bio

• The brain is an organ in the central nervous system (whichincludes the brain and spinal cord)The brain controls the body’s response to changes in theinternal or external environment, known as stimuli
• The nerves are a fiber of cells that use electrical andchemical signals to exchange information throughout thebody.
• neurons are the major cells of the nervous system.• Sensory neurons detect stimuli or changes in theenvironment such as heat or pain neurons found on fingertips• Motor neurons allow for movement as coordinated by thecentral nervous system• Interneurons connect other neurons to each oth
• structure of the Nervous System – Glial CellsGlial cells are the supporting cells of the nervous system.• Structural support• Insulation• Metabolism• Regulation
• The synapse is the area where twoneurons meet, in a lock and keymodel, to exchange information usingchemical messengers known asneurotransmitters. Unusedneurotransmitters undergo thereuptake process
• Chemical Messengers of the BrainNeurotransmitters are molecules released by neurons when an action potential is achieved.There are many different types, each of which are usually associated with certain types ofregulation:• Activating or deactivating another neuron• Enabling body functions such as movement• Enabling mental functions learning, memory, attention• Increasing or decreasing certain emotions or feelings
• Neurotransmitters open ion channelsNeurotransmitters released from the pre-synaptic neuron bind to specific receptors in thepost-synaptic neuron, opening ion channels in the post-synaptic neuron.An influx of positively charged ions changes the voltage of the post-synaptic neuron,initiating an action potential
• 1. Summary of an Action PotentialAxon terminal forms synapse with dendrites of anotherneuron.2. Axon terminal releases a chemical signal in the form of aNT.3. NT enters the receiving neuron’s dendrites via receptors.Excess NT are re-uptaken by original neuron.4. Receptors activated by NT transduce an electrical impulsevia ions entering the cell body.5. When enough ions to achieve threshold voltage activate anaction potential, an electrical charge travels down theaxon.6. Electric charge at the axon terminal activates the release ofNT.
• the brainstem connects the brain to the spine and controls the functions most essential tostaying alive.There are three structures that make thebrainstem:• Pons• Medulla• Reticular activating system
• CerebellumKnown as the “mini-brain,” the cerebellum manages balance andcoordinates movements. It makes up 10% of the brain butcontains over 50% of its neurons.
• Limbic SystemThe limbic system governs emotion and is madeof three main structures:• Hypothalamus: maintains homeostasis by exertingcontrol over the pituitary gland and autonomicnervous system• Hippocampus: responsible for memory (spatial andlong-term)• Amygdala: associated with fear responses
• ThalamusThe thalamus is the main sensoryprocessing center. It is also involved inattention and movement (alongside thebasal ganglia)
• The ForebrainThe cerebrum is the large portion of the brain. It has two hemispheres separated by thecorpus callosum.The cerebral cortex is the outer layer of cerebrum where most processing happensassociated with all functions.
• Plasticity is the brain’s ability to adapt its structure or function due to damage (e.g. injury,trauma etc.) or experience (e.g. learning, therapy etc.). The brain can do this by:• Changing neural pathwaysbased on usage• Neurogenesis: creating newneurons as needed• Stem cells: undifferentiatedcells can differentiate intoneurons
• At rest, a neuron has a voltage of (-70) mV
• When the axon terminal of a pre-synaptic neuron releases vesicles of neurotransmitters into the synapse, they bind to the receptor site of the ion channel on the post-synaptic neuron's dendrites
• This action opens the ion channel, allowing for positively charged ions to enter the post-synaptic neuron
• If a sufficient number of ions enter the cell, allowing it to reach its threshold of -55 mV, this will initiate the depolarization stage of an action potential
• The electrical change will cascade along the axon of the post-synaptic neuron, opening one ion channel after another until the action potential reaches the end of the neuron, known as the axon terminal
• During the repolarization stage, ions will start moving back out of the cell to return the cell to rest
• Repolarization overshoots the compensation of ions, leaving the cell at a further negative voltage than at rest, known as the refractory period
• During the refractory period, it is very difficult to initiate another action potential until all ion channels have closed and the neuron returns to rest