The master controlling and communicating system of the body. Its cells communicate by electrical and chemical signals.
Information gathered by the nervous systems sensory receptors. Uses to monitor changes occuring inside and outside the body.
The process in which the nervous system processes and interprets sensory input.
The nervous system's response. Effector organs, such as muscles or glands, are activated.
Two principal parts of the NS.
Part of the nervous system that includes the brain and spinal cord.
Central nervous system (CNS)
Part of the NS outside the CNS. Consists of spinal and cranial nerves (bundles of axons).
Peripheral nervous system (PNS)
These nerves in the PNS carry impulses to and from the spinal cord.
The nerves in the PNS carry impulses to and from the brain.
Two functional subdivisions of the PNS.
Sensory division or afferent
Motor division or efferent
The subdivision of the PNS that consists of nerve fibers (axons) that convey impulses to the CNS from sensory receptors.
Sensory or afferent division
The subdivision of the PNS that transmits impulses from the CNS to the effector organs.
Mototr or efferent division
Two main parts of the motor or efferent division.
Somatic nervous system or voluntary
Autonomic nervous system or involuntary (ANS)
Two functional subdivisions of the autonomic nervous system.
Glial cells of the CNS. (4)
Glial cells of the PNS.
Glial of the CNS that is the most abundant and versatile. They support and brace neurons, assist in exchanges between neurons and capillaries, and guide neurons in synapse formation.
Glial of CNS that monitor health nearby neurons. Can become a special macrophage when invading microorga isms are present..
Glial in CNS that line the central cavities of the brain and the spinal cord forming a barrier seperating the cerebrospinal fluid and tissue fluid of CNS. Usually cilliated.
CNS glial that wrap their process around neuron fibers, forming a insulating covering or myelin sheath.
Neuroglia of the CNS that forms myelin sheaths.
Neuroglia that surround neuron cell bodies in the PNS. Similar to astrocytes of the CNS.
Neuroglia of the PNS that forms myelin sheaths. Functionally similar to the oligodendrocytes of the CNS.
Schwann cells or neurolemmocytes
Structuralized unit of the nervous system that conducts messages in the form of nerve impulses from one part of the body to another.
Neuron or nerve cells
Special characteristics of neurons. (4)
Conduct nerve impulses
High metabolic rate
The part of a neuron that is the electrical site for signalling.
The biosynthetic center of a neuron that contains the organelles.
Neuron cell body or soma or perikaryon
The rough ER of a neuron is probably the most active and developed in the body is referred to as...
Nissl bodies or chromatophilic substance.
These, which are found in the neuron cell body, are important in maintaining cell shape and integrity. (2)
Microtubules and neurofibrils
Most neuron cell bodies are located in the _NS.
Clusters of cell bodies in the CNS.
Cell bodies lie along the nerves of the PNS.
Armlike extensions of the cell body of all neurons.
The _NS contain both neuron cell bodies and their processes. Bundles of neuron processes are called tracts.
The _NS consists chiefly of neuron processes. Bundles of neuron processes are called nerves.
These two types of neuron processes differ in the structure and function of their plasma membranes.
Short, tapering, branching extensions of motor neurons. This is the main receptove or input region.
Dendrites convey incoming messages toward the cell body with these short-distance signals.
This arises from a cone-shaped area of the cell body called the hillock. Any long example is called a nerve fiber.
How many axons per neuron?
Branches of an axon the extends at right angles.
The branches at the end of an axon.
Terminal branches or telodendria
The knob-like endings of the terminal branches of axons.
Axon terminals, synaptic knobs, or boutons
The conducting region of a neuron. It generates nerve impulses and transmits them along the axolemma.
The secretory region of the neuron.
Axons lack these two structures that are involved in protein synthesis and packaging.
Nissl bodies and Golgi apparatus
Movement toward axon terminals.
Movement away from axon terminals.
Mitochondria, cytoskeleton elements, membrane components, and necessary enzymes are moved in this direction.
Organelles that are to be degraded or recycled are moved in this direction.
Whitish, fatty sheath that covers many nerve fibers. Protects and electrically insulates fibers and increases speed of transmission of nerve impulses.
These fibers conduct nerve impulses rapidly.
The absence of these in the plasma membrane of myelinated cells make myelin sheaths exceptionally good electrical insulators.
Channel and carrier proteins.
The bulge of a Schwann cell's plasma membrane that is just external to the myelin sheath that includes the nucleus and most of the cytoplasm.
The gaps between Schwann cells that occur at regular intervals along the myelinated axon. Also called myelin sheath gaps.
Nodes of Ranvier
Axon collaterals can emerge from an axon here.
Nodes of Ranvier
These form the myelin sheaths of the CNS. They lack a neurolemma the extensions are forming the sheaths.
Term that refers to regions of brain and spinal cord containing dense collections of myelinated fibers. Are primarily fiber tracts.
Contains mostly nerve cell bundles and unmyelinated fibers.
Three major neuron groups based on the number of processes extending from cell body.
Most common type of neuron (99%+) and the majority of the CNS. Three or more processes.
Rare neuron type found in some special sense organs. Two processes - an axon and a dendrite.
Type of neuron that has a single short process that divides into peripheral and central processes.
Unipolar neurons or pseudounipolar neurons
Three classifications of neurons based on the direction of the nerve impulse relative to the CNS.
Class of neuron that transmits impulses from sensory receptors in the skin or internal organs towards or into the CNS. Unipolar. Cell bodies located outside CNS.
Sensory, or afferent, neurons
Class of neuron that carry impulses away from the CNS to the effector organs. Multipolar. Cell bodies located in CNS with few exceptions.
Motor, or efferent, neurons
Class of neurons that lie between motor and sensory neurons in neural pathways and shuttle signals through CNS pathways where integration occur. 99%+ neurons of body. Most confined within the CNS. Multipolar.
Interneurons, or association neurons
Channels which are always open.
Leakage, or nongated channels
Three types of gate channels.
Chemically or ligand-gated channels
Mechanically gated channels
These gates open when the appropriate chemical (i.e. a neurotransmitter) binds.
Ligand-gated, or chemically gated channels.
Channels that open or close in response to changes in membrane potential.
Channels that open in response to physical deformation of the receptor (as in sensory receptors for touch and pressure.
Mechanically gated channels
Ion flows along this underlie all electrical phenomena in neurons.
Two types of signals that can be produced by changes in membrane potential.
Graded potentials (incoming signals over short distances)
Action potentials (long distance axon signals)
A reduction in membrane potential. Increases probability of producing a nerve impulse.
Occurs when membrane potential increases, becoming more negative. Reduces probability of producing nerve impulses.
Short-lived, localized changes in membrane potential that can be either depolarizations or hyperpolarizations. Magnitude varies directly with stimulus strength. Triggered by change in the neuron's environment that cause gated ion channels to open.
When the receptor of a neuron is excited by energy (heat, light, other) this stype of graded potential is formed.
Receptor potential or generator potential
Graded potential that is formed when a neurotransmitter realeased form a neuron stimulates another neuron.
A brief reversal of membrane potential with a total amplitude of about 100 mV. Also called a nerve impulse and is typically generated only in axons.
Two types of cells that can generate action potential due to their excitable membranes.
Four events of action potential.
Phase of action potential generation when all gated Na+ and K+ channels are closed.
Phase of action potential generation when Na+ channels open after reaching threshold.
Phase of action potential generation where Na+ channels are inactivating, and K+ channels are open.
Both the abrupt decline in Na+ permeability and the increased permeability to K+ contribute to this.
Phase of action potential generation where some K+ channels remain open, and Na+ channels reset.
Hyperpolarization or undershoot
This restores resting electrical conditions.
These restore resting ionic conditions.
Na+ - K+ pumps
The movement of an AP alond the entire length of an axon.
The period from the opening of the Na+ channels until the channels begin to reset to their resting state. Ensures that each AP is a seperate, all-or-none event, and enforces one-way transmission of AP.
Absolute refractory period
The period following the absolute refractory period. Repolarization is occuring, most Na+ channels are resting, some K+ still open. An axon's threshold is is elevated.
Relative refractory period
Two factors that the rate of impulse propogation depend on.
Degree of myelination
A type of conduction where APs are triggered at nodes. The electrical signal jumps from node to node.
Group of fibers that are mostly somatic sensory and motor fibers serving the skin, skeletal muscles, and joints. Largest diameter and thick myelin sheaths. Conduct at 150 m/s.
Group A fibers
These fiber groups are autonomic nervous system mototr fibers serving the viseceral organs; viscreal sensory fibers; and somatic sensory fibers (afferent from skin).
Group B fibers
Group C fibers
Group of fibers that are lightly myelinated fibers of intermediate diameter. Conduct at 15 m/s.
Group B fibers
Group of fibers that have the smallest diameter and are unmyelinated. Conduct at 1 m/s.
Group C fibers
A junction that mediates information transfer from one neuron to the next or from a neuron to an effector cell.
A synapse between the axon endings of one neuron and the dendrites of another.
A synapse between axon endings of one neuron and the soma of other neurons.
The neuron conducting impulses toward the synapse.
The neuron transmitting the electrical signal away from the synapse.
Two types of synapses.
Less common type of synapse that consist of a gap junction. Neurons joined this way are electrically coupled, synchronized, and transmission is rapid. May be unidirectional or bidirectional. Specialized to control the flow of ions between neurons.
Synapses which are specialized for release and reception of chemical neurotransmitters. Can be excititory or inhibitory.
Two parts of a chemical synapse which are seperated by a synaptic cleft..