1. Nerve cells neural circuitry and behaviour
A.Alipour
Conscioustronics Foundation

2. .1 mm to 2 m!! Length of An axon

3. Neuron has 10 thousand connections
It projects only 1 thousand
Does it mean that the neuron is an integrator?

4. After axon hillock the action potential propagates through the axon without distortion or failure.
1 to 100 m/s
How much time it takes for an A.P to propagate through the skull?

5. First recorded action potential giant axon of squid (1mm diameter)

6. Neuron doctrin
Ramon Cajal
Are Quantum approaches right?

7. We have 3 main rules Neuron doctrine
Principle of dynamic polarization(Unidirectional transmission)
Connectional specificity

8. 3 main type of cells
Unipolar
Bipolar
multipolar

9. unipolar
Unipolar
Mostly in invertebrates and autonomous nervous system

10. bipolar
Bipolars are aboundant in retina and olfactory epithelium of nose

11. Pseudo-unipolar cell
These cell exist in our peripheral sensory system i.e.
The sense of touch, pain pressure sensory system of skin and joint
This cell body forms the ganglion

12. multipolar
Many dendritic branches protruded out of the cell body and just 1 axonal branch projects out of the soma

13. example A spinal Motor neuron
Gets 10 thousand of dendritic input(1000 on its soma)
Purkinje cell in cerebellum gets millions of inputs!

14. Another classification functional
Sensory
Motor
inteneuron

15. afferent V.S. sensory
Every signal or pathway that brings information in whether it will be perceived or not or not (input)
Sensory every afferent signal that will be perceived

16. efferent
Every out put of the system commands of the CNS or spinal cord

17. interneurons We have 2 classes of them
Relay or projection interneurons: They have long projections and connect different areas of the brain
Local interneurons: they make short connections in local circuits

18. Glial cells Derived from the Greek word means “glue”
But they don’t glue!
They support the neurons
We have 2 types of them
Microglia
macroglia

19. microglia
They belong to the Immune system 20% of the glia

20. macroglia They are 3 types : Oligodendrocytes ~40% of all
Astrocytes ~ 40% of all
Schwann cells in periphery

21. Astrocytes and oligodendrocytes
These guys insulate the axon branches
Each of oligodendrocytes covers one to 30 axonal branches depending on their diameter

22. oligodendrocyte

23. Schwann

24. astrocytes Two main types of astrocytes Protoplasmic : in grey matter
Fibrous : in white matter

25. Astrocytes No definite answer but: They take up neurotransmitters
Astrocytes help nourish surrounding neurons by releasing growth factors they feed neurons, also BBB
Astrocytes separate cells
Because astrocytes are highly permeable to K+, they help regulate the K+ concentration in the space between neurons,… why?

26. Each Nerve Cell Is Part of a Circuit That has a specific function
Knee jerk reflex

27. Knee jerk reflex

28. Some simple stuff
each of which makes direct contact with 45 to 50 motor neurons. This pattern of connection, in which one neuron activates many target cells, is called divergence
Conversely, a single motor cell in the knee jerk circuit receives 200 to 450 input contacts from approximately 130 sensory cells. This pattem of connection is called convergence

29. Divergence & convergence

30. Feed-forward inhibition

31. Feedback inhibition

32. 4 components of every neuron
Receptive component
Integrative component
Conductive component
Out put

33. Some electrical stuff!
Resting Membrane potential

34. Some electrical stuff!
Action potential

35. Graded local potentials V.S. active action potential
Receptor potential
Synaptic potential
IPSP and EPSP

36. Axon hillock or trigger zone
It decides about the neuron’s firing
HOW?

37. NEURAL CODE
HOW information is transmitted through neural firing patterns?
ISI? Frequency?

38. Out put component
It releases the neurotransmitter

39. What is a neurotransmitter and how it works?
It is a molecule that is being released from a presynaptic neuron to effect the post synaptic neuron

40. Examples

41. 4 components of every neuron
Receptive component:
dendrites + soma be4 axon hillock, receptor and synaptic potentials
Integrative component: trigger zone
Conductive component axonal branches
Out put neurotransmitter release

42. Nerve cells mostly differ at the molecular level
Different ion channels: different spiking pattern
Different receptors: different inhibitory/ excitatory effects

43. Knee jerk reflex demonstrates what we said up to here

44. Neural nets… One question be4 them
In invertebrate animals, and in some lower-order vertebrates, a single cell (a so-called command cell) can initiate a complex behavioral sequence.
But as far as we know no complex human behavior is initiated by a single neuron. Rather, each behaviour is generated by the actions of many cells.

45. Parallel processing: the paradigm of computation in the brain
The deployment of several neuronal groups or pathways to convey similar information

46. Neural networks…. Help!
elements of the system process information simultaneously using both feed-forward and feedback connections.

47. Neural connectivity
? How is behavior modified if the nervous system is wired so precisely?
Neural connectivity can be altered through experience

48. Plasticity hypothesis
Put forth by Cajal early in 1900
Then advanced by polish psychologist Jerzy Konorski in 1948
These days people have strong believes about it because it has many experimental evidences

49. Some examples of neural plasticity how scientists and engineers used it
Changes in Synaptic effectiveness
Growing new synapses

50. Last point
Do not respect TEXTBOOK THEORIES
Vincent Walsh, BCNC, 2013

51. Time is over? No? Watch the clip!
Sebastian Seung…………. I’m my connectome