1.2 Physiological control systems and feedback mechanisms

Physiological control systems and feedback mechanisms are crucial for maintaining balance in animals. These systems involve complex interactions between receptors, control centers, and effectors, working together to regulate bodily functions and respond to changes.

Negative feedback counteracts changes, while positive feedback amplifies them. Understanding these mechanisms is essential for grasping how animals maintain homeostasis and adapt to their environments. It's the foundation of animal physiology.

Feedback and Control Systems

Negative Feedback Mechanisms

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• Maintain homeostasis by counteracting changes in the internal environment
• Consist of a control center, receptors, and effectors that work together to restore balance
• Involve a series of steps: stimulus detection, signal transmission, response generation, and feedback to the control center
• Examples include regulation of blood glucose levels (insulin and glucagon) and body temperature (hypothalamus)

Positive Feedback Mechanisms and Feedforward Control

• Positive feedback amplifies changes in the body, leading to a deviation from homeostasis
• Examples include blood clotting cascade, uterine contractions during childbirth, and lactation
• Feedforward control anticipates changes in the internal environment and initiates compensatory mechanisms before the change occurs
• Feedforward control examples include increased heart rate and breathing rate in anticipation of exercise

Control Centers and Compensatory Mechanisms

• Control centers are specialized regions in the body that receive input from receptors and initiate appropriate responses
• Examples of control centers include the hypothalamus (regulates body temperature, hunger, and thirst) and the medulla oblongata (regulates heart rate and breathing)
• Compensatory mechanisms are physiological processes that help maintain homeostasis by counteracting disturbances
• Examples of compensatory mechanisms include sweating to cool the body during heat stress and shivering to generate heat during cold stress

Physiological Regulation

Endocrine System

• Consists of glands that secrete hormones directly into the bloodstream
• Hormones act as chemical messengers, targeting specific cells or tissues to regulate physiological processes
• Examples of endocrine glands include the pituitary gland (master gland), thyroid gland (metabolism), and adrenal glands (stress response)
• Hormone action can be slow and long-lasting compared to the nervous system

Nervous System

• Composed of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves and ganglia)
• Transmits electrical and chemical signals called neurotransmitters to regulate physiological processes
• Provides rapid and precise control of body functions
• Examples include regulation of muscle contraction, sensory perception, and cognitive functions

Receptors and Effectors

• Receptors are specialized structures that detect changes in the internal or external environment
• Examples of receptors include thermoreceptors (detect temperature changes), chemoreceptors (detect chemical changes), and mechanoreceptors (detect mechanical stimuli)
• Effectors are cells, tissues, or organs that respond to signals from the control center to bring about a change in the body
• Examples of effectors include muscles (contraction or relaxation), glands (secretion), and blood vessels (dilation or constriction)

Homeostatic Imbalances

Causes and Consequences of Homeostatic Imbalances

• Homeostatic imbalances occur when the body's feedback and control systems fail to maintain a stable internal environment
• Causes of homeostatic imbalances include genetic factors, environmental stressors, infections, and lifestyle choices
• Consequences of homeostatic imbalances can range from mild symptoms to severe disorders and diseases
• Examples of homeostatic imbalances include diabetes (impaired glucose regulation), hypertension (high blood pressure), and hypothyroidism (underactive thyroid gland)