Endocrine Systems

Question 1

What is the primary function of the endocrine system?

Answer 1

The endocrine system regulates homeostasis by slow, long-lasting chemical signaling through hormones released from glands that act on target organs via the circulatory system.

Question 2

What are the key differences between endocrine and exocrine glands?

Answer 2

Endocrine glands secrete hormones into the blood to act on distant target organs (e.g., thyroid hormone).
Exocrine glands secrete substances through ducts to the skin or external body cavities (e.g., sweat or mucous).

Question 3

Endocrine glands secrete hormones into the blood to act on distant target organs (e.g., thyroid hormone).
Exocrine glands secrete substances through ducts to the skin or external body cavities (e.g., sweat or mucous).

Answer 3

The endocrine system senses internal changes, integrates sensory information, and responds by releasing hormones to act on target organs, regulating physiological responses.

Question 4

What is the role of the hypothalamus in the endocrine system?

Answer 4

The hypothalamus integrates sensory input and regulates hormone release from the pituitary gland and other glands to maintain homeostasis and coordinate physiological responses (e.g., thirst, hunger).

Question 4

How are hormones classified based on their function?

Answer 4

Tropic hormones regulate the production or secretion of another hormone in a gland (e.g., thyroid-stimulating hormone).
Non-tropic hormones have a direct effect on target organs (e.g., thyroid hormone).

Question 5

How are hormones classified based on their structure?

Answer 5

Peptides: Most hormones are amino acids.
Amines: Derived from tyrosine (e.g., catecholamines).
Steroids: Derived from cholesterol (e.g., gonadal hormones).

Question 6

What is the process of synthesizing, storing, and releasing peptide hormones?

Answer 6

Preprohormone is translated and packaged into vesicles.
It is processed into prohormone → hormone.
Hormone is stored in vesicles.
The vesicles fuse with the plasma membrane to release the hormone into the blood.

Question 7

How are steroid hormones synthesized and released?

Answer 7

Steroid hormones are synthesized from cholesterol, diffuse across the plasma membrane into the blood (since they are lipophilic), and are not packaged into vesicles.

Question 8

What is the difference between water-soluble and lipid-soluble hormones in terms of their transport?

Answer 8

Water-soluble hormones (e.g., peptides, catecholamines) are free in the blood or bind to plasma proteins.
Lipid-soluble hormones (e.g., steroids, thyroid hormone) are bound to plasma proteins

Question 9

How do hormones produce their effects on target organs?

Answer 9

Hormones bind to specific receptors on target cells, which triggers a response inside the cell, often leading to changes in enzyme activity or protein synthesis.

Question 10

What are the two types of hormone receptors?

Answer 10

Membrane receptors (e.g., GPCR, kinase-linked) for peptides, catecholamines, and some steroids.
Internal receptors (e.g., nuclear receptors) for most steroids and thyroid hormones.

Question 11

What is the difference between permissiveness, synergism, and antagonism in hormone interactions?

Answer 11

Permissiveness: One hormone is required for another hormone to be effective (e.g., thyroid hormone and adrenaline).
Synergism: Combined effect of two hormones is greater than their individual effects (e.g., FSH and testosterone on sperm).
Antagonism: One hormone reduces the receptor levels for another hormone (e.g., progesterone reducing estrogen receptors).

Question 12

What is the role of negative feedback in hormone regulation?

Answer 12

Negative feedback helps maintain hormone levels within a narrow range by counteracting deviations from a set point (e.g., thyroid hormone regulation by TSH).

Question 13

How are hormone secretion levels influenced by external stimuli?

Answer 13

Neuroendocrine reflexes produce sudden increases in hormone secretion in response to internal or external stimuli, such as stress or childbirth (e.g., glucocorticoids or oxytocin).

Question 14

What are biological rhythms, and what are their types?

Answer 14

Biological rhythms are regular variations in physiology and behavior. Types include:

Circadian rhythms (daily variations).
Monthly rhythms (e.g., menstrual cycle).
Circannual rhythms (yearly variations like mating or hibernation).

Question 15

What is the role of the suprachiasmatic nucleus in regulating circadian rhythms?

Answer 15

The suprachiasmatic nucleus is the “master clock” in mammals, controlling the circadian rhythm by coordinating neuronal activity with light input from the retina and regulating melatonin production in the pineal gland.

Question 16

What are endocrine disrupting chemicals, and how do they affect animals?

Answer 16

Endocrine disrupting chemicals (EDCs) are substances that mimic or block the action of hormones, affecting physiological processes like sexual development, often through bioaccumulation in aquatic food webs.

Question 17

How do biological clocks interact with the external environment?

Answer 17

Biological clocks are influenced by external cues called zeitgebers, such as light, which help synchronize internal rhythms with environmental changes like the day-night cycle or seasonal shifts.