Understanding Parkinson's and Alzheimer's Diseases

1. Parkinson’s and Alzheimer’s disease both affect the nervous system.

2. The Nervous System “Cells of the Nervous System”

3. Organization of Nervous System Can be divided three ways • Structurally • Direction of information flow • Effector control (job it does)

4. Organization of the Nervous System STRUCTURAL • Central Nervous System (CNS) • Brain and spinal cord • Peripheral Nervous System (PNS) • Cranial and spinal nerves

5. Organization of the Nervous System DIRECTION OF INFORMATION • Afferent Divisions (carry towards brain) • All incoming sensory or afferent pathways • Efferent Divisions (carry away from brain) • All outgoing motor or efferent pathways

6. Organization of the Nervous System EFFECTOR CONTROL • Somatic Nervous System (SNS) • Somatic effectors are skeletal muscles • Somatic sensory division provide feedback from affectors. • Autonomic Nervous System (ANS) • Carries information to the autonomic or visceral effectors. • Smooth and cardiac muscles, glands • Visceral sensory division provides feedback from affectors.

7. Divisions of Autonomic Nervous System • Sympathetic Division • “fight or flight” response • takes over to deal with immediate threats • Parasympathetic Division • “rest and repair” division • Coordinates normal resting activities

9. Cells of the Nervous System • Neurons • Excitable cells that transmit signals • Glia (glial cells) • Are support cells for the neurons

10. Glia Cells • Glia means glue • Estimated to be about 900 billion • Divide through adulthood • Susceptible to cancer and tumors This MRI scan, taken in the sagittal plane, shows a tumor of approximately 3cm diameter (white circular area) in Wernicke's area of the left hemisphere.

11. Astrocytes • Microglia • Ependymal cells • Oligodendrocytes • Schwann cells • Satellite cells

12. Astrocytes • Found only in the CNS • Largest and most numerous type of glia • Attach to capillaries and neurons • Get nutrients to neurons • They form the blood-brain barrier (BBB)

13. Microglia • Small and stationary • Found in CNS • In inflamed brain tissue they carry phagocytosis

14. Ependymal cells • Resemble epithelial cells • Line fluid filled cavities in the brain and spinal cord • Cilia helps keep fluid circulating

15. Oligodendrocytes • “cell with few branches” • Hold nerve fibers together • Produce the fatty myelin sheath around the nerve fibers of CNS

16. Schwann Cells • Found only in PNS • Support nerve fibers sometimes forming myelin sheath around them • Gaps between schwann cells are called nodes of Ranvier • Myelinated fibers are called white fibers • Un-myelinated fibers are called gray fibers • Satellite cell are schwann cells that support the nerve body

18. Neurons Key Parts • Soma or cell body contains the nucleus • Nissl bodies are ribosomes found on rough ER • Dendrites(receptors) branch out extensively from cell body, they receive information • Axon, long arm extending away from cell body, transmits signal away from cell body • Axons can have side branched called axon collaterals.

19. Multipolar Most neurons in brain and spinal cord are multipolar Bipolar Only one axon and dendrite Least numerous Found in eye, inner ear and nose Unipolar One end branches toward CNS while the goes toward PNS Two processes form a long axon They are always sensory neurons Structural Classification of Neurons

20. Nerves and Tracts How are individual neurons related to nerves you can see in the body? • Nerve- bundle of nerve tissue in PNS • Tract- bundle of nerve tissue in CNS • Endoneurium surrounds each individual nerve fiber • Fascicles are bundles of fibers • Perineurium surround fascicles • Epineurium holds together fascicles, blood vessels and other tissue to complete the nerve

22. Nerve Repair • Mature neurons cannot replicate • Repair can take place if the damage is not extensive • Cell body and neurilemma(sheath around axon) must remain intact.

23. Nerve Impulses • Membrane potential- is caused by a slight excess positive ions outside the membrane and slight excess of negative ions inside (polarized) • Resting membranepotential (RMP)- normally -70mV • All living cells maintain a membrane potential

24. Nerve Impulse • Gated channels allow for the pumping of Na+ and K+ ions to set up the gradient. • K+ is able to diffuse freely across but Na+ is kept out. • More Na+ ions are pumped outside the cell creating the positive charge on the outside of the cell.

25. Action Potential • A stimulus that reaches the threshold potential triggers Na+ channels to open. • As Na+ enters the cell it causes a wave of depolarization. • Action potential peaks at +30mV and Na+ channels close • After brief hyperpolarization resting potential is restored

26. Action Potential 1. Threshold is met. 3. depolarization. 4. repolarization. 2. Brief hyperpolarization.

27. Refractory Period • Absolute Refractory period- half a millisecond after stimulation the membrane will not respond to any stimulus(during depolarization). • Relative Refractory period- the membrane will respond only to very strong stimuli. • Refractory period ensures that action potential only travels in one direction!!

28. Conduction of Impulse • In myelinated fibers action potential can only occur at the gaps of the myelin sheath (Nodes of Ranvier) • This is called Saltatory conduction and is much faster than unmyelinated fibers. • The larger the diameter the neuron the faster the transmission. http://www.brainviews.com/abFiles/IntHanoi.htm

29. Anesthetics • Many over-the-counter local anesthetics, benzocaine, block the opening of Na+ channels. • How does this prevent pain transmission???

30. The Synapse • Synapse- the junction where signals are transmitted from the presynaptic neuron to a postsynaptic or an effector (muscle)

31. Electrical Synapse Found where cells are joined by gap junctions Allows for continuous flow of action potential Found in cardiac & smooth muscles Chemical Synapse Use neurotransmitters to send signal from pre- to postsynaptic cell. Found in nervous system Types of Synapses

32. Chemical Synapses • Action potential reaches the synaptic knob of the telodendrium and causes the opening of Ca++ channels • Ca++ rushes into the cell triggering the movement of neurotransmitter vesicles to the synaptic knob membrane where they fuse with the membrane. • Once released, the neurotransmitters bind to the postsynaptic neuron’s receptors on its dendrites. • The opening of ion channels can then cause a postsynaptic potential

33. The synapse

34. Neurotransmitters • Excitatory neurotransmitters • Cause both Na+ and K+ channels to open up • This creates temporary depolarization • Excitatory postsynaptic potential (EPSP) • Inhibitory neurotransmitters • Cause K+ and/or Cl- to open up • This creates temporary hyperpolarization • Inhibitory postsynaptic potential (IPSP)

35. Acetylcholine is a very widely distributed excitatory neurotransmitter that triggers muscle contraction and stimulates the excretion of certain hormones. In the CNS, it is involved in wakefulness, attentiveness, anger, aggression, sexuality, and thirst, among other things. Dopamine is an inhibitory neurotransmitter involved in controlling movement and posture. It also modulates mood and plays a central role in positive reinforcement and dependency. Norepinephrine is a neurotransmitter that is important for attentiveness, emotions, sleeping, dreaming, and learning. Norepinephrine is also released as a hormone into the blood, where it causes blood vessels to contract and heart rate to increase. Serotonin contributes to various functions, such as regulating body temperature, sleep, mood, appetite, and pain. Alzheimer’s disease is associated with a lack of acetylcholine in certain regions of the brain. The loss of dopamine in certain parts of the brain causes the muscle rigidity typical of Parkinson’s disease. Norepinephrine plays a role in mood disorders such as manic depression. Depression, suicide, impulsive behaviour, and agressiveness all appear to involve certain imbalances in serotonin. Examples of Neurotransmitters