Neuroscience
Nervous systems
Learning Objectives
- Know how we categorize different nervous systems in the body
- Be able to name one thing that is different between the central and peripheral nervous systems
The nervous system can be divided into four major regions: the central nervous system (CNS) and the peripheral nervous system (PNS), the sympathetic and parasympathetic nervous system, and the enteric nervous system. We’ll focus here on the CNS and PNS.
The central nervous system consists of the brain and spinal cord; the peripheral nervous system consists of everything else. The spinal cord transmits information for the brain to process. The brain is contained within the cranial cavity of the skull, and the spinal cord is contained within the vertebral cavity of the vertebral column.
The peripheral nervous system is like a system that collects information and sends commands. The PNS is so named because it is on the periphery—meaning beyond the brain and spinal cord.
Neurons in the central nervous system cannot regenerate or grow back after injury. The most obvious example of this is paralysis after spinal cord injury. Peripheral neurons, on the other hand, often do regrow after injury. For example, after a deep cut on the skin, the area around the cut is often numb for a long time after the cut looks like it has healed. But slowly—after several weeks or months—the sensation comes back.
Brain Anatomy
Learning Objectives
- Know the major sub-divisions of the brain (cortex, cerebellum, thalamus)
- Know the major terms to talk about directions in the brain (neuroscience terms for up/down, front/back)
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Neurons
Learning Objectives
- Be able to name the separate functions of axons, dendrites, and cell bodies
- Be able to describe membrane potentials and action potentials to a neighbor
Neurons are the largest population of cells in the nervous system that specialize in communication. They can come in several shapes and sizes depending on their specialized functions but all neurons will have axons and dendrites that protrude from the cell body.
There are almost as many glial cells as there are neurons in the body’s nervous system. Glial cells mostly act as caretaker cells, supporting the neurons and their connections. There are several different types.
Parts of a neuron
Dendrites are specialized structures for receiving and integrating signals from other cells. They do this mainly through receptors for small molecules and gases that are released from specialized structures at the end of the axons of other neurons.
Most neurons have a single axon that typically sends electrical impulses outwards away from the cell body. Axons can have branches, or collaterals, that can connect with other cells, or groups of cells. Axons in the PNS often travel in bundles known as nerves.
Synapses
Neurons communicate through axon-dendrite, axon-soma and sometimes dendrite-dendrite connections but these protrusions don’t actually touch. A chemical synapse consists of