task 2

Question 1

nervous system / subdivision / constituents / function

Answer 1

Can be divided into central nervous system (CNS) and peripheral nervous system (PNS)
Serves as manager of the body -> controls the functions of every other system
cells of the nervous system are of two fundamentally different types: neurones & glia cells

Question 2

neurones (or nerve cells) / function

Answer 2

specialised for the reception, conduction, transmission of electrochemical signals in the body.
each neurone is a self-contained functioning unit

Question 3

sensory neurones / function

Answer 3

Information in form of light, sounds waves, odors, tastes or contact with objects, is gathered from the environment by sensory neurons.

Question 4

motor neurones / function

Answer 4

They control contractions of muscles, which allow us to move.

Question 5

interneurones / function

Answer 5

Neurons that lie entirely within the central nervous system. Local interneurons form circuits with nearby neurons and analyse small pieces of information. Relay interneurons connect circuits of local interneurons in one region of the brain with those other regions.

Question 6

dendrites

Answer 6

Input zone = receive electrical messages from other neurons by grabbing on to neurotransmitters.
These messages are either inhibitory or excitatory in nature:
Inhibitory message – cell body will not transmit the message to the axon.
Excitatory message – cell body will send the message down the axon and pass it to other neurones

Question 7

soma (cell body)

Answer 7

Integration zone = combines the information the neuron has received to determine whether or not to send a signal of its own.
Covered by cell membrane.
Contains the nucleus.
Cell body is responsible for
Building new dendrites.
Producing protein that the other parts of the neurone needs.
contains the cell’s DNA
produces chemicals (neurotransmitter) which neurones use as signals

Question 8

axon hillock / location / function

Answer 8

Cone-shaped region at the junction between axon and cell body.
It controls the firing of the neuron – if total strength of the signal exceeds limit of the axon hillock the structure will fire signal (action potential) down the axon.

Question 9

terminal buttons / function / location

Answer 9

Small knobs at the end of an axon. When an action potential traveling down the axon reaches them, they secrete neurotransmitters into the synapse.
Terminal buttons form synapses with other neurones.
responsible for reuptake of excessive neurotransmitter

Question 10

synapse / function

Answer 10

Communication sites where neurons pass nerve impulses among themselves.
Cells are separated by thin gap – the synaptic cleft.

Question 11

multipolar neurones

Answer 11

Most common type.

Somatic membrane gives rise to one axon but to the trunks of many dendrites trees.

Question 12

bipolar neurones

Answer 12

Give rise to one axon and one dendritic tree.

Question 13

unipolar neurones

Answer 13

It only has one stalk, which leaves the soma and divides into two branches.

Question 14

intracellular fluid / constituents

Answer 14

fluid contained within cell
> A-, K+: high concentration
> Cl-, Na+: low concentration

Question 15

extracellular fluid / constituents

Answer 15

fluid contained outside cell
> K+: low concentration
> Cl-, Ka+: high concentration

Question 16

membrane potential

Answer 16

The electrical charge across a cell membrane; the difference in electrical potential inside and outside the cell. 
> composed of 3 forces: 
- diffusion 
- osmosis
- active transport

Question 17

resting membrane potential

Answer 17

membrane potential of a neurone (of the axons) is when it is not being altered by EPSP’ or IPSP’s; aka when the axons have -70mV’s.
Resting potential is created by a transport protein called the sodium-potassium pump -> makes sure that the sodium ions stay on the outside of the cells. -> Membrane is more permeable to K+

Question 18

depolarisation

Answer 18

Because the inside of the axon is negative, a positive charge applied to the inside of the membrane produces depolarization, which is the reduction toward zero, from -70mV, of the membrane potential of a cell from its normal resting potential.

Question 19

hyperpolarisation

Answer 19

neurone becomes hyperpolarised when more K+ are outside than Na+ are inside the cell
=> potential drops lower than resting potential

Question 20

action potential

Answer 20

massive nut momentary reversal of membrane potential (from about -70mV > 50mV)
> stimulus is needed in order to conduct action potential
-> when stimulus reaches a resting neurone it transmits the signal as an impulse (= action potential)
> role: electrical signals along nerves and muscle fibres are essential for communication of information to / from / within the brain

Question 21

threshold of excitation

Answer 21

The value of the membrane potential that must be reached to produce an action potential

Question 22

inhibitory postsynaptic potential (IPSP)

Answer 22

electrical charge in the membrane of a postsynaptic neurone
> caused by the binding of an inhibitory neurotransmitter from a presynaptic cell to a postsynaptic receptor
> brings a negative charge -> partial hyperpolarisation
> inhibitory because it basically guarantees that there wont be an action potential that runs along the axon
> GABA produces IPSP’s -> inhibitory

Question 23

excitatory postsynaptic potential (EPSP)

Answer 23

electrical charge in the membrane of a postsynaptic neurone
> caused by an excitatory neurotransmitter from a presynaptic cell to a postsynaptic receptor
> brings a positive charge -> partial depolarisation.
> excitatory because it makes it more likely for a postsynaptic neurone to generate an action potential
> glutamate produces EPSP –> excitatory

Question 24

sodium-potassium pump

Answer 24

uses ATP to actively pump 3Na+ out of & 2K+ into the cell
> pumps same amount of K+ ions into neurone, as the amount that moves out
> pumps same amount of Na+ ions out of neurone, as the amount that moves in
=> reason for why Na+ can stay in such high concentration in the extracellular fluid

Question 25

ion channels

Answer 25

Specialised protein molecules that allows specific ions to enter and leave cells.
> Potassium channel = always open.
> Sodium channel = not always open.

Question 26

steps of action potential

Answer 26

1. resting membrane potential
2. depolarisation
3. spike potential
4. repolarisation
5. hyperpolarisation
6. refractory period

Question 27

absolute & relative refractory period

Answer 27

Absolute refractory period:
it is impossible to trigger action potential during this period
> sodium channels are shut -> no sodium = no depolarisation = no action potential

Relative refractory period:
it is hard to trigger an action potential during this period
> period after absolute refractory period (gates are open again)
> cell is still hyperpolarised so it is hard to get it up to the threshold of excitation

Question 28

all-or-none law

Answer 28

An action potential either occurs or does not occur. Once triggered, it is transmitted down the axon to its end and always remains the same size.

Question 29

rate law

Answer 29

how certain muscle contractions occur is due to the rate of firing of an axon:
> strength of stimuli affects the rate of firing:
-> strong stimulus produces more action potentials than a weak stimulus
> high rate of firing causes strong muscular contraction

Question 30

saltatory conduction

Answer 30

action potentials only occur in nodes of Ranvier and appear to jump from one node to another along the axon
> conduction is faster
> has less degradation along myelinated than unmyelinated axons

orthodromic conduction:
> from synaptic junction or receptors along axons to their termination
antidromic conduction:
> opposite direction (towards the soma)

Question 31

summation

Answer 31

Adding up the effect of multiple stimuli, that are all individually unable to produce a response, so that together they are large enough to generate an action potential in excitable cells.

Question 32

temporal summation

Answer 32

when one presynaptic neurone releases neurotransmitters many times over a period of time
> if a stimulus comes in, then another one and so on -> those ‘bumps’ occur in rapid and close succession -> together they can reach the threshold => action potential can occur

Question 33

spatial summation

Answer 33

when multiple presynaptic neurones together release enough neurotransmitters to exceed the threshold of the postsynaptic neurone
> neurone A and B individually release insufficient neurotransmitters
> when these quantities combine, the threshold may be exceeded => action potential can occur.

Question 34

mitochondria

Answer 34

Neurone’s fuel source

produces energy needed for the neurone -> ATP

Question 35

endoplasmic reticulum & Golgi apparatus / function

Answer 35

work together with the rest of the organelles in nucleus to produce and transport protein to the various locations inside and outside the cell

Question 36

organelles

Answer 36

component of the soma that provides the cell body and nucleus control of the function of the nerve cell
tiny cellular structure that performs specific functions within a cell
embedded within the cytoplasm of eukaryotic and prokaryotic cells

Question 37

eukaryotic & prokaryotic cells

Answer 37

eukaryotic: organisms whose cells have a nucleus enclosed within membranes
prokaryotic: unicellular organism that lacks a membrane-bound nucleus, mitochondria

Question 38

neurotransmitter

Answer 38

Chemicals contained in the terminal buttons that enable neurones to communicate
fit into receptor cells on the dendrites on other neurones like a key lock

Question 39

multipolar interneurones / construction / function

Answer 39

neurones with a short axon or no axon at all 
function is to receive information from other neurones, process it and pass the integrated info on

Question 40

cytoplasm

Answer 40

internal liquid containing organelles

Question 41

nucleus

Answer 41

contains the chromatin and the genetic makeup of the organism

Question 42

Golgi complex

Answer 42

main function is the modification, sorting, packaging of proteins and lipids for either secretion or delivery to another organelle

Question 43

endoplasmic reticulum

Answer 43

organelle in cell that functions as a manufacturing and packaging system for proteins
serves storage reservoir and channel for transporting chemicals through the cytoplasm
rough ER: ribosomes attached to its surface -> synthesis of proteins
smooth ER: without ribosomes -> synthesis of fats

Question 44

ribosomes

Answer 44

small organelles that synthesise proteins
some are attached to the endoplasmic reticulum
not surrounded by membrane
produced by nucleus - dark large sphere

Question 45

microtubules

Answer 45

when proteins cannot be made on the spot and they need to be transported from one part of the cell to a different part of the cell
proteins can travel along ‘transporting channels’ called microtubules

Question 46

cell membrane / function / structure

Answer 46

composed of lipid bilayer -> two layers of fat molecules
> takes care that intracellular and extracellular space remain separated
> has molecules and proteins embedded in it:
1. channel proteins: allow certain molecules to pass through
2. signal proteins: transfer signals to inside of neurone when particular molecules bind to them on the outside of membrane

Question 47

passive & active transport in cell membrane

Answer 47

passive transport: channel enables ions to flow rapidly through membranes in a downhill direction, so channel action illustrates passive transport or facilitated diffusion
active transport: pumps are energy transducers in that they convert one from of free energy into another

Question 48

glia cells (= supporting cells) / kinds

Answer 48

oligodendrocyte (cells with several branches)
Schwann cells
astrocyte
microglia (clean-up crew)

Question 49

oligodendrocyte (cells with several branches)

Answer 49

glial cell with extensions that wrap around the axons of the neurones on the CNS
> extensions are rich in myelin -> myelination plays a role in intelligence
> each oligodendrocyte provides several myelin segments
=> disfunction: schizophrenia, bipolar disorder, tumors

Question 50

Schwann cells

Answer 50

glia cell wrapped around an axon of the nerve cells in the PNS
> similar to oligodendrocytes -> difference: they exist in PNS not CNS
> form spirals directly around the axon and the nodes of Revier lie between them and they assist in nerve transmission in the same way
> part of immune system: when nerve cell is damaged, they have ability to eat the nerve’s axon and provide protected path for new axon to fort
=> disfunction: Guillain-Barré syndrome ( autoimmune disorder in which the immune system attacks health nerve cells in PNS), Charcot-Marie-Tooth disease (= group of inherited disorders of the PNS characterised by progressive loss of muscle tissue and touch sensation)

Question 51

astrocyte

Answer 51

(astro = star)
star shaped cells, considered the largest glia cells
> form the blood-brain barrier: security system only letting in substances that are supposed to be in the brain
> regulating chemicals around neurones: neurones communicate via neurotransmitters. once a chemical has delivered its message to a cell, it waits for an astrocyte to ‘reuptake’ (recycle) it
> cleaning: they clean what is left when a neurone dies as well as the excess potassium ions
> regulating blood flow to the brain and synchronise activity of axons
=> disfunction: neurodegenerative disease (Parkinson’s, Huntington’s)

Question 52

microglia (clean-up crew)

Answer 52

smaller than other glia cells
> act as the brain’s own dedicated immune system: necessary since the blood-brain barrier isolates the bran from the rest of the body
> respond to injury or disease by charging in and taking care of the problem: clearing away dead cells or getting rid of a toxin or pathogen
-> inflammation as part of healing process
=> disfunction: when microglia becomes hyper-activated it causes too much inflammation -> Alzheimer’s disease, chronic pain, autism disorders

Question 53

axon polarisation

Answer 53

overall balance between positive and negative charges is such that inside of axon is electrically negative with respect to the outside -> axon is polarised in its resting state => resting potential

Question 54

K+

Answer 54

potassium cation 
> concentrated within the axon 
diffusion pushes it out of the cell 
> electrostatic pressure forces the cation inside the cell 
=> those opposing forces balance K+

Question 55

A-

Answer 55

organic anion

> unable to pass through membrane of the axon

Question 56

Cl-

Answer 56

chloride anion
> greatest concentration outside the axon
> diffusion pushes it inward
> electrostatic pressure pushes it outward
=> those opposing forces balance Cl-

Question 57

Na+

Answer 57

sodium cation
> greatest concentration outside the axon
> diffusion pushes it inward
> electrostatic pressure pushes it inward
> sodium-potassium pump pushes it out of axon

Question 58

diffusion

Answer 58

tendency of molecules to move from a higher concentration are to a lower one until equilibrium is reached

Question 59

osmosis

Answer 59

passive movement of water molecules from one place to another until a uniform concentration is achieved
> occurs when there is a difference in molecular concentration of water on two sides of the membrane
-> membrane allows solvent (water) to move through, but keep out solute (particles dissolved)

Question 60

active transport (membrane potential)

Answer 60

transport of a substance fro lower to higher connotation of that substance, using energy from the cell
> allows cells to obtain nutrients that cannot pass through the membrane by other means
> selective permeability: membrane has some control over what can cross it -> only certain molecules enter or leave the cell
> each ion channel works for one type of ion

Question 61

gated channel

Answer 61

channels in the neurone’s membrane

> can open and close in response to signals like electrical changes

Question 62

repolarisation

Answer 62

K+ move outside the membrane & Na+ stay inside -> repolarising the cell
=> results in polarisation opposite of the initial polarisation

Question 63

spike potential

Answer 63

peak of action potential
causes:
> gated sodium channels to close
> potassium channels to open