Topic 2: Neurons and action potentials

Question 1

membranes

what gets through protein channels

Answer 1

outer sac
water oxygen
sodium 
chloride
calcium
potassium

Question 2

mitochondria
how energy

function
people with over and under active mitochondria or mutated?

Answer 2

powerhouse, metabolic provides energy for neuron functions

use enzymes to break down glucose into Adenosine Triposphate

over; burn fuel rapidly over heat
under; predisposed depression and pain

mutated; theory of autism

mitrochondria have some DNA (get from mum e.g mitochondrial eve)

Question 3

ribosomes

Answer 3

where protein molecules are synthesized

Question 4

endoplasmic reticulum

Answer 4

folded parallel layers
rough synthesise proteins

smooth synthesise fats
network of thin tubes that transport newly synthesized proteins from the ribosomes to other locations, some ribosomes are connected to endoplasmic reticulum

Question 5

soma

Answer 5

cell body

Question 6

dendrites

Answer 6

receive signals
not as long
can have dendridic spines

Question 7

axon

Answer 7

transmit signals

can be much longer up to 1m (sciatic nerve), have constant radius, covered in myelin

myelin is made of 80% fat, protective and increases speed of AP. MS is inflammation scars and legions CNS myelin, causing cog decline (memory), motor problems, visual problems

not all axons are myelinated, some delayed pain signals.

myelin makes white matter white, somas etc is grey matter

At the end of an axon are terminal buttons/bootons (pre-synaptic terminal, axon terminal)

tiniest neruons don’t have them

Question 8

Motor neuron v sensory neuron shape

Answer 8

motor; soma in spinal chord, has axon going out all the way to muscles (has also dendrites going out from the soma to receive info from nearby cells)
efferent neurons

sensory; has a long axon with the soma in the middle of it somewhere, at the end of the axon is specialized fibers for sensing (touch etc)
afferent neurons

Question 9

nodes of ranvier

Answer 9

myelin interruptions for potentiating signal

Question 10

afferent v efferent v intrinsic

Answer 10

towards (e.g. every sensory neuron is afferent to the rest of the nervous system)
away (e.g. every motor neuron is efferent from the nervous system)

instrinsic or interneuron is when a cells dendrites and axons are contained within a structure e.g. the neurons of the thalamus. they join sensory (afferent) and motor (efferent) messages. Often found in the spinal chord

Question 11

variation within cell structure
purkinje
bipolar

Answer 11

purkinje; many widely branching dendrites, in the cerebellum, inputs from 200’000 cells

wheras bipolar neurons in retina, only 2 other cells input, small few branches

Question 12

Glia

Answer 12

all the other parts of the nervous system
outnumber neurons in the cerebral cortex
while neurons outnumber glia in the cerebellum
overall numbers are roughly equal

Question 13

astrocytes

Answer 13

star shaped glia
wrap around the axons of closely functionally related axons preventing influx of chemicals, taking up and releasing ions and transmitters to synchronize the axons of multiple cells for rhythmic activation patterns e.g. breathing

also can dilate blood vessels for increased nutrients to active areas

Question 14

microglia

Answer 14

immune system
remove viruses and fungi from the brain
proliferate after brain damage removing damaged cells

remove weak unused synapses

use process called phagocytosis engulf and consume!

cause collateral damage, implicated in alsheimers
oli astrid and schwann are macroglia crew, mini wants in

Question 15

oligodendrocytes and swann cells

Answer 15

oli in brain and spinal chord (CNS) and Shwann in PNS build myelin
provide nutrients

Question 16

migration of neurons is by the…

Answer 16

radial glia (after embryonic development, differentiates into neurons astrocytes and oli’s)

Question 17

blood brain barrier and viruses

Answer 17

regular cell virus response is to signal the immune system to destroy the cell which will be replaced. Nervous system cells don’t get replaced so the blood brain barrier prevents viral infections

exceptions; rabies and syphilis
and viruses that get contained but may come back eg chicken pox and herpes

built of endothelial cells which form the walls of blood vessels, are packed much tighter on the BBB

also keeps out fuel and amino acids necessary for building proteins, need ATP active transport to do it

area postrema at medulla of brain has weaker BBB, this is responsible for vomiting, sensitive to toxins making vomm quickly

Question 18

blood brain barrier and nutrients 4 ways

small

lipid based

protein channels in endo wall

active transport

Answer 18

small uncharged particles can get through e.g. oxygen CO2
fat dissolved can get through vitamins A & D and psychotropic drugs
speed of effect of drugs dependent on how readily it dissolves in fat (heroin and nicotene readily disolve in fat) dopamine doesn’t dissolve in fat, L-dopa does and once inside can be catalysed by enzymes into dopamine for parkinsons sufferers

endothelial cell wall has protein channels to let through water

active transport - energy using protein mediated, glucose amino acids purines choline some vitamins iron

insulin and others also cross although we don’t yet know how

Question 19

BBB and health

Answer 19

alsheimers, endothelial cells shrink (harmful chemicals in)

brain cancer problem - chemo cant cross

Question 20

energy use in most cells vs in neurons cancer and testes cells

Answer 20

most use carbs and fats, neurons use glucose

metabolizing glucose requires oxygen
the brain is 2% of humans body weight but uses 20% of its oxygen and 25% of its glucose

its because glucose is the only nutrient that crosses the BBB in large quantities

you need B1 to use glucose, alcoholism leads to B1 deficiency which leads to brain cell death Korsakoff’s syndrome)

Question 21

Bipolar axons

Answer 21

1 axon and 1 dendrite either side of the soma, most often found in visual and auditory systems

Question 22

unipolar axons

Answer 22

1 axon, going either side of the soma which is somewhere in the middle of the axon. one side receives sensory information and the other side transmits it towards the CNS.

found in the somatosensory system

Question 23

multipolar

Answer 23

most common CNS neuron
typical neuron diagram
many dendrites attached to the soma, with a long axon coming of the other side

Question 24

micro-tubules

Answer 24

a structure within neuron, tracks to transmit stuff between the soma and terminal buttons

this is called axoplasmic transport needs ATP, its a kind of active transport.

Question 25

2 types of axoplasmic transport

Answer 25

anterograde and retrograde

Question 26

anterograde axoplasmic transport

john

Answer 26

carries proteins, vesicles of neuro transmistters and other vital things from the soma to the terminal buttons, carried by kinisin proteins
5m/day

Question 27

retrograde axoplasmic transport

fred

Answer 27

carries thing like waste from the terminal buttons towards the soma, carried by dynein proteins
rabies, tetinis, polio, herpes, all transmitted into soma by the dynein doing retrograde axoplasmic transport
2.5m/day

the kinisn and dynein can compete in direction if not all conditions are right for transport in one direction or another

Question 28

marker of alsheimers

Answer 28

is neurofibulary tangles.
caused by tau proteins (part of microtubles) have there structure changed by excessive phosphate ions.
this interupts axoplasmic transport, leading to cell death.
axoplasmic transport is a vital function of neurons

Question 29

cytoskeleton & cytoplasm

Answer 29

The cytoskeleton is a network of filaments and tubules that extends throughout a cell, through the cytoplasm, which is all of the material within a cell except for the nucleus. It is found in all cells, though the proteins that it is made of vary between organisms.

cytoplasm is the fluid jelly, holds organelles

Question 30

actin

Answer 30

laneways off the main track(microtubules) of the cytoskelitin

there is also interfilaments

Question 31

neurofiliments

Answer 31

threads that form a matrix that maintain shape of neuron and support the membrane

Question 32

golgi aparatus

Answer 32

smooth plate shaped membranous sac that packages up proteins etc into little sacs called vesicles
many in the cell body to transport neurotransmitters in vesicles down to the buttons
some are in the buttons, making vesicles out of scrap button wall bits!

also makes lisosomes that have enzymes to break down and recycle waste products

Question 33

types of proteins

Answer 33

enzymes - chemical reactions, synthesise and break down stuff

peptide hormones - regulate body functions eg insulin

transporter proteins - haemoglobin

tubulin - struture of stuff

antibodies - immune proteins

all proteins are made of chains of amino acids, up to 50 with 20 essential aminos acids (from food)

Question 34

cell membranes

details about active and passive transport

what determines what gets through a channel

Answer 34

made of phospho-lipid molecules while hydrophilic heads on the outer edge on the membrane, exposed to the water
and hydrophobic tails(inside of membrane)

In most cases, the movement of molecules in and out of the cell is controlled. Some very small molecules can cross freely (e.g. nitric oxide [NO], a soluble gas recently recognised as being important in learning). However, many ions cross the cell wall via channels found in the membrane’s protein molecules. These channels are called ion channels, and they are specific to that ion (e.g. potassium channels). Ion selectivity is determined by:

the size of the molecule
the electrical charge of the molecule
in the hydration of the channel.

Ion channels are a form of passive transport as the cell does not use its own energy supplies to transport molecules into or out of the cell. These channels can be permanently open (‘free passive transport’) or open only when certain conditions are present in the membrane (‘gated passive transport’).

Gated channels can be chemically gated, which means that they can only open when a specific molecule binds to the transport molecules. Alternatively, they can be voltage gated and open when certain electrical properties are present in that region of the cell wall.

There are also active transport mechanisms provided by membrane protein molecules. These require energy in the form of ATP to pump ions in and out of the cell. The most important active transport mechanism is the sodium-potassium pump.

Using these transport mechanisms, cells create electrical differences across the cell membrane (i.e. a membrane potential). Neurons, however, go one step further than other cells and exploit this electrical difference to transmit information.

Question 35

proteins use in the cell

Answer 35

channels
transporters
signal takers

Question 36

protein synthesis TTT

Answer 36

transcription; DNA is copied into mRNA
translation; the mRNA exits nucleus through pores and goes to ribosomes and tells them to make the proteins (which they make out of amino acids)
transport; newly synthesized proteins are carried by the axoplasmic transporter kyeine

Question 37

resting membrane potential

Answer 37

no excititory (making the cell more positive, + charged neurotransmitters) or inhibitory (making the cell more negative, - charged neurotransmitters) messages being received.

the resting potential is the difference in electrical potential between the inside and outside.
inside is -70mV more negative than outside in resting potential state
this is POLARISED

Question 38

membrane potential

Answer 38

electrical potential difference between inside and outside of the cell.

Question 39

Polarized de-polerised and hyper-polerised

Answer 39

Polarized: inside of the cell is very negative (net compared to outside)

de-polerised: when the inside becomes more positive (it goes up to +40mV)

hyper-polerised: refracts down to lower than -70mV (-75mV)

Question 40

ions that effect electrical charge

Answer 40

Na+ sodium
K+ potassium
Ca++ calcium
Cl- chlorine (this is what the lecturer wrote but it might be cloride Cl- which has an added negative ion making it Cl-, and wanting to form a compound)

Question 41

whats the I-C and E-C composition in resting state

Answer 41

intracellular fluid has higher organic anions (-) and potassium (K+)
ion channels leak potassium out, keeping the overall charge negative

extracellular fluid has more chloride (Cl-) and sodium (Na+) overall positive charge (a lot of sodium)
(remember that the extracellular is saltwater NaCl in there)

Question 42

ion channels types

Answer 42

free (can pass any time)
or gated (only certain things)
voltage opened (+40mV) e.g. for sodium it needs to be 40+ and then boom 
chemical opened (only specific ions can go through)

Question 43

sodium potassium pump

Answer 43

requires ATP

Question 44

passive transport in ions moving across cell membrane

Answer 44

Diffusion and electrostatic pressure

diffusion
kinetic energy - molecules bump around and distribute evenly
sodium will spread into the cell where there is a lower concentration. this changes the membrane potential towards less negative

electrostatic pressure
cations (+) and anions (-) electrolytes when dissolved split into these

sodium is a cation

cl is an anion

opposite charges attract, same charges repel

Question 45

concentration gradient v membrane gradient v electrical gradient

Answer 45

concentration gradient is the high and low concentration within a fluid and diffusion happening

electrical gradient also known as polarization is the difference between the inside and outside of the cell

Question 46

hypertonic
hypotonic
isotonic

Answer 46

high concentration
low concentration
equal concentration

Question 47

axon hillock

Answer 47

dendrites pick up signal, it goes to the soma, the soma connects to the axon at the axon hillock. enough to reach the threshold of excitation means the action potential will be propagated.

Question 48

rate law of action potentials

Answer 48

higher frequency rates of action potentials are for stronger stimulus. higher frequencies also increase likelihood of nearby neuron being triggered

Question 49

threshold of excitation

Answer 49

-55mV at the axon hillock

Question 50

saltatory conduction

Answer 50

nodes of ranvier allow quicker potentiating, ions jump from node to node (saltatory conduction) so not all channel opening is needed
also the sodium-potassium pump only need to be at the nodes, saving energy (cause they use ATP)

Question 51

osmosis

Answer 51

Osmosis is the spontaneous net movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, in the direction that tends to equalize the solute concentrations on the two sides.

Question 52

diffusion v osmosis

Answer 52

The main difference between the two is that diffusion can occur in any mixture, even when two solutions aren’t separated by a semipermeable membrane, whereas osmosis exclusively occurs across a semipermeable membrane.

in our case osmosis refers to the movement of water