Problem 2 Neurons and potentials

Question 1

Soma/Cell body

Answer 1

contains the nucleus and much of the machinery for the processes of the cell

Question 2

Dendrites

Answer 2

recipients of the messages from another neuron (its synapses) – input zone

Question 3

Axon hillock

Answer 3

junction between axon and cell body

Where action potentials emerge

Question 4

Axon

Answer 4

carries information (message = action potential) from cell bodies to terminal buttons (one-way street) – conduction zone

Question 5

Myelin sheath

Answer 5

fatty insulation around many axons that speed up the transmission of electrical impulses thus convey information more rapidly

Question 6

Oligodendrocytes

Answer 6

(glia cells) with extensions (rich in myelin) that wrap around the axon (CNS)

Question 7

Schwann cells

Answer 7

which can also guide axonal regeneration (helps to build the myelin covering) is a glia cell (PNS swims in your body)

Question 8

Nodes of Ranvier

Answer 8

the gaps between sections of myelin

 Where ion channels are located (APs)

Question 9

Terminal Buttons

Answer 9

endings of the axon that release neurotransmitters into the synaptic gap (pre-synapse) – output zone

Question 10

Multipolar neuron/Motor neuron

Answer 10

Most common in CNS

From the neuron to the action (movement)

Question 11

Bipolar neuron/inter neuron

Answer 11

o	PNS (transmit sensory information to CNS)
o	Analyses the information

Question 12

Unipolar neuron/Sensory neuron

Answer 12

o PNS (transmit sensory information to CNS)
o Only one axon leaves the cell body and divides into two or more branches
o Pressure heat senor
o From the body to the brain

Question 13

Multipolar Interneuron

Answer 13

Integrate neural activity within a single brain structure

Question 14

Nucleus

Answer 14

contains DNA

Question 15

Cytoplasm

Answer 15

internal (liquid) substance containing organelles

Question 16

Endoplasmic reticulum

Answer 16

serves as storage reservoir and channel for transporting chemicals through cytoplasm

Question 17

ribosomes

Answer 17

translate DNA to real material

Question 18

Mitochondria

Answer 18

extract energy from nutrients
o	Aerobic (oxygen-consuming) energy release

Question 19

Golgi-complex

Answer 19

connected system of membranes that packages molecules in vesicles for delivery to buttons

Question 20

Microtubules

Answer 20

responsible for rapid transport of material throughout neurons

Question 21

Membrane structure

Answer 21

 Composed of a lipid bilayer (two layers of fat molecules)
 Embedded in the lipid bilayer are molecule/proteins
o Channel proteins: certain molecules can pass through them
o Signal proteins: transfer a signal to the inside of the neuron when a certain molecule binds to them on the outside of the membrane
- Hydrophobic is the inside
- Hydrophilic is the outside

Question 22

Diffusion

Answer 22

passive movement of molecules along a concentration gradient

Question 23

Osmosis

Answer 23

diffusion through a semipermeable membrane from an area of low concentration to an area of high concentration

Question 24

Selective permeability

Answer 24

membrane that is selective in terms of which molecules can pass and which can’t

Question 25

Within the cell

Answer 25

more K+ and A- (organic anion is to big to fit through the membrane) keeps the outside always a bit negative

Question 26

Outside the cell

Answer 26

mainly Na+ and Cl-

Question 27

Na+ channels (sodium ion channels)

Answer 27

are closed during resting potential (voltage gated channel: like to open around -55mV) o Substantial pressure for natrium ions to enter the resting neurons

Question 28

K+ channels (potassium channels)

Answer 28

o K+ pressure to leave cell due to concentration gradient but also to enter cell due to electrostatic pressure -> STEADY STATE

Question 29

Sodium-potassium-pump

Answer 29

maintains resting potential!! o At the same rate that K+ leaks out they are actively transported in (2 in) o At the same rate that Na+ leaks in they are actively transported out (3 out)

Question 30

II. Depolarisation/hyperpolarisation

Answer 30

 Caused by neurotransmitters binding to postsynaptic receptors  Decrease resting potential (excitatory postsynaptic potential – EPSP positive input) o Increase likelihood that neuron will fire  Increase resting potential (inhibitory postsynaptic potential – IPSP negative input) o Decrease likelihood that neuron will fire  Threshold for action potential at -55mV (all-or-none response)  Whether a neuron fires or not depends on the balance btw IPSPs and EPSPs reaching its axon (spatial & temporal summation)

Question 31

III. Depolarisation – begin of action potential

Answer 31

 As soon as threshold of excitation is reached sodium channels in membrane open  Na+ comes in but lots of K+ channels are blocked  Rapid change in membrane potential from -70mV to +40mV

Question 32

IV. Peak

Answer 32

 Sodium channels become refractory (absolute refractory period): become blocked and cannot open again until membrane once more reaches its resting potential o Responsible that APs only travel one way

Question 33

V. Repolarisation

Answer 33

K+ continues to leave cell causing membrane potential to return to resting level  More Na+ channels close, more K+ channels open  Hyperpolarisation due to gradual closing of K+ channels

Question 34

VI. Return to resting potential

Answer 34

 Sodium-potassium transporters remove Na+ from cell and retrieve the leaked K+

Question 35

VII. Resting potential

Answer 35

 Relative refractory period: axon is able to fire again but only when applying higher than normal levels of stimulation o Thus rate of firing is related to the intensity of the stimulation (APs always the same but the rate depends – rate law)

Question 36

Orthodromic conduction

Answer 36

from cell body to buttons

Question 37

Antidromic conduction

Answer 37

towards cell body