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Structure of neurons include...(5)
- Myelin Sheath
- Nodes of Ranvier (Ron-Vee-Ay)
- Conducts nerve impulses away from soma
- Never more than one axon per neuron(some have none)
receive impulses from other neurons
Myelin Sheath (4)
- Insulating layer (mostly lipid) around nerve fibers, which are formed by
- neuroglia cells(Schwann Cells in PNS & Oligodendrocytes in CNS).
- Not all nerve fibers are myelinated.
- Myelinated comprise the white matter.
- Unmyelinated comprise the gray matter.
Nodes of Ranvier (2)
- Myelinated nerve fibers
- Ions can be exchanged with the ECF only with this...
Types of Neurons (4)
- Interneurons(association neurons)
- Reflex Ark
Conduct impulses toward the CNS
Interneurons (association neurons) (2)
- Entirely within the CNS
- Conduct impulses from sensory neurons to motor neurons.
Conduct impulses away from the CNS and to the effectors (muscles or glands).
Reflex Ark is an arrangement of...(3)
- sensory neurons
- motor neurons
Functions of Neurons (3)
- Excitability (irritability)
- Secretion of neurontransmitters
Nervous Tissue is specialized for...by? (2)Consists of? (2)
- Communication, by means of electrical or chemical signs
- neurons (nerve cells)
- neuroglia (glial cells)
Interior of nerve cell or any cell is...? Relative to ECF. (3)
- Negative Charge
- Requires ATP
The charge differences across the plasma membrane is...? which is about...?
- Resting Membrane Potential (RMP)
The...charge of the ion in cell.
Large anions that cannot escape cell Na+ is ...x higher concentration outside. K+ is ...x higher concentration inside.
Uneven distribution of Na+ & K+ on ... of plasma membrane pertains only to thin film of ions adjacent to the membrane surface.
Electrical events involves ions adjacent to membrane in...?
Local Potentials (3)
- Influx of Na+ diffuse for a short distance along the inside of plasma membrane
- Produce a current that travels from point of stimulation toward the cell's trigger zone; short range change
- High need of glucose and ATP energy
Characteristics of Local Potentials
- Stimulation of neuron by chemical, light, heat, mechanical distortion.
- Stimulation alters permeability of various ions thus leading to a change in resting membrane potential
- Graded-different magnitude
- Decremental-die out
Action Potential (2)
- Occur where there is high density of voltage gated channels, ex: trigger zone has 350 to 500 channels/μm2.
- Generated if local potential spreads all the way tot he trigger zone and is still strong, it can open these channels.
The action potential changes the membrane potential from -70mV (resting) to 35mV & back again to the resting membrane potential. (7)
- The action potential arrives at the axon hillock, depolarizes the membrane at that point.
- This local potential must rise to a critical voltage called threshold ~ -55mV.
- The neuron now produces an action potential.
- As potential passes 0mV the Na+ channel closes, the voltage peaks @ +35mV, as the voltage peaks the K+ channels open K+ ions exit the cell.
- Their outflow repolarizes the membrane.
- Hyperpolarization, membrane voltage drops 1 or 2mV more negative because K+ channels stay open longer than Na+ channels, so more K+ leaves the cell than the amount of Na+ entered.
- Refractory Period, for a short time, few milliseconds, after action potential, it is impossible to stimulate that region of a neuron to fire again; This is the period of resistance to restimulate.
All or Nothing Law
Action Potentials are non decremental
There are 2000 to 12000 voltage gated ion channels/μm2 at...?
The node of ranvier
In..., ions can be exchanged with the ECF only at the Nodes of Ranvier.
Myelinated nerve fibers
Impulses jumping from node to node.
(Filled w/neurotransmitters) in the pre-synaptic neuron
In the post-synaptic membrane
Cessation of signal at the synapse (3)
- Re uptake of the neurotransmitter by the pre-synaptic neuron
- Diffusion of the neurotransmitter into the extracellular fluid, where astrocytes absorb it.
- Degradation of the neurotransmitter in the synaptic cleft.
Muscle contraction (3)
- Muscle relaxation
- Molecular processes involving muscle contraction
- General structure & functions of different muscle cells
Smooth Muscles (4)
- Spindle-shaped Fiber
- Single Nucleus
Cardiac Muscles (5)
- Striated Fiber
- Single Nucleus
- Intercalated disks
Skeletal Muscles (3)
- Striated Cylindrical Fiber
- Voluntary Movement
- Myosin (thick) filaments
- Actin (thin) filaments, tropomyosin & troponin are associated w/thin filaments
- Titin (elastic) filaments
- Spinal Cord, motor neuron 1, motor neuron 2
- Neuromuscular junction
- Skeletal Muscle Fibers