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The Biological Perspective. Development of the Biological Perspective. Develops in response to the Dualism attributed to Descartes circa 17 th century Dualism-mind and body distinct, can interact via pineal gland in brain.
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Development of the Biological Perspective • Develops in response to the Dualism attributed to Descartes circa 17th century • Dualism-mind and body distinct, can interact via pineal gland in brain. • Biological perspective moves away from this towards monism and materialism • Monism-mind and body a single entity • Materialism-all behavior has a physiological basis
Shift begins away from dualism with Julien de La Mettrie, French Priest turned physician • Contracts fever and notes physical condition affected both mental and physical state • Writes L’histoirenaturelle de l’ame (The Natural History of the Soul) • Argues mind and soul are the same and the mind is part of the body. • Forced from France for his views
A physician named Cabanis connected consciousness to the brain during the French Revolution • Argued guillotine victims were not conscious because this was a function of the brain. • Paul Broca was the first to connect physiological structures and behavior in 1861. • Meets man who lost ability to speak coherently after head injury at insane asylum at Bicetre. • Post-mortem autopsy reveals injury to specific area of brain • Proves localization of function, final step in progression of ideas • Localization of function-connects a specific behavior to a specific brain area
The role of heredity in behavior was another major aspect of the perspective • Heredity-the biological transmission of characteristics from one generation to another • Original beliefs centered around creationist ideas in the Bible • Questions began to arise with catalogue of biologist Linnaeus in 1735 • Orderly categories suggested connections among species • French naturalist Lamarck produced first theory of evolution in 1809 • Variations develop through inheritance of acquired characteristics • Important even though discredited because it suggested hereditary basis for characteristics • Charles Darwin’s Origin of the Species in 1859 was the absolute game changer • Variations occur by chance, but can be passed on • “Survival of the fittest” principle stated that variations which help individuals survive to reproduce will be passed on • Leads to natural selection of the best characteristics from a survival standpoint • Natural selection-the evolutionary process by which those random variations within a species which enhance reproductive success will lead to perpetuation of new characteristics, • Mechanism for this was not explained until the work of Gregor Mendel was rediscovered • Darwin suffered a fate similar to La Mettrie in conflict with religious ideologies • Still not formally resolved.
Nature of the Physiological System • What is the mechanism of mind and body interactions? • Several physiological systems involved • Central Nervous System • Peripheral Nervous System • Endocrine System • Important to note that “mind” or seat of consciousness may consist of all or several of these systems and not just the brain
The Nervous System • Coordinates the activities of the many body systems • Composed of specialized cells called neurons • Act as wires carrying an electro-chemical message • Connect to each other at junctions called synapses • A synapse acts as the switch board sending the message to other areas
The Nervous System • Central Nervous System • Consists of the brain and the nerve pathways of the spinal cord • Use interneurons to carry messages from peripheral to brain and back • Brain integrates info and directs muscle activity • Spinal cord acts as relay station (passes through vertebrate for protection) • Cannot be repaired • Peripheral Nervous System • All nerve pathways outside of central nervous system • Carry outside messaged to CNS through sensory neurons • Initiate muscle direction using motor neurons which receive info from CNS • Can be repaired
Nervous System • Central Nervous System • Brain • Spinal Cord • Peripheral Nervous System • Autonomic • Sympathetic • Parasympathetic • Somatic
Further Information • Simple Breakdown of the Nervous System
Neurons • Basic units of the nervous system • Act like a wire passing an electric signal called a nerve impulse • Key components of neurons • Dendrites- small branches that receive and transmit info between neurons • Axon-cable like structure on which messages travel through neurons • Myelin- insulating sheath around the axon, made of tightly wrapped Schwann cells, improve efficiency of conduction • Node of Ranvier-small gaps in the myelin sheath of an axon • Axon Terminals- branch like structures that extend from the end of the axon pathway • Synapse- small gaps between dendrites and the axon of the next neuron • Neurotransmitters- chemicals released to bridge gaps at the synapse
The Brain • Consists of about 100 billion neurons (Estimate via extrapolation) • Each neuron makes and receives connections with 100’s maybe 1000’s of other neurons • Creates network of 1 million-billion connections in the cortex (Pink, wrinkled outer layer of brain which controls many higher functions)
Divisions of the Brain • Cortex • Split into two hemispheres (left and right) which control opposite sides of the body • Hemispheres broken into lobes by 2 major fissures • Central-Splits brain in half roughly, front and back • Lateral-Runs along the side of each hemisphere • There are 4 lobes with seeming localized function • Frontal-interpretation of emotion and experience/integrates activity from other brain areas/controls voluntary movement of the muscles • Temporal-hearing, language and memory for objects • Parietal-related to touch senses • Occipital-devoted solely to vision • Despite localization of functions in the brain it always functions as a whole
The Primitive Brain • Located beneath the cortex and linked by subcortical networks • Control fundamental aspects of behavior • Consists of • Limbic system • Hypothalamus-regulates behavior associated with basic drives and regulates hormonal functions • Hippocampus-important to memory function • Amygdala-plays a role in basic emotions • Cerebellum • Contains 2 hemispheres • Directs movement and balance, particularly fine motor control activities • Brain Stem • Medulla-regulates basic bodily processes • Pons- provides connections between the cortex and the cerebellum • Reticular formation-controls sensory inputs
Chemical Processes in Behavior • Required for communication to work between neurons • Exchange of chemicals called neurotransmitters bridges gaps at synapses • Approximately 100 chemicals used in this process • Some used to excite (Trigger activation) others used to inhibit (Prevent neuron firing) still more are used to block or clear away these exciters and inhibitors • If neurons are constantly stimulated they reduce their response, called habituation • Reason why we need hormones
Endocrine System • Secretes chemical called hormones into the bloodstream to regulate bodily processes that require slower long term functions • Originally thought to be complementary to Nervous System • Now thought to instead be linked via pituitary gland and hypothalamus • Chemical thought once to be hormones have now been found to also be neurotransmitters and vice versa (i.e. norepinepherine, vasopressin) • Major difference between hormones and neurotranmitters • Neurotransmitters used to send signals along neural pathways, relatively quick process • Hormones send signals to internal organs and other areas in a more controlled and slower fashion via the blood stream
Basic Mechanisms of Heredity • Genes- basic units of heredity made up of stings of amino acids • Humans possess about 80,000 different genes • Each regulates a different process • Genes split and recombine using genetic information from both parents to produce offspring • Chromosomes are the mechanism for this • Chromosomes-thread-like genetic structures composed of double strands of DNA and proteins • Humans contain 23 pairs of chromosomes
Genotype- genetic code and individual carries in their DNA • Phenotype- the observed characteristics of the individual • Remember that genes function in pairs and various forms of genes (alleles) for a characteristic exist • Mutations- change the genetic material of a cell possibly creating a new trait that can be passes on to descendants • Argument for evolution
