Brain Bee 2024

• There are three main types of neurons - sensory neurons, motor neurons, and interneurons.
• Sensory neurons are neurons that are coupled with receptors specialized in detecting + responding to stimuli.
• Motor neurons control the activity of muscles and movement. They are responsible for all forms of behavior.
• Interneurons mediate simple reflexes, as well as being responsible for the highest functions of the brain.
• Glial cells have a supporting role for neurons, and also is important when it comes to nervous system development and adult brain function.
• Neurons have four main compontents: the dendrite, the cell body, the axon, and the synapse.
• The brain and the spinal cord are connected to sensory receptors and muscles through long axons that make up the peripheral nerves.
• The spinal cord has two functions: allowing for quick reflexes (ex. rapid withdrawl of a limb from a hot surface) and more complex motions, as well as acting as a highway between brain and body.
• Overall, the brain can be divided into two main parts: the brainstem and the cerebral hemispheres.
• The brain stem can be divided into three parts: the hind-brain, the mid-brain, and a "between-brain" called the diencephalon.
• The hind-brain is actually an extension of the spinal cord, it moderates crucial life functions such as breathing and blood pressure.
• The cerebellum (controls voluntary movement) arises from the top of the hind-brain.
• The midbrain contains neurons that predominantly use chemical messengers, these help moderate the activity of neurons that are in the higher centres of the brain.
• The diencephalon is divided into two different areas called the thalamus (regulates sensory information to cerebral cortex and back) and hypothalamus (controls the pituary gland, hormones, and maintains homeostasis).
• The cerebral hemispheres have a core, the basal ganglia, which is surrounded by thin sheets of neurons that make up the gray matter of the cerebral cortex.
• The basal ganglia play a central role in the initiation and control of movement.
• The cerebral cortex is greatly folded to allow for a larger surface area for the sheet of neurons that would otherwise be impossible.
• Sensory areas that recieve information from the skin are known as "somaesthetic" areas.
• The left half of the body sends information to the right hemisphere, while the right half of the body sends information to the left hemisphere.
• The two halves of the brain do not work in isolation; the two hemispheres are connected by a large fibre tract called the corpus callosum.
• The cerebral cortex is necessary for voluntary actions, language, speech, and other higher functions.
• Many functions carried out by the cerebral cortex occur in both hemispheres, but some are lateralized to one hemisphere over another.
• The dendrite recieves, the cell body integrates, and the axons transmit - a process known as polarization.
• The neuron is held together by membranes made of fatty acids, and are draped around a cytoskeleton made of rods of tubular and filamentous proteins.
• Tiny protuberances that stick out of dendrites are called "dendritic spines". These are where incoming axons make most of their connections.
• The end points of axons also respond to molecules known as growth factors - molecules that influence neuronal genes and dendrite growth.
• The part where dendrites have close contacts with other axons is called a synapse,
• Communication between nerve cells at synapses is called "synaptic transmission" and involves chemical processes.
• When a dendrite recieves a chemical messenger, miniature electrical currents are set up in the recieving dendritic spine. When currents move in, it is exhibition. When currentss move out, it is inhibition.
• The axons of neurons transmit electrical pulses called action potentials.
• The axonal membrane has ion channels that allow for the influx of sodium ions and others for potassium ions. This allows for the action potential to travel down the neuron.

  
• In the long run, Na+/K+ ion pumps help maintain the overall concentration gradient that allows for the action potential.
• An analogy used to help describe the action potential is lighting a firecracker.
• Patch-clamping is a modern electrical recording technique used by scientists to study the movement of ions in individual ion channels.
• An insulating blanket made of stretched-out glial cell membranes that cover an axon is called a "myelin sheath". It makes the neuron fire faster.
• Neurons that have myelin sheaths fire faster than neurons that are not insulated.
• The myelin sheath prevents the ionic currents in the axon from leaking out, but every so often there is a gap that concentrates Na+ and K+ ion channels.
• In fact, in myelinated neurons, actions potentials can travel 100 metres per second!
• Actions potentials have the distinctive characteristic of being "all-or-nothing" - they either fire or they don't. They do not vary in intensity, only in how often they occur.
• Alan Hodgkin and Andrew Huxley did experiments on the giant axon of the squid to study the transmission of the nerve impulse.