Nervous System Flashcards
Neuron
A nerve cell that is capable of conducting nerve impulses
Afferent neuron
A neuron that carries impulses from sensory receptors to the central nervous system; also called a sensory neuron
Interneuron
A local circuit neuron of the central nervous system that relays impulses between afferent (sensory) and efferent (motor) neurons
Efferent neuron
A neuron that carries impulses from the central nervous system to skeletal muscles; also known as a motor neuron
Dendrite
A projection of cytosol that carries signals toward the nerve cell body
Axon
An extension of cytosol that carries nerve signals away from the nerve cell body
Glial cell
A non-conducting cell that is important for the structural support and metabolism of nerve cells
Ex. Schwann cells
Myelin sheath
An insulated covering over the axon of nerve cell
node of Ranvier
A regularly occurring gap between sections of myelin sheath along the axon
Central nervous system (CNS)
The body’s coordinating centre for mechanical and chemical actions; made up of the brain and spinal cord
Peripheral nervous system (PNS)
All parts of the nervous system, excluding the brain and spinal cord; relays information between the CNS and other parts of the body
Ex. afferent and efferent system
Afferent system
The component of the PNS that receives input through receptors and transmits the input to the CNS
Ex. sensory receptors
Efferent system
The component of the PNS that varies signals away to the effectors (muscles and glands)
Ex. skeletal and smooth muscles, and glands
Somatic system
A subdivision of the efferent system (within the PNS); composed of efferent (motor) neurons that carry signals to skeletal muscles in response to external stimuli
Ex. communication with the skeletal muscles, and voluntary processes (some contractions like reflexes and shivers are involuntary)
Autonomic system
A subdivision of the efferent system (within the PNS); regulates the internal environment
Ex. communication with smooth muscles and glands and involuntary processes, such as digestion, secretion by sweat glands, circulation of blood, etc.
Sympathetic system
One of the two subdivision of the autonomic nervous system; increase energy consumption and prepares the body for action
Ex. dominates situations that involve stress, danger, etc., and increase heart rate, raise blood pressure by vasoconstriction, dilate pupils, etc.
Parasympathetic system
One of two subdivisions of the autonomic nervous system; stimulates body activities that acquire and conserve energy
Ex. dominate in quiet, low-stress situations, and reduce rapid heartbeat and elevated blood pressure, and digestion predominates