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10 Cards in this Set
- Front
- Back
What are the functions of the nervous tissue?
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1. sensing changes with sensory receptors (sensation)
2. interpreting and remembering changes (integration) 3. reacting to those changes with effectors |
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what are the 2 types of ion channels?
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1. Leakage (non-gated) channel
2. Gated channel: a. voltage-gated b. chemically-gated (ligand-gated) c. mechanically-gated |
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what are properties of leakage (non-gated) channel?
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- always open (passive)
- nerve cells have more K+ than Na+ leakage channels - therefore, membrane permeability to K+ is higher - resting membrane potential in nerve tissue is -70mV |
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what are properties of gated channel?
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they open and close in response to stimulus results in neuron excitability
1. voltage-gated channel: open/close in response to change in voltage 2. chem.-gated (ligand-gated): open/close in response to change in chemical stimuli (hormone, neurotransmitter, ion). 3. mechanically-gated channel: open/close due to mechanical stimulation (pressure, stretching, vibration) |
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what is resting membrane potential?
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= negative ions along inside of cell membrane and positive ions along the outside cell membrane.
* potential energy difference at rest is -70mV. |
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why do resting membrane potential exist?
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1. because concentration of ions different inside and outside the cell membrane
* ECF is rich in Na+ and Cl- * cytosol full of K+, organic phosphate and amino acids 2. Because membrane permeability is different for K+ and Na+. * permeability for K+ is 50-100 greater * inflow of Na+ can't keep up with outflow of K+ * Na+/K+ pump remove Na+ as fast as it leaks in |
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what are graded potentials?
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- hyperpolarization= membrane becomes more negative
- depolarization= membrane becomes more positive (less negative) |
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what are local potentials?
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- local disturbances in membrane potential
- aka. graded potential, caused by depolarizing of inside plasma membrane - depolarization decreases potential across cell membrane due to opening of gated Na+ channels |
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Local Potential vs action potential
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- local potential are graded (vary in magnitude depending w. stimulus strength)
- local potentials a decremental (get weaker the farther they spread) - local potentials are reversible once K+ diffused out of cell - local potentials can either be excitatory/inhibitory (causing it to hyper-polarize) |
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How do graded potential arise?
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1. From source of stimuli:
- mechanical: pressure at the ion channels - chemical: neurotransmitter at ligand-gated ion channels 2. Graded/post-synaptic/ receptor/generator potential: - ions flow via ion channels and change membrane potential locally - amount of change varies with strength of stimuli 3. Flow of ions (current) creates local change only |