Lectur 3,4

Question 1

What are the 2 primary functions of neurons?

Answer 1

1.) rapid transmission of information from specific sources to selected targets: done via action potentials
2.) The integration of information / electrical activity from many sources

Question 2

Anatomical structure of neurons?

Answer 2

Basis structure →
- cell body
- dendrites
-Axon
-Axon terminal

Question 3

Define dendrites?

Answer 3

Receive info from other neurons

Question 4

Define cell body

Answer 4

Contain nucleus & most cell organelles

Question 5

Define axon hillock?

Answer 5

Information is collected by dendrites is integrated generating an action potential

Question 6

Define axon ?

Answer 6

Conducts action potentials away from the cell body

Question 7

Define axon terminal

Answer 7

Synapses with target cell

Question 8

Define neurotransmitters?

Answer 8

The release of chemicals substances

Question 9

The neuronal membrane at ‘rest’?

Answer 9

Cell is at rest = not generating an impulse / AP
Resting neurone →cytosolic side of plasma membrane has a negative electrical charge
Steady difference in electrical charge across membrane is called resting membrane potential ( RMP)

Question 10

Define solutes?

Answer 10

Dissolved materials that con move across cell membrane and epithelia
Electrolytes → charged species: Na t k+ .
Conc of potassium ions is higher inside the cell vs outside whereas sodium & chionde Ians are more concentrated..

Question 11

What does the phospholipid bilayerdo?

Answer 11

Separates ICF from ECF: forms a barrier
Water soluble ions
Membranes are selectively permeable to water, small molecules and ions pass through “special “ proteins

Question 12

Define channel protein?

Answer 12

Ion channels: proteins assemble to form a pore
Ion selectivity
Gating
Ion pumps → nat/ki atlases

Question 13

What does a carrier protein?

Answer 13

Used for glucose transport

Molecule binds to carrier
Carrier changes shape & molecule passes through

Question 14

What is passive transport mechanism?

Answer 14

Transport ↓ the concentration gradient, or facilitated diffusion ( via channel/ carrier protein )
Can carry material only in direction of equilibrium

Question 15

Define active - transport mechanism?

Answer 15

Transport against conc gradient; requires energy
→ primary & secondary
→ can carry material in direction opposing eqm

Question 16

Movement of ions across membrane?

Answer 16

Direction of movement →
1.) concentration of gradient
Net movement of ions from a , region of high to a region of low concentration (down a conc gradients )
2.) charge of ions or molecule ( electrical gradient)
“Opposite charges attract like charges repel “
Electrical potential (V) reflects diff in charges
3.) The membrane potential (mv )
Inside surface of cell membrane is always negative compared to outside

Question 17

What is neuronal resting membrane potential (RMP)?

Answer 17

Membrane potential: voltage across the national membrane.at rest inside neuron surface is electrically negative vs outside
Equilibrium potential: potential at which tendency of an ion to move ↓ its conc gradient is exactly balanced by the membrane potential0
Result: net movement of ion ceases → when electrochemical forces are equal & opposite

Question 18

The Nernst equation?

Answer 18

Con calculate the equilibrium potential for a given ion

Question 19

What does generating an RMP depend on?

Answer 19

1.) differences in conc of sodium & potassium both inside & outside of cell
2.) differences in the permeability of the plasma/ cell membrane to these ions

Question 20

What is the sodium-potassium pump ?

Answer 20

an ion pump that breaks down ATP in the presence of internal Na+
-Chermical energy relaesed drives the pump :exchanges internal Na+ for external K+ both pumped against their concentration gradient (ACTIVE TRANSPORT -needs energy)
-> ensures K+ is concentrated inside and Na+outside ->pump maintains both K+ and Na+ gradients-critical for brain function

Question 21

Establishing the ionic-concentration gradients:role of sodium -potassium pump?

Answer 21

1.)Outside of the cell :High Na+ conc low K+conc
3Na+ and 1 ATP bind to the protein pump
2.)Hydrolysis of ATP phosphorylates the pump protein which then changes its shape .Inorganic phosphate (Pi) binds to the pump.
3.)shape change-releases Na+ outside the cell enabling K+ to bind to pump
4.)Release of Pi returns the pumpto its original shape releasing K+ to the cells interior and once again exposing yhe Na +binding sites-repeats cycle

Question 22

Relative ion permabilties ?

Answer 22

at rest -membrane is highly permeable to K+(leak channels) also seady leak of Na+ into cell
-Neuronal membrane is permeably different ions helps explain RMP (-65mV)
RMP can be calculated-Goldmans equation

Question 23

What is the K+ efflux ?

Answer 23

neuronal membrane is higly permeable to K+ becuase of the membrane leak K+ channels (major contributor to RMP)
k+ions move down their concentration gradient to the outside of the cell->leaves the inside of the neuron -ve charged

Question 24

What experiment showed the existance of voltage-gated ion channels ?

Answer 24

Hodgkin and Huxley (1949)
experiment on Squid axons revealed the existence of voltage gated ion channels and their critical role in the gneration of AP
-during AP membrane is more permeable to Na+ than K+

Question 25

After membrane potential gated ion channels?

Answer 25

gated in channels open/close under certain conditins -chemically (ligand) gated ion channels e,g)NaChR,s -Voltage gated ion channels Activation can lead to depolarisation /hyperpolarisation

Question 26

What are the 2 properties of Action potential ?

Answer 26

1.)Na+ current :inward,depolarising current 2.)K+ current :outward ,hyperpolarising current APs are sudden transcient large chains in Vm

Question 27

How are APs generated ?

Answer 27

By opening and closing of voltage gated Na+ and K+ channels Voltage gated Na+ channels are oncentrated atthe axon hillock .Sufficient depolarisationcauses an AP PASSESthrugh threshold

Question 28

How are voltage gated channels controlled?

Answer 28

Na channels → activation m-gate Inactivation h-gate K+ channel → activation n-gate (Slide 34 )

Question 29

Course of AP?

Answer 29

1.) leaky K + channels create the resting potential Gated channels are closed 2.) some voltage gated Nat channels open depolarising the cell to threshold 3.) additional voltage gated Nat channels activation gates open → A rapid spike depolarisation _ AP 4.) Na channels inactivation gates close, gated K t channels open replanting & even hyper polarising the cell 5.) all gated channels close. The cell returns to its resting potential. Nat inactivation gates reopen

Question 30

What are the "ups" & "downs" of an AP?

Answer 30

If threshold is exceeded → AP → "all or nothing" Nat channels open or inactivated a 2nd AP cannot he elicited → absolute refractory period ( ARP) K+ channels open um is hyperpolarised so only stronger dep. Stimulus con elicit 2nd AP relative refractory period (rrp)

Question 31

Myelin: Nodes of Ranvier

Answer 31

CNS: oligodendrocytes myelinate axons PNS:Schwann cells myelinate axons Nodes of Ranvier :Interruptions in myelin sheath

Question 32

Factors affecting conduction velocity ?

Answer 32

Velocity-varies Axon Diameter:The larger the diameter the faster the propagation -important for invertebrates Myelination: Provides insulation = important for vertebrates Nodes of Ranvier :Saltatory conduction AP jump node to node -current faster &farther

Question 33

Define synapse ?

Answer 33

Junction between a nerve ending (axon terminal )& target cell -Presynaptic terminal -Postsynaptic terminal -Synaptic Cleft

Question 34

Define Synaptic Transmission ?

Answer 34

Process by which nerve cells (neurons) pass information onto target cells 2 -Chemical transmission :chemical neurotransmitters diffuse across the synaptic cleft POSTSYNAPTIC -Electrical transmission:pre and postsynaptic elements are electrically connected via junctions

Question 35

Define structure of CNC chemical synapse ?

Answer 35

draw or explain

Question 36

Chemical synaptic transmission ?

Answer 36

1: Action potential arrives sat axin terminal 2.)Na+ channels open depolarisation causes voltage gated Ca 2+ channels to open 3.)Ca 2+ enters the cell and triggers fusion of acetylcholine vesicles with preresynaptic membrane. 4.)Acetylcholine molecules diffuse across the synaptic cleft and bind to receptors on the postsynpatic membrane 5.) When receptors bind acetylcholine they open the cation channels and depolarise the postsynaptic membrane 6.)Spreading depolarisation fires an action potential in the postsynaptic membrane 7.)AChE breaks dwon ACh snd the components are taken back up the presynaptic cell.Acetylcholine and vesicels are recycled

Question 37

Define Excitatory neurotransmiiters ?

Answer 37

eg.)glutamate ,acetylcholine -Increase nerve activity -cause depolariation -initiate excitatory post-synaptic potentials (ESPS) more likely for AP to be prod

Question 38

Defie Inhibitory neurotransmitters ?

Answer 38

Decrease nerver activity Cause hyperpolarisation Initiate inhibitory post synaptic potentials (IPSP)

Question 39

Define Summation ?

Answer 39

The balance of ESPS and ISPS coverging on to a neuron at any given moment - SYNAPTIC INTEGRATION

Question 40

Define Dendrites

Answer 40

axo dendritic synapses

Question 41

Defien soma

Answer 41

Axo-somatic synapses

Question 42

Other axons :

Answer 42

Axo axonal synapses

Question 43

What is the Excitatory synapse ?

Answer 43

When the presynaptic activity increases the excitability of the postsynaptic neuron

Question 44

How are ESPS graded ?

Answer 44

In intensity and outlast the APs that generated them in the first place .Thus they can be temporally and spatially summated.

Question 45

Define Spatial Summation ?

Answer 45

Occurs when several excitatory postsynaptic potentials (ESPS) arrive at the axon hillock simultaneously .

Question 46

Define Temporal Summation ?

Answer 46

means that postsynaptic potentials crerated at the same synapse in rapid succession can be summed

Question 47

Explain GABergic syanpse ?

Answer 47

explain