Kaplan Ch. 10 - Homeostasis

Question 1

Describe the path that blood follows in the kidneys.

Answer 1

Rental artery —> afferent arterioles —> glomeruli —> efferent arterioles (vasa recta) —> Loop of Henle —> renal vein

Question 2

What is the name for the muscle lining the bladder?

Under control of ____ NS.

Answer 2

Detrusor muscle

Parasympathetic

Question 3

Describe the two sphincters involved in urination.

Answer 3

Internal urethral sphincter is smooth muscle, under autonomic control. When bladder is full, ParaNS signals to detrusor muscle to contract, this relaxing bladder and causing internal urethral sphincter to relax. Then, the external urethral sphincter (skeletal muscle, under somatic control) must also relax. This is up to individual (holding in one’s pee).

Question 4

What are the primary functions of the kidneys?

Answer 4

Regulate blood volume and osmolarity

Question 5

Describe the process of filtration

Answer 5

Movement of solutes from blood to filtrate at Bowman’s capsule

Blood from the afferent arterioles enter the glomeruli. There, fluid and some molecules / ions (filtrate) flow out of the afferent capillaries and into Bowman’s space because the hydrostatic pressure in the capillary is much greater than the hydrostatic and oncotic pressure in Bowman’s space. Cells and large molecules are not able to pass into Bowman’s space because of the pore size of the filter. Blood that remains passes into the efferent arterioles which empty to the vasa recta.

Question 6

Describe the process of secretion.

Answer 6

Movement of solutes from blood to filtrate anywhere besides Bowman’s capsule

Nephrons secrete salts, acids, bases and urea directly into the tubule by either active or passive transport.

Question 7

Describe the process of reabsorption.

Answer 7

Movement of solutes from filtrate to blood

The body can reabsorb some compounds that it filters or secretes out of the blood, such as glucose, amino acids, and vitamins.

Question 8

The major waste products excreted in the urine can be remembered using the mnemonic “Dump the HUNK”. What are the molecules that associate with HUNK?

Answer 8

H = H+ ions
U = urea
N = NH3 (ammonia)
K = K+ (potassium)

Question 9

What happens in the proximal convoluted tubule?

Answer 9

Majority of reabsorption of amino acids, glucose, water soluble vitamins, salts and water. These solutes enter the interstitium (connective tissue around nephron) and are returned to blood stream via bass recta. H+, urea, NH3 and K+ are also secreted from interstitium to filtrate here.

Question 10

Descending limb of the loop of henle:

1) what is this permeable to?
2) as this travels deeper into the medulla of the kidney, what happens?

Answer 10

1) only water

2) the osmolarity of the interstitium increases so water flows out of the filtrate and into the interstitium

Question 11

How do the vasa recta and nephron create a countercurrent multiplier system?

Answer 11

Because the flow of filtrate through the nephron is opposite the flow of blood through the vasa recta.

Question 12

Ascending limb of loop of henle:

1) only permeable to _____?
2) what exchange happens here?

Answer 12

1) salts
2) at deep parts of medulla (beginning of ascending limb) the concentration of solutes is high, so as the limb ascends the concentration decreases, leading to increased removal of salts from filtrate as limb ascends to cortex

Question 13

What happens at the junction of the inner and outer medulla?

Answer 13

The loop of henle gets larger and is called the diluting segment. Here the cells of the ascending limb are larger and have mitochondria to transport Na+ and Cl- via active transport out of the filtrate and into the interstitium. This can result in excess water trapped in the filtrate and is the only part of the nephron that can produce urine that is less concentrated than the blood.

Question 14

What happens in the distal convoluted tubule?

What hormone is this section sensitive to?

Answer 14

Sodium is reabsorbed and water along with it.

Responds to aldosterone

Question 15

What happens in the collecting duct?

What hormones is this section sensitive to?

Answer 15

Water is reabsorbed from the filtrate to the interstitium. Eventually makes its way from interstitium to vasa recta and to blood.

Responds to ADH and aldosterone by changing permeability (hormones increase permeability so more water leaves filtrate to interstitium)

Question 16

What are the three major layers of the skin?

Answer 16

The hypodermics (bottom), dermis, and epidermis.

Question 17

What are the layers of the epidermis?
Mnemonic (superficial to deep) Come, Lets Get Sun Burned

What are the cells / structures in each layer?

Answer 17

Stratum Corneum - contains flattened keratinocytes that form barrier

Stratum Lucidum - transparent, only present in thick hairless regions of skin

Stratum Granulosum - keratinocytes die and lose nuclei

Stratum Spinosum - keratinocytes become connected to one another, layer contains langerhans cells, which are macrophages that can participate in MHC presentation to T cells to activate immune system

Stratum Basale - contains stem cells that proliferate into keratinocytes, which produce keratin. Also contains melanocytes, which produce melanin pigment to protect skin from DNA damage from UV radiation. Once melanin is produced keratinocytes uptake the pigment

Question 18

How is the skin involved in thermoregulation?

Answer 18

1) sweating (secrete water and ions onto skin, water evaporates which absorbs heat from skin)
2) arrector pili muscles contract to raise hair fibers and trap warm air near surface of skin
3) shivering (rapid muscle contraction that generates large amounts of thermal energy)

Question 19

What is the function of the dermis?

Answer 19

The dermis contains sensory receptors

Merkel cells are responsible for deep pressure and texture sensation

Meissner’s corpuscles respond to light touch

Pacinian corpuscles respond to deep pressure and vibration

Ruffini endings respond to stretch