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d3.3 (homeostasis) Flashcards

1
Q

regulation of homeostasis relies on what mechanism?

A

negative feedback loops (the response to some stimulus affecting the variable is corrective)

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2
Q

5 examples of - feedback loops in homeostasis in humans

A

heart rate

blood pH

blood glucose

body temperature

blood osmolality

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3
Q

3 examples of + feedback loops in homeostasis in humans

A

blood clotting triggers more blood clotting

uterus contractions trigger more uterus contractions during childbirth

a cancer cell will cause there to be more cancer cells

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4
Q

define endotherm

A

organisms that generate heat internally to maintain a steady body temperature (examples: birds and mammals)

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5
Q

define ectotherm

A

organisms that rely on external heat sources to regulate their body temperature (examples: lizards and most fish)

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6
Q

define thermoregulation

A

the maintenance of a core body temperature despite fluctuations in external temperatures by balancing heat generation with heat loss

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7
Q

thermoregulators maintain body temperature homeostasis via negative feedback mechanisms. what are 2 responses to heat?

A

vasodilation (widening of blood vessels)

sweating

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8
Q

thermoregulators maintain body temperature homeostasis via negative feedback mechanisms. what are 4 responses to cold?

A

vasoconstriction (contracting of blood vessels)

shivering

uncoupled respiration (a process that dissipates energy instead of using it to perform work)

piloerection (goosebumps)

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9
Q

5 steps of negative feedback in overly hot conditions

A

1 (stimulus): body temperature rises due to exercise or hot environment

2 (receptor): thermoreceptors in the skin and central nervous system sense rise in body temperature

3 (control center): hypothalamus activates responses

4 (effector): blood vessels dilation and sweat glands are activated

5 (response): heat is lost from the body, decreasing body temperature

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10
Q

5 steps of negative feedback in overly cold conditions

A

1 (stimulus): cold environment causes heat to leave the body

2 (receptor): thermoreceptors in the skin and central nervous system sense drop in body temperature

3 (control center): hypothalamus activates responses

4 (effector): blood vessels constrict, shivering is activated and metabolism increased

5 (response): more heat generated and less is lost from the body, increasing body temperature

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11
Q

what are the effectors & their roles in body temperature homeostasis? x6

A

pituitary: releases a hormone that stimulates the thyroid gland to release thyroxin

thyroid: increase or decrease release of the hormone thyroxin to change basal metabolic rate

adipose tissue: brown fat cells generate heat through uncoupled cellular respiration

blood vessels: constrict or dilate to carry more or less blood towards different regions of the body

muscles: respond to signals to contract, causing shivering, hair erection and changes to ventilation rate

sweat glands: activate sweating to reduce body temperature via evaporative cooling

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12
Q

what are thermoreceptors?

A

ion channel proteins in the membrane of specific sensory neurons that help the body detect changes in temperature

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13
Q

how do thermoreceptors work upon a change in temperature? x5 steps

A
  1. channels open
  2. flow of ions
  3. cell membrane depolarization
  4. electrical impulses propagated along nerve fibres
  5. conveyed to the brain (hypothalamus)
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14
Q

what is the thyroid?

A

an endocrine gland located in the front of the neck, made up of two lobes that sit on either side of the trachea (wind pipe), connected by a narrow strip of tissue

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15
Q

how are cells triggered to increase their metabolic rate in body temperature homeostasis? x4 steps

A
  1. thermoreceptors sense a change in temperature and send a signal to the hypothalamus
  2. hypothalamus causes pituitary to increase secretion of TSH (thyroid stimulating horomone)
  3. TSH causes the thyroid will secrete a hormone called thyroxine
  4. thyroxine travels to target cells throughout the body, triggering the cells to increase their metabolic rate by binding to the cell’s intranuclear receptor
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16
Q

how does brown adipose tissue produce heat?

A

uncoupled cellular respiration

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17
Q

define uncoupled cellular respiration

A

a metabolic process where the mitochondria actively dissipate energy as heat instead of producing ATP

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18
Q

how does uncoupled cellular respiration work?

A

uncoupling protein 1 (UCP1) allows protons to leak across the inner mitochondrial membrane, instead of flowing back in through ATP-synthase
energy carried by protons is released as heat as it passes through UCP1
(watch a video on this)

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19
Q

how does shivering work?

A

skeletal muscles rapidly contracting and relaxing. the heat generation from muscle contractions plays a crucial role in maintaining body temperature

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20
Q

why do muscles produce heat when contracting?

A

the process of muscle contraction relies on the breakdown of ATP molecules, which is an exothermic reaction, meaning it releases heat energy

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21
Q

how does sweat cool us?

A

when sweat evaporates from the skin, it cools the body through a mechanism called evaporative cooling (as water evaporates, it absorbs heat energy from the skin, removing heat from the body).
(watch a video on this)

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22
Q

how does piloerection occur?

A

the contraction of muscles at the base of hair follicles that causes hair to stand up

the erect hairs act as a thermal insulator; the thick coat traps the warm air radiating from the body

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23
Q

how does blood movement cool us?

A

distributes heat energy generated through metabolism throughout the body

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24
Q

how does vasodilation occur?

A

muscles within the artery wall relax, causing the diameter of the artery to widen and an increase in blood flowing through the vessel

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25
how does vasoconstriction occur?
muscles within the artery wall contract, causing the diameter of the artery to narrow and a decrease in blood flowing through the vessel (decreases heat loss)
26
why do vasodilation and constriction need to be balanced?
for overall blood pressure to be constant
27
___ and ___ can withstand the largest blood volume changes
skeletal muscle and digestive system
28
___ and ___ can only tolerate very small decreases in their blood supply
brain and kidneys
29
what arteries supply blood to the brain? x2
internal carotid arteries and vertebral arteries
30
vertebral arteries join to form the ___
basilar artery 
31
_____ and _____ branch out to form the circle of willis 
basilar artery and internal carotid arteries
32
purpose of the circle of willis
ensures an uninterrupted blood supply to the brain
33
blood flows to the kidneys through the ___ blood flows out of the kidneys through the ___
renal arteries renal veins
34
nephron function
filter blood
35
what is the myogenic response?
the contraction of a blood vessel that occurs when intravascular pressure is elevated and, conversely, the vasodilation that follows a reduction in pressure
36
what is the tubuloglomerular feedback (kidneys)? (watch a video too)
specialized cells in the nephron loop monitor the sodium concentration in the tubular fluid, which then signals the afferent arteriole to adjust its diameter to maintain a consistent glomerular filtration rate
37
primary functions of the kidney x2
osmoregulation: regulating the amounts of water and salts in the blood excretion: the removal of metabolic waste products from the body
38
kidney structure x6 components & functions
renal artery brings blood to be filtered to the kidney (away from heart) renal vein takes the filtered blood away from the kidney (back to heart) ureter transports urine from the kidney to the bladder renal pelvis is where urine is funneled before leaving the kidney through the ureter medulla is the inner part of the kidney that regulates urine concentration cortex is the outer layer of the kidney, where filtering and reabsorbing of essential substances occurs
39
osmolarity unit
milliosmoles per liter (mOsm/L)
40
what does urea result from?
waste product of protein oxidation
41
kidney nephron structure & function x6
glomerulus: filters small solutes from the blood proximal convoluted tubule: reabsorbs ions, water & nutrients, also removes toxins and adjusts filtrate pH descending loop of henle: aquaporins allow water to pass from filtrate into interstitial fluid ascending loop of henle: reabsorbs Na+ and Cl- from filtrate into interstitial fluid distal tubule: selectively secretes and absorbs different ions to maintain blood pH & electrolyte balance collecting duct: reabsorbs solutes and water from filtrate
42
kidney nephron functions x4
ultrafiltration of blood selective reabsorption of essential substances secretion of waste products into filtrate to leave as urine osmoregulation to create highly concentrated urine
43
define ultrafiltration
the process by which small molecules are filtered from the blood to enter the nephron, whereas larger molecules are held back and remain in the blood
44
where does ultrafiltration occur?
in the kidney nephron at the glomerulus and bowman’s capsule
45
what is filtrate?
the fluid that is filtered out of the blood and into the nephron
46
adaptations of the glomerulus for ultrafiltration? x2
high blood pressure to push small molecules out of the blood through the capillary walls and into bowman’s capsule wider & more numerous fenestrations to allow more small molecules to pass into bowman’s capsule
47
why does the glomerulus have such high pressure?
due to a difference in diameter between the afferent arteriole (which carries blood into the glomerulus) and the efferent arteriole (which carries blood out of the glomerulus) (narrowing of the diameter of the efferent arteriole results in a build-up of pressure within the glomerular capillaries)
48
what are fenestrations? what do they allow?
small openings in the capillaries of the kidneys, small intestine, and endocrine glands allow molecules to pass between the blood vessel and surrounding tissues
49
what is bowman's capsule?
a cup-shaped structure that wraps around the capillaries of the glomerulus it is the first part of the nephron
50
where does filtrate go after being captured by bowman's capsule?
flows into the proximal convoluted tubule for further processing
51
look at slide 90 and 91 d3.3
-
52
define lumen
the interior of the proximal convoluted tube, where the filtrate flows
53
the cells that line the lumen are specialized for the function of reabsorption and secretion. how is this seen? x4 ways
microvilli on the surface facing the tubule lumen increases the surface area for reabsorption of substances like glucose, amino acids, and ions numerous mitochondria to provide ATP for active transport mechanisms involved in reabsorption cells are connected by tight junctions to prevent leakage from the tubule lumen a large number of channels and pumps for transport of materials across the plasma membrane
54
define selective reabsorption
the process by which specific molecules in the filtrate that were filtered out of the blood during ultrafiltration are actively transported back into the bloodstream
55
selective reabsorption occurs in the ______ at the ____________, which receives the filtrate from _________
kidney nephron proximal convoluted tubule bowman’s capsule
56
mechanisms by which substances move across proximal convoluted tubule cell membranes for reabsorption include: x5 ways & examples
Osmosis: Water follows the hypertonic concentration gradient established by the pumping of Na+ ions Diffusion: Urea moves passively down its concentration gradient. Facilitated diffusion: Cl- ions move passively through channel proteins Active transport: Na+ ions are moved through pump proteins Indirect active transport: Glucose and amino acids are moves through co-transporters that simultaneously move Na+ ions, utilizing the existing sodium gradient established by the Na+/K+ pump.
57
define secretion (in relation to blood & prox conv tubule)
when substances are actively transported from the blood into the proximal convoluted tubule
58
benefits of secreting things into filtrate x4
Excretion of metabolic waste products: secretion helps to remove waste molecules that were not filtered out by the glomerulus, such as bile salts, creatinine and urea. Regulation of ion balance: secretion of additional ions helps to maintain the body's electrolyte balance. Removal of toxins: secretion can eliminate harmful substances from the blood, such as antibiotics, drug metabolites and heavy metals. Acid-base balance: Secretion of hydrogen ions contributes to the regulation of blood pH for homeostasis
59
loop of henle ascending vs descending function
descending ⬇ limb: water drawn out ascending ⬆ limb actively pumps sodium and chloride ions out (into the interstitial fluid) (this creates a concentration gradient that further draws water out in the descending limb)
60
define interstitial fluid
the fluid that surrounds cells in a tissue
61
the cortex is the outer layer of the kidney, what parts of the nephron does it include? x3
glomeruli proximal convoluted tubule distal convoluted tubule
62
the medulla is the inner layer of the kidney, what parts of the nephron does it include? x2
loops of henle collecting ducts
63
what is the osmolarity of the interstitial fluid relative to the filtrate? (isotonic, hypertonic, hypotonic)
hypertonic due to the pumping of Na+ and Cl- out of the filtrate and into the interstitial fluid by cells of the ascending limb of the loop of henle
64
what is plasma osmolality a measure of
the concentration of solutes in plasma, which is the fluid part of blood
65
osmoregulation is a negative feedback loop that regulates the body's water balance. what is this feedback loop upon heavy water intake?
heavy intake of water (hyperhydration) ⇩ high water content in blood plasma (low osmolarity) ⇩ sensed by osmoreceptor cells in hypothalamus ⇩ pituitary gland releases less ADH ⇩ less water reabsorbed by kidney collecting duct ⇩ large volume of dilute urine goes to bladder ⇩ water content in blood plasma drops (raising osmolarity)
66
low blood osmolality = ? high blood osmolality = ?
low = hyperhydration (too much water in the blood plasma) high = dehydration (not enough water in the blood plasma)
67
how do osmoreceptors work? x5 steps
have aquaporin proteins spanning through their plasma membranes through which water can diffuse if plasma osmolarity becomes hypertonic, then water will move out of the cell due to osmosis, causing the osmoreceptor cell to shrink in size when the cell shrinks in size, gated ions channels open and allow positively charged ions, such as Na+, to enter the cell this causes initial depolarization of the osmoreceptor leading to action potentials being generated these action potentials release of ADH from the posterior pituitary gland, which reaches target cells in the kidney collecting duct
68
what does ADH stand for?
antidiuretic hormone
69
to increase osmolality of blood, ____ will not be ______ by the cells of the collecting duct
water reabsorbed
70
when blood plasma osmolality is high (dehydration), antidiuretic hormone (ADH) is released from the pituitary gland in the brain. what does ADH do to lower osmolality?
causes cells of the kidney collecting duct to move vesicles storing aquaporin channels to the plasma membrane vesicles then fuse with the the plasma membrane of the collecting duct cells, inserting the aquaporin channels into the membrane water will then move through osmosis through the aquaporin channel, out of the filtrate and back into the blood plasma. the adding of the water to the blood plasma will decrease the blood osmolality.

biology hl (20 decks)

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