Chapter 6 - Focus area Flashcards
Parts of neuron
Should name dendrites, cell body, initial segment, axon collateral, axon, and axon terminals
Types of glial cells in PNS. What does each do?
Satellite cells, and schwann cells. Satellite cells = support cells. Schwann cells form myelin sheath, and excrete neurotrophic factors (growth factors)
What are sections without myelin called on axon?
Nodes of Ranvier
What is special about oligodendrocytes in terms of what they myelinate?
Myelinate several sections on axons, and on different axons
Describe nerve regeneration, and by aid of what types of cells does this occur?
When axon in PNS is severed:
- Distal part of axon degenerates. Aka axon segment that is separated from the cell body degenerates, and is phagocytosed
- Part of axon still attached to the cell body gives rise to a growth cone (regeneration tube).
- Tube releases chemicals that attract growing axon.
- Tube guides regrowing axon to synaptic site
List the following on the figure: microglia, oligodendrocyte, ependymal cells, astrocyte, and neuron. Descirbe what each of the glial cells do in the CNS.
Oligodendrocytes - form myelin sheaths in the CNS
Microglia - acts as immune system - macrophage like cells that perfrom immune functions, and may also contribute to synapse remodeling and plasticity
Astrocyte - helps regulate composition of extracellular fluid in the CNS by removing potassium ions, and neurotransmitters around synapses. Also stimulates formation of tight junctions b/w the cells that make up the walls of capillaries found in the CNS (BBB).
Ependymal cells - line the fluid-filled cavities within the brain, and spinal cord. Regulate the production and flow of cerebrospinal fluid.
Descirbe the distribution of major mobile ions across the plasma membrane of a typical nerve cell? Na+, Ca2+, Cl-, and K+
- Ca2+ has higher extracellular concentration outside about 1mmol/L, and inside about .1mmol/L. So there is a tremendous gradient, but doesn’t really influence ion concentration. AKA won’t change RMP.
- May ask how action potential may be affected in decreased Na+, increased K+, etc. But, if I increased concentration gradient, I typically – when voltage-gated channels open - that ion will travel down concentration gradient faster.
- For overall health of individual if I change intracellular K+ a bit it would be ok, but if I change the extracellular concentration from 5 to 7, then probably not going to be ok. If I only have a small amount then changing amount wil lhave a larger influence. Cookie example.
- Increased extracellular K+ levels result in depolarization of the MP. http://biology.stackexchange.com/questions/10519/what-is-the-effect-of-extra-cellular-potassium-concentration-on-heart-rate-and-c
Na+/K+ Pump critical for maintaining ________, but does not send _______.
RMP, but does not send action potential
Explain the following: what does it mean for a cell to be polarized? Overshoot? Depolarization? Repolariation, and hyperpolarization?
Graded potential size…KHAN academy video. What is graded potential decay?
Ions are acted on by electrical and diffusion forces, so they disperse in opposite directions. Graded potential weakens as it expands.
Explain sequence of events of an action potential
Explain refractory period and inactivation gate
Na+ channels, spontaneously and rapidly leads to their inactivation. At the peak of the action potential, all Na+ channels become inactivated. When Na+ channels are inactivated, they cannot be immediately opened again (see figure on Na+ channel inactivation). Recovery from inactivation is a time- and voltage-dependent process, and full recovery usually takes about 3-4 ms. Therefore, it takes about 3-4 ms for all Na+ channels to come out of inactivation in order to be ready for activation (opening) again. The period from the initiation of the action potential to immediately after the peak is referred to as the absolute refractory period (ARP) (see Figs. 1 and 2). This is the time during which another stimulus given to the neuron (no matter how strong) will not lead to a second action potential. Thus, because Na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials. The absolute refractory period takes about 1-2 ms.
Label these parts, and what is a synapse?
Synapse is a place of communication for two neurons that operate sequentially
What happens when an action potential reaches the terminal? Aka mechanisms of neurotransmitter release. Steps:
- Action potential reaches terminal
- Voltage-gated Ca 2+ channels open
- Calcium enters axon terminal
- Neurotransmitters are released, and diffuse across synaptic cleft
- Neurotransmitters bind to postsynaptic receptors
- Neurotransmitter is removed from synaptic cleft in three ways
What does calcium do in the axon terminal? What is the function of SNARE proteins? And what proteins does calcium interact with, and how does this promote neurotransmitter release?
where are vesicles loosely docked prior to action potential?
- calcium activates procesesses that lead to fusion of docked vesicles with the synaptic terminal membrane.
- snare proteins - prior to the arrival of an action potential, vesicles are loosely docked in the active zones by the interaction of a group of SNARE proteins
- when calcium enters, it interacts with a separate family of proteins associated with the vesicle, synaptotagmins, triggering confirmation change in SNARE complex that leads to membrane fusion and neurotransmitter release
Describe different pathways, with neurotransmitters and receptors. Which receptors always have an excitatory response, which ones have both excitatory or inhibitory? What can NE bind to?
List cholinergic receptors, and adrenergic receptors.
Alpha receptors are always excitatory, beta receptors are excitatory or inhibitory.
Nicotinic receptors are always excitatory, muscarinic receptors can be either ^.
NE can bind to many receptors (adrenergic receptors: alpha, beta, sub classes of both of these)
