Mind and Body
This page will examine how your physiology (anatomy) influences how you behave.
Nervous System
Below is a diagram of a neurone, these are the cells that make up nerves, they connect together and enable the body to control the muscles from the brain (or spinal chord in the case of a reflex).
The diagram shows a motor neurone, this sends electric impulses to the muscles. In a reflex, the impulse is recieved by a sensory neurone, for example you have touched something hot and then it goes to the central nervous system (brain and spine) where a relay neurone sends the impulse back down a motor neurone which puts the effector into action to cause a response. In this case the muscle in the arm contracts to pull it away from the heat source. And this all happens in a fraction of a second.
The nervous system is divided into the Central Nervous System (CNS) which includes the spinal chord and brain and the Peripheral Nervous System (PNS) and part of this is the autonomic nervous sytem that controls the vital organs.
There are two types of divisions within this. First is the sympathetic division that responds to an emergency and prepares for fight or flight. And then there is the parasympathetic division that relaxes the organs and builds energy reserves.
Fight or Flight
The 'fight or flight' response refers to how the body responds to an emergency situation by either running away (flight) or standing up to it (fight). The type of situation the body has evolved this to deal with is if a predetar was running towards you. However, it is brought into any stressful situation, even if it isn't life threatening: like before an exam for example.
In this response the sympathetic division of the nervous system is stimulated so that the heart beats faster to allow more oxygen to get to the muscles so that they can work more.
Working alongside the nervous system is the hormonal system; chiefly adrenaline which is secreted from the adrenal gland (above the kidney) and maintains a faster heart rate, deeper and faster breathing and breaking down storage into sugar for the muscles to use.
The Brain
As you know it is the brain that is reponsible for our intelligence, thoughts and controlling the body, so not surprisingly, it is the brain more than any other part of your physiology that is of most interest to Psychologists.
In examining the brain, we often use the principle of localisation of cortical function which is the idea that particular regions of the cortex (outside) of the brain are responsible for specific functions.
Research started into this area with Penfield who looked at soldiers with shrapnel injuries (bits of metal) in the brain, he noticed that visual problems were caused by damage to similar areas of the brain.
Other methods of investigating the brain are outlined in the table below.
| Method | What is done | Advantages | Disadvantages |
|---|---|---|---|
| Neurosurgery | Parts of the brain are removed, or links are destroyed. | Precise locations can be identified. Behaviour before and after can be compared. | Is only performed on people who already have serious illnesses as a last resort. Part removed may only be part of a chain. |
| EEGs | Probes are put on the surface of the head to measure brain activity. | Non-invasive and can be done on anyone. | Only measures activity so gives no idea about structure or function. Electrodes take average measurement over broad area. |
| Electrical Stimulation | Microelectrodes are used to stimulate nerves in the exposed brain while patient is conscious. i.e. the skull is removed then patient is woke up (with head numbed) with brain exposed and clamped. | It is very precise. The patient can carry out tasks during the stimulation. Less harmful than neurosurgery and isn't permanent. | It is invasive. Only can be done on people very ill and animals (so generalising to all humans is not possible). Because of the nature of nerves, the stimulation may well spread to other areas. |
| Scans (PET, MRI) | PET uses radioactive sugar to show up active areas of the brain in a scan. MRI uses magnetic fields to produce a 3D image of the brain. | Non-invasive Detailed structure of the brain (MRI) and live information about brain activity (PET). | Only information about the structure. Has poor ecological validity because participant has to keep their help still inside a scanner. |
Further evidence for localisation of cortical function comes from Peterson et al who used PET whilst participants either listened to, thought about or read nouns; it showed that for each of these tasks, specific different areas of the brain were being used.
However, through continued research and ever improving methods, neuroscientists are now coming to the conclusion that perhaps the cortex isn't divided into areas with specific functions after all.
More and more the idea of brain plasticity is being accepted which says that if damaged, other parts of the brain will take over the functions of the bit damaged. Evidence for this holistic view of the brain comes from Lashley, who removed bits of the brain cortex in rats, and found that it wasn't where the tissue was removed that was more important but how much.