Chapter 20: Endocrine System

Question 1

Define endocrine system.

Answer 1

A system involving glands and hormones (that are released into the blood stream) to help maintain homeostasis in the body.

Question 2

Define endocrinology.

Answer 2

The study of the structural components of the endocrine system, the hormones they produce, and the effects of those hormones on target organs.

Question 3

List and describe the functions of the endocrine system. (3)

Answer 3

1. Work with the nervous system to maintain homeostasis.
2. Regulate certain body functions.
3. Use hormones rather than nerve impulses

Question 4

Discuss the characteristics of endocrine glands and list some examples.

Answer 4

1. Exocrine Glands
   - DUCTS: secretions released into ducts opening onto an epithelial surface
2. Endocrine glands
   - DUCTLESS: organs that secrete their molecules directly into the bloodstream
   - Located in highly vascularized areas to ensure that their products enter the blood stream immediately

Major Endocrine Glands: 
Pituitary Gland
Pineal Gland
Thyroid Gland
Parathyroid Glands
Adrenal Glands

Question 5

Identify similarities and differences between the endocrine system and the nervous system. Also, discuss how they interact.

Answer 5

Endocrine System (ES) Vs Nervous System (NS)

Communication:

• ES: secretes hormones into the blood and they are carried throughout the body to their target organs
• NS: uses nerve impulses that signal neurotransmitter released from a neuron into a synaptic cleft

Target of stimulation:

• ES: any cell in the body with a receptor for the hormone
• NS: other neurons, muscle cells, and gland cells

Response time:

• ES: Slow rxn time; seconds/min/hrs
• NS: Fast run time; Milliseconds/Seconds

Effect of Stimulation:

• ES: Causes metabolic changes in target cells
• NS: Causes stimulation/inhibition of another neuron; contraction/relaxation in muscles

Range of Effect

• ES: Widespread bodily effects
• NS: Localized, specific effects on the body

Duration of Response

• ES: Long-lasting; min/days/weeks; may continue after stimulus is removed
• NS: Short-term; milliseconds; terminates with stimulus is removed

Question 6

Discuss what hormones are and how they effect target organs and cells.

Answer 6

• Molecules that have an effect on specific organs

- Only cells/tissue/organs with specific receptors for the hormone respond to that hormone

Question 7

List and discuss the 2 different types of feedback loops.

Answer 7

1. Negative Feedback Loop:
   - Stimulus starts a process and eventually either the hormone that is secreted or a product of its effects causes the process to slow down to turn off
   - ie. Regulation of blood glucose in the body
2. Positive Feedback Loop:
   - Stimulus occurs and accelerates a process, either by ensuring that the pathway continues to run or speeds up its activities
   - ie. breast feeding

Question 8

Explain the relationship between the hypothalamus and the endocrine system

Answer 8

Hypothalamus is the master control center of the endocrine system and oversees most endocrine activity in 3 main ways:

1. Cells in hypothalamus secrete hormones to act on pituitary gland causing it to secrete regulatory hormones into the blood stream
2. Hypothalamus produces 2 hormones that are transported to and stored in pituitary
3. Direct stimulation of adrenal gland - sympathetic response

Question 9

Identify the location and main secretion and major effects of the:
Pituitary Gland

Answer 9

• Inferior to hypothalamus, in sellae turcica
• Releases growth hormone (GH), hormones that act on the gonads (FSH, LH), a hormone that acts on the thyroid (TSH), one that acts on the mammary glands to stimulate milk production, a hormone that acts on the adrenal gland

Question 10

Identify the location and main secretion and major effects of the:
Thyroid Gland

Answer 10

• Inferior to the thyroid cartilage of the larynx, butterfly shape/2 lobes
• stimulated follicular cells of the thyroid gland release a hormone that stimulates target cells to respond to a stimulus

Question 11

Identify the location and main secretion and major effects of the:
Parathyroid Glands

Answer 11

• on posterior surface of thyroid gland
• contain chief cells and oxyphil cells
• contain a hormone that stimulates osteoclasts to reabsorb bone and release Ca
• promotes Ca absorption in small intestines and prevents loss of Ca when making urine

Question 12

Identify the location and main secretion and major effects of the:
Adrenal Glands

Answer 12

• superior surface of the kidneys like hats
• ## secrete different types of hormones; corticosteriods that regulate salt, sugar, and sex

Question 13

Identify the location and main secretion and major effects of the:
Pancreas

Answer 13

• posterior to stomach, between duodenum and spleen
• produces pancreatic juice that aides in digestion
• secretes glucagon when blood sugar is low
• secretes insulin when blood sugar is high
• pancreatic hormones provide orderly uptake and processing of nutrients

Question 14

Identify the location and main secretion and major effects of the:
Pineal gland

Answer 14

• posterior region of the epithalamus
• secretes melatonin to help regulate sleep/wake cycles
• decreases in size as we age

Question 15

Identify the location and main secretion and major effects of the:
Thymus

Answer 15

• superior to the heart, posterior to the sternum
• functions associated with the lymphatic system to regulate and maintain body immunity
• secrete hormones that stimulate production and maturation of T-lymphocytes

Question 16

Identify endocrine functions and hormones of:

Kidneys, Heart, GI tract, Gonads

Answer 16

• all secrete their own hormones
• regulate RBC levels in blood, RBC production, blood vol, BP
• Digestive activities
• Sexual maturation and activity

Question 17

Identify common illnesses related to dysfunction of the endocrine structures

Answer 17

Diabetes:
Type I: Beta Cells don’t function properly (secretion of insulin)

Type II: Insulin receptors don’t function properly (effected by lifestyle and can be “fixed” by lifestyle changes)