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Flashcards in Problem 2 Deck (40)
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1

Structural Division of a Neuron

- Dendrite
- Soma
- Axon
- Axon terminals

2

Dendrite
(Input Zone)

receives information from other neurons across synapses

3

Soma
(Integration Zone)

Combines / Integrates the received information

Contains cells nucleus

4

Axon
(Conduction Zone)

Carries the cells electrical signal (AP) away from soma

leads away from cell body

5

Axon Collaterals

multiple branches at end of axon

6

Axon Terminals
(Output Zone)

transmit neurons activity across synapses to other cells

7

Neuron

basic unit of the nervous system

1. receives inputs from other cells
2. integrates the inputs
3. then distributes processed information to other neurons

8

Multipolar Neuron

many dendrites, single axon

--> most common

9

Bipolar Neuron

single dendrite, single axon

10

Unipolar Neuron

axon branches in two directions

one side has the dendrite, other has the collaterals and terminals

11

Motor Neuron

governs movement

part of CNS

12

Sensory Neurons

carry information from the periphery to other neurons

13

Interneurons

perform functions of the brain

14

Astrocyte

Type of glial cell

involved in formation of new synapses

15

Oligodendrocyte

Type of glial cell

Myelinates in CNS

16

Schwann Cell

Type of Glial cell

Myelinates in PNS

17

Node of Ranvier

small uninsulated patches of axonal membrane

18

Microglial cell

removes debris / lesion from injured or dead cells

Type of glial cell

19

Ion channel

tubelike pore that allows ions of a specific type to pass through the membrane

20

Precondition of Resting Potential

-65mv

- neuron contains a majority of anions (-) which cannot exit the cell

- intra - and extracellular fluid are separated by cell membrane

- intracellular --> more negatively charged ions
(Anions- & K+)
extracellular --> more postively charged ions (Na+ & Cl- ions)

- neuron is studded with K+ Channels

21

Process of Resting potential

At rest, membrane is much more permeable to Potassium (K+ Ions)

1. K+ ions leave interior through K+ channels
--> build up of negative charges inside cell

2. Concentration gradient pushes K+ ions out of extracellular f.
+ electrostatic pressure pulls K+ ions in the intracellular fluid

--> Equilibrium is reaches

3. Further movement of potassium into the cell is matched by movement out of cell

22

Maintenance of the Resting Potential

- little but steady influx of Na+ through leakage current leads to decrease of negative potential

- K+ ions leaving the cell leads to high loss of potassium

--> Sodium potassium pump pumps 3 Na+ out of call and 2 K+ into call ( always 1 cation (+) is pumped out of intracellular fluid.

23

What is an Action Potential ?

Very brief, but large changes in a neurons polarization that arise at the axon hillock
--> it is then propagated at high speed along the axon

24

Depolarization

I. Phase of an AP

Cell becomes depolarized to threshold levels

--> channels shape changes
--> voltage gated Na+ Channels open
--> Na+ ions are allowed through

Rapid change from -65mv to +40mv

25

Repolarisation

II. Phase of an AP

1. Axon membrane contains voltage - gated potassium channels (K+) which require more depolarization to open
--> open later than Na+ channels

2. K+ channels (that are always open) + Voltage-gated K+ channels
= High permeability for K+ ions

3. Na+ permeability decrease at the same time
--> Na+ channels close

4. High number of cations left cell
=> Membrane potential is negative again


26

Sodium

Natrium (Na+)

27

Anion

negatively charged ions

Cl-

28

Cations

Positively charged ions

K+, Na+

29

Hyperpolarisation

III. Phase of an AP

1. K+ channels close
--> number of K+ ions that left is so high that membrane potential is lower than resting potential

2. Axonal membrane is refractory ( unresponsive ) to a second stimulus

30

Absolute refractory phase

Threshold --> Repolarisation

- Na+ channels are unresponsive
--> no amount of stimulus can induce a new AP