biopsychology

• The Central Nervous System (CNS) consists of the brain and spinal cord. The spinal cord is an extension of the brain. It passes messages to and from the brain and connects nerves to the PNS. This processes, interprets and stores information and issues orders to muscles, glands and organs
• The PNS transmits messages, via millions of neurons (nerve cells) to and from the central nervous system. The peripheral nervous system is further sub-divided into two groups AUTONOMIC AND SOMANTIC NERVOUS SYSTEM  
• Autonomic Nervous system governs vital functions in the body such as breathing, heart rate, digestion, sexual arousal and stress response. The organs controlled by the autonomic nervous system include the heart, lungs, eyes, stomach, and the blood vessels of the internal organs. It can be divided into the sympathetic and parasympathetic nervous system
• Somatic nervous system (SNS) consists of nerves carrying sensory signals from all over the body e.g. eyes, ears, skeletal muscles, and the skin to the CNS. It also contains the nerves that carry the messages from the brain to the other areas of the body. It controls muscle movement and receives information from sensory receptors. 
• neurons involved in a reflex arc - sensory , relay , motor
• Excitatory neurotransmitters are those that increase the chance of adjacent neurons firing, whereas inhibitory neurotransmitters decrease the chance of adjacent neurons firing.  
• Sensory neurons: They are found in receptors such as the eyes, ears, tongue and skin, and carry nerve impulses to the spinal cord and brain. When these nerve impulses reach the brain, they are translated into ‘sensations’, such as vision, hearing, taste and touch. However, not all sensory neurons reach the brain, as some neurons stop at the spinal cord, allowing for quick reflex actions. 
• Relay neurons: They are found between sensory input and motor output/response neurons. Relay neurons are found in the brain and spinal cord and allow sensory and motor neurons to communicate. 
• motor neurons: They are found in the central nervous system (CNS) and control muscle movements. When motor neurons are stimulated, they release neurotransmitters that bind to the receptors on 

   muscles to trigger a response, which lead to movement. 
• • The junction where two neurones meet is known as a synapse. 
  • A synapse consists of a presynaptic knob, synaptic cleft and postsynaptic membrane.  
  • Synapses that use acetylcholine (ACh) as a neurotransmitter are described as cholinergic synapses. 
• Electrical impulses cannot 'jump' across synapses
• Electrical impulse arriving at the end of the axon on the presynaptic neurone

  1. Chemical messengers (neurotransmitters) released from vesicles at the presynaptic membrane

  2. Neurotransmitters diffuse across the synaptic cleft

  3. Neurotransmitters temporarily bind with receptor molecules on the postsynaptic membrane

  4. Postsynaptic neurone generates an electrical impulse that travels down the axon

  5. Neurotransmitters destroyed or recycled to prevent continued stimulation of the second neurone
• Continued stimulation of the second neurone could cause repeated impulses to be sent
• Our sympathetic nervous system immediately prepares us for action (fight or flight). This system is designed to deal immediately with short-lived stress, by channelling resources into the areas of the body where they are needed and diverting resources from areas not needed. During situations that creates stress, fear or excitement, the neurones of the sympathetic nervous system will stimulate the adrenal medulla (of the adrenal gland) to secrete adrenaline. 
• once the threat has passed, the parasympathetic nervous system returns the body to its resting state. The parasympathetic branch of the ANS works in opposition to the sympathetic division. This acts as a ‘brake’ and reduces the activities of the body that were increased by the actions of the sympathetic branch. This is sometimes referred to as the rest and digest response. 
• Localisation: the theory that specific areas of the brain are associated with physical and psychological functions. 
• lateralisation: the dominance of one hemisphere of the brain for physical and psychological functions 
• • Localisation of brain function is where certain functions (memory, speech, language) have specific locations in the brain. 
  • The brain is split into two hemispheres, right and left hemisphere. 
  • The two hemispheres are connected by the corpus callosum, which acts as a bridge between the two hemispheres and allows them to send messages and work together.  
  • Each hemisphere has 4  brain lobes. 
• Frontal Lobe:  

  • Motor control (premotor cortex)  
  • Problem solving (prefrontal area) 
  • Speech production (Broca's area)  
• Temporal Lobe:  

  • Auditory processing 
  • Language comprehension (Wernicke's area)  
  • Memory/information retrieval  
• Parietal Lobe: 

  • Touch perception (somatosensory cortex) 
  • Body orientation  
  • Sensory input  
• Occipital Lobe: 

  • Sight (visual cortex) 
  • Visual reception and interpretation  
• Motor cortex – (FRONTAL) 

  • This is located at the back of the frontal lobe. The motor cortex is responsible for the generation of voluntary motor movements. Both hemispheres have a motor cortex, with the right hemisphere being responsible for the left side of the body’s movement and the left hemisphere being responsible for the right. 
• Auditory Centre- (TEMPEROL)  

  • Is concerned with hearing. Located in the temporal lobe in both hemispheres. The auditory pathway begins in the cochlea where soundwaves are converted to nerve impulses which travel via the auditory nerve to the auditory cortex.   
  • Cochlea-Brainstem (basic decoding e.g. duration and intensity) 
  • Thalamus (relay station/further decoding) 
  • Auditory cortex (recognition of and response to sound). 
•  Somatosensory Cortex- (PARIETAL)  

  • This is located in the parietal lobe, close to the motor area. Both hemispheres have a somatosensory cortex, with each hemisphere receiving sensory information from the opposite side of the body. This detects sensory events arising from different regions of the body. Using information from the skin, the somatosensory cortex produces sensations of touch, pressure, pain and temperature, which it then localises to specific body regions. 
• Visual Centre- (OCCUPITAL)  

  • The primary visual centre is the visual cortex in the occipital lobe. The visual cortex spans both hemispheres, with each hemisphere receiving information from the visual field of the opposite side.  Processing begins in the retina and then information is sent to the brain via the optic nerve. Most information then travels to the thalamus, which acts as a relay station, passing this information on to the visual cortex. The visual cortex contains different areas for colour, shape etc. 
• The brain is split into two equal symmetrical parts, the right and left hemispheres. The brain is contralateral. 
• Hemispheric lateralisation is the division of functions between the two hemispheres. 
• Left Hemisphere  

  • The left hemisphere for most people is where they process language.  
  • Broca and Wernicke's areas are found in the left hemisphere. 
  • If someone has a stroke in the left hemisphere, their speech will likely be affected. 
• Right Hemisphere  

  • Dominant in recognising emotions in others. 
  • Spatial information
• evaluation of localisation 


  higher cognitive functions may not be localised - Karl Lashley (1950) investigated rats ability to learn a maze and found that the basic motor and sensory functions were localised, but that higher mental functions were not. He found the effects of deliberate damage to between 10% and 50% of the rat’s cortex was determined by the extent, rather than the location, of the damage.  

  The more cortex he removed, the more the rat’s ability to learn the maze was affected. 
• evaluation of localisation 


  Research suggests that what might be more important is how brain areas communicate with each other, rather than which specific brain regions control a particular process. 

  Dejerine reported a case in which the ability to read was lost through damage to the connection between the visual cortex and Wernicke’s area.   Complex behaviours move through different structures before a response is produced. 

  Damage to the connection between any 2 points results in impairments that resemble damage to the localised brain region associated with a specific function. 

   
• evaluation of localisation 


  support for language studies from aphasia - Expressive (Broca’s) aphasia is an impaired ability to produce language. In most cases, this is produced by damage to Broca’s area.  

  Receptive (Wernicke’s) aphasia is an impaired ability to understand language. This is usually the result of damage to Wernicke’s area (e.g. from a stroke).  

  These findings demonstrate the importance of these brain regions in the production and comprehension of language. 
• evaluation of localisation 


  brain scans - For example, Petersen et al (1988) used brain scans to demonstrate how Wernicke’s area was active during a listening task and Broca’s area was active during a reading task. This suggests these areas have different functions, supporting the notion of localisation of function. 

   
• Localisation


  The idea that specific mental functions are located in specific regions of the brain
• Neurological evidence from psychosurgery

  • Dougherty (2002) reported on 44 OCD patients who had undergone cingulotomy (lesioning the cingulate gyrus)
  • Follow-up at 32 weeks showed a third had met the criteria for successful response to surgery and 14% for partial response
• Neurological evidence from psychosurgery


  Suggests that symptoms and behaviours associated with serious mental disorders are localised
• evaluation - Over half of patients experienced no improvement from psychosurgery
• This suggests that other factors may be involved and that localisation of function is an oversimplistic approach
• Lateralisation is the idea that the two halves of the brain are functionally different, and that each hemisphere has functional specialisations