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73 Cards in this Set
- Front
- Back
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How do cells communicate?
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By sending and receiving signals
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What are the two types of communication?
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Chemical signal
Electrical signal |
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Where are chemical signals secreted?
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Directly between cells or into the ECF
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What cells have the potential to respond to chemical signals?
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Target cells
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What are some examples of electrical signals?
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Nervous System, think of neurons
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Who do electrical signals communicate with? What does it stimulate?
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Other neurons, stimulate muscles and glands
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What does dendrite mean? Where are they found?
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Dendrite means tree/branching
Found on end of neuron. |
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What do dendrites do?
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Can act as sensory receptor or receive signals from other neurons.
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Do dendrites have one or many branches?
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many.
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What is the cell body? What does it include?
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Enlarged part of the nerve cell.
Nucleus and organelles = normal cell. Metabolism occurs here. |
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Function of cell body?
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Integrative area, receives inputs from dendrites and determines if signal is passed on.
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What is the axon hillock, what does it do?
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Area between cell body and axon, where action potential is generated.
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After action potential is generated, where does it go?
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To the axon
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What is the axon known as? What does it do?
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Conductive region, transmits AP away from the cell body.
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What are the branches on the axon called?
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Axon collateral
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How many axons does a nerve cell have?
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one, but may be very long.
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What are the bulbs on the end of the axon? What do they do?
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Terminals of the axon, transmit impulse to next neuron or to effector via release of neurotransmitters into the synapse.
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What can the axon also provide to modulate signaling?
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Negative feedback.
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What is the small gap between neuron and effector?
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Synapse
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What is a membrane potential caused by?
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Caused by the difference in electrical charge between intracellular and extracellular fluid.
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What does a positive membrane potential mean?
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Greater distribution of positive charges on the inside versus the outside of the cell.
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What component of the cell membrane provides separation of charge?
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The lipid portion
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What are leak channels? What does it do?
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Integral proteins, allows movement of specific ions through, based on size, charge and shape.
Establishes resting membrane potential by leaking more k+ out of the cell than Na+ |
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Are leak channels passive or active?
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Passive
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Leak channels are always ___________.
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Open
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What is the mv for resting membrane potential?
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-70
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Resting membrane potential results in a __________ charge.
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Negative charge difference of Na+ and k+ ions between the inside and outside of the cell.
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What cells are excitable?
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Nervous and muscle
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What does voltage mean?
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Separation of charges across membrane
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What does irritability mean?
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Ability to respond to a stimulus and convert it to an electrical impulse.
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What does conductivity mean?
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Ability to transmit the impulse down neuron or across muscle.
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What is the role of the nervous system?
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Generate and conduct AP along axon.
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Where are most AP generated?
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Axon hillock and axon
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Look at the mechanism of the Na/K Pump!!
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Look at the mechanism of the Na/K Pump!!
2-2 Review diagram |
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When does an activation gate (na) open?
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When membrane voltage occurs.
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When does an inactivation gate (na) close?
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After a certain amount of time has passed.
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What are the steps of the Na/K gate during AP?
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1) Resting state, -70mv
2) Depolarization, -55 to set off this. Na rushes in, changing charge to +30. 3) Repolarization, after time Na gate inactivates (based on time), K+ channels open, K+ flows out of cell. (makes it more negative again). 4) Hyperpolarization, goes lower then -70. 5) Resting potential is reestablished. 2-2 Na/K Review |
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What causes depolarization?
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Sensory stimulus
Neurotransmitter released from axon or previous neuron. (focusing on NT) |
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Neuron transmitters often involve what kind of channel?
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Ligand-gated ion channel,
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What does ligand-gated ion channel do? Where are they found and what do they do?
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Opens in response to binding of ligand (NT).
Found on dendrites and cell body. Causing change in resting membrane potential from -70 to -55. Starting a stimulus. |
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What happens if something is depolarized?
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Action potential occurs in neuron
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If threshold is not reached, there is no __________________
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Action potential
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What is the refractory period of the action potential?
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Time it takes to restore resting membrane potential so that another action potential can occur.
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What are the two periods of refractory period?
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Absolute refractory period
Relative refractory period. |
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When is the absolute refractory period? Can AP be set off?
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From depolarization through most of repolarization and the start of hyperpolarization. CANNOT generate another AP yet.
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When is the relative refractory period? Can AP be set off?
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Occurs from end of hyperpolarization until resting membrane potential is reestablished.
Another AP CAN be generated, given strong enough stimulus. |
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How many action potentials can happen per second?
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200-300
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How is action potential transmitted down the axon?
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1) Start of depolarization at axon hillock
2) Na+ travels laterally inside of the cell. 3) Opens more voltage gated Na+ channels in adjacent segment. 4) Leads to depolarization of that area. 5) repeats |
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Is action potential one way or two way movement? Why?
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One way movement, because of the refractory period. Previous segment has just depolarized and cannot depolarize again.
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What is the all or none theory (action potential).
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If stimulus is too low, none part of the theory. Must reach -55 to cause AP.
Once you reach -55, all part of the theory. |
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Are ion cycles identical or different in amplitude?
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Identical
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How do we vary intensity of stimulus if AP is always identical?
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Change in frequency.
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What is the number of action potentials per second called?
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Hertz
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What is frequency of action potential limited by?
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Absolute refractory period.
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How long does absolute refractory period last?
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1-2 milliseconds.
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Which axons conduct action potential faster? Small or large diameter? Why?
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Large, due to less resistance to ion passage.
Don't have to rub against lipid membrane to move laterally. |
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What is myelination?
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Tightly wound cell membranes around the neurons axon
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What does myelination do?
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Acts as insulation, lipid in cell membrane prevents electrical transmission and limits amount of membrane contact with ECF.
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What conducts action potential faster? Myelinated or unmyelinated axons. Why?
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Myelinated
Less spots of depolarization makes it faster. |
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The method action potentials travel along a myelinated axon is called? What does this mean?
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Saltitory conduction, increases rate of conduction.
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What two things effect action potential conduction speed?
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Diameter of axon (larger is faster)
Unmyelinated and myelinated (myelinated is faster) |
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What is a disease that results in demyelination?
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Multiple Sclerosis.
Autoimmune disease. Antibodies destroy myelin. Slows action potentials. |
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What can number of synapses effect?
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How quickly the signal is passed. Because diffusion across synapse is slower then electrical transmission
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Whats faster, electrical transmission or chemical diffusion?
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Electrical transmission
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Which is faster? Monosynaptic or polysynaptic?
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Monosynpatic
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What types of drugs can bind to voltage-gated Na channels and keeps gates closed?
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Local anesthetics (benzocaine, lidocaine, procaine)
Antiepileptic (dilantin) Tetrodotoxin (from puffer fish) Saxitoxin (from dinoflagellates associated with red tide) |
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What do local anesthetics do? Examples.
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Prevent signals from reaching brain = decreases sensory perception.
Benzocaine, lidocaine, procaine, ice. |
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Hot or cold temperatures slow down AP?
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Cold, put ice on injured finger to anesthetize pain.
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What does an antiepileptic agent do? Example?
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Phentoil (Dilantin), Tetrodotoxin from puffer fishm Saxitoxin.
Decreases seizures by decrease electrical transmission Tetrodotoxin causes paralysis by decreasing electrical transmission. Saxitoxin, dinoflagellates associated with red tide. Gets into shell fish and also cause respiratory failure. |
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What does high extracellular fluid levels of potassium mean ( > 5mM)? What symptoms can you have if this happens?
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Called Hyperkalemia. Prevents natural flow of K ions out of cell via leak channels during resting membrane potential. Results in more positive resting membrane potential.
Resting membrane potential now -60mv instead of -70. AP happens more easily. Muscle weakness --> Paralysis; kidney malfunction --> failure; cardiac dysrhythmia --> asystole (heart stops). |
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At what point does high extracellular fluid levels of K+ require medical attention?
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> 6.5mM.
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What happens if extracellular fluid levels of potassium are too low? What are the symptoms?
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Called Hypokalemia, decreased blood K+ concentration.
Causes more negative resting potential (-80, instead of -70). <3.5mM K+, increased loss of K+ from cell via leak channels. Symptoms: Weakness, malaise, constipation, low bp, cardiac dysrhythmia --> stroke, heart attack. |
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At what point does low potassium levels need medical attention?
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<2.5mM K+ requires medical attention.
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