The adrenal medulla develops from neural tissue and secretes two hormones, epinephrine and norepinephrine. These two hormones are secreted in response to stimulation by sympathetic nerve, particularly during stressful situations. A lack of hormones from the adrenal medulla produces no significant effects.
While the sinoatrial node typically regulates the heartbeat during normal sinus rhythm, PACs occur when another region of the atria depolarizes before the sinoatrial node and thus triggers a premature heartbeat.
Giant Papillary Conjunctivitis Go to Academy Store Learn more and Purchase. Giant Papillary Conjunctivitis Giant papillary conjunctivitis (GPC) occurs in primary and secondary forms (Figure 9). All forms of GPC are at least partially caused by chronic ocular allergy. Primary forms of GPC include vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC). Secondary GPC is caused by contact lenses, ocular prostheses, or exposed sutures.