4Central Nervous System The CNS is composed of the brain and spinal cordSpinal cord connects the brain with the PNSSpinal cord is comprised of cell bodies and axons that carry messagesAfferent: toward the brain (sensory function)Efferent: away from the brain (motor function)
5Peripheral Nervous System The Peripheral Nervous System (PNS) includes all nerves outside the brain and spinal cordSomatic NS carries sensory messages to brain and motor commands to the musclesAutonomic NS regulates automatic body functions (such as heart rate, breathing)Sympathetic: “Fight or Flight”Parasympathetic: dominant when relaxed
8MyelinMyelin is a fatty, waxy substance coating the axon of some neurons.Functions:Speeds neurotransmissionInsulates neurons from each otherMakes neurotransmission more efficient
9SynapseThe synapse is the junction between an axon terminal and an adjacent dendrite or cell body.Neurotransmitter (NT) molecules are released from the axon terminal into the synapse when the action potential arrives at the axon terminal.
10The Synapse Synthesis of neurotransmitter (NT) Storage and transport of NT within vesiclesNT ReleaseActivation of postsynaptic receptorsTermination of transmitter effect (e.g. reuptake)
12Psychoactive DrugsPsychoactive drugs affect the nervous system to alter mood, emotion, and thoughtPsychoactive drugs act by:Increasing or decreasing release of neurotransmittersStimulating or blocking receptor sites
13Psychoactive Drugs Agonists enhance neurotransmitter function Antagonists block neurotransmitter function
15Brainstem Brainstem is a primitive portion of brain Pons: involved in respiration, sleep regulation, dreamingMedulla: involved in life support functions such as respiration and heart rateReticular activating system is an arousal system within the brainstem
16Subcortical Brain Areas Corpus callosum: band of axons that interconnects the hemispheresThalamus: sensory relay areaLimbic system: involved in emotionalityHypothalamus: feeding, fleeing, mating, fighting, homeostasisCerebellum: involved in motor controlSubcortical Brain Areas
17HYPOTHALAMIC REGULATION OF PHYSIOLOGIC FUNCTIONS Water and electrolyte balanceTemperature regulationActivation of sympathetic nervous systemThirst and regulation of drinkingHunger, satiety and regulation of feedingRegulation of sexual behaviorRegulation of circadian rhythmsPituitary hormone secretion
18HYPOTHALAMUS CONTAINS “BIOLOGIC CLOCK” Hypothalamus plays a major role in regulating biologic rhythmsRhythms persist in absence of time cuesCircadian or diurnal rhythms repeat dailyExternal signals of light and darkness serve to entrain the internal clock to a 24 hour dayBiologic clock is located in the suprachiasmatic nucleusInput is received from the eye by the retinohypothalamic tract of the optic nerve
20Limbic System The fornix is a C-shaped bundle of fibres (axons) in the brain, andcarries signals from the hippocampusto the mammillary bodies andseptal nuclei.The amygdala is an almond-shaped group of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Primary role in the processing and memory of emotional reactions and considered part of the limbic system.The hippocampus plays important roles in long-term memory and spatial navigation. Like the cerebral cortex, with which it is closely associated, it is a paired structure, with mirror-image halves in the left and right sides of the brain.
21LIMBIC SYSTEM FUNCTIONS BRAIN REWARD SYSTEMSElectrical stimulation of various sites in the limbic system produces either pleasurable (rewarding) or unpleasant (aversive) feelingsDopaminergic neurons play a major role in mediating rewardAGGRESSIONStimulation of sites in hypothalamus and amygdala elicits a fight or flight reaction and postures of rage and aggressionSevering the cortical connections to the limbic system results in permanent rage postures and aggressivenessSEXUAL ACTIVITYLimbic system in general coordinates sex drive and mating behaviorHigher cortical centers exert more or less overriding influences
22MEMORY AND LEARNINGMost likely sites are large association areas of the cerebral cortex working in association with subcortical structures as hippocampus and amygdalaPrefrontal cortex is important for coordinating formation of memoryHippocampus is important in consolidating memoryAssociation cortices are important in storing memoriesShort term memoryProduct of working memory-prefrontalcortexLong term memoryInvolves limbic system input
23Cerebral Cortex Cortex refers to the outer covering of the brain Consists of left and right hemispheresCortex is divided into lobesFrontal: Self-awareness, planning, voluntary movement, emotional control, speech, working memoryParietal: Body sensationsOccipital: VisionTemporal: Hearing, language comprehension