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Chapter 4

Week 4 (Textbook) - Sept 19-24 - Chapter 4 - PSYCH 3M03

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McMaster University
Aadil Merali Juma

LECTURE 4 PSYCH 3M03 Chapter 4: General Physiological Perspective Textbook Notes September 19-24, 2013 Overall Structure and Evolution Structure of the Human Nervous System  Two general division o Central Nervous System (CNS) – brain and spinal cord o Peripheral Nervous System (PNS) – nerves throughout body outside of CNS  Ganglia – clusters of nerve cells outside of CNS  Peripheral nerves  Point of connection o Spinal Cord – most o Brain Stem (at base of brain, top of spinal cord) – cranial nerves; 12 pairs of nerves  Afferent Nerves – bring sensory information to CNS  Efferent Nerves – conduct information from CNS to muscles  Hindbrain (part of brainstem) – reflexive behaviour o Medulla Oblongata  Contains nuclei that regulate vital functions (heartbeat, respiration) o Pons  Contains nuclei related to cranial nerves, simple sensory processing and general activation of the individual o Cerebellum (connected to the pons)  Non-conscious integration of sensory and motor information – allows for complex coordination  Midbrain (part of brainstem above hindbrain) o Tectum  Involved in auditory and visual information o Tegmentum  Contains nuclei controlling eye movements  Forebrain – very involved in motivation and emotion o Thalamus  Majority of neural input that goes to higher areas of the cerebral cortex is received via projections from specific regions of the thalamus  Sensory information is received by nuclei and is relayed it to the cortex  Nuclei project to motor and other non-sensory regions of the cortex o Hypothalamus o Pituitary Gland o Basal Ganglia  Caudate Nucleus – primarily concerned with motor control  Putamen – primarily concerned with motor control o Limbic System – involved in many aspects of motivation and emotion  Hippocampus  Amygdala  Septum  Anterior thalamus  Mammillary body  Hypothalamus  Parts of the cortex o Cerebral Cortex  Left and right; connected by the corpus collosum (band of fibres) Evolution Reflected in Structure  Use of chemicals, as opposed to nerves, is more primitive for internal communication o Hormones conduct information to cellular targets through blood circulation; controls growth, reproduction, response to stress etc o Nervous systems conduction information through electrical impulses; more rapid responses; interact closely with hormonal processes and chemical messengers  Earliest vertebrates (eg/ primitive fish) – simple NS; peripheral nerves from organs and skin to small CNS; CNS mainly brain stem with slight enlargement at anterior end 1 LECTURE 4 PSYCH 3M03  Hindbrain – reflexive behaviour  Forebrain – processes sensory information and allows for behavioural adaptation  Fish amphibians, reptiles – enriched sensory input; especially visual and auditory  Primitive mammals (eg/ rodents) – prominent olfactory bulbs  Neocortex (new structures) lateral to paleocortex (old conserved structures) o Neocortex allows for higher-order processing of information – permits coordination of sensory input, stored information and motor responses Cells of the Nervous System  CNS – two major classes of cells o Neurons – nerve cells that conduct information via electrical impulses o Glial Cells – provide structure, control nutrition, remove waste  Structure – surround neurons; hold them in place  Nutrition – transport substances from capillaries for nourishment of neurons  Waste – export waste from neurons to venous outflow; destroy carcasses of dead neurons  Separate neurons to avoid mingled electrical messages  PNS – three types of cells o Satellite Cells – structural and metabolic functions (similar to glial cells) o Schwann Cells – produce myelin that coats axons of many nerves and speeds the rate of information transmission; guide growth, death and recovery from injury of peripheral nerves o Neurons – directly transmit information  Four structures  Soma/Cell Body – contains nucleus  Dendrites – branches from soma  Axon – carries electrical information away from soma toward other neurons  Terminal button – terminate axons; release chemical substances that communicate with other neurons  Information Transmission – electrical impulse from dendrite, along axon, to terminal button 2 LECTURE 4 PSYCH 3M03  Action Potential – carries electrical message down axon when rapid reversal of electrical potential of membrane occurs due to changes in membrane permeability to Na+ and K+ o Electrical potential – formed by positive and negative ions on ether side of permeable cell membrane  AP carries messages to terminal button of axon (few milliseconds); presynaptic neuron releases chemicals at synapse, which alters electrical firing (AP) in postsynaptic neuron o Synapse – junction of terminal button of presynaptic neuron with somatic or dendritic membrane of postsynaptic neuron Structures Most Relevant to Motivation and Emotion Autonomic Nervous System  Part of the PNS that innervates major organs and some glands  Active in most emotions; subjective emotional sensations  Involuntary, not controlled by conscious processes  Regulate vegetative processes controlling smooth muscle, cardiac muscle and glands o Smooth muscle – found in skin associated with hair follicles, blood vessels, eye (controls pupil size and accommodation of the lens), wall of sphincters and gut, gall bladder, urinary bladder  3 Major Divisions o Enteric - gastrointestinal o Sympathetic – fight/flight  Rapidly activated during arousal, stress and many emotions  Promotes catabolic processes (processes expending energy from stored reserves)  It causes  Increase of blood flow to skeletal muscles  Reduction of blood flow to digestive organs  Secretion of epinephrine from adrenal glands  Cell bodies of sympathetic neurons located in thoracic and lumbar regions of the spinal cord  Fibers exit spinal cords and pass into spinal sympathetic ganglia, which connect to ganglia above and below to form the sympathetic chain  Sympathetic Chain – column of nervous tissue parallel to the spinal cord; all motor fibers enter sympathetic chain ganglia  Motor fiber synapses (from sympathetic chain ganglia)  At chain ganglia – travel to organs such as heart, bronchi, large blood vessels, sites in head and skin, sweat glands, hair follicles via spinal nerves  Travel to other sympathetic ganglia among the internal organs and synapse on postganglionic neurons – travel to organs such as intestines, stomach and kidneys  Neurotransmission  At ganglionic sympathetic synapses – involves acetylcholine 3 LECTURE 4 PSYCH 3M03  At terminals at target organs – involves norepinephrine  Firing stimulates a number of reflexes experiences during excitement (increased heart rate, increased respiration rate, perspiration, pupil dilation, piloerection) o Parasympathetic – rest/digest  Associated with restorative functions and recovery from acute excitement; reverses functions set off by parasympathetic portion  Supports anabolic functions (those which increase the body’s storative energy)  Branches from cranial and sacral areas of spinal cord, in head or neck an at the base of spine  Vagus nerve (a cranial nerve) serves autonomic functions in the thoracic and abdominal cavities  Parasympathetic ganglia located in immediate vicinity of target organ; short postganglionic fibers  Neurotransmission  At ganglionic synapses and terminals – involve acetylcholine Reticular Activating System  Reticular formation – brainstem structure; consists of nuclei, diffuse network of neurons with complex connections o Occupies central core of brainstem o Receives sensory information from various pathways o Plays a role in arousal from sleep and wakefulness; possibly selective attention Peripheral Endocrine Systems  Hormones – chemicals distributed by the bloodstream 1. Steroid Hormones  Light weight; basic 17-carbon structure with chemical appendages  Normally produced from dietary cholesterol  Readily pass to all parts of the body (including brain and fetus during pregnancy)  Fat soluble  Long term action  Excreted by liver and kidney actions  Enter cells and bind with specific receptors 2. Protein Hormones  Peptides – sequences of amino acids linked by peptide bonds  Monoamines – single amino acids  Water soluble  More rapid in action and excretion than steroid hormones  Do not pass into brain due to blood-brain-barrier (BBB)  BBB = collection of factors controlling membrane permeability and enzymatic actions that prevent or facilitate the specific chemical transport  Act on receptors on the cell membrane  Adrenal Glands – two, located above each kidney 4 LECTURE 4 PSYCH 3M03 o Vital functions related to carbohydrate, fat, protein and mineral metabolism; major roles in emotional sensations (i.e. fear, anger, elation) and motivational dimensions (i.e. stress, reproduction, aggression) 1. Adrenal Medulla – inner core; overgrown ganglion of sympathetic portion of autonomic NS  Secretes catecholamine’s (monoamine) – epinephrine and norepinephrine – directly into blood stream  Catecholamine’s – produced in synapses as transmitter substances of the CNS and sympathetic NS; release is rapid and occurs in conjunction with sympathetic NS firing  Adrenal catecholamine’s reach targets outside the brain where they enhance reflexes of the sympathetic NS  i.e. increased heart rate, respiratory rate, perspiration, fight/flight – may be associated with nervousness and fear, anger or exhilaration 2. Adrenal Cortex – outer capsule; steroid-secreting organ; many metabolic influences  Affects processes taking place over hours, weeks and months  No nervous input or innervation (unlike adrenal medulla) – controlled by peptides from pituitary  Secretes stero
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