B6

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  • B6
    • Reflexes
      • Organism detect and respond to a stimulus (change in the environment)
        • Receptors are stimulated by the stimulus and produce a rapid, involuntary response (Simple Reflex)
      • Receptors are stimulated by the stimulus and produce a rapid, involuntary response (Simple Reflex)
      • Animals react in a way that will result in survival
      • Simple Reflexes in Babies
        • Absense of reflexes or failer to disapear my lead to a babies nervous system delevoping incorrecty.
        • Stepping Reflex - babies feet on firm surface, walking movements
        • Grasping- baby grasps finger when placed in hand
        • Sucking - baby sucks on finger when in its mouth
        • Startle - baby shoots out arms and legs when startled
        • Rooting - baby turns head, opens mouth when cheek touched.
        • Adults
          • Pupil reflex - bright light makes muscles in iris to contract, retina not damaged.
          • Knee-Jerk - when knee struck, leg kicks out.
          • Dropping hot object - picking up hot object results in throwing it away.
      • Sending Signals
        • Hormones
          • Insulin (controls blood sugar levels) and oestrogen are secreted in blood.
          • Chemical signals are very slow and move to target organs
          • Effects last for longer
    • Detecting Changes
      • Animals require presence of one or more receptors to detect stimuli
      • Light - receptors in eyes
      • Sound - receptors in ears
      • Changes of position - receptors in balance in inner ear
      • Taste - receptors on tongue
      • Snell - receptors in nose
      • Pressure - receptors for pressure in skin
      • Temperature - receptors for temp. in skin.
    • Coordinating Response
      • Receptors are connected to the processing centre (spinal cord for simple reflexes) by Sensory Neurons
      • The processing centre coordinates a response by sending back an electric impluse through motor neurons to the effector
      • Effectors carries out the response - Spinal Reflex Arc.
      • Drawing Pin Example:
        • 1) A receptor is stimulated by drawing pin (effector)
        • 2) This causes impulses to pass along a sensory neuron to spinal cord
        • 3) Senesory neuron synapses with relay neuron.
        • 4) Relay synapses with motor neuron, sending impulses down it
        • 5) Impulses go to the muscles (effectors) and causing them to contract in response.
      • Arrangement of neurons into fixed pathway in reflex arc means responses are automatic and quick
      • If signal had to travel to brain, response may be too slow
    • Receptors and Effectors
      • Muscle Cells
        • Speciallised cells that make up the tissue are effectors
        • Impulses travel along motor neurons and terminate @ muscle cells - causing them to contract
      • Light receptors in Retina
        • The lens focuses light onto receptor cells in the retina which are sensitive to light
        • The receptor cells are stimulated and the optic nerve carries impulses along sensory neurons to the brain
      • Hormone Secreting Cells in a Gland
        • These cells are effectors
        • Activated by an impulse which travels along a motor neuron from CNS and terminates at gland.
        • Impulse triggers release of hormone into bloodstream, which transports to required sites
    • Structure of Neurons
      • Carry electrical signals (nerve impulses)
      • Elongated to make connections between parts of body
      • Branched endings - allow single neuron to act on other neurons/ effectors
      • Motor Neurons
        • Cytoplasm forms long fibre surrounded by cell membrane - An Axon
        • Some axons surrounded by a fatty sheath
          • Insultes neurons from neighbouring cells
          • Increses speed of impulses
    • Central Nervous System
      • Info. from neurons is co-ordinated here
      • Made up of brain and spinal cord
      • - Receptor- Sensory N- Relay N-Spinal Cord- Bain -Spinal Cord-Motor N- Effector
      • CNS connected to body via sensory and motor neurons - Peripheral Nervous System
        • PNS sensory and motor neurons transmit messages all over body and to and from CNS
    • Synapses
      • Gaps between adjacent neurons
      • Number in the brain decreases with age - stabilising by adulthood
      • impulse reaches end on neuron, triggers release of chemicals - Transmitter Substanses, into synapse.
      • Diffuse across synapse and bind with specific receptor on relay neuron membrane
      • Transmittter substance reabsorbed by sensory neuron
        • By transporter molecules.
      • 1) Nerve impulse moves through sensory neuron
      • 2) Transmitter substances released into synapse
      • 3) T.S bind with receptors on motor neuron
      • 4) Nerve impulsesent through motor neuron
      • Drugs and the nervous system
        • Ecstasy affects transmitter substance - Serotonin
        • Serotonin has mood enhancing effects eg. happy
        • Ecstasy blacks sites in brains synapses whewre chemical serotonin is removed
        • Serotonin concentrations in brain incease and makes people very happy.
        • Long term consequence - memory loss
    • Cerebral Cortex
      • Part of bruan associated with intelligence, memory, language and consciousness
      • Variety of Methods to map different regions of the cortex
        • Physiological Techniques
          • Damage to diff. parts of brain give diff. problems
          • Studying effects of accidents/illnesses leads to understanding
          • Directly stimulating the brain with electrical impulses leads to an understanding of what parts control what
        • Electronic Techniques
          • Electroencephalogram (EEG) is a visual record of the electrical activity generated by neurons in the brain
          • By amplifying electrical signalspicked up through skull, trace produced showing rise an fall of electrical potentials (Brain Waves)
          • Stimulating receptors means parts of brain that respond can be mapped
        • Magnetic Resonance Imaging (MRI)
          • Technique that produces images of cross sections of the brain
          • Computer-generated image uses colour to represent different levels of electrical activity
          • Activity in brain changes depending on what the person is doing/thinking
    • Conditioned Reflexes
      • Reflex responses to a new stimulus can be learnt
      • Body learns to produce a specific response when a certain stimulus is detected
      • Works by building an association between the new stimulus (secondary stimulus) and the stimulus that naturally triggers the response (primary stimulus)
      • Final response has no direct connection to the stimulus
      • Some conditioned reflexes can increase a species chance of survival
    • Development of Brain
      • Mammels have a complex brain that contains billions of neurons
      • Neuron pathways are formed  in brain during development
      • The way in which the animal interacts with its environment determines what pathways are formed
      • Huge variety of pathways = animals easily adapt to new situations
      • As each neuron matures, it sends out multiple branches, increasing the no. of synapses
      • Each time there's a new experience, different pathways between neurons are stimulated
      • Everytime an experience is repeated, the pathway is strengthened
      • Pathways not used regularly - deleted
      • These modifications mean pathways become more likely to transmit impulses than others and person will become better at task
      • Certain tasks are learnt through repetition
    • Feral Children
      • Neural pathways not used = deleted
      • If a new skill not learnt by particular stage in development, person not able to learn it in same way as normal
      • Feral children dont go through normal development process - isolated from society
    • Child Development
      • Milestones that can be checked to see if development is following normal patterns
      • If milestones are missing or late it could mean there are neurological problems or child is lacking simulation
    • Memory
      • Verbal Memory (words and labels) can be divided into Short Term and Long Term memory
      • Short-Time - Stores limited amount of info. for limited time (15-30 secs)
      • Long-Term - store unlimited amount of info.
      • In short term, up to seven seperate pieces of info can be stored
      • Capacity can be increased bu Chunking the info. ie. putting it into smaller chunks
      • Long term is where info. is stored in brain through repetition which strengthens and builds up neuron pathways
      • More Likely to rememeber when:
        • Its repeted
        • Strong stimulus associated
        • Pattern to it
    • Memory Models
      • Sensory memory lasts 1-2 seconds

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