Homeostasis Flashcards
Define Homeostasis
“the ability or tendency of a living organism, cell, or tissue to keep the conditions inside it the same despite any changes in the conditions around it, or maintaining a state of internal balance”
“Homeo” and “Stasis” Meaning
Homeostasis is defined as:
Homeo = sameness and stasis = standing still
What needs to be maintained constant in the internal Environment (6)
- Gases: oxygen, carbon dioxide
- Nutrients, glucose, amino acids, electrolytes
- Waste products: ammonia, water
- Temperature (for enzymes)
- pH
- Water (volume and pressure) - Leads to explosion of cells
What technique is used to maintain Homeostasis
(Posative and Negative) Feedback loops
what are the 4 stages of the feedback loop
Stimulus - Sensor - Control Centre - Effector
Difference between Positive and Negative Feedback loop
Positive feedback loops enhance or amplify changes; this tends to move a system away from its equilibrium state and make it more unstable. Negative feedbacks tend to dampen or buffer changes; this tends to hold a system to some equilibrium state making it more stable.
Positive increases Stimulus
Negative Reduced Stimulus
What is the core Body Temp
Stated as 37 ± 0.5 °C (source NHS)
5 ways of Measuring Temperature, and how to use
- Infra-red skin thermometer - Point it at head
- Tympanic thermometer - goes in the inner ear
- Temporal film - Strip that changes colour ( goes on head )
- Oral/rectal/axillary thermometer - Goes in the Armpit
- Traditional - Tube Filled With mercury (Dangerous as it may break)
What feedback loop controls temperature Change
Negative Feedback loop
What Happens when it gets Too HOT (4)
- Vasodilation
Arterioles dilate (Enlarge) so more blood can go to skin capillaries and heat is lost - Sweating
Sudorific Glands Secrete Sweat which removes heat when water changes state - Pilorelaxation
The Hair flattens - Streching Out
Increases surface area by opening up body
What happens when is gets Too COLD (4)
- Vasoconstriction
Arterioles get smaller and reduce blood going to the skin - Shivering
Rapid contraction and relaxing of skeletal muscle muscles. The heat is produced by respiration. - Piloerection
Hairs on Skin Stand up - Curling Up
Smaller SA for less heat loss
The function of the Hypothalamus
Is the Control Centre and the Sensor along with Skin
Effectors for Temperature Control (5)
- Muscles
- Blood Vessels
- Hairs on skin
- Fat - babies have brown fat
- Sweat glands
What is Heat Exhaustion and what Symptoms
(>40°C) Unconsciousness/fitting/seizures, confused/restless Headache, dizzy, uncomfortable
What is Heat Stroke and what Symptoms
(> 40°C) Flushed dry skin, hot to the touch, strong bounding pulse
What is Fever and what Symptoms
(>38°C) Pale sweaty skin, cramps in stomach, arms and legs
Normal Temps
(36.5-37.5°C) Normal core body temperature
Mild Hypothermia and what symptoms
(32.1-35°C) Shivering, Fatigue, Slurred speech, Confusion Forgetfulness, muscle stiffness
Severe Hypothermia and what symptoms
(28.0- 32.0°C) Shivering stops, muscles become rigid, very slow and weak pulse
Noticeable drowsiness
No vital signs and what symptoms
Severe reduction in response levels
Unconsciousness, dilated pupils, pulse undetectable Appearance of death
NB Below 28°C = Not dead UNTIL WARM AND DEAD!
What is the normal PH
Ph 7.35 - 7.45
What is the Gastric PH
Between 1.5 and 3.5
What can happen if gastric acid gets into the oesophagus
If gastric acid gets into the oesophagus can cause severe problems (oesophagitis, stricture). This is the closing of the oesophagus
What happens if the stomach loses its mucus protection
If the stomach loses its protection (mucus) can lead to gastric ulceration and perforation.
What are the Limits to human Tissue survival PH
The limits of human tissue survival are from pH 6.8 to 7.8
What is the relationship between pH and [H+]
A change in [H+] by a factor of 2 causes a pH change of 0.3
If you remember that:
at pH 7.4 the [H+] is 40 nM and a pH change of 0.3 either
doubles or halves [H+] at many other pH values
Where do we get Blood sample
Arterial Blood Gas, (Analysis of pH and gases in an arterial blood sample)
What is the buffering system for ICF (2)
Phosphate buffer System and protein buffer system
What is the buffering system for the ECF (2)
Carbonic acid - Bicarbonate buffer system
and protein buffer system
what do protein buffer systems include (3)
Haemoglobin Buffer system (RBC only)
Amino Acid Buffer System (all proteins)
Plasma Protein buffers
how to neutralise acids
Clinical relevance:
* antacids neutralise acids
* solubility is a factor
aluminium hydroxide is MILDLY alkaline, but insoluble so is a good acid neutraliser
What percentaged of our body is water
60 %
Split between intra and extra cellular water
INTRA = 1/3 EXTRA = 2/3
how much water is needed each day
Aprox 6-8 cups water
2.5 litres of FLUID
from Extra Cellular Fluid how is the eater split
75 % interstitial fluid
25 % plasma
what happens if you don’t have the right water level
- Not enough – dehydration and cell, tissue, organism death
- Too much – toxicity, metabolic failure and cell, tissue, organism death
How Does Total Body Water vary Between Male Female and Infant
Infant - Highest at 70 % normal
Male - Middle at 60 % normal
Female - Lowest at 50 % normal
How does total body water vary between normal obese and lean
Lean - Highest
Normal - Middle
Obese - Lowest
Iso, Hypo and Hyper definition
- Iso = the same amount of water on both sides of the plasma membrane
- Hypo = more water outside the cell
- Hyper = less water outside the cell
what is osmosis
The movement of water is always down its concentration gradient by diffusion – process is called osmosis
What is OSMOLALITY
- It is a function of the
concentration of particles
in solution (expressed in
milliOsmoles
(mOsm/kg))
Osmolality – important clinical measurement how to calculate them
* Sodium is 140 mmol/L
* Potassium is 5 mmol/L
* Urea is 5 mmol/L
* Glucose is 5 mmol/L
Total = 300mOsm/kg
sodium and potassium associate with chloride ions thus double as
* Sodium is 140 mmol/L + 140 cl -
* Potassium is 5 mmol/L + 5 cl -
what happens if there isn’t enough water
- Cells and tissues initially absorb water from interstitial space
- Then from each other (sacrifice of cells)
- Then as tissues die, water absorbed from
organs - Then as organs die, water absorbed from brain, liver and lastly kidney and heart
What happens if there is TOO much water
- Osmotic pressure high
- Cells absorb water and swell
- Enzyme and proteins stop working * Cells keep swelling until they burst
clinical importance - how to help when too much water
- Patients need isotonic solutions
- i.e. IV drips need physiological saline concentrations (0.9% NaCl)
What is the Aquaporin
Aquaporins (AQP) are integral membrane proteins that serve as channels in the transfer of water, and in some cases, small solutes across the membrane.
Why do different aquaporin isoforms exist
Different aquaporin protein isoforms exist often on different sides of cells have different affinities for water -
some slow some fast
* Allows for discrete water flow
how does glycerol affect water flow
different amount if glycerol in bilayer,
a lot pulls open channel allowing water to flow in
What is Oedema
Oedema is a build-up of fluid in the body which causes the affected tissue to become swollen
When does oedema occur
Hydrostatic pressure>osmotic pressure
what is peripheral oedema
Peripheral oedema is commonly called ‘swollen ankles’ or ‘ankle
swelling’, resulting from the retention of fluid.
what is albumen
protein found in blood that creates oncotic pressure
Why do you get Oedema from liver failure?
Patients with liver failure cant produce Albumen thus capillaries are more likely to leak
Why do you get Oedema with lymphatic system failure
Water leaked from capillaries is usually picked by the lymphatic system and returned to bloodstream, without it water is not picked and thus cell starts to swell.
what are fenestrations
small gaps within capillaries
what happens when you damage fenestrations
Damage from a burn, crash etc causes fenestrations to enlarge thus albumen can leak out, albumen sucks out water with them, ( oncotic pressure goes outside bloodstream) , which causes swelling , and less 02 to cells
