U3: C11: Homeostasis

Question 1

Homeostasis

Answer 1

Ability to maintain a constant internal environment despite a changing of external environment

Question 2

Kidneys use ___ & ___ to maintain the body’s ___& ___ balance.

Answer 2

selective permeability & osmolarity … water & salt

Question 3

Functional unit of Kidney is ____, name the 5 basic sections

http://mcat-review.org/nephron.gif

Answer 3

nephron

1. Bowman’s Capsule: glomerulus is inside and the fluid that makes it into PCT is called the filtrate.
2. proximal convoluted tubule: major reabsorption and secretion (reabsorption of glu, amino acids, vitamin, salts)
3. loope of henle: create osmotic gradient (top: low osmolarity, bottom: high osmolarity inside the tubule)
   a. descending limb: reabsorb water only
   b. ascending limb: reabsorb salts only
4. distal convolulted tubule: hormone controlled reabsorption and secretion, normally reabsorption of salts and water in same proportions, unless hormone Aldosterone present
5. collecting duct: concentrate urine using osmotic gradient

Question 4

Hormones involved in water and salt balance (include molecular type)

Answer 4

Aldosterone (steroid), ADH (peptide) Both cause reabsorption of water, they differ in their mechanisms.

Question 5

Aldosterone

1. molecular type
2. secreted by
3. as a response to..
4. function

Answer 5

1. steroid
2. Secreted by adrenal cortex, released into DCT
3. low blood volume, (aka low bp)
4. increase amt of reabsorbed salt in CD (directly) and thereby water (indirectly)
5. increase fluid in interstituim, which is then absorbed into the blood, increasing blood volume (aka inc. BP), also increases K+ excretion

Question 6

ADH

1. molecular type
2. secreted by
3. as a response to..
4. function

Answer 6

1. peptide (also known as vasopressin)
2. made in hypothalmus and stored in pituatary gland
3. blood osmolarity is high (high [salt] in blood)
4. increases permeabiliy in collecting ducts, allowing water to leak out into the interstial fluid. To dilute the blood osmolarity

Question 7

Liver (metabolisim)

Answer 7

1. Gluconeogensis: generating glucose from non-carbohydrate carbon substrates. (use Fats & Proteins) 2. Glycogenesis: generating glycogen from glucose

Question 8

Large Intestine (in homeostasis)

Answer 8

direcly secretes ions and metals into solid waste

Question 9

Thermoregulation

1. occurs where
2. How
3. When it is hot
4. When it is cold
5. regulated by what part of the body?

Answer 9

1. skin
2. vasodilation and vasoconstriction
3. vasodilation: surface vessels allow more blood to run close to the skin’s surface and heat is carried away by convection
4. vasoconstriction: surface vessels prevents convections by minimizing the amount of blood at the skin’s surface.
5. Hypothalmus

Question 10

Melanocytes

Answer 10

1. epidermis 2. secrete melanin = pigmentation & protection from uv damage

Question 11

___ & ___ are states of decreased metabolc activity and awarness. They serve to conserve resources in a time of scarcity.

Answer 11

hibernation (winter) and aestivation (summer)

Question 12

Skin layers x 3 and functions

Answer 12

1. epidermis: skin, prevents fluid and salt loss, and protection.
2. dermis: connective tissue, = blood and nerve supply, 2 layers contain glands and sense organs for touch and temperature
3. hypodermis: adipose tissue, absorbs schoc, and provides insulation, & connects skin to body

Question 13

Epidermis Layers (surface ->inward) x 5

List the cells x 3

Answer 13

Prefix = stratum for all 5

1. corneum: squamous cells
2. lucidum: lose nuclei before reaching corneum
3. granulosum
4. spinosum
5. basalis: proliferate
6. keratinocytes: produce keratin and make up the majority of the epidermis, these are what proliferate and then flatten as they reach the surface
7. Melanocytes: make melanin, skin pigment
8. Dendritic cells: (langerhans cell): phagocytes that eat pathogen and present foreign antigens to activate immune response.

Question 14

Dermis layers (surface inward) x 2

Answer 14

papillary layer (loose CT), reticular layer (dense CT)

-blood and nerve supply

Question 15

Livers main function (9)

Answer 15

1. detox 2. storage of vitamins and cofactors (Fe & B12) 3. destruction of old rbcs 4. synthesis of bile and various blood proteins 5. defense against antiens 6. metabolism (beta oxidation of FA to ketones, interconversion of carbohydrates, fats and amino acids) 7. stores glucose

Question 16

Cortex vs Medulla (adrenal gland, kidneys, brain)

Answer 16

Cortex: outside

1. adrenal gland: arise from mesoderm
2. kidney: glomerulus, procimal and distal convoluted tubules
3. brain: gray matter, nuclei (somas)

Medulla: inside

1. adrenal gland: arise from ectodermal
2. kidney: loope of henle & collecting duct
3. brain: white matter, mylinated axons

Question 17

Kidney structure

Answer 17

1. Cortex& medulla
2. Renal pelvis: where renal arteries, renal veins, and ureter enter and exit kidneys
3. Portal system: 2 sets of capillaries in series through which blood must travel before returnin to heat.
   
   1. Renal artery -> afferent arterioles -> glomerulus (capillaries) -> efferent arterioles -> vas recta -> renal vein

Question 18

Nephron

1. Sodium reabsorption/excretion locations
2. Water reabsorption/excretion

Answer 18

1. Sodium: activley reabsorbed in cortex bc isotonic bw tubule and interstium, and Na+ is transported against the [gradient]
2. Sodium: passively reabsorbed in thin segment of loop of henle in medulla (ascending limb) bc interstituuim is hypotonic compared to tubule, Na+ is transported with the [gradient]
3. Water is reabsorbed via osmosis, following the salt [gradient]
   - PCT, descending limb of loop of henle, DCT, CD
   - CD depends on hormones adosterone and ADH

Question 19

What is reabsorption and excretion?

Answer 19

* reabsorption: taken out of tubule into interstitium, and then reabsorped into the blood.

* excretion: everything that is not reabsorbed

Question 20

What does filtrate contain?

What does urine contain, and not contain?

Excretion pathway?

Answer 20

1. Filtrate contains almost everything that blood does except for whole cells and proteins, bc Bowman Capsule filters via size.
2. Urea, Uric acid, excess ions. Urine should not contain glucose, blood, or proteins
3. CDs -> renal pelvis -> ureter -> bladder -> urethra

Question 22

In a normal functioning nephron, is the urine hypertonic or hypotonic compared to blood?

Answer 22

normally hypertonic (more salts in tubule than blood)