult. If surgery is undergone more damage or side-effects may be created, which could affect the patients' quality of life. Serious considerations about the risks involved against the benefits need to be undertaken first.