Endocrine System Flashcards by Sam h

Describe Cell Signaling

signaling cell sends a signal (usually a chemical)

target cell receives the signal and responds to it

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Describe two systems of Long Distance Signaling

Endocrine System: chemical messenger (hormone) transported by circulatory system
Nervous System: electrical signal travels along a neuron and chemical messenger (neurotransmitter) is released

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What are 4 types of cell signaling? Describe them

Direct cell signaling: 2 cells in direct contact communicate through gap junctions where chemical messenger goes from one to the other
2a. Autocrine: chemical messenger leaves cell and binds to receptor on itself
2b. Paracrine signaling: chemical messenger binds to receptor on nearby cell (no circ. system involved)
Endocrine signaling: signaling cell dumps hormone into cir. system (long or short distance) then binds to receptor on receiving cell
Neural signaling: electrical signal leads to release of neurotransmitter that binds to receptor on target cell

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Describe the 3 regulatory components of cell signaling

Sensor: detects levels of regulated variable -> sends signal to integrating center
Integrating center: evaluates input from sensor -> sends signal to effector
Effector: target tissue that responds to signal from integrating center

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What is a Set Point?

The value of the variable that the body is trying to maintain

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What is the difference between Positive and Negative Feedback Loops?

Positive: output of effector amplifies variable AWAY from the set point
Negative: output of effector brings variable BACK to the set point

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Explain what happens to the thermoregulatory set point during a fever

fever involves an increase in the body’s thermoregulatory set point -> person feels cold because body perceives a state of hypothermia -> fever breaks and set point returns back down so person sweats until body temp is lowered

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Describe a Direct Feedback Loop

stimulus -> endocrine gland -> target organ -> response

- no integrating center; quick

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Describe a First-order Feedback Loop

stimulus -> integrating center -> target organ -> response

- no endocrine glands

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Describe a Second-order Feedback Loop

stimulus -> sense organ -> integrating center -> endocrine gland -> target organ -> response
- 1 endocrine gland + integrating center

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Describe a Third-order Feedback Loop

stimulus -> sense organ -> integrating center -> endocrine gland 1 -> endocrine gland 2 -> target organ -> response
- 2 endocrine glands + integrating center

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Describe the Direct Feedback Loop of atrial natriuretic peptide (ANP)

Stimulus = increased blood pressure
Endocrine gland = heart (atrium) - secretes ANP
Target organ = blood vessels in kidneys
Response = lower blood pressure

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What is Hypoglycemia? What problem does it cause?

blood glucose too low

brain cannot function

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What is Hyperglycemia? What problem does it cause?

blood glucose too high

osmotic balance of blood disturbed

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What does Insulin do?

lower blood glucose levels

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What does Glucagon do?

raise blood glucose levels

Where are Alpha and beta cells found? What do they do?

Islet of Langerhans (in pancreas)
Alpha cells release glucagon
Beta cells release insulin

Why are Insulin and Glucagon considered an Antagonistic pairing?

they are hormones that have opposing effects

Describe the Antagonistic regulation of blood glucose

increased plasma glucose -> beta cells of pancreas increase insulin secretion -> target tissues -> increase glucose uptake -> decrease plasma glucose
(simultaneously)
increased plasma glucose -> alpha cells decrease glucagon secretion -> target tissues -> decrease glucose release -> decrease plasma glucose

What type of feedback loop are insulin and glucagon involved in?

Direct feedback loop

What are 3 pathways that regulate insulin secretion?

Direct feedback loop: increase blood glucose -> pancreas secretes insulin
(2) Direct feedback loops: Glucose receptors in digestive tract release CCK -> pancreas secretes insulin
Second-order feedback loop: stretch receptors in digestive tract -> integrating center (Enteric Nervous System) -> pancreas secretes insulin

Describe Type 1 Diabetes

juvenile onset

body does not produce enough insuliin

Describe Type 2 Diabetes

adult onset

target cells do not fully respond to insulin

Why does obesity increase the risk for Type 2 Diabetes?

adipocytes release a hormone (resistin) which likely down-regulates the insulin pathway

Why does a defect in the insulin pathway vary from person to person?

because so many proteins are involved in insulin signal transduction

Why is it difficult to define Hypoglycemia? What is the first sign of being Hypoglycemic?

there is a range of blood sugar levels that could result in a reaction the first sign is becoming completely incoherent

What is Hyperinsulinism? What are some metabolic diseases that can cause it?

Always being Hypoglycemic - Autosomal mutations - Beckwith-Wiedemann Syndrom (overgrowth disorder) - Insulin reaction when too much insulin given to a diabetic

How is hormone diversity in vertebrates characterized?

evolutionary changes in the way tissues respond to a hormone (rather than a change in the hormone molecules)

Give 2 examples of hormones that have the same effect in different animals

1. human growth hormone: increase rate of growth in fish | 2. estrogen (from pregnant mares): used in post-menopausal women

Give an example of a hormone that has a different effect in different animals

Prolactin: - stimulates milk production in mammals - inhibits metamorphosis & promotes growth in amphibians - regulates water balance in fish

What is the key vehicle for the endocrine system? Give examples of why they are considered diverse organic chemical messengers?

Hormones | ex. proteins, glycoproteins, steroids, biogenic amines, small peptides

What are many hormones produced and secreted by?

produced by hypothalamus | secreted by pituitary

Where can Hormone Receptors be? Where can Hormone Signaling occur?

- on surface of target tissue, within cytosol, in target cell's nucleus - endocrine, paracrine, autocrine pathways

Describe how Peptide Hormones are synthesized, stored, and secreted. Give some examples of peptide hormones

- synthesized on rough ER (often as larger preprohormones) - stored in vesicle as prohormones (proteolytic enzymes in vesicle then cut the prohormone into active hormone) - secreted by exocytosis - ex. ANP, CCK, Prolactin

Where is the Pituitary gland (hypophysis) located? What 2 parts is it derived from?

at base of brain, resides within sella turcica (saddle-shaped cavity) from (1) oral ectoderm and (2) neural tissue

Describe the derivation of the Neural part of the pituitary gland. What two names are used to describe this part?

evagination from the floor of the diencephalon | Neurohypophysis = Posterior Pituitary

Describe the derivation of the Oral component of the pituitary gland. What two names are used to describe this part?

outpocketing of the ectoderm from the roof of the mouth | Adenohypophysis = Anterior Pituitary