Each neuron in the body is surrounded by anywhere from 6 to 60 neuroglia that protect, feed, and insulate the neuron. Neuroglia, also known as glial cells, act as the “helper” cells of the nervous system. Interneurons form complex networks within the central nervous system to integrate the information received from afferent neurons and to direct the function of the body through efferent neurons. Also known as motor neurons, efferent neurons transmit signals from the central nervous system to effectors in the body such as muscles and glands. Also known as sensory neurons, afferent neurons transmit sensory signals to the central nervous system from receptors in the body. There are 3 basic classes of neurons: afferent neurons, efferent neurons, and interneurons. Long transmitting processes called axons extend from the cell body to send signals onward to other neurons or effector cells in the body. Small tree-like structures called dendrites extend from the cell body to pick up stimuli from the environment, other neurons, or sensory receptor cells. The cell body is the roughly round part of a neuron that contains the nucleus, mitochondria, and most of the cellular organelles. Neurons look quite different from other cells in the body due to the many long cellular processes that extend from their central cell body. Neurons, also known as nerve cells, communicate within the body by transmitting electrochemical signals. The majority of the nervous system is tissue made up of two classes of cells: neurons and neuroglia. One common example is the knee reflex: hitting the patellar tendon just below the knee cap with a reflex hammer leads to an automatic contraction of the quadriceps – which results in the lower leg kicking out.Continued From Above. In addition to regulating the voluntary movements of the body, the somatic nervous system is also responsible for a specific type of involuntary muscle responses known as reflexes, controlled by a neural pathway known as the reflex arc.Ī reflex arc includes a sensory neuron that sends a signal straight to the spinal cord (bypassing the brain) which in turn generates a response such as a quick muscle contraction so fast that it’s subconscious. Image credit: MartaAguayo / Wikimedia commons Work at QBI is being conducted to understand the genetics and the molecular mechanisms responsible for MND. Several diseases affecting motor neurons, for example motor neurone disease (MND), result in death of the neurons (neurodegeneration) and eventually muscle wasting and loss of functions.
It’s interesting to note that while the neurotransmitter acetylcholine has an excitatory effect in the somatic nervous system (ramps up a response), in the autonomic nervous system (the involuntary nervous system), it has an opposite inhibitory function (dampens a response). The spinal nerves are 31 pairs of nerves that send sensory information from the periphery to the spinal cord and muscle commands from the spinal cord to the skeletal muscles. These nerves are required for the five senses and for the movement of head, neck and tongue. There are 12 pairs of cranial nerves, which send information to the brain stem (base of the brain where the spinal cord connects) or from the brain stem to the periphery. The nerves in the somatic nervous system are classified based on their location, either in the head regions or in the spine region. It contains both afferent nerves (which send information to the brain and spinal cord), made of sensory neurons that inform the central nervous system about our five senses and efferent nerves (which send information from the brain), which contain motor neurons responsible for voluntary movements, such as walking or lifting an object. The somatic nervous system (SNS) is also known as the voluntary nervous system.
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