Biopsychology

• Nervous system


  Consists of the CNS and the PNS, communicates using electrical signals. It is a specialised network of cells and is our primary internal communication system. Controls movement, thoughts, memory without thinking such as breathing, blinking, blushing.
• Neurons


  Specialised cells that send signals all over the body helping limbs feel sensations like pain.
• Main functions of the nervous system


  • To collect, process and respond to information in the environment
  • To co-ordinate the working of different organs and cells in the body
• Subunits of the nervous system


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


  Brain and spinal cord
• Function of the CNS


  The origin of all complex commands and decisions
• Brain


  The centre of all conscious awareness. The brain's outer layer, the cerebral cortex, is only 3mm thick and is only found in mammals. It is highly developed in humans and is what distinguishes our higher mental functions from other animals. The connection between the brain and spinal cord allows for messages to be passed from the brain to the body, the body is then able to respond.
• Cerebral cortex


  Wrinkly outermost layer surrounding the brain. Relates to human traits including higher thought, language and human consciousness as well as the ability to think, reason and imagine. Further divided into 4 sections
• Lobes of the cerebral cortex


  • Frontal lobe associated with reasoning, planning, parts of speech, movement, emotions and problem solving
  • Parietal lobe associated with movement, orientations, recognition, perception of stimuli
  • Occipital lobe associated with perception and recognition of auditory stimuli, memory and speech
• Spinal cord


  An extension of the brain. It passes messages to and from the brain and connects nerves to the PNS. It is also responsible for reflex actions such as pulling your hand away from a hot plate.
• Peripheral nervous system (PNS)


  Outside the CNS made up of nerves and ganglia that send and receive signals from the CNS. It transmits messages via millions of neurons, further divided into the ANS and SNS
• Somatic nervous system


  Controls body movements under our control (volunatry), transmits information from receptor cells in the sense organs to the CNS and receives information from the CNS that directs muscles to act. Maintains communication between the CNS and outside world.
• Autonomic nervous system (ANS)


  Controls involuntary functions that our body does on its own. Transmits information to and from the internal bodily organs. It has two main divisions: the sympathetic and parasympathetic nervous systems.
• Sympathetic nervous system


  The response to a perceived threat and is responsible for fight or flight. Pupils dilate, heart beat increases, digestion and bladder is constricted.
• Parasympathetic nervous system


  Controls homeostasis, "rest and digest" function. Pupils constrict, heart rate decreases, digestion and bladder is continuous.
• Endocrine system


  Works with the nervous system to maintain homeostasis and control vital functions in the body. It acts more slowly than the nervous system but has a very widespread and powerful effect. Various glands produce hormones which are secreted into the bloodstream and affect any cell in the body that has a receptor for that hormone.
• How the endocrine system works with the nervous system


  The PNS collects information regarding the stage of the body. If there is something wrong, a signal is sent to the CNS to make a decision. Signal is then sent to a major endocrine gland to secrete relevant hormones to restore homeostasis.
• Glands


  Organs that secrete hormones
• Pituitary gland


  Located in the brain, called the master gland because it controls the release of hormones from all the other endocrine glands in the body
• Other main glands in the endocrine system


  • Hypothalamus
  • Pituitary
  • Thyroid
  • Parathyroid
  • Adrenal
  • Pancreas
  • Ovaries
  • Testes
• Thyroid gland


  Releases thyroxine which affects cells in the heart and throughout the body which affects metabolic rates, in turn affects growth rates.
• How fight or flight comes about with the nervous system and endocrine system

  Endocrine and ANS work in parallel during a stressful event. The hypothalamus activates the pituitary gland and this triggers activity in the sympathetic branch of the ANS. ANS changes from parasympathetic state to the physiologically aroused sympathetic state. Adrenaline is released from the adrenal medulla into the bloodstream. This triggers physiological changes in the body which creates physiological arousal necessary for fight or flight. This response is immediate and automatic. There is an increased heart rate, breathing rate, pupils dilate, inhibits digestion, saliva production and contracts the rectum. Once the threat has passed, the parasympathetic nervous system returns the body to its resting state. The actions of the parasympathetic are antagonistic to the sympathetic nervous system.
• Neurons


  Basic building blocks of the nervous system, they are nerve cells that process and transmit messages through electrical and chemical signals. There are 100 billion in the humans nervous system, 80% of which are located in the brain.
• Structure of a neuron


  Cell body includes a nucleus and dendrites. The axon contains myelin sheath and Node of Ranvier. Axon terminal includes terminal buttons.
• Dendrites


  Receive signals from other neurons or from sensory receptor cells, typically connected to the cell body.
• Axon


  A long slender fibre that carries nerve impulses away from the cell body in the form of electrical signals known as action potential, this is how neurons communicate with each other. Action potential is a brief change in the voltage across the membrane due to the flow of certain ions in and out.
• Myelin sheath


  Surrounds the axon acting as a fatty layer that insulates and protects the axon so that electrical impulses travel faster along the axon.
• Nodes of Ranvier


  If the myelin sheath was continuous is would slow down the electrical impulse. The myelin sheath is therefore segmented by gaps called nodes of Ranvier which speed up the transmission of the impulse by forcing it to jump across the gaps along the axon
• Terminal buttons


  Connect the neuron to other neurons using synaptic transmission, they produce neurotransmitters.
• Neuron locations


  • Motor neurons - cell bodies may be in the CNS but they have long axons which form part of the PNS
  • Sensory neurons - Outside of the CNS, in the PNS in clusters known as ganglia
  • Relay neurons - Make up 97% of all neurons, most are found within the brain and the visual system
• How action potential occurs


  When a neuron is in a resting state the inside of the cell is negatively charges compared to the outside. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing action potential to occur. This creates an electrical impulse that travels down the axon towards the end of the neuron.
• Neural groups


  Groups that neurons communicate with each other
• Synapse


  A tiny gap between each neuron
• Difference in signal transmission within vs between neurons


  Signals within neurons are transmitted electrically. Signals between neurons are transmitted chemically across the synapse.
• How chemical transmission occurs between neurons


  Action potential arrives at the pre-synaptic neuron. This stimulates a vesicle containing neurotransmitters to move down and bond to the wall of the presynaptic neuron. Neurotransmitters are released from the vesicles into the synaptic cleft. Neurotransmitters are then received by receptors on the post-synaptic receptors on the dendrites via lock and key mechanism.
• Neurotransmitters


  Chemicals that diffuse across synapses and bind to receptors on the next neurone carrying messages.
• There are different types of neurotransmitters, each with their own specific molecular structure and specialist functions. For instance acetylcholine is found at each point where a motor neuron meets a muscle and upon its release it will cause muscles to contract
• What happens when a neurotransmitter binds to its receptor

  It causes ion channels to open or close. This can produce a localised change in the membrane potential-voltage across the membrane of the receiving cells.
• Excitatory Postsynaptic Potential (EPSP)


  Changes in the membrane potential-voltage making the target cell more likely to fire its own action potential. Adrenaline causes excitation of the postsynaptic neuron by increasing its positive charge and making it more likely to fire
• Inhibitory Postsynaptic Potential (IPSP)


  Changes in the membrane potential-voltage making the target cell less likely to fire its own action potential. Serotonin causes inhibition in the receiving neuron resulting in it becoming more negatively charged and less likely to fire