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38 terms

Nervous Tissue - S&E

STUDY
PLAY
CNS
Brain and spinal cord enclosed in bony coverings
PNS
nerve = bundle of axons in connective tissue
Sensory (afferent) divisions
Going to CNS
Motor (efferent) divisions
CNS to effectors that divides into the ANS and Somatic motor division
Sensory (afferent) neurons
Detect changes in body and external environment
Info transmitted into brain or spinal cord
Interneurons
Most abundant, bring info between afferent and motor, connect afferent and efferent
Motor (efferent) neuron
Sends signals out to muscles and gland cells
Excitability (irritability)
Ability to respond to changes in the body and external environment called stimuli
Respond electrically
Cell body
Perikaryon = soma
Single, central nucleus with large nucleolus, cytoskeleton of microtubules and neurofibrils
Dendrites
Projections for receiving signals
Axon
Arising from axon hillock for rapid conduction
Oligodendrocyte
Form myelin sheaths ONLY in CNS
Ependymal cells
produce CSF (cerebral spinal fluid)
Microglia
(macrophages) formed from monocytes
Neuroglial Cells
support cells for neurons
Neuroglial tumor
Brain cancer
Astrocytes
Most abundant glial cells
- contribute to Blood Brain Barrier (BBB) and regulate composition of brain tissue fluid
Schwann
Cells make myelin in the PNS
Node of Ranvier
Gaps between myelin segments
Trigger Zone
Initial segment (area before 1st schwann cell) and axon hillock
Speed of Nerve Signals
Large, myelinated fibers > small, myelinated fibers > small, unmyelinated fibers
Regeneration of Peripheral Nerves
Occurs if soma and neurilemmal tube is intact
Types of Nerve Injury
1. Laceration
2. Evulsion - worst prognosis
3. Compression - Best prognosis
Resting Membrane Potentials
~-70mV inside the cell comparing to outside the cell
- electrolytes such as Na+ and K+ pump in/out to maintain the equilibrium
Local Potentials
1. Occurs on a part of the neuron when that part has been stimulated
2. They are graded and decremental (it gets weaker as spread out more)
3. Reversible, work like a dimer
Action Potentials
Electrical information found on axon, only be found within an axon and it will only occur if that trigger zone said it should occur
Characteristics of AP
1. All-or-nothing
2. Always be the same, if it occurs, it occurs all the way
like a light switch
3. Irreversible
Absolute Refractory period
Axon cannot have another action potential
Relative Refractory period
Action potential/axon can make another action potential, but the stimulus for that to occur has to be greater than normal
Purpose of Refractory Period
Preventing back-fire of the conduction, so the electrical msg only go down one direction
Saltatory Conduction
Myelinated fibers insulate the fibers, make the skips down, only the nodes of Ranvier conduct down
Neuron use other chemicals as neurotransmitters
Acetylcholine
Amino acid neurotransmitters
Monoamines
Neuropeptides
Excitatory postsynaptic potentials neurotransmitters
Glutamate and Asparate
Increase the mV
Inhibitory postsynaptic potentials
GABA and Glycine
Decrease the mV
Temporal Summation
Single synapse receives many ESPS's in short time
Spatial Summation
Single synapse receives many EPSP's from many cells
Converging circuit
Taking msg from a whole lot different nerve cells and stimulate the axon hillock
Diverging circuit
Same nerve cells spreads out to many different nerves