Feb 11th

Question 1

Claude Bernard

Answer 1

• father of modern physiology
• our internal environment remains remarkably constant despite changes in the external milieu

Question 2

Walter Cannon

Answer 2

• coined the term “homeostasis” to describe the relative stability of the internal environment

Question 3

Homeostasis

Answer 3

1. SENSOR: detects shift in physiological variable outside normal range
2. INTEGRATION/CONTROL CENTER: Processes the information and determines the appropriate response
3. EFFECTOR: Carries out the response to restore balance

Question 4

Homeostasis - negative feedback loops

Answer 4

Negative feedback loops reverse a change to maintain balance, unlike positive feedback loops, which amplify a response.
Ex: Body Temperature Regulation
- If too hot: The body sweats to cool down.
- If too cold: The body shivers to generate heat.

Question 5

what does homeostatic control rely on?

Answer 5

1. Sensor: constantly monitors
2. Integrating center: coordinates
3. Response system: changes

Question 6

components of homeostatic systems

Answer 6

1. Sensory system (monitor)
2. Integrating center
3. Response system (adjustment)
4. Negative feedback

Question 7

Major regulatory systems

Answer 7

• skin
• cardiovascular
• renal
• digestive
• respiratory
• musculo-skeletal

Question 8

the regulated factors

Answer 8

• water
• electrolytes/ pH
• nitrogenous compounds
• oxygen
• carbon dioxide
• temperature
• toxicants

Question 9

hyper function

Answer 9

too much hormone

Question 10

hypo function

Answer 10

too little hormone

Question 11

resistance

Answer 11

too little effect

Question 12

what is the endocrine gland

Answer 12

a tissue which releases (secretes) a substance into the blood stream; this substance then travels via the blood to influence a target cell

Question 13

what makes a chemical a hormone

Answer 13

a chemical messenger secreted by glands, travelling through the bloodstream to regulate physiological functions

Question 14

types of hormones

Answer 14

1. proteins & polypeptides (<100 AA)
2. steroids (cholesterol derivatives)
3. glycoproteins
4. amines (catecholamines or thyroid hormones)

Question 15

classic minkowski experiment (1889)

Answer 15

discovery of insulin
- pancreas removal in dogs (diabetes symptoms appear)
- pancreatic tissue implantation (symptoms prevented)

Question 16

Banting & Best (1921)

Answer 16

further discovery of insulin
- found antidiabetic substance in pancreatic extracts
- injecting extracts - prevents elevated blood glucose (diabetes symptoms)

Question 17

what is the type, function and forms of insulin

Answer 17

type: peptide hormone from beta cells of the pancreas
function: helps glucose absorption in muscle and fat tissue
forms: inactive - hexamer
active - monomer

Question 18

Autocrine Signaling - hormones

Answer 18

A cell secretes a hormone or chemical messenger that binds to receptors on the same cell that released it.

Question 19

Paracrine Signaling - hormones

Answer 19

A hormone or chemical messenger is released by one cell and affects nearby cells without entering the bloodstream.

Question 20

Endocrine Signaling - hormones

Answer 20

A hormone is released into the bloodstream, traveling to distant target organs or tissues.

Question 21

What do hormones bind to?

Answer 21

Hormones bind to specific receptors in target cells to trigger a response.

Question 22

How specific are hormone receptors?

Answer 22

Very specific to their hormone, but non-specific binding (overspill) can occur.

Question 23

Why is receptor-hormone turnover important?

Answer 23

Continuous formation & breakdown of receptor-hormone complexes is essential for proper signaling.

Question 24

Where are most hormone receptors found?

Answer 24

On the plasma membrane of target cells (for peptides & protein hormones).

Question 25

Where do steroid & thyroid hormones bind?

Answer 25

Inside the target cell, to intracellular receptors.

Question 26

What do transmembrane receptors do?

Answer 26

They bind hormones outside the cell and trigger intracellular signaling.

Question 27

How do transmembrane receptors activate signals?

Answer 27

By triggering cytoplasmic pathways, often involving phosphorylation & enzyme activation.

Question 28

What are the two main effects of transmembrane receptor signaling?

Answer 28

1. DNA → mRNA → Protein response (gene expression changes). 2. Local effects (e.g., enzyme activation in the target cell).

Question 29

Adenylate cyclase pathway

Answer 29

1. Hormone + receptor, G- proteins dissociate 2. α-subunit activates AC 3. Catalyzes product of cAMP 4. Removes regulatory unit from PK 5. PK activates other molecules (hormonal response)

Question 30

Epinephrine & adenylate cyclase

Answer 30

1. Epinephrine binds to β–adrenergic receptor on liver cell 2. G-proteins activated – subunit carrying GDP dissociates, GDP →GTP 3. Subunit activates adenylyl cyclase which catalyzes ATP → cAMP 4. cAMP activates PKA, which activates phosphorylase 5. Phosphorylase converts glycogen to glucose-6-phosphate 6. Glucose-6-phosphate → glucose (released from liver)

Question 31

Phospholipase C-Ca2+ pathways

Answer 31

1. Hormone + receptor, G- proteins dissociate 2. Activates PLC 3. Causes breakdown of membrane phospholipid to IP3 4. IP3 binds to endoplasmic reticulum 5. Release of stored Ca2+ into cytoplasm 6. Ca2+ activates other molecules (hormonal response)

Question 32

what do alpha-adrenergic receptors activate

Answer 32

phospholipase C

Question 33

what do beta-adrenergic receptors activate

Answer 33

adenylate cyclase

Question 34

Steroid hormone receptors

Answer 34

1. Steroid hormone (e.g. estrogen, androgen) transported bound to plasma carrier protein * Lipophilic i.e. they move across plasma membrane 2. Steroid hormone binds cell cytoplasm receptor 3. Translocates to the nucleus, binds to DNA * Acts as a transcription factor 4. Stimulates gene transcription 5. Protein products 6. Response

Question 35

Thyroid receptors

Answer 35

1. Thyroxine (T4) + carrier binding protein 2. T4 → T3 (triiodothyronine) 3. T3 uses binding proteins to enter nucleus 4. Hormone-receptor complex binds DNA 5. New mRNA 6. Protein 7. Response

Question 36

What did Lefkowitz & Kobilka study?

Answer 36

G protein-coupled receptors (GPCRs) and how cells sense their environment.

Question 37

Why are GPCRs important?

Answer 37

They play a key role in cell signaling and are targets for nearly half of all drugs.