Nervous System Overview Quiz

Study Notes

The nervous system is the master controlling and communication system of the body, responsible for collecting information, integrating, and generating a motor output.
Three general functions of the nervous system:
- Collect information (sensory input)
- Integration (interpret sensory input and determine proper response)
- Motor output (activate effectors including muscle and glands)

Nervous tissue is composed of neurons and glia.
Two main cell types:
- Neurons (basic unit of the nervous system, excitable cells that transmit electrical signals, do not divide after developmental period)
- Glia (non-excitable, support and protect neurons, outnumber neurons 10:1, undergo mitosis throughout life)

Excitable (neuronal membrane generates electrical activity in response to stimulation)
Conductive (electrical signals are propagated across the plasma membrane)
Extreme longevity (most neurons are formed before birth and are still present in advanced age)
Amitotic (neurons lose their ability to divide)

The neuron cell body is the biosynthetic center of the cell, containing cytoplasm, nucleus, and other organelles.
Dendrites (branch off the cell body, receive information from other neurons, and transfer to the cell body)
Axon (singular process that transmits signals to other neurons, muscle cells, or glands)
Axon hillock (where axon leaves the cell body)
Axon terminals (form synapses with target cells, contain synaptic vesicles, and release neurotransmitters)

A synapse is made of a presynaptic neuron, the synaptic cleft, and a postsynaptic neuron.
The cytoskeleton provides support and structure for neurons (microfilaments, intermediate filaments, and microtubules)

Glial cells are "non-excitable" and support, protect, and provide a scaffold for neurons.
CNS glial cells:
- Astrocytes (most abundant glial cell in the CNS, regulate nutrients to neurons, control chemical environment)
- Oligodendrocytes (highly branched from a single soma, wrap processes tightly around axons, produce an insulted covering - myelin sheath)
- Microglia (monitor neurons and extracellular space for health and signs of disrupted homeostasis, transform into a type of macrophage)
- Ependymal cells (line CNS cavities, produce cerebrospinal fluid, cilia help circulate CSF)
PNS glial cells:
- Satellite cells (surround ganglion neuron cell body, regulate cellular environment, similar to astrocytes in the CNS)
- Schwann cells (myelinate PNS axons, similar to oligodendrocytes)

Large axons in the CNS and PNS are myelinated.
Myelination insulates and protects the axon, speeds conduction of electrical impulses down the axon.
Schwann cells myelinate axons in the PNS, while oligodendrocytes myelinate axons in the CNS.