mod 8 manus Flashcards
(45 cards)
Define homeostasis and explain its importance
Homeostasis is the maintenance of a stable internal environment despite changes in the external environment. It’s crucial for optimal bodily functions, enzyme activity, and metabolic efficiency, ensuring cells operate under optimal conditions for survival.
Explain how negative feedback mechanisms work in homeostasis
Negative feedback involves detecting change through receptors, processing information in a control center, and initiating corrective responses through effectors to reverse the change. This creates a loop that maintains stability by counteracting deviations from the set point.
Describe the role of the nervous system in maintaining homeostasis
The nervous system detects changes through sensory receptors, processes information in the central nervous system, and initiates rapid responses through motor neurons and effectors. It coordinates immediate responses to maintain homeostasis through electrical signals (action potentials).
Explain the role of the endocrine system in maintaining homeostasis
The endocrine system maintains homeostasis through hormone secretion from glands. Hormones travel through the bloodstream to target cells, triggering slower but longer-lasting responses than the nervous system. It regulates metabolism, growth, reproduction, and stress responses.
Compare and contrast the nervous and endocrine systems in homeostatic regulation
The nervous system provides rapid, short-term responses via electrical signals through neurons, while the endocrine system offers slower, longer-lasting responses via hormones through the bloodstream. Both systems often work together, with the hypothalamus serving as a key integration point.
Describe the structure and function of the pituitary gland
The pituitary gland has anterior and posterior lobes. The anterior lobe is controlled by hypothalamic hormones and regulates growth, thyroid, adrenal glands, and gonads. The posterior lobe, controlled by nerve impulses, releases ADH to regulate water concentration and oxytocin for uterine contractions and milk release.
Explain how the body regulates temperature in response to heat
When body temperature rises, thermoreceptors signal the hypothalamus, which initiates responses including: vasodilation (increasing blood flow to the skin), sweating (evaporative cooling), reduced metabolic rate, and behavioral changes like seeking shade. These mechanisms increase heat loss and decrease heat production.
Explain how the body regulates temperature in response to cold
When body temperature drops, thermoreceptors signal the hypothalamus, which initiates responses including: vasoconstriction (reducing blood flow to the skin), shivering (generating heat through muscle contractions), increased metabolic rate, and behavioral changes like seeking warmth or curling up.
Describe the structural adaptations that help endotherms maintain body temperature
Structural adaptations include insulation (fur, feathers, blubber), surface area to volume ratio adjustments (smaller extremities in cold climates), countercurrent heat exchange systems (in limbs), and specialized features like fat deposits for insulation and energy storage.
Explain the physiological adaptations that help endotherms maintain body temperature
Physiological adaptations include metabolic rate adjustments, shivering thermogenesis, non-shivering thermogenesis (brown fat), sweating or panting for evaporative cooling, and torpor or hibernation to conserve energy during extreme conditions or food scarcity.
Describe the behavioral adaptations that help endotherms maintain body temperature
Behavioral adaptations include seeking appropriate microenvironments (shade, sun, water), changing body position to alter exposure, huddling with others for warmth, migration to more favorable climates, and adjusting activity patterns (becoming nocturnal in hot environments).
Explain how blood glucose levels are regulated
Blood glucose is regulated primarily by insulin and glucagon from the pancreas. When glucose levels rise, beta cells release insulin, promoting glucose uptake by cells and conversion to glycogen. When levels fall, alpha cells release glucagon, promoting glycogen breakdown and glucose release from the liver.
Describe the negative feedback loop that regulates blood glucose levels
When blood glucose rises after eating, beta cells in the pancreas detect this and secrete insulin. Insulin causes cells to take up glucose and the liver to store it as glycogen, lowering blood glucose. When levels fall too low, alpha cells secrete glucagon, which causes the liver to convert glycogen back to glucose, raising blood levels.
Explain how diabetes disrupts glucose homeostasis
In Type 1 diabetes, the immune system destroys pancreatic beta cells, preventing insulin production. In Type 2 diabetes, cells become insulin resistant. Both types result in elevated blood glucose (hyperglycemia), leading to symptoms like increased thirst, frequent urination, and long-term complications affecting the cardiovascular system, kidneys, and eyes.
Describe how water balance is maintained in the human body
Water balance is maintained through thirst mechanisms, ADH (antidiuretic hormone) secretion, and kidney function. When blood becomes concentrated, osmoreceptors in the hypothalamus trigger thirst and ADH release. ADH increases water reabsorption in the kidneys, concentrating urine and conserving water.
Explain the role of the thyroid gland in homeostasis
The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), which regulate metabolic rate, body temperature, growth, and development. It’s controlled by the anterior pituitary through thyroid-stimulating hormone (TSH), which is regulated by the hypothalamus through thyrotropin-releasing hormone (TRH).
Describe the function of the adrenal glands in homeostasis
The adrenal glands consist of the cortex and medulla. The cortex produces cortisol (stress response, metabolism), aldosterone (sodium and potassium balance), and sex hormones. The medulla produces adrenaline and noradrenaline for the fight-or-flight response, affecting heart rate, blood pressure, and glucose release.
Explain the role of the pancreas in glucose homeostasis
The pancreas contains the islets of Langerhans with alpha cells (producing glucagon) and beta cells (producing insulin). Insulin lowers blood glucose by promoting cellular uptake and storage as glycogen. Glucagon raises blood glucose by promoting glycogen breakdown and gluconeogenesis in the liver.
Describe the structure and function of neurons
Neurons consist of a cell body (soma) containing the nucleus, dendrites that receive signals, and an axon that transmits signals. They communicate via electrical impulses (action potentials) and chemical signals (neurotransmitters) at synapses, forming networks that process information and coordinate responses.
Explain how action potentials are generated and propagated
Action potentials occur when a stimulus causes sodium channels to open, allowing sodium ions to rush in and depolarize the membrane. This triggers adjacent sodium channels to open, propagating the signal. Potassium channels then open, allowing potassium to flow out and repolarize the membrane, followed by a refractory period.
Describe the process of synaptic transmission
At chemical synapses, an action potential triggers neurotransmitter release from the presynaptic neuron. These molecules cross the synaptic cleft and bind to receptors on the postsynaptic neuron, causing ion channels to open or close, which either excites or inhibits the postsynaptic neuron.
Explain the difference between the sympathetic and parasympathetic nervous systems
The sympathetic nervous system prepares the body for ‘fight or flight’ by increasing heart rate, dilating pupils, and redirecting blood to muscles. The parasympathetic system promotes ‘rest and digest’ functions by slowing heart rate, stimulating digestion, and conserving energy. They work antagonistically to maintain balance.
