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Various factors can impact brain development: 1. Direct CNS injury or insult (e.g., stroke, tumor, trauma) 2. Environmental factors (e.g., malnutrition, sensory deprivation) 3. Environmental toxins (e.g., lead, radiation) 4. Psychosocial factors (e.g., quality of mother-child relationship, level of available stimulation, social support structures, access to resources etc.) How do these various factors actually influence neurons and their structure and function? Epigenetics Environmentally induced changes in gene expression. DNA is wrapped around other proteins (called histones) When the DNA is read it is said to be “expressed” difficult to read easier to read In order for all of our DNA to fit in our cells, it must be highly compacted. DNA is wrapped around a cluster of proteins called histones Champagne et al., (2009) Current Opinion in Neurobiology Gene expression requires unwrapping of DNA Champagne et al., (2009) Current Opinion in Neurobiology The Bidirectional Coupling of Levels Meeting the challenge of homeostasis involves: • • • • • central nervous system autonomic (peripheral) nervous system endocrine system immune system limbic system The Brain/ Body Links • Autonomic Nervous System: -Sympathetic system -Parasympathetic system autonomic nervous system Autonomic Nervous System HYPOTHALAMUS The Hypothalamus •The hypothalamus has 4 ways of using the autonomic nervous system to regulate internal behavior (such as respiration and heart rate): - diminish or increase activity of the sympathetic nervous system -diminish or increase activity of the parasympathetic nervous system The Hypothalamus •These adjustments are primarily accomplished by the type of neurotransmitters released at target organs or glands: - acetylcholine (Ach) decrease activity -norepinephrine (NE) increase activity Homeostasis Several critical features involved in maintaining homeostasis: • set point (optimal level system tries to maintain) • detector (sensitive to deviations from the set point) • use of negative feedback (it opposes the action that started the activity in the first place) Hypothalamus • The hypothalamus bridges nervous and endocrine systems. • For example, heat-sensitive nerve cells in the hypothalamus receive “too cold” signals from heat sensors in the skin - the hypothalamus tells the pituitary gland to release a chemical that triggers the release of thyroid hormone into the bloodstream. • Thyroid hormone in turn steps up the body’s heat production by altering metabolic rate. Hypothalamus and Homeostasis • If the body’s water content falls, salt concentration builds up in the blood and special sensors warn the hypothalamus. • It sends a signal (releasing factor) to the pituitary gland to release vasopressin into the bloodstream. • This makes the kidneys reabsorb water otherwise scheduled to be released as urine. ENDOCRINE GLANDS Endocrine System Example: if blood pressure rises, sensors in the kidney detect the rise and set in motion the various processes that reduce blood pressure. Introduction to Biopsychology [PSB 4002] Professor Robert Lickliter DM 260 / 305-348-3441 [email protected] website: dpblab.fiu.edu Three generations at once are exposed to the same environmental conditions (diet, stress, toxins, etc.). ENDOCRINE GLANDS Endocrine Glands Produce Hormones • Hormones affect behavior in two primary ways: -1. Organizational effects: influence the developing structure of the organism in longlasting ways (examples include the effects of estrogen and testosterone on primary and secondary sexual characteristics). Brain reorganization induced by fetal androgens cannot be reversed. Organizational Effects of Hormones • Sex differences in brain structure: corpus callosum is relatively larger in females • the suprachiasmatic nucleus of the hypothalamus is relatively larger in males • hippocampus is relatively larger in males than females • the left hemisphere of the cerebral cortex is thicker than the right in females; in males, the right cortex is thicker than the left Hormones 2. Activational effects: prime the organism for responding to certain stimuli in real time. Are typically reversible and shortterm (examples of oxytocin and prolactin in the expression of maternal behavior in mammals). Perception/Action Coupling The Perceptual Systems The Perceptual Systems invariant sequence of sensory system onset in birds and mammals visual auditory chemical vestibular tactile Developmental Time Types of Animal Infants • precocial: born with all sensory systems functional • (lambs, calves, foals, ducks, chicks) Types of Animal Infants • altricial: born with one or more sensory systems not yet functional (kittens, puppies, rat pups, mice, songbirds) Which are we?