1. HOMEOSTASIS
pH of
7.35
37C
0.1% blood
sugar

2. Homeostasis and Control Systems
Homeostasis – an equilibrium (steady state) between an organism’s various physiological functions, and between the organism and the environment.
This is a balance in response to continually changing conditions in both the internal and external environments

3. Steady State achieved by self adjustment (see feedback)
death results when then balance can no longer be maintained
dynamic equilibrium – a condition that remains stable with fluctuation limits
There are many factors that we, as organisms, must balance:  ex. blood glucose, water content (osmotic balance), temperature, hormones, etc.

4. Control Systems All homeostatic control systems have three components:
a monitor  special sensors located in the organs of the body detect changes in homeostasis
a coordinating centre,  receives message from sensors and relays information to appropriate regulator (organ/tissue that will act to restore steady state)  brain
a regulator  restores normal balance  muscles and organs

5. FEEDBACK SYSTEMS MAINTAIN HOMEOSTASIS Components: 1. Receptors
2. Control Center
3. Effectors
NEED TO KNOW THIS!!!
Have receptors all over our body in every tissue; collect data constantly 5

6. Coordination of Body Functions
The activity of various specialized parts of an animal are coordinated by the two major systems of internal communication:
the nervous system – involved with high-speed messages
the endocrine system – involved in the production, release, and movement of chemical messangers

7. All animals exhibit some coordination by chemical signals:
hormones = produced by the endocrine system convey information between organs of the body
pheromones = chemical signals used to communicate between different individuals
neurotransmitters = chemical signals between cells on a localized scale (over short distances; between neurons)

8. The Endocrine System Has several key components:
Hormones = secreted by endocrine or neurosecretory cells, travel into body fluids to target cells where it elicits a specific response
Target Cell = cell equipped to respond to the given hormone
Neurosecretory cells = neuron that receives signals from other nerve cells and responds by releasing hormones into body fluids or into a storage organ from which they are later released.
Endocrine gland = ductless gland that secretes hormones into the body fluids for distribution through the body
Note: Exocrine gland = glands that produce a variety of substances (e.g sweat, mucus, digestive enzymes) and deliver their produces via ducts, are NOT part of the endocrine system.
More on the endocrine system in chapter 8…..

9. Excreting Waste Urinary System Formation of Urine Water Balance
Kidney Disease
Example: carbon dioxide levels  Levels increased during exercise
Chemical receptors in brain are stimulated
Nerve cells from the brain carry impulses to muscles that increase breathing rate.
A group of arteries in the neck can detect low levels of oxygen in the blood and they send a message via a nerve to the brain, which then relays the message to the muscles that control breathing movements.
Because we are constantly having to fix our levels so they stay within a range, we call it dynamic equilibrium.
Mechanisms that make adjustments to bring the body back within its acceptable range are called negative feedback systems.

10. The body is self correcting by the use of negative feedback
Most homeostatic control systems are negative feedback systems. These systems prevent small changes from becoming too large.
A relationship in which the response is opposite to the stimulus (or impressed change)
The body is self correcting by the use of negative feedback
Example: glucose and insulin, thermostat (pg. 336)
high glucose in blood
↑ insulin production

11. Response No heat produced Heater turned off Room temperature decreases
Set
point
Too
hot
Set point
Set
point
Too
cold
Control center:
thermostat
Study this on your own
Room
temperature
increases
Heater
turned on
Response
Heat
produced 11

12. NEGATIVE FEEDBACK ►decreases an action ►stops when return to normal
►most homeostatic control mechanisms are negative feedback 12

13. Positive Feedback systems: process by which a small effect is amplified
A relationship in which the response is the same as the stimulus
Leads to instability and possibly death
Some rare limited examples:
birthing process in humans: childbirth  hormone oxytocin

14. ►must be turned off by outside event
POSITIVE
FEEDBACK
(reinforces)
►increases
an action
►must be turned off by outside event
►decreases
►could run away = death
* blood loss
- ↓ B.P.
- ↓ heart beat
* blood clotting 14

15. Decrease in progesterone ---->increase in uterine contraction ----> release of oxytocin ---> increase in stronger contractions---->baby is expelled----->contraction stop--->release of oxytocin stops
↓ progesterone
contractions & oxytocin +
Section 7.1 Questions, pp. 337, #1-5

16. Thermoregulation
Thermoregulation: the maintenance of body temperature within a range that enables cells to function efficiently.
Ectotherms: (reptiles etc.) rely on air temperature to regulate metabolic rates. Therefore activity is dependent on environment.
 adaptations: seeking sun, shade
Endotherms: (mammals etc.) maintain constant body temp (37°C) regardless of environment. Respond to changes in environmental temp. by using energy to produce heat
Conduction: direct transfer of thermal motion(heat) between molecules of the environment and those of the body surface
Convection: transfer of heat by the movement of air or liquid past the surface of a body
Radiation: the emission of electromagnetic waves produced by all objects warmer than absolute zero  transfer heat between objects that are not in direct contact
Evaporation: the loss of heat from the surface of a liquid that is losing some of its molecules as gas
Endotherms generally consume much more food than ectotherms of equivalent size.

17. Relationship between body temperature & Environmental temperature40
River otter (endotherm) 30
Body temperature (°C) 20
Largemouth bass (ectotherm) 10 10 20 30 40
Ambient (environmental) temperature (°C) 17

18. B. Modes of Heat Exchange
Organisms exchange heat by four physical processes: conduction, convection, radiation, and evaporation
Radiation: radiate heat
between objects not in contact.
Evaporation: removal heat
from surface of liquid lost
as gas
Convection: transfer
heat by mvt air
Conduction: direct transfer
heat between molecules
in contact 18

19. B. Balancing Heat Loss and Gain
In thermoregulation, physiological and behavioral adjustments balance heat loss and heat gain
5 general adaptations in animals’ thermoregulation:
Insulation
Circulatory adaptations
Cooling by evaporative heat loss
Behavioral responses
Adjusting metabolic heat production 19

20. 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
This is how we regulate our heat 20

21. 2. Circulatory Adaptations
Many endotherms & some ectotherms alter amount of blood flowing between the body core & skin
Vasodilatation = ↑ blood flow in skin = ↑ heat loss
Vasoconstriction = ↓ blood flow in skin =
↓ heat loss
Like when we work out and our faces get red; our blood is flowing faster and our vessels are expanding to let off more heat. 21

22. important for reducing heat loss
Many marine mammals & birds have arrangement blood vessels called counter current heat exchanger which are
important for reducing heat loss 22

23. 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 23

24. 4. Behavioral Responses
Both endotherms and ectotherms use behavioral responses to control body temp
Some terrestrial invertebrates have postures that minimize or maximize absorb solar heat
More extreme behavioral adaptations = hibernation or migration to more suitable climate
Like when we shiver and tense our muscles when we are cold. 24

25. 5. Adjusting Metabolic Heat Production
Some animals can regulate body temperature by adjusting their rate of metabolic heat production
Many species of flying insects use shivering to warm up before taking flight
Preflight warmup in hawkmoth = shiver-like to help muscles produce enough power to take off 25

26. C. Feedback Mechanisms in Thermoregulation
Mammals regulate body temperature by negative feedback involving several organ systems
In humans, the hypothalamus (a part of the brain) contains nerve cells that function as a thermostat 26

27. Physiological Response Adjustment Decreased environmental temperature
Stimulus
Physiological Response
Adjustment
Decreased environmental temperature
Constriction of blood vessels in skin-hairs on body erect shivering
Heat is conserved more heat is generated by increased metabolism
Increased environmental temperature
Dilation of blood vessels of skin-sweating
Heat is dissipated
Vasodilation/Vasoconstriction/ Counter-current heat exchange

28. 28

29. Human thermostat = hypothalamus (control centre)

30. increase sweat (glands) vasodilatation (blood vessels)
Responses to heat stress: (nerve messages from sensor via hypothalamus)
increase sweat (glands)
vasodilatation (blood vessels)
Responses to cold stress: (nerve
messages from sensor via hypothalamus)
smooth muscles contract
vasoconstriction (blood vessels)
hair stands on end to trap warm air near skin (follicles) (goosebump = muscle
contraction in area of hair follicle)
rhythmic skeletal muscle
contraction = shivering to generate heat
Mammalian Diving Reflex
Section 7.2 Questions, pp. 341, # 1-7
Torpor: alternative physiological state in which metabolism decreases and the heart and respiratory system slow down  conserve energy when food supplies are low and environmental temperatures are extreme
Hibernation: long-term torpor during which the body temp. is lowered as an adaptation to winter cold and food scarcity
Estivation: summer torpor  slow metabolism and inactivity that enables an animal to survive long periods of high temps. And scarce water supplies