Neurons and synaptic transmission
-neurons send and receive nerve impulses (electrical information) from other neurons or others cells
-Sensory neurons carry information from the senses to the central nervous system
-Motor neurons (see on the right) transmit messages from the central nervous system to the muscles
-Interneurons (connector neurons) connect neurons to other neurons

-Neurons contain a cell body, an axon and branch-like dendrites. Cell body contains DNA (genetic material)
-Within the cell information travels by electrical impulses
-fatty myelin sheath insulates the axon and speeds up transmission of electrical impulses along it
-terminal button at end of axon houses vesicles (tiny sacks) containing neurotransmitters
- synapse =gap between adjacent neurons
-when an electric pulse travels to the end of the axon, vesicles release their neurotransmitter across the synapse. neurotransmitter locks into special receptor sites on the dendrite of the adjacent neuron
-some neurotransmitters increase rate of firing between neurons, others decrease it
-action potential: movement of an electrical impulse along the axon. happens when a chemical process alters electric charge, both inside and outside of the neuron

Neurotransmitters:
Neurotransmitters are brain chemicals that affect cognitive processes and behaviour
-Acetylcholine (ACH): found at synapses between motor neurons and muscle cells, is responsible for movement
-Dopamine: affects arousal, pleasure and voluntary movement. Too much dopamine is thought to be responsible for schizophrenia
-Serotonin: governs sleep, aggression and mood. Low levels of serotonin are associated with depression

Divisions of the nervous system:
-divided into Central Nervous System and Peripheral Nervous System
-The Central Nervous Systen made up of brain and spinal cord. Spinal cord receives and passes messages to and from the brain and connects to nerves in the peripheral nervous system
-The Peripheral Nervous System consists of neurons that send information to and from the central nervous system. Divided into somatic and autonomic nervous system
The somatic nervous system transmits information received by the senses to the central nervous system and to the muscles
The autonomic nervous system is divided into sympathetic and parasympatheric sections. The autonomic nervous system links the central nervous system to internal organs and control basic functions such as breathing and digestion. It cannot be controlled voluntarily.

Localisation of function:
-localisation of function= notion that different areas of the brain have different functions
-human brain has two hemispheres responsible for higher cognitive functions, eg thinking and remembering
-hemispheres joined by the corpus callosum (set of nerve fibres allowing information to be transferred between the two hemispheres
-right hemisphere mostly responsible for the left side of the body and left hemisphere for the right side of the body
-Lateralisation of functions= the way that the two hemispheres have different functions, also reffered to as hemispheric specialisation)
-in right handed people left side of the brain most important for language function, logic and analysis and the right side most importat for non-linguistic processing (eg music and emotion)
Different functions are located in different areas of the cortex:
-Movement is located in the motor cortex to the rear of the frontal lobe----Sensory processing (touch) is located in the somatosensory cortex in the parietal, behind the motor cortex
-Vision is located in the visual cortex in the occipital lobe at the rear of the cortex
-Auditory (sound) processing is located in the left temporal lobe

-Broca's area, to the left of the frontal lobe governs speech production. Damage to it cause speech to be slow and laborious
-Wernicke's area, in the temporal lobe, governs the understanding of speech. Damage to it cause comprehension problems and the person's speech is fluent but meaningless
Studies using brain scans have shown that either Broca's area or Wernicke's area is active when different types of language tasks are performed. eg listening to nouns involves Wernicke's area, thinking of verbs to go in a phrase uses Broca's area

Evaluation:
-Although some functions can be located in certain areas of the brain functions involve many inter-connected areas of the brain. Brain function is holistic
-People with brain damage to a specific area (eg after a stroke) often recover function over time because another area of the brain takes over = brain plasticity

Methods used to identify cortical specialisation:
Post-mortem examinations:
-a post mortem involves surgical dissection of a dead person's brain
-Broca used post mortem examinations to attempt to link visible signs of brain damage with how the people behaved when they were alive
-so discovered that language function was located on left side of the brain (Broca's area)
strengths: -provide an interesting insight into rare cases of brain-damaged individuals
weaknesses: -cannot tell us anything about the functions of a living brain
-process of death may have changed the brain

EEGs:
-EEGs record the electrical activity of areas of the brain using electrodes that are placed on the head
-brain wave patterns coming from the activity of lots of neurons can be seen on a screen
strenghts: -can be used to study normal brain activity (comparison to post mortem)
-have become more sophisticated with computers used to analyse recordings from large numbers of electrodes
-easy to use and not harmful
weaknesses: -generalised measure, so not useful in identifying specific areas of cortical specialisation

Scans:
-PET scans involve injection of radioactive chemical into the bloodstream
-head is then scanned to see the amount of radioactivity coming from different areas of the brain
-amount of radioactivity increases with increased blood flow, showing in which areas the brain is the most active
-can be used to see which parts of the brain are involved in different mental tasks eg reading
-In MRI scans strong magnetic fields and radio waves produce multiple images that combine to give a detailed image of the structure of the brain
-In CAT scans multiple X-rays from different positions around the head are taken
-these are are combined on a computer to produce cross-sectional images of the brain
strengths: -have greatly advanced understanding of brain functions
-can be used with live brain (comparison post mortem)
-more accurate and less invasive than other methods

Autonomic nervous system:
-the autonomic nervous system connects the central nervous system with smooth muscled organs and is part of the peripheral nervous system
-functions (eg increased heart rate) not normally under conscious control
-divided into the sympathetic and parasympathetic sections
-sympathetic section prepares body for action in an emergency or exciting situation- fight or flight
-parasympathetic section brings back the body to the normal state- rest and digest
Sympathetic actions: heart rate increases, pupil dilates, intestine/gut action slows/salvation stops
Parasympathetic actions: heart rate decreases, pupil constricts, intestine/gut action restored, salvation restored

	Created by stellasophie.k over 9 years ago

AS Level Psychology (Unit 1) Note on Biological approach, created by stellasophie.k on 28/03/2015.