1. 2 primary cell types in nervous system
neurons – 10 to 100 billion neurons
Role:
2. glial cells –
provide support, nutrients, myelin, cleanup, etc. for neurons

4. 2 primary cell types in nervous system
neurons – 10 to 100 billion neurons
can vary tremendously in size and shape but all have 3 components
cell body or soma
contains genetic material, provides nutrients,

5. 2 primary cell types in nervous system
1. neurons – 10 to 100 billion neurons
Role:
can vary tremendously in size and shape but all have 3 components
cell body or soma
contains genetic material, provides nutrients,
dendrites
axon

6. How do neurons communicate?
within neurons – electrically
between neurons - chemically

7. Neuron receiving info
Information traveling
down neuron

8. Ramon Y Cajal developed Golgi Stain
first determined space between neurons
“synapse”

9. A brief discussion about communication within a neuron
changes in electrical potential

10. Neurons can exist in one of 3 states
the “resting” state
the “active” state or action potential
neuron is firing
conveying info to other neurons or organs
the recovery or “refractory” state

11. How do we know about what is happening in the neuron?
giant squid axon
why was work done with the giant squid axon?

14. At rest:
inside of the axon has a slightly negative charge relative to outside the axon
called the membrane or resting potential
(~ -60 mV)
why?

15. Neuron stimulated
see depolarization (change from negative inside neuron to more positive)
“threshold” – if a great enough depolarization occurs, an action potential will occur
action potential – very quick - milliseconds

16. When the action potential occurs…..
see depolarization (change from negative (~ -60mV) inside neuron to more positive (~ +30 mV))

17. threshold
resting potential

18. hyperpolarization
after action potential – return to negative (actually a more negative state than to begin with)

19. What causes these changes in electrical potential?
All axons and cells have a membrane
thin bilayer that surrounds cell allowing some chemicals and ions in but keeping others out
axons also have a large number of protein channels that when open allow ions (charged molecules) to flow in or out

21. What causes these changes in electrical potential?
Ions flowing across the membrane causes the changes in the potential
Ions are molecules that contain a positive or negative charge
anion – negative charge
cation – positive charge

22. Some important ions for neuronal communication
Na+ sodium
HIGHER CONCENTRATION OUTSIDE THE AXON
Cl- chloride
HIGHER CONCENTRATION OUTSIDE AXON
K+ potassium
higher concentration inside the axon
A- anions -large (-) molecules with a negative charge (stuck inside the axon)

23. Neuron at Rest Na+ and Cl- are in higher concentration
OUTSIDE AXON (EXTRACELLULAR
FLUID)
INSIDE AXON
(intracellular)
Na+
Cl-
Na+ A-
Cl-
Cl- A-
Cl-
Cl-
Na+
Na+
Cl-
Cl- A-
Na+
Na+ A-
Na+
Na+
Cl- A-
Na+
Na+
Cl-
Na+
Cl-
Cl-
Na+ A-
Na+
Cl-
Cl-
Cl-
Cl-
Na+ and Cl- are in higher concentration
in the extracellular fluid
Neuron at Rest

24. Neuron at Rest K+ and negative anions are in higher concentration
INSIDE AXON
OUTSIDE AXON (EXTRACELLULAR FLUID)
Cl- K+ K+ K+
Cl- A-
Na+
Cl- A-
Na+ K+
Na+ A-
Cl-
Na+ K+ A-
Na+
Cl-
Na+ K+ K+
K+ and negative anions are in higher concentration
in the intracellular or inside the axon
Neuron at Rest

25. Some forces that play a role in maintaining membrane potential
concentration gradient –
ions diffuse from higher concentration to lower concentration

26. What would each ion do if the ion channel opened based on the concentration gradient?
Na+ K+
Cl-

27. Some forces that play a role in maintaining membrane potential
concentration gradient –
ions diffuse from higher concentration to lower concentration
electrical gradient -
opposite charges attract so ions are attracted to an environment that has a charge that is opposite of the charge they carry!

28. example of electrostatic forces

29. What would each ion do if the ion channel opened based on electrostatic forces ?
Na+ K+
Cl-

30. What drives the action potential?
opening of Na+ channels and influx of Na+ ions

32. What happens if sodium channels are blocked?
lidocaine, novocaine, cocaine
TTX – tetrototoxin
Sagitoxin-
red tides

35. What about communication between neurons?

37. Communication between neurons
most psychoactive drugs work via this mechanism
chemical transmission via the synapse
neurotransmitters

38. label some things
presynaptic ending – axon – releases chemical if the neuron generated an action potential

39. presynaptic ending
(axon)

40. label some things
presynaptic ending – axon – releases chemical if the neuron generated an acton potential
postsynaptic ending – can be dendrite, cell body, or axon
receives chemical signal from neuron –
synapse – tiny gap between neurons

41. Other things to notice in presynaptic ending
Ca+ channels -
synaptic vesicles
contain neurotransmitter

43. What happens at level of synapse when an action potential occurs?
Ca+2 enters presynaptic ending via Ca+ channels
synaptic vesicles bind to presynaptic ending and release their neurotransmitter
Neurotransmitter crosses synapse and binds to receptor on postsynaptic side

45. postsynaptic receptors
protein embedded in membrane
mechanism for neurotransmitter to influence postsynaptic activity by binding to receptor

46. What happens when neurotransmitter binds to the postsynaptic receptor?
can cause the opening of localized ion channels in the postsynaptic ending
Na+ or
K+ or
Cl-

47. What happens when neurotransmitter binds to the postsynaptic receptor?
can cause the opening of localized ion channels in the postsynaptic ending
IF:
Na+ channels open - Na+ enters
local excitation (or depolarization)
K+ or
Cl-

48. What happens when neurotransmitter binds to the postsynaptic receptor?
can cause the opening of localized ion channels in the postsynaptic ending
IF:
Na+
K+ channels open – K+ leaves the cell
causes local inhibition or hyperpolarization
Cl-

49. What happens when neurotransmitter binds to the postsynaptic receptor?
can cause the opening of localized ion channels in the postsynaptic ending
IF:
Na+
K+ or
Cl- channels open – influx of Cl-
causes local inhibition or hyperpolarization

50. Graded Potentials-
these local changes in ion flow are called graded potentials
has impact in limited region
increases or decreases the likelihood of the neuron receiving info to generate an action potential.

51. How do graded potentials contribute to the likelihood of an action potential?
graded potentials are summed at axon hillock – if great enough depolarization to reach “threshold” – axon generates an action potential

52. What happens when neurotransmitter binds to the postsynaptic receptor?
if Na+ channels open - increases likelihood of generating an action potential
if K+ channels open - - decreases the likelihood of an action potential
if Cl- channels open - decreases the likelihood of an action potential

55. Ways that graded potentials differ from action potentials
action potentials are “all or none” while graded potentials decrease over space and time
localized – has impact in limited region
action potentials always excitatory while graded potentials can be excitatory or inhibitory

56. Two types of graded potentials
excitatory -
EPSPs – excitatory postsynaptic potentials
Na+ ion channels
IPSPs inhibitory postsynaptic potentials
K+ or Cl- ion channels

58. 2 ways that neurotransmitter exert these effects
ionotrophic - directly opening the ion channel
occurs and terminates very quickly

60. 2 ways that neurotransmitter exert these effects
ionotrophic - directly opening the ion channel
occurs and terminates very quickly
metabotropic - more indirect
ultimately opens ion channel via stimulating a chemical reaction through a "second messenger system"
takes longer but lasts longer

62. How do we get rid of the transmitter from the synapse?
2 main ways
1. reuptake - most common
transporter on presynaptic ending
a means of recycling
a common way for drugs to alter normal communication

63. transporter

64. enzyme degradation enzyme - speeds up a reaction
ex. acetylcholine (ACh) is broken down by acetylcholinesterase (AChE)

66. NT binding to postsynaptic receptor
“lock and key analogy”

67. Neurotransmitter represents a key
Receptor represents the lock
Other keys can represent drugs

68. What are possibilities?
agonist – mimics the neurotransmitter
antagonist – blocks the neurotransmitter
partial agonists/ partial antagonists –