Sept 23 - Central Nervous System Flashcards
Name the two categories of cells in the CNS
Neurons and Glia (aka Neuroglia)
What are neurons?
They are specialized cells for rapid communication; reception, transduction and conduction of stimuli. They conduct signal (action potential) from one part of cell to another and which is then transmitted to other cells. They are specialized for generating and propagating impulses from cell to cell
What are glia cells?
The support cells of the nervous system. They have have numerous functions
Describe neurons
They are the basic unit/cell of the nervous tissue. One consists of dendrites, a cell body, an axon and axon terminals. The axon may be myelinated or unmyelinated
What are dendrites?
The site of inputs (excitatory or inhibatory)
Where does an axon commonly terminate?
On a neuron, where it forms a synapse
What is a synapse?
Site of signal transmission between neurons. Most synapses are chemical, i.e., a chemical/transmitter is released from an axon terminal (synaptic button) to act on a specific receptor on the post-synaptic cell
Name the three types of glia cells in the CNS
Astrocytes, Oligodendrocytes and Microglia
Name the two types of glia cells in the PNS
Schwann cells and Satellite cells
Where are astrocytes found? What are their function?
They are found in white matter and gray matter. Their functions include: physical/structural support, secreting growth factors, metabolic support, transmitter “scavengers” and ionic and pH balance of the environment. Basically, keeping neurons happy
What is the role of oligodendrocytes?
They function to provide the myelin sheaths around axons in the CNS (required for rapid conduction of the action potential). These cells are targeted in multiple sclerosis
What are microglia? What is their function?
They are the macrophages of the nervous system (ie. immune cells of the CNS). Their function is to protect against viruses, bacteria and tumour cells (digest invading cells; act as antigen-presenting cells in the CNS). They are activated during inflammation in the CNS, as well as after a stroke, to remove the dead cells
What are Schwann cells?
They are the myeline producing cells of the PNS
What are Satellite cells?
They support the cells of the PNS found within the ganglia
Name the two components of the nervous system
The central nervous system (the brain and spinal cord) and the peripheral nervous system (everything outside of the CNS)
Name the three components of the PNS
Cranial nerves, spinal nerves and associated structures (ganglia and sensory nerve endings)
How many cranial nerves are there?
12 pairs attached to brain
How many spinal nerves are there?
31 pairs attached to the spinal cord
What are ganglia?
Clusters of nerve cell bodies where synaptic transmission occurs
What are sensory nerve endings?
They detect pain, temperature, touch, muscle tension, joint movement, etc.
What is proprioception?
What allows you to know where your limbs are in space without even seeing them
How is the CNS divided?
Into gray matter, white matter and glial cells
What is gray matter?
It consists of neurons embedded within glia (neuropil is processes of glia and neurons within gray matter). In the brain, aggregation of gray matter is called a nucleus
What is white matter?
It consists of nerve fibres/axons embedded in glial cells (white because of high lipid content of myelin)
What are glial cells?
(i.e. glia/neuroglia) They are support cells for neurons
What does gray matter and white matter have in common?
They both contain glia (support cells of the CNS) and they blood vessels
With regard to gray and white matter, how does the brain and the spinal cord differ?
In the brain, gray matter is on the outside and white matter is on the inside. In the spinal cord gray matter is on the inside (butterfly-shape) and white is on the outside
What are ventricles?
Fluid filled cavities
Name the three sections of the brain
Forebrain, midbrain and hindbrain (the hindbrain is continuous with the spinal cord)
Name the two components of the forebrain
Telencephalon (Cerebrum)
Diencephalon
What is another name the for the midbrain? Describe the midbrain
Mesencephalon
Short, narrow “stalk” that connects forebrain with hindbrain
Name the three components of the hindbrain
Pons, cerebellum and medulla (the medulla is continuous with the spinal cord
What is the brain stem
It is the composed of the midbrain, pons and medulla