Neurophysiology

1. Neurophysiology Electrical Activity in the Body

4. Review of basic principles of electricity • Two types of electrical charges? • Like charges_________ • Opposite charges________ • The difference in electrical charged areas is called____________ __________. • Electricity is measure in _______. • In your body measurements are _________.

5. Apparatus to administer thermal stimuli and record nerve impulses.

6. Distribution of charges in the Nerve Cell • Outside the cell • Na+ (150mM), K+ (15mM) and Cl- (120mM) • Inside the cell • Na+ (15mM), K+ (150mM) and Cl- (10mM), A- (100mM) Recall the Cell Membrane and membrane transport… What molecules will diffuse based on diffusion properties?

9. Na+/K+ Pump • http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

10. Membrane Potential • Nerve cells have differences in the concentration of ions • The membrane is electrically Polarized (more – charges on inside than the other) • Anions are more concentrated inside a cell • Cations are more concentrated outside the cell Recall a molecule that is polar…?

11. Extracellular fluid Intracellular fluid

12. Review 10-16-14 • What are the three types of neurons? • Which neuron transmits impulses from sensory receptors to the brain or spinal cord? • Which neuron transmits impulses from the CNS to effectors? • Discuss the function of myelination? Which type of neurons are myelined? Why? • In order to maintain membrane potential, the cell membrane of neurons are composed of __? • The electrical charge of a neuron is __?

13. Membrane Potential • How do we measure potential? • Milivolts • Resting state: when a nerve is inactive (not transmitting a signal) the value is –70 mV

14. Changes in the Membrane Potential of a neuron give rise to nerve impulses • How are the membrane potentials changed? • Response to stimuli (ion concentrations) Ex: temperature, light, or pressure • Chemical stimuli (neurotransmitters) Ex: dopamine, serotonin, amino acids

15. http://www.biology4all.com/resources_library/source/63.swf

17. Phases of an action potential • Resting State: Neither channel is open • Depolarization: Na+ channels open, K+ remain closed • Repolarization: Na+ channels close, K+ channels open • Undershoot: K+ channels remain open (slow to close)

19. http://highered.mheducation.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.htmlhttp://highered.mheducation.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

20. Nerve Impulse Conduction • The resulting action potential causes an electric current that stimulates adjacent portions of the membrane • Series of action potentials occurs sequentially along the length of axon as a nerve impulse

21. Factors that determine speed of Nerve Impulses • Temperature: The higher the temperature, the faster the speed. • Axon diameter - The larger the diameter, the faster the speed • Myelin sheath – • Only vertebrates have a myelin sheath surrounding their neurons. • The voltage-gated ion channels are found only at the nodes of Ranvier, and between the nodes the myelin sheath acts as a good electrical insulator. • The action potential can therefore jump large distances from node to node (1mm), a process that is called saltatory propagation. • This increases the speed of propagation dramatically, so while nerve impulses in unmyelinated neurones have a maximum speed of around 1 m/s, in myelinated neurones they travel at 100 m/s.

22. Review of Action Potentials • How are the membrane potentials changed? • What factors may affect the speed/rate of a nerve impulse? • The potential difference between cell membrane is called ______ ________. • Describe the conditions of a neuron that is at rest. • What occurs during Depolarization? • Suggest Why a refractory period is necessary after action potential has been reached?

24. Characteristics of Nerve Impulses • Refractory period • All or none response • Impulse conduction

25. Refractory Periodaka: Rest Time • For an action potential to begin, then the depolarization of the neuron must reach the threshold value, i.e. the all or nothing law. • refractory period, • After an ion channel has opened, it needs a “rest period” before it can open again/ lasts about 2 ms. • One Way Street: although the action potential affects all other ion channels nearby, the upstream ion channels cannot open again since they are in their refractory period • only the downstream channels open, causing the action potential to move one-way along the axon.

26. Refractory Period • The refractory period is necessary as it allows the proteins of voltage sensitive ion channels to restore to their original polarity. • 2 periods of refractory period • absolute refractory period  = during the action potential, a second stimulus will not cause a new action potential. 2. Exception:  There is an interval in which a second action potential can be produced but only if the stimulus is considerably greater than the threshold = relative refractory

27. Refractory…Why? • Limits how many action potentials may be generated

28. Chemicals released from pre-synaptic neuron Act to assist, stimulate or inhibit postsynaptic neurons Where do they come from? Synthesized in cytoplasm of synaptic knobs Or stored in vesicles Neurotransmitters • http://intro.bio.umb.edu/111-112/112s99Lect/neuro_anims/s_t_anim/WW36.htm

29. How NTs are released • http://highered.mheducation.com/sites/9834092339/student_view0/chapter44/chemical_synapse.html • https://www.youtube.com/watch?v=p5zFgT4aofA

30. Acetylcholine

32. Categories of NT • Monoamines • Epinephrin, dopomine, and serotonin • Amino acids • Glycine, glutamic acid and gamma aminobutyric acid: GABA • Peptides • Made in RER • Neuropeptide • Alter response to a NT or block release of NT • Act as NTs • Released during stress • Ex: beta endorphin: pain reliever…similar to morphine

33. Norepinephrineaka: adrenalin • Released from brain and ANS • Adrenal gland • Excitatory • Sense of feeling good, alertness • Increases heart rate and Bld pressure • Monoamine • Can be used to manage hypertension

34. Glutamate • Found in CNS and concentrated in brain • Excitatory

35. Dopamine • Released from brain (CNS) • hypothalamus • Receptors: heart, kidneys, bld vessels • Inhibitory (can be excitatory) • sense of feeling good, reward pathway • Parkinson’s Disease • amine

36. Serotonin • Brain (CNS) • Regulates endocrine activity (hormonal controls) • Leads to sleepiness • Involved with mood and perception • Controls sleep/wake cycles • amine • Inadequate amounts: • Severe depression and obsessive/compulsive disorders, anger issues, and eating disorders

37. Endorphins • Neuropeptide • Produced in brain (CNS) • Pain relief and pleasure • Released in times of pain or stress • Elevated levels cause disease known as Addison’s disease • Structure is similar to??? • morphine

38. GABAgamma amino butyric acid • Inhibitory • Prevents NT that can cause sensitivity/anxiety

39. Review of NTs ___1. dopaminea. excitatory; involved in control of skeletal muscles ___ 2. norepinephrine b. associated with reward mechanisms ___ 3. serotoninc. chemical structure related to morphine ___ 4. acetylcholine d. inadequate amounts may lead to depression ___ 5. endorphins e. excitatory; vasoconstrictor 6. Define a synapse. 7. Predict What would happen if Ca+ ions were not stimulated by a nerve impulse at a chemical synapse? • What causes a person to become dependent on drugs? • What might occur if a NT remains in the synapse after communicating with a post-synaptic neuron? • Draw and label a chemical synapse.

40. Disorders Associated with NT imbalances

41. SIDS • NT: excess dopamine • Symptoms: baby stops breathing • Leading cause of death of infants 0-1yr • Factors: smoking, sleeping on belly

42. NT: deficient serotonin Symtoms: no sleep! Insomnia

43. NT: not enough AcH Symptoms: memory loss, depression, disorientation Alzheimer's

44. Parkinson’s • NT: not enough dopamine • Symptoms: tremors, muscle rigidy • Inhibitory? Excitatory? • Over stimulation of neurons controlling muscle tone

45. Huntington’s • NT: deficient GABA • Symptoms: personality changes, loss of coordination, muscle control, death

46. Depression • NT: serotonin • Anger, sadness, excess sleep, social isolation, short tempered….over long period of time

47. http://www.williams.edu/imput/introduction_main.html