1. Homeostasis Flashcards
Define homeostasis
Homeo=sameness and stasis=standing still
What needs to be maintained constant in the internal environment?
- Concentration of oxygen, carbon dioxide, salt and other electrolytes
- Concentration of nutrients, waste products
- pH
- Temperature
- Volume and pressure
What is a fundamental technique that the body uses to maintain homeostasis?
Feedback loops - positive and negative
What is the normal human body temperature range?
37 ± 0.5 °C.
What does the core body temperature depend on?
time of day, physical activity, time in the menstrual cycle and age
What does fluctuation in body temperature throughout the day show?
Circadian rhythm
Describe the components of a negative feedback loop
Stimulus to sensor to control to effector back to stimulus
What 4 things occur when the temperature is too hot?
- Vasodilation
- Sweating
- Pilorelaxation
- Stretching out
How does vasodilation help lower the temperature?
Arterioles dilate so more blood enters skin capillaries so more heat lost from the surface of the skin
How does sweating help lower the temperature?
Sudorific glands secrete sweat which removes heat when water changes state
What is pilorelaxation and how does it help lower the body temperature?
It is when hairs of the body lay flat- means less air trapped by the hairs so less of an insulating layer so more heat lost
How does stretching out help lower the body temperature?
By opening up, the body has a larger surface area so more heat lost
What things occur when the temperature is too cold?
- Vasoconstriction
- Shivering
- piloerection
- curling up
How does vasoconstriction help to increase the body temperature?
Arterioles get smaller to reduce blood going to the skin so less heat lost from the surface of the skin.
How does shivering help increase the body temperature?
Repaid contraction and relaxing of skeletal muscles causes heat to be produced by respiration
How does piloerection help increase the body temperature?
Hairs on skin stand up so trap a layer of insulating air so less heat lost
How does curling up increase the body temperature?
Making yourself smaller so smaller surface area so less heat lost
What are the primary thermoregulatiry effectors?
- Skin blood vessels
- Sweat glands
- Skeletal muscle
- Brown adipose tissue
What is pyrexia and what causes it?
- When a person is infected, toxins from bacteria and chemicals produced by the immune system (particularly interleukin 6; IL-6) known as pyrogens increase the set point in the hypothalamus to a higher temperature.
- This initiates heat generation through shivering and increased metabolic rate so that an increase in body temperature is achieved.
- When above 38.5°C this is known as fever (pyrexia)
How does an increases temperature help in fighting pathogen?
increase in temperature is important because at these temperatures the immune system works optimally. Increased temperature can also help to kill off microbes or stop them reproducing.
What is rigor?
Rigor- an episode of shaking or exaggerated shivering which can occur with a high fever
What triggers rigors?
Rigors are triggered by the presence of chemicals called pyrogens in the blood which are produced by white blood cells when fighting an infection.
What are the 3 steps of increasing temperature than normal?
- Fever. 38 - 40
- Heat stroke. 40-46
- Heat exhaustion. 46+
What are the symptoms of fever?
Pale sweaty skin, cramps in stomach, arms and legs
What are the symptoms of heat stroke?
Flushed dry skin, hot to the touch, strong bounding pulse
What are the symptoms of heat exhaustion?
Unconsciousness/fitting/seizure, confused/restless, headache,dizzy, uncomfortable
What are the 3 stages of decreasing temperature below normal?
- Mild hypothermia. 36-32
- Severe hypothermia. 32-28
- No vital signs. 28-
What are the signs of mild hypothermia?
Shivering, fatigue, slurred speech, confusion, forgetfulness, muscle stiffness
What are the signs of severe hypothermia?
Shivering stops, muscles become rigid, very slow and weak pulse, noticeable drowsiness, severe reduction in response levels
What are the signs of no vital signs?
Unconsciousness, dilated pupil, pulse detectable, appearance of death.
When temperature is below 28 C, what is the rule?
Not dead until warm and dead
What does pH mean?
Power of hydrogen
What is the normal pH range?
7.35-7.45
What are the 2 major organs responsible for mintaining acid base balance?
Lungs- respiratory balance
Kidneys- metabolic balance
What is it called when the pH of blood is less than 7.35?
Acidosis
What is it called when the pH of blood is greater than 7.45?
Alkalosis
What are the signs an symptoms of acidosis?
- Headaches
- Confusion
- Feeling tired
- Tremors
- Coma
What are the two types of acidosis?
- Metabolic acidosis
2. Respiratory acidosis
What causes metabolic acidosis?
caused by increased production of metabolic acids, such as lactic acid or an inability to excrete acid via the kidney
What causes respiratory acidosis?
caused by excessive buildup of carbon dioxide due to hypoventilation
What is the normal range for gastric pH?
1.5-3.5
How do antacids work?
antacids neutralise acids by virtue of their alkalinity, But also their solubility is a factor – aluminium hydroxide is MILDLY alkaline, but because it is insoluble is a good neutraliser.
What is fluid balance?
amount of water gained each day = amount of water lost to the environment.
What is intracellular fluid?
water inside cells
What is extracellular fluid?
fluid surrounding the cells
What is interstitial fluid?
fluid that surrounds cells but is outside the blood vessels
What is blood plasma?
fluid that surrounds cells but is inside the blood
What are the two fluid compartments?
Intracellular fluid an extracellular fluid
What are the two components of extracellular fluid?
Interstitial fluid and blood plasma
What percent of total body weight is fluid?
60%
What fraction of the total fluid is intracellular fluid?
2/3
What fraction of total fluid is extracellular fluid?
1/3
What percentage of extracellular fluid is interstitial fluid?
75%
What percentage of extracellular fluid is plasma?
25%
What affects the total body water of an individual?
The higher the percentage body fat, the lower the percentage of total body water
Why are there differences in total body water in males and females?
females have a lager mass of adipose tissue which is only 10% water compared to males who have a greater average muscle mass which is 75% water.
What does hypotonic mean?
The solute concentration inside cells is higher than the outside so water moves into cells - can lead to cells swelling and eventually bursting
What does isotonic mean?
The solute concentration inside the cell is equal to the concentration outside the cell so the amount of water transported into the cell is equal to the amount transported out
What does hypertonic mean?
Solute concentration inside cells is lower than the outside so water is transported out from the cell causing the cell to shrink
What is osmolarity?
Osmolarity is the concentration of a solution expressed as osmoles of solute particles per litre of solution
What is osmolality?
Osmolality is the concentration of a solution expressed as the total number of solute particles per kilogram
What is considered when calculating osmolarity?
Volume of the solution
What is considered when calculating osmolality?
Mass of the solution
What is the unit for osmolarity?
mOsm/L
What is the unit for osmolality?
mOsm/Kg
What does osmolarity depend on?
Temperature and pressure
What does osmolality depend on?
It does not depend on temperature and pressure
What is an example of negative feedback? Describe how it works
Control of blood glucose
Between which compartments can water move?
Water movements can occur between the ECF and ICF and between the subdivisions of the ECF but generally not within the ICF. Under normal circumstances, the ECF and ICF are in osmotic equilibrium so no large scale circulation occurs between the two compartments.
What determines the movement of water between the compartments?
The movement of water between compartments and across cell membranes is mainly determined by the differences in hydrostatic and osmotic pressures on either side of these barriers.
What creates hydrostatic forces?
Hydrostatic forces are created by the pumping action of the heart(which tends to push water out of the plasma)
What creates osmotic pressure?
osmotic pressures is created by the concentration of solute particles(which tends to draw water out of the interstitial fluid and into the plasma)
How do you measure osmotic pressure?
osmotic pressure can be measured from the number (concentration) of solute molecules present in a solution.
What happens if there is not 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 dies, water absorbed from brain, liver and lastly kidney and heart
What causes dehydration?
Picture
What is Capillary Plasma Oncotic Pressure
Because the capillary barrier is readily permeable to ions, the osmotic pressure within the capillary is principally determined by plasma proteins that are relatively impermeable. Therefore, instead of speaking of “osmotic” pressure, this pressure is referred to as the “oncotic” pressure or “colloid osmotic” pressure because it is generated by colloids. Albumin generates about 70% of the oncotic pressure. The greater the number of plasma proteins, the greater the oncotic pressure, and water moves into the capillaries
What is Tissue (interstitial) Oncotic Pressure
The oncotic pressure of the interstitial fluid depends on the interstitial protein concentration. The more permeable the capillary barrier is to proteins, the higher the interstitial oncotic pressure
What is the normal ph range in veins and arteries?
Veins - 7.35
Arteries 7.45
