Homeostasis Glossary Maintain – keep up. Maintain – keep up. Constant – the same. Constant – the same. Internal – inside the body. Internal – inside

HomeostasisHomeostasis

GlossaryGlossary

Maintain – keep up.Maintain – keep up. Constant – the same.Constant – the same. Internal – inside the body.Internal – inside the body. Environment – surroundings of the body.Environment – surroundings of the body.

What is Homeostasis?What is Homeostasis?

Body cells work best if they have the Body cells work best if they have the correctcorrect TemperatureTemperature Water levelsWater levels Waste levelsWaste levels Glucose concentrationGlucose concentration

Your body has mechanisms to keep the Your body has mechanisms to keep the cells in a constant environment.cells in a constant environment.

What is Homeostasis?What is Homeostasis?

The maintenance of a constant The maintenance of a constant environment in the body.environment in the body.

The ability or tendency of an organism or The ability or tendency of an organism or cell to maintain internal equilibrium by cell to maintain internal equilibrium by adjusting its physiological processes.adjusting its physiological processes. Physiology: is the study of the mechanical, Physiology: is the study of the mechanical,

physical, and biochemical functions of living physical, and biochemical functions of living organismsorganisms

*Our bodies attempt to maintain an *Our bodies attempt to maintain an internal balance called internal balance called HOMEOSTASISHOMEOSTASIS. . There are many conditions in which life There are many conditions in which life processes are limited:processes are limited:

Eg. Most enzymes in our bodies work Eg. Most enzymes in our bodies work best at best at 3737ººCC..

pH of blood is maintained between 7.35 pH of blood is maintained between 7.35 and 7.45. (recall – 7 is neutral, blood is and 7.45. (recall – 7 is neutral, blood is slightly basic) slightly basic) Too low, Too low, acidosisacidosis Too high, Too high, alkalosisalkalosis

*MAJOR HOMEOSTATIC ORGAN *MAJOR HOMEOSTATIC ORGAN

Hypothalamus (brain) = HomeostasisHypothalamus (brain) = Homeostasis

The main function of the hypothalamus is The main function of the hypothalamus is homeostasis, or maintaining the body's homeostasis, or maintaining the body's status quo. status quo.

*MAJOR HOMEOSTATIC ORGAN *MAJOR HOMEOSTATIC ORGAN The following factors are held to a precise The following factors are held to a precise

value called the set-point:value called the set-point: blood pressureblood pressure, , blood sugarblood sugar body body temperaturetemperature, , fluid and electrolyte balancefluid and electrolyte balance, , and and body weightbody weight

Although this set-point can migrate over Although this set-point can migrate over time, from day to day it is remarkably time, from day to day it is remarkably fixed.fixed.

Receptors and EffectorsReceptors and Effectors

*To achieve this task, the hypothalamus *To achieve this task, the hypothalamus must:must: nerve fibers/endings called receptors/sensors nerve fibers/endings called receptors/sensors

receive inputs about the state of the bodyreceive inputs about the state of the body

effectors are nerve endings that respond to effectors are nerve endings that respond to

changes in nerve fibers changes in nerve fibers i.e. if anything drifts out of whack.i.e. if anything drifts out of whack.

i.e. Feedback Loop (more about this later)i.e. Feedback Loop (more about this later)

Intrinsic ReceptorsIntrinsic Receptors

*The hypothalamus has some intrinsic *The hypothalamus has some intrinsic receptors, including:receptors, including: thermoreceptorsthermoreceptors (sense degree of hotness (sense degree of hotness

and coldness) and and coldness) and

osmoreceptorsosmoreceptors (sense electrolyte balance).(sense electrolyte balance).

The hypothalamus sends signals to The hypothalamus sends signals to effectors (nerve endings that respond) effectors (nerve endings that respond) which can control heart rate, which can control heart rate, vasoconstriction, digestion, sweating, etc.vasoconstriction, digestion, sweating, etc.

*The Brain*The Brain

*We will concentrate on FOUR *We will concentrate on FOUR homeostatic processes:homeostatic processes:

1.1. thermoregulation thermoregulation

2.2. osmoregulationosmoregulation

3.3. blood glucose managementblood glucose management

4.4. waste managementwaste management

The first two and last two of these The first two and last two of these

homeostatic processes are closely homeostatic processes are closely interrelated.interrelated.

*Thermoregulation:*Thermoregulation: The The process of keeping the body at a process of keeping the body at a

constant temperatureconstant temperature.. We are We are homiothermshomiotherms (warm blooded). (warm blooded).

Heat is constantly produced through Heat is constantly produced through metabolism (metabolism (25%25% remains in the body) and remains in the body) and lost (lost (75%75%))

If your body is in a hot or cold environment If your body is in a hot or cold environment your body temperature is 37your body temperature is 37ººC.C.

*Thermoregulation:*Thermoregulation:

Processes affected by temp.Processes affected by temp. enzyme functionenzyme function, , disease controldisease control, , metabolic rate metabolic rate

Body heat depends on Body heat depends on metabolic ratemetabolic rate (how the body uses nutrients, activity)(how the body uses nutrients, activity) At rest muscles produce up to At rest muscles produce up to 30%30% of our of our

body heat (brain)body heat (brain) During exercise, our muscles produce During exercise, our muscles produce 40X40X

more body heat than other tissues (only 25% more body heat than other tissues (only 25% efficient)efficient)

Normal body temp.Normal body temp. 98.6ºF or 98.6ºF or 3737ººCC

Controlling body temperatureControlling body temperature

Animals with a large surface area compared Animals with a large surface area compared to their volume will lose heat faster than to their volume will lose heat faster than animals with a small surface area.animals with a small surface area.

Volume = _______

Surface area = ______

Volume : Surface area ratio = ___________

Volume = _______

Surface area = ______

Volume : Surface area ratio = ___________


Volume : Surface area

1:6


1:5

For every 1 unit of heat made, heat is lost out of 6 sides

For every 1 unit of heat made, heat is lost out of 5 sides



1:6


1:5

The bigger the Volume : Surface Area ratio is, the faster heat will be lost.

Penguins huddling to keep warmPenguins huddling to keep warm

THERMAL RANGESTHERMAL RANGESProfessor Alan Hedge, Cornell University, January 2007Professor Alan Hedge, Cornell University, January 2007

SKIN (Shell)SKIN (Shell) >45°C (>113°F) Burns>45°C (>113°F) Burns 42°C (108°F) Pain42°C (108°F) Pain 40°C (104°F) Uncomfortably hot 40°C (104°F) Uncomfortably hot 25°C (77°F) Uncomfortably cold25°C (77°F) Uncomfortably cold 5°C (41°F) Numbness5°C (41°F) Numbness 0°C (<32°F) Frostbite0°C (<32°F) Frostbite -0.6°C (<31°F) Skin freezes-0.6°C (<31°F) Skin freezes

BODY (Core)BODY (Core) >42°C (108°F) Fatal>42°C (108°F) Fatal 41°C (106°F) Coma, convulsions41°C (106°F) Coma, convulsions 39.5°C (103°F) Upper acceptable limit - 39.5°C (103°F) Upper acceptable limit -

drowsinessdrowsiness 37°C (98.6°F) normal37°C (98.6°F) normal 35.5°C (96°F) Lower acceptable limit - mental 35.5°C (96°F) Lower acceptable limit - mental

dullnessdullness 34.5°C (94°F) Shivering diminishes - extreme 34.5°C (94°F) Shivering diminishes - extreme

mental slownessmental slowness 33°C (91°F) Coma33°C (91°F) Coma <33°C (91°F) Deep Coma. Death<33°C (91°F) Deep Coma. Death 27°C (81°F) Heart stops. Death27°C (81°F) Heart stops. Death

What mechanisms are there to cool What mechanisms are there to cool the body down?the body down?

1.1. SweatingSweating When your body is hot, sweat glands under When your body is hot, sweat glands under

the skin are stimulated to release sweat.the skin are stimulated to release sweat. The liquid sweat turns into a gas (it The liquid sweat turns into a gas (it

evaporates)evaporates) To do this, it needs heat.To do this, it needs heat. It gets that heat from your skin.It gets that heat from your skin. As your skin loses heat, it cools down.As your skin loses heat, it cools down.

SweatingSweating

The skin

What mechanisms are there to What mechanisms are there to coolcool the body down?the body down?

2.2. Vasodilation/VasoconstrictionVasodilation/Vasoconstriction Your blood carries most of the heat energy Your blood carries most of the heat energy

around your body.around your body. There are There are capillaries underneath your skin capillaries underneath your skin

that can swell/dilate if you get too hot.that can swell/dilate if you get too hot. This brings the blood closer to the surface This brings the blood closer to the surface

of the skin so more heat can be lost.of the skin so more heat can be lost. This is why you look red when you are hot!This is why you look red when you are hot!

If the temperature rises, the blood vessel dilates (gets bigger).

This means more heat is lost from the surface of the skin

What mechanisms are there to What mechanisms are there to warmwarm the body up?the body up?

1.1. VasoconstrictionVasoconstriction This is the opposite of vasodilationThis is the opposite of vasodilation The The capillaries underneath your skin get capillaries underneath your skin get

constricted/shrink (shut off).constricted/shrink (shut off). This takes the blood away from the surface This takes the blood away from the surface

of the skin so less heat can be lost.of the skin so less heat can be lost.

If the temperature falls, the blood vessel constricts (gets shut off).

This means less heat is lost from the surface of the skin

What mechanisms are there to What mechanisms are there to warmwarm the body up?the body up?

2.2. PiloerectionPiloerection This is when tiny muscles in the skin contract, This is when tiny muscles in the skin contract,

causing the causing the hairs on your skin “stand up” .hairs on your skin “stand up” . It is sometimes called “goose bumps” or It is sometimes called “goose bumps” or

“chicken skin”!“chicken skin”! The hairs trap a layer of air next to the skin The hairs trap a layer of air next to the skin

which is then warmed by the body heatwhich is then warmed by the body heat The air becomes an insulating layer.The air becomes an insulating layer.

OSMOREGULATION:OSMOREGULATION:Water RegulationWater Regulation

Water makes up ~Water makes up ~60%60% of total body of total body composition, of this. composition, of this.

Water is constantly required and removed.Water is constantly required and removed. 73%73% of lean body mass ( of lean body mass (LBMLBM) is composed of ) is composed of

waterwater essential for survivalessential for survival required for all cell functionsrequired for all cell functions used for thermoregulationused for thermoregulation** major component of blood volumemajor component of blood volume

OSMOREGULATIONOSMOREGULATION

Not enough water in the body – Not enough water in the body – dehydration.dehydration. In dehydrated states, water is lost from the In dehydrated states, water is lost from the

blood, electrolyte imbalanceblood, electrolyte imbalance Too much water in the body – Too much water in the body – edemaedema

(water retention swelling), electrolyte (water retention swelling), electrolyte imbalanceimbalance

Homeostasis of Heat and WaterHomeostasis of Heat and Water

Body temp. monitored by the Body temp. monitored by the hypothalamus. hypothalamus.

Skin surfaceSkin surface: : 32 000 heat receptors/sq. inch32 000 heat receptors/sq. inch concentrated in concentrated in fingertipsfingertips, nose, elbows, , nose, elbows,

upper lip, & chest. upper lip, & chest. BrainBrain and blood vessels contain the and blood vessels contain the

thermal receptors for sensing thermal receptors for sensing core bodycore body temperature temperature

Heat Loss Mechanisms at RestHeat Loss Mechanisms at Rest

RadiationRadiation – – at rest 60% of heat loss from at rest 60% of heat loss from a nude bodya nude body

ConvectionConvection: air movement past body. : air movement past body. Two ways, natural (air molecules) and Two ways, natural (air molecules) and forced (eg. Fan) (up to 30% lost through forced (eg. Fan) (up to 30% lost through head and neck)head and neck)

EvaporationEvaporation: : water losswater loss through skin through skin 15% of 15% of heat lossheat loss

Inhalation/ExhalationInhalation/Exhalation: 10% : 10% loss of heatloss of heat and and water losswater loss (exhalation) (exhalation)

ConductionConduction: skin contact with objects : skin contact with objects such as chairs, floors, etc. about 3%such as chairs, floors, etc. about 3%

Excretion of urine and fecesExcretion of urine and feces, , both both water water (major component, 400 – 800 (major component, 400 – 800 mL/event)mL/event) and heat loss and heat loss (3%)(3%) Winter survivalWinter survival

Heat Loss Mechanisms at RestHeat Loss Mechanisms at Rest

SWEAT BASICS:SWEAT BASICS:

Each sq. inch of skin has 32 000 nerve Each sq. inch of skin has 32 000 nerve fibers, 98 sebaceous glands & ~650 sweat fibers, 98 sebaceous glands & ~650 sweat glandsglands

Heat and emotions affect sweating Heat and emotions affect sweating Emotional tears are more toxic - healingEmotional tears are more toxic - healing

Men sweat 50% more than women. Older Men sweat 50% more than women. Older people (esp males) and children sweat people (esp males) and children sweat ineffectivelyineffectively


Eccrine glands Eccrine glands produce sweat produce sweat 99% water99% water NaClNaCl Other electrolytesOther electrolytes traces of urea, lactic acid, traces of urea, lactic acid,

fatty acids and proteinsfatty acids and proteins Colorless and odorlessColorless and odorless

http://www.sweathelp.org/English/PFF_Hyperhidrosis_Overview.asp


Eccrine glands produce Eccrine glands produce between between 200 ml – 10 L per day 200 ml – 10 L per day depending on depending on

activity level and climateactivity level and climate 200 ml/hr at room temperature, and up to 1.5 200 ml/hr at room temperature, and up to 1.5

L/h in extreme heat climatesL/h in extreme heat climates The greatest number of sweat glands are The greatest number of sweat glands are

on the forehead, neck, back of hand, on the forehead, neck, back of hand, forearm, back and front trunk; lowest on forearm, back and front trunk; lowest on thighs, soles of feet, & palms of the thighs, soles of feet, & palms of the hands.hands.

Sweat GlandsSweat Glands

http://www.nature.com/milestones/skinbio/images/subject_index_02.gifhttp://www.nature.com/milestones/skinbio/images/subject_index_02.gif

E – Epidermal Layer

D - Dermis

H – Hair Follicles

G – Sweat/Eccrine Glands

S – Sebaceous Glands

http://vrc.belfastinstitute.ac.uk/resources/skin/skin.htm

Hair FollicleHair Follicle


Apocrine gland/ducts (sebaceous Apocrine gland/ducts (sebaceous glands) glands) Secrete protein, oils and waterSecrete protein, oils and water. These open . These open

onto hair folliclesonto hair follicles Highest density in underarms, nipples, pubic Highest density in underarms, nipples, pubic

area, lips, chin and head, eyelids, outer ear.area, lips, chin and head, eyelids, outer ear. Bacteria decompose apocrine secretions Bacteria decompose apocrine secretions

(within an hour) and create individually (within an hour) and create individually characteristic “body odor” (BO)characteristic “body odor” (BO)

Sweat & ExerciseSweat & Exercise

High intensity exercises or exercises High intensity exercises or exercises lasting more than 1 h can result in 2.0 L/h lasting more than 1 h can result in 2.0 L/h of water loss (of water loss (usually 1.0 L/h is more usually 1.0 L/h is more commoncommon).).

This depends on environmental This depends on environmental conditions, humidity, clothing, intensity, conditions, humidity, clothing, intensity, fitness level, and acclimation to climate.fitness level, and acclimation to climate.

Sweat & ExerciseSweat & Exercise 24 h prior to major activity:24 h prior to major activity:

consume fruits, veggies, and carbs to consume fruits, veggies, and carbs to promote hydration.promote hydration.

Avoid, caffeines, alcohols (which promote Avoid, caffeines, alcohols (which promote dehydration).dehydration).

Sweat & ExerciseSweat & Exercise 2 h before - 2 h before - 2 cups of water 2 cups of water (not juice/pop)(not juice/pop) during – more water about every 15 during – more water about every 15

minutes. minutes. After (if over 1 hr) – After (if over 1 hr) – replace electrolytes replace electrolytes

(ie Gatorade which balances sugars, NaCl, (ie Gatorade which balances sugars, NaCl, and K ions lost through sweating).and K ions lost through sweating).

Make your own – salt, fruit juice, waterMake your own – salt, fruit juice, water

Other ways we lose heat and water:Other ways we lose heat and water:

Expectoration (cough)Expectoration (cough) Sternutation (sneeze)Sternutation (sneeze)SalivationSalivation EjaculationEjaculationMenstruationMenstruation Parturition (Birth)Parturition (Birth)LactationLactation Epilation (hair loss)Epilation (hair loss)Lacrimation (tears)Lacrimation (tears) Eructation (burps)Eructation (burps)FlatulationFlatulation RegurgitationRegurgitationSpontaneous exanguination (blood loss)Spontaneous exanguination (blood loss)

Sweat Gland Video clip (20 sec) Sweat Gland Video clip (20 sec) http://www.britannica.com/EBchecked/topic/453087/perspiration

What Causes Prickly HeatWhat Causes Prickly Heat

Negative Feedback LoopNegative Feedback Loop

Control Center (Hypothalamus)Control Center (Hypothalamus)

Sensor/Receptor:Sensor/Receptor: Effector:Effector:

Change:Change: Change:Change:

Cause:Cause:

Normal Condition:Normal Condition:

http://wps.aw.com/bc_martini_eap_5/105/27046/6923809.cw/index.html

Controlling Glucose levelsControlling Glucose levels Your Your cells also need an exact level of cells also need an exact level of

glucose in the bloodglucose in the blood. . Excess glucose gets turned into glycogen Excess glucose gets turned into glycogen

in the liverin the liver Regulated by two pancreatic hormones:Regulated by two pancreatic hormones:

InsulinInsulin GlucagonGlucagon

http://dtc.ucsf.edu/types-of-diabetes/type1/treatment-of-type-1-diabetes/how-the-body-processes-sugar/controlling-blood-sugar/

Too much glucose in the blood – Insulin converts some of it to glycogen

Glycogen

Insulin

Glucose in the blood

Not enough glucose in the blood – glucagon converts some glycogen into glucose.

Glycogen

Glucagon


DiabetesDiabetes

Some people do not produce enough Some people do not produce enough insulin.insulin.

When they eat food, the glucose levels in When they eat food, the glucose levels in their blood cannot be reducedtheir blood cannot be reduced..

This condition is known as DIABETES.This condition is known as DIABETES. Diabetics sometimes have to inject insulin Diabetics sometimes have to inject insulin

into their blood. They have to be careful of into their blood. They have to be careful of their diet.their diet.

Time

Glucose Concentration

Meal eaten

Insulin is produced and glucose levels fall to normal again.

Glucose levels rise after a meal.

Normal

Time

Glucose Concentration

Meal eaten

Insulin is not produced so glucose levels stay high

Glucose levels rise after a meal.

Diabetic

The glucose in the blood increases.

Glycogen

Insulin


But there is no insulin to convert it into glycogen.

Glucose concentration rises to dangerous levels.

Liver Glycogen

Blood Glucose

InsulinGlucagon

Blood Sugar Feedback LoopBlood Sugar Feedback Loop

http://dtc.ucsf.edu/types-of-diabetes/type1/treatment-of-type-1-diabetes/how-the-body-processes-sugar/the-liver-blood-sugar/

OsmoregulationOsmoregulation Control of water levelsControl of water levels Carried out by the KIDNEYS.Carried out by the KIDNEYS. Closely linked to the excretion of urea.Closely linked to the excretion of urea.

Waste product made when the LIVER breaks Waste product made when the LIVER breaks down excess proteinsdown excess proteins Why might you have to get up to go the washroom Why might you have to get up to go the washroom

at night if you had a late night steak?at night if you had a late night steak? Contains Nitrogen.Contains Nitrogen.

The kidneysThe kidneys

• ““Cleans” the blood of waste products Cleans” the blood of waste products • Controls water retentionControls water retention• Waste products and water make up urineWaste products and water make up urine

• excreted via the ureter.excreted via the ureter.• ““Dirty” blood enters the kidney through Dirty” blood enters the kidney through

renal artery and exits through renal vein renal artery and exits through renal vein • Several things happen to clean the blood...Several things happen to clean the blood...

Blood enters the tubule area in a capillary.

The capillary forms a small “knot” near the kidney tubule (glomerulus – more about this later).

The blood is filtered so all the small particles go into the tubule.

The capillary then carries on to run next to the tubule.

1. Filtration

The kidney tubule now contains lots of blood components including:

Glucose:Ions:Water:Urea:

2. Reabsorb sugar

The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

2. Reabsorb sugar

The body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.

3. Reabsorb water

Water and ions are the next to be absorbed. It depends on how much is needed by the body.

3. Reabsorb water

Water and ions are the next to be absorbed. It depends on how much is needed by the body.

Reabsorbing waterReabsorbing water

If you have too little water in your blood, you will produce very concentrated urine.

(very little water in it because most was reabsorbed)

If you have too much water in your blood, you will produce very dilute urine.

(lots of water in it)

5. Excrete the waste

Everything that is left in the kidney tubule is waste:

•All the urea•Excess water

This waste is called urine. It is excreted via the ureter and is stored in the bladder.

The “clean” blood leaves the kidney in the renal vein.

Renal vein

Ureter

Summary of urine productionSummary of urine production

Urea is a waste product made in the Urea is a waste product made in the LIVER.LIVER. Water content of the body is controlled in Water content of the body is controlled in

the the KIDNEYS.KIDNEYS. Urea, water and other waste makes up Urea, water and other waste makes up

URINEURINE.. Urine travels down the Urine travels down the URETERURETER and is and is

stored in the stored in the BLADDER.BLADDER. Urine is excreted through the Urine is excreted through the URETHRAURETHRA..

Documents

Homeostasis Glossary Maintain – keep up. Maintain – keep up. Constant – the same. Constant – the same. Internal – inside the body. Internal – inside