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MCAT > Biology Ch 10. Homeostasis > Flashcards

Biology Ch 10. Homeostasis Flashcards

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MCAT flashcards
1
Q

Excretory system

A

Serves many functions including the regulation of blood pressure, blood osmolarity, acid base balance, and removal of nitrogenous wastes, consists of the kidneys, ureters, bladder, and urethra

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2
Q

Kidney

A

Two bean shaped structures located behind the digestive organs, produced urine, contains a cortex and a medulla, each has a hilium and portal system, participates in solute movement through filtration, secretion, and reabsorption, under hormonal control, can regulate pH by increasing or decreasing secretion of hydrogen ions and bicarbonate , functional unit is the nephron

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3
Q

Urine path

A

Kidney, ureter, bladder, urethra

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4
Q

Ureter

A

Transports urine from the kidney to the bladder to be stored, at the renal pelvis

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5
Q

Renal pelvis

A

Where all nephrons empty into that narrows into the ureter (ie the widest part of the ureter)

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6
Q

Bladder

A

Stores urine, has detrusor muscle and two sphincters

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7
Q

Urethra

A

Where urine is excreted

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8
Q

Hilium

A

Part of a kidney, deep slit in the center of the kidney’s medial surface, contains renal artery, renal vein, and ureter

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9
Q

Kidney portal system

A

Two capillary beds in series, the renal artery branches into afferent arterioles which then form glomeruli, after the glomeruli, blood passes to efferent arterioles

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10
Q

Bowmans capsule

A

Cuplike structurearound the glomerulus, in the first capillary bed blood from the renal artery in the medulla flows into afferent arterioles in the cortex which form glomeruli, leads to long tubule of the PCT, loop of henle, DCT and collecting duct

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11
Q

Vasa recta

A

Second capillary bed in the kidney, blood from efferent arterioles, surrounds the nephron, leave kidney in renal vein, surround the loop of henle

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12
Q

Detrusor muscle

A

Muscular lining in bladder, under parasympathetic control

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13
Q

Internal urethral sphincter

A

Consists of smooth muscle and is under involuntary/parasympathetic control

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14
Q

External urethral sphincter

A

Consists of skeletal muscle and is under voluntary control

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15
Q

Kidney filtration

A

The movement of solutes from blood to filtrate at Bowmans capsule, the direction and rate of filtration is determined by starling forces, hydrostatic pressure higher in the glomerulus so fluid moves into nephron, osmolarity higher in the glomerulus which opposes the movement of fluid into the nephron, net flow still from blood into nephron but rate will vary

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16
Q

Starling forces kidneys

A

Account for the hydrostatic and oncotic pressure differentials between the blood and Bowmans space

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17
Q

Kidney secretion

A

The movement of solutes from blood to filtrate anywhere other than Bowmans capsule by either active or passive transport, quantity and identify of substances secreted directly related to the needs of the body at that time, also a mechanism for excreting wastes that are simply too large to pass through glomerular pores

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18
Q

Kidney reabsorption

A

Movement of solutes from filtrate to blood, typically glucose, amino acids, and vitamins always reabsorbed, amount of water reabsorbed depends on ADH or aldosterone levels

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19
Q

Nephron segments

A

Proximal convoluted tubule, descending limb of the loop of Henle, ascending limb of the loop of Henle, distal convoluted tubule, collecting duct

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20
Q

Proximal convoluted tubule

A

PCT - The site of book reabsorption of glucose, amino acids, soluble vitamins, salt, and water (picked up by vasa recta and returned to blood stream), it is also the site of secretion for hydrogen ions, potassium ions, ammonia, and urea, filtrate remains isotonic, in the kidney cortex

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21
Q

Descending limb of the loop of Henle

A

Permeable to water but not salt, therefore as filtrate moves into the more osmotically concentrated renal medulla, water is reabsorbed from the filtrate. the vasa recta and nephron flow in opposite directions creating a countercurrent multiplier system that allows maximal reabsorption of water, dives from cortex to inner medulla

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22
Q

Countercurrent multiplier system

A

System that allows the maximal reabsorption of water such as how the vasa recta and nephron flow in opposite directions, flow of the filtrate through the loop of Henle is in the opposite direction from the flow of blood through the vasa recta, therefore, filtrate constantly exposed to hypertonic blood

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23
Q

Ascending limb of the loop of Henle

A

Permeable to salt but not water, therefore salt is reabsorbed both passively and actively, the diluting segment is in the outer medulla; because salt is actively reabsorbed in this site, the filtrate actually becomes hypotonic compared to the blood

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24
Q

Diluting segment

A

Transition from inner to outer medulla where the loop of Henle gets thicker, cells in the lining are larger because they contain large amounts of mitochondria, allows for maximum reabsorption of sodium and chloride by active transport, filtrate becomes hypotonic, only part of nephron capable of producing urine more dilute than the blood (important for overhydration)

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25
Q

Distal convoluted tubule

A

DCT - Responsive to aldosterone and is a site of salt reabsorption (water goes with the salt) and waste product excretion, like the PCT

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26
Q

Collecting duct

A

Responsive to both aldosterone and antidiuretic hormone and has variable permeability which allows reabsorption of the right amount of water depending on the body’s needs, last site of secretion/reabsorption

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27
Q

Kidney response to low blood pressure/volume

A

Both aldosterone and antidiuretic hormone hormonal systems are activated

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28
Q

Aldosterone

A

A steroid hormones regulated by the renin-angiotensin-aldosterone system that increases sodium reabsorption in the distal convoluted tubule and collecting duct, thereby increasing water reabsorption. This results in increased blood volume and pressure but no change in blood osmolarity, also increases potassium and hydrogen ion excretion

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29
Q

Antidiuretic hormone

A

ADH - aka vasopressin - a peptide hormone synthesized by the hypothalamus and released by the posterior pituitary, it’s release is stimulated not only by low blood volume but also buy high blood osmolarity, it increases the permeability of the collecting duct to water increasing water reabsorption. This results in increased blood volume and pressure and a decreased blood osmolarity

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30
Q

Kidney pH regulation

A

Can you still buy selective reabsorption and secretion of bicarbonate or hydrogen ions

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31
Q

Kidney cortex

A

Kidney’s outermost layer

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32
Q

Kidney medulla

A

Sits within the cortex of the kidney

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33
Q

Glomeruli

A

Highly convoluted capillary tufts derived from afferent arterioles

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34
Q

Afferent arterioles

A

Arterioles that flow into kidney’s first capillary bed, form glomeruli, in medulla of kidney

35
Q

Efferent arterioles

A

Arterioles that flow into kidney’s second capillary bed or vasa recta, in medulla of kidney

36
Q

Micturition reflex

A

When the bladder is full and stretch receptors cause parasympathetic neurons to fire, detrusor muscle contracts, this causes the internal sphincter to relax; however, urination does not occur unless the individual relaxes the external sphincter also with voluntary control

37
Q

Osmoregulation

A

Primary job of the kidneys, done by filtration, secretion, and reabsorption

38
Q

Filtrate

A

Collected fluid that is filtered from the blood to Bowmans space

39
Q

Interstitium

A

Connective tissue surrounding the nephron, where molecules are reabsorbed to be sent back to vasa recta

40
Q

Filtrate from beginning to end of nephron

A

Beginning - isotonic

End - volume significantly reduced, hypotonic (filtrate has been diluted)

41
Q

Renin-angiotensi-aldosterone pathway

A

Decreased blood pressure - > release of renin from juxtaglomerular cells in the kidney - > renin cleaves angiotensinogen to angiotensin I -> angiotensin I metabolized by angiotensin-converting enzyme in the lungs to angiotensin II -> promotes release of aldosterone from the adrenal cortex

42
Q

Juxtaglomerular cells

A

Cells in the kidney that release renin in response to low blood pressure

43
Q

Angiotensinogen

A

A liver protein that is cleaved to angiotensin I by renin

44
Q

Angiotensin I

A

Peptide cleaved from angiotensinogen by renin

45
Q

Angiotensin-converting enzyme

A

Enzyme in the lungs which metabolizes angiotensin I to angiotensin II

46
Q

Angiotensin II

A

Promotes the release of aldosterone from the adrenal cortex, metabolized from angiotensin I

47
Q

Osmotic presssure

A

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

48
Q

Oncotic pressure

A

The osmotic pressure that is attributable to dissolved proteins specifically

49
Q

Low blood osmolarity

A

Excess water excreted, solutes reabsorbed in higher concentrations

50
Q

High blood osmolarity

A

Water reabsorption increases, solute excretion increases

51
Q

Bicarbonate buffer system

A

CO2(g) + H2O = H2CO3 = H+ + HCO3-

major regulator of blood pH

52
Q

Skin

A

aka integument, largest organ in body, acts as a barrier, protecting us from the elements and invasion by pathogens (part of the nonspecific immune defense), important for thermoregulation, prevents dehydration and salt loss from the body, derived from the ectoderm

53
Q

Skin layers

A

Hypodermis (deepest), dermis (middle), epidermis (surface)

54
Q

Epidermis layers

A

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum, called strata

55
Q

Stratum basale

A

Bottom layer of the epidermis, contains stem cells that proliferate to form keratinocytes, also home to melanocytes

56
Q

Stratum granulosum

A

Layer of epidermic, where keratinocytes die and lose their nuclei

57
Q

Stratum corneum

A

Layer of the epidermis, made of many thin layers of flattened keratinocytes, forms barrier that prevents pathogen invasion or fluid/salt loss

58
Q

Melanocytes

A

Produce melanin, derived from neural crest cells, found in stratum basale

59
Q

Melanin

A

Pigment that protects the skin from DNA damage caused by ultraviolet radiation, pigment is passed to keratinocytes after being produced

60
Q

Langerhans cells

A

Special macrophages that serve as antigen-presenting cells in the skin, reside in stratum spinosum

61
Q

Dermis layers

A

Papillary layer and the reticular layer

62
Q

Dermis sensory cell types

A

Merkel cells, free nerve endings, Meissners corpuscles, Ruffini endings, and Pacinian corpuscles

63
Q

Merkel cells

A

Sensory cell that senses deep pressure and texture

64
Q

Free nerve endings

A

Sense pain

65
Q

Meissners corpuscles

A

Sensory cell that sense light touch

66
Q

Ruffini endings

A

Sensory cell that sense stretch

67
Q

Pacinian corpuscles

A

Sensory cell that senses deep pressure and vibration

68
Q

Hypodermis

A

Contains fat and connective tissue, connects the skin to the rest of the body

69
Q

Thermoregulation cooling mechanism

A

Sweating and vasodilation

70
Q

Sweating

A

Draws heat away from the body through evaporation of water from swear

71
Q

Sweat glands

A

Innervated by postganglionic cholinergic sympathetic neurons

72
Q

Thermoregulation warming mechanism

A

Piloerection, vasoconstriction, shivering, and insulation provided by fat

73
Q

Piloerection

A

Arrector pili muscles contract causing hairs to stand on end (traps a layer of warmed air around the skin)

74
Q

Keratinocytes

A

Predominant cells in the skin, produce keratin, proliferate in stratum basal, become connected to each other in stratum spinosum, die in stratum granulosum

75
Q

Keratin

A

Created by keratinocytes, resistant to damage and provides protection against injury, water, and pathogens , also forms fingernails and hair

76
Q

Startum spinosum

A

Keratinocytes become connected to each other, site of langerhans cells, layer of epidermis

77
Q

Stratum lucidum

A

Only present in thick, hairless skin (sole of foot and palms), nearly transparent, layer of epidermis

78
Q

Calluses

A

Form from excessive keratin deposits in areas of repeated strain due to friction

79
Q

Fingernails and hair

A

Formed by keratin and produced by specialized cells

80
Q

Papillary layer

A

Upper layer of the dermis that consists of loose connective tissue

81
Q

Reticular layer

A

Lower layer of the dermis

82
Q

Dermis

A

Divided into papillary and reticular layer, where sweat glands, blood vessels, and hair follicles originate, where most sensory receptors are located

83
Q

Brown fat

A

Tissue found especially in infants that has a much less efficient ETC and more heat energy is released as fuel is burned

MCAT (67 decks)

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