PSY 390 Neurophysiology-3.pptx

PSY 390 Dr. Koncsol NEUROPHYSIOLOGY NEUROPHYSIOLOGY 10-15 BILLION functional cells known as NEURONS 1. Do not regenerate themselves 2. Unique morphology 3. Unique inter-cellular spaces called synapses 4. Evolutionary insulation called myelin 5. Unique cellular function i.e., communication NEURO...

PSY 390 Dr. Koncsol NEUROPHYSIOLOGY NEUROPHYSIOLOGY 10-15 BILLION functional cells known as NEURONS 1. Do not regenerate themselves 2. Unique morphology 3. Unique inter-cellular spaces called synapses 4. Evolutionary insulation called myelin 5. Unique cellular function i.e., communication NEUROPHYSI OLOGY 100-150 BILLION structural cells known as GLIAL CELLS Two types of NEUROGIA: CNS & PNS glial cells I. CNS glial cells A. oligodendroglia: connects neuron+ neuron B. astroglia: connects neurons+ blood vessels C. microglia: nurse cells, move to damage II. PNS glial cells A. neurolemma (oligodendroglia) NEUROPHYSI OLOGY 1. Schwann cells 2. produce myelin B. satellite cells (astroglia) 1. nurse cells 2. migrate to damaged cells for repairs C. PNS glial disorder: multiple sclerosis (MS) progressive deterioration of myelin (autoimmune disease) STRUCTURE OF THE NEURON NEUROPHYSI OLOGY I. Cell body- soma-perikaryon II. Dendrites-receptive processes III. Axons- transmitter processes IV. Synapse-synaptic cleft V. Neurotransmitters-excitatory and inhibitory I. NEUROPHYSI OLOGY CELL BODY (4-5 to 50-100 microns): A. Nucleus: with single nucleolus: DNA/RNA B. Organelles: mitochondria, ER, Golgi, etc C. Cytoplasm: with inclusions e.g., Nissl bodies D. neurofibrils/microtubules (implicated in Alzheimer’s disease) E. Pigmentation: melanin, lipochrome NEUROPHYSI OLOGY II. DENDRITES A. Number: multiple, one, or none extensions of the cell body B. Receptors; increase surface area of cell to receive neurotransmitters C. Dendritic spines; found on the dendrites D. Variable connections with other neurons NEUROPHYSI OLOGY III. AXONS A. Unipolar B. Extension of cell body C. Co-lateral branches D. Axonal endings, terminals, telodendria E. Synaptic knobs containing synaptic vesicles F. Neurotransmitters contained in vesicles NEUROPHYSI OLOGY IV. Neuronal Junctions (Types of Synaptic connections) A. axodendritic- axon to dendrite B. axoaxonic- axon to axon C. axosomatic- axon to cell body D. dendrodenritic- dendrite to dendrite E. No dendrosomatic junctions NEUROPHYSI OLOGY V. Special Properties of Neurons A. Do not undergo mitosis B. Extra chromosomes- tetroid number C. Types: sensory, motor, association D. Degeneration 1. anterograde-(Wallerian)- loss of distal part (axon) 2. retrograde-loss of cell body 3. transneuronal-loss of neighboring neuron NEUROPHYSI OLOGY E. Regeneration 1. neurobiotaxis-only in the PNS 2. stem cell placement-only in the CNS F. Synapsis (connections with other types of cells) to: 1. sensory receptors 2. muscles 3. glands 4. other neurons NEUROPHYSI OLOGY VI. Synapse (means to clasp in Greek) A. Structure 1. presynaptic cell (membrane) 2. postsynaptic cell (membrane) 3. sub-synaptic web 4. width: 200 Angstrom units (1/10 billionth of a meter) NEUROPHYSI OLOGY VII. AXONAL CONDUCTION A. Properties of neuron: 1. depend on its semipermeable membrane 2. function to allow electrical conduction within the cell 3. are evidence the neuron is a living battery 4. function to allow synaptic transmission from cell to cell B. Stages of Axonal Conduction 1. resting potential—polarization NEUROPHYSI OLOGY 2. action potential—depolarization 3. refractory phase— hyperpolarization 4. resting potential—repolarization C. Chemical components involved: 1. sodium (NA+) 2. potassium (K+) 3. negative anions (A-) 4. chlorine (Cl-) D. Research origins 1. H. von Helmholtz’s experiment (1890s) NEUROPHYSI OLOGY 2. N. Bernstein’s theory: 3’/sec vs 2000’/sec (1930s) 3. J.Z. Young’s giant squid research (1960s) E. Theoretical model 1. cell has a semipermeable membrane 2. with active channels that have “filters” and “gates” 3. and passive channel with “filters” but no “gates” NEUROPHYSI OLOGY F. Active channels--Na+ channels 1.Each contain a “filter” based on the size of an ion 2. Each contains a “gate” based on the charge of an ion 3. Gates controlled by neurotransmitters 4. Filters & gates work together to determine if Na+ enters the cell 5. certain poisons (neurotoxins) work to open all Na+ gates NEUROPHYSI OLOGY G. Neuronal Conduction 1. Initiated by all or none, either/or process 2. Sequential depolarizationdomino effect 3. Begins at the axon hillock 4. Saltatory or discrete conduction 5. Result of presynaptic summation a. spatial b. temporal NEUROPHYSI OLOGY VIII. SYNAPTIC TRANSMISSION A. Requires release of neurotransmitters (NTs) B. Neurotransmitters (NTs) either: a. excitatory b. inhibitory C. Must travel across a synaptic cleft (200 A units—20-30 nm) D. Affected by presynaptic facilitation/inhibition NEUROPHYSI OLOGY E. Neurotransmitter-Cell receptor site reaction involving: a. protein receptor affinities b. binding sites c. lock & key analogy IX. Neurotransmitter (NT) classification A. Adrenergic NTs B. Cholinergic NTs C. Other types of NTs IX. NEUROTRANSMITTERS A. Pioneer investigators: NEUROPHYSI OLOGY 1. John Eccles -Nobel Prize 1963 2. Bernard Katz- Nobel Prize 1970 3. Earl Sutherland-Nobel Prize 1971 B. Four functions of neurotransmitters: 1. production 2. release 3. mechanism of action (MOA) 4. clearance (elimination from the synapse) C. Four research questions regarding neurotransmitters: NEUROPHYSI OLOGY 1. What is their chemical composition? 2. Where are they found in the nervous system? 3. How exactly do the work? 4. What happens to them ultimately? D. Four answers: 1. NTs are complex chemical compounds known as: NEUROPHYSI OLOGY amino acids, polypeptides, histamines 2. NTs found in varied locations in the PNS and CNS 3. NT mechanisms of action (MOAs) depend on active channels with filters and gates and passive channels with no gates; locks & keys analogy 4. NT clearance: the processes of degradation and reabsorption NEUROPHYSI OLOGY X. NT Production & Storage A. Production 1. cell body (axonal transport; enzymes) 2. axon (retrograde transport; nutrients) 3. 2-way traffic via passageways known as neurotubules B. Storage 1. in the axon terminals within the synaptic knobs 2. within the synaptic vesicles XI. NT Release 1. a neural impulse opens the: NEUROPHYSI OLOGY Na+ channels and the Ca+ channels in the axon terminal endings 2. Ca+ ions enter cell and move synaptic vesicles in process known as exocytosis (cell vomiting) releasing neurotransmitter stored within 3. neurotransmitter travels across synapse 4. neurotransmitter regulated pre vs post synaptic membranes XIII. NT channels mechanism of action (MOA): A. Gated channels open two ways: NEUROPHYSI OLOGY 1. directly and immediately or 2. indirectly and slowly via two “messengers” (types of “keys”) a. 1st messenger ATP (adenosine triphosphate) b. 2nd messenger cAMP (cyclic adenosine monophosphate) B. specific receptor cites for protein binding (specific keys for specific locks. C. Protein binding (specific locks & specific keys analogy): NEUROPHYSI OLOGY 1. produces change in post synaptic membrane to permeability to: Na+, Ca+, and K+ 2. which triggers a neural impulse cycle 3. Neurotransmitter binding to receptor cite (the lock) then changes the shape of protein molecule gate (the key) which leads to the release of neurotransmitter which sends information to the 4. next neuron XIV. Neurotransmitter Removal/Elimination from the synapse NEUROPHYSI OLOGY A. Degradation (enzymatic) where the NT is “destroyed” via a co-enzyme (an assassin) released simultaneously, or B. Reuptake where the NT is drawn back into the vesicle of the presynaptic membrane C. Removal is necessary and inevitable D. Reuptake method is more efficient NEUROPHYSI OLOGY XV. Neurotransmitter initial classification (circa 1970) A. Cholinergic NTs: 1. Acetylcholine (Ach) 2. Cholinesterase (AChE) B. Adrenergic NTs: 1. Catecholamines (Norepinephrine, Epinephrine, Dopamine) 2. Indolamines (Serotonins) C. Other NTs VI. Cholinergic NTs and their cholinergic receptor sites NEUROPHYSI OLOGY A. Ach is manufactured presynaptically in the: 1. CNS: motor cortex, midbrain, medulla 2. PNS: parasympathtic endings 3. SNS: neuromuscular junctions B. AChE is manufactured in the same locations C. Ach & AchE receptor sites found concomitantly in all locations ACh & AChE receptor sites: 1. Type #1 found at motor end plates (affected by the poison curare) NEUROPHYSI OLOGY 2. Type #2 found on smooth and cardiac muscles affected by the drug atropine used in surgery 3. Type #3 found in the autonomic parasympathetic ganglia and affected by the drug hexamethonium used to treat hypertension VII. Adrenergic NTs and their receptor sites: NEUROPHYSI OLOGY Adrenergic NT manufactured presynaptically by oxidation (using MAO) and methylation (using COMT) A. Norepinephrine (NE) also known as Noradrenalin is: 1. excitatory 2. released pre-synaptically in sympathetic NS 3. a vasoconstrictor in the PNS 4. a dialator of the coronary arteries B. Epinephrine also know as Adrenaline is: 1. excitatory NEUROPHYSI OLOGY 2. released from sympathetic NS & adrenal medullas 3. produces the classic fight or flight response 4. is a vasoconstrictor used to stop hemorrhages, allergic reactions 5. is an anti-asthmatic medication (found in inhalers) 6. is a cardiac stimulant used to resuscitate the heart NEUROPHYSIOL OGY C. DA (Dopamine) 1. found in the basal ganglia, nucleus accumbens (pleasure center) of the brain 2. DA release responsible for addiction to all drugs which produce euphoria 3. also manipulated in antidepressant medication e.g., Wellbutrin D. Serotonin (5-HT) is: NEUROPHYSI OLOGY 1. manufactured in the CNS: cortex, cerebellum, hypothalamus 2. is derived from the chemical sequence: Tryptophan becomes 5Hyproxytraptophan becomes 5Hydroxytryptamine (serotonin) 3. regulates mood, sleep, temperature 4. is the active ingredient in most antidepressants known as SSRIs selective serotonin reuptake inhibitors NEUROPHYSI OLOGY D. Other Neurotransmitters are: 1. GABA (Gamma Amino Butyric Acid): a. found in the basal ganglia, cerebellum, spinal cord b. is a major inhibitory NT in the brain c. is the MOA for most inhibitory drugs e.g., alcohol, sedatives, and anxiolytics NEUROPHYSI OLOGY 3. Glycine a. found in the spinal cord b. is inhibitory exclusively 4. Substance P (P = pain) a. found in the cerebral cortex, spinal cord b. is excitatory exclusively 5. Glutamic acid a. found in the sensory cortex b. is excitatory exclusively NEUROPHYSI OLOGY 6. Endorphins and Enkephalins a. found in the hypothalamus, thalamus, brainstem, spinal cord b. is inhibitory and involved in pain reduction throughout the body c. can be both excitatory and inhibitory dependent on location d. is a contraction of “endogenously produce morphine”