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HOMEOSTASIS

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HOMEOSTASIS pH of 7.35 37 C 0.1% blood sugar Homeostasis an equilibrium (steady state) between an organism s various physiological functions, and between the ... – PowerPoint PPT presentation

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Title: HOMEOSTASIS


1
HOMEOSTASIS
pH of 7.35
37?C
0.1 blood sugar
2
Homeostasis and Control Systems
  • Homeostasis an equilibrium (steady state)
    between an organisms 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

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
  1. Excreting Waste
  2. Urinary System
  3. Formation of Urine
  4. Water Balance
  5. 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
  • 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)

11
Response
No heat produced
Heater turned off
Room temperature decreases
Set point
Too hot
Set point
Set point
Too cold
Control center thermostat
Room temperature increases
Heater turned on
Response
Heat produced
12
  • NEGATIVE
  • FEEDBACK
  • ?decreases
  • an action
  • ?stops when return to normal
  • ?most homeostatic control mechanisms are negative
    feedback

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
  • POSITIVE
  • FEEDBACK
  • (reinforces)
  • ?increases
  • an action
  • ?must be turned off by outside event
  • ?decreases
  • an action
  • ?could run away death

blood loss - ? B.P. - ? heart beat - ?
B.P. blood clotting
15
  • Decrease in progesterone ----gtincrease in uterine
    contraction ----gt release of oxytocin ---gt
    increase in stronger contractions----gtbaby is
    expelled-----gtcontraction stop---gtrelease of
    oxytocin stops

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 (37C) regardless of environment. Respond
    to changes in environmental temp. by using energy
    to produce heat

17
Relationship between body temperature
Environmental temperature
40
River otter (endotherm)
30
Body temperature (C)
20
Largemouth bass (ectotherm)
10
10
20
30
40
0
Ambient (environmental) temperature (C)
18
B. Modes of Heat Exchange
  • Organisms exchange heat by four physical
    processes conduction, convection, radiation, and
    evaporation

Evaporation removal heat from surface of liquid
lost as gas
Radiation radiate heat between objects not in
contact.
Convection transfer heat by mvt air
Conduction direct transfer heat between
molecules in contact
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

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

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

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

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

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
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
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

27
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
28
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29
Human thermostat hypothalamus (control centre)
30
  • 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
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