Mod 5 Flashcards
(85 cards)
The Importance of Communication in Organisms
Communication is vital for the survival of all living organisms.
Organisms must detect and respond to environmental changes.
Nervous and endocrine systems trigger necessary changes in multicellular organisms.
Effective communication allows organisms to adapt to their surroundings.
Survival relies on both internal and external environmental responses.
Understanding Cell Signalling Mechanisms
Cell signalling involves communication between cells via electrical signals or hormones.
Neuronal signalling is faster and more short-term than chemical signalling.
Endocrine signalling enables long-distance communication through the circulatory system.
Paracrine signalling occurs between nearby cells, often using extracellular fluid.
Autocrine signalling allows cells to stimulate their own receptors and trigger internal responses.
Understanding Homeostasis: Maintaining Internal Balance
Homeostasis regulates internal conditions in organisms.
Key factors include temperature, water potential, pH, and blood glucose levels.
It maintains stability despite external environmental changes.
Homeostasis is crucial for the proper functioning of cells and organs.
Disruptions in homeostasis can lead to health issues.
The Role of Negative Feedback in Maintaining Internal Conditions
Negative feedback helps counteract changes in internal conditions.
It works to reverse changes and restore optimal conditions.
Sensory receptors detect internal condition changes.
Effectors, like muscles and glands, respond to the detected changes.
Messages from receptors are communicated through the nervous or hormonal system to initiate a response.
Understanding Positive Feedback Mechanisms
Positive feedback enhances changes in a system.
It is less common than negative feedback.
An example is cervical dilation during childbirth.
Positive feedback amplifies the original condition.
This mechanism has an opposing effect to negative feedback.
Understanding Ectotherms: Temperature Regulation
Ectotherms regulate body temperature using external sources.
They cannot increase respiration rates for internal heat production.
Temperature control involves heat exchange with the environment.
They may expose themselves to sunlight or hide from it for warmth.
Breathing rate can increase to promote heat loss through evaporation.
Understanding Endotherms: Temperature Regulation
Endotherms maintain a constant body temperature regardless of external conditions.
They have thermoreceptors that detect changes in core body temperature.
Thermoreceptors send information to the hypothalamus for processing.
The hypothalamus coordinates responses to restore optimal temperature.
Responses can be physiological or behavioral in nature.
Endothermic Temperature Regulation Mechanisms
Endotherms use shivering to increase body temperature through muscle contractions.
Sweat glands produce sweat to lower body temperature via evaporation.
Skin hairs can lie flat to minimize insulation or raise to provide insulation.
Arterioles dilate to increase heat loss by bringing blood closer to the skin.
Arterioles also constrict to reduce blood flow and minimize heat loss.
What is excretion and why is it important?
During metabolism, waste products are produced, that is products not required by cells such as carbon dioxide or nitrogen containing ammonia. As the majority of waste products are toxic, the removal of metabolic waste known as excretion is of high importance.
Understanding Liver Lobules and Their Functions
Liver lobules are cylindrical structures composed of hepatocytes arranged in rows.
Each lobule connects to the hepatic vein for deoxygenated blood removal.
The hepatic artery supplies oxygenated blood to the liver lobules.
Lobules are connected to the hepatic portal vein carrying digestion products.
Bile ducts transport bile to the gallbladder for fat emulsification.
The Role of Sinusoids in Liver Function
Sinusoids connect the central vein to the hepatic artery and portal vein.
Hepatocytes and sinusoids break down toxic substances.
Processed blood returns to the central vein and then to the hepatic vein.
Sinusoids contain Kupffer cells for breaking down old red blood cells.
Kupffer cells also help in the removal of bacteria from the blood.
The Liver’s Role in Amino Acid Breakdown
The liver processes excess amino acids from protein digestion.
Excess amino acids must be excreted to prevent toxicity.
Nitrogenous substances from amino acids are harmful to the body.
If not utilized, excess amino acids cannot remain in the body.
The liver plays a critical role in detoxifying these substances.
Amino Acid Excretion Process
Deamination removes amino groups from excess amino acids.
Ammonia and organic acids are formed during deamination.
Organic acids can produce ATP or be converted into glycogen.
Ammonia is converted to urea in the ornithine cycle.
Urea is released into the blood and filtered by the kidneys.
What other processes is the liver involved in?
Apart from this, the liver is involved in the detoxification process, that is the removal of harmful substances such as drugs and alcohol. For instance, the liver breaks alcohol down into ethanal which is further broken down into acetic acid.
Understanding Kidney Functions
Kidneys primarily excrete waste products like urea in urine.
Blood enters the kidneys via the renal artery.
Waste is filtered from blood in the kidney’s capillaries.
Filtration occurs in nephrons through ultrafiltration.
Nephrons are long tubules that surround the capillaries.
Understanding Selective Reabsorption in Kidneys
Selective reabsorption is a process in the kidneys.
Useful substances like amino acids, glucose, and vitamins are reabsorbed through tubules.
Excess substances pass through tubules and ureters to reach the bladder.
These substances are ultimately disposed of as urine.
Filtered blood exits the kidneys via the renal vein.
Understanding Ultrafiltration in the Nephron
Blood enters the Glomerulus via the afferent arteriole and exits through the efferent arteriole.
The afferent arteriole has a wider lumen, increasing hydrostatic pressure in the glomerulus.
Water and small molecules under 69,000 Mr can pass into the Bowman’s capsule.
Filtrate in the Bowman’s capsule consists of water, glucose, amino acids, urea, ions, and hormones.
Red blood cells and plasma proteins are too large to enter the nephron.
Understanding Selective Reabsorption in the Nephron
Selective reabsorption occurs in the proximal convoluted tubule (PCT).
100% of glucose and amino acids are reabsorbed in the PCT.
A significant amount of water and salts are also reabsorbed in this area.
PCT cells have microvilli for a larger surface area and many mitochondria for ATP production.
Glucose and amino acids are reabsorbed via active transport using co-transporter proteins with Na+.
Understanding the Loop of Henle
The Loop of Henle creates a low water potential in the kidney’s medulla.
It functions as a countercurrent multiplier to establish concentration gradients.
The descending limb allows water to exit, lowering the filtrate’s water potential.
The ascending limb is impermeable to water but allows Na+ and Cl- to exit.
This mechanism enables the kidney to produce urine more concentrated than blood.
Understanding Water Reabsorption and Hormonal Control
Dehydration leads to lower blood water potential.
More water is reabsorbed from the loop of Henle, distal convoluted tubule, and collecting duct.
This process results in the production of concentrated urine.
The opposite occurs when blood water content is high.
Hormones are crucial for regulating water reabsorption.
Regulation of Blood Water Potential by Osmoreceptors
Osmoreceptors in the hypothalamus monitor blood water potential.
Low water potential triggers the hypothalamus to release ADH from the posterior pituitary.
ADH increases permeability of DCT and collecting ducts to water.
Enhanced water reabsorption leads to concentrated urine production.
Well-hydrated states result in opposite effects, reducing ADH release.
How ADH Enhances Water Reabsorption
ADH binds to receptors on collecting duct cell membranes.
This binding activates enzymes that produce cAMP.
cAMP causes vesicles to fuse with the plasma membrane.
Vesicles contain aquaporins, which are water channel proteins.
Inserting aquaporins increases cell permeability to water.
Understanding Kidney Failure and Its Consequences
Kidney failure can be triggered by infections causing inflammation.
Damaged kidneys filter and reabsorb less efficiently.
High blood pressure can harm kidney capillaries, leading to larger molecules in urine.
Toxic waste buildup from kidney failure can cause symptoms like vomiting.
Fluid accumulation from kidney failure can lead to swelling and disrupt ion balance.
Understanding Renal Dialysis for Kidney Failure
Renal dialysis filters blood using a machine and dialysis fluid.
It helps remove waste products, excess water, and ions from the body.
Dialysis is a temporary measure while patients wait for a kidney transplant.
Patients typically need dialysis several times a week.
Patients may feel unwell between dialysis sessions due to accumulating toxins.
