Term
| What cells produce the myelin sheath? |
|
Definition
oligodendrocytes in the CNS
Schwann cells in the PNS |
|
|
Term
|
Definition
| a cluster of neuron cell bodies |
|
|
Term
| What is the function of astrocytes? |
|
Definition
| nourish neurons and form blood-brain barrier |
|
|
Term
| What do ependymal cells do? |
|
Definition
| produce cerebrospinal fluid which physically supports the brain |
|
|
Term
|
Definition
|
|
Term
| How does the Na+/K+ ATPase function? |
|
Definition
| It uses ATP to maintain resting membrane potential by moving 3 Na+ ions out of the cell for every 2 K+ ions into the cell. Inside of the cells is more negative. |
|
|
Term
| Why is the inside of the cell more negative than the outside? |
|
Definition
| The cell membrane is more permeable to potassium ions and because they have a higher concentration in the cell they will move down their gradient out of the cell. Becuase potassium is positively charged and leaving the cell it results in a more negative interior. |
|
|
Term
| What is summation in regard to action potentials? What kinds are there? |
|
Definition
| It is the additive effect of multiple signals. Temporal summation is multiple signals occuring close to each other in time. Spatial summation has additive effects based on the number and location of incoming signals. |
|
|
Term
| What happens when the threshold is reached? |
|
Definition
| Voltage gated sodium channels open in the membrane allowing sodium ions to rush in down their electrochemical gradient into the cell making the cell more positive. This depolarizes the membrane. Sodium channells will become inactivated (deinactivation only occurs at resting potential). Potassium channels now open and potassium rushes out of the cell down its electrochemical gradient causing the cells to repolarize and even hyperpolarize causing a refractory period. |
|
|
Term
| What are the two kinds of refractory periods? |
|
Definition
Absolute - no amount of stimluation can cause another action potential
Relative - greater than normal stimulation can cause an action potential
|
|
|
Term
| How does an action potential propogate down the axon? |
|
Definition
| The axon hillock depolarizes causing the surrounding area to depolarize as well and this causes a chain reaction all the way down the axon. |
|
|
Term
| What happens when the action potential reaches the nerve terminal? |
|
Definition
| The depolarization causes voltage-gated calcium channels to open. The influx of calcium triggers fusion of the membrane-bound vesicles with the cell membrane which causes exocytosis of neurotransmitter. |
|
|
Term
| white matter vs grey matter |
|
Definition
| white matter is myelinated and grey matter is not |
|
|
Term
| Where do sensory and motor neurons enter and leave the spinal cord, respectively? |
|
Definition
Sensory neurons enter dorsally and their cell bodies are found at the dorsal root ganglion.
Motor neurons leave ventrally. They synapse within the spine. |
|
|
Term
| What is a primary difference between autonomic and somatic nervous system regarding number of neurons utilized? |
|
Definition
| The autonomic nervous system uses two neurons, pre- and postganglionic, to communicate to the peripheral nervous system. The pre neuron's soma (cell body) is found in the CNS and its axon travels to the post neuron in the PNS which then affects target tissue. The peripheral motor neurons go straight from the spinal cord to the muscle without synapsing. |
|
|
Term
| What are the two kinds of reflex arcs and how do they work? |
|
Definition
| Reflex arcs are neural circuits that control reflexive behavior. Monosynaptic reflex arc has only a sensory neuron that synapses with a motor neuron. A polysynaptic reflex arc has at least one interneuron between the sensory and motor neurons. |
|
|
