Unit 2, Topic 1 Homeostasis — thermoregulation and osmoregulation Flashcards
Nervous system, endocrine system, thermoregulation, osmoregulation
What is homeostasis, and why is it important for living organisms?
Homeostasis is the process by which living organisms maintain a stable internal environment despite changes in external conditions. It is crucial for the proper functioning of cells and organs, ensuring that factors like temperature, pH, and fluid balance remain within narrow limits.
How does the nervous system use negative feedback to maintain homeostasis?
Negative feedback mechanisms involve detecting a change (stimulus), processing it in the control center (e.g., brain or spinal cord), and triggering a response to counteract the change, returning the system to its optimal state. For example, if body temperature rises, responses like sweating and vasodilation are activated to cool the body down.
What are sensory receptors, and what types are there?
Sensory receptors are specialized cells that detect specific stimuli and convert them into electrical signals. Types include:
Chemoreceptors: Detect chemical changes (e.g., taste, smell, blood composition).
Thermoreceptors: Detect temperature changes (e.g., skin, hypothalamus).
Mechanoreceptors: Detect mechanical stimuli (e.g., pressure, touch, vibration).
Photoreceptors: Detect light (e.g., rods and cones in the retina).
Nociceptors: Detect pain (e.g., extreme temperatures, mechanical damage).
What is the role of neurons in the nervous system?
Neurons are the fundamental units of the nervous system responsible for transmitting electrical and chemical signals. They include:
Sensory/Afferent Neurons: Carry information from sensory receptors to the CNS.
Interneurons: Connect sensory and motor neurons within the CNS and process information.
Motor/Efferent Neurons: Transmit signals from the CNS to effectors like muscles or glands.
Tip: Afferent- think the CNS welcoming the sensory neuron from receptors like “Ahh”, Efferent- think CNS pushing away motor neuron to effectors like “eff off”
What are the main structures of a neuron and their functions?
Dendrites: Receive signals from other neurons or sensory receptors.
Soma (Cell Body): Integrates signals and generates action potentials.
Axon: Conducts electrical impulses away from the soma.
Myelin Sheath: Insulates the axon, increasing signal transmission speed.
Nodes of Ranvier: Gaps in the myelin sheath that allow saltatory conduction.
Axon Terminal: Converts electrical signals into chemical signals and releases neurotransmitters into the synapse.
What is the resting potential of a neuron, and how is it maintained?
The resting potential is the stable electrical charge difference across the neuronal membrane when not transmitting an impulse, typically around -70 mV. It is maintained by the sodium-potassium pump, which moves 3 sodium ions out and 2 potassium ions into the cell, and by potassium channels that allow potassium to leak out.
How is an action potential transmitted along a neuron?
An action potential is an electrical signal that travels down the axon. It starts when the membrane potential reaches a critical threshold, triggering sodium channels to open and sodium ions to enter, causing depolarization. Potassium channels then open, allowing potassium to exit, repolarizing the membrane.
What occurs during synaptic transmission?
When an action potential reaches the axon terminal, it triggers calcium channels to open, allowing calcium ions to enter. This causes neurotransmitters to be released into the synaptic cleft, where they bind to receptors on the postsynaptic neuron, generating a response that may lead to a new action potential or inhibit the neuron.
How does signal transduction occur in the postsynaptic neuron?
Neurotransmitter binding to receptors on the postsynaptic neuron can lead to depolarization (exciting the neuron) or hyperpolarization (inhibiting the neuron). This converts the chemical signal back into an electrical signal, allowing the continuation of the nerve impulse or modulation of the response. Neurotransmitters are then broken down or reabsorbed to end the signal.
What role does the endocrine system play in maintaining homeostasis?
The endocrine system uses negative feedback mechanisms to regulate physiological processes in response to internal and external stimuli.
What is negative feedback in the context of homeostasis?
Negative feedback is a process that helps keep things balanced inside the body. When something changes, it triggers a response that works to bring things back to normal, preventing the change from going too far.
For example: When your body temperature rises (e.g. due to exercise or hot weather), your brain detects the increase. In response, it triggers cooling mechanisms like sweating and increasing blood flow to the skin. These actions help lower your body temperature back to its normal range. Once the temperature is back to normal, the brain reduces these cooling actions. This process of detecting a change, initiating a response to counteract it, and then adjusting the response as needed is an example of negative feedback.
How does the stimulus-response model operate in the endocrine system?
The stimulus-response model starts with a stimulus (e.g., a change in blood glucose levels), detected by receptors. The information is sent to an endocrine gland, which releases hormones into the bloodstream. These hormones travel to target cells or organs to restore balance and maintain homeostasis.
Provide an example of negative feedback involving blood glucose levels.
e.g. After a meal, if blood sugar rises, the pancreas releases insulin to facilitate glucose uptake by cells, reducing blood sugar levels. Once normal levels are restored, insulin secretion decreases. Conversely, if blood sugar levels fall, the pancreas releases glucagon to stimulate glucose release from the liver, increasing blood sugar levels.
What are hormones, and how do they affect target cells?
Hormones are chemical messengers secreted by endocrine glands into the bloodstream or lymphatic fluid. They affect target cells by binding to specific receptors, triggering cellular changes such as altering gene expression, regulating enzyme activity, or modifying membrane permeability.
How do cells regulate their sensitivity to hormones?
Cells regulate sensitivity by upregulating or downregulating (increasing or decreasing) the number of receptors for a hormone on or in a cell depending on the type of hormone (if the hormone is water soluble it will be on the surface, if it is fat soluble it will be in the cell). High hormone levels can lead to a reduction in receptor numbers to prevent overstimulation, while low hormone levels can lead to an increase in receptor numbers to enhance response.
What are endotherms?
Endotherms are animals that maintain a stable internal body temperature through internal heat production, regardless of external conditions.
What is brown adipose tissue and its role in endotherms?
Brown adipose tissue is rich in mitochondria and generates heat through non-shivering thermogenesis to help maintain body temperature in cold conditions.
How does insulation help endotherms?
Insulation, such as fur, feathers, or subcutaneous fat, reduces heat loss by trapping a layer of air close to the skin, providing a barrier against the cold.
What is kleptothermy?
Kleptothermy is a behavioural adaptation where animals share or steal heat from other organisms, such as huddling together for warmth.
What is hibernation?
Hibernation is a state of prolonged torpor during cold months where metabolic rate and body temperature drop significantly to conserve energy.
What is aestivation?
Aestivation is a state similar to hibernation but occurs during hot or dry periods to avoid heat stress.
What is torpor?
Torpor is a short-term reduction in body temperature and metabolic rate, allowing animals to save energy when food is scarce or during extreme temperatures.
