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chapter 11/12
muscular system/nervous tisse
81
Biology
Undergraduate 2
02/26/2012

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Term
Origin -
Insertion -
Body -
Definition
- The site of muscle's attachment to the more stable bone.
- The site of a muscle's attachment to the more moveablebone.
- The fleshy part of a muscle located between the origin andinsertion of a muscle.
Term
Leverage:
Definition
- A mechanical advantage. The force created to achievemovement.
Term
Lever -
Definition
A rigid structure that can move around a fixed point(called the fulcrum).
Term
Effort -
Definition
The force which causes movement. (i.e. the muscle)
Term
Load =
Definition
Resistance
- The force which opposes movement.
Term
Agonist =
Definition
Prime Mover
- The muscle that contracts to produce the desiredmovement.
Term
Antagonist -
Definition
The muscle that stretches and yields to the agonist.
Term
Synergist -
Definition
The muscle(s) that prevent unwanted movement and aid inthe movement of the agonist.
Term
Fixator -
Definition
The muscle(s) that stabilize the origin of the agonist.
Term
Fixator -
Definition
The muscle(s) that stabilize the origin of the agonist.
Term
Central Nervous System (CNS)
Definition
1. Brain
2. Spinal Cord
B. Peripheral Nervous System
1. Somatic Nervous System
2. Autonomic Nervous System
a. Sympathetic Nervous System
b. Parasympathetic Nervous System
3. Enteric Nervous System
Term
Cell Body =
Definition
Soma = Perikaryon
- contains one centrally located nucleus
- contains Nissl Bodies, Rough Endoplasmic Reticulum
Term
Dendrites
Definition
- extensions from the cell body that receive signals(then transmits them towards the nucleus
Term
Axon
Definition
- extension from the cell body that transmits signalstowards the synapse
Term
Axon Hillock
Definition
- region where the axon joins the cell body
Term
Axoplasm and Axolemma
Definition
- cytoplasm and cell membrane of the axon
Term
Axon Collaterals
Definition
- branches that come off of the axon
Term
Synaptic End Bulbs
Definition
- the end of the axon that contacts the synapse
- vesicles that contain neurotransmitter can befound in these structures
Term
Synapse
Definition
- the site of communication between the axon and itsend organ
Term
Slow Axonal Transport
Definition
- the mechanism that transports axoplasm fromthe cell body towards the synapse
- material travels at a rate of 1 to 5 mm/day
Term
Fast Axonal Transport
Definition
- moves material along the axon in bothdirections, ex. synaptic vesicles
- material travels at a rate of 200 to 400mm/day
Term
Myelin Sheath
Definition
- a lipid/protein coating that surrounds the axonsof certain neurons
- the region between the myelin sheaths are calledthe Nodes of Ranvier
- these structures speed up nerve impulsetransmission
Term
Gray Matter -
Definition
a collection of unmyelinated neuron
Term
White Matter -
Definition
a collection of myelinated neurons
Term
Multipolar Neuron
Definition
- has several dendrites and one (or more) axon
- found in the Brain and Spinal Cord
Term
Bipolar Neurons
Definition
- has one axon and one dendrite
- associated with the eye and ear
Term
Unipolar Neurons
Definition
- the dendrite and axon leave the cell body from one area
- associated with sensory neurons
Term
Neuroglia =
Definition
Glia = Glial cells
- cells that support the function of the Nervous System
Term
Neuroglia - types:
Definition
1. Astrocytes
2. Oligodendrocytes
3. Microglia
4. Ependymal cells
5. Schwann cell
6. Satellite cells
Term
Astrocytes
Definition
- located in the CNS
- provide nutritional support and the proper chemicalenvironment to Neurons
Term
Oligodendrocytes
Definition
- in CNS
- produce myelin sheaths
Term
Microglia
Definition
- in CNS
- mobile macrophage
Term
Ependymal cells
Definition
- in CNS
- line the ventricles of the Brain
- produce Cerebral Spinal Fluid (CSF)
Term
Schwann cell
- in PNS
- produce myelin sheaths
Definition
Term
Neurolemma =
Definition
the outermost layer of the cell, contains thenucleus
Term
Satellite cells
Definition
- in PNS
- nutritional support to Neurons
Term
Resting Membrane Potential (RMP) -
Definition
the electrical potential across the axon membrane, this is produced by the different ions located on each side of the membrane
- outside is positive, inside is negative
Term
Extracellualr vs. intracellular
Definition
- extracellular area has more Sodium and Chloride ions
- intracellular area has more potassium ions, phosphates, andamino acids
Term
RMP
Definition
is approximately equal to -70 mV (i.e. more negativeintracellularly)
Term
Voltage Gated Channels
Definition
- located in the axolemma
- open and close in response to changes in voltage
- ex. Voltage Gated Na+ Channels
Voltage Gated K+ Channels
Term
Sodium/Potassium ATPase Pumps
Definition
- located in axolemma
- takes care of ion (i.e. Na+ and K+) leakage across the axonmembrane
Term
Depolarization
Definition
- voltage gated Na+ Channels open in response to a stimulus,the membrane voltage becomes more positive as thepositive ions rush inside the membrane
- depolarization originates at the Axon Hillock
Term
Repolarization
Definition
- recovery of the RMP
Term
Action Potential
Definition
= Depolarization + Repolarization
- the electrical signal (impulse) that is propagated down theaxon
Term
Threshold Stimulus
Definition
- any electrical stimulus that is strong enough to initiate anaction potential
Term
All-or-none principle
Definition
- the initial stimulus must reach threshold before an actionpotential is generated (there is no partial activation ofan action potential)
- this initial electrical stimulus will quickly dissipate ifthe threshold stimulus is not achieved
Term
Events Associated With An Action Potential:
Definition
1. Threshold Stimulus is reached (-55mV)
2. Voltage Gated Sodium Channels open initiating Depolarization
3. Repolarization begins
4. Hyperpolarization occurs
5. RMP is restored by the Sodium-Potassium ATPase Pumps
Term
Voltage Gated Sodium Channels open initiating Depolarization
Definition
- sodium rushes inside the axolemma
- the membrane voltage goes to 0 mV, then to approx. +30 mV(more positive inside the membrane)
- Voltage Gated Sodium Channels close at +30 mV
Term
Repolarization begins
Definition
- with the Voltage Gated Sodium Channels closed, the action ofthe Sodium-Potassium ATPase Pumps begin to restore theproper ion concentrations along the axolemma
- the Voltage Gated Potassium Channels are now fully opened(they respond slowly to the Threshold Stimulus)
- the voltage across the axolemma becomes more negative (backto 0 mV, then to -90 mV)
Term
Hyperpolarization occurs
Definition
- Hyperpolarization = membrane voltage is below RMP (-70 mV)
- this occurs because the Voltage Gated Potassium Channels areslow to close (positive charges are still leaking out ofthe axon)
Term
Refractory Period
Definition
- The period of time in which an excitatory cell cannotgenerate another Action Potential
Term
Absolute Refractory Period
Definition
- The Voltage Gated Sodium Channels need to reach a restingstate before they can be reactivated.
= The period of time from activation of Voltage Gated SodiumChannels until they reach a resting state.
Term
Relative Refractory Period
Definition
- During hyperpolarization of the axon membrane, a larger thanthreshold stimulus is needed to activate an actionpotential
Term
Propagation =
Definition
Conduction
- as sodium rushes inside the axolemma, adjacent Voltage GatedChannels are activated (achieve Threshold Stimulus); theprocess of activating adjacent channels continues downthe axon towards the synapse
Term
Continuous Conduction
Definition
- Propagation of a nerve impulse in a step by stepdepolarization and repolarization of adjacent areas ofthe axolemma
- associated with nonmyelinated neurons
Term
Saltatory Conduction
Definition
- the Action Potential is moved along the myelinated portionof the axolemma, passing from one Node of Ranvier to thenext until the impulse reaches the synapse
(the signal is passed along the myelinated regions via anionic current)
- associated with myelinated neurons
Term
The effect of axon diameter.
Definition
- The rate of nerve impulse transmission is determined by thediameter of the axon and the presence (or absence) ofmyelin
Term
A Fiber:
Definition
- myelinated
- largest diameter axon (5 - 20 micrometers)
- short absolute refractory period
- fastest nerve impulse transmission (27 - 280 mph)
Term
B Fiber:
Definition
- myelinated
- axon diameter is smaller than A fibers (2 - 3micrometers)
- absolute refractory period is longer than A fiber
- slower impulse transmission than A fiber (32 mph)
Term
C Fiber:
Definition
- unmyelinated
- smallest axon diameter (0.5 - 1.5 micrometers)
- longest absolute refractory period
- slowest impulse transmission (1 - 4 mph)
Term
Electrical Synapse
Definition
- ionic current spreads through Gap Junctions in adjacentcells
- are faster than chemical synapses
- ex. Cardiac muscle
Term
Chemical Synapse
Definition
1. A nerve impulse stimulates a vesicle (located in the axonterminus) to release neurotransmitter into the synapticcleft (i.e. the space between the Presynaptic andPostsynaptic Neurons)
2. The neurotransmitter diffuses across the synaptic cleft andinteracts with a specific receptor site on thePostsynaptic Neuron
- one way transfer of the signal
- the neurotransmitter must be deactivated shortly afterinteracting with the receptor
3. The Postsynaptic Neuron generates a graded potential that istransmitted to the Axon Hillock
- 2 primary effects on the Postsynaptic Neuron:
Term
Excitatory Postsynaptic Potential (EPSP)
Definition
= depolarization (positive ions move into the Dendrite)
- this adds to the threshold stimulus (i.e. makes it morepositive)
Term
Inhibitory Postsynaptic Potential (IPSP)
Definition
= hyperpolarization (negative ions flow in or positiveions flow out of the Dendrite)
- a stimulus that takes away from the threshold stimulus(i.e. makes it more negative)
Term
Deactivation/Removal of Neurotransmitter from the SynapticCleft
Definition
- this prevents continuous stimulation of PostsynapticNeurons (End Organs)
1. Diffusion from the synaptic cleft
2. Enzymatic degradation
- ex. Acetylcholinesterase deactivating Acetylcholine
3. Uptake by cells
- reuptake by the secreting neuron or a glial cell
Term
Summation:
Definition
- occurs at the axon hillock
- integration of the EPSP's & IPSP's until a thresholdstimulus is reached (this will rapidly dissipate)
1. Spatial Summation
2. Temporal Summation
Term
Spatial Summation
Definition
- the build up of graded potentials caused by several synapticend bulbs releasing neurotransmitter
Term
Temporal Summation
Definition
- the build up of graded potentials caused by only onesynaptic end bulb releasing neurotransmitter in rapidsuccession
Term
Neurotransmitter:
Definition
- chemicals essential for transmission of across the synapticcleft
Term
Acetylcholine
Definition
- can be excitatory or inhibitory
- deactivated by Acetylcholinesterase
ex. Alzheimer Disease
- progressive loss of the ability to reason and care forones self
- associated with high mortality
- caused by degeneration of ACh releasing neurons in theBrain
Term
Amino Acids
Definition
- Glutamate and Aspartate are excitatory
- Gamma Aminobutyric Acid (GABA) and Glycine are inhibitory
Term
Biogenic Amines
Definition
- modified amino acids
a. dopamine
b. serotonin
c. epinephrine, norepinephrine
Term
Dopamine
Definition
- regulates skeletal muscle tone, movement, emotionalresponses
ex. Parkinson Disease
- associated with the progressive degeneration ofDopamine releasing neurons in the Brain
- patient develops tremors, slow and uncoordinatedmovements
Term
Serotonin
Definition
- associated with sensory perception, mood control,temperature regulation, appetite, sleep induction
ex. Selective Serotonin Reuptake Inhibitor (SSRI)
- Prozac - allows serotonin to remain in thesynaptic cleft longer
Term
Prozac -
Definition
allows serotonin to remain in thesynaptic cleft longer
Term
Nitric Oxide (NO)
Definition
- thought to play a role in memory and learning
- is not produce in advance
Term
Neuropeptides
Definition
- neurotransmitter 3 to 40 bonded amino acids
- can be excitatory or inhibitory
- often associated with controlling pain and modifyingneuronal activity
ex. Endorphins, Enkephalins, Substance P
Term
Neurogenesis:
Definition
- the creation of new neurons from undifferentiated stem cells
Term
Axon Repair in the Peripheral Nervous System
Definition
- occurs in myelinated axons where the neurolemma in intact
Term
Early effects of nerve repair:
Definition
- The cell body swells
- Wallerian Degeneration occurs - the portion to the axondistal to the injury degenerates
- the proximal portion of the axon degenerates to the nearestNode of Ranvier
- Nissl bodies become granular in appearance
Term
Later effects of nerve repair:
Definition
- Schwann cells undergo mitosis to form a Regeneration tubeacross the injury site
- the axon is gradually reconstructed with in the sheath thatis left behind at a rate of 1 to 5 mm/day
- scar tissue in the "tube" of to wide of a gap will stopregeneration
- function is restored
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