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12 Bio > Ch 14 Homeostasis > Flashcards

Ch 14 Homeostasis Flashcards

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Biology 101 flashcards
1
Q

What is homeostasis?

A

Control systems which keep internal condition near constant

Requiring information regarding condition of the body and surroundings, detected by sensory cells

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2
Q

What are some things controlled by homeostasis?`

A
  • core body temperature
  • metabolic wastes (particularly CO2 and urea)
  • blood pH
  • blood glucose concentration
  • water potential of blood
  • concentration of respiratory gases in the blood (O2 and CO2)
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3
Q

What is tissue fluid?

A

The immediate environment of cells, tissue fluid surrounds cells. It is leaked plasma.

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4
Q

What 3 features of tissue fluid which influence cell activities?

A
  • Temperature
  • Water potential
  • Glucose concentration
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5
Q

Explain the 3 features of tissue fluid

A
  • Temperature: Low temperature slows down metabolic reactions
    high temp may denature proteins, including enzymes
  • Water potential: if water potential decreases, water flow out of cells (no metabolic reaction)
    if increase, water flow into cells and the cells may swell and burst
  • Glucose concentration: Glucose is fuel for reaction so low conc., cell respiration slow down or stop (cell has no energy source)
    high conc., may cause water to move out of cell by osmosis (disturbing cell metabolism)
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6
Q

How does homeostatic mechanism work in general?

A

Generally work by controlling blood composition which therefore controls tissue fluid composition (see page 164)

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7
Q

How does the control of homeostasis work?

A

Negative feedback control loop, involving:

  • receptor/sensor detecting relevant stimuli (relevant to condition or physiological factor being regulated)
  • effector (e.g. muscles, glands)

constant monitoring and ‘fixing’ of the changes result in the factor fluctuating around a particular ‘ideal’ value or SET POINT

stimuli is any change in a factor

  • external stimuli
  • internal stimuli
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8
Q

The pathway of homeostasis’ receptor relaying the change they detected is?

A

Receptor send information through nervous system to a central control in the brain or spinal cord

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9
Q

Why do homeostatic mechanisms involve negative feedback?

A

It is because it minimizes the difference between the actual value of the factor and the ;ideal’ value / set point

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10
Q

What are the 2 coordination system involved in homeostasis? (mammals) Describe them as well

A
  • Nervous system (information in the form of electrical impulses transmitted along the nerve cells - neurons)
  • Endocrine system (chemical messengers - hormones - travelling in the blood)
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11
Q

Which cell produces much heat that mammals generate? And how does the heat spread from that region?

A

Liver cells

Heat produced is absorbed by blood flowing through liver and is distributed around the rest of the body

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12
Q

What is the central control for body temperature?

A

Hypothalamus in the brain, the thermostat of the body

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13
Q

How does that region/organ monitor and control body temp?

A

Hypothalamus in the brain

  • Receives constant input of information (from thermoreceptors throughout the rest of the body like skin)
  • Thermoreceptor cells monitor temp of blood flowing through it
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14
Q

What is core temperature?

A

Temperature inside the body that remains very close to the set point. 37 degrees Celcius

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15
Q

Responses to low temperature detected?

A
  • Vasoconstriction, arterioles muscle blood supply to capillaries near the skin surface contract –> less heat lost from blood
  • Shivering, involuntary contraction of skeletal muscle generate heat
  • ‘Goosebumps’ / body hairs rise, muscle at hair base in the skin contract, increasing depth of fur, trapping more air. Air is poor conductor of heat, hence a good insulator (not very useful in humans but very good in other mammals)
  • Sweat production decreases, reduce heat lost from evaporation
  • Adrenaline secretion increases, increases rate of heat production in liver
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16
Q

Behavioral response?

A

Hypothalamus also stimulates higher centers in the brain to bring some behavioral responses.

e. g. animals curling up to reduce SA exposed to air, huddling together, finding source of warmth, putting on warm clothing
e. g. lying down with limbs spread out, increasing body SA exposed to air, wear loose fitting clothes, turning on the AC or fan and taking cold drinks

17
Q

Responses to low temperature detected?

A
  • Vasodilation, muscles in arteriole relax, allowing more blood to flow through capillaries near the skin
  • Body hairs lower, hairs lay flat, reducing depth of fur and layer of insulation
  • Sweat production increase, more heat lost through evaporation
18
Q

What hormones can be released by the hypothalamus?

A
  • The hypothalamus releases hormone which activates anterior pituitary gland to release Thyroid Stimulating Hormone (TSH) which stimulates the thyroid gland to secrete THYROXINE hormone
  • Adrenal glands stimulated to release ADRENALINE

All this stimulate heat production by liver

19
Q

Why is positive feedback not used in maintaining homeostasis?

A

Because when receptors sense a certain change, the change is encouraged and amplified so it doesn’t return to the normal or ‘ideal’ state

20
Q

Excretion?

A

Removal of unwanted products of metabolism (e.g. CO2 and urea)

21
Q

Where does the wastes for excretion come from?

A

CO2 = from respiring cells to lungs

Urea = produced in the liver from breaking down of excess amino acids –> deamination (liver to kidney in blood plasma)

22
Q

How are the wastes expelled from the body?

A

CO2 = exhaled out

Urea = removed from blood plasma by kidney, dissolving it in water –> urine

23
Q

Explain the deamination process and how urea is formed from it

A
  • Amino acids may be made in excess due to more protein being eaten more than necessary, and it cannot be stored.
  • It would be a waste to throw amino acids as a whole since amino acids provide useful energy so DEAMINATION is carried out.

deamination –> The removal of AMINO (-NH2) group and an extra hydrogen atom becoming NH3
The leftover KETO ACID enter krebs cycle / converted to glucose or glycogen or fat for storage

2NH3 reacts with CO2 creating UREA which is CO(NH2)2, and also water

more protein = more amino acids = more ammonia = more urea

24
Q

Characteristic of ammonia?

A

Very soluble and highly toxic, hence why it is converted to urea (less soluble and toxic)

25
Q

What are the nitrogenous excretory product? And where do they come from?

A
  • Urea (main) = from ammonia that is produced by liver deamination reacting with CO2
  • Creatinine = in liver from certain amino acids. Used in the muscles in the form creatine phosphate (acts as energy store). Some is converted to creatinine and excreted
  • Uric acid = breakdown of urines from nucleotides, not amino acids
26
Q

How is urea excreted?

A

As blood passes the kidney, urea is filtered and excreted in urine (dissolved in water to create urine)

27
Q

Mention kidney structure from outermost part to innermost part

A 
Capsule
Cortex
Medulla
Pelvis
(Ureter, ureter joins in pelvis)
28
Q

Mention the tubes in the kidney and their roles

A

Ureter = carries urine from kidney TO BLADDER

Urethra = carries urine TO OUTSIDE of the body

29
Q

Mention parts of the nephron and where it is located exactly in parts of the kidney if the kidney is seen through the longitudinal section
(the kidney is cut in half vertically)

A

Bowman’s capsule = cortex

Proximal convoluted tubule = cortex

Loop of Henle = cortex to medulla back to cortex

Distal convoluted tubule = cortex

Collecting duct = cortex to medulla to pelvis

30
Q

Describe the Bowman’s capsule

A

Each capsule surrounds a tight network of capillaries called a glomerulus.

Renal artery –> afferent arteriole –> glomerulus –> efferent arteriole –> to the rest of the nephron –> eventually going to the renal vein

31
Q

What are the two stages of the making of urine? Describe them

A
  1. Ultrafiltration
  2. Selective absorption

Ultrafiltration: filtering small molecules like urea out of the blood into the Bowman’s capsule. The molecule flows along the nephron to the ureter

Selective absorption: taking back any useful molecules from the fluid in nephron as it flows along

32
Q

Mention and describe the structures of the glomerulus which separate its lumen from the blood in the glomerular capillaries

outermost to innermost

A
  • Endothelium (cell layer): lining of the capillary, A LOT of GAPS
    each endothelial has thousands of tiny holes
  • Basement membrane: from collagen and glycoproteins
  • Epithelial cells (cell layer) –> finger like projections called podocytes with gaps in between them

pg 307 for visualization

12 Bio (2 decks)

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