chapter 7 - homeostasis of body temp / fluids Flashcards
1
Q
what are sources of heat input and output
A
- input: heat from body processes (metabolism, respiration of liver and muscle cells), heat gained from surroundings by conduction and radiation
- output: evaporation of water from skin and lungs, warm urine / faeces
2
Q
explain cellular respiration
A
- cellular respiration: food is oxidised in cells and energy is stored in chemical bonds in proteins, carbohydrates and fats and later released
- energy is used for muscle contraction, active transport, anabolism, form of heat
3
Q
explain metabolic rate
A
- rate at which energy is released by the breakdown of food
- body temp is usually higher than environmental due to metabolic activity (during exercise, MR increases, body temp therefore increases thus body needs to decrease temp; homeostasis)
- factors affecting: exercise (more muscle activity increased MR x40, increased heat), stress (sympathetic division of ANS, more adrenaline / noradrenaline, increased MR, increased heat) and rising body temp by 1*C intervals causes increased MR x10
4
Q
what is thermo regulation and why does it happen
A
- maintaining the balance between heat production and heat loss
- body temp must be around 36.8 which is optimum for cellular reactions and enzyme activity
- increased temp can cause nerve malfunction, change in structure of proteins, denature of enzymes (deactivation if decreased temp), and death
5
Q
how is the skin involved in temperature regulation
A
- BV: carry blood to skin from core of body (lose heat through conduction, convection, radiation and evaporation)
- BV diameter: controlled by ANS to increase / decrease BF to surface
- sweating: when BV are dilated, active secretion of fluid by sweat glands / periodic contraction of cells surrounding ducts (sympathetic nerves stimulate production / transport of sweat to skin
- > evaporation: of sweat = cooling effect when sweat (l) turns to vapour (g)
- > absence: of sweat, continual loss of water via evaporation (lungs, respiratory system)
6
Q
explain the types of heat transfer
A
- conduction: heat is transferred to another object by direct contact (heat goes from hot object to cool object)
- convection: when cool air makes contact with body it becomes warm (heat leaves body and vice versa), air moves away via convection currents (faster flow = faster transfer)
- evaporation: conversion of (l) to (g), surface is subsequently cooled (via latent heat energy)
- radiation: transfer of heat from one object to another without direct contact, heat leaves body in form of infrared radiation (heat radiates from body to cooler objects and vice versa)
7
Q
how does the body prevent temp from falling
A
- vasoconstriction: peripheral TR - hyp. - sympathetic NS - BV in skin - vasoconstriction - decreased BF of warm blood to skin - decrease heat loss
- adrenaline / noradrenaline: central TR - hyp. - sympathetic NS - adrenal medulla - adrenaline / noradrenaline - increase MR - increase heat prod.
- increase in MR: central TR - hyp. - RF - anterior pituitary - TSH - thyroid gland - thyroxine - increased MR - increased heat prod.
- shivering: central TR - hyp. - cerebral cortex - increase skeletal muscle tone - oscillating / rhythmic muscle tremors - shivering - metabolic activity produces more heat
- behavioural: central TR - hyp. - cerebral cortex - put on clothing / shelter from cold wind / eat to increase MR / heater / decrease SA - decreased heat loss
8
Q
how does the body prevent temp from rising
A
- vasodilation: peripheral TR - hyp. - sympathetic NS - BV in skin - vasodilation - skin is reddish / surface temp rises - increase heat loss (radiation / convection)
- sweating: peripheral TR - hyp. - sympathetic NS - production / transfer of sweat to skin - periodic contraction of cells surrounding ducts / glands - increased heat loss (evaporation: only when not humid, environmental temp must be <37)
- decreased MR: central TR - hyp - IF - anterior pituitary - decreases TSH to thyroid - decreased MR - decrease heat prod.
- behavioural: central TR - hyp. - cerebral cortex - turn on fan / AC / remove clothing, decrease physical activity - increase heat loss / decrease heat prod.
9
Q
explain heat stroke, heat exhaustion and hypothermia
A
- HS: temp / relative humidity are high - difficult / little heat loss via - evaporation / radiation - increased body temp (regulating mechanisms cease) - >42 very serious / 44-46 is fatal - treatment (immerse in cold water)
- HE: extreme sweating / vasodilation (body temp almost normal) - decrease V(plasma) / decrease resistance to BF - decreased BP - output from heart decreases
- hypo: very low MR - heat production cannot restore - body temp continues to fall - death <32
10
Q
describe the contents of intra and extra cellular fluid in the body
A
- I: fluid inside cell (cytosol) 2/3 of total body water
- E: plasma (1/4 of E fluid, fluid part of blood) and intercellular fluid (3/4 of E fluid, interstitial tissue / fluid, comprised of lymph, CSF, synovial fluid of eyes / ear / chest / abdominal cavities, around heart, alimentary canal and kidney filtrate)
- the different fluids aren’t isolated, continual exchange of materials, water moves easily through plasma membranes
11
Q
describe how fluid balance is maintained
A
- fluid gain must equal fluid loss if composition is to be kept constant
- water intake (2500mL): drink (1600), metabolic water (water produced from cellular respiration 200), food (700)
- water loss (2500mL): faeces (200), kidneys (1500), skin (500), lungs (300)
12
Q
describe the process of excretion
A
- E: removal of waste products (from metabolism), from the body
- lungs: excretion of CO2 and H2O (g), CO2 is produced during cellular respiration and cannot be used by the body
- sweat glands: secrete water containing the by-products of metabolism (salt, urea, lactic acid)
- alimentary canal: excretes bile products (breakdown products of haemoglobin), leaves body with faeces (with undigested food = not a by product = not made by cells)
- kidneys: maintain constant conc. of materials in body fluids
13
Q
go into detail about the kidneys
A
- F: excrete water as urine (60% of water lost each day is via kidney)
- regulation: water loss from lungs, alimentary canal and skin cannot be regulated, kidney can
- S: kidneys (produce urine), nephron (functional unit, filtration / excretion), renal artery (B to K), renal vein (K to B), uretar (tube that leaves kidney with urine), bladder, urethra
- nephron: 99% of water filtered through glomeruli is reabsorbed, occurs in PCT, loop of henle via osmosis and in DCT and CT via active transport (controlled by ADH)
14
Q
how is water loss and salt loss controlled
A
- low [H2O] and high osmotic pressure - osmoreceptors in hyp. - hyp. - ADH - posterior lobe - ADH - kidney - increased permeability to water of DCT and CT - increased reabsorption of water into peri tubular capillaries - increased [H2O] in plasma / decreased osmotic pressure
- low osmotic pressure - osmoreceptors in hyp. - hyp. - RF - anterior lobe - ACTH - adrenal glands - aldosterone - increased permeability to salts (and water) of DCT and CT into peri tubular capillaries - increased [salt and water] in blood - increased osmotic pressure and BP (more volume)
15
Q
how is water intake controlled
A
- dehydration: water loss - intercellular fluid moves into plasma by osmosis - intercellular is more concentrated - water diffuses out of intracellular fluid - cells shrink
- low water / reduction in plasma volume / increase in osmotic pressure / concentration of extracellular fluid - osmoreceptors in thirst centre in hyp. / stimuli of dry mouth - stimulation makes person feel thirsty - conscious response to drink - fluid consumed is absorbed into plasma by alimentary canal - enables inter / intra cellular fluid to return to proper osmotic conc. - excess fluid in extraC. is collected by lymph - returned to blood
