brain and neuropsychology

• Nervous system


  • A specialised network of cells in the human body
  • Our primary communication system
• Nervous system


  • It has two functions:
  • To collect, process and respond to information in the environment
  • To co-ordinate the working of different organs and cells in the body
• Nervous system sub-systems


  • The central nervous system
  • The peripheral nervous system
• Central nervous system (CNS)


  Made up of the brain and the spinal cord
• Brain


  • Is the centre of all conscious awareness. Where all decisions take place
  • The brain has two hemispheres. The left hemisphere controls the right side of the body and the right hemisphere controls the left side of the body
  • At the base of the brain is the brain stem. The function of the brain stem is to control basic functions such as controlling autonomic activity
• Spinal cord


  • An extension of the brain
  • Carries incoming and outgoing messages between the brain and rest of the body
  • Responsible for reflex actions such as pulling hand away from a hot plate
• Peripheral nervous system (PNS)

  Transmits messages via millions of neurons (nerve cells) to and from the CNS
• PNS sub-divisions


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


  • Governs vital functions in the body such as breathing, heart rate, sexual arousal, digestion and stress response
  • Has two main divisions: sympathetic and parasympathetic nervous system
  • Involuntary
  • Has only motor pathways
• Somatic nervous system (SNS)


  • Controls muscle movement
  • Receives information from sensory receptors
  • Under conscious control
  • Has sensory and motor pathways
• Nervous system components


  • Peripheral nervous system (PNS)
  • Central nervous system (CNS)
  • Autonomic nervous system (ANS)
  • Somatic nervous system (SNS)
  • Brain
  • Spinal cord
• Autonomic (automatic)


  Involuntary processes e.g. breathing and heart rate
• Somatic


  Voluntary such as moving your arm (muscle movement)
• Autonomic nervous system divisions


  • Sympathetic branch
  • Parasympathetic branch
• Homeostasis


  The process by which the body maintains a constant and balanced internal state
• Homeostasis examples


  • Maintenance of constant body temperature: 37 degrees centigrade
  • Control in the concentration of carbon dioxide
• Autonomic nervous system


  Deals with involuntary responses
• Autonomic nervous system divisions


  • Sympathetic nervous system: a state of arousal
  • Parasympathetic nervous system: rest and digest response/ resting state
• Flight or fight response

  1. When a stressor is perceived, the hypothalamus triggers activity in the sympathetic branch of the autonomic nervous system, this moves us from resting state (para-sympathetic) to arousal (sympathetic)

  2. The stress hormone, adrenaline, is then released from the adrenal medulla (a part of the adrenal gland) into the blood stream

  3. This triggers physiological changes in the body (e.g. increased heart rate). At this stage, we either run away or fight and tackle the situation

  4. Finally once the threat has passed, the parasympathetic nervous system returns the body to resting state
• Sympathetic state


  • Increase heart rate
  • Increase breathing rate
  • Pupils dilate
  • Inhibits digestion
  • Inhibits saliva production
  • Contracts rectum
• Parasympathetic state


  • Decrease heart rate
  • Decrease breathing rate
  • Pupils constrict
  • Stimulates digestion
  • Stimulates saliva production
  • Relaxes rectum
• Adrenaline


  To prepare the body for action, fight or flight
• Adrenaline effects


  • Increases blood to brain and skeletal muscle. This will increase blood supply/oxygen, to skeletal muscle for physical action
  • Increases respiration. This will increase oxygen to brain for rapid response planning
• James-Lang theory of emotion

  EVENT – AROUSAL – INTERPRETATION - EMOTION
• James-Lang theory of emotion

  1. A particular event (a stressor in the environment) activates the hypothalamus which instructs the sympathetic division of the ANS

  2. This leads to the release of adrenaline from the adrenal glands creating physiological arousal. This arousal is experience as an increase in bodily activity such as a faster heart rate and increased blood pressure

  3. The theory says it is then up to the brain to interpret these physiological changes

  4. The result of this interpretation is an emotion. Which might be a sense of fear, excitement, even love
• If there are no physiological changes in the body or these are not noticed, no emotion will be experienced
• Real life examples of James-Lang theory

  • Emotional states seem to follow physiological arousal in cases such as phobias or panic disorders. For instance, a person may trip and fall down in public which leads to an emotional reaction such as anxiety or embarrassment. This then leads to them avoiding public situations as an association has been formed between the situation and the emotion
• The Cannon-Bard theory argues that we experience emotion at the same time as physiological arousal (they are simultaneous) and not one after the other
• Neurons


  Nerve cells that process and transmit messages through electrical and chemical signals
• Structure of a neuron

  • Cell Body: includes nucleus which contains genetic material of a cell
  • Dendrites: protrude from cell body these carry nerve impulses from neighboring neurons towards cell body
  • Axon: carries impulses away from cell body
  • Myelin Sheath: fatty layer that protects axon and speeds up electrical transmission down the axon
  • Nodes of Ranvier: speed up transmission by forcing the impulse to jump across the gaps along the axon
• Types of neurons


  • Motor neuron: these connect the CNS to effectors such as muscles and glands. They have short dendrites and long axons
  • Sensory neuron: these carry messages from the PNS to the CNS. They have long dendrites and short axons
  • Relay neuron: these connect the sensory neurons to the motor or other relay neurons. They have short dendrites and short axons
• Electrical transmission


  • When a neuron is in a resting state, the inside of the cell is negatively charged compared to the outside
  • When a neuron fires, the electrical charge of the cell changes for a split second causing an action potential – the neuron fires
  • This creates the electrical signal (impulse) that travels down the axon to the end of the neuron
• Synaptic transmission


  The process by which neighbouring neurons communicate with each other by sending chemical messages across the gap (synaptic cleft) that separates them
• Chemical transmission


  1. Messages are passed down the neuron electrically, when they reach the end of the neuron they are passed across the synapse chemically

  2. When an electrical signal has reached the end of a neuron, it arrives at the terminal buttons. Here there are tiny sacs called vesicles which contain neurotransmitters. The electrical signal causes the vesicles to release neurotransmitters. These travel across the synaptic cleft to the next neuron

  3. The neurotransmitter then attached to the postsynaptic receptor sites. These are located on the dendrites of the next neuron. Here the chemical message is turned back into an electrical impulse which sets off again down the neuron

  4. The chemical neurotransmitter left in the gap is broken down by enzymes an reabsorbed by the presynaptic neuron so it can be used again
• Excitation and inhibition


  • Neurotransmitters have either an excitatory or inhibitory effect on the neighboring neuron
  • Inhibition results in the post synaptic neuron becoming negatively charged and less likely to fire
  • Excitation results in the post synaptic neuron by increasing its positive charge therefore making it more likely to fire e.g. adrenaline
• GABA


  A neurotransmitter that crosses the synapse and creates a negative charge in the post synaptic neuron, has an inhibitory effect
• Summation


  • At any one time, a neuron may receive thousands of signals from other neurons within a network. Some of these will be excitatory and some inhibitory
  • If there are enough excitatory signals compared to inhibitory signals then summation occurs
  • This will cause the neuron to fire and an electrical impulse will be created
• Hebb's theory of learning and neuronal growth


  • Hebb attempted to use ideas from psychology and biology to explain mental processes
  • He suggests that when we learn, this creates new connections between neurons in the brain
• Brain plasticity


  • What happens to synaptic connections in the brain that are use frequently? They become stronger the more we use them
  • This suggests that the brain is not fixed in structure, but that it is constantly changing and developing
  • The brain can adapt, change structure and form new connections as we learn. This can happen at any time, any age and it does not matter what we are learning (anything new will do it)
• Engram


  The trace that learning leaves in the brain can be permeant