Biop

• Nervous system


  Made up of the brain and the spinal cord
• function of Peripheral nervous system (PNS)?

  Relays(sends) messages from the environment to the CNS, via sensory neurones, and from the CNS to effectors, via motor neurones
• Subdivisions of the PNS

  • Autonomic nervous system
  • Somatic nervous system
• Autonomic nervous system


  Controls involuntary, vital functions of the body, such as maintaining heart rates and breathing rates
• Somatic nervous system


  Receives information from sensory receptors belonging to each of the 5 senses, and results in effectors being stimulated by the CNS, via motor neurones

  
• Branches of the autonomic nervous system


  • Sympathetic
  • Parasympathetic
• Sympathetic and parasympathetic nervous systems

  Work as part of an antagonistic pair during the 'rest and digest' response, and are crucial in producing the physiological arousal needed to maintain the fight or flight response
• Sympathetic nervous system


  Increases heart rates, breathing rate, causes vasoconstriction and pupil dilation
• Parasympathetic nervous system


  Decreases heart rate, breathing rates, causes vasodilation and pupil constriction
• Endocrine system


  The main chemical messenger system of the body, where hormones are secreted into the bloodstream from glands, and then are transported towards target cells in the blood, with complementary receptors
• Pituitary gland


  Considered to be the 'master' gland because it controls the release of hormones from all other glands in the body
• Thyroid


  Releases the hormone thyroxine, which increases heart rate and therefore increases the rate of growth
• Adrenal gland


  Releases adrenaline which creates the physiological arousal preceding(before) the fight or flight response, through increasing the activity within the sympathetic branch of the nervous system
• Fight or flight response

  1. The body senses and becomes aware of a stressor in the environment

  2. Through sensory receptors and sensory neurones in the PNS, this information is sent to the hypothalamus in the brain which coordinates a response and triggers increased levels of activity in the sympathetic branch of the ANS

  3. Adrenaline is released from the adrenal medulla in the adrenal glands, and is transported to target effectors, via the blood and through the action of the endocrine system

  4. This results in the rectum contracting, saliva production being inhibited and a greater breathing rate

  5. Once the stressor is no longer a threat, the hypothalamus triggers less activity in the sympathetic branch and more activity in the parasympathetic branch of the ANS
• Synaptic transmission


  A method of neurons communicating with each other, relaying information to the CNS across sensory neurons and carrying out responses dictated by the brain through sending information to effectors via motor neurons
• Synaptic transmission


  1. An action potential arrives at the presynaptic membrane, causing depolarisation through the opening of voltage-dependent calcium ion channels, and the consequent influx of calcium ions

  2. The increased concentration of calcium ions within the membrane causes the vesicles, containing neurotransmitter, to fuse with the presynaptic membrane and release their contents into the synaptic cleft through exocytosis

  3. The neurotransmitter diffuses across the synaptic cleft, down a concentration gradient, and binds to complementary receptors on the post-synaptic membrane

  4. The resultant action potential will then be transmitted along the axon of the following neuron, resulting in a 'cascade' of neurotransmission
• Inhibitory neurotransmitters


  Reduce the potential difference across the postsynaptic membrane through the closure of the voltage-dependent sodium ion channels, reducing the likelihood that an action potential will be generated
• Excitatory neurotransmitters


  Increase the potential difference across the postsynaptic membrane through triggering the opening of more voltage-dependent sodium ion channels, increasing the likelihood that an action potential will be generated
• Localisation theory


  Certain areas of the brain are responsible for certain processes, behaviours and activities

  
• Motor area


  Separated from the auditory area by the central suclus and found in the frontal lobe, this area is involved in regulating and coordinating movements

  
• Auditory area


  An area of the temporal lobe, located on the superior temporal gyrus, which is responsible for processing auditory information and speech
• Visual area


  An area in the occipital lobe which is responsible for processing visual information
• Somatosensory area


  An area of the parietal lobe which processes information associated with the senses e.g. touch, heat, pressure etc.

  
• Wernicke's Area


  Responsible for speech comprehension and located in the temporal lobe (the left temporal lobe for most people)
• Broca's Area


  Responsible for speech production and located in the frontal lobe, usually in the left hemisphere
• The left hemisphere of the brain is associated with language production and comprehension
• Supporting evidence for localisation of brain function

  • Tulving et al demonstrated, using PET scans, that semantic memories were recalled from the left prefrontal cortex, whilst episodic memories were recalled from the right prefrontal cortex
  • Petersen et al (1988) found that Wernicke's area activation is required for listening tasks, whereas Broca's area is required for reading tasks

  
• Supporting Case Studies


  • Phineas Gage was injured by a blasting rod which intersected the left side of his face, tearing through his prefrontal cortex
• Holistic view of brain function

  Each function requires several brain areas to be activated and these functions are not restricted to these areas

  
• After removing 20-50% of the cortices belonging to rats, found that no specific brain area or lesion was associated with learning how to traverse through a maze
• Evidence supporting the link between certain brain areas and symptoms of OCD

  • Dougherty et al (2002) studied 44 OCD sufferers who'd undergone lesioning of the cingulate gyrus (cingulotomy) in order to control their symptoms

  
• Plasticity


  The brain's ability to physically and functionally adapt and change in response trauma, new experiences and learning
• The idea of plasticity opposes the previous theory that there is a 'critical window' for synaptic and neuronal connection formation, which occurred during the first 3 years of life, after which no new neuronal connections would be formed
• Synaptic pruning


  The process by which extra neurons and synaptic connections are eliminated in order to increase the efficiency of neuronal transmissions
• Functional recovery


  The ability of the brain to transfer the functions of areas damaged through trauma, to other healthy parts of the brain, thus allowing for normal functioning to carry on
• Law of equipotentiality


  Secondary neural circuits surrounding the damaged area become activated
• Axonal sprouting


  Formation of new synapses and strengthening of axonal connections between damaged and healthy areas
• Haemodynamic response


  Activated areas experience a higher blood deoxygenation level
• Phantom limb syndrome


  Caused by the sensory input from the face skin 'invading' and activating deafferented hand zones in the cortex and thalamus
• Jodi Miller


  • Her entire left hemisphere was removed in an attempt to control her epileptic seizures, but through the mechanisms of neuroplasticity, she was still able to control the right side of her body through the use of cerebral spinal fluid