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MCAT: Biology > Chapter 10: Homeostasis > Flashcards

Chapter 10: Homeostasis Flashcards

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1
Q

What four organs comprise the excretory system?

A
  • Kidneys
  • Ureters
  • Bladder
  • Urethra
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2
Q

What is the functional unit of the kidney? How many do they have?

A
  • The nephron

- 1 million

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3
Q

All of the nephrons eventually empty into the ______ ________, which narrows to form the _______.

A

renal pelvins

ureter

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4
Q

Urine travels through the _______ to the _________, out of the _______ to exit the body.

A

ureter
bladder
urethra

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5
Q

What are the two sub-structures of the kidney?

A
  • Cortex: outer layer

- Medulla: sits within the cortex

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6
Q

What is the renal hilum of the kidney?

A

Deep slit in the center of its medial surface

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7
Q

What is the widest part of the ureter called?

A

Renal pelvis

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8
Q

The renal artery, renal vein, and _______ enter and exit through the renal ______

A

ureter

hilum

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9
Q

What is a portal system?

A

Consists of two capillary beds in series through which blood must travel before returning to the heart

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10
Q

What are glomeruli?

A

The highly convoluted capillary tufts derived from afferent arterioles

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11
Q

What is the portal system of the kidney? Name the two capillary beds.

A
  • Blood from the renal artery flows into afferent arterioles, which form glomeruli in Bowman’s capsule (the first capillary bed)
  • Blood then flows through the efferent arteriole to the vasa recta, which surround the nephron (the second capillary bed), before leaving the kidney through the renal vein
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12
Q

The second capillary bed surround the ____________ and are known as vasa recta.

A

loop of Henle

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13
Q

Differentiate the two muscular sphincters of the detrusor muscle in the bladder.

A
  • Internal urethral sphincter consists of smooth muscle and is under involuntary (parasympathetic) control
  • External urethral sphincter consists of skeletal muscle and is under voluntary control
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14
Q

What is the micturition reflex?

A
  • When the bladder is full, stretch receptors tell the nervous system that it needs emptying
  • Causes parasympathetic neurons to fire, and the detrusor muscle contracts
  • Also causes the internal sphincter to relax
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15
Q

What happens if blood volume is low and blood osmolarity is high in terms of urination?

A

Low-volume, highly concentrated urine

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16
Q

What are the three processes of the kidneys?

A
  • Filtration
  • Secretion
  • Reabsorption
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17
Q

What is filtration?

A

The movement of solutes from blood to filtrate at Bowman’s capsule

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18
Q

What is the direction and rate of filtration determined by?

A
  • Starling forces, which account for the hydrostatic and oncotic pressure differentials between the glomerulus and Bowman’s space
  • Hydrostatic > oncotic, so the net flow is the blood into the nephron
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19
Q

How does the filtrate differ from blood?

A

Similar in composition, but does not contain cells or proteins

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20
Q

What do blood cells and proteins found in urine indicate?

A

A health probe mat the level of the glomerulus

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21
Q

What is secretion?

A

The movement of solutes from blood to filtrate anywhere other than Bowman’s capsule

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22
Q

What do nephrons secrete during secretion? What type of transport is it?

A
  • Salts, acids, bases, and urea

- Active or passive transport

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23
Q

What is reabsorption?

A

Movement of solutes from filtrate to blood

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24
Q

What compounds are almost always reabsorbed?

A

Glucose, amino acids, vitamins

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25
Q

What hormones can alter the quantity of water reabsorbed within the kidney?

A

Antidiuretic hormone (ADH) and aldosterone

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26
Q

What are horizontal regions in the nephron focused on? Name them.

A
  • Identity of the particles in the urine

- Bownman’s capsule, proximal convoluted tubule, distal convoluted tubule

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27
Q

What are the vertical regions in the nephron focused on? Name them.

A
  • The volume and water concentration of the urine

- Loop of Henle and collecting duct

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28
Q

What is the mnemonic for the major waste products excreted in urine?

A
  • Dump the HUNK
  • H+
  • Urea
  • NH3
  • K+
29
Q

What is the function of the proximal convoluted tubule?

A
  • Reabsorption of amino acids, glucose, water-soluble vitamins, and salts
  • Secretion of HUNK waste products
30
Q

What happens to solutes that enter the interstitium?

A

Picked up by the vasa recta and returned to the bloodstream for reuse within the body

31
Q

Where is the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and the collecting duct?

A
  • Proximal convoluted tubule: cortex
  • Loop of Henle: cortex, outer medulla, inner medulla
  • Distal convoluted tubule: cortex
  • Collecting duct: outer medulla
32
Q

What is the function of the descending limb of the loop of Henle?

A

Only permeable to water, reabsorption of water

33
Q

What is the countercurrent multiplier system of the vasa recta and nephron?

A
  • The flow of filtrate through the loop of Henle is in the opposite direction from the flow of blood through the vasa recta
  • The filtrate is constantly being exposed to hypertonic blood, which allows maximal reabsorption of water
34
Q

What is the function of the ascending limb of the loop of Henle?

A

Secretion of salts (Na+, Cl-)

35
Q

At the transition from the inner to outer medulla, the loop of Henle becomes thicker. What is this termed? Why does this occur?

A
  • Diluting segment
  • Because the cells lining the tube are larger, contain a larger amount of mitochondria, which allow for the reabsorption of sodium and chloride by active transport
36
Q

Which segment is the only portion of the nephron that can produce urine that is more dilute than blood? What is the function?

A
  • Diluting segment

- Provides a mechanism for eliminating excess water

37
Q

What does the distal convoluted tubule respond to? What is its function?

A
  • Aldosterone, which promotes sodium reabsorption
  • Reabsorption of sodium ions and water
  • Also, site of waste product secretion
38
Q

What does the collecting duct respond to? What is its function?

A
  • Aldosterone and antidiuretic hormone (ADH)

- Variable permeability, which allows reabsorption of the right amount of water depending on the body’s needs

39
Q

What is aldosterone?

A

Steroid hormone secreted by the adrenal cortex in response to decreased blood pressure

40
Q

What is the mechanism by which aldosterone is released from the adrenal cortex?

A
  • Decreased blood pressure stimulates the release of renin from juxtaglomerular cells in the kidney
  • Renin cleaves angiotensinogen, a liver protein, to form angiotensin I
  • Angiotensin-converting enzyme in the lungs converts it to angiotensin II, which promotes the release of aldosterone
41
Q

How does aldosterone work?

A

By altering the ability of the distal convoluted tubule and collecting duct to reabsorb sodium, which increases the reabsorption of water

42
Q

What is ADH?

A

Peptide hormone synthesized by the hypothalamus and released by the posterior pituitary in response to high blood osmolarity

43
Q

How does ADH work?

A

Directly alters the permeability of the collecting duct, allowing more water to be reabsorbed by making the cell junctions of the duct leaky

44
Q

What are the effects of alcohol and caffeine on ADH?

A

Both inhibit ADH release and lead to the frequent excretion of dilute urine

45
Q

How do the kidneys affect acid-base balance?

A
  • When blood pH is low, they excrete more H+ and increase reabsorption of bicarbonate, increasing pH
  • When blood pH is high, they excrete more bicarbonate and increase reabsorption of H+
46
Q

List the vessels in the renal vascular pathway, starting from the renal artery and ending at the renal vein.

A

Renal artery, afferent arteriole, glomerulus, efferent arteriole, vasa recta, renal vein

47
Q

Starting from the deepest layer, what are the four layers of the skin?

A
  • Hypodermis (subcutaneous layer)
  • Dermis
  • Epidermis
48
Q

The epidermis is subdivided into layers called ______.

A

strata

49
Q

What is the mnemonic to remember the layers of the skin (superficial to deep)?

A
  • Come, Let’s Get Sun Burned
  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
50
Q

What are the stem cells of the stratum basale responsible for?

A

For the proliferation of keratinocytes, the predominant cells of the skin that produce keratin

51
Q

What happens in the stratum spinosum?

A

Cells become connected to each other (Langerhans cells)

52
Q

What happens in the stratum granulosum?

A

The keratinocytes die and lose their nuclei

53
Q

Where is the stratum lucidum only present?

A

In thick, hairless skin, such as the skin on the sole of the foot or the palms, and is nearly transparent

54
Q

What happens in the stratum corneum?

A

Dozens of layers of flattened keratinocytes, forming a barrier that prevents invasion by pathogens and that helps to prevent loss of fluids and salt

55
Q

What are the main cells in the epidermis?

A

Keratinocytes

56
Q

How do calluses form?

A

From excessive keratin deposition in areas of repeated strain due to friction

57
Q

Where are melanocytes found? What are they derived from?

A
  • Derived from neural crest cells

- Found in the stratum basale

58
Q

What is the function of melanocytes?

A

Produce melanin, a pigment that serves to protect the skin from DNA damage caused by UV radiation

59
Q

Where do Langerhans cells reside?

A

Special macrophages that reside within stratum spinosum

60
Q

What are the two layers to the dermis?

A
  • Papillary layer (upper): loose connective tissue

- Reticular layer (lower): dense

61
Q

Where do sweat glands, blood vessels, sensory cells and hair follicles originate?

A

In the dermis

62
Q

What are Merkel discs?

A
  • Sensory cells present at the epidermal-dermal junction

- Connected to sensory neurons and are responsible for deep pressure and texture sensation within the skin

63
Q

What do Meissner’s corpuscles, Ruffini endings, and Pacinian corpuscles respond to?

A
  • Meissner’s corpuscles respond to light touch
  • Ruffini endings respond to stretch
  • Pacinian corpuscles respond to deep pressure and vibration
64
Q

What is the function of the hypodermis?

A
  • Layer of connective tissue that connects the skin to the rest of the body
  • Contains fat and connective tissue
65
Q

What is sweating controlled by?

A
  • Automatic nervous system
  • Postganglionic sympathetic neurons that utilize acetylcholine innervate sweat glands and promote the secretion of water with certain ions onto the skin
66
Q

What happens in cold conditions?

A

Arrector pili muscles contract, causingthe hairs of the skin to stand up on end (piloerection)

67
Q

How can the body cool itself?

A

Sweating and vasodilatation

68
Q

How can the body warm itself?

A

Vasoconstriction, piloerection, and shivering

MCAT: Biology (12 decks)

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