Neuroscience.ppt

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Neuroscience.ppt

  1. 1. Neurophysiology, Neuroanatomy
  2. 2. The brain is a combination of two types of cells, glial cells and neurons The brain consists of 100 billion neurons and 1012 total cells
  3. 3.  Cells in the brain that communicate with each other  Neurons are “born” early in life  Limited regeneration
  4. 4.  Provide support for neurons ◦ Structure support ◦ Metabolic and nutritional support  Can replace themselves  Serve to clean up the brain, removes dead tissue and foreign objects  Play a large role in neural development  May even be communicating with neurons  Role is expanding with new research
  5. 5. Pyramidal neuron Purkinje neuron
  6. 6.  Neurons communicate in two ways  Electrical signal: within a neuron  Chemical signal: between neurons  Electrical signal is sent from one part of the neuron to the other: The signal travels from the dendrite through the cell body to the axon ◦ Dendrites receive the signal from another neuron ◦ Axons send the signal to other neurons  Chemical signal is sent from the axon of one neuron to the dendrite of another neuron
  7. 7.  Neurons contain many ions and are charged A- are large protein ions that always stay inside the cell K+ is potassium. At rest it is mostly inside the cell Cl- is chloride. It exists both inside and outside the cell Na+ is sodium. It exists primarily outside the cell
  8. 8.  When the cell is at rest (i.e., not doing anything), it has a charge of -70 mV. This is called the resting potential.  Because of the cell properties, many forces are acting on the cell.  1. Diffusion - substances tend to move from areas of high concentration to areas of low concentration.  2. Like charges repel each other and opposite charges attract  Charges stay the way they are because of the cell membrane. It is selectively permeable. It does this by ion channels.
  9. 9.  Normally, membrane closes Na+ channels  However, if the membrane is given an electrical charge, it causes the membrane to lose some permeability  This opens the sodium channels  If this electrical charge is large enough, the flood gates will open  Change in charge is potentiated down the length of the neuron  This wave of charge is called the action potential
  10. 10.  Once sodium has rushed in, the cell quickly regains its composure  Active process in which sodium is removed from the cell  Sodium is exchanged for potassium  Requires metabolic activity  Returns charge inside cell to -70 mV  Refractory period
  11. 11.  When the action potential reaches the terminal button, it causes a release of chemicals called neurotransmitters  These neurotransmitters are dumped into the synapse, the space between the axon of one neuron and the dendrite of another
  12. 12.  Neurotransmitters come into contact with membrane of the other neuron  Receptors on the dendrite detect the neurotransmitter  NT binds to the receptor  This causes a temporary change in the membrane, allowing a little sodium inside the cell  This small charge is called the graded potential  This is passed on to the axon and it summates
  13. 13. When the sum of the potentials reaches the base of the axon, a sufficient charge may be present to cause an action potential.
  14. 14.  Myelin – a layer of proteins that are wrapped around the axon.  Two functions: to protect the axon, and to speed up transmission  Without myelin, neural transmission is inefficient  Multiple Sclerosis – an autoimmune disorder in which the myelin is destroyed. ◦ Fatigue, pain, motor disorders, cognitive disorders, etc.
  15. 15.  After the NT is initially released, the chemical must be removed  This is done in a couple of different ways ◦ Biochemical breakdown of the NT ◦ Reuptake: NT is pulled back into the presynaptic button and packaged to be released again
  16. 16.  Excitatory ◦ Glutamate ◦ Acetylcholine  Inhibitory – What does this mean? ◦ GABA ◦ Norepinephrine  Both ◦ Dopamine ◦ Serotonin
  17. 17.  Psychopharmacology- the study of how drugs affect behavior  Nearly all drugs work by affecting neurotransmitter release
  18. 18. Prozac is an example of a SSRI – a selective serotonin reuptake inhibitor
  19. 19.  Alcohol ◦ Activates GABA receptors  Nicotine ◦ Activates acetylcholine receptors ◦ Changes overall number of ACH receptors  Cocaine / crack ◦ Blocks reuptake of dopamine ◦ Stimulates release of dopamine ◦ Anesthetic effect on cells  Amphetamine / Methamphetamine ◦ Similar to cocaine with no anesthetic effect
  20. 20.  Heroin ◦ Activates opiate receptors  Marijuana ◦ Activates cannabinoid receptors (similar to opiate)  Ecstasy (MDMA) ◦ Selectively destroys neurons that release serotonin ◦ Serotonin is dumped out when the cell dies
  21. 21.  Central Nervous System: Includes Brain and Spinal Cord
  22. 22.  Peripheral Nervous System: All other neural tissue. Specifically, the periphery. This includes muscles, the skin, and even the organs  PNS broken down into two parts 1. Somatic nervous system: nerve fibers that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle.
  23. 23. 2. Autonomic nervous system – Controls the "insides" (the "viscera") of our body, like the heart, stomach and intestines - functions in an involuntary, reflexive manner - does things like constrict blood vessels, dilate pupils, and even makes our heart beat fast on a roller coaster, etc. -Has two components - A. Sympathetic nervous system: - B. Parasympathetic nervous system
  24. 24.  Sympathetic NS- Regulates “Fight or Flight” ◦ Prepares the body during stressful situations ◦ Increases heart beat, blood pressure, speeds breathing, slows digestive function  Parasympathetic NS – Regulates "rest and digest" ◦ Keeps the body running calmly ◦ Shuts down the sympathetic NS when the situation becomes less stressful
  25. 25.  Spinal Cord: Two types of material, white matter (Axons) and grey matter (cell bodies)
  26. 26.  Spinal cord relays sensory and motor information to and from the brain  Controls reflexes ◦ Ex. Knee jerk reflex, pain reflex
  27. 27.  Afferent neurons: neurons that send their signal TOWARDS the spinal cord  Efferent neurons: neurons that send their signal AWAY from the spinal cord  Reflex involves two neurons, one afferent and one efferent  Reflexive action takes place before it is sent to the brain  Allows for extremely efficient processing
  28. 28.  3 major divisions 1. Hindbrain: Cerebellum; Pons; Medulla 2. Forebrain: Cortex, amygdala, hippocampus, thalamus, hypothalamus 3. Midbrain
  29. 29.  Cerebellum: Extremely large area, millions of neurons ◦ Responsible for coordination of movement ◦ Plays a role in learning  Pons ◦ Important for sleep and especially dreaming  Medulla ◦ Controls all vital functions of the body including breathing and heart rate
  30. 30.  Thalamus ◦ Primary relay station of the brain ◦ Almost all sensory information passes through before going elsewhere  Hypothalamus ◦ Regulates autonomic nervous system ◦ Regulates hormones, “4 F’s”; Feeding, Fighting, Fleeing, and sexual behavior  Amygdala ◦ Responsible for many aspects of emotion ◦ Emotional learning
  31. 31.  Hippocampus ◦ Especially important for learning and memory ◦ Resolving conflict  Cerebral Cortex ◦ Does just about everything ◦ Many think that the cortex is what makes humans the way they are ◦ Cortex is broken up into 4 lobes:  Frontal lobe: the front of the brain  Temporal lobe: side, the temples  Parietal lobe: kinda middle portion  Occipital Lobe: very back
  32. 32.  Frontal lobe ◦ Important for planning ◦ Thinking / decision making ◦ Primary motor cortex: Generation of movement ◦ Broca’s area: Production of Speech  Temporal lobe ◦ Audition ◦ Wernicke’s area: Language comprehension
  33. 33.  Parietal lobe ◦ Somatosensory function (touch, vibration, pain) ◦ Combination of all senses with vision  Occipital lobe ◦ Vision: Primary visual cortex
  34. 34.  Brain is actually two different halves. It is split down the middle, with the right and left side being very similar to the other  The two hemispheres are connected by the corpus callosum: a bunch of axons
  35. 35.  Each side of the brain controls the opposite side of the body. ◦ Ex. Moving right arm controlled by the left side of the brain.  Systematic differences in right vs. left.  Most language and music on the left. ◦ Somewhat different for left-handed people  The right hemisphere more involved with visual imagery and creativity.
  36. 36.  Sometimes the corpus callosum of a person is cut. It is often surgically cut in patients with severe epilepsy.  Allows for the study of the role of each hemisphere  Experiments have found crazy strange results
  37. 37.  Many techniques can be used to study the brain of animals  Lesioning of the brain ◦ Electrical lesions- electricity is passed through an electrode until neurons die ◦ Chemical lesions- inject chemicals like acid to kill neurons  Injection of drugs
  38. 38.  In Vitro analysis: “In the Lab” – brain tissue is removed, isolated, and studied on its own. Individual neurons can be studied  In Vivo analysis: “In the Living” – the brain is studied in an intact animal
  39. 39.  EEG: electroencephalogram – electrodes are placed on the scalp. ◦ It records the electrical activity of neurons. ◦ Problem: It records from thousands of neurons at a time; not very precise
  40. 40.  “CAT” scan: Computerized tomography ◦ Computer enhanced 3-D X-Rays ◦ Not much resolution, still life
  41. 41.  MRI: Magnetic resonance imaging – uses magnetic fields to get brain scans ◦ Just get a picture
  42. 42.  PET scan: Positron Emission Tomography – patients are injected with radioactive glucose. The scanner tracks where the glucose moves to. This is used as an indicator of neural activity. - Has problems: very expensive, resolution is fairly low.
  43. 43.  Functional MRI (fMRI) – Registers changes in the metabolism of cells ◦ Get 3-D picture of real time brain activity ◦ Very expensive

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