Biopsychology

• Nervous system


  Specialised network of cells and is the primary communication system in the body - allows us to function
• Nervous system - functions 


  1. Collect, process and respond to environmental information
  2. Co-ordinate the working of different organs and cells in the body
• Nervous system - Two sub systems

  Central nervous system (CNS)

  Peripheral nervous system (PNS)
• Central nervous system (CNS)


  The CNS is made up of the brain and the spinal cord

  • The brain is central to maintaining life and has many functions including:
  • Basic functions such as regulating body temperature, heart rate and breathing 
  • Language (production and understanding)
  • Co-ordinating movement
  • Coding sensory data from the sensory organs
  • Problem-solving and planning
  • The Spinal Cord ensures that signals from the brain are transmitted to the rest of the body via the PNS
• Peripheral nervous system (PNS)


  Transmits messages throughout the whole body from the brain and also relays messages back to the brain - two sub sections:

  • The somatic nervous system
  • The autonomic nervous system
• Somatic nervous system 


  Transmits and receives messages from the senses

  We can actively control the neurons in this system, meaning that it controls voluntary movements (Raising your arm)
• Autonomic nervous system (ANS)


  We cannot control the neurons in this system meaning that it controls involuntary processes (such as breathing and heart rate)

  Divided into two further sections:

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


  Associated with 'fight or flight' response

  Prepares the body for physical activity

  Can accelerate heart rate, widen bronchial passages
• Parasympathetic system 


  Known as the 'rest and digest' system:

  • Helps to conserve the body's activity levels and energy
  • Regulates bodily functions like digestion and urination
  • Slows heart and breathing rates
  • Relaxation enables the body to go into 'standby'
• Neurons 


  The building blocks of the nervous system: they process and transmit messages through electrical and chemical signals. 80% are located in the brain
• Dendrites 


  Located at the end of neuron and receive signals from neighbouring neurons or from sensory receptors - carry this message towards cell body
• Soma


  Contains the nucleus, which carries genetic code
• Axon


  The impulse (message) is carried along this
• Myelin sheath


  Fatty layer around the axon that prevents messages from getting 'mixed' between neurons, and speeds up the electrical impulses
• Axon terminals 


  At the end of the axon, these allow the neuron to communicate with neighbouring neurons via synaptic transmission
• Nodes of ranvier 


  Gaps in the myelin sheath that allow the electrical impulse to move along the axon faster
• Neuron diagram

  
• Neuron - functions 


  To receive information and send it on. Messages sent along a neuron are known as action potentials, when resting a neuron is negatively charged. When activated by a stimulus, it becomes positively charged, causing the action potential
• Sensory neuron 


  Carry messages from sensory receptors to the central nervous system - convert information from sensory receptors into neural impulses that are passed onto brain or spinal cord (Long dendrites and short axons)
• Relay neurons 


  Connect sensory neurons to the motor neurons, or other relay neurons - allow other neurons to communicate with each other and are found in CNS (short dendrites and short axons)
• Motor neurons 


  Connect the central nervous system to the muscles and glands - located in CNS and project their axons outside of CNS to directly or indirectly control muscles, release neurotransmitters that bind to receptors on muscle to cause movement (short dendrites and long axons)
• Sensory neuron diagram

  
• Motor neuron diagram

  
• Process of synaptic transmission 


  Information is passed down the axon as electrical impulse known as action potential

  Once reaches the end, must cross the synaptic gap between the presynaptic neuron and post-synaptic neuron

  When electrical impulse reaches synaptic vesicles, releases the contents of neurotransmitter - then carry across synaptic gap, then bind to receptor sites on post-synaptic cell
• Excitatory neurotransmitters 


  The post-synaptic neuron is more likely to fire an impulse
• Inhibitory neurotransmitters 


  The post-synaptic neuron is less likely to fire an impulse
• Endocrine system 


  Works with the nervous system to control vital functions, just at a much slower rate. Made up of various glands which produce hormones - these are secreted into the blood stream and affect any cell in the body that has receptors for that hormone
• Hypothalamus 


  Stimulates and controls the release of hormones from the pituitary gland
• Pituitary gland (Master gland)


  Hormones released:

  • ACTH - Stimulates the adrenal cortex and release of cortisol during stress response
  • Oxytocin - Responsible for uterus contractions during childbirth
• Pineal gland 


  Hormone released:

  • Melatonin - Important biological rhythms, including the sleep-wake cycle
• Thyroid gland 


  Hormone released:

  • Thyroxine - Regulating metabolism
• Adrenal gland


  Hormones released:

  Adrenal Medulla - Key hormones in fight or flight

  • Adrenaline
  • Noradrenaline

  Adrenal cortex - release of glucose to provide energy

  • Cortisol
• Ovaries (Female)


  Hormone released:

  • Oestrogen - Controls the regulation of female reproductive system, including menstrual cycle and pregnancy
• Testes (Male)


  Hormone released:

  • Testosterone - Development of male sex characteristics during puberty, while also promoting muscle growth
• Fight or flight response 


  Person enters stressful/dangerous situation

  1. The amygdala is activated -> sends distress signal to hypothalamus
  2. Hypothalamus activates the sympathomedullary pathway (SAM), the pathway running to adrenal medulla and SNS
  3. The SNS stimulates the adrenal medulla
  4. Adrenal medulla secretes adrenaline and noradrenaline
  5. Adrenaline causes a number of physiological changes to prepare for fight or flight
• Physiological changes for fight or flight

  Increased heart rate - increase blood flow to organs

  Increased breathing rate - increase oxygen intake

  Pupil dilation - increase light entry into eye and enhance vision

  Sweat production - regulate temperature

  Reduction of non-essential functions - increase energy for others
• Fight or flight - Evaluation


  Weaknesses:

  • Gray (1988) suggests that it is too limited; initial response is actually to freeze - suggests theory lacks validity
  • Taylor et al (2002) suggests that females adopt a 'tend and befriend' response rather than fight or flight - shows a beta bias to theory
• Localisation of function 


  The theory that different areas of the brain perform different tasks and are involved in different parts of the body
• Phineas Gage 


  Piece of iron went through his skull, Gage survived but experienced a change in personality such as a loss of inhibition and anger - provided evidence to support localisation of function as the area damaged was responsible for personality
• Frontal lobe 


  Responsible for voluntary movements by sending signals to the muscles

  • Expressive language
  • Managing higher level executive functions

  Motor area located here - translates thoughts into physical motions