Session 1 Flashcards
homeostatis, pH, temperature and body fluids how to examine cells and tissues MISSING: how to label ultrastructural components common to animal cells
define homeostatis
‘the ability of a living organism, cell or tissue to keep the conditions inside it the same, despite any changes in the conditions around it’
maintaining a state of internal balance… dynamic equilibrium
Homeo = sameness
Statis = standing still
main homeostatic controls: water, temperature + pH
what elements make up a feedback loop
stimulus = detectable change in the environment
sensor = something that monitors the current value of the variable
control centre = something that retains the desired value of the variable (and has a way of comparing that to the current value provided by the sensor)
effector = something that has the ability to change the value of the variable in a way that is determined by the control centre
positive vs negative feedback loops
negative is when a stimulus causes an effector response to bring the body back to it’s normal conditions, ie to counteract the change.
(eg body temp control and blood glucose control)
negative feedback stops when the effector ceases
positive is when the output enhances or exaggerates the original stimulus.
(eg regulation of blood clotting and the process of uterus contraction/childbirth)
positive feedback stops when the stimulus ceases
percentage of water in standard 70kg male
60% of total body weight is water
of that…
- 0.66 is intracellular fluid (inside cells)
- 0.33 is extracellular fluid
of the extracellular fluid…
- 0.75 is interstitial fluid (ie surrounds cells, but outside blood vessels
- 0.25 makes up blood plasma (more on next card)
calculating blood volume (in standard 70kg male)
0.25 of extracellular fluid (ie 5%) of total body weight is blood plasma in standard human
this is calculated to be 3.5 L (1kg = 1L)
- minus 0.5 L which is found in transmembrane space (ie plasma membranes).
- this fluid isnt plasma or intracellular fluid
- add 2 L of RBCs to add to the plasma
- therefore 5 L of total blood volume in standard male
however… actually 4.9 L due to approximations in calculations
state the body compartments where fluids accumulate
extracellular is fluid outside cells
- interstitial fluid is fluid that surrounds cells but outside blood vessels
- blood plasma makes up the total blood volume
intracellular fluid is fluid that is inside cells
transmembrane space isnt plasma or intracellular fluid. It is the space inside plasma membranes
compare and contrast water balance in males and females, and in early and late life
- females have lower % water content than men (due to higher fat content)
- babies have greater water content
- obese people have lower water content
- lean people have higher water content
- elderly people have less water content as they have increased body fat
dehydration and overhydration (water toxicity) and their effect on osmolality
dehydration
- osmolality increases
- cells and tissues initially absorb water from intersitial space
- then from each other (sacrafice of cells)
- then as tissues die, water absorbed from organs and then brain, liver, kidneys and lastly heart
water toxicity
- osmolality decreases
- osmotic pressure high
- enzymes and proteins stop working
- cells keep swelling until they burst (lysis)
what is osmolality
a function of the concentration of particles in solution
expressed in milliOsmoles
mOsm/kg
why is acid-base balance important
- measure of the concentration of H+ in blood
- higher conc of H+ means more acid, and therefore lower pH value
normal pH is 7.35 - 7.45
- normal cellular metabolism requires optimum otherwise proteins and enzymes denatured
what organs are required for maintaining acid base balance
lungs = respiratory balance
kidneys = metabolic balance
what are the normal ranges for pH, and their symptoms
acidosis: lower than 7.35
headaches, tremors, confusion, diarrhoea, nausea, arrythmia etc
normal: 7.35 - 7.45
alkalosis: greater than 7.45
tremors in hand, numbness in face, nausea, confusion and muscle twitching
below 7 and above 7.8 are likely to cause death
what are ranges for core body temperature
normal is 36.5 - 37.5
- heat exhaustion is above 40 (fitting, seizures, dizzy, confused)
- heat stroke is above 40 (hot to touch, flushed, strong bounding pulse)
- fever is above 38 (pale sweaty skin, cramps)
- mild hypothermia is 32.1 - 35 (shivering, fatigue, confusion, muscle stiffness)
- severe hypothermia is 28 - 32 (shivering stops, muscles rigid, very slow and weak pulse)
- below 28 is no vital signs, dilated pupils, unconscious, appeareance of death, go blue/grey lips and gums
hyper = too much
hypo = too little
what is the relationship between pH and [H+]
double [H+] for every 0.3 decrease in pH
remember 7.4 pH and 40 nanomoles/L [H+]
ie when pH decreases, [H+] increases
mechanisms of pH control in the body (in broad terms)
each part of the body works at a different optimum of pH
buffer systems
- proteins as buffers as they can act as H+ donors or acceptors
- phosphate buffers too
- buffers help when there are minor changes in pH eg due to exercise where acidic CO2 in blood
respiratory control
- eg during exercise, CO2 levels increase due to respiration
- CO2 dissociates into carbonic acid in the tissues
- this lowers pH
- therefore the resp rate increases to increase blood flow to lungs and remove CO2 more quickly (gas exchange)
renal control
- kidneys control pH of extracellular tissues
- if pH too high, secretes H+ ions
- if pH too low, retains H+ and secretes HCO3- ions
mechanisms of temperature control in the body (in broad terms)
sensor = skin and hypothalamus
control centre = hypothalamus
effectors = muscles, blood vessels, hairs on skin, fat and sweat glands
if too hot…
- vasodilation where arterioles dilate so more blood enters capillaries, so heat is lost
- sweating glands secrete sweat, which uses excess heat energy from the body to evaporate off the skin surface
- pilorelaxation where the hairs flatten, trapping less hot air and allowing more evaporation
- stretching out where the body is making use of a larger surface area
if too cold…
- vasoconstriction to keep core warm
- shivering to generate heat by respiration
- piloerection
- curling up
main heat source is respiration
describe mechanism of oedema
oedema = fluid retention aka dropsy
where the hydrostatic pressure is greater than the osmotic pressure…
- capillaries have tiny holes throughout length, called fenestrations which allow ultrafiltration of water
- if tissues are damaged, fenestrations increase in size, allowing albumen to exit capillary (plasma loss), so now oncotic pressure is outside blood stream, sucking more water out capillary
- normally water that leaks out during ultrafiltration is returned to bloodstream by lymphatic system
- if lymphatic system fails/is blocked, water accumulates, causing oedema
oedema can also cause drop in BP, due to water leaving bloodstream, causing lower blood volume, and therefore lower BP… also causing less O2 delivery to cells
describe mechanism of ultrafiltration (broad terms)
- there is a higher pressure at the arteriole end of capillary than the venule end, and this is due to higher BP
- fenestrations in capillary only let small molecules, such as water through
- larger proteins, eg albumen, remain in capillary
- high hydrostatic pressure at arteriole end forces small molecules out
- most water re-enters at venous end by osmosis, due to osmotic pressure, created by albumen remaining in capillary
- water also re-enters venous end due to hydrostatic pressure gradient
- rest of water is removed by lymphatic vessel, part of lymphatic system, which drains back into the blood near the heart, into veins
tonicity (hypo/hyper etc and where water moves in and out of cells)
water movement is always down concentration gradient by osmosis
cell in hypotonic solution
- the solute concentration is lower outside cell
- water moves into cell
- cell swells and bursts
- osmotic lysis / haemolysis
cell in isotonic solution
- the solute concentration is equal in and out of the cell
- no net movement of water
- the same amount of water on both sides of plasma membrane
cell in hypertonic solution
- the solute concentration is higher outside cell
- water moves out of cell
- cell shrinks
what are tissues (and give the 4 main different types)
tissue = a collection of cells specialised for a specific function. It is a Latin word meaning ‘woven’
- Muscle tissue eg cardiac muscle
- Nerves eg sympathetic nerve
- Epithelial eg skin
- Connective (holds other tissues together)
relationship between milli, micro and nano metres
milli x1000 = micro
micro x 1000 = nano
what is histology used for
- examines cells and tissues
- checks for changes in structure of cells ie if cell has mutated
- can diagnose things like cancer from appearance of cells
common biopsy techniques
- surgery and then later dissection from histopathologist
- scraping ie curettes, scalpel scrapes
- sharps eg needle biopsy, pipelle (endometrial), trephine (to go through bone to get bone marrow), punch biopsy
- venepuncture ie blood smears or for haematological disease assessment
- transvascular where device travels through blood vessels to highly vascularised tissues biopsy site (eg kidney, lung, brain or heart)
why do tissues need to be fixed + state which fixatives are commonly used
fixation needs to be used in order to preserve tissues in a life-like state.
- works by cross-linking all proteins so they cannot move
- often by 10% formalin solution (buffered and dissolved in sodium chloride ie saline, to prevent osmotic damage)
- for electron microscopy, glutaraldehyde fix is often used instead
