Module 5: section 1- Communication and Homeostasis

Question 1

Why is Responding to the Environment Important?

Answer 1

Increases chances of survival by responding to external and internal changes.
External example: Avoid harmful environments (e.g., too hot/cold).
Internal example: Control conditions for optimal metabolism.
Plants also respond to environmental changes.
A stimulus is any change in the internal or external environment.

Question 2

How Do Receptors and Effectors Work?

Answer 2

Receptors detect stimuli:
Receptors are specific to one stimulus type (e.g., pressure, light).
Different receptors detect different types of stimuli.
Some receptors are cells (photoreceptors) , others are proteins on cell membranes.
Effectors produce a response:
Effectors include muscles or glands (e.g., pancreas).

Question 3

How Do Cells Communicate to Produce a Response?

Answer 3

Receptors need to communicate with effectors to produce a response.
In the nervous system, neurotransmitters are used.
In the hormonal system, chemicals (hormones) travel through the blood to distant cells.
Cell-surface receptors recognize signaling chemicals.

Question 4

What is Homeostasis and Why is It Important?

Answer 4

Definition: Maintenance of a constant internal environment.
Maintains the internal environment despite external changes.
Ensures cells function normally and avoid damage.
Temperature control:
High temperature: enzymes denature, lowering reaction efficiency.
Low temperature: enzyme activity slows down, slowing reactions.
Optimum temperature for enzymes: 37°C in humans.
Glucose concentration also needs to be controlled for respiration.

Question 5

How Do Homeostatic Systems Respond to Changes?

Answer 5

Homeostatic systems involve receptors, a communication system, and effectors.
Receptors detect when a level is too high or too low.
The nervous or hormonal system sends the information to effectors.
The mechanism that brings the level back to normal is called negative feedback.

Question 6

What is Negative Feedback?

Answer 6

Negative feedback restores the level to normal.
It keeps conditions within a narrow range around the normal level (e.g., body temperature close to 37°C).
It only works within certain limits—if the change is too large, negative feedback may fail to correct it (e.g., severe exposure to cold).

Question 7

What is Positive Feedback?

Answer 7

Positive feedback amplifies a change from the normal level.
It pushes the level away from normal (e.g., blood clot formation).
It rapidly activates processes, like clotting or triggering labor.
Positive feedback is not involved in homeostasis because it doesn’t maintain a constant internal environment.

Question 8

What are Examples of Positive and Negative Feedback?

Answer 8

Negative feedback example: Body temperature regulation—effectors act to reduce or increase temperature when it’s too high or low.
Positive feedback example: Platelets activated to form a blood clot when there’s an injury. This amplifies the clotting process until the wound is sealed.

Question 9

How Does Negative Feedback Relate to Homeostasis?

Answer 9

Negative feedback maintains homeostasis by bringing levels back to normal when they drift too high or low.
Homeostasis ensures the internal environment remains stable within set limits, preventing damage to cells or organ systems.

Question 10

what is homeostasis?

Answer 10

Homeostasis is the maintenance of a stable internal environment in the body. It involves regulating factors like temperature, pH, and glucose levels to ensure optimal functioning, even when external conditions change.

Question 11

How is temperature controlled differently in ectotherms and endotherms?

Answer 11

Ectotherms rely on external factors (like sunlight) for temperature regulation, whereas endotherms maintain their temperature internally through metabolic processes.

Question 12

How What are some characteristics of ectotherms? do endotherms control body temperature?

Answer 12

Ectotherms cannot generate their own heat internally and are heavily dependent on external temperatures. Their activity level is influenced by environmental temperatures, and they have lower metabolic rates than endotherms.

Question 13

What are some characteristics of endotherms?

Answer 13

Endotherms generate heat internally through metabolic activity. They have a higher metabolic rate, allowing them to maintain a stable body temperature regardless of the environment. They use mechanisms like sweating, shivering, and changing blood flow to regulate temperature.

Question 14

What mechanisms help increase body temperature in mammals?

Answer 14

Sweating: Sweat evaporates from the skin, using heat energy from the body and cooling it down.
Hairs lying flat: Reduces the insulating layer of air, allowing more heat to be lost.
Vasodilation: Blood vessels near the skin surface widen, increasing blood flow to the skin and promoting heat loss via radiation.

Question 15

What mechanisms do mammals use to increase body temperature?

Answer 15

Shivering: Rapid muscle contractions generate heat.
Hairs standing up: Traps a layer of insulating air close to the skin, reducing heat loss.
Vasoconstriction: Blood vessels near the skin surface narrow, reducing blood flow to the skin and minimizing heat loss.

Question 16

How does the hypothalamus control body temperature in mammals?

Answer 16

The hypothalamus maintains a constant body temperature by processing information from thermoreceptors in the skin and the brain. It sends signals to effectors (like muscles or sweat glands) to initiate responses that either increase or decrease body temperature.

Question 17

What are the roles of thermoreceptors in body temperature regulation?

Answer 17

Peripheral thermoreceptors: Located in the skin, they detect external temperature changes.
Central thermoreceptors: Located in the hypothalamus, they monitor the temperature of the blood.

Question 18

What is the process of vasodilation and how does it aid in cooling the body?

Answer 18

Vasodilation involves widening the arterioles near the skin surface. This increases blood flow to the skin, allowing more heat to be lost via radiation, conduction, and convection, which helps cool the body.

Question 19

What is vasoconstriction and how does it help the body conserve heat?

Answer 19

Vasoconstriction involves narrowing the arterioles near the skin surface. This reduces blood flow to the skin, keeping heat in the body’s core and reducing heat loss, helping to conserve warmth in cold conditions.

Question 20

Why do mammals in cold climates have specific adaptations like thick fur or fat layers?

Answer 20

These adaptations, like thick fur and fat layers, provide insulation to reduce heat loss. Fur traps warm air close to the skin, and fat layers act as a barrier to heat loss, both helping to maintain a stable internal temperature.

Question 21

What role does shivering play in thermoregulation?

Answer 21

Shivering generates heat through rapid, involuntary muscle contractions, increasing the metabolic rate and raising body temperature when it’s cold.

Question 22

How does the hypothalamus respond when the body temperature is too high?

Answer 22

If body temperature is too high, the hypothalamus triggers responses like sweating and vasodilation, causing the body to lose heat and lower temperature back to normal.

Question 23

How does the hypothalamus respond when the body temperature is too low?

Answer 23

If the temperature is too low, the hypothalamus signals for shivering, vasoconstriction, and metabolic adjustments to generate and conserve heat, raising the body temperature.

Question 24

What is excretion and why is it important?

Answer 24

Excretion is the removal of waste products produced by the body during metabolism. These waste products, if not removed, can be harmful and disrupt bodily functions. The liver plays a key role in excreting harmful substances, such as ammonia (a byproduct of amino acid breakdown), which is converted to urea and excreted.

Question 25

What are the main functions of the liver in excretion and energy storage?

Answer 25

The liver:
• Breaks down amino acids to remove excess nitrogen, forming urea (deamination process).
• Detoxifies harmful substances like alcohol and drugs.
• Stores glycogen, converting excess glucose to glycogen for energy storage and releasing it as needed.
• Maintains blood sugar levels by converting stored glycogen back to glucose.

Question 26

Describe deamination and its role in amino acid breakdown in the liver.

Answer 26

Deamination is the removal of the amino group (NH2) from amino acids. This process:
• Converts the amino group into ammonia, which is toxic.
• Ammonia is quickly converted into urea, a less toxic compound, in the urea cycle.
• Urea is then transported in the blood to the kidneys for excretion.

Question 27

How does the liver handle harmful substances other than amino acids?

Answer 27

The liver detoxifies various harmful substances, such as:
1. Alcohol: Broken down into ethanal, then into a less toxic substance. Excessive alcohol consumption can damage liver cells.
2. Paracetamol: Excessive intake can lead to liver damage.
3. Insulin: Broken down to maintain proper blood glucose levels.

Question 28

How does the liver store glycogen, and why is it important?

Answer 28

The liver converts excess glucose into glycogen and stores it in liver cells. When blood glucose levels drop, the liver converts glycogen back into glucose, releasing it into the bloodstream to maintain energy balance.

Question 29

Describe the blood supply to the liver and how it supports its functions.

Answer 29

The liver receives blood from:
• The hepatic artery which supplies oxygenated blood.
• The hepatic portal vein which supplies deoxygenated blood rich in nutrients absorbed from the digestive system.
• Blood flows through liver sinusoids (small capillaries), allowing hepatocytes to process nutrients and filter out harmful substances.

Question 30

What are sinusoids, and what role do they play in the liver?

Answer 30

Sinusoids are small capillaries in the liver where blood from the hepatic artery and portal vein mix. This blood flows past liver cells (hepatocytes) which remove and process nutrients, drugs, and toxins. Sinusoids also contain Kupffer cells that break down old red blood cells and remove bacteria.

Question 31

What is the function of Kupffer cells in the liver?

Answer 31

Kupffer cells are specialized cells in the liver attached to the walls of sinusoids. They:
• Remove bacteria and old red blood cells from the blood.
• Help maintain immune defense by breaking down foreign substances.

Question 32

How does the liver produce and excrete bile?

Answer 32

Hepatocytes in the liver produce bile, which is secreted into small bile canaliculi. Bile flows through these canaliculi into larger bile ducts and eventually collects in the gall bladder. Bile aids in the digestion and absorption of fats in the small intestine.

Question 33

Explain the pathway of blood through the liver and the exit of blood.

Answer 33

Blood enters the liver through the hepatic artery and portal vein, flows through sinusoids where it’s processed, and then exits via the central vein. The central veins merge to form the hepatic vein, which carries processed blood away from the liver to the heart.

Question 34

What are the main structures visible when examining liver tissue under a microscope?

Answer 34

When viewing liver tissue:
• Liver lobules appear as hexagonal shapes, with a central vein in the middle.
• Sinusoids are spaces between rows of liver cells, where blood flows.
• Hepatocytes (liver cells) perform functions like detoxification and bile production.
• Kupffer cells are specialized cells within the sinusoids that remove bacteria and old red blood cells.

Question 35

What are the key functions of each part of the liver lobule?

Answer 35

• Hepatocytes: Detoxify harmful substances and produce bile.
• Kupffer cells: Break down old red blood cells and remove bacteria.
• Canaliculi: Small channels that carry bile from hepatocytes to bile ducts.
• Sinusoids: Capillaries that carry blood from the hepatic artery and portal vein, allowing hepatocytes to process blood.

Question 36

What is the main function of the kidneys in excretion?

Answer 36

The kidneys remove urea and other waste products from the blood to form urine. They regulate water and ion balance, maintaining blood pressure and overall homeostasis.

Question 37

Describe the blood supply to the kidneys and the process of blood filtration.

Answer 37

Blood flows into each kidney through the renal arteries. Inside the kidneys, blood is filtered in tiny units called nephrons. Cleaned blood leaves the kidneys via the renal veins.

Question 38

What is the structure and function of a nephron?

Answer 38

Each nephron starts with Bowman’s capsule, which encloses a bundle of capillaries called the glomerulus.

Each nephron starts with Bowman’s capsule, which encloses a bundle of capillaries called the glomerulus.
• Blood enters the glomerulus at high pressure, forcing small molecules (like water, ions, and urea) through the capillary walls into Bowman’s capsule. This fluid is called filtrate.
• Larger molecules, like proteins, remain in the blood.

Question 39

What is ultrafiltration and where does it occur?

Answer 39

Ultrafiltration is the process by which blood pressure forces small molecules (water, ions, glucose, and urea) from the blood in the glomerulus into Bowman’s capsule. This filtration only allows smaller molecules to pass, while larger molecules remain in the blood.

Question 40

Explain the importance of Bowman’s capsule and the glomerulus in the nephron.

Answer 40

Bowman’s capsule collects the filtrate produced by ultrafiltration in the glomerulus. The glomerulus is a network of capillaries where blood pressure forces fluid and small molecules into Bowman’s capsule to begin the process of urine formation

Question 41

Describe the pathway of filtrate after it leaves Bowman’s capsule.

Answer 41

After filtration in Bowman’s capsule:
• The filtrate passes through the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule, where various ions and water are reabsorbed as needed.
• The remaining fluid, now called urine, collects in the collecting duct and moves to the ureter, which transports urine to the bladder.

Question 42

What happens to blood pressure as it enters the nephron, and why is this important?

Answer 42

Blood enters the glomerulus at high pressure due to the narrow diameter of the afferent arteriole compared to the efferent arteriole. This high pressure is essential for ultrafiltration, pushing small molecules into Bowman’s capsule.

Question 43

Which substances are reabsorbed in the nephron tubules, and where does this occur?

Answer 43

Glucose is reabsorbed in the proximal convoluted tubule (PCT) by active transport.
• Amino acids are also reabsorbed in the PCT by active transport.
• Water is reabsorbed throughout the nephron, especially in the descending limb of the loop of Henle and the collecting duct, by osmosis.
• Ions like sodium and chloride are actively reabsorbed in the PCT and loop of Henle.
• Urea is partially reabsorbed to maintain concentration gradients but is mainly excreted.

Question 44

Explain selective reabsorption in the nephron and why it is important.

Answer 44

Selective reabsorption is the process by which essential substances (glucose, amino acids, ions, and some water) are reabsorbed back into the blood from the filtrate in the nephron. This process is crucial to conserve necessary nutrients and maintain homeostasis, ensuring that only waste products remain in the urine.

Question 45

What is the role of the proximal convoluted tubule (PCT) in reabsorption?

Answer 45

The PCT reabsorbs most of the filtrate’s glucose, amino acids, and ions through active transport. It also reabsorbs a significant amount of water through osmosis. The PCT cells have numerous mitochondria to provide energy for active transport.

Question 46

Describe the function of the loop of Henle.

Answer 46

The loop of Henle:
• Creates a concentration gradient in the medulla to facilitate water reabsorption.
• The descending limb is permeable to water but not to ions, leading to water reabsorption.
• The ascending limb is impermeable to water but actively transports ions (like sodium and chloride) out, maintaining high salt concentration in the medulla.

Question 47

What is the role of the distal convoluted tubule (DCT) and the collecting duct in reabsorption?

Answer 47

• DCT: Fine-tunes ion reabsorption, particularly sodium and calcium, and is influenced by hormones such as aldosterone.
• Collecting Duct: Reabsorbs water under the control of the hormone ADH (antidiuretic hormone). This helps concentrate the urine depending on the body’s hydration level.

Question 48

What is a kidney dissection, and what can be observed during this process?

Answer 48

dissection is a lab exercise where the kidney is cut open to observe its structure. Key structures visible include:
• The outer renal cortex, where glomeruli are located.
• The inner renal medulla, containing loops of Henle and collecting ducts.
• The renal pelvis, where urine collects before entering the ureter.

Question 49

Describe the procedure for preparing a kidney for dissection.

Answer 49

1. Remove any fat surrounding the kidney.
2. Observe the outside, noting the renal capsule and any blood vessels.
3. Make a longitudinal cut to reveal the internal structures (cortex, medulla, and renal pelvis).
4. Use diagrams to identify key areas within the kidney.

Question 50

Why do proteins not normally appear in urine?

Answer 50

Proteins are large molecules that cannot pass through the filtration barrier in the glomerulus, so they remain in the bloodstream rather than entering the filtrate in Bowman’s capsule.

Question 51

How does ADH (antidiuretic hormone) affect the collecting duct?

Answer 51

ADH increases the permeability of the collecting duct to water, allowing more water to be reabsorbed into the bloodstream. This helps to concentrate urine and conserve water in the body, especially when hydration levels are low.