Term
| Why are nerves and muscles considered to be "excitable" tissues? |
|
Definition
| Muscles and nerve cells are considered to be "excitable" because they're capable of transmitting action potentials after electrical or chemical stimulation sufficient to depolarize the plasma membrane. |
|
|
Term
| What is "membrane potential"? |
|
Definition
| The difference in electrical potential or voltage that appears across the membranes of most cells. |
|
|
Term
| What is the resting membrane potential? |
|
Definition
| The voltage that exists across a cell membrane when the cell is not transmitting electrical signals; polarity is such that the inside of the cell is negative with respect to the outside. |
|
|
Term
| Which three ions are the major contributors to the resting membrane potential? |
|
Definition
K+ Potassium
Na+ Sodium
Cl- Chloride ions |
|
|
Term
| Which solution is Na+ in the greater concentration? |
|
Definition
|
|
Term
| In which solution is K+ in the greater concentration? |
|
Definition
|
|
Term
| Which structures create and maintain the resting membrane potential? |
|
Definition
| The sodium/potassium pumps actively help contribute, while "leaky" and ion gated channels passively contributes to RMP. |
|
|
Term
| What is the resting membrane potential voltage for a typical nerve cell? |
|
Definition
| -65 mV to -85 mV (usually -70 mV). |
|
|
Term
| Differentiate between a nerve cell and a glial cell. |
|
Definition
| Glial cells lack axon and dendrites and they cannot generate action potentials. They support nerves. They surround neurons, hold them in place, provide nutrition, help maintain homeostasis, provide electrical insulation, destroy pathogens, regulate neuronal repair, and removal of dead neurons, and participate in signal transmissions on the nervous system. |
|
|
Term
| What are the major parts of a neuron? |
|
Definition
| Cell body, dendrites, axon hillock, myelin sheath, axon terminal, node of Ranvier. |
|
|
Term
| What part of the neuron has the lowest threshold? |
|
Definition
|
|
Term
| Name and describe the 3 functional classes of neurons of the nervous system |
|
Definition
1. Afferent neuron-generates AP from the sensory receptors; long axon; found mainly in the PNS.
2. Interneuron-found entirely within the CNS.
3. Efferent Neurons-generate AP from the CNS; has a long peripheral axon in the PNS. |
|
|
Term
| Which structures allow ions to move across a membrane quickly? |
|
Definition
|
|
Term
| What is the primary difference between a leaky ion channel and a gated ion channel? |
|
Definition
| Leaky channels are always open, whereas gated ion channels must be opened via voltage, thermal, chemical, or mechanical stimulation. |
|
|
Term
| Describe the 4 types of gated ion channels discussed in class. |
|
Definition
1. Voltage gated-membrane potential.
2. Chemically gated-neurotransmitter.
3. Mechanically gated- physical deformation of receptors.
4. Thermally gated-local temperature. |
|
|
Term
| What is the driving force for ion movement through open gated channels? |
|
Definition
| They will diffuse or passively move down their electrochemical gradient. |
|
|
Term
| What are the biggest differences between a graded potential and an action potential? |
|
Definition
| Graded potentials-travel short distances and AP travels farther. GP voltage intensity decreases with distances, whereas AP does not. GP is sub-threshold, whereas AP passes the threshold. GP is directly proportional to the triggering event, whereas AP impulses due to crossing the threshold. |
|
|
Term
| Name and describe in detail what happens during the 4 polarization states during the generation of an action potential. |
|
Definition
1. Depolarization-membrane potential becomes less negative than the RMP.
2. Repolarization- membrane returns to RMP after depolarization.
3. Hyperpolarization-membrane becomes more polarized (more negative) than the RMP.
4. ?? |
|
|
Term
| What is the membrane threshold and why is it important? |
|
Definition
| Membrane threshold is an excitable cell, the critical value of the membrane potential to which the cell must be depolarized in order to trigger an action potential. |
|
|
Term
| What could initiate an action potential? |
|
Definition
|
|
Term
| What ensures than an AP is sent in only 1 direction along an axon? |
|
Definition
| The refractory period ensures one-way travel of an AP. |
|
|
Term
| In which direction do the action potential signals flow? |
|
Definition
| From the cell body, axon hillock, along the axon, and to the axon terminal. |
|
|
Term
| What is the all or none phenomenon? |
|
Definition
| The phenomenon is a reference to the fact that a threshold must be crossed in order for an AP to manifest. If a cell depolarizes slightly, but does not cross the threshold it will not produce an AP. |
|
|
Term
| What does the AP frequency indicate? |
|
Definition
| The AP frequency indicates the stimulus intensity. |
|
|
Term
| Which factors determine the velocity of nerve conduction? |
|
Definition
1. Degree of myelination.
2. Axon diameter. |
|
|
Term
| What are the differences between contiguous and salutatory conduction? |
|
Definition
Contiguous-continuous; lack of myelination; gray matter.
Salutatory-myelination; white-fatty matter; tissue is white. |
|
|
Term
| What cells form the myelin sheath in the PNS? |
|
Definition
|
|
Term
| What cells form the myelin sheath in the CNS? |
|
Definition
|
|
Term
| What does the myelin sheath function to do? |
|
Definition
| The myelin sheath functions to protect the axon, electrically insulate fibers, and increase nerve impulse transmission. |
|
|
Term
| What are the nodes of Ranvier? |
|
Definition
| They are the gaps in the myelin along axons. |
|
|
