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Yr.12 Human Biology > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

Homeostasis

A

maintenance of a relatively constant internal environment despite fluctuations in the external environment.

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2
Q

Feedback system

A

a situation where the response to a stimulus changes the original stimulus.
Negative feedback - response reduces stimulus

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3
Q

glucose and glycogen

A

glucose - Monosaccharide -simple sugar found in the bloodstream, principle fuel for energy.
Glycogen - polysaccharide -1000’s of glucose molecules, bonded together in branching chains, function -a storage form of glucose
glycogen storage - 500g stored: 100 in liver cells, 400 skeletal muscles

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4
Q

Glucose metabolism

A

Glycogenesis
Glycogenolysis
Gluconeogenesis
Lipolysis
Lipogenesis

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5
Q

Glycogenesis

A

making glycogen from glucose (insulin) occurs in the liver

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6
Q

Glycogenolysis

A

breakdown of glycogen to glucose (glucagon and cortisol) occurs between meals (in liver and skeletal muscles)

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7
Q

Gluconeogenesis

A

Making glucose from fats or proteins (AA)
(Glucagon, adrenaline and cortisol) occurs in liver

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8
Q

Lipolysis

A

Lipids (fats) broken down and used directly by cells
Occurs in adipose tissue stores

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9
Q

Lipogenesis

A

Glucose -> fats
occurs in liver and adipose tissue.

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10
Q

Role of pancreas

A

Hormone secreting cells of pancreas: Islets of Langerhans
alpha cells - secrete glucagon, causes in increase in Blood glucose levels
Beta cells - secretes insulin, causes decrease in blood glucose level

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11
Q

role of Adrenal gland

A

Outer cortex - Glucocorticoids - cortisol stimulated by Adrenal Coriticotrophic hormone (anterior pituitary gland). Regulates carbohydrate metabolism (2 ways). Slow acting - long term effects, time of stress or fasting
Inner medula - adrenaline (epinephrine) + Noradrenaline (Norepinephrine), hormone produces same effects of Sympathetic Nervous System (SNS) of Autonomic Nervous System (ANS). Increase Blood Glucose Level by Glycogenolysis in liver. In muscles: Lactic Acid -> glycogen -> liver -> glucose. Fast-acting - short term regulation eg. Between meals, stress, exercise

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12
Q

Role of liver

A

blood supply via hepatic portal vein directed to the liver, where glucose is:
I) removed by the liver for liver function
II) allowed to circulate for all body cells to use
III) converted/stored as glycogen in the liver and/or muscle cells
IV) converted to fat for long term storage (adipose tissue)
V) liver can convert AA’s and lactic acid to glucose when blood sugar levels are low

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13
Q

Hypoglycaemia

A

low blood sugar (few hours after meal)
Symptoms: tiredness, confusion, dizziness, headaches, mood swings, muscle weakness, tremors

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14
Q

Hyperglycaemia

A

High blood sugar level
Symptoms: excessive thirst, frequent urination, fatigue, unexplained weight loss, vision problems, increased susceptibility to infections

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15
Q

heat transfer methods

A

Conduction
Convection
Radiation
Evaporation

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16
Q

Conduction

A

Heat energy is transferred from one solid object to another by direct physical contact

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17
Q

convection

A

Heat energy is transferred by the movement of fluids (water or air)
eg. Air warms up in contact with body surface, moves away, cooler surface.

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18
Q

Radiation

A

heat energy moves from a warmer object to a cooler object across space, or a vacuum, no contact between the bodies is necessary.

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19
Q

Evaporation

A

the conversion of a liquid into a gas which requires energy
Sweating produces water onto surface of skin. To convert water into gas, energy required which comes in form of heat being radiated from the blood at the surface, thus cooling body.
can only cause heat loss.

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20
Q

Temperature receptors

A

peripheral thermoreceptors
Central thermoreceptors
cold receptors
Heat receptors

21
Q

peripheral thermoreceptors

A

Found in: skin and mucous membranes
detects temperature in external envrionment
Sends info to hypothalamus

22
Q

central thermoreceptors

A

Found in hypothalamus
detect temperature in internal environment
Can also be found in spinal cord + abdominal organs, but sends info to hypothalamus

23
Q

cold thermoreceptors

A

Stimulated by low temperature
once stimulated, sends into to hypothalamus
Stimulates heat production + heat conservation

24
Q

Heat thermoreceptors

A

Stimulated by temperature higher than normal
stimulated and sends info to hypothalamus
Stimulates heat loss + reduces heat production

25
Q

importance of H2O and dissolved substance in blood

A

I) transporting substances (O2, nutrients, hormones)
II) facilitating movement of molecules across cell membrane
III) site of chemical reactions
IV) regulates body temperature (sweating, cellular respiration)

26
Q

Extracellular fluid

A

1/3 of all liquid in body, 2/3 in intracellular fluid
Intravascular - blood plasma (in blood vessels)
Interstitial - fluid between cells (intercellular/tissue)
Transcellular - fluid in specific body regions. (In brain, spinal cord, eyes, joints, lymph, around heart.)

27
Q

osmosis and osmotic pressure

A

Osmosis: the passive diffusion of water through a semi-permeable membrane from high conc -> low conc.
H2O moves easily through membranes - so any difference in osmotic concentration between intra+extracellular fluid does not last long.
Water always goes to where there is less water. As water diffuses into a cell, pressure builds up in a cell. Eventually, pressure in cell is balanced to osmotic pressure outside

28
Q

osmotic concentration

A

Concentration of solutes (osmolarity)

29
Q

osmotic pressure

A

Occurs if there is an imbalance between H2O molecules and solutes inside (ICF) and outside (ECF) of the cell

30
Q

excretion

A

Removal of metabolic wastes from the body
1) lungs - CO2 and H2O vapour as we exhale
2) sweat glands - H2O, salts, urea and lactic acid
3) alimentary canal - bile pigments from breakdown of haemoglobin from RBC’s -> faeces
4) kidneys - primary excretory organs, urea produced in liver (deamination) from breakdown of proteins, are taken to kidneys for removal

31
Q

3 steps of urine production

A

1) Glomerular filtration - removes much of the water from the blood and everything dissolved in it, filtrate forms in capsule.
2) Selective reabsorption - where most of the water and anything useful to the body is taken back into the blood, mainly in Proximal convolutes tubule (PCT) in loop of henle. Mainly water reabsorbed, sodium pumps more sodium (Na+) out of filtrate + water follows by osmosis.
3) tubular secretion - mainly in Distal convoluted tubule (DCT), adds materials to filtrate (from blood), anything body still wants to excrete (secreting from bloodstream)

32
Q

Kidneys and Antidiuretic Hormone (ADH)

A

Volume + composition of urine depends on how much H2O there is in the body
ADH most sensitive to increase is Na+ concentration. Reabsorption of H2O in kidneys, 99% in PCT controlled by osmosis (passive), 1% in DCT controlled by ADH (active)
ADH reduces urine production
ADH produced by hypo, stored and released from posterior pituitary gland.
ADH lets H2O through walls of DCT and out of collecting duct.

33
Q

Kidneys and Aldosterone

A

Aldo helps regulate H2O output (balance)
Aldo acts on DCT and CD to increase Na+ reabsorption and K+ secretion in urine
Does this through active transport via Na+/K+ pump, every 3Na+ reabsorbed, 2K+ secreted.
reduces urine output in Kidneys

34
Q

Aldosterone

A

Salt-retaining hormone - secreted by adrenal cortex in response to:
I) decrease in Na+ conc.
II) decrease in blood volume
III) decrease in blood pressure
IV) increase in K+ conc.
Increases K+ and decreases Na+ in urine

35
Q

thirst response

A

Osmoreceptors stimulate stimulate thirst centre of hypo -> symp. Nerve signals to salivary glands to inhibit/reduce salivation -> dry, sticky mouth -> sense of thirst - cerebral cortex -> person drinks water -> digestive system -> absorbed into blood -> decreased osmotic pressure.
Response is behavioural

36
Q

excess extracellular fluid

A

Called by lymphatic system and returned to blood by lymph vessels that join subclavian vein in upper chest near heart

37
Q

dehydration

A

Cause: exercise, blood loss, vomiting, severe burns
humans can withstand 2-10% loss of body weight from dehydration. If more lost -> blood becomes viscous -> high osmotic pressure -> can’t be carried to body surface -> heat exhaustion -> heat stroke -> death.

38
Q

Water intoxication (water poisoning)

A

excess fluid, less common
Hypotonic extracellular fluid -> cellular swelling (cerebral edema)

39
Q

Diuretics

A

Chemicals that increase urine volume
used to treat hypertension (increased BP) and congestive heart failure because they decrease body’s fluid volume.
Caffeine/tea - reduces tubular secretion
Alcohol - inhibits ADH secretion

40
Q

Control of breathing

A

Medulla oblongata has respiratory system with two parts: Expiratory centre (out) and Inspiratory centre (in)
For coordination, messages go back and forth between the neurone in these 2 groups.
vagus nerves - transmit sensory signals from stretch receptors to medulla oblongata.
Phrenic nerve - stimulates diaphragm
intercostal nerves - stimulates intercostal muscles
Origin point of Phrenic and intercostal nerves: Neck - phrenic, thorax - intercostals

41
Q

unconscious breathing

A

Neurons in Medulla oblongata provide automatic control -> spinal cord -> phrenic and intercostal nerves
Regular breathing: asleep, unconscious

42
Q

Voluntary breathing

A

Neurons in motor cortex region of cerebrum (frontal lobe) -> spinal cord (higher brain centre)
Bypasses respiratory centre in MO
holding our breath, speech, singing, sneezing, coughing, talking, pain, smoking, laughing, crying
This is a protective reflex - to prevent poisonous gases + water from entering lungs
breaking point is reached then automatic controls override one’s will.
Eventually build up of CO2 in plasma -> inspiratory centre -> inspiratory muscles -> forced to take a breath in.

43
Q

Peripheral chemoreceptors (outside CNS)

A

located in Aorta (aortic bodies) + in carotid arteries (carotid body)
Sensitive to changes in O2, CO2, and H+ in blood plasma

44
Q

Central chemoreceptors

A

Medulla Oblongata
CO2 in blood + H+ levels in CSF

45
Q

O2 concentration

A

As oxygen is used by cells, its conc. On the blood falls. Unless 02 levels are extremely low, it will not affect breathing rate.
Aortic and Coratid bodies are sensitive to oxygen.
A large decrease, stimulates peripheral chemoreceptors which send impulses to the respiratory centre of the medulla oblongata which in turn sends impulses to the respiratory muscles (diaphragm + ic) to increase breathing rate and depth.
This does not happen in normal situations, brain damage - after minutes when heart stops.

46
Q

CO2 concentration

A

Is the major factor affecting Breathing Rate
a small increase in CO2 conc. Will cause a large increase in BR and depth.
Increase in CO2 causes increase in H+ which directly stimulates the c + p chemoreceptors -> nerve impulses to respiratory centre -> increase breathing rate and depth.
Response to increase in CO2 (central chemo. in MO) is not immediate, takes several minutes vs CO2 increase elicits an immediate response, or Increase in BR by aortic + coratid bodies.

47
Q

H+ concentration

A

Increase in H+ ions in the blood causes pH to decrease = increase in BR
Increase in H+ ions detected by chemoreceptors in aortic and carotid bodies -> sends messages to respiratory centre directly to increase breathing rate + depth
The pH of blood is maintained at 7.4 by the carbonic acid - bicarbonate ion buffering system
CO2 + H2O <-> H2CO3 <-> H+ + HCO3-
H2CO3 = carbonic acid
H+ + HCO3- = bicarbonate ions

48
Q

hyperventilation

A

Extremely rapid or deep breathing, may result in dizziness or fainting, due to loss of CO2 from blood, BR over 20BrPM
Expels CO2 faster than it is produced. Too much CO2 breathed out -> CO2 levels in blood drop -> pH increases, chemoreceptors are not stimulated in these cases. Results in narrowing of blood vessels -> vasoconstriction to the brain -> results in dizziness, lightheadedness, unsteady.
This reduces the urge to breath and the person may stop breathing and even lose consciousness. Build of of CO2 will eventually cause the person to start breathing regardless of conscious state.
causes drowning.
Treatment: rebreathe the exhaled CO2 from a paper bag, breath slowly into a paper bag - close to mouth + nose - breath in more CO2 to increase levels in blood

49
Q

exercise and breathing

A

More energy is needed, so more glucose broken down in presence of O2 and more CO2 produced (and H2O).
both the BR + depth increase
Factors influencing Breathing: CO2 conc, pH change, lesser extent of O2.
O2 conc. in plasma of arteries not significantly reduced due to increase in ventilation.
CO2 conc in plasma is the controlling factor in the initiation of an increase in BR.
Build up of H+ - due not to CO2 accumulation - but by increase in lactic acid.

Yr.12 Human Biology (7 decks)

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