Homeostasis

Question 1

What are the four tissue types of the body?

Answer 1

The four tissue types of the body are:

• Epithelial: Protection, absorption, secretion
• Muscle: Contraction and movement
• Nervous: Sensory and response functions
• Connective: Supportive (e.g. blood, bone, ligaments, tendons, cartilage, with scattered cells in an extracellular matrix)

Question 2

What are the four main epithelial types?

Answer 2

The four main epithelial types are:

• cuboidal
• simple columnar
• simple squamous
• stratified squamous

Question 3

Describe cuboidal epithelial tissue

Answer 3

Cuboidal epithelial tissue:

- Many glands and kidney tubules, think secretion

Question 4

Describe simple columnar epithelial tissue

Answer 4

Simple columnar epithelial tissue:

• Much of the GI tract
• Protection, lubrication, absorption, and even secretion

Question 5

Describe simple squamous epithelial tissue

Answer 5

Simple squamous epithelial tissue:

• lines blood vessels, alveoli, loop of Henle, pleural, and peritoneal cavities
• For exchange of materials. Thin and leaky

Question 6

Describe stratified squamous epithelial tissue

Answer 6

Stratified squamous epithelial tissue:

• epidermis, esophagus, vagina, anus
• Regenerates rapidly
• Found on tissues subject to abrasion

Question 7

What are the three different types of connective tissue fibers?

Answer 7

The three different types of connective tissue fibers are:

• Collagen
• Elastic Fibers
• Reticular Fibers

Question 8

What is collagen?

Answer 8

Collagen represents a family of white fiber proteins very rich in glycine

• It has a triple helix (tropocollagen)
• fibrous and hydrophobic
• Hydrogen bonding and cross linking occurs through a series of complex reactions between lysine and histidine residues
• In bone and teeth, collagen is embedded in hydroxyapatite, an inorganic calcium phosphate molecule that gives it strength
• Tendons, dentin, dermis, ligaments, and organs all contain collagen

Question 9

What special amino acids are found in collagen?

Answer 9

Hydroxyglycine and hydroxyproline are seen in the polypeptide chain of collagen allowing for the sharp twists of the helixes.
- These are both formed by the post-translational addition of an OH group that helps with hydrogen bonding.

Question 10

Describe why we see so many collagen diseases

Answer 10

Several genes are involved with collagen biosynthesis; thus a large number of diseases could result from a defect in collagen synthesis. (Scurvy, Ehlers-Danlos, and osteogenesis imperfecta are some examples)

Question 11

Describe Vitamin C’s role in collagen development

Answer 11

Vitamin C is needed for proper collagen synthesis, and lack of this vitamin will give rise to scurvy. It helps convert proline to hydroxyproline, thus with a lack of vitamin C, the tropocollagen molecules cannot form a stable helix.(less hydrogen bonding can occur)

Question 12

What is Ehlers-Danlos syndrome?

Answer 12

Ehlers-Danlos syndrome:

- we see hyper-extensive skin and hyper-mobile joints which leads to easy injury

Question 13

What are elastic fibers?

Answer 13

Elastic fibers

• Unlike collagen, these fibers are very accommodating and can be stretched quite far without breaking. They have the ability to recoil.
• Made by fibroblasts and smooth muscle cells in arteries
• Allows our skin to return to its original position when pinched
• highly abundant in blood vessels such as the aorta
• found in the bladder, lungs, veins, ligaments, cartilage, and skin
• Easily hydrolyzed by the pancreatic enzyme elastase

Question 14

What are reticular fibers?

Answer 14

Reticular fibers:

• Give support to individual cells
• Very thin branched fibers made of collagen
• They stain black because they react with silver salts
• Found in high % in: Smooth muscle, lymph nodes, spleen, red bone marrow

Question 15

What do connective tissue include?

Answer 15

Connective tissues include:

• Blood
• Bone
• Cartilage
• Adipose
• Tendons
• Ligaments

Question 16

What are fibroblast cells?

Answer 16

Fibroblast cells synthesize proteins like elastin and collagen, glycoproteins, proteoglycans, and glycoproteins of the cellular matrix

• Also produce growth factors that influence cell growth and differentiation
• In adults, it undergoes very little mitosis, except when more fibroblasts are needed
• When a tissue is destroyed by trauma or pathology, the spaces are filled with connective tissue by the fibroblast. What we call a scar.
• They are the most abundant cell in connective tissue.
• They make almost all of the extracellular matrix components, providing support, but also guiding division, growth, and cell development
• They also make fibronectin, that connects the extracellular matrix to cell surface receptor proteins such as integrins. Fibronectin also migrates to clots to aid in repairs.

Question 17

What two body systems are involved with control and coordination

Answer 17

The two body systems involved with control and coordination are:

• Endocrine: Hormones secreted directly into the bloodstream, but targets specific cells that have the proper receptors
• Nervous: transmits information along a specific communication line called a neuron.

Question 18

How do the endocrine and nervous system differ?

Answer 18

The nervous system and endocrine system differ in these ways:

• Speed and duration:
• Nervous system fast and lasts for a brief period of time
• Endocrine system slow and can last for hours
• Hormone or nerve impulse signal
• Transmission

Both work to establish homeostasis.

Question 19

What is thermoregulation?

Answer 19

Thermoregulation is the process by which organisms control their body heat in response to the external environment.
- Can be endothermic or ectothermic

Question 20

What is acclimatization

Answer 20

Acclimatization is a physiological adjustment to changes in the external environment.

Question 21

What are endotherms?

Answer 21

Endotherms:

• Are warmed mainly by metabolism
• Commonly called “warm-blooded” but this term has been dropped
• Birds and Mammals
• Cells usually have more mitochondria
• Usually require more food due to their higher metabolism

Question 22

What are ectotherms?

Answer 22

Ectotherms:

• They are warmed mainly by external sources in their environment
• Commonly called “cold-blooded” but this is not really correct. Their blood temperature varies with the ambient temperature
• Amphibians, reptiles, many fish, and most invertebrates
• Many reptiles regulate their body temperature by basking in the sun or relaxing in the shade
• Because their heat source is mainly from the environment, they consume less food
• Can tolerate temperature changes.

Question 23

What are Homeotherms?

Answer 23

Homeotherms are organisms that maintain a constant body temperature.
- Both ectotherms and endotherms can be homeotherms, but mostly endotherms are.

Question 24

What are Poikilotherms?

Answer 24

Poikilotherms are organisms whose body temperature varies with the environment
- Both ectotherms and endotherms can be poikilotherms, but mostly ectotherms are.

Question 25

What does human body temperature depend on?

Answer 25

Human body temperature depends on many factors such as:

• time of day
• exertion
• sex
• age
• emotional state

Question 26

What physiological responses occur in humans when hot and cold?

Answer 26

When humans are hot:

• They sweat. The evaporation of the sweat causes the body to cool down
• Vasodilation of blood vessels at the skin allow more blood to flow there and release heat into the environment

When humans are cold:

• They shiver. The shiver is a series of involuntary muscle contractions that generates heat as the muscles start to work and raise our metabolic rate
• Vasoconstriction of blood vessels at the skin allow more blood to stay within the body preventing heat loss to the environment.

Question 27

How does endotherm body size correlate to metabolic rate?

Answer 27

Metabolic rate in endotherms is correlated to body size in the following way:

• The larger the organism, the lower its metabolic rate.
• The smaller the organism the faster its metabolic rate.
• As we get larger, our surface area to volume ratio decreases, so there is less heat lost to the environment.
• As we get smaller, the surface area increases causing more heat to be lost to the environment and an increased need for metabolism to make up the heat difference.
• Smaller animals have a higher breathing rate, heart rate, and blood volume relative to its size, and therefore tend to have a higher per-gram basal metabolic rate than larger animals.
• This theory is in debate, however, as we see the same inverse relationship of size and metabolic rate with ectotherms who don’t use metabolism to regulate body heat.

Question 28

What is hibernation?

Answer 28

Hibernation is when an animal allows its body temperature and metabolism to decrease for long periods of time.

• These animals survive on the metabolic reserves that it accumulated before entering hibernation
• Heart rate, body temperature, and O2 consumption may fall dramatically
• Seen in:
• Bears
• Hummingbirds
• Turtles
• Groundhogs
• Bumblebees
• Bats
• Ladybugs
• Skunks