Neurobiology and immunology (unit 3)

• The CNS consists of the brain and the spinal cord.
• The peripheral nervous system (PNS) consists of the somatic nervous system (SNS) and the autonomic nervous system (ANS).
• The somatic nervous system contains sensory and motor neurons.
• The autonomic nervous system (ANS) consists of the sympathetic and parasympathetic systems.
• The sympathetic system speeds up heart rate and breathing rate while slowing down peristalsis and the production of intestinal secretions.
• The parasympathetic system decreases heart rate, and breathing rate and increases peristalsis and production of intestinal secretions.
• In a converging neural pathway, impulses from several neurons travel to one neuron. This increases the sensitivity to excitatory or inhibitory signals.
• A diverging neural pathway, impulses from one neuron travel to several neurons affecting more than one destination at the same time.
• A reverberating pathway, neurons later in the pathway link with earlier neurons, sending the impulse back through the pathway. This allows repeated stimulation of the pathway.
• The cerebral cortex is the centre of conscious thought. It also recalls memories and alters behaviour in the light of experience.
• Association areas involved in language processing, personality, imagination, and intelligence.
• Localisation of brain functions in the cerebral cortex. It contains sensory areas, motor areas, and association areas
• Information from one side of the body is processed in the opposite side of the cerebrum.
• Transfer of information between the cerebral hemispheres occurs through the corpus callosum.
• The left cerebral hemisphere deals with information from the right visual field and controls the right side of the body
• Memory involves encoding, storage and retrieval of information.
• All information entering the brain passes through sensory memory and enters short-term memory (STM). Information is then either transferred to long-term memory (LTM) or is discarded.
• Sensory memory retains all the visual and auditory input received for a few seconds from the sensory register.
• Short-term memory (STM) has a limited capacity and holds information for a short time. The capacity of STM can be improved by chunking.
• Memory span, the serial position effect, maintaining items by rehearsal and loss of items by displacement and decay.
• STM can also process data, to a limited extent, as well as store it. This working memory model explains why the STM can perform simple cognitive tasks.
• Long-term memory (LTM) has an unlimited capacity and holds information for a long time.
• The transfer of information from STM to LTM by rehearsal, organisation and elaboration
• Retrieval is aided by the use of contextual cues. They relate to the time and place when the information was initially encoded into LTM.
• Rehearsal is regarded as a shallow form of encoding information into LTM.
• Elaboration is regarded as a deeper form of encoding which leads to improved information retention.
• Axons are surrounded by a myelin sheath which insulates the axon and increases the speed of impulse conduction.
• Myelination continues from birth to adolescence.
• Responses to stimuli in the first two years of life are not as rapid or co-ordinated as those of an older child or adult.
• Certain diseases destroy the myelin sheath causing a loss of co-ordination.
• Glial cells produce the myelin sheath and support neurons.
• Neurons connect with other neurons or muscle fibers at a synaptic cleft to relay impulses.
• Neurotransmitters are stored in vesicles in the axon endings of the presynaptic neuron which are released into the cleft on arrival of an impulse. They diffuse across the cleft and bind to receptors on the membrane of the postsynaptic neuron.
• The need for removal of neurotransmitters by enzymes or reuptake to prevent continuous stimulation of postsynaptic neurons.
• A minimum number of neurotransmitter molecules must attach to receptors in order to reach the threshold on the postsynaptic membrane to transmit the impulse.
• Summation of a series of weak stimuli can release enough neurotransmitter to trigger an impulse.
• Convergent neural pathways can release enough neurotransmitter molecules to reach a threshold and trigger an impulse.
• Endorphins are neurotransmitters that stimulate neurons involved in reducing the intensity of pain.
• Endorphin production increases in response to severe injury, prolonged and continuous exercise, stress and certain foods.
• Increased levels of endorphins are also linked to the feelings of pleasure obtained from activities such as eating, sex and prolonged exercise.