Unit B6: Brain and Mind

REVISION

UNIT B6: GROWTH AND DEVELOPMENT

Simple Reflexes, Conditioned Reflexes, Effects of Drugs, Brain and memory

Simple reflexes - produce rapid, involuntary responses to a stimulus - This aids chance of survival
Simple reflexes in animals: - Used for majority of behavior - makes it difficult to adapt to new situations
- Moving towards and finding food
- Moving away and sheltering from predators
- Moving towards and finding a mate

Simple reflexes in humans:
- Pupil reflect - Pupil gets bigger in dim light to allow more light in to the eye to produce a clear image on the retina
- Babies are born with simple reflexes - Startle; Swimming; Grasping; Sucking; Rooting; Stepping

Reflex arc: the nerve pathway which makes such a fast, automatic response possible.
- Stimulus (i.e heat)
- Pain receptor stimulated
- Signals travel from Sensory neuron
- Travel via the Relay neuron (sending message signals to the brain)
- Signals sent along the Motor neuron
- Effector muscle contracts (response)

Conditioned reflexes sre responses to a stimulus that have been learned through experience

- Increase an animals chance of survival - For example, birds will not eat caterpillars with bright colouring because they are conditioned to think of bright colours as poisonous. Some caterpillars use this to their advantage. Their bright colours protect them, even though they are not poisonous.

Pavlov and his dogs: A russian scientist trained dogs to salivate on hearing a bell
- The dog salivates naturally when given food (Food is primary stimulus)
- Pavlov rings a bell every time the dog eats (Bell is secondary stimulus)
- After much repetition, the dog salivates everytime it hears a bell ring, even without food

In a conditioned reflex the final response (salivation) has no direct connection with the stimulus (ringing bell).

Modifying a reflex response:
In some circumstances the brain can modify a reflex response. It does this by sending an impulse along a motor neuron of the reflex arc. This enables us, for example, to hold onto a hot dinner plate when normally we would drop it.

"Some drugs and toxins affect how impulses pass from one neuron to the next across a synapse"

Drugs and synapses
- Drugs such as curare stop impulses dispersing across the synapse. This can cause complete paralysis.
- Other drugs stimulate the synapes so the diffusion of impulses if repeated again and again. Muscles spasms

Serotonin - Happy chemical that is released in to synapses in the brain
Receptor molecules on the other side of the synapse absorb serotonin to prevent it building up

Ecstasy
- Blocks serotonin receptor sites in synapses in the brain
- Prevents serotonin being absorbed causing a build up of the chemical in the brain
- Increase in serotonin causes a feeling of well being
- Can cause memory loss
- Can cause severe dehydration which may result in death 

The Brain:
Cerebral Cortex - Controls intelligence, language, memory and consciousness
Studying the brain - MRI Scans, Electrical stimulation, Studying the Brain damaged
Billions of neurons and pathways in the brain

Memory
Short-term memory - Lasts approx. 30 seconds - Alzheimer's effects short term memory
Long-term memory - Can be lifelong, No limit to the amount of information your long-term memory can store - Brain damage can erase long term memory, however short term memory is not affected

Improving our memory
- Repetition
- Strong stimulus - Could include colour, light, smell or sound
- Patterns or stories -  Creating stories from lists of words
 
 New experiences and new skills
-When we have a new experience, a new pathway is built in the brain. If these experiences are repeated, neurons repeatedly travel along these pathways making them stronger. 
- Some skills can only be developed at a particular age, for instance learning a language - feral children