There are two basic types of regulatory systems Endocrine system Nervous system Regulatory systems These two system are structurally, chemically and functionally related. Many nervous systems have neurosecretory cells that secrete hormones which act on some region of the organism. Several chemicals serve both as hormones and as signals in the nervous system. There are also several regulatory processes that overlap between the endocrine and the nervous systems. Also feed back mechanisms, both positive and negative, operate in both the endocrine and the nervous system

Figure 45.1 An example of how feedback regulation maintains homeostasis

Figure 45.2 Hormonal regulation of insect development Neurosecretory cells in brain produce brain hormone (BH) BH signals its main target, the prothoracic gland, to produce ecdysone Ecdysone secretion is episodic with each release stimulating the molt Juvenile hormone (JH) is secreted by the corpus allatum and determines the results of the molt. High concentration results in a larvae produced by the molt and low levels stimulate metamorphosis high Low

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Chemical Signals and Their Modes of Action 1.A variety of local regulators affect neighboring target cells 2.Most chemical signals bind to plasma-membrane proteins, initiating signal transduction pathways 3.Steroid hormones, thyroid hormones, and some local regulators enter target cells and bind to intracellular receptors

Growth factors: proteins and polypeptides that stimulate cell proliferation Example: nerve growth factor (NGF) affects certain embryonic cells, developing white blood cells, and other kinds of cells Nitric oxide (NO) –Though a gas, NO is an important local regulator. –When secreted by neurons, it acts as a neurotransmitter. –When secreted by white blood cells, it kills bacteria and cancer cells. –And when secreted by endothelial cells, it dilates the walls of blood vessels. Prostaglandins (PGs): modified fatty acids. –PGs secreted by the placenta stimulate uterine contractions during childbirth. –Other PGs play a role in inflammation and the blood flow to the lungs. A variety of local regulators affect neighboring target cells Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Most chemical signals bind to plasma membrane proteins, initiating signal-transduction pathways. Fig. 45.3a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Different signal-transduction pathways in different cells can lead to different responses to the same signal. In this case it is the neurotransmitter, acetylcholine Fig. 45.4

Steroid hormones, thyroid hormones, and some local regulators enter target cells and bind to intracellular receptors Examples: estrogen, progesterone, vitamin D, NO. –Usually, the intracellular receptor activated by a hormone is a transcription factor. (shown in b below) Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 45.3b

Humans have nine endocrine glands.

The hypothalamus integrates endocrine and nervous function. –Neurosecretory cells of the hypothalamus produce hormones. Releasing hormones stimulate the anterior pituitary (adenohypophysis) to secrete hormones. Inhibiting hormones prevent the anterior pituitary from secreting hormones. The hypothalamus and pituitary integrate many functions of the vertebrate endocrine system Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 45.6b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings The anterior pituitary gland is derived from a fold of tissue on the roof of the embryonic mouth. Neurosecretory cells of the hypothalamus exert control over the anterior pituitary gland Source of releasing and inhibiting hormones

 The posterior pituitary (neurohypo- physis) is derived from brain tissue and stores and secretes hormones produced by the hypothalamus. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 45.6a

Regulation of blood osmolarity is maintained by hormonal control of the kidney by negative feedback circuits. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings One hormone important in regulating water balance is antidiuretic hormone (ADH). ADH is produced in hypothalamus of the brain and stored in and released from the pituitary gland, which lies just below the hypothalamus. Osmoreceptor cells in the hypothalamus monitor the osmolarity of the blood. When blood osmolarity rises above a set point of 300 mosm/L, more ADH is released into the blood stream and reaches the kidney. The epithelium of the distal tubules and collecting ducts become more permeable to water. This amplifies water reabsorption, reduces urine volume and helps prevent further increase of blood osmolarity above the set point.

The next two slides are given for added discussion but will not be examined in examinations in this course.

The pancreas has both endocrine and exocrine functions. –Exocrine function: secretion of bicarbonate ions and digestive enzymes. –Endocrine function: insulin and glucagon secreted by islets of Langerhans. –Insulin: a protein secreted by beta cells. Lowers blood glucose levels. –Stimulates all body cells (except brain cells) to take up glucose. –Slows glycogenolysis. –Inhibits gluconeogenesis. Secretion regulated by glucose in blood (negative feedback). Endocrine tissues of the pancreas secrete insulin and glucagon, antagonistic hormones that regulate blood glucose Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings The adrenal medulla and adrenal cortex help the body manage stress The adrenal glands are located adjacent to the kidneys.The adrenal cortex is the outer portion and secretes corticosteroids and is regulated by the nervous system in response to stress..The adrenal medulla is the inner portion and produces epinephrine (adrenaline) and norepinephrine (noradrenaline) and also regulated by the nervous system.

Epinephrine (adrenaline) and norepinephrine (noradrenaline). Catecholamines: amines synthesized from tyrosine. Secretion regulated by the nervous system in response to stress. Raises blood glucose level and blood fatty acid level. Increase metabolic activities. –Increases heart rate and stroke volume and dilates bronchioles. Shunts blood away from skin, digestive organs, and kidneys, and increases blood flow to heart, brain, and skeletal muscle. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings