receive and transmit information to other cells

adult human brain: 86 billion neurons

water, oxygen, sodium, potassium, calcium, chloride, etc. can cross

nucleus: the structure that contains the chromosomes

mitochondrion: performs metabolic activities, providing the energy that the cell uses for activity

endopl. ret.: network of thin tubes - transport newly synthesized proteins to other locations

its soma is in the spinal cord, it receives excitation through its dendrites and conducts impulses along its axon to a muscle

specialised at one end to be highly sensitive to a particular type of stimulation, such as light, sound or touch; the sensory neuron conducts information from the skin to the spinal cord

the cell's soma is located on a little stalk off the main trunk

their surface is lined with specialized synaptic receptors, at which the dendrite receives information from other neurons

the greater the surface area of a dendrite, the more information it can receive

soma (cell body): contains the nucleus, robisomes and mitochondria - most metabolic work occurs here

can be more than a meter in length (e.g.: axons from spinal cord to feet)

branching fibers that get narrower near their ends

vertebrate axons: many are covered with an insulating material - myelin sheath, with interruptions known as nodes of Ranvier

a neuron can have only one axon but the axon may have branches - the end of each branch has a swelling, called a presynaptic terminal

afferent: brings info into a structure - sensory neurons

efferent neurons carries info away from a structure - motor neurons

intrinsic neuron/interneuron: if a cell's dendrites and axons are entirely contained within a single structure - e.g.: an intrinsic neuron of the thalamus has its axon and its denrites within the thalamus

vary enormously in size, shape and function

the term glia is derived from a greek word meaning glue

neurons outnumber glia in a lot of brain areas, especially the cerebellum; but overall the numbers are almost equal

astrocytes - important for generating rhythms such as breathing

microglia - tiny cells, part of the immune system, removing viruses and fungi from the brain; they proliferate after brain damage, removing dead or damaged neurons; contribute to learning and memory by removing weak synapses

oligodendrocytes (in the brain) + Schwann cells (in the periphery of the body) - building myelin sheaths around axons

radial glia - guide the migration of nerions and their axons and dendrites during embryonic development

like any other organ, the brain needs to receive nutrients from the blood - but many chemicals cannot cross from the blood to the brain - this excluding mechanism is called the blood-brain barrier

but it also blocks out useful chemicals such as amino acids, th ebuilding blocks for proteins (thats why it can only be found in the brain and not in the rest of the body

(how fast a drug takes effect depends largely on how readily it dissolves in fats and therefore crosses the blood-brain barrier)

water crosses through special protein channels in the wall of the endothelial cells

for certain chemicals, the brain uses active transport (a protein-mediated process) - glucose (the brain's main fuel), amino acids, purines, choline, vitamins, iron

a disadvantage: treating brain cancer - nearly all the drugs used for chemotherapy dail to cross the BBB

glucose (the only nurtient that crosses the BBB in large quantities) - neurons depend almost entirely on this sugar

the human brain uses about 20 % of the body's oxygen and 25 % of its glucose

prolonged thiamine deficiency (common in chromic alcoholism) leads to death of neurons + a condition called Korsakoff's syndrome, marked by severe memory impairments