Topic 3: Homeostasis

Question 1

What is Homeostasis?

Answer 1

Maintenance of relatively constant internal environment, ensuring optimum conditions for body to function.

Question 2

What is the tolerance range?

Answer 2

Difference between maximum and minimum tolerance limits.

Question 3

What are abiotic factors that affect tolerance limits in Plants?

Answer 3

• Light (Photosynthesis)
• Water Availability
• CO2 concentration
• pH of soil

Question 4

What are abiotic factors that affect tolerance limits in Animals?

Answer 4

• Body Temperature
• Water Availability
• Blood Glucose Levels

Question 5

What makes up the Stimulus Response Model?

Answer 5

1. Stimulus
2. Receptor
3. Effectors
4. Response

Question 6

What is a Stimulus? (Stimulus Response)

Answer 6

Detectable change in the internal or external environment

Question 7

What are Receptors? (Stimulus Response)

Answer 7

Detect Stimuli in the body.
Examples:
- Chemoreceptors (blood’s chemical composition)
- Thermoreceptors (temperature)
- Mechanoreceptors (pressure, sound, touch)

Question 8

What are Effectors? (Stimulus Response)

Answer 8

Glands or muscles that bring about a response.

Question 9

What is the Response? (Stimulus Response)

Answer 9

Inhibits/reverses original stimulus

NEGATIVE FEEDBACK

Question 10

What makes up the Central Nervous System (CNS)? What is its function?

Answer 10

Brain and Spinal Cord

Function: Receive messages, process & manage response

Question 11

What makes up the Peripheral Nervous System (PNS)? What is its Function?

Answer 11

All other Nerves

Function: Transmission of info to & from the CNS

Question 12

What are the three types of Neurons?

Answer 12

• Sensory neurons
• Interneurons
• Motor neurons

Question 13

Where are Sensory Neurons located? What is its function?

Answer 13

PNS

Function: Send nerve impulses from detected stimulus towards the CNS

Question 14

Where are Interneurons located? What is its function?

Answer 14

CNS

Function: Relay signals from sensory neurons to motor neurons

Question 15

Where are Motor Neurons located? What is its function?

Answer 15

PNS

Function: Sends nerve impulses from CNS to effectors (muscles & glands)

Question 16

What is the nerve cell pathway?

Answer 16

Sensory Neuron —-> Interneuron —-> Motor Neuron

Question 17

What is the structure of Nerve Cells?

Answer 17

Dendrites - receive impulses from other neurons & transmits info towards cell body.
Cell Body - Contains organelles
Axons - transmits nerve impulses towards another cell
Myelin Sheath - Insulating layer around Axons
Axon Terminals - transmits signals to other cells.

Question 18

What are the structural differences between nerve cells?

Answer 18

Size: Sensory & Motor Neurons are Longer
Location of Cell Body:
- Sensory: Axon branches from cell body (to the side)
- Interneuron: Directly between dendrites and axons
- Motor: Dendrites extend directly from cell body

Question 19

What are Reflex Responses?

Answer 19

Automatic response to a Stimulus without conscious thought

*Brain is NOT directly involved, ONLY Spinal Cord

Question 20

What is the function of the endocrine system?

Answer 20

Produce and secrete hormones that travel around the body via the blood and bind to specific receptors in or on target cells.

Question 21

What are the types of hormones?

Answer 21

Peptide - short amino acid chains (∼ 20 amino acids)
Protein hormones - long polypeptide chains
Steroids - Lipids (Hydrophobic - pass through cell membrane)
Amino-Acid derivatives - chemically altered amino acids

Question 22

How do Hydrophilic hormones cause intracellular change?

Answer 22

Hydrophilic = Water soluble (cannot pass through cell membrane)
Bind to specific receptor molecules on Target Cells.
Examples: Peptides & Protein hormones

Question 23

How do Hydrophobic hormones cause intracellular change?

Answer 23

Hydrophobic = Lipid Soluble (Can pass through cell membrane)
Bind to specific receptors inside the cell.
Examples: All Steroid Hormones

Question 24

What are the differences between the Nervous (NS) and Endocrine systems (ES)?

Answer 24

Pathway: Direct Pathway via neurons (NS), Indirect pathway via Blood (ES)
Message type: Electro-chemical (NS), Chemical (ES)
Specificity: Highly Specific target cells (NS), Multiple Target Cells (ES)
Speed: Fast Transmission (NS), Slow Transmission (ES)
Duration: Short-term (NS), Long-term (ES)

Question 25

What is the response to High Blood Glucose Levels?

Answer 25

1. Pancreatic Cells release insulin 2. Insulin binds to receptor/muscle cells 3. Muscle & Liver Cells stimulate uptake of Glucose 4. Blood Glucose Decreases

Question 26

What is the response to Low Blood Glucose Levels?

Answer 26

1. Glucagon is secreted by Pancreas 2. Stimulates breakdown of Glycogen in Liver 3. Glucose is released into the blood 4. High Blood Glucose Levels

Question 27

What is Diabetes Mellitus? (Diabetes)

Answer 27

Condition that impairs the body's ability to process blood glucose

Question 28

What is Type 1 Diabetes?

Answer 28

Reduced production of Insulin in pancreas

Question 29

What is Type 2 Diabetes?

Answer 29

Body becomes resistant to normal effects of Insulin

Question 30

What is the role of adrenaline in Fight of Flight Responses?

Answer 30

- Increases availability of energy ( ↑ aerobic respiration) - Triggers breakdown of glycogen - ↑ Heart and breathing rate - Blood Glucose is directed away from skin, Kidney's and Digestive Organs

Question 31

What are the responses to High Body Temperature?

Answer 31

1. Hypothalamus --- Nerve Impulses --- Sweat Glands --- Secrete Sweat (Sweat evaporates, removing heat) 2. Hypothalamus --- ↓ secretion of TSH --- ↓ secretion of thyroxine 3. Vasodilation --- Increased blood flow near surface of skin --- greater heat loss

Question 32

What are the responses to Low Body Temperature?

Answer 32

1. Hypothalamus --- Nerve impulses to skeletal muscles --- Shivering ( ↑ Respiration) 2. Hypothalamus --- Vasoconstriction --- ↓ blood flow near surface of cells --- ↓ Heat released 3. Hypothalamus --- Release of TSH --- Thyroxine --- ↑ heat released by cells

Question 33

What is the response to High Osmolarity (↓ Water Conc.)?

Answer 33

1. Hypothalamus --- Stimulates release of ADH 2. ADH is transported to kidney's via the blood 3. ADH binds to target receptors in cells of distal convoluted tubule and collecting ducts 4. Binding of ADH - ↑ permeability of water (water diffuses into the blood from filtrate) 5. Osmolarity ↓ * ↓ Volume of water excreted in Urine*

Question 34

What is the response to Low Osmolarity (↑ Water Conc.)?

Answer 34

1. Hypothalamus inhibits release of ADH 2. ↓ ADH is transported to kidneys --- ↓ permeability to water 3. ↓ Water is reabsorbed into the blood from filtrate 4. ↑ Osmolarity * ↑ Volume of water excreted in Urine*

Question 35

What is the model answer for responding to change in homeostasis?

Answer 35

When the [receptor] detects a change in [factor] that is too [high/low], it will stimulate the synthesis and the secretion of the hormone [...]. [Hormone name] will then travel around the body via the blood and bind to specific receptors on [...] and thus cause ...