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Homeostasis 3.4 Internal Homeostasis Animals have internal control mechanisms that act to maintain a stable internal environment = homeostasis. Homeostasis Animals have internal control mechanisms that act to maintain a stable internal environment = homeostasis. ‘The ability of an animal to maintain a constant internal environment in response to environmental change internally and externally’ Feedback control The body has complex feedback control systems (homeostatic mechanisms) to maintain homeostasis. Feedback control The body has complex feedback control systems (homeostatic mechanisms) to maintain homeostasis. They depend on different body systems or organs working together to determine when the control system needs to be switched on/off. These require the following components: Feedback control The body has complex feedback control systems (homeostatic mechanisms) to maintain homeostasis. They depend on different body systems or organs working together to determine when the control system needs to be switched on/off. These require the following components: - Input (or stimulus) from internal/external environment - Receptors or sensors – sensory nerves/organs Feedback control The body has complex feedback control systems (homeostatic mechanisms) to maintain homeostasis. They depend on different body systems or organs working together to determine when the control system needs to be switched on/off. These require the following components: - Input (or stimulus) from internal/external environment - Receptors or sensors – sensory nerves/organs - Controller – usually the brain - Effectors – glands, muscles or organs Feedback control The body has complex feedback control systems (homeostatic mechanisms) to maintain homeostasis. They depend on different body systems or organs working together to determine when the control system needs to be switched on/off. These require the following components: - Input (or stimulus) from internal/external environment - Receptors or sensors – sensory nerves/organs - Controller – usually the brain - Effectors – glands, muscles or organs - Output – the response or action of the effector. Feedback control The controller has a set point – the internal environment is measured against this. Feedback control The controller has a set point – the internal environment is measured against this. When the environment is away from this set point, receptors record it and send info to the controller. Feedback control The controller has a set point – the internal environment is measured against this. When the environment is away from this set point, receptors record it and send info to the controller. Controller sends messages to effectors, instructing them to restore conditions to the set point. Feedback control The controller has a set point – the internal environment is measured against this. When the environment is away from this set point, receptors record it and send info to the controller. Controller sends messages to effectors, instructing them to restore conditions to the set point. Feedback mechanisms can be positive or negative – neg most common. **Glue in your examples** Systems involved in homeostatic control Nervous system Central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS) Systems involved in homeostatic control Nervous system Central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS) CNS – brain and spinal cord. Brain acts as controller receiving input from sensory nerves, processes the input then sends output via motor nerves to the effectors. Systems involved in homeostatic control Nervous system Central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS) CNS – brain and spinal cord. Brain acts as controller receiving input from sensory nerves, processes the input then sends output via motor nerves to the effectors. The most important control is the hypothalamus. Systems involved in homeostatic control Nervous system Central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS) CNS – brain and spinal cord. Brain acts as controller receiving input from sensory nerves, processes the input then sends output via motor nerves to the effectors. The most important control is the hypothalamus. PNS – receives and responds to stimuli through nerves of the skin, organs, skeletal muscles. Systems involved in homeostatic control Nervous system Central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS) CNS – brain and spinal cord. Brain acts as controller receiving input from sensory nerves, processes the input then sends output via motor nerves to the effectors. The most important control is the hypothalamus. PNS – receives and responds to stimuli through nerves of the skin, organs, skeletal muscles. ANS – regulates the actions of glands (eg. Endocrine, sweat, salivary), smooth muscles (eg. pupil contractions, digestion), heartbeat, respiratory rate ANS Also controls hunger, thirst, desire to go to the toilet. ANS Also controls hunger, thirst, desire to go to the toilet. Sympathetic system of the ANS – tends to speed functions up ANS Also controls hunger, thirst, desire to go to the toilet. Sympathetic system of the ANS – tends to speed functions up Parasympathetic – slows things down ANS Also controls hunger, thirst, desire to go to the toilet. Sympathetic system of the ANS – tends to speed functions up Parasympathetic – slows things down EG – speeding up and slowing down of heartbeat Endocrine system A series of ductless glands (endocrine glands) located throughout the body. Endocrine system A series of ductless glands (endocrine glands) located throughout the body. Endocrine glands secrete chemicals called hormones directly into the blood for transport to target tissue (organs/glands/cells). Endocrine system A series of ductless glands (endocrine glands) located throughout the body. Endocrine glands secrete chemicals called hormones directly into the blood for transport to target tissue (organs/glands/cells). Each endocrine gland secretes its own specific hormone – each hormone has a specific target. Endocrine system A series of ductless glands (endocrine glands) located throughout the body. Endocrine glands secrete chemicals called hormones directly into the blood for transport to target tissue (organs/glands/cells). Each endocrine gland secretes its own specific hormone – each hormone has a specific target. Eg – pancreatic gland secretes the hormone insulin which targets liver cells to convert glucose from the blood to glycogen for storage. **Glue in other examples and read them** The pituitary gland Not only produces its own hormone, but also hormones that control the activity of other endocrine glands – FSH (controls oestrogen and progesterone in ovaries) and TSH ( controls production of thyroxine by thyroid). The pituitary gland Not only produces its own hormone, but also hormones that control the activity of other endocrine glands – FSH (controls oestrogen and progesterone in ovaries) and TSH ( controls production of thyroxine by thyroid). About the size of a pea and is located directly under the brain. Closely connected with the hypothalamus – H has receptors for monitoring the level of substances in the blood and is the control centre. Blood system Transport system of the body – links all other systems depending on supply and demand: Blood system Transport system of the body – links all other systems depending on supply and demand: - CO2 produced in the cells of working muscle tissue is transported to alveoli cells of the lungs for excretion - Excess glucose entering the blood from cells lining the small intestine as a result of starch digestion is transported to the liver for conversion to glycogen and stored. Vasoconstriction & vasodilation Vasoconstriction: - Results from increased contraction of circular smooth muscle in wall of arteriole. Resistance to blood flow increases = less blood flow. Vasoconstriction & vasodilation Vasoconstriction: - Results from increased contraction of circular smooth muscle in wall of arteriole. Resistance to blood flow increases = less blood flow. - Increases blood pressure Vasoconstriction & vasodilation Vasoconstriction: - Results from increased contraction of circular smooth muscle in wall of arteriole. Resistance to blood flow increases = less blood flow. - Increases blood pressure Vasodilation: - Results from decreased contraction of smooth muscle in wall of arteriole. Resistance to blood flow decreases = increased blood flow. - Decreases blood pressure. Liver & Kidneys Liver: - Largest internal organ and maintains homeostasis through detoxification, storage of minerals (Fe, Cu, K) and production of heat energy. Liver & Kidneys Liver: - Largest internal organ and maintains homeostasis through detoxification, storage of minerals (Fe, Cu, K) and production of heat energy. - Essential in the control of blood glucose levels. Kidneys: - Liver & Kidneys Liver: - Largest internal organ and maintains homeostasis through detoxification, storage of minerals (Fe, Cu, K) and production of heat energy. - Essential in the control of blood glucose levels. Kidneys: - Main excretory organs – removing excess water and mineral ions and urea. Liver & Kidneys Liver: - Largest internal organ and maintains homeostasis through detoxification, storage of minerals (Fe, Cu, K) and production of heat energy. - Essential in the control of blood glucose levels. Kidneys: - Main excretory organs – removing excess water and mineral ions and urea. - Essential for maintaining levels of glucose and water in the body and contribute to the regulation of blood pressure.
