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Neural cells
Neuro
Term | Definition |
---|---|
2 categories of cells in the nervous system | Neurons process and transmit info. Glia maintain homeostasis, form myelin, and provide support and protection for neurons. |
Most common glia (5) | ASOME: Astrocytes, Schwann cells, Oligodendrocytes, Microglia, Ependymal cells |
Astrocytes | CNS, grey & white matter - Provide supporting network in the brain by forming a complete lining on external surface of brain and blood vessels in CNS. Contribute to blood-brain barrier. Forms scars around dead brain tissue. |
Schwann cells | PNS - make up the myelin sheath in PNS, constitute fibrous connective tissue around PNS fibers. |
Oligodendrocytes | CNS - make up the myelin sheath in CNS. |
Microglia | CNS - travel to the site of lesion and engulf cellular debris before removing it. |
Ependymal cells | Ventricular cavity - form lining around ventricular surface. |
Neuronal transmission of information, Step 1 | Signal enters dendrite |
Neuronal transmission of information, Step 2 | Signal is summed up |
Neuronal transmission of information, Step 3 | Signal triggers action potential on the axon |
Neuronal transmission of information, Step 4 | Signal travels down the axon |
Neuronal transmission of information, Step 5 | Nodes of Ranvier boost the signal (saltatory conduction) |
Neuronal transmission of information, Step 6 | Possible connection to other dendrites or target cells via the synapse |
Structural Types of Neurons in CNS (5) | Neuroblasts, unipolar neurons, bipolar neurons, multipolar neurons, pseudounipolar neuron |
Neuroblasts | start as neural stem cells (which turn into most types of cells in the CNS). Neural stem cells differentiate into cells called neuroblasts which can only become neurons. |
Unipolar neurons | only have one axon (or process), these are mainly present during development |
Bipolar neurons | one soma, one axon, and one dendrite |
Multipolar neurons | one soma, one axon, but has multiple dendrites (most common structural type of neuron in adult humans) |
Pseudounipolar neuron | one soma, one short process that divides into two long processes going in different directions. |
Resting membrane potential | Without input, most neurons have a stable electrical charge, more negative on the inside of the cell membrane and more positive on the outside. |
Graded potentials | once information from inputs reaches a threshold potential, the neuron fires. Size and duration depends on the size and duration of the inputs. |
Action potentials | large in size, brief in duration; usually the same size and duration for any particular neuron (all or nothing). |
Effect of potassium pump | We end up with more Na+ outside and more K+ inside. 3:2 ratio makes the outside charge more positive (-70 mV difference), but resting cell membrane is highly permeable to K+ and may “leak” out. |