BIOL 273 Exam

1. BIOL 273 Exam

2. Introduction • James England • 4th Year Biochemistry Student • Research focus on the molecular causes of aging in yeast

3. 2010 Outreach Trip Summary Date Aug 20 – Sept 4 Location Cusco, Peru # Students 22 Project Cost $16,000 Building Projects Kindergarten Classroom provides free education Sewing Workshop enables better job prospects ELT Classroom enables better job prospects More info @ studentsofferingsupport.ca/blog

4. Cell to Cell Communication Add Red Dye to left cell Connexon

5. Cell to Cell Communication

6. Cell to Cell Communication Paracrine Target Cell Cell Autocrine Endocrine Blood

7. Receptors • Signalling specificity depends on Receptor Proteins • Signalling molecule binds onto a specific receptor found only on target cells transmembrane, cytosolic, or nuclear location • Receptor protein is what brings about the response to signal • Agonists Binds receptor and activates response • Antagonists  Binds receptor and produces no response (inhibitory activity)

8. Receptors Biological Signalling Molecule Foreign “drug” molecule Foreign “drug” molecule Antagonist Pathway Without Response Normal Signal Pathway With Response Agonist Pathway With Response

9. Nervous System • 1) Receives information  Sensory neurons from external environment (light, sound, pressure etc) • 2)Integrates Information  Organizes new information, combines with stored information • 3) Transmits Information Sends signals to muscles/glands to carry out action

10. Neurons Dendrites Axon Terminal Node of Ranvier Soma Myelin Sheath/ Schwann Cell Axon Nucleus Ref: Wikipedia http://en.wikipedia.org/wiki/File:Neuron_Hand-tuned.svg

11. Neurons

12. Nervous System

13. Glial Cells Neurons Neurons are the VIP’s of the nervous systems! They need other people to help do their laundry, cook food, act as bodyguards, etc etc so they can focus on their jobs

14. Neurons Dendrites Axon Terminal Node of Ranvier Soma Myelin Sheath/ Schwann Cell Axon Nucleus Ref: Wikipedia http://en.wikipedia.org/wiki/File:Neuron_Hand-tuned.svg

15. PNS Glial Cells Schwann Cells  form myelin sheath which acts as electrical insulator. Only wrap around 1 cell • Structure has many layers of cell membrane with gap junctions connecting layers -Gap Junctions Neuron

16. PNS Glial Cells • Satellite Cells  non-myelinating, support nerve cells

17. CNS Glial Cells-4 Types • 1) Oligodendrite Myelinating Cell (like Schwaan) but can wrap around more than one neuron • 2) Astroglia  Make contact with blood vessels and neurons; transfer nutrients, maintain microenvironment; Star Shaped.

18. CNS Glial Cells • 3) Microglia Small, specialized immune cells -maintain microenvironment like astroglia -remove dead cells & foreign invaders, protect neurons • 4) Ependymal Cells  Epithelial cells, create semi-permeable barriers between brain compartments -produce cerebrospinal fluid

19. Electrical Properties of Neurons • Difference between electrical charge on the inside of the cell and the outside environment creates an electrical gradient across the membrane • There is also an osmotic gradient due to the differences in concentrations of solutes between the inside & outside of cell

20. Electrical Properties of Neurons • Cell membranes are semi-permeable • Allow free diffusion of small, hydrophobic (non-polar) molecules • Membranes are impermeable to most molecules, Especially charged ions. • Specific protein transporters move these molecules across the membrane

21. Resting Membrane Potential • Resting Membrane Potential for a neuron is around -70 mV to -90 mV  Negative charge compared to environment; mostly due to phosphate (HPO42- ,H2PO4-), and negatively charged proteins & DNA + + + - + - - - + + - - -70 mV - + + + - - + -

22. Resting Membrane Potential • Know the relative ion concentrations for the neuron at rest: • Na+, Cl-, and Ca2+ have concentrations higher in the extracellular fluid (outside cell) • K+ has a higher concentration inside the cell Na+ Cl- -70 mV Ca2+ K+

23. Na+/K+ ATPase • Active transport of 3 Na+ out of the cell and 2 K+ into the cell powered by ATP • Pumps ions against gradient (by consuming energy) to maintain cellular concentrations of K+ and Na+ • Compensates for ions leaking into/out of cell along their concentration gradient

24. Nernst Equation • Equilibrium Potential (Eion) is the electrical potential of the Cell needed to generate an equilibrium state for a KNOWN concentration gradient  The electrical gradient needed to balance the concentration gradient • Compare this to known cell potential to predict where ions are likely to flow

25. Nernst Equation • Know that K+ is found at higher concentrations inside of the cell  Concentration gradient dictates K+ would flow out of the cell • Calculated Equilibrium Potential for Potassium is -90 mV. Neuron with membrane potential of -70 mV Neuron with membrane potential of -90 mV - - - - - -70 mV -90 mV - K+ K+ K+ will flow (leak) out of cell Negative charges not enough to attract PositiveK+to remain in the cell No NET K+ movement Negative charges attract PositiveK+ to balance concentration gradient

26. Nernst Equation • Know that Na+ is found at higher concentrations outside of the cell  Concentration gradient dictates Na+ would flow into the cell • Calculated Equilibrium Potential for Na+ is +60 mV. Neuron with membrane potential of -70 mV Neuron with membrane potential of +60 mV - + + - Na+ Na+ + -70 mV +60 mV + + Na+ will leak into the cell Negativecharges not enough to repel PositiveNa+to prevent movement into cell No NET Na+ movement Positive charges repel PositiveNa+ to balance concentration gradient

27. Resting Membrane Potential & Ion Permeability • The relative permeability of these ions dictate how important their contribution is to the resting membrane potential (RMP) • Ions that can move more easily through the membrane contribute greater to the RMP • RMP can be calculated using the Goldman Equation which takes into account the relative permeability of ions • Permeability can be increased by: 1)opening gated protein channels for transport 2) increasing the # of transport proteins

28. Gated Channels Stretch + + + + Channel Closed Channel Open Channel Closed Channel Open Channel Closed Channel Open Voltage Gated - Respond to membrane potential changes - Involved in initiation and conduction of electrical signals Chemically Gated - Respond to ligand binding (neurotransmitters, neuromodulators) - “most important” for neurons (located in synapses) Mechanically Gated - Respond to physical forces - Found in Sensory neurons

29. Changes in Membrane Potential Repolarizationis any change in membrane potential which returns it to the Resting Membrane Potential

30. Graded & Action Potentials

31. Neurons Dendrites Axon Terminal Node of Ranvier Soma Myelin Sheath/ Schwann Cell Axon Nucleus Ref: Wikipedia http://en.wikipedia.org/wiki/File:Neuron_Hand-tuned.svg

32. Graded Potentials Activate Action Potentials Depolarizing Graded Potential Net Graded potential -55 mV -70 mV Hyperpolarizing Graded Potential

33. Action Potential 3 +30 mV 4 2 0 -55 mV 1 6 -70 mV 5

34. Action Potential-Voltage Gates Na+ + + + Activation Gate Inactivation Gate Sodium (Na+) Channel with Activation Gate (opens at -55 mV), and Inactivation Gate (voltage activated but time delayed)

35. Action Potential-Voltage Gates + + K+ Potassium (K+) Channel with Voltage Gate which opens later than Na+ channels (fully open at +30 mV)

36. Action Potential 3 +30 mV 4 2 0 -55 mV 1 6 -70 mV 5

37. Action Potential 0 MP = Less than -55 mV + + 1 MP = -55 mV + +

38. Action Potential Na+ 2 + MP = Between -55 mV and +30 mV + 3 &4 + + MP = +30 mV to -70 mV K+

39. Action Potential 3 +30 mV 4 2 0 -55 mV 1 6 -70 mV 5

40. Action Potential ABSOLUTE REFRACTORY 5 + MP = Less than -70 mV + K+ 5.5 RELATIVE REFRACTORY + MP = Less than -70 mV + K+

41. Neurons Dendrites Axon Terminal Node of Ranvier Soma Myelin Sheath/ Schwann Cell Axon Nucleus Ref: Wikipedia http://en.wikipedia.org/wiki/File:Neuron_Hand-tuned.svg

42. Refractory Periods • Set directionality of Signal  cannot activate membrane regions which have recently fired Na+ + + + Na+ Na+ Na+

43. Synapses • Electrical Synapses Gap junctions connect 2 cells allowing direct electrical signalling - CNS; between 2 neurons, or neuron and glial cell - Nervous system development and transmission in adult brain Action Potential Depolarization wave Action Potential Depolarization wave

44. Chemical Synapse Synaptic Cleft Presynaptic cell Postsynaptic cell Action Potential Depolarization wave Ions Neurotransmitter Receptors can either open ion channel directly, or cause another (long lasting) signal cascade  coupled to G proteins etc AP causes Ca+2 entry  vesicles release neurotransmitter Ca2+

45. Types of Neurotransmitters

46. Types of Neurotransmitters

47. Peripheral Nervous System

48. CNS Somatic neuron Always excitatory ACh Nicotinic ACh receptors Muscle Cell

49. CNS Parasympathetic 2 Neuron chain Sympathetic 2 Neuron Chain Swollen Terminals Varicosity; stores a lot of neurotransmitter Ganglion Target Cell Target Cell

50. G Proteins & Ion Channels IONS e.g. Nicotinic cholinergic receptors 1 molecule of neurotransmitter opens 1 ion channel