Neurotransmitter: dopamine. Physiology of additive drugs. Dopamine and reward. Neurotransmitter: dopamine

Transcription

1 Physiology of additive drugs Cocaine, methamphetamine, marijuana, and opiates influence the neurotransmitter dopamine. Neurotransmitter: dopamine Dopamine - a neurotransmitter associated with several functions, including muscle control and feelings of reward axon terminal of dopamine neuron Neurotransmitter: dopamine Dopamine - a neurotransmitter associated with several functions, including muscle control and feelings of reward Schizophrenia, manic depression are associated with too much dopamine. Antipsychotic drugs block dopamine receptors. reward pathways To signal the pleasure center here Dopamine and reward Neurons here use dopamine 1

2 Neurotransmitter: dopamine Cocaine and methamphetamines prevent reuptake of dopamine. Neurotransmitter: serotonin Neurons using serotonin are associated with mood, sleep, & appetite Antidepressants often enhance levels of serotonin (Zoloft, Prozac, Paxil) Three main neurotransmitters of mood All are monoamines Neurotransmitter: serotonin Ecstasy temporarily increases serotonin, but body makes less serotonin in response ecstasy blocking reuptake of serotonin 2

3 Cannabis effects THC binds to cannabinoid (CB) receptors, mimicking endocannabinoids (from body) (anadaminde, arachidonate lipids) CB receptors are in pleasure pathway (VTA), motor coordination (cerebellum) and memory (hippocampus) areas Signaling bw neurons during learning is disrupted (GABA neurons w CB1 receptors) What makes drugs addictive? Drug tolerance occurs because the body tries to maintain homeostasis in presence of high neurotransmitter levels What makes drugs addictive? Repeated drug use causes elevated dopamine Body decreases # dopamine receptors, dopamine prod n Down regulation Dopamine receptors Normal Abuser 3

4 Study showing down regulation What makes drugs addictive? Now a higher dose is necessary for high Repeated doses of morphine reduce # of dendrites in dopamine neurons Normal happy increases in dopamine can t stimulate pleasure bc the pleasure center is badly altered Endocrine system Hormones are transported by the blood, but only cause responses in target cells Regulation of growth and development Homeostasis - ex: salt/water balance, stress, metabolism Reproduction Endocrine functions 4

5 Types of hormones Amines use tyrosine (epinephrine and norepinephrine) Types of hormones Steroids - from cholesterol (adrenal cortex, testis, ovary and placenta). Hydrophobic, transported by proteins Peptides (oxytocin, vasopressin, GH, insulin, TSH) Both types are water soluable How do hormones signal cells? Steroid and thyroid hormones activate genes Diffuse freely into and out of cells Receptor proteins are in cytoplasm. Hormone binds and moves inside nucleus How do hormones signal cells? Peptide hormones utilize a 2 nd messenger mechanism Target cells have specific receptor for hormone on cell surface, which triggers 2 nd messenger 5

6 Comparing the two systems Nervous system - signals sent via specific wiring rapid, precise responses Endocrine system - specificity is at the receiving end overall body responses, effect may take hours Fig. 5-1, p. 108 Neuroglia Most CNS cells are glial cells They provide structure and maintain interneurons in the CNS Are capable of dividing, even in adulthood nuclei of glial cells neuron Fig. 5-2, p

7 Astrocytes: hold neurons together establish a blood-brain barrier w/capillaries repair brain injuries breakdown some neurotransmitters take up excess K + from the brain ECF Microglia are the immune defense of the CNS Oligodendrocytes form myelin sheaths around axons Ependymal cells line the internal cavities of the CNS. MS involves oligodendrocytes Multiple sclerosis immune system targets oligodendrocytes, causing degeneration of myelin in CNS Cranial meninges Scalp Skull Dura mater Arachnoid Pia mater Arachnoid mater Subarachnoid space of brain Brain 7

8 Ventricles Right lateral ventricle Left lateral ventricle Third ventricle Cerebral spinal fluid (CSF) provides almost neutral balance for brain (it floats ) cushions and nourishes brain produced by tissue in ventricles Fourth ventricle CSF produced in ventricles and resorbed in venus sinus Hydrocephalus 8

9 Meningitis Meningitis: infection, inflammation of meninges - viral or bacterial. Why is it often difficult to deliver drugs to the brain? Bacterial infections are quite serious and can result in encephalitis, brain damage, death. Blood brain barrier Exists at capillaries that serve the brain Capillaries have tight junctions Normal capillary Lipid-soluble substances BBB capillary Carrier-mediated transport What molecules pass through the blood brain barrier? Lipid soluble vs. water soluble Brain infections are generally rare, but harder to fight when established (antibodies can t pass) Water-lined pore Astrocyte processes Tight junction Lipid-soluble substances Meningitis 9

10 How can drugs pass through the blood brain barrier? The BBB makes it difficult for drug treatments to enter brain Not everything can be small, lipid soluble Via nanotechnology, engineered molecules may carry treatments otherwise water soluble gray matter white matter (posterior) (anterior) Table Cerebral 5.3 (1) cortex Page 144 Basal nuclei Cerebrum Cerebral cortex Basal nuclei Cerebrum Cerebral cortex is highly convoluted, outer layer of gray matter. It covers an inner core of white matter. An inner core of basal nucleii are located deep within the white matter. 10

11 Receives somesthetic sensations and proprioreception Parietal Temporal Occipital Temporal Occipital Parietal Frontal Voluntary motor activity, speech, thought Primary motor cortex Frontal Central sulcus Temporal Occipital Somatosensory cortex Parietal 11

12 Figure 5.11 (2) Page 149 Sensory homunculus Motor homunculus Left hemisphere Temporal Diencephalon Hypothalamus Controls much of the endocrine system via pituitary gland Thalamus - performs some sensory processing, transmits signals to higher areas Pineal linked with circadian clock Thalamus Diencephalon 12

13 Table 5.3 (1) Page 144 Midbrain Pons Cerebellum Cerebellum Brain stem and cerebellum Brain stem - Controls basic functions: breathing, heart rate, digestion, etc. Cerebellum maintains balance, enhances muscle tone, and coordinates skilled muscle activity Brain stem Midbrain Pons Medulla Brain stem Medulla Reticular activating system How long should sleep last? Visual impulses Reticular formation Brain stem Auditory impulses Humans generally require 7-8 hours of sleep 10% require more 5% require less (some have mutation on DEC2 or BHLHE41 genes). They have reduced sleep but no less NREM sleep Spinal cord 13

14 Posterior parietal cortex transforms visual information into movement commands Premotor cortex Prefrontal cortex Frontal Parietal Temporal Posterior parietal cortex Occipital Associative areas: Prefrontal (association) cortex - plans voluntary activity, decision-making, creativity, and personality traits. Cerebellum Then the pre-motor cortex (w/ neighboring area) will orient the body, help plan and coordinate movements Muscle movement Areas that communicate to the 1 o motor cortex to control voluntary movement Prefrontal cortex Premotor cortex Posterior parietal cortex Pre 14