Hockenbury Discovering Psychology 5th txtbk

A Guided Tour of the Brain61gland, and the adrenal medulla, which is the inner gland. Both the adrenal cortexand the adrenal medulla produce hormones that are involved in the humanstress response. As you’ll see in Chapter 12, on stress, hormones secretedby the adrenal cortex also interact with the immune system, the body’sdefense against invading viruses or bacteria.The adrenal medulla plays a key role in the fight-or-flight response,described earlier. When aroused, the sympathetic nervous system stimulatesthe adrenal medulla. In turn, the adrenal medulla produces epinephrineand norepinephrine. (You may be more familiar with theword adrenaline, which is another name for epinephrine.)As they circulate through the bloodstream to the heart andNerve impulsesother target organs, epinephrine and norepinephrine complementand enhance the effects of the sympathetic nervous sys-to hypothalamustem. These hormones also act as neurotransmitters, stimulatingactivity at the synapses in the sympathetic nervous system. The actionof epinephrine and norepinephrine is a good illustration of the longlastingeffects of hormones. If you’ve noticed that it takes a while foryou to calm down after a particularly upsetting or stressful experience,it’s because of the lingering effects of epinephrine and norepinephrine inyour body.Also important are the gonads, or sex organs—the ovaries in women and thetestes in men. In women, the ovaries secrete the hormones estrogen and progesterone.In men, the testes secrete male sex hormones called androgens, the mostimportant of which is testosterone. Testosterone is also secreted by the adrenalglands in both males and females. In both males and females, the sex hormones influencesexual development, sexual behavior, and reproduction.A Guided Tour of the BrainKey Theme• The brain is a highly complex, integrated, and dynamic system of interconnectedneurons.Key Questions• What are neural pathways and why are they important?• What are functional and structural plasticity?• What is neurogenesis, and what is the evidence for its occurrence in theadult human brain?HypothalamusRelease ofoxytocinPituitaryglandFigure 2.12 Interacting Systems Breastfeedingis an example of the complex interactionamong the nervous system, theendocrine system, and behavior. Nerve impulsesfrom sensory receptors in themother’s skin are sent to the brain. Thehypothalamus signals the production ofoxytocin by the pituitary gland, whichcauses the mother’s milk to let down andbegin flowing.Think about it: the most complex mass of matter in the universe sits right behindyour eyes and between your two ears—your brain. Not even the Internet can matchthe human brain for speed and sophistication of information transmission.In this part of the chapter, we’ll take you on a guided tour of the human brain.As your tour guides, our goal here is not to tell you everything that is known or suspectedabout the human brain. Such an endeavor would take stacks of books ratherthan a single chapter in a college textbook. Instead, our first goal is to familiarizeyou with the basic organization and structures of the brain. Our second goal is togive you a general sense of how the brain works. In later chapters, we’ll add to yourknowledge of the brain as we discuss the brain’s involvement in specific psychologicalprocesses.At the beginning of this tour, it’s important to note that the brain generally doesnot lend itself to simple explanations. One early simplistic approach to mapping theadrenal medullaThe inner portion of the adrenal glands;secretes epinephrine and norepinephrine.gonadsThe endocrine glands that secrete hormonesthat regulate sexual characteristics and reproductiveprocesses; ovaries in females andtestes in males.