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Test 4
Nervous Tissue, Brain, Spinal Cord
58
Anatomy
Undergraduate 3
06/13/2013

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Term
Functions of the nervous system
Definition
Main control and regulatory system of the body. It communicates electrically and chemically to send messages very quickly from the CNS of the body and from the periphery of the body to CNS
Term
Sensory Receptors
Definition
specialized structures that detect changes= sensory input. Examples would include the eyes, Merkel/tactile cells, ears, temperature and pain receptors (nocireceptors)
Term
Afferent Pathway
Definition
nerve pathway through which sensory input is transmitted to CNS. Formed by axons of sensory neurons
Term
Control Center
Definition
structure (CNS) that analyzes the sensory input and makes a decision to respond to the change. Decision is made by the interneurons, also called association neurons
Term
Efferent Pathway
Definition
nerve pathway through which motor output is sent away from CNS. Carried by axons of motor neurons
Term
Effector Organs
Definition
carry out the decision (motor output). Examples: skeletal muscles contract; smooth muscle relaxes blood vessels; glands produce sweat
Term
Somatic
Definition
the division mainly controls skeletal muscles of the body
Term
Autonomic
Definition
this division is called the visceral division. It carries signals to internal organs like glands, cardiac muscles, and smooth muscles. It is involuntary
Term
CNS
Definition
Brain (enclosed and protected by the cranium) and spinal cord (enclosed and protected by the vertebral column)
Term
PNS
Definition
nerves (spinal and cranial nerves) and ganglia (like dorsal root ganglion). Has sensory (afferent) and motor (efferent division). Also has somatic and visceral (autonomic) division
Term
Unipolar
Definition
this neuron has an extension coming off the soma that divides into a dendrite and an axon. Seen in sensory neurons of dorsal root ganglion
Term
Bipolar
Definition
Has one dendrite and one axon. Rare form. Found in sensory organs (like olfactory receptor/smell)
Term
Multipolar
Definition
this is the most common neuron. Have many more branches of dendrites than the other two neuron types but only one axon. Found mostly in CNS
Term
Dendrites
Definition
are receiving regions of neurons. Local potentials are usually created on dendrites and then travel to axon hillock
Term
Soma
Definition
this part of the neuron contains the nucleus and other organelles
Term
Axons
Definition
are conducting regions of neurons. Can have a myelin sheath or lack a myelin sheath
Term
Location of cell bodies
Definition
Somas of neurons and dendrites are located in the grey matter of the brain and spinal cord. If somas are located outside CNS, those places are called ganglia
Term
Oligodendrocytes
Definition
from the myelin sheath in the brain and in the spinal cord
Term
Ependymal cells
Definition
line the cavities of the brain (ventricles) and in spinal cord (central canal)
Term
Microglia
Definition
phagocytize and destroy microorganisms, foregin matter, and dead nervous tissue
Term
Astrocytes
Definition
have the most functions. Participate in forming the BBB
Term
Oligodendrocytes
Definition
these glial cells have as amany as 15 armlike projections. These projections reach out to surrounding nerve fibers and form the myelin sheath around different axons
Term
Ependymal cells
Definition
these cuboidal epithelial cells are great for lining cavities of the brain and spinal cord. These cells produce the cerebrospinal fluid (CSF) that bathes the CNS and its cavities with nutrient rich fluid
Term
Micrglia
Definition
these cells have a soma with many fingerlike projections. These projections allow the microglia to probe, attach, destroy cellular debris or foreign material that they come across
Term
Astrocytes
Definition
the most abundant glial cells that have a star-shaped appearance with armlike projections to connect to capillaries in the brain. Form a tight seal called the blood-brain barrier
Term
Schwann cells (PNS)
Definition
these glial cells form the neurilemma and the myelin sheath around all PNS nerve fibers
Term
Satellite cells (PNS)
Definition
these cells surround the somas. Their thick covering protects the soma much like the Schwann cells protect the nerve the nerve fiber by providing electrical and chemical regulation
Term
permeability
Definition
the ability to transport/allow solutes through a membrane
Term
Sodium
Definition
ECF concentration is high, ICF is low
Term
Potassium
Definition
ICF concentration is high, ECF is low
Term
Chloride
Definition
ECF concentration is high, ICF concentration is low
Term
Concentration gradient
Definition
unequal distribution of ions across the plasma membrane due to its permeability. Normally permeable to Na and K and not permeable to cytoplasmic anions
Term
Electrical potential
Definition
a voltage difference across the plasma membrane due to unequal distribution of ions selective permeability of membrane and Na/K pump has the "potential" to cause a flow of ions
Term
constantly open
Definition
are always open and allow ions to move in and out of the cell as long as the solute fits through the channel opening
Term
gated ion
Definition
these channels open in response to signals
Term
ligand gated
Definition
open in response to chemicals attaching to them (ex: ligand-gated Na channels on junctional folds of NMJ)
Term
voltage gated
Definition
open in response to voltage change (ex: voltage gated Na channels on the axon hillock, forming the trigger zone
Term
threshold
Definition
a minimum change in voltage across the plasma membrane (-55mV) that can open voltage gated Na and K channels and generate an action potential (nerve signal)
Term
absolute refractory period
Definition
absolutely no stimulus will trigger an action potential
Term
relative refractory period
Definition
only a strong stimulus will trigger an action potential
Term
Diameter
Definition
a larger diameter will make an action potential travel faster down the axon, as it offers less resistance
Term
Myelin
Definition
an axon with myelin sheath will transmit an AP faster than an unmyelinated axon, as the signal can jump over areas of the myelin sheath
Term
Presynaptic neuron
Definition
has vesicles with NT which is released in response to an action potential
Term
Postsynaptic neuron
Definition
has receptors for the NT secreted by the presynaptic neuron
Term
synaptic knob
Definition
swelling at the end of telodendria, has vesicles with NT
Term
Voltage-gated Ca channel
Definition
allow Ca++ to enter the axon terminal and be available for the exocytosis of NT
Term
Synaptic cleft
Definition
space between synaptic knob and postsynaptic cell, part of ECF
Term
Receptors
Definition
on the postsynaptic cell of the synapse to attach the neurotransmitter
Term
synaptic knob
Definition
the axon terminal is the end of the axon, looks like a swelling, holds vesicles with NT, allows for transmitting chemical signals throughout the body
Term
Excitatory Cholinergic synapse
Definition
this is a synapse in which acetylcholine is the main neurotransmitter. Ach is seen in NMJ, where it is responsible for activating skeletal muscles.
Term
Inhibitory GABAergic synapse
Definition
this synapse uses y-aminobutyric as neurotransmitter. GABA opens ligand gated Cl- channels that hyperpolarize the postsynaptic cell. Hyperpolarization takes a cell away from the threshold, thus the cell is inhibited and the synapse is called inhibitory
Term
Excitatory postsynaptic otential (EPSP)
Definition
graded depolarization, will bring normal Vm closer to the threshold. Neuron is more likely to fire, so neuron is excited
Term
Inhibitory postsynaptic potential (IPSP)
Definition
graded hyperpolarization, will bring a normal Vm farther away from the threshold. Neuron is less likely to fire, so neuron is inhibited
Term
Temporal summation
Definition
ONE presynaptic neuron stimulates the postsynaptic neuron multiple times within a brief period of time. All these stimulations are added.
Term
Local potentials
Definition
caused by opening of ligand-gated channels, are graded, are reversible, travel short distances, are decremental, can excite or inhibit the cell
Term
Action potential
Definition
caused by opening of voltage gated channels, are irreversible; are all-or-none, travels long distance; are non decremental
Term
Excitatory
Definition
norepinephrine NE and epinephrine
Term
Inhibitory
Definition
y-aminobutyruc acid (GABA)
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