6.6 Hormones & Reproduction

Endocrine system Produces and releases hormones Hormones travel in the blood to target tissues Long distance communication between cells Endocrine Glands Blood stream Hormone Target Tissue

Homeostasis Ability of the body to maintain stable internal conditions regardless of external conditions Hypothalamus monitors the following: Blood pH Carbon dioxide concentration Blood glucose concentration Body temperature Water balance

Negative Feedback Loop When a change in the body is detected, the body elicits are response to being the altered level back to where it was before the change.

Thermoregulation Maintaining body temperature at 98.6 degrees Regulated by hypothalamus and thyroid

Thermoregulation chart Cooling Mechanisms Warming Mechanisms Sweat glands release sweat for evaporative cooling Sweat glands do not release sweat in order to limit evaporative cooling Arterioles leading to the skin’s surface dilate and bring more blood to the surface for cooling Arterioles leading to the skin’s surface constrict and keep blood in the body’s core tow warm vital organs The body spreads out (wide arms and legs) to increase the surface are for cooling The body pulls inwards (arms and legs very close to the body) to decrease surface area and retain heat Muscle cells relax and prevent shivering that would further heat the body Muscle cells contract to induce shivering to produce heat to warm the body

Blood glucose levels Must be maintained within a narrow range Regulated by the hypothalamus Regulated by two antagonistic hormones by produced by the pancreas (pancreatic islet cells) Alpha cells produce glucagon (increase glucose levels) Beta cells produce insulin (decrease glucose levels)

Blood Glucose Regulation Rise in Blood Glucose Levels Drop in Blood Glucose Levels Insulin is released from beta cells Glucagon is released from alpha cells Liver cells store glucose as glycogen, removing glucose from the bloodstream Liver cells break down stored glycogen into glucose and release the glucose into the bloodstream Cells take up glucose from the bloodstream (capillaries) Cells take up very little glucose from the bloodstream (capillaries) Blood sugar levels fall to homeostatic levels Blood glucose levels rise to homeostatic levels

Type I and Type II Diabetes Disease where you are unable to control glucose levels Type I Islet cells lose their ability to produce insulin Possible causes Autoimmune response, viral infection or genetics Type II Results when cellular receptors for insulin fail to respond to the hormone Causes Obesity or possibly genetics Can be reversed by diet and exercise

Type I and Type II Diabetes Type I Diabetes Type II Diabetes Onset Sudden Gradual Prevalence Less common More common Age of onset Mostly in young children Usually in adults but due to childhood obesity becoming more common in children Insulin levels No insulin production or very low levels Normal insulin or altered (higher or lower) levels Insulin needs Must have insulin injections for survival Vary with individual Treatment Insulin injections/diet changes Weight loss with diet and exercise may use insulin injections

Applications of Hormone Use Can be used to treat or detect disorders of the endocrine system

Hormone applications Hormone Source Mode of action Application Insulin Beta cells of the pancreas Lowers blood glucose levels Used to treat type I diabetes Thyroxin Thyroid gland Increases metabolic processes and thermoregulation Used as replacement therapy for patients with reduced thyroid function Leptin Adipose tissue Acts on the hypothalamus inhibiting appetite Used to help diagnose causes of obesity by testing levels of leptin in obese individuals Melatonin Pineal gland Circadian rhythms (sleep cycles) Used to treat jet lag