1. CBNS 106 Review
Lecture 2

2. Brain Cells Neurons (100 billion) Glia (10 times more)
Process information
Sense environmental changes
Communicate changes to other neurons
Command body response
Glia (10 times more)
Insulate, support and nourish neurons

3. Staining Nissl Stain Golgi Stain Facilitates study of cytoarchitecture
Shows soma and neurites (dendrites and axon)

9. Different classes of neurons

10. Afferent – INFO  CNS

12. ASTROCYTES!!!

13. CBNS 106
Lecture 3

16. - Astrocytes buffer excess potassium, cycle it from ecs to bbb

17. CBNS 106 Review
Lecture 4 and 5

18. Action Potential
Ideal
Actual

21. “Resting” Cell
During AP

23. Action Potential Conduction
The entry of positive charge during the action potential causes the membrane just ahead to depolarize to threshold
Orthodromic conduction – action potentials conduct only in one direction
Antidromic conduction – backward propagation
Typical conduction velocity ~ 10 m/sec
Action potentials last ~ 2 msec

24. Factors Influencing Conduction Velocity
Spread of action potential along membrane • Dependent upon axon structure Path of the positive charge • Inside of the axon (faster) • Across the axonal membrane (slower) * If the axon is narrow and there are many open membrane pores then most of the current will flow out across the membrane. * If the axon is wide and there are few open membrane pores, then most of the current will flow down inside the axon * The farther the current goes down the axon, the farther ahead the action potential will depolarize the membrane and thus the faster the action potential.

25. Factors Influencing Conduction Velocity
Axonal excitability
• Axonal diameter (bigger = faster)
• Number of voltage-gated channels
Myelin: Facilitates current flow
• Myelinating cells
– Schwann cells in the PNS
– Oligodendroglia in CNS
Saltatory Conduction – The propagation of an action potential down a myelinated axon

26. CBNS 106 Review
Lecture 6

27. Synaptic Transmission
The process of information transfer at a synapse
Direction of Flow
One direction, Neuron-to-Target Cell
1st Neuron called Presynaptic Neuron
Target Cell called Postsynaptic Neuron
Two Types of synapses
Chemical
Electrical

28. Synaptic Transmission
• Electrical Synapses: - They allow the direct transfer of ionic current from one cell to another - Gap junction - Cells are said to be “electrically coupled” • Flow of ions from cytoplasm to cytoplasm
- Very fast transmission
• Postsynaptic potentials (PSPs)
- Synaptic integration: Several PSPs occurring simultaneously to excite a neuron (i.e.causes AP)

29. Synaptic Transmission
Types of Synapses
- Axodendritic (a)
- Axosomatic (b)
- Axoaxonic (c)
- Asymmetrical membrane differentiations (a)
- Symmetrical membrane differentiations (b)

30. Synaptic Transmission
• Chemical Synapses:
– Neurotransmitter, the chemical is used to transfer information from one cell to another
- Most synaptic transmission in the mature human nervous system is chemical.

31. Synaptic Transmission
Principles of Chemical Synaptic Transmission
• Basic Steps
– Neurotransmitter synthesis
– Load neurotransmitter into synaptic vesicles
– Neurotransmitter Release
• Vesicles fuse to presynaptic terminal
• Neurotransmitter spills into synaptic cleft
– Binds to postsynaptic receptors
– Biochemical/Electrical response elicited in postsynaptic cell
– Removal of neurotransmitter from synaptic cleft

32. Synaptic Transmission
Neurotransmitter Release
– Exocytosis: Process by which vesicles release their contents; 60 microsec
Mechanisms
• Process of exocytosis stimulated by release of intracellular calcium, [Ca2+]i
• Proteins alter conformation - activated
• Vesicle membrane incorporated into presynaptic membrane
• Neurotransmitter released
• Vesicle membrane recovered by endocytosis

33. Neurotransmitter Recovery and Degradation
– Diffusion: Away from the synapse – Reuptake: Neurotransmitter re-enters presynaptic axon terminal – Enzymatic destruction inside terminal cytosol or synaptic cleft – Desensitization: e.g., AChE cleaves Ach to inactive state

34. Neurotransmitters Amino acids: Small organic molecules
• e.g., Glutamate (Glu), Glycine (Gly), gammaaminobutyric acid (GABA)
Amines: Small organic molecules
• e.g., Dopamine (DA), Acetylcholine (Ach), Norepinephrine (NE), Serotonin (5-HT)
Peptides: Short amino acid chains (i.e. proteins) stored in and released from secretory granules
• e.g., Dynorphin, Enkephalins

35. PSP Generation
• EPSP = excitatory postsynaptic potential – Transient postsynaptic membrane depolarization by presynaptic release of neurotransmitter • IPSP = inhibitory postsynaptic potential – Transient hyperpolarization of postsynaptic membrane potential caused by presynaptic release of neurotransmitter

36. Synaptic Integration
Process by which multiple synaptic potentials combine within one postsynaptic neuron
Allows for neurons to perform sophisticated computations
Integration: PSPs added together
Spatial: PSPs generated simultaneously in different spaces
Temporal: PSPs generated at same synapse in rapid succession

37. Synaptic Integration
Synaptic vesicles: Elementary units of synaptic transmission
Quantum: An indivisible unit
Miniature postsynaptic potential (“mini”)
Quantal analysis: Used to determine number of vesicles that release during neurotransmission
Neuromuscular junction: About 200 synaptic vesicles, EPSP of 40mV or more
- CNS synapse: Single vesicle, EPSP of few tenths of a millivolt

38. Synaptic Integration • IPSPs and Shunting Inhibition
– Excitatory vs. inhibitory synapses: Bind different neurotransmitters, allow different ions to pass through channels
– Membrane potential less negative than -65mV = hyperpolarizing IPSP
• Shunting Inhibition: Inhibiting current flow from soma to axon hillock
(a) Stimulation of the excitatory input causes inward postsynaptic
current that spreads to the soma, where it can be recorded as an EPSP.
(b) When the inhibitory and excitatory inputs are stimulated together, the depolarizing current
leaks out before it reaches the soma.

39. Chemical Synaptic Transmission Principles
Autoreceptors – Presynaptic receptors sensitive to neurotransmitter released by presynaptic terminal – Act as safety valve to reduce release when levels are high in synaptic cleft (autoregulation)