The Neuron Flashcards

Structure of neurons and chemistry at rest

1
Q

What is another name for the cell body?

A

The soma

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2
Q

What is the name of where the cell body joins the axon?

A

Initial segment/ Axon Hillock

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3
Q

What are collaterals of the neuron?

A

Branches from axon; more collaterals are present closer to end of the neuron = more influence

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4
Q

What are processes?

A

Long extensions

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5
Q

What is the myelin sheath?

A

Layers of modified plasma membrane, comprised of Glial cells

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6
Q

What cells are the myelin sheath comprised of in the PNS?

A

Schwann cells

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7
Q

What cells are the myelin sheath comprised of in the CNS?

A

Oligodendrocytes

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8
Q

What direction do afferent neurons run in?

A

Towards CNS; are sensory neurones

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9
Q

What part of the afferent neurons is in the CNS?

A

Central process (axon) enters CNS

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10
Q

What parts of the afferent neurons are in the PNS?

A

Cell body and peripheral process (dendron) are in PNS

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11
Q

What direction do efferent neurons run in?

A

Away from CNS; are motor neurons

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12
Q

What parts of the efferent neurons are in the CNS?

A

Cell body and its dendrites are located in the CNS

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13
Q

What part of the efferent neurons is in the PNS?

A

Axon is in the PNS, extended peripherally

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14
Q

Where are interneurons located?

A

Within the CNS

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15
Q

What are interneurons?

A

Relay neurons; signal changers/integrators; process information

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16
Q

What does the number of interneurons indicate about the complexity of the required action?

A

More interneurons in a pathway indicates increased complexity of action

17
Q

What is the ratio of afferent: efferent: interneurons?

A

1 afferent: 10 efferent: 200,000 interneurons

18
Q

What are the four main glial cells?

A

Oliodendrocytes, ependymal, microglia, astrocytes

19
Q

What are oliodendrocytes?

A

Make up the myelin on axins

20
Q

What are ependymal cells?

A

Line fluid-filled cavities; regulate production and flow of CSF

21
Q

What are microglia?

A

Macrophage-like cells which perform immune function for nervous system

22
Q

What are astrocytes?

A

Regulate extracellular fluid composition, especially at the end of the neuron, by removing K+ and NTs around the synapse; Form blood-brain barriers at capillary walls to protect neuron; Metabolically sustain neurons by providing glucose and removing ammonia; Guide neurons as they migrate to destination, and stimulate neuronal growth in embryos

23
Q

What is polarity?

A

Intracellular charge

24
Q

What is value?

A

The potential difference

25
What is electrical potential?
The attraction of opposite charges if not separated by a barrier
26
What is the resting membrane potential?
Voltage difference between inside and outside of cells; -70mV
27
How is an electrostatic gradient created?
Intracellular is polarised due to having lower +ve charge
28
How is a concentration gradient created?
Ionic imbalance between inside and outside of cell
29
What does the membrane potential depend on?
Depends on concentration gradients and membrane permeabilities of Na+ and K+
30
What is the overall effect of concentration and electrostatic gradients on Na+ and K+?
Na+: both pull in | K+: concentration gradient pushes out, electrostatic pulls in
31
How is the K+ equilibrium potential reached?
K+ diffuse down concentration gradient out of cell when K+ channels open; P.d. is created as excessive positive charge is present in extracellular fluid due to Na+ and K+; K+ flux influenced, and less positive charge inside cells pulls K+ back in, creating electric potential; when fluxes due to concentration and electrical gradients become equal, membrane potential is same as the K+ equilibrium potential for that ion; no net movement of K+
32
What does the NERNST equation describe?
Magnitude and direction of equilibrium potential is different for different ions and depends on concentration gradients
33
What is the NERNST equation?
Eion = 61/Z log ([out]/[in])
34
What is the order of membrane permeability to the significant ions?
Cl- > K+ > Na+ >> proteins-
35
What is the largest contribution to the membrane potential?
Generated largely from K+ movement out of cell down concentration gradient, making inside more negative than positive (but is not equal to K+ equilibrium potential, although much closer than to Na+ equilibrium potential)
36
How does Na+ neutralise the effect of some K+ moving out?
A small number of Na+ channels are channels are open in resting state, allowing Na+ into cells
37
What is the function of the Na+/K+ ATPase pumps?
Maintain concentration gradients, by moving 3Na+ out and 2K+ in; create small electrogenic effect by a small negative potential (electrogenic pumps); contribute directly to membrane potential; balance ion leakage through open channels down concentration gradients