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NEUROENDOCRINE SYSTEM. AIMS OF LESSON To understand the relationship between the nervous and endocrine systems To have an appreciation of how hormones exert their effect to regulate metabolism and maintain homeostasis. NEUROENDOCRINE SYSTEM.
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NEUROENDOCRINE SYSTEM AIMS OF LESSON • To understand the relationship between the nervous and endocrine systems • To have an appreciation of how hormones exert their effect to regulate metabolism and maintain homeostasis
NEUROENDOCRINE SYSTEM • Functions with nervous system to co-ordinate body systems and maintain homeostasis • Both sense information, organise a response, then deliver a message • Nerves release neurotransmitters to transmit messages via neurons • Endocrine system releases hormones (chemical messengers) into the blood • Neurotransmitters and hormones bind to receptors either “on” or “in” their target cells
ENDOCRINE SYSTEM • A collection of glands that secrete chemical messengers called “hormones” (Greek – to excite) • Hormones travel via the blood to their target cell • The target cell has specific protein receptors for that hormone
Hormones only exert their influence on cells that have specific receptors If a cell does not have a receptor for a particular hormone then the hormone has no effect on that cell ENDOCRINE SYSTEM
COMPARISON BETWEEN NERVOUS AND ENDOCRINE SYSTEMS CHARACTERISTIC NERVOUS ENDOCRINE Molecule Neurotransmitters Hormones delivered released locally to cells throughout the body Site of action Close to site of Far from site of release release (via blood) Types of target cells Skeletal, cardiac All body cells muscle, glands neurons Time to onset of action Milliseconds Seconds, hours, days Duration of action Generally shorter Generally longer
COMMUNICATION BETWEEN THE NERVOUS AND ENDOCRINE SYSTEMS • Linked by the HYPOTHALAMUS in the forebrain and the PITUITARY gland just below it • Hypothalamus sends chemical messages to the pituitary causing it to release pituitary hormones into the blood • The pituitary hormones act on other endocrine glands to secrete their hormones • Because the pituitary gland controls the secretion of other endocrine glands it is known as the “master” gland
EXAMPLE OF HORMONAL INFLUENCE • Pancreas secretes 2 hormones: • 1. INSULIN – released in response to high plasma levels of glucose • 2. GLUCAGON – released in response to low plasma levels of glucose • These two hormones are antagonistic working in opposition to closely monitor plasma glucose levels
INTEGRATED CONTROL OF HORMONE SECRETION • Endocrine glands are under the influence of more than one input either reinforcing or inhibiting the hormones effect • EG. Insulin responds to changes in plasma glucose and amino acids as well as sympathetic and parasympathetic nervous activity • Elevation of plasma glucose and amino acids increase insulin secretion • Release of adrenaline and noreadrenaline decreases insulin secretion
IN SUMMARY • Nearly every process in the human body is kept in balance by the finely tuned interaction of the nervous and endocrine system • Both are responsible for communication, integration and control • Hormones are often antagonistic signalling a cell to ”increase” or “decrease” a certain cellular process