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MCAT BIO my flashcards > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

Functions of the excretory system

A

The regulation of blood pressure, blood osmolarity, acid-base balance, and removal of nitrogenous wastes. –> kidney plays essential role

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2
Q

Parts of the excretory system

A

Kidneys, ureters, bladder, and urethra

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3
Q

Cortex

A

The kidney’s outermost layer

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4
Q

Medulla

A

Part of the kidney that sits within cortex

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5
Q

Hilum

A

A deep slit in the center of the liver’s medial surface

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6
Q

Renal pelvis

A

Widest part of the ureter; spans almost the entire width of the renal hilum

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7
Q

Describe the kidney’s portal system

A

Renal artery branches out, passes through the medulla, and enters the cortex as afferent arterioles. Highly convoluted capillary tufts derived from these afferent arterioles are known as glomeruli. After blood passes through a glomerulus, the efferent arterioles then form a second capillary bed. The capillaries surround the loop of Henle and are known as vasa recta.

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8
Q

Bowman’s capsule

A

A cuplike structure located around the glomerulus.

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9
Q

What are the parts of the long tubule the Bowman’s capsule leads to

A

The proximal convoluted tubule, descending and ascending limbs of Loop of Henle, distal convoluted tubule, and collecting duct.

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10
Q

Detrusor muscle

A

Muscular lining of bladder:parasympathetic activity causes the detrusor muscle to contract

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11
Q

Internal urethral sphincter

A

Consists of smooth muscle, and is contracted in its normal state. Made of smooth muscle and is under involuntary control

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12
Q

External urethral sphincter

A

Consists of skeletal muscle and is under voluntary control

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13
Q

What happens when the bladder is full/micturition reflex

A

Stretch receptors convey to the nervous system that the bladder requires emptying –> causes parasympathetic neurons to fire, and the detrusor muscle contracts –> in turn causes internal sphincter to relax.

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14
Q

3 broad different kidney process kidney function can be divided into

A

Filtration, secretion, and reabsorption

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15
Q

Filtration

A

The nephron’s first function: approximately 20 percent of the blood that passes through the glomerulus is filtered as fluid into Bowman’s space.

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16
Q

Starling forces in Bowman’s spaces

A

Governs movement of fluid in Bowman’s space.
Hydrostatic pressure in the glomerulus is significantly higher than that in Bowman’s space, which causes fluid to move into the nephron.
Osmolarity of blood is higher than that of Bowman’s space, resulting in pressure opposing the movement of fluid into the nephron.
NET: hydrostatic pressure much larger than oncotic pressure, so net flow is still from blood into nephron

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17
Q

What do nephrons secrete

A

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

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18
Q

How is nitrogen secreted

A

Ammonia (NH3) is a byproduct of the metabolism of nitrogen-containing compounds and, as a base, can disturb the pH of blood and cells.
liver converts ammonia to urea, a neutral compound, which travels to the kidney and is secreted into the nephron for excretion in the urine.

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19
Q

Reabsorption

A

When some compounds that are filtered or secreted may be taken back up for use. Certain substances are almost always reabsorbed, such as glucose, amino acids, and vitamins

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20
Q

summary of filtration, secretion, and reabsorption

A

Filtration: movement of solutes from blood to filtrate at Bowman’s capsule
Secretion: movement of solutes from blood to filtrate anywhere besides Bowman’s capsule
Reabsorption: movement of solutes from filtrate to blood

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21
Q

Proximal convoluted tubule (PCT)

A

First place after bowman’s capsule the filtrate enters. Amino acids, glucose, water-soluble vitamins, and the majority of salts are reabsorbed along with water. About 70% of filtrate reabsorbed here, but the filtrate remains isotonic to the interstitium, as other solutes and a large volume of water are also absorbed.
PCT is also the site of secretion for a number of waste products, including H+ ions, potassium ions, ammonia, and urea.

22
Q

What happens to solutes reabsorbed into the interstitium in the nephron

A

They are picked up by the vasa recta to be returned to the bloodstream for reuse within the body.

23
Q

Major waste products excreted in the urine

A

Dump the HUNK: H+, Urea, NH3, and K+

24
Q

Descending limb of the loop of Henle

A

Permeable only to water, and the medulla has an ever-increasing osmolarity as the descending limb travels deeper into it –> interstitial concentration favors outflow of water from descending limb, which is reabsorbed into the vasa recta.

25
Q

Countercurrent multiplier system

A

Together, the vasa recta and nephron –> means that the flow of filtrate through the loop of Henle is in the opposite direction from the flow of blood through the vasa recta.

26
Q

Descending limb of loop of Henle

A

Permeable to salts and impermeable to water.

Maximizes salt reabsorption by taking advantage of decreasing medullary osmolarity

27
Q

Diluting segment

A

Loop of Henle becomes thicker at the transition from inner to outer medulla –> cells lining the tube are larger –> contain mitochondria which allow reabsorption of sodium and chlordie by active transport.
The only portion of nephron that can produce urine that is more dilute than the blood.

28
Q

Distal convoluted tubule (DCT)

A

Responds to aldosterone, which promotes sodium reabsorption –> because sodium ions are osmotically active particles, water will follow the sodium, concentrating the urine and decreasing its volume.
Also a site of waste product secretion

29
Q

Collecting duct

A

Responsive to both aldosterone and antidiuretic hormone (ADH or vasopressin). Collecting duct almost always reabsorbs water, but amount is variable.

30
Q

Osmotic prssure

A

The “sucking” pressure that draws water into the vasculature caused by all dissolved particles.

31
Q

Oncotic pressure

A

The osmotic pressure that is attributable to dissolved proteins specifically.

32
Q

Bicarbonate buffer system and kidneys

A

The kidneys are able to selectively increase or decrease the secretion of hydrogen ions and bicarbonate. When blood pH is too low, the kidneys excrete more hydrogen ions and increase reabsorption of bicarbonate, resulting in higher pH. and vice versa.

33
Q

What are the layers of the skin starting from the deepest layer and working outward

A

Hypodermis (subcutaneous)
Dermis
Epidermis

34
Q

Layers of the epidermis from superficial to deep

A 
Come, Let's Get Sun Burned
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
35
Q

Stratum basale

A

Contains stem cells and is responsible for proliferation of keratinocytes, the predominant cells of the skin,t hat produce keratin.

36
Q

Stratum spinosum

A

The cells become connected to each other; also the site of Langerhan’s cells

37
Q

Stratum granulosum

A

Keratinocytes die and lose their nuclei

38
Q

Stratum lucidum

A

Only present in thick, hairless skin, such as the skin on the sole of the foot or the palms, and is nearly transparent.

39
Q

Stratum corneum

A

Contains up to several dozen layers of flattened keratinocytes, forming a barrier that prevents invasion by pathogens and that helps to prevent loss of fluids and salts.

40
Q

Calluses

A

Form from excessive keratin deposition in areas of repeated strain due to friction; they provide protection to avoid damage in the future

41
Q

Melanocytes

A

A cell type derived from neural crest cells and found in the stratum basale –> they produce melanin, a pigment that serves to protect the skin from DNA damage caused by ultraviolet radiation

42
Q

Langerhans cells

A

Special macrophages that reside within the stratum spinosum: capable of presenting antigens to T-cells in order to activate the immune system.

43
Q

Layers of the dermis

A

Papillary and reticular layer

44
Q

Papillary layer

A

Upper layer (right below epidermis) of dermis, which consists of loose connective tissue

45
Q

Reticular layer

A

Below the papillary layer: contains sweat glands, blood vessels, and hair follicles

46
Q

Merkel cells (discs)

A

Sensory receptors present at the epidermal-dermal junction –> connected to sensory neurons and responsible for deep pressure and texture sensation within the skin.

47
Q

Meissner’s corpuscles

A

Respond to light touch

48
Q

Ruffini endings

A

Respond to stretch

49
Q

Pacinian corpuscles

A

Respond to deep pressure and vibration

50
Q

Hypodermis

A

Layer of connective tissue that connects the skin to the rest of the body

51
Q

Brown fat

A

Present especially in infants: has a much less efficient electron transport chain, which means that more heat energy is released as fuel is burned

MCAT BIO my flashcards (15 decks)

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