Psychobiology

A &P of the Human Nervous SystemThe nervous system is composed of two separate but interconnected divisions:Central Nervous System (CNS)Composed of the brain and the spinal cordUnderstanding of mental d/os involves in-depth understanding of the structure and function of the CNSPeripheral Nervous System (PNS)Contains peripheral nerves and includes cranial nerves starting from just outside the brain stem

NeuroanatomyI. CerebrumA. Cortex1. Frontal lobe2. Parietal lobe3. Occipital lobe4. Temporal lobe

Neuroanatomy (cont)II. DiencephalonA. HypothalamusB. ThalamusC. Pineal bodyIII. CerebellumIV. BrainstemA. PonsB. Medulla oblongataC. Reticular activating systemD. Midbrain

Neuroanatomy (cont)V. Basal GangliaVI. Limbic systemA. Hippocampus

CerebrumLargest part of the brainDivided into left and right cerebral hemispheresEach hemisphere is further subdivided into 4 lobes:FrontalParietalTemporal Occipital

Cerebrum (cont)Effective coordinated activity requires communication between the two hemispheresThe hemispheres are connected by the corpus callosum, a large bundle of white matterThe corpus callosum allows each hemisphere of the brain to send and receive information to the other hemisphere

Cerebral CortexThin layer of gray matter that makes up the surface of the 2 cerebral hemispheresThe outermost surface of the brain cortex contains corrugated wrinkles with many grooves and indentationsSulcishallow groovesFissuresdeeper grooves extending deep into the brainGyrithe raised areasAll give the brain its characteristic look and provide landmarks

4 LobesFrontal lobeTemporal lobeOccipital lobeParietal lobeMany of the sx of mental illness can be understood as a disturbance in functioning of 1 or more of these lobes

Frontal Lobe(Thought Processes)

Frontal LobeFormulate or select goalsPlanDecision makingInsightMotivationSocial judgmentExpression of moodVoluntary motor ability starts in the frontal lobe

Frontal Lobe (cont)Neurospych testing and brain imaging studies indicate that the frontal lobe seems to be involved in:SchizophreniaOCDMood disordersADHDDementias

Temporal Lobe(Auditory)

Temporal Lobe Receives and processes auditory informationLanguage comprehensionStores sounds into memory (language, speech)

Occipital Lobe(Vision)

Occipital LobeReception and integration of visual input

Parietal Lobe(Sensory and Motor)

Parietal Lobe Receive and identify sensory informationability to read, to understand spoken language Proprioception and body awarenessAbstractionReading mathematics

Structures of the DiencephalonHypothalamusThalamusPineal Gland

Hypothalamus

HypothalamusHouses the pituitary gland and serves as a major control center for maintaining physiological homeostasisRegulates some of the most basic human functionsSleep-rest patternsBody temperaturePhysical drives of hunger and sex

Thalamus

ThalamusA regulatory structure that acts as a gateway to the cerebral cortexRelays all sensory info, except smell, from the PNS to the CNSHelps filter incoming info to prevent the cortex from being overloaded

Pineal Gland

Pineal GlandSecretes melatoninPossibly regulates sleep-wake cycle

Cerebellum

CerebellumLocated in the posterior part of the brain behind the brainstemCoordinates equilibrium, muscle tone, postural control, and voluntary muscle activity

BrainstemConnects the spinal cord to the brain and contains the control center for vital cardiac and respiratory functionsComposed of:Pons Medulla oblongataRASMidbrain

Brainstem (cont)MidbrainUnconscious regulation of motor activityContains part of the basal ganglia which manufactures the NT dopaminePonsRelay between the cerebrum and cerebellumSite of production for most of the brains NE

Brainstem (cont)Medulla oblongataResponsible for conscious control of skeletal muscle and is involved with balance and coordinationReticular activating systemStimulation of this area activates the cortex into a state of alert wakefulness

Basal Ganglia

Basal GangliaMade up of cell bodies closely involved with motor functions and associationInvolved in learning and programming of behaviorFor example: complex activities such as driving or eating become so engrained that one does not have to think consciously to perform them

Basal Ganglia (cont)Extrapyramidal motor system Muscle tone, common reflexes, and automatic motor functioning of walking (posture) are controlled by this trackThis track works by maintaining a balance between excitatory and inhibitory neuronsDiseases such as Parkinsons and Huntingtons cause dysfunction of this motor track and produce abnormal muscle movementsAntipsychotics also cause an alteration in functioning of the basal ganglia and produce side effects

Limbic System

Limbic SystemInstincts, drives, needs, and emotions are considered functions of the limbic systemStructures of the limbic system include:AmygdalaHippocampus

Amygdala

AmygdalaModulates common emotional states such as feelings of aggression and anger, love, and comfort in social settingsSexual arousal and aggression are also controlled by the amygdalaResearchers are looking into the misfirng of neurons in the amygdala and the development of bipolar d/o

Hippocampus

Hippocampus

Plays a major role in the encoding, consolidation, and retrieval of memoriesDamaged in Alzheimers disease

Neurophysiology

NeurophysiologyStructural features of neurons:1. Cell body2. Axon (stem)transmits signals from the neurons cell body to connect with other neurons and cells3. Dendritescollect incoming signals from other neurons and send the signal to the neurons cell body

Basic Properties of Neurotransmission

Synthesis and Storage of NTsMost NTs are stored in the terminal region of the neuronNTs are often synthesized from chemicals in our dietsBefore released into the synapse, NTs are stored in membranous sacs called vesicles which protects them from being destroyed by enzymes

Release and Response of NTsNTs are released from the nerve terminal following electrical stimulationinward movement of Na+ followed by outward movement of K+After being released, a NT binds to a receptor (a unique protein found in the membrane of a neuron)The analogy of a lock and key describes this relationshipThe lock is the receptor and the key is the NT

Release and Response of NTs (cont)After the receptor is bound, the action of the 1st message, the NT, is converted into action by a second messenger.Second messenger systems can be described as the effects of a single NT being amplified through the subsequent activation of multiple systemsThe effects of 2nd messenger systems last longer and the process is called neuromodualtion

NeurotransmittersNTs can carry 2 different types of messages:ExcitatoryInhibitoryNerve cells stimulated by an excitatory NT will be turned on or stimulated to start some actionThose stimulated by an inhibitory NT will be turned off causing slowing or stopping actions

NTs common in Mental Disorders5 NTs are important to the understanding of mental disorders:Acetylcholine (Ach)Dopamine (Da)Norepinephrine (NE)Serotonin (5-HT)Gamma-Aminobutyric acid (GABA)

Acetylcholine (Ach)Formation of Ach depends on the dietary intake of its precursor choline (red meat, vegetables)Can have an excitatory or inhibitory effectThe role of Ach in the brain is to mediate cognitive function

Acetylcholine (Ach) Decreased Ach is thought to produce the memory impairing effects of Alzheimers disease (AD)This is the reason Aricept is useful in treating ADAricept inhibits cholinesterasethe enzyme that breaks down AchThis increase the amount of Ach

Acetylcholine (Ach) 2 types of Ach receptors:MuscarinicWhen muscarinic receptors are blocked, pts experience anticholinergic side effectsNicotinicActivity at nicotinic receptors has been shown to improve learning and memory performance

Dopamine (Da)

Dopamine is synthesized from the amino acid tyrosineGenerally has an excitatory effect

Dopamine (Da)Da receptors are classified into 2 main families, D1 and D2The D2 receptor family is inhibitory and is the target of the antipsychotic medsDa levels are thought to be increased in pts with schizophrenia and maniaDrugs used to treat schizophrenia act to decrease Da levels or transmissionDa levels are decreased in pts with depression

Norepinephrine (NE)Generally excitatoryMost prevalent NT in the bodyHas 2 main receptor subtypes:AlphaBeta

Norepinephrine (NE)Drives the sympathetic nervous system fight or flight responseStudies indicate that pts suffering from depression have decreased NEResearch also shows that excess NE increases startle reactions and aggression and has been implicated in mania and anxiety d/os

Serotonon (5-HT)Mostly inhibitorySynthesis of 5-HT requires dietary intake of tryptophanPlays a role in sleep regulation, hunger, mood states, and pain perceptionPlays a role in aggression and sexual behavior

Serotonon (5-HT)Low levels of 5-HT have been implicated in depression, aggression, and violent suicide attempts5-HT is structurally similar to LSDThis has led researchers to hypothesize that 5-HT is also dysregulated in psychosis

Gamma Aminobutyric Acid (GABA)InhibitoryWhen GABA receptors are activated, chloride enters the cell causing inhibitionAntianxiety meds cause CNS depression by prolonging the time the chloride channels are open

Neuroplasticity, The Kindling Effect, and Behavioral Sensitization

NeuroplasticityRefers to the ability of the brain and nervous system to change structure and functioningKindling/Behavioral SensitizationLess stimulus in needed to evoke a response

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