2.1.1 Cells Of The Nervous System 2 Flashcards
An ____ axon brings information into a structure; an ____ axon carries information away from a structure.
afferent : efferent
If a cells dendrites are entirely contained within a single structure, the cell is an ____ or intrinsic neuron of that structure.
interneuron
____ (or neuroglia), the other major components of the nervous system, do not transmit information over long distances is neurons do, although they perform many other functions.
Glia
The brain has several types of glia with different functions. The star-shaped ____ wrap around the presynaptic terminals of a group of functionally related axons.
astrocytes
By taking up ____ released by axons and then releasing them back to other axons, an astrocyte helps synchronise the activity of the axons, enabling them to send messages in waves.
ions
Astrocytes also remove ____ material created when neurons die and control the amount of blood flow to each brain area.
waste
____, very small cells, also remove waste material as well as viruses, fungi, and other microorganisms.
Microglia
____ in the brain and spinal-cord and Schwann cells in the periphery of the body are specialised glia that build the myelin sheaths that surround and insulate certain vertebrate axons.
Oligodendrocytes
____ ____ guide migration of neurons and their axons and dendrites during embryonic development.
Radial glia
The mechanism that excludes most chemicals from the vertebrate brain is known as the ____-____ barrier.
blood-brain
The blood-brain barrier depends on the ____ cells that form the walls of the capillaries.
endothelial
Outside the brain, such cells are separated by small gaps, but in the brain, they are joined so ____ that virtually nothing passes between them.
tightly
The barrier keeps out useful chemicals as well as harmful ones. Those useful chemicals include all ____ and ____ ____, the building blocks for proteins. For the brain to function, it needs special mechanisms to get these chemical across the blood-brain barrier.
fuel and amino acids
Mechanism one. Small uncharged molecules, including ____ and ____ ____, cross freely. Water crosses through special protein channels in the wall of the endothelial cells.
oxygen and carbon dioxide
Mechanism two. Molecules that dissolve in the ____ of the membrane also cross passively. Examples include vitamins A and D and all the drugs that affect the brain.
fats
For a few other chemicals, the brain uses ____ ____, a protein mediated process that expends energy to pump chemicals from the blood into the brain.
active transport
Chemicals actively transported into the brain include ____ (the brains main fuel), ____ ____ (the building blocks of proteins), purines, choline, a few vitamins, iron, and certain hormones.
glucose, amino acids
The blood-brain barrier is ____ to ____. In people Alzheimer’s disease or similar conditions, the endothelial cells lining the brains blood vessels shrink, and harmful chemicals enter the brain.
essential to health
However, the barrier also poses difficulty in medicine because it keeps out many ____.
medications
Most cells used a variety of carbohydrates and fats for nutrition, but vertebrate neurons depended almost entirely on ____, a sugar.
glucose
Because the metabolic pathway that uses glucose requires oxygen, neurons need a steady supply of ____.
oxygen
Although neurons require glucose, glucose shortage is rarely a problem. The liver makes glucose from many kinds of carbohydrates and amino acids, as well is from ____, a breakdown product from fats.
glycerol
The only likely problem is an inability to use glucose. To use glucose, the body needs vitamin B1, ____.
thiamine
Prolonged thiamine deficiency, common in chronic alcoholism, leads to death of neurons and a condition called ____ ____, marked by severe memory impairments.
Korsakoff’s syndrome
