B6: Brain and Mind

reflex actions
1. Reflex actions are rapid and happen without us thinking. For example, you would pull your hand away from a hot flame without thinking about it.
  1. This is what happens: receptor detects a stimulus - change in the environment sensory neurone sends signal to relay neurone motor neurone sends signal to effector effector produces a response
    1. light is also a reflex action. In bright light: Less light enters the eye through the contracted pupil. In dim light:More light enters the eye through the dilated pupil.
2. When a receptor is stimulated, it sends a signal to the central nervous system, where the brain co-ordinates the response. But sometimes a very quick response is needed, one that does not need the involvement of the brain. This is a reflex action.
Central Nervous System
1. (the brain and spinal cord) connected to body by sensory & motor neurons= peripheral nervous system (PNS)
  1. PNS is 2nd major division of nervous system
    1. its sensory+motor neuron transmit messages all over body+transmit messages to and from CNS
2. the most important part of nervous system. if you break your spine, you become paralysed. if you damage your brain you can die. the CNS causes reverse movements. the PNS senses change in the environment + this changes in the bone.
3. Sensory neurons carry impulses from receptors to the CNS.
  1. Motor neurons carry impulses from the CNS to effectors.
    1. Sensory and motor neurons form part of the peripheral nervous system.
behaviour voluntary and invouluntary
1. simple reflexes in humans
  1. stepping: this supports evolution because in past babies used to walk with their families
    1. gripping: babies used to hold on to mums fur
      1. startled: loud noises make babies reach out for accomplice
        grasping: babies tightly grasp a finger that is placed in their hands
        rooting: touching the cheek makes babies turn towards the breast
        sucking: babies suck on a finger or mothers nipple that is put in its mouth
2. simple reflexes are called involuntary: we cant help doing some movements e.g. sneezing blinking
receptors and effectors
1. lens: focus the light on retina
  1. retina: contains sensitive receptor cells
    1. optic nerve: sends electrical signals called impulses to brain
    2. retina: senses light+colour, receptor cells sends info to the brain
2. Effectors = any part of the body that produces the response.some examples of effectors: a muscle contracting to move the arm. a muscle squeezing saliva from the salivary gland. a gland releasing a hormone into the blood.
3. Receptors are groups of specialised cells. - detect changes in the environment, - called stimuli, + turn them into electrical impulses. Receptors often located in sense organs, such as the ear, eye + skin. Each organ has receptors sensitive to particular kinds of stimulus.
brain
1. memory and learning
  1. Short-term memory lasts for about 30 seconds. This is why, when you look up a new telephone number, by the time the call has ended you have forgotten the number.
    1. Long-term memory may last for the whole of your life. When you sing the words of a favourite song, you are using your long-term memory. Although we often complain about how hard it is to learn new things, there is no limit to how much information you can store in your long-term memory.
  2. Memory is improved through repetition. If we repeat things, especially over a long period of time, we are much more likely to remember them using our long-term memory
    1. A strong stimulus - including colour, light, smell or sound - also helps us to remember things.
      1. We are more likely to remember information if we can either see or make a pattern out of it.
2. The cerebral cortex is the part of the brain responsible for intelligence, language, memory and consciousness.
  1. Scientists have stimulated different parts of the brain with a weak electrical current then 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.
3. There are billions of neurons in the human brain
  1. Learning occurs when humans interact with their environment. This causes more neural pathways to be formed in the brain.
    1. Learning results in these neural pathways being used more than other neural pathways
      1. An example of a skill that can only be acquired at a certain age is learning language for the first time.
our nervous system and drugs
1. Some drugs and toxins affect how impulses pass from one neuron to the next across a synapse.
  1. curare (a drug) stop the impulse from passing across the synapse.They cause complete paralysis/ stop the person from breathing.
    1. Other drugs stimulate the synapse so that once an impulse crosses the gap the impulse is repeated over and over again. Drugs such as strychnine do this. They cause all the muscles in the body to go into a continuous spasm of constriction. This also stops the person from breathing.
      1. Strychnine is used by Australian aborigines to paralyze fish
        Serotonin is a chemical that is released into synapses in the brain. An increase in serotonin makes us feel happier.
        Ecstasy is a drug that blocks the serotonin in the synapses in brain. This prevents the serotonin from being absorbed by the receptor molecules.=level of serotonin in the synapse increases.= a feeling of happiness. However, the use of Ecstasy reduces memory. can also cause severe dehydration= death.
2. Curare can cause complete paralysis.
  1. Strychnine can cause a continuous spasm.
    1. Ecstasy works by blocking the sites in the brain's synapses where serotonin is removed.
      1. The mood-enhancing effects of Ecstasy are due to an increase in serotonin concentration.
conditional response
1. it is when you learn something and remember it.
  1. e.g. pavlov+dog
    1. Show dog food --> Dog drools (reflex action) Ring bell, show dog food --> Dog drools (If you continue this, ringing the bell before food repeatedly you get: Ring Bell ---> Dog drools (conditioned reflex action)
2. conditioned reflex
  1. Conditioned reflexes are useful because they increase an animal’s chances of survival.
    1. e.g. 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.
      1. a hoverfly mimics a wasp with its black and yellow stripe, the birds will not eat it because they dont want to be stung. this helps the hoverfly to survive
  2. A conditioned reflex has no direct connection to the stimulus
3. 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.
feral children
1. isolated from society
  1. in a cellar or locked room
    1. dont have the ability to talk, instead they grunt noises
2. these are children who do not learn a language
neurons
1. reflex arc
  1. The best description of the pathway of a reflex arc is: receptor - sensory neuron - spinal cord - motor neuron - effector
  2. The brain can modify a reflex arc via the motor neuron of the reflex arc.
2. neuron
  1. sensory neurons carry signals from receptors to the spinal cord and brain. relay neurones carry messages from one part of the CNS to another. motor neurones carry signals from the CNS to effectors.
    1. The axon is surrounded by a fatty layer known as the myelin sheath. This helps to protect the neuron and allow impulses to travel faster.
3. The fatty sheath does not connect two neurons together
  1. Chemicals are released into the synapse at the end of a sensory neuron.
    1. chemicals that are released by a sensory neuron into a synapse when they reach a motor neuron bind with receptor molecules
      1. Receptor molecules only bind with specific chemicals
        After a chemical released from a sensory neuron binds with a receptor molecule, a nerve impulse is initiated
synapses
1. gaps between neurons.
  1. how do synapse work?
    1. impulse comes down, serotonim is quickly given off. serotonim diffuses+fills receptors. when receptors are filled the excess serotonim are reabsorbed into the first neuron. this triggers an electrical impulse in the second neuron.
stimulus is a change in the environment

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