transmission within neurons

Question 1

what is the CNS?

Answer 1

brain

spinal cord

Question 2

what is the PNS?

Answer 2

all other nerves that connect body to CNS

Question 3

what are sensory neurons?

Answer 3

carry information from the body

light, sound, pressure, odour information

Question 4

what are interneurons?

Answer 4

link sensory and motor neurons

Question 5

what are motor neurons?

Answer 5

control muscle contraction - movement

carry information from CNS to body

Question 6

what are neurons?

Answer 6

do all information processing and information transmitting

many different types of neurons

86 billion neurons

receives information usually on its dendrites from another neuron’s terminal buttons

Question 7

what is the structure of neurons?

Answer 7

soma

dendrites

axon

myelin sheath

terminal button

Question 8

what is the soma?

Answer 8

cell body

contains nucleus

Question 9

what are dendrites?

Answer 9

branch-like structures

receives messages

Question 10

what is an axon?

Answer 10

carries information (action potential) from soma to terminal buttons

Question 11

what is the myelin sheath?

Answer 11

wraps around axon

Question 12

what are terminal buttons?

Answer 12

at the end of the axon branches

Question 13

how many glia are there?

Answer 13

number of glia about equivalent to number of neurons

Question 14

what are glia?

Answer 14

cells provide support, waste services, supply of nutrients and chemicals

Question 15

what are the different types of glia?

Answer 15

astrocytes

oligodendrocytes

microglia

Question 16

what are astrocytes?

Answer 16

star-shaped cells

provide structural support to neurons

help provides nutrients to neurons

surround synapse - help limit dispersion of neurons

Question 17

how to astrocytes help provide nutrients to neurons?

Answer 17

receive glucose from capillaries and break it down into lactate

released into extracellular fluid and taken up by neurons

Question 18

what are oligodendrocytes?

Answer 18

produce myelin sheath that insulates axons

one cell = 50 segments of myelin sheath

Schwann cells provide similar function in PNS

Question 19

what are microglia?

Answer 19

smallest of supporting cells
clear away dead and dying neurons

act like brain’s immune system

Question 20

how do the microglia act like the brain’s immune system?

Answer 20

attack foreign tissue

aid repair to damaged cells

Question 21

what is the Node of Ranvier?

Answer 21

naked axon

Question 22

what kind of process is transmission within a neuron?

Answer 22

electrical

results from movement of ions across a membrane

Question 23

how do cells have an electrical charge?

Answer 23

more negative on inside than outside

results in resulting potential (store of energy)

neurons can reverse their electrical charge

Question 24

what is the membrane?

Answer 24

all cells covered in membrane

made up of two layers of phospholipid molecules

Question 25

what are the heads of phospholipid molecules?

Answer 25

hydrophilic attracted to each other and water

Question 26

what are the tails of phospholipid molecules?

Answer 26

hydrophobic attracted away from water and point inwards towards each other

Question 27

what is the ion channel?

Answer 27

spans the membrane

Question 28

what are ions?

Answer 28

charged molecules

Question 29

what are cations?

Answer 29

positively charged

Question 30

what are anions?

Answer 30

negatively charged

Question 31

what does intracellular fluid contain?

Answer 31

potassium ions (K+) anions (A-)

Question 32

what does extracellular fluid contain?

Answer 32

sodium (Na+) chloride (Cl-) ions

Question 33

what is membrane potential?

Answer 33

difference in electrical potential inside and outside the cell

Question 34

what is membrane potential balanced by?

Answer 34

diffusion - movement of molecules from regions of high concentration to regions of low concentration electrostatic pressure - attraction or repulsion of particles depending on what charge they are

Question 35

what do organic anions (A-) do?

Answer 35

concentrated inside the cell cannot cross the membrane

Question 36

what do potassium cells (K+) do?

Answer 36

more concentrated inside the cell diffusion = wants to move out electrostatic = attracted to inside (-ve) overall = forces balanced so K+ doesn't want to move

Question 37

what do chloride ions (Cl-) do?

Answer 37

more concentrated outside the cell diffusion = wants to move in electrostatic = repelled from inside (-ve) overall = forces balance so Cl- doesn't move

Question 38

what do sodium ions (Na+) do?

Answer 38

more concentrated outside the cell diffusion = wants to move in electrostatic = attracted to inside (-ve)

Question 39

how is Na+ kept under control?

Answer 39

by sodium-potassium pumps 2x Na+ pumped out, 2x K+ pumped in

Question 40

what is the resting potential of the inside of the neuron?

Answer 40

negative

Question 41

what is the resting potential of the outside of the neuron?

Answer 41

positive

Question 42

what is the overall resting potential of a neuron?

Answer 42

-70 mV inside of the cell more negative than outside

Question 43

why is maintaining resting potential important?

Answer 43

so neuron can respond rapidly to a stimulus

Question 44

what is action potential?

Answer 44

reversal in the potential rapid change in membrane potential how information sent through an axon "all or none" process (fires or doesn't) stays same size throughout transmission

Question 45

what is an electrical impulse?

Answer 45

rapid change in the potential

Question 46

what is depolarisation?

Answer 46

decrease from normal resting potential brings membrane closer to 0

Question 47

what is hyperpolarisation?

Answer 47

increase relative to resting potential more negative

Question 48

what does voltage dependent channels mean?

Answer 48

only open at certain point of membrane potential

Question 49

what does refractory mean?

Answer 49

can't open again

Question 50

what is the process of membrane potential?

Answer 50

at rest neuron is -70mV threshold of excitation reached (about -50 mV) Na+ channels open (voltage dependent) Na+ enters the cell (diffusion and electrostatic, cell begins to depolarise till about +40) Na+ channels close (peak of action potential reached) then reverses - repolarisation K+ leaves cell through K+ channels (diffusion and electrostatic) K+ channels close membrane is hyperpolarised (due to K+ outside membrane) these diffuse away and Na+K+ pump moves Na+ outside of cell and K+ into cell changes due to movement of ions

Question 51

what is propagation?

Answer 51

action potential is transmitted down an axon via propagation action potential is regenerated at points along the axon due to entry of sodium ions at neighbouring point only one way down axon size of action potential doesn't change but frequency might

Question 52

what is saltatory conduction?

Answer 52

action potential regenerated along the axon at Nodes of Ranvier

Question 53

what are the benefits of saltatory conduction?

Answer 53

fast conduction more energy efficient because sodium-potassium pumps only needed to nodes of Ranvier