psych units 1 & 2

• Brain


  The body's master information-processing and decision-making organ
• Brain


  • Receives and interprets information from the sensory systems and sends motor messages out to all parts of the body so that a co-ordinated and an appropriate response can be made
  • Encased in a hard skull
  • Weighs around 1.5 kg
  • Contains billions of neurons and trillions of connections between neurons
  • Consists of two halves
  • Has a convoluted (folded) outer surface
• Spinal cord


  A complex cable or tract of nerve fibres stretching from the base of the brain to the lower back
• Spinal cord


  • Connects the brain to other parts of the body via its connection to the peripheral nervous system
  • Receives sensory information from the Peripheral Nervous System (PNS) and transmits it to the brain
  • Transmits motor messages from the brain to the PNS
  • If there is damage to a section, it may mean that motor messages can no longer reach muscles in the body and sensations from these muscles will not be registered
• Neuron


  The structure that determines whether the neuron will be activated and thus transmit (send) messages to other neurons
• Neuron


  • Dendrite: a short, thin, widely branching nerve fibre that is specialised to detect and receive neural information
  • Axon: a single, tube like, fluid-filled extension that transmits messages from the soma to other cells
  • Axon is encased in a white fatty substance called myelin sheath that helps speed up transmission
  • At the end of each axon are branches called axon terminals, each with a small knob-like swelling called a terminal button / synaptic knob
  • The synaptic knob stores chemicals called neurotransmitters which assist in the transmission of neural information from one neuron to another
• The brain-heart debate considers whether our thoughts, feelings and behaviours originate from our brain or our heart
• Aristotle's beliefs


  Mental processes were located in and around the heart
• Several Greek physicians supported the brain hypothesis after dissecting animal bodies
• Galen observed that injuries to the head and brain affected behaviour, while heart injuries did not
• Mind-body problem


  The extent to which the mind and the body are the same or separate things
• Dualism


  The mind and the body are separate entities, one physical and one non-physical, which are linked through two-way interactions
• Phrenology


  The (now discredited) study of the shape of the skull as an indicator of the extent of one's mental faculties and character traits
• Phrenology


  • Franz Joseph Gall believed the size of each part of the cerebral cortex was determined by mental faculties, traits and personality, and this in turn influenced the contours of the skull
  • Gall developed a system of 27 'faculties,' each of which he believed belonged to a different region of the head
• Phrenology has been discounted, but Gall's idea that different parts of the brain play a significant role in different functions is accurate
• Ablation


  A surgical procedure in which parts of the brain are removed or destroyed
• Pierre Flourens performed brain ablation on animals and demonstrated that resulting loss of movement could be recovered over time
• Electrical stimulation of the brain (ESB)


  Used to study brain function, by stimulating different sections and recording activity in these sections via a probe delivering a weak electrical signal
• Wilder Penfield used electrodes to study epilepsy and created 'brain maps' (sensory and motor homunculus) which link brain areas to functions and are still used today
• Neuroimaging techniques


  A range of techniques developed to capture images of the brain
• Computerised tomography (CT)


  • Combines x-ray images taken from different angles to create cross-sectional images
  • The patient is usually injected with a contrast
  • Extremely useful for showing damage or abnormalities in brain structures, soft tissues (including tumours) are revealed more clearly than on an X-ray, adjacent slices can be combined to form a 3D image
  • Does not provide information about functioning of the brain, Involves the use of a powerful x-ray, so cannot be repeated within several months or used on pregnant people, Clarity of image is not as good as an MRI image, Considered slightly invasive (due to the injection of the contrast)
• Magnetic resonance imaging (MRI)


  • Uses magnetic fields to activate atoms in the brain, which allows a computer to generate an image
  • Allows for precise location of structural damage in the brain, Non-invasive (no injections, radioactivity or X-rays), Provides a photographic quality image (much clearer than CT), Can provide both several views (horizontal, vertical and sideways)
  • Cannot be used on people with internal metallic devices (pacemakers), Requires the patient to remain very still as even small movements may produce 'ghosting' (shadows on the scan), Cannot be used on 'uncooperative' or claustrophobic patients
• Positron emission tomography (PET)


  • Allows colour imaging of brain activity while the patient engages in an activity, A colour code is used to indicate high and low brain activity
  • Provides detailed information about the functioning of the brain (or the brain 'at work), Researchers can establish which brain areas are active while a participant completes a certain task, Can be used on healthy participants
  • Mildly invasive due to the injection of a radioactive substance (even though this considered to be harmless), Use of radioactive agent means that there can only be limited number of scans on an individual subject, Images do not provide clear structural information, Radioactivity decays rapidly so tasks under investigation must be short, Long delay between scans (40 seconds) so it doesn't pick up the rapid progression of activity in the brain
• Functional magnetic resonance imaging (fMRI)


  • Measures oxygen consumption with the assumption that active areas of the brain contain more oxygenated blood, This is a preferred imaging technique in research due to its safety and accuracy
  • It does not involve radiation and can be performed multiple times, It shows areas of high activity in colour
  • It is very expensive, not as readily available
• Hindbrain


  Located in the lower back of the brain, Involved in supporting vital bodily processes (e.g., breathing and sleep)
• Hindbrain


  • Consists of the cerebellum, medulla oblongata and pons
  • The cerebellum coordinates fine muscle movements and regulates posture and balance, The medulla oblongata controls vital bodily functions such as swallowing, breathing, heart rate, blood pressure, vomiting, salivating, coughing and sneezing, The pons is involved in sleep, dreaming and arousal from sleep ('waking') and coordination of some muscle movements
• Midbrain


  The centre of the brain which sits at the topmost part of the brainstem, Connects the upper and lower areas of the brain, Involved in auditory and visual processing and plays a role in motor control, pain inhibition and reward-based learning patterns
• Midbrain


  • Consists of the substantia nigra and reticular formation
  • The substantia nigra is a collection of neurons producing dopamine, a neurotransmitter involved in movement and coordination, The reticular formation plays a role in maintaining arousal, consciousness and motor control, contains the reticular activating system (RAS), which causes alertness and awakening when stimulated
• Forebrain


  The largest region of the brain, Involved in several bodily functions, and learning, memory, thinking and perception
• Forebrain


  • Consists of the cerebrum, thalamus, hypothalamus, pineal gland and limbic system
  • The hypothalamus is involved in connecting the hormonal and nervous systems via the pituitary gland, regulates hormones involved in maintaining homeostasis
  • The thalamus relays information to the relevant sections of the cerebral cortex for further processing, particularly sensory information, connects with the reticular formation and RAS system, and regulates arousal
  • The cerebrum is responsible for directing conscious motor activities and receiving and processing sensory information
  • The cerebral cortex is a thin layer that covers the cerebrum and is extensively folded, specific areas are dedicated to specific function (localisation of function), most areas perform a wide array of functions, it is extensively connected to the subcortical areas below it, function is typically divided into sensory, motor and association areas
• Cerebral hemispheres


  • Perform both similar and unique functions, Each hemisphere controls motor and sensory functions on the opposite side (contralateral organisation), Hemispheric specialisations are functions performed by one side and not the other, Left side: analytical processing, language, rational thought and logic, Right side: spatial and visual thinking, emotion, creativity, imagination
• Cortical lobes


  The cerebral cortex is divided into four pairs of cortical lobes (four in each hemisphere: the frontal, parietal, temporal and occipital lobes)
• Cerebral cortex


  • Specific areas are dedicated to specific function (localisation of function)
  • Most areas perform a wide array of functions
  • Extensively connected to the subcortical areas below it
• Functions of the cerebral cortex


  • Sensory
  • Motor
  • Association
• Sensory areas


  Receive and process sensory information
• Motor areas


  Initiate voluntary movement
• Association areas


  Integrate information from multiple brain regions, facilitating complex processes such as language, creativity and decision-making
• The cerebral hemispheres perform both similar and unique functions
• Contralateral organisation


  Each hemisphere controls motor and sensory functions on the opposite side
• Hemispheric specialisations


  • Left side: analytical processing, language, rational thought and logic
  • Right side: spatial and visual thinking, emotion, creativity, imagination