Biopsych

• Nervous system


  Specialised network of cells and our primary communication system
• Functions of the nervous system


  • Collect, process, and respond to information in the environment
  • Co-ordinate the working of different organs and cells in the body
• Central nervous system (CNS)


  Made up of the brain and the spinal cord
• Brain


  Centre of all conscious awareness
• Cerebral cortex


  Outer layer of the brain, highly developed in humans and distinguishes our higher mental functions from those of animals
• Spinal cord


  Extension of the brain, responsible for reflex actions, passes messages to and from the brain and connects nerves to the peripheral nervous system
• Peripheral nervous system (PNS)


  Transmits messages neurons to and from the CNS
• Divisions of the PNS

  • Autonomic nervous system (ANS)
  • Somatic nervous system (SNS)
• Somatic nervous system (SNS)


  Controls conscious muscle movement and receives information from sensory receptors
• Autonomic nervous system (ANS)


  Governs vital unconscious functions in the body such as breathing, heart rate, digestion, sexual arousal, and stress responses
• Divisions of the ANS


  • Sympathetic nervous system
  • Parasympathetic nervous system
• Sympathetic nervous system


  Involved in responses that prepare the body for fight or flight, increases heart rate, blood pressure, etc.
• Parasympathetic nervous system


  Returns the body to its 'normal' resting state once an emergency (e.g. fight or flight) has passed
• Endocrine system


  Works alongside the nervous system to control vital functions in the body through the action of hormones
• Hormones


  Chemical messages secreted by glands into the bloodstream that affect any cell in the body that has a receptor for that particular hormone
• Pituitary gland


  Major gland located in the brain, called the 'master gland' because it controls the release of hormones from all other glands in the body
• Hypothalamus


  Connected to the pituitary gland and responsible for stimulating/ controlling the release of hormones from the pituitary gland
• Hormones released by the pituitary gland

  • ACTH (from anterior lobe)
  • Oxytocin (from posterior lobe)
• Pineal gland


  Releases melatonin, responsible for important biological rhythms such as the sleep-wake cycle
• Thyroid gland


  Releases thyroxine, responsible for regulating metabolism
• Effects of thyroid gland dysfunction

  • Over-active thyroid = fast metabolism
  • Under-active thyroid = slow metabolism
• Adrenal gland


  • Adrenal medulla (releases adrenaline and noradrenaline)
  • Adrenal cortex (releases cortisol)
• Testes


  Release androgens, including testosterone, responsible for the development of male sex characteristics, sex drive, sperm production, and increase/maintenance of muscular strength
• Ovaries


  Release oestrogen, which controls the regulation of the female reproductive system, including the menstrual cycle and pregnancy
• Endocrine system and ANS response to stress


  1. Stressor is perceived, hypothalamus triggers sympathetic branch of ANS

  2. Adrenaline is released from the adrenal medulla into the bloodstream

  3. Adrenaline triggers physiological changes (fight-or-flight response)

  4. Once the threat has passed, parasympathetic nervous system returns to resting state
• Dendrites


  Receive signals from other neurons or from sensory receptor cells
• Cell body


  Contains the nucleus which holds the genetic information
• Axon


  A long slender fibre that carries nerve impulses, in the form of action potential
• Myelin sheath


  Insulates the axon so that action potentials travel faster along the axon
• Axon terminal


  Connects the neuron to other neurons (or directly to organs)
• Types of neuron


  • Sensory neuron
  • Relay neuron
  • Motor neuron
• Synaptic transmission


  1. Information is passed down the axon as an action potential

  2. Synaptic vesicles release neurotransmitters into the synaptic cleft

  3. Neurotransmitters diffuse across the synaptic gap and bind to receptor sites on the post-synaptic membrane

  4. Receptors on the post-synaptic neuron produce excitatory or inhibitory effects
• Summation


  The sum / net effect of the excitatory and inhibitory influences on the post-synaptic neuron
• Uni-directional


  Communication is one-sided, as neurotransmitters diffuse from a high concentration to a low concentration
• Reuptake


  Neurotransmitters diffuse back into the pre-synaptic neuron after being released from post-synaptic receptor, preparing the cell to fire again
• Fight-or-flight response


  1. Amygdala is activated, sending distress signal to hypothalamus

  2. Hypothalamus activates the Sympathomedullary pathway, stimulating the adrenal medulla

  3. Adrenal medulla secretes adrenaline and noradrenaline into the bloodstream

  4. Adrenaline causes physiological changes to prepare the body for fight or flight

  5. When the threat has passed, the parasympathetic nervous system dampens down the stress response
• Response to chronic stressors

  1. Hypothalamus activates the HPA axis (hypothalamus, pituitary gland, adrenal glands)

  2. Hypothalamus releases CRH

  3. CRH causes pituitary gland to release ACTH

  4. ACTH stimulates adrenal cortex to release cortisol
• Localisation of function


  Certain functions (e.g. language, memory) have certain locations within the brain
• Localised brain regions


  • Motor area
  • Somatosensory area
  • Visual area
  • Auditory area
  • Broca's area
  • Wernicke's area
• Hemispheric lateralisation


  Each hemisphere/side of the brain is specialised to perform different functions