HOMEOSTASIS

37C pH of7.35pH of7.35

0.1% bloodsugar

• Homeostasis – an equilibrium (steadystate) between an organism’s variousphysiological functions, and between theorganism and the environment.

• This is a balance in response tocontinually changing conditions in both theinternal and external environments

• Homeostasis – an equilibrium (steadystate) between an organism’s variousphysiological functions, and between theorganism and the environment.

• This is a balance in response tocontinually changing conditions in both theinternal and external environments

Steady State• achieved by self adjustment (see feedback)• death results when then balance can no longer be

maintained

dynamic equilibrium – a condition that remains stablewith fluctuation limits

• achieved by self adjustment (see feedback)• death results when then balance can no longer be

maintained

dynamic equilibrium – a condition that remains stablewith fluctuation limits

• achieved by self adjustment (see feedback)• death results when then balance can no longer be

maintained

dynamic equilibrium – a condition that remains stablewith fluctuation limits

• achieved by self adjustment (see feedback)• death results when then balance can no longer be

maintained

dynamic equilibrium – a condition that remains stablewith fluctuation limits

There are many factors that we, as organisms,must balance: ex. blood glucose, watercontent (osmotic balance), temperature,hormones, etc.

Control Systems• All homeostatic control systems have

three components:– a monitor special sensors located in the

organs of the body detect changes inhomeostasis

– a coordinating centre, receives messagefrom sensors and relays information toappropriate regulator (organ/tissue that willact to restore steady state) brain

– a regulator restores normal balance muscles and organs

• All homeostatic control systems havethree components:– a monitor special sensors located in the

organs of the body detect changes inhomeostasis

– a coordinating centre, receives messagefrom sensors and relays information toappropriate regulator (organ/tissue that willact to restore steady state) brain

– a regulator restores normal balance muscles and organs

FEEDBACKSYSTEMSMAINTAINHOMEOSTAS

IS

Components:1. Receptors2. Control

Center3. Effectors

FEEDBACKSYSTEMSMAINTAINHOMEOSTAS

IS

Components:1. Receptors2. Control

Center3. Effectors

Coordination of Body Functions

• The activity of various specialized parts ofan animal are coordinated by the twomajor systems of internal communication:

• the nervous system – involved with high-speed messages

• the endocrine system – involved in theproduction, release, and movement ofchemical messangers

• The activity of various specialized parts ofan animal are coordinated by the twomajor systems of internal communication:

• the nervous system – involved with high-speed messages

• the endocrine system – involved in theproduction, release, and movement ofchemical messangers

• All animals exhibit some coordination bychemical signals:– hormones = produced by the endocrine

system convey information between organs ofthe body

– pheromones = chemical signals used tocommunicate between different individuals

– neurotransmitters = chemical signalsbetween cells on a localized scale (over shortdistances; between neurons)

• All animals exhibit some coordination bychemical signals:– hormones = produced by the endocrine

system convey information between organs ofthe body

– pheromones = chemical signals used tocommunicate between different individuals

– neurotransmitters = chemical signalsbetween cells on a localized scale (over shortdistances; between neurons)

The Endocrine System• Has several key components:• Hormones = secreted by endocrine or neurosecretory

cells, travel into body fluids to target cells where it elicitsa specific response

• Target Cell = cell equipped to respond to the givenhormone

• Neurosecretory cells = neuron that receives signalsfrom other nerve cells and responds by releasinghormones into body fluids or into a storage organ fromwhich they are later released.

• Endocrine gland = ductless gland that secreteshormones into the body fluids for distribution through thebody

• Note: Exocrine gland = glands that produce a variety of substances (e.gsweat, mucus, digestive enzymes) and deliver their produces via ducts, areNOT part of the endocrine system.

• More on the endocrine system in chapter 8…..

• Has several key components:• Hormones = secreted by endocrine or neurosecretory

cells, travel into body fluids to target cells where it elicitsa specific response

• Target Cell = cell equipped to respond to the givenhormone

• Neurosecretory cells = neuron that receives signalsfrom other nerve cells and responds by releasinghormones into body fluids or into a storage organ fromwhich they are later released.

• Endocrine gland = ductless gland that secreteshormones into the body fluids for distribution through thebody

• Note: Exocrine gland = glands that produce a variety of substances (e.gsweat, mucus, digestive enzymes) and deliver their produces via ducts, areNOT part of the endocrine system.

• More on the endocrine system in chapter 8…..

1. Excreting Waste2. Urinary System3. Formation of Urine4. Water Balance5. Kidney Disease

Example: carbon dioxide levels Levels increased during exerciseChemical receptors in brain are stimulatedNerve cells from the brain carry impulses to muscles that increasebreathing rate.

Example: carbon dioxide levels Levels increased during exerciseChemical receptors in brain are stimulatedNerve cells from the brain carry impulses to muscles that increasebreathing rate.

A group of arteries in the neck can detect low levels ofoxygen in the blood and they send a message via a nerve tothe brain, which then relays the message to the muscles thatcontrol breathing movements.

•Because we are constantly having to fix our levels so they stay withina range, we call it dynamic equilibrium.•Mechanisms that make adjustments to bring the body back within itsacceptable range are called negative feedback systems.

• Most homeostatic control systems are negativefeedback systems. These systems preventsmall changes from becoming too large.

• A relationship in which the response is oppositeto the stimulus (or impressed change)

• The body is self correcting by the use ofnegative feedback

• Example: glucose and insulin, thermostat (pg. 336)

• Most homeostatic control systems are negativefeedback systems. These systems preventsmall changes from becoming too large.

• A relationship in which the response is oppositeto the stimulus (or impressed change)

• The body is self correcting by the use ofnegative feedback

• Example: glucose and insulin, thermostat (pg. 336)

high glucose inblood

↑ insulinproduction

Response

No heatproduced

Roomtemperaturedecreases

Set point

Toohot

Setpoint

Heaterturnedoff

Roomtemperature

increases

Toocold

Setpoint

Control center:thermostat

Heaterturnedon

Response

Heatproduced

NEGATIVEFEEDBACK

►decreasesan action

►stops whenreturn tonormal

►mosthomeostaticcontrolmechanismsare negativefeedback

NEGATIVEFEEDBACK

►decreasesan action

►stops whenreturn tonormal

►mosthomeostaticcontrolmechanismsare negativefeedback

• Positive Feedback systems: process bywhich a small effect is amplified

• A relationship in which the response isthe same as the stimulus

• Leads to instability and possibly death• Some rare limited examples:

birthing process in humans: childbirth hormone oxytocin

• Positive Feedback systems: process bywhich a small effect is amplified

• A relationship in which the response isthe same as the stimulus

• Leads to instability and possibly death• Some rare limited examples:

birthing process in humans: childbirth hormone oxytocin

POSITIVEFEEDBACK(reinforces)►increases

an action►must be

turned offby outsideevent

►decreasesan action

►could runaway =death

POSITIVEFEEDBACK(reinforces)►increases

an action►must be

turned offby outsideevent

►decreasesan action

►could runaway =death

* blood loss- ↓ B.P.- ↓ heart beat- ↓ B.P.

* blood clotting

• Decrease in progesterone ---->increase in uterinecontraction ----> release of oxytocin ---> increase instronger contractions---->baby is expelled----->contraction stop--->release of oxytocin stops

↓ progesterone contractions &oxytocin

+

+

Section 7.1 Questions, pp. 337, #1-5

Thermoregulation

•

• Thermoregulation: themaintenance of bodytemperature within a rangethat enables cells tofunction efficiently.

• Ectotherms: (reptiles etc.)rely on air temperature toregulate metabolic rates.Therefore activity isdependent onenvironment. adaptations: seekingsun, shade

• Endotherms: (mammalsetc.) maintain constantbody temp (37°C)regardless of environment.Respond to changes inenvironmental temp. byusing energy to produceheat

•

• Thermoregulation: themaintenance of bodytemperature within a rangethat enables cells tofunction efficiently.

• Ectotherms: (reptiles etc.)rely on air temperature toregulate metabolic rates.Therefore activity isdependent onenvironment. adaptations: seekingsun, shade

• Endotherms: (mammalsetc.) maintain constantbody temp (37°C)regardless of environment.Respond to changes inenvironmental temp. byusing energy to produceheat

River otter (endotherm)40

Bod

y te

mpe

ratu

re (°

C)

30

20

Relationship between body temperature & Environmentaltemperature

Largemouth bass (ectotherm)

Ambient (environmental) temperature (°C)

010 20 30 40

Bod

y te

mpe

ratu

re (°

C)

20

10

B. Modes of Heat Exchange• Organisms exchange heat by four physical

processes: conduction, convection, radiation,and evaporation Evaporation: removal heat

from surface of liquid lostas gas

Convection: transferheat by mvt air

Radiation: radiate heatbetween objects not in contact.

Conduction: direct transferheat between moleculesin contact

Convection: transferheat by mvt air

B. Balancing Heat Loss andGain

• In thermoregulation, physiological andbehavioral adjustments balance heatloss and heat gain

• 5 general adaptations in animals’thermoregulation:– Insulation– Circulatory adaptations– Cooling by evaporative heat loss– Behavioral responses– Adjusting metabolic heat production

• In thermoregulation, physiological andbehavioral adjustments balance heatloss and heat gain

• 5 general adaptations in animals’thermoregulation:– Insulation– Circulatory adaptations– Cooling by evaporative heat loss– Behavioral responses– Adjusting metabolic heat production

1. Insulation• Insulation is a major thermoregulatory

adaptation in mammals and birds• It reduces heat flow between an animal and its

environment• Examples are skin, feathers, fur, and blubber• In mammals, the integumentary system acts as

insulating material

• Insulation is a major thermoregulatoryadaptation in mammals and birds

• It reduces heat flow between an animal and itsenvironment

• Examples are skin, feathers, fur, and blubber• In mammals, the integumentary system acts as

insulating material

• Many endotherms & some ectotherms alteramount of blood flowing between the bodycore & skin

• Vasodilatation = ↑ blood flow in skin = ↑heat loss

• Vasoconstriction = ↓ blood flow in skin =↓ heat loss

2. Circulatory Adaptations• Many endotherms & some ectotherms alter

amount of blood flowing between the bodycore & skin

• Vasodilatation = ↑ blood flow in skin = ↑heat loss

• Vasoconstriction = ↓ blood flow in skin =↓ heat loss

• Many marine mammals & birds havearrangement blood vessels calledcounter current heat exchanger which areimportant for reducing heat loss

3. Cooling by Evaporative Heat Loss• Many types of animals lose heat through

evaporation of water in sweat• Panting augments the cooling effect in birds

and many mammals• Bathing moistens the skin, helping to cool

animal

• Both endotherms and ectotherms usebehavioral responses to control body temp

• Some terrestrial invertebrates have posturesthat minimize or maximize absorb solar heat

4. Behavioral Responses

More extremebehavioraladaptations =hibernation ormigration tomore suitableclimate

More extremebehavioraladaptations =hibernation ormigration tomore suitableclimate

5. Adjusting Metabolic Heat Production• Some animals can regulate body temperature

by adjusting their rate of metabolic heatproduction

• Many species of flying insects use shivering towarm up before taking flight

Preflight warmup inhawkmoth = shiver-like tohelp muscles produceenough power to take off

Preflight warmup inhawkmoth = shiver-like tohelp muscles produceenough power to take off

• Mammals regulate body temperature bynegative feedback involving severalorgan systems

• In humans, the hypothalamus (a part ofthe brain) contains nerve cells thatfunction as a thermostat

C. Feedback Mechanisms inThermoregulation

• Mammals regulate body temperature bynegative feedback involving severalorgan systems

• In humans, the hypothalamus (a part ofthe brain) contains nerve cells thatfunction as a thermostat

Stimulus PhysiologicalResponse

Adjustment

Decreasedenvironmentaltemperature

Constriction ofblood vessels inskin-hairs onbody erectshivering

Heat isconserved moreheat isgenerated byincreasedmetabolism

Constriction ofblood vessels inskin-hairs onbody erectshivering

Heat isconserved moreheat isgenerated byincreasedmetabolism

Increasedenvironmentaltemperature

Dilation of bloodvessels of skin-sweating

Heat isdissipated

Human thermostat = hypothalamus (control centre)

Responses to heat stress: (nerve messages from sensorvia hypothalamus)

• increase sweat (glands)• vasodilatation (blood vessels)Responses to cold stress: (nervemessages from sensor via hypothalamus)• smooth muscles contract• vasoconstriction (blood vessels)• hair stands on end to trap warm air near skin (follicles)

(goosebump = musclecontraction in area of hair follicle)• rhythmic skeletal musclecontraction = shivering to generate heat• Mammalian Diving ReflexSection 7.2 Questions, pp. 341, # 1-7

Responses to heat stress: (nerve messages from sensorvia hypothalamus)

• increase sweat (glands)• vasodilatation (blood vessels)Responses to cold stress: (nervemessages from sensor via hypothalamus)• smooth muscles contract• vasoconstriction (blood vessels)• hair stands on end to trap warm air near skin (follicles)

(goosebump = musclecontraction in area of hair follicle)• rhythmic skeletal musclecontraction = shivering to generate heat• Mammalian Diving ReflexSection 7.2 Questions, pp. 341, # 1-7