Nucleus - contains genetic material chromosomes including information for cell development and synthesis of proteins necessary for cell maintenance and survival.
Covered by a membrane. Nucleolus - produces ribosomes necessary for translation of genetic information into proteins Nissl Bodies - groups of ribosomes used for protein synthesis. Endoplasmic reticulum ER - system of tubes for transport of materials within cytoplasm.
Can have ribosomes rough ER or no ribosomes smooth ER. With ribosomes, the ER is important for protein synthesis. Golgi Apparatus - membrane-bound structure important in packaging peptides and proteins including neurotransmitters into vesicles. Mitochondria - produce energy to fuel cellular activities. Happy st Birthday to the Golgi apparatus! In , the famous neuroanatomist Camillo Golgi reported his discovery of a ribbon-like apparatus inside neurons of the cerebellum.
This structure now bears his name as the "Golgi apparatus. Color a neuron or several neurons online! Try the Neuron Review Test. Requires the Adobe Acrobat Reader. Answers to the Neuron Review Test. Build a Neuron - you must have the Shockwave plug-in for your browser. Get the Shockwave plug-in. Chudler All Rights Reserved. Take information away from the cell body Smooth Surface Generally only 1 axon per cell No ribosomes Can have myelin Branch further from the cell body.
Bring information to the cell body Rough Surface dendritic spines Usually many dendrites per cell Have ribosomes No myelin insulation Branch near the cell body. In a chemical synapse, action potentials affect other neurons via a gap between neurons called a synapse. Synapses consist of a presynaptic ending, a synaptic cleft, and a postsynaptic ending. This triggers the release of chemical messengers called neurotransmitters.
These molecules cross the synaptic cleft and bind to receptors in the postsynaptic ending of a dendrite. Neurotransmitters can excite the postsynaptic neuron, causing it to generate an action potential of its own. Electrical synapses can only excite. They occur when two neurons are connected via a gap junction. This gap is much smaller than a synapse, and includes ion channels which facilitate the direct transmission of a positive electrical signal.
As a result, electrical synapses are much faster than chemical synapses. However, the signal diminishes from one neuron to the next, making them less effective at transmitting. Neurons vary in structure, function, and genetic makeup. Given the sheer number of neurons, there are thousands of different types, much like there are thousands of species of living organisms on Earth.
In terms of function, scientists classify neurons into three broad types: sensory, motor, and interneurons. Sensory neurons are triggered by physical and chemical inputs from your environment. Sound, touch, heat, and light are physical inputs. Smell and taste are chemical inputs. For example, stepping on hot sand activates sensory neurons in the soles of your feet. Those neurons send a message to your brain, which makes you aware of the heat.
Motor neurons play a role in movement, including voluntary and involuntary movements. These neurons allow the brain and spinal cord to communicate with muscles, organs, and glands all over the body.
There are two types of motor neurons: lower and upper. Lower motor neurons carry signals from the spinal cord to the smooth muscles and the skeletal muscles.
Upper motor neurons carry signals between your brain and spinal cord. When you eat, for instance, lower motor neurons in your spinal cord send signals to the smooth muscles in your esophagus, stomach, and intestines. These muscles contract, which allows food to move through your digestive tract. Interneurons are neural intermediaries found in your brain and spinal cord.
They pass signals from sensory neurons and other interneurons to motor neurons and other interneurons. Often, they form complex circuits that help you to react to external stimuli. For instance, when you touch something hot, sensory neurons in your fingertips send a signal to interneurons in your spinal cord.
Dendrites bring information to the cell body and axons take information away from the cell body. Information from one neuron flows to another neuron across a synapse. The synapse contains a small gap separating neurons. The synapse consists of:. Hear IT! For communication between neurons to occur, an electrical impulse must travel down an axon to the synaptic terminal.
At the synaptic terminal the presynaptic ending , an electrical impulse will trigger the migration of vesicles the red dots in the figure to the left containing neurotransmitters toward the presynaptic membrane. The vesicle membrane will fuse with the presynaptic membrane releasing the neurotransmitters into the synaptic cleft. Until recently, it was thought that a neuron produced and released only one type of neurotransmitter. This was called "Dale's Law.
0コメント