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Central nervous system
Brain and spinal cord in vertebrates
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Peripheral nervous system
(PNS) All neurons and projections of their plasma membranes that are outside of the CNS
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Grey matter
- the major component of the CNS, consisting of:
- –Neuronal cell bodies, dendrites and axons;
- –Glial cells;
- –Capillaries;
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•White matter,
- mostly contains myelinated axon tracts
- –The color difference arises mainly from the whiteness of myelin.
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Neurons
- Generate, send and receive information
- through electrical and
- chemical signals;
- to and from other neurons or other cells throughout the body
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What animals don't have neurons?
sponges
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What cells can be excitable
neurons, muscle cells, and endocrine cells, as well as in some plant cells
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What is the voltage for:
action potential?
threshold potential?
What is the resting potential?
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What effect do action potentials have on muscle cells?
B-cells in pancreas?
- -an action potential is the first step in the chain of events leading to a contraction
- -release of insulin
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What makes up dendrites and axons?
Plasma membrane
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what part of a neuron contains the nucleus and organelles?
the cell body or soma
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Dendrites
Branched projections of a neuron that conduct the electrochemical stimulation received from other neural cells.
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Axons
- -Long, slender projection of neurons
- -Conducts electrical impulses away from the soma;-rich in voltage-gated ion channels
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Synapses
- -place of transmission of neurotransmitters/electrical impulse, from axon to dendrite
- -full of neurotransmitter vesicles
- -Dendrite receptor is loaded with ligand gated ion channels
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Glial Cells or Neuroglia
- •Non nervous cells of the NS
- –commonly known as the glue of the NS
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What are the ratios of Glial cells to neurons in the brain
- roughly 1:1
- in cerebellum 3:2
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What are the six types of Glial cells
- 1.Astrocytes
- 2.Microglia
- 3.Ependymal cells
- 4.Oligodendrocytes
- 5.Satellite cells
- 6.Schwann cells
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Astrocytes
–star-shaped glial cells–provision of nutrients–maintenance of extracellular ion balance; –repair and scarring process of the brain and spinal cord; and–biochemical support of endothelial cells
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The Blood brain Barrier (BBB)
-def
-effect on different molecules
- •A separation between the circulating blood and the brain extracellular fluid;
- •Consist of tight junctions around the capillaries that do not exist in normal circulation;
- –Restrict the diffusion of microscopic objects, e.g.•bacteria and large or hydrophilic molecules into CSF;
- •while allowing the diffusion of small hydrophobic molecules (O2, CO2, hormones).
- –Actively transport metabolic products such as glucose

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Schwann cells
- •The principal glia cells of the PNS
- -Wrap around axons of motor and sensory neurons to form the myelin sheath
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Myelin
Def
Purpose
Composition
- •;An electrically inulating material that forms a layer around axons
- •Essential for the proper functioning of the nervous system;
- •Composed of:
- – ~ 80% lipids, primarily the glycolipids galactocerebroside
- –~20% protein
- •myelin basic protein (MBP),
- •myelin oligodendrocyte glycoprotein (MOG), •proteolipid protein (PLP).
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Schwann cells myelinate the _NS
Oligodendrocytes myelinate the _NS
Schwann cells myelinate the PNS Oligodendrocytes myelinate the CNS
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Three Main Types of Neurons
- •Interneurons or Association Neurons
- •Motor neurons
- •Sensory neurons
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Interneurons or Association Neurons
- –Form interconnections between other neurons in the CNS;
- –Tend to have many dendrites;
- –Axons are typically short and highly branched allowing them to form complex connections with other cells
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•Motor neurons
–Efferent: send signals away from CNS to elicit response
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•Sensory neurons
- –Afferents: detect information from the outside world or internal body conditions & transmit to the CNS;
- –Usually a large axon that bypasses the cell body and goes directly to the CNS
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Reflex Circuits
- •The stimulus from sensory neurons is sent to the CNS, but there is little or no interpretation of the signal;
- –Few interneurons are involved
- •The signal is then transmitted to motor neurons, which elicit a response, such as a knee jerk
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