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NROC61 - Ch16 textbook notes

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Le Boutillier

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Chapter 16 Motivation y Voluntary movements are incited to occur motivate in order to satisfy a need y Motivation can be very abstract eg the need to go sailing on a warm and breezy summer or very concrete eg going to the bathroom because your bladder is full y Motivation can be thought of as a driving force on behaviourThe Hypothalamus Homeostasis and Motivated Behaviour y Homeostasis is the processes that maintain the internal environment of the body within a narrow physiological range y The hypothalamus plays a key role in the regulation of body temperature fluid balance and energy balance y Hypothalamic regulation of homeostasis starts with sensory transduction y A regulated parameter is measured by specialized sensory neurons and deviations from the optimal range are detected by neurons in the periventricular zone of the hypothalamus y The response generally has three components o Humoral response Hypothalamic neurons respond to sensory signals by stimulating or inhibiting the release of pituitary hormones into the bloodstream o Visceromotor responseNeurons in the hypothalamus respond to sensory signals by adjusting the balance of sympathetic and parasympathetic outputs of the ANS o Somatic motor response Hypothalamic neurons within lateral hypothalamus respond to sensory signals by inciting an appropriate somatic motor behavioural response EXAMPLE o You are cold dehydrate and depleted of energy The appropriate humoral and visceromotor responses kick in automatically You shiver blood is shunted away from the body surface urine production is inhibited and body fat reserves are mobilized o However the fastest and most effective way to correct these disturbances of brain homeostasis is to actively seek or generate warmth by moving to drink water and to eat These are examples of motivated behaviours generated by the somatic motor system The LongTerm Regulation of Feeding Behavioury One primary reason we are motivated to eat is to keep these reserves at a level sufficient to ensure that there will not be an energy shortfall y Energy Balance o The bodys energy stores are replenished during and immediately after consuming a mealThis condition ie blood filled with nutrients is the prandial stateHere energy is stored as glycogen and triglycerides y Glycogen reserves have a finite capacity and found mainly in the liver and skeletal muscle y Triglyceride reserves are found in adipose fat tissue have an unlimited capacity y Assembly of macromolecules is called anabolismDuring the fasting condition postabsorptive the stored glycogen and triglycerides are broken down to provide the body with a continuous supply of the molecules used as fuel for cellular metabolismglucose for all cells fatty acids and ketones for all cells other than neurons y Breaking down of macromolecules is catabolism o The system is in balance when energy reserves are replenished at the same rate they are spentIf intake is greater than usage the amount of fat adiposity increaseobesityIf intake is less than usage required loss of fat tissues occursstarvation y Hormonal and Hypothalamic Regulation of Body Fat and Feeding o Feeding is stimulated when neurons in the hypothalamus detect a drop in the level of a hormone released by fat cellsThese neurons are in the periventricular zone and those that incite feeding behaviour are in the lateral hypothalamus o Body Fat and Food ConsumptionThe idea that the brain monitors the amount of body fat and acts to defend this energy storeagainst perturbations proposed in 1953 by Gordon Kennedy is called the lipostatic hypothesis The connection between body fat and feeding behaviour suggest there must be communication from adipose tissue to the brain
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