HMB200H1 Final: Lecture 8 Revison Guide

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Human Biology
Franco Taverna

Lecture 8 Revision Guide Amygdala & Hypothalamus - Activating Amygdala—can elicit multiple effects o Important effect: can trigger hypothalamus Hypothalamus: can trigger Innate Releasing Mechanisms (IRMs) - Activating hypothalamus  leads to goal-driven/motivated behaviours - Indistinguishable from normally occurring behaviours Motivation / Drive: - Drive provides force to act purposefully towards a goal o Adaptive, promotes survival - Activated by triggers o Internal triggers (hunger, curiosity) o External triggers (sights of food) Operant Conditioning: o Triggers can be learned—operant conditioning - Involves multiple physiological systems - Final trigger: hypothalamus  motor pathway Organizational Effects - Using consequences to influence behaviour - Reinforcements: increases the preceding behaviour - Punishments: decreases the preceding behaviour Operant & classical conditioning often work in tandem - Physical development of sexual characteristics - Sex hormones—critical for physical & sexual development Physical Development: Primary Sexual Characteristics 1. Genetics: a. SRY gene—leads to differentiated gonads a.i. Different gonads  different hormones produced 2. Hormones: Activational Effects a. Steroid hormones—Testosterone, Estrogens b. Affects gene activation  major structural effects Physical Development: Secondary Sexual Characteristics - Developmental processes pause after birth, until puberty 1) Hormones & genes - Sexually dimorphic behaviours o Differen ces in sexual behavio urs, b/w 2 sexes o Caused by drive & Summary of Sex Differences stimuli o Differen ces triggere d by Innate Enlarged Male mPOA Releasin g Mechan isms - Dimorphic brain development  different behaviours & triggers Females: - Sexual behaviour occurs usually in Estrus o Estrogen surge 2 days prior  Facilitates proceptive behaviours o Progeste  Activates receptive behaviour rone surge 6  Receptive behaviours facilitated by stimulation of mounting males hours after - Estrogen surge: Estrus onset o Promotes progesterone receptor expression in ventromedial hypothalamus  I o Allows male stimulation  progesterone surge  VMH activation n c  periaqueductal gray activation  Lordosis event (receptive r behaviour) e Males: a s - Testosterone—simply ‘permissive’ molecule e o Castration – lack of testosterone  mating stops s p o Reversed by testosterone treatment (1/10 of normal concentration) r - Female stimulation: o c o Exhibition of proceptive & receptive behaviours e o Smells—Pheromones  vomeronasal organ p t - Female stimulation  Medial amygdala  Medial preoptic area (mPOA) i v of hypothalamus o Triggers ventral midbrain  e b e  Basal ganglia  movement h a  Brainstem & spinal cord  copulation & ejaculatory reflexes v i o u - Ventromedial hypothalamus o Controls lordosis [female] r - mPOA hypothalamus o controls copulatory behaviour in males - larger bulbocavernosus muscle (BC) around base of penis Caused by: - testosterone surge around birth Causes: - sensory Behavioural effect of hormones in HUMANS integration of female sights & sounds, triggering male copulatory behaviour Smaller mPOA: - no triggering male copulatory behaviour (causes female- like behaivours) Larger BC muscle - more motoneurons innervated in the spinal nucleus of the BC muscles (SNB) - Androgens promote their survival o Females—lack the testosterone to bind w/ androgen receptors  death of the muscle Vomeronasal organ - Vomeronasal receptors detect “pheromones” involved in sexual
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