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Nervous System structure, neurons

Terms in this set (24)

Central Nervous System
(CNS) brain and spinal cord. Main function is to process information received from the body's internal and external environments and to activate appropriate responses.
Peripheral Nervous system
is the entire network of nerves located outside the CNS. The PNS:
- carries information to the CNS from the body's muscles, organs and glands (about the internal environment) and from the sensory organs (about the external environment)
- carries information from the CNS to the body's muscles, organs and glands.
Autonomic Nervous System
a subdivision of the PNS that connects the CNS to the body's internal organs (such as the heart, stomach and liver) and glands (such as sweat, salivary and adrenal glands), providing feedback to the brain about their activities. Usually self-regulating, occurs without conscious effort and not under voluntary control.
Somatic Nervous System
a network of nerves that carries sensory information to the CNS and motor information from the CNS. Sensory information is received at sensory receptor sites in the body and carried along sensory neural pathways by sensory neurons. Motor information is carried along motor neural pathways by motor neurons to skeletal muscles to control their activity. Skeletal muscles are attached to our bones and respond to messages from the CNS to initiate, change or stop movement.
Synapse
the site where communication occurs between adjacent neurons. The three components of the synapse are the terminal buttons of the presynaptic ('sending') neuron, the dendrites of the postsynaptic ('receiving') neuron & the synaptic gap between the two neurons.
Myelin Sheath
is a white, fatty substance (made up of certain types of glial cells) that surrounds and insulates the axon and allows for the rapid movement of the message along the axon without being interrupted or distorted. Messages travel much faster through neurons wrapped in myelin than unmyelinated neurons.
Axon
a single, tubelike extension that transmits neural information to other neurons (or cells in muscles and glands). Most neurons have only one axon but many axons have branches that allow a message to be sent to multiple cells. Axons vary in length from a metre tp as small as the width of a single hair. Nerves are actually cable-like bundles of multiple axons
Dendrites
an extension of a neuron (from the soma) that detects and receives (chemical) information from other neurons (during 'lock & key' process). 'Dendritic spines' are outgrowths on the dendrite and grow due to neuroplasticity.
Neurotransmitters
a chemical substance produced by a neuron that carries a message to other neurons or cells in muscles, organs or other tissue. A neurotransmitter works by attaching itself ('binding') to receptor sites of postsynaptic neurons that are specialised to receive that specific neurotransmitter.
Sensory Neuron
receives and carries sensory information from both the external and internal environments and transmits to the CNS. It is also called an afferent neuron and travels along afferent tracts to the CNS. (SA-ME)
Interneuron
sends messages between sensory & motor neurons within the CNS, relaying information from one to the other (because sensory and motor neurons rarely ever connect directly). Note that they are only found in the CNS.
Motor Neuron
carries messages from the CNS to cells in skeletal muscles, organs and glands to stimulate activity. It is also called an efferent neuron and travels along afferent tracts to the PNS. (SA-ME)
Resting Potential
Non-active state of a neuron (not sending an impulse)
Action Potential
the change in electrical potential associated with the passage of an impulse along a muscle cell or nerve cell.
Autonomic functions
Regulate involuntary actions like the intestines, heart, and glands.
Efferent Tracts
A nerve pathway that goes downwards from the brain (CNS) toward the PNS carrying motor information
Afferent Tracts
A nerve pathway that goes upward from the PNS to the spinal cord toward the brain (CNS) carrying sensory information
axon terminals
small branches at the end of an axon called axon collaterals. At the end of the collaterals are axon terminals. Each axon terminal has a small knob-like swelling at its tip called a terminal button (sometimes called a synaptic vesicle, synaptic knob or synaptic button). The terminal button is a small structure like a sac that stores and secretes neurotransmitter that is manufactured by the neuron and carries its chemical message to other neurons or cells.
neuron
an individual nerve cell that is specialised to receive, process and/or transmit information. Communicate with each other, but also with muscles and glands. Information always travels in one direction through a neuron. Although each neuron has only one axon, the collaterals and axon terminals allow its message to be sent to many other neurons simultaneously.
parasympathetic nervous system
helps to maintain the internal body environment in a steady, balanced state of normal functioning. Generally has the effect of counterbalancing the activities of the sympathetic nervous system. It restores the body to a state of calm, once the need for sympathetic nervous system activation has passed.The parasympathetic nervous system dominates the sympathetic nervous system most of the time. It is involved in routine, everyday activities.
spinal reflex
an unconscious, involuntary and automatically occurring response to certain stimuli without any involvement of the brain. Referred to as a reflex arc because the response to an incoming stimulus is automatically 'reflected back' from the spinal cord without any initial input from the brain and before the brain processes a conscious perception of the stimulus.
synaptic gap
the tiny space between the terminal buttons of one neuron, which release the neurotransmitter, and the dendrites of another, which receive the neurotransmitter. Forms one component of the synapse.
unconscious response
to a sensory stimulus is a reaction that does not involve awareness. It is involuntary, unintentional, automatic and we cannot ordinarily control its occurrence. Bodily responses regulated by the ANS occur automatically without conscious effort, eg. pumping blood from your heart, digesting your food. Many of these ANS functions are actually reflexive responses.
conscious response
to a sensory stimulus is a reaction that involves awareness. The response will usually be a voluntary, 'intentional' reaction. The reaction, even if momentary, is also likely to be goal directed ('purposeful') and you will be able to exercise some degree of control over it.
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