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Ever wonder why you shiver, or why you sweat? Why do you pee or poop? Or, breath out CO2? Why??

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Title: Ever wonder why you shiver, or why you sweat? Why do you pee or poop? Or, breath out CO2? Why??


1
Ever wonder why you shiver, or why you
sweat? Why do you pee or poop? Or, breath out
CO2?Why??
Homeostasis
2
Why do you shiver?
3
Why do you sweat?
4
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6
To Regulate??
  • Shiver and sweat To regulate/maintain
    Temperature of your body
  • Pee To regulate/maintain stable Water/salt/urea
    level of your body
  • Poop To regulate waste or undigested food level
  • Why EAT? Why breath?
  • To maintain energy level to run the cells

7
Kidneys???Too much waterOUT!!(pee)
8
Regulation
  • rule, requirement
  • managing, organizing
  • RULES???

9
WHY Regulation?????
  • So all systems can work together to maintain the
    STABLE conditions in your body.
  • I mean to maintain HOMEOSTASIS! (maintaining a
    stable or constant internal environment)
  • How ???

10
By Control and coordination of all the body
systems
  • Coordination?
  • Working together in harmony

11
IT'S ALL ABOUT HOMEOSTASIS
  • Homeostasis is achieved by making sure the
    temperature, pH (acidity/alkalinity), and oxygen
    levels (and many other factors) are set just
    right for your cells to survive. Homeostasis
    levels are different for each species.
  • Who does Homeostasis?
  • Well, if you are living, you got to do
    HOMOEOSTASIS!!!! NO EXCEPTIONS!!!!!!

12
What happens if an organism fail to do
HOMEOSTASIS?
  • Sickness
  • Disease

13
WHO in my body helps maintain homeostasis?
  • Who tells me to shiver, sweat, pee, poop, eat,
    breath, drink.blah blah blah
  • Brain?
  • Yeah for the most part, but it has help!

14
Parts that work with brain
  • Well, there is spinal cord.
  • And then, there are nerves going everywhere,
  • there are chemicals (like hormones,
    neurotransmitters) acting as messengers to inform
    brain, spinal cord, cells.

15
Lets talk about the nervous system...
16
Which parts constitute(make) the nervous system?
  • BRAIN
  • SPINAL CORD
  • NERVES
  • Nervous system is the control center for your
    entire body. Your brain uses information it
    receives from your nerves to coordinate all of
    your actions and reactions.
  • Yes copy!

17
Nervous system is divided into 2 main parts
Central and Peripheral.
18
Human Nervous System has 2 parts copy yes
  • Central Nervous System
  • 2) Peripheral Nervous System

Brain
Spinal Cord
NERVES
19
Lingo of Nervous system
  • Stimulus

20
Stimulus
  • Something causing a response.
  • An agent, action, or condition that elicits or
    accelerates a physiological or psychological
    activity or response.
  • Something that incites or rouses an action an
    incentive

21
Response
  • The act of responding.
  • A reply or an answer.
  • A reaction, as that of an organism or a
    mechanism, to a specific stimulus.

22
Impulse
  • MESSAGES conducted through the cells of nervous
    system

23
What is nervous system made up of?
  • Cells, of course
  • called nerve cells or neurons.
  • are specialized to carry "messages" through an
    electrochemical process.
  • The human brain has approximately 100 billion
    neurons.

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A Neuron
26
A Neuron
  • (Copy)

27
Neuron Anatomy
28
Lets first talk about brain
  • Parts of Brain
  • cerebrum
  • cerebellum
  • brain stem (Medulla)
  • hypothalamus
  • pituitary gland

29
The Biggest Part the Cerebrum
  • The biggest part of the brain is the cerebrum.
    The cerebrum makes up 85 of the brain's weight,
    and it's easy to see why. The cerebrum is the
    thinking part of the brain and it controls your
    voluntary muscles the ones that move when you
    want them to. So you can't dance or kick a
    soccer ball without your cerebrum.

30
And many other jobs
  • When you're thinking hard, you're using your
    cerebrum. You need it to solve math problems,
    figure out a video game, and draw a picture. Your
    memory lives in the cerebrum both short-term
    memory (what you ate for dinner last night) and
    long-term memory (the name of that roller-coaster
    you rode on two summers ago). The cerebrum also
    helps you reason, like when you figure out that
    you'd better do your homework now because your
    mom is taking you to a movie later.

31
Cerebrum has 2 halves
  • One on either side of the head. Some scientists
    think that the right half helps you think about
    abstract things like music, colors, and shapes.
    The left half is said to be more analytical,
    helping you with math, logic, and speech.
    Scientists do know for sure that the right half
    of the cerebrum controls the left side of your
    body, and the left half controls the right side.

32
Your Brain on Shopping
  • Ladies! Have you ever felt jealous of your boy
    friend/fiancé/brother? I have!
  • The shopping process just seems so easy for men. 
    They decide what they want, do a little research,
    bada-bing, bada-boomand he buys what he wants. 
  • We, however, turn it into a prime time soap
    opera. 
  • I attribute it to wiring in the brain, and I
    think it applies to many men and women out there.
  • As a refresher, remember that the left brain is
    the logical, analytical side of the brain - it is
    the worker bee, focusing and analyzing one thing
    at a time.  The right brain is free to play -
    its the home of imagination, emotional memory
    and bonding with others. 

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34
The Balancing Act
Cerebellum
  • Next up is the cerebellum. The cerebellum is at
    the back of the brain, below the cerebrum. It
    controls balance, movement, and coordination (how
    your muscles work together).

35
Brain Stem Keeps You Breathing and More
  • Another brain part that's small but mighty is the
    brain stem. The brain stem sits beneath the
    cerebrum and in front of the cerebellum.
  • It connects the rest of the brain to the spinal
    cord, which runs down your neck and back. The
    brain stem is in charge of all the functions your
    body needs to stay alive, like breathing air,
    digesting food, and circulating blood.

36
  • Part of the brain stem's job is to control your
    involuntary muscles the ones that work
    automatically, without you even thinking about
    it. There are involuntary muscles in the heart
    and stomach, and it's the brain stem that tells
    your heart to pump more blood when you're biking
    or your stomach to start digesting your lunch.
    Whew! It's a big job being the brain's stem!

37
Hypothalamus Controls Temperature
  • The hypothalamus is like your brain's inner
    thermostat (that little box on the wall that
    controls the heat in your house). The
    hypothalamus knows what temperature your body
    should be (about 98.6 Fahrenheit or 37
    Celsius). If your body is too hot, the
    hypothalamus tells it to sweat. If you're too
    cold, the hypothalamus gets you shivering. Both
    shivering and sweating are attempts to get your
    body's temperature back where it needs to be.

38
Voluntary and involuntary
  • Voluntary
  • At willjob of cerebrum
  • Involuntary
  • Automaticnot under your control
  • Medulla
  • Spinal cord

39
Pituitary gland!
  • Hey! Its TINYbut dont let the size fool you!!!
    Its the MASTER GLAND for crying out loud
  • only about the size of a pea!

40
Pituitary Gland Controls Growth
  • Has a big JOBgtgtgtto produce and release HORMONES
    into your body (I mean in ______). If your
    clothes from last year are too small, it's
    because your pituitary gland released special
    hormones that made you grow.
  • This gland is a big player in puberty too. This
    is the time when boys' and girls' bodies go
    through major changes as they slowly become men
    and women, all thanks to hormones released by the
    pituitary gland
  • Will talk about other hormones later.

41
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45
Nervous System Cells Why do they have long
tail-like AXON?
  • Neurons have long axons that enable them to
    transmit signals

46
So what are nerves??
  • A bundle of neurons

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49
How many types of neurons do you think are
there? A General Sense
50
Neurons Are they all the same?
  • No, Neurons can be classified by the direction
    that they send information.
  • They are of 3 types

51
  • 1) Sensory (or afferent) neurons send
    information from sensory receptors (e.g., in
    skin, eyes, nose, tongue, ears) TOWARD the
    central nervous system.
  • 2) Motor (or efferent) neurons send information
    AWAY from the central nervous system to muscles
    or glands.
  • 3) Interneurons Make brain and spinal cord
    (central nervous system). They send information
    between sensory neurons and motor neurons.
  • Copy yes

52
whos the receptor and whos the effector
53
Anatomy of a Neuron
  • Cell body main part
  • Dendrite receives action potential
    (stimulation)
  • Axon branches from cell body, where the action
    potential/signal travels
  • Axon terminal/End brushes end of an axon

54
___________ Nervous System
  • Sensory neurons carry messages _________ the CNS
    from _________ __________ all over body.
  • Sensory receptors convert the signal into an
    __________ onealso called the action potential
    of a nerve.
  • Sensory receptors are in sense organs, such as
    eyes, ears, mouth, nose, skin and different
    regions of the brain respond to different
    signals.
  • Interneuronsare there in the brain and spinal
    cord to make sense of the stimulus.
  • Motor neuronstake the signal back to the
    muscles/sensory organs

55
  • 4 Which process is most directly responsible for
  • maintaining internal stability in an organism
  • when its environment is constantly changing?
  • (1) digestion (3) reproduction
  • (2) feedback (4) evolution

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57
  • 52 Describe what would happen if a drug molecule
    shaped like were introduced into
  • this nerve pathway. 1
  • __________________________________________________
    _____________________
  • __________________________________________________
    _____________________
  • 53 Identify one substance, other than the
    secretions from nerve cells, used in cell
  • communication. 1
  • __________________________________________________
    _____________________

58
How do dendrites
59
How do dendrites receive the message?
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Cell Membrane
  • How do cells receive messages and talk to each
    other
  • I mean communicate with each other
  • Through receptor proteins present on the cell
    membrane

62
Cell membrane is made up of a phospholipid
bilayer its the fluid mosaic model
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  • Cell Membrane
  •  We have to start somewhere. Let's start on the
    outside. Around every cell is a CELL MEMBRANE.
    The membrane is like a big plastic bag with tiny
    holes in it. Scientists also call the cell
    membrane a PLASMA MEMBRANE.

67
  • WHAT'S IT FOR? The purpose of the cell membrane
    is to hold the cell together. It keeps all of the
    pieces, like the organelles and the CYTOPLASM,
    inside. The membrane also controls what goes in
    and out of the cell. It acts like a crossing
    guard and says "You better stop right there
    buddy. You aren't getting in here." CELL
    MEMBRANE STRUCTURE Scientists have a theory
    about the way a cell membrane works. The theory
    is called the FLUID MOSAIC MODEL. The idea says
    that there are two layers of MOLECULES, a
    BILAYER. These two layers are made up of
    molecules called phospholipids. Take a look, it's
    like a sandwich with two pieces of bread and some
    alfalfa on the inside. Each phospholipid has an
    HYDROPHOBIC and HYDROPHILIC end. They are big
    words, but they mean very simple things. HYDRO
    means water. PHOBIC means afraid. PHILIC means
    loving. So one end of the molecule is afraid of
    the water, and one end loves being in the water.
    Millions of these molecules line up together to
    form a cell membrane.

68
  • CELL MEMBRANE PROTEINS Throughout the membrane
    are proteins stuck inside the membrane. These
    proteins cross the bilayer and make the holes
    that let ions and molecules in and out of the
    cell. (That crossing guard thing again.) When
    ions move through the cell membrane, it is called
    FACILITATED DIFFUSION. Facilitated means helped.
    Diffusion means moving from one area to another.
    So facilitated diffusion is a procedure where an
    ion is helped across the membrane. (Like helping
    an old lady across the street.)

69
Direction of impulse
  • How do dendrites receive the message?
  • Receptor proteins on their cell membranes!
  • copy

70
Receptor
  • In biochemistry, a receptor is a protein on the
    cell membrane that binds to a specific molecule
    (a ligand), such as a neurotransmitter, hormone,
    or other substance, and initiates the cellular
    response to the ligand.

71
Aim How do neurons conduct impulses?
  • Do Now What will happen if your homeostasis is
    disturbed/breaks down?

72
Impulse travelingits a relay race
73
Transmission of neural signals How it Works
  • Signaling activity of the nervous system is
    composed of
  • electrical activity within neurons and
  • chemical flow between neurons.

74
  • Dendritesreceive signal
  • Impulse passes through axon as electric (or
    action) potential
  • When it reaches the terminal end of axon,the end
    brushes secret neurotransmitters
  • Receptors on dendrites of the next neuron bind to
    the neurotransmitters
  • And the impulse travels through the next neurons
    body as ___________

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How do neurons conduct (carry!) the messages (or
impulses)?
  • In general, the signaling activity of the nervous
    system is composed of electrical activity within
    neurons and chemical flow between neurons. Quite
    a complex network!
  • 200 years ago found out that a recently dead
    animal will still contract muscles if an
    electrical stimulation is sent through.
  • copy

77
  • DO YOU THINK BRAIN KNOWS/CONTROLS EVERY SINGLE
    MOVEMENT IN YOUR BODY?
  • NOOOSometimes spinal cord comes in handyfor
    emergency responses

78
The Patellar Reflex
79
Reflex action
  • Being an involuntary action or response, such as
    a sneeze, blink, or hiccup.
  • Produced as an automatic response or reaction

80
  • The reflex action

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Peripheral Nervous System(2 Types)
  • Somatic nervous system
  • is for voluntary muscle control. These neurons
    control the skeletal muscles.
  • Also some spinal reflexes. EX patellar reflex
  • Autonomic nervous system
  • is automatic. Control of heart rate,
    respiration, blood pressure, smooth muscle, etc.
  • This has 2 separate divisions sympathetic and
    parasympathetic
  • Copy yes

84
An Overview of the (copy) Nervous
System
Peripheral Nervous System
Central Nervous System -Brain -Spinal
Cord
Motor Neurons -carry signals
away from CNS
Sensory Neurons -carry messages towards spinal
cord from sensory receptors
Somatic System Voluntary Nerves --neurons
control skeletal muscles
Autonomic System Visceral, Involuntary --heart,
blood vessels, digestive organs, smooth muscle
Sympathetic Division --fight or
flight --activated by stress
Parasympathetic Division --Routine
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  • Acetylcholine in skeletal muscles
  • Norepinephrine and Epinephrine respond to stress
  • Dopamine Serotonin in the brain
  • Enzymes break down neurotransmitters so neurons
    are not over stimulated.
  • Ex. cholinesterase (breaks down
    acetylcholine).

87
Human Nervous System
  • Central and
  • Peripheral

88
A General Sense
89
An Overview of the Nervous System
Peripheral Nervous System
Central Nervous System -Brain -Spinal
Cord
Motor Neurons -carry signals
away from CNS
Sensory Neurons -carry messages towards spinal
cord from sensory receptors
Somatic System Voluntary Nerves --neurons
control skeletal muscles
Autonomic System Visceral, Involuntary --heart,
blood vessels, digestive organs, smooth muscle
Sympathetic Division --fight or
flight --activated by stress
Parasympathetic Division --Routine
90
Nervous System Cells
  • Called neurons
  • Neurons have long axons that enable them to
    transmit signals. Many neurons together are
    called a nerve.
  • Each nerve has a dorsal root (info into the CNS)
    and a ventral root (info out from CNS to body).

91
Neuron Anatomy
92
Anatomy of a Neuron
  • Cell body main part
  • Dendrite receives action potential
    (stimulation) from other neurons
  • Axon branches from cell body, where the action
    potential occurs
  • Axon terminal end of an axon
  • Myelin sheath lipid layer for protection over
    neurons that allows for increase in speed of
    signal transmission made by Schwann cells
  • Nodes of Ranvier gaps in myelin sheath along
    the axon, where most Na pumps are located
  • Synaptic Cleft gap between neurons between the
    axon terminal of 1 neuron and the dendrite of a
    2nd neuron

93
Anatomy of a Neuron-Draw this!
94
Central Nervous System (CNS)
  • BRAIN
  • About 1.4 kg, 2 of body weight
  • About 100 billion neurons
  • 12 pairs of cranial nerves are connected to the
    human brain
  • Example Pupil reflex in response to bright
    light, to avoid damage to retina. Nerves that
    control this reflex are connected to the brain.
  • Others blinking, Hering-Breuer reflex

95
Spinal Cord
  • Starts at the medulla oblongata (in the brain)
  • Outer area is made up of the axons of motor and
    sensory neurons white matter
  • Inner, rigid core made up of motor neuron cell
    bodies gray matter
  • 31 pairs of spinal nerves branch out to the body
  • Spinal Reflexes these dont go to the brain,
    instead they go to the spinal cord--patellar
    reflex

96
The Patellar Reflex
97
Peripheral Nervous System(Motor and
Sensory)Motor Division signals away from CNS
  • Somatic nervous system is for voluntary muscle
    control. These neurons control the skeletal
    muscles. Also some spinal reflexes. EX
    patellar reflex
  • Autonomic nervous system is automatic. Control
    of heart rate, respiration, blood pressure,
    smooth muscle, etc.
  • This has 2 separate divisions sympathetic and
    parasympathetic

98
Autonomic Sympathetic Division Parasympathetic
Division
  • Sympathetic Shunting of blood from one part of
    body (ex stomach to heart) to another.
    Activated by physical or emotional stress. Fight
    or Flight response.
  • Parasympathetic Routine life, conserves energy,
    heart rate lowers, digestive organs back to
    normal. Rest and Ruminate response.

99
Autonomic NS Parasympathetic and Sympathetic
Controls
100
Peripheral Nervous SystemSensory Division
  • Sensory neurons carry messages toward the CNS
    from sensory receptors all over body.
  • Sensory receptors act as energy transducers. A
    transducer is a device for converting a
    non-electrical signal into an electrical one. In
    this case, the electrical signal produced is the
    action potential of a nerve.
  • Sensory receptors are in sense organs, such as
    eyes, ears, mouth, nose, skin and different
    regions of the brain respond to different
    signals.

101
Warm Up
  • Thursday 1/4/07
  • What are the two types of neurons of the
    Peripheral Nervous System and what do they do?
  • Answer

102
Types of Sensory Receptors
Stimulus Type of Sensory Receptor Location
Light Photoreceptors Retina
Mechanical Mechanoreceptors Under the skin, inner ear
Heat Thermoreceptors Hypothalamus, under the skin
Pressure Baroreceptors Walls of some arteries
Chemicals Chemoreceptor Mouth, nose
103
Transmission of neural signals How it Works
  • In general, the signaling activity of the nervous
    system is composed of electrical activity within
    neurons and chemical flow between neurons. Quite
    a complex network!
  • 200 years ago found out that a recently dead
    animal will still contract muscles if an
    electrical stimulation is sent through.

104
Within one neuron
  • The resting potential of a neuron is -70
    millivolts. The inside of the cell is relatively
    more negative than the outside, due to an
    imbalance of ions and some negatively charged
    proteins inside.
  • When a dendrite/cell body is stimulated
    (pressure, light, air vibrations, etc.),
    membranes become temporarily permeable to Na ion
    at the site of stimulation (triggers these gates
    to open).
  • Na ions rush into the cell, through gated
    protein channels, and the inside becomes more
    positive. This reverse of polarity begins an
    action potential. The action potential starts
    where the cell body meets the axon. Threshold
    potential is about -50 millivolts, action
    potential is about 30 millivolts.
  • Gated channels keep opening along the axon, and
    Na continues to enter. Much like fire burns
    down a rope. Action potential continues from
    start of axon to terminal, always in one
    direction.

105
And even more AH!
  • Shortly after Na channels open, they close, and
    the K channels open, allowing K ions to leave
    the cell, and the resting potential returns.
  • The neuron cannot generate another action
    potential during this time. Na gates close, K
    flow out returns the neuron to resting potential.
    This period is called the refractory period.
  • The Na/K pump (that we learned about in active
    transport) pumps away to keep the proper
    concentrations of ions across the membrane. This
    requires lots of energy ATP!

106
Diagram of action potential through an axon
107
Transmitting to another neuron
  • When the Action Potential reaches the terminal,
    Ca2 gates open, Ca2 comes into the cell.
  • Increase in Ca2 concentration causes vesicles to
    fuse with the pre-synaptic membrane and release
    neurotransmitters into the synapse.
  • Neurotransmitters bind to receptor proteins on
    the post-synaptic membrane of the next neuron,
    which signals Na gates to open and the action
    potential starts all over again.

108
Examples of Neurotransmitters
  • Acetylcholine in skeletal muscles
  • Norepinephrine and Epinephrine respond to stress
  • Dopamine Serotonin in the brain
  • Enzymes break down neurotransmitters so neurons
    are not over stimulated.
  • Ex. cholinesterase (breaks down
    acetylcholine).

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113
A Little Quiz
  • 1. What is the potential for the resting neuron?
  • 2. What is the potential for a neuron that is
    sending an action potential?
  • 3. When a neuron goes from its resting potential
    to its action potential which ion moves? Where
    does the ion move? How does it move? Active or
    Passive?
  • 4. When a neuron goes from its action potential
    to its resting potential which ions move? Where
    do they move? How does it move? Active or
    Passive?

114
A Few More
  • 5. Where in the neuron is the presynaptic
    membrane? (axon, cell body, or dendrite)
  • 6. What happens when the action potential reaches
    the presynaptic membrane?
  • 7. What happens when the neurotransmitter binds
    to the receptors on the postsynaptic membrane?

115
Warm Up
  • Thursday 1/4/07
  • What are the two types of neurons of the
    Peripheral Nervous System and what do they do?
  • Answer

116
Neurons are special cells!
  • Neurons have specialized extensions called
    dendrites and axons. Dendrites bring information
    to the cell body and axons take information away
    from the cell body.
  • Neurons communicate with each other through an
    electrochemical process.
  • Neurons contain some specialized structures (for
    example, synapses) and chemicals (for example,
    neurotransmitters).

117
  • Neurons come in many different shapes and sizes.
    (Remember that 1 micron is equal to one
    thousandth of a millimeter!).

118
  • In the peripheral nervous system, neurons can be
    functionally divided in three ways
  • Sensory (afferent) - carry information INTO the
    central nervous system from sense organs or motor
    (efferent) - carry information away from the
    central nervous system (for muscle control).
  • Cranial - connects the brain with the periphery
    or spinal - connects the spinal cord with the
    periphery.
  • Somatic - connects the skin or muscle with the
    central nervous system or visceral - connects the
    internal organs with the central nervous system.

119
  • Unlike cold-blooded animals like lizards and
    snakes, humans keep the same body temperature at
    all times
  • discover how a part of your brain called the
    hypothalamus acts as a kind of thermostat,
    keeping you as close to normal temperature as
    possible!

120
  • discover how a part of your brain called the
    hypothalamus acts as a kind of thermostat,
    keeping you as close to normal temperature as
    possible!
  • Youll also learn about different forms of
    homeostasis, like how your immune system defends
    you from invading viruses, how your respiratory
    system regulates the amount of oxygen in your
    blood, and more. If youve ever wondered how your
    body regulates itself, this is the movie for you!

121
What is homeostatic regulation?
  • Answer
  • Homeostatic regulation is controlled in the body
    by the autonomic nervous system and seeks to
    maintain relatively stable conditions in the
    internal environment. The main gland of
    homeostasis is the hypothalamus and the major
    organ of homeostasis are the kidneys.  

122
  • NEGATIVE FEEDBACK
  • Negative feedback is a process that happens when
    your systems need to slow down or completely stop
    a process that is happening. When you eat, food
    travels into your stomach, and digestion begins.
    You don't need your stomach working if you aren't
    eating. The digestive system works with a series
    of hormones and nervous impulses to stop and
    start the secretion of acids in your stomach.
    Another example of negative feedback occurs when
    your body's temperature begins to rise and a
    negative feedback response works to counteract
    and stop the rise in temperature. Sweating is a
    good example of negative feedback

123
  • POSITIVE FEEDBACK
  • Positive feedback is the opposite of negative
    feedback in that encourages a physiological
    process or amplifies the action of a system.
    Positive feedback is a cyclic process that can
    continue to amplify your body's response to a
    stimulus until a negative feedback response takes
    over. An example of positive feedback also can
    happen in your stomach. Your stomach normally
    secretes a compound called pepsinogen that is an
    inactive enzyme. As your body converts pepsinogen
    to the enzyme pepsin, it triggers a process that
    helps convert other pepsinogen molecules to
    pepsin. This cascade effect occurs and soon your
    stomach has enough pepsin molecules to digest
    proteins.

124
  • BODY TEMPERATURE EXAMPLE
  • A good example of system regulation of your body
    can be found in the regulation of body
    temperatures. You are a homoeothermic organism,
    which means you regulate your own body
    temperature. Other species like reptiles are not
    homoeothermic. Anyway, if your body gets too
    cold, a series of actions are taken to warm your
    body. Sensors throughout your nervous system can
    recognize when the temperature drops and might
    trigger your muscular system to start shivering.
    The constant contractions of your muscles allow
    heat to be generated. Your nervous and endocrine
    systems may also contract the blood vessels of
    your circulatory system to keep blood in the core
    of your body and not the extremities (like
    fingers).

125
  • Shivering is one of the methods that the human
    body uses to warm itself.  It is a neurological
    reaction, that the body executes when it gets too
    cold.   Joggers are familiar with the concept of
    moving to stay warm they run in the coldest of
    weather and manage to stay warm.  Basic physics
    dictate that energy taken from a storage source
    (like our fat) and changed to another form of
    energy (your body movements), results in yet
    another form of energy - heat.  So when your
    muscles start moving back and fourth rapidly,
    they make heat, which helps warm the body in the
    cold.  

126
Panting?
  • We know from our own experience that humans sweat
    to increase cooling by evaporation. Dogs, in
    contrast, have few sweat glands, and they cool
    primarily by panting - a very rapid, shallow
    breathing that increases evaporation from the
    upper respiratory tract. Some animals use a third
    method for increasing evaporation They spread
    saliva over their fur and lick their limbs, thus
    achieving cooling by evaporation....

127
  • Most homeostatic regulation is controlled by the
    release of hormones into the bloodstream. However
    other regulatory processes rely on simple
    diffusion to maintain a balance.
  • Homeostatic regulation extends far beyond the
    control of temperature. All animals also regulate
    their blood glucose, as well as the concentration
    of their blood. Mammals regulate their blood
    glucose with insulin and glucagon. These hormones
    are released by the pancreas. If the pancreas is
    for any reason unable to produce enough of these
    two hormones diabetes results. The kidneys are
    used to remove excess water and ions from the
    blood. These are then expelled as urine. The
    kidneys perform a vital role in homeostatic
    regulation in mammals removing excess water, salt
    and urea from the blood. These are the body's
    main waste products.
  • Sleep timing depends upon a balance between
    homeostatic sleep propensity, the need for sleep
    as a function of the amount of time elapsed since
    the last adequate sleep episode, and circadian
    rhythms which determine the ideal timing of a
    correctly structured and restorative sleep
    episode.1

128
  • Control Mechanisms
  • All homeostatic control mechanisms have at least
    three interdependent components for the variable
    being regulated The receptor is the sensing
    component that monitors and responds to changes
    in the environment. When the receptor senses a
    stimulus, it sends information to a control
    center, the component that sets the range at
    which a variable is maintained. The control
    center determines an appropriate response to the
    stimulus. The result of that response feeds to
    the effector, either enhancing it with positive
    feedback or depressing it with negative feedback
    2

129
Negative Feedback Mechanisms
  • Negative feedback mechanisms reduce or suppress
    the original stimulus, given the effectors
    output. Most homeostatic control mechanisms
    require a negative feedback loop to keep
    conditions from exceeding tolerable limits. The
    purpose is to prevent sudden severe changes
    within a complex organism. There are hundreds of
    negative feedback mechanisms in the human body.
    Among the most important regulatory functions are
    thermoregulation, osmoregulation, and
    glucoregulation. The kidneys contribute to
    homeostasis in five important ways regulation of
    blood water levels, re-absorption of substances
    into the blood, maintenance of salt and ion
    levels in the blood, regulation of blood pH, and
    excretion of urea and other wastes.
  • . 2

130
  • A negative feedback mechanism example is the
    typical home heating system. Its thermostat
    houses a thermometer, the receptor that senses
    when the temperature is too low. The control
    center, also housed in the thermostat, senses and
    responds to the thermometer when the temperature
    drops below a specified set point. Below that
    target level, the thermostat sends a message to
    the effector, the furnace. The furnace then
    produces heat, which warms the house. Once the
    thermostat senses a target level of heat has been
    reached, it will signal the furnace to turn off,
    thus maintaining a comfortable temperature - not
    too hot nor cold

131
  • Examples of the use of negative feedback to
    control its system are thermostat control,
    phase-locked loop, hormonal regulation, and
    temperature regulation in animals.
  • A simple and practical example is a thermostat.
    When the temperature in a heated room reaches a
    certain upper limit the room heating is switched
    off so that the temperature begins to fall. When
    the temperature drops to a lower limit, the
    heating is switched on again. Provided the limits
    are close to each other, a steady room
    temperature is maintained. The same applies to a
    cooling system, such as an air conditioner, a
    refrigerator, or a freezer.

132
Positive Feedback Mechanisms
  • Positive feedback mechanisms are designed to
    accelerate or enhance the output created by a
    stimulus that has already been activated.
  • Unlike negative feedback mechanisms that initiate
    to maintain or regulate physiological functions
    within a set and narrow range, the positive
    feedback mechanisms are designed to push levels
    out of normal ranges. To achieve this purpose, a
    series of events initiates a cascading process
    that builds to increase the effect of the
    stimulus. This process can be beneficial but is
    rarely used by the body due to risks of the
    acceleration becoming uncontrollable.

133
  • One positive feedback example event in the body
    is blood platelet accumulation, which, in turn,
    causes blood clotting in response to a break or
    tear in the lining of blood vessels. Another
    example is the release of oxytocin to intensify
    the contractions that take place during
    childbirth.2
  • Positive feedback can also be harmful. One
    particular example is when a fever causes a
    positive feedback within homeostasis that pushes
    the temperature continually higher. Body
    temperature can reach extremes of 45C (113F),
    at which cellular proteins denature, causing the
    active site in proteins to change, thus causing
    metabolism to stop, resulting in death.

134
What is a "Feedback Loop"?Scientists 'Feedback
Loops' Are the Single-Biggest Threat to
Civilization From Global Warming
135
Today it is another beautiful, sunny day in NY
and on the Arctic tundra
  • It may sound nicer that way -- but it's a big
    problem for the Earth.
  • Scientists say the warm weather adds to global
    warming because of "feedback loops."
  • In a feedback loop, the rising temperature on the
    Earth changes the environment in ways that then
    create even more heat. Scientists consider
    feedback loops the single-biggest threat to
    civilization from global warming

136
Homeostatic Imbalance
  • Much disease results from disturbance of
    homeostasis, a condition known as homeostatic
    imbalance. As it ages, every organism will lose
    efficiency in its control systems. The
    inefficiencies gradually result in an unstable
    internal environment that increases the risk for
    illness. In addition, homeostatic imbalance is
    also responsible for the physical changes
    associated with aging. Even more serious than
    illness and other characteristics of aging, is
    death. Heart failure has been seen where nominal
    negative feedback mechanisms become overwhelmed,
    and destructive positive feedback mechanisms then
    take over.2
  • Diseases that result from a homeostatic imbalance
    include diabetes, dehydration, hypoglycemia,
    hyperglycemia, gout, and any disease caused by a
    toxin present in the bloodstream. All of these
    conditions result from the presence of an
    increased amount of a particular substance. In
    ideal circumstances, homeostatic control
    mechanisms should prevent this imbalance from
    occurring, but, in some people, the mechanisms do
    not work efficiently enough or the quantity of
    the substance exceeds the levels at which it can
    be managed. In these cases, medical intervention
    is necessary to restore the imbalance, or
    permanent damage to the organs may result

137
  • Some biological systems exhibit negative feedback
    such as the baroreflex in blood pressure
    regulation and erythropoiesis. Many biological
    process (e.g., in the human anatomy) use negative
    feedback. Examples of this are numerous, from the
    regulating of body temperature, to the regulating
    of blood glucose levels. The disruption of
    negative feedback can lead to undesirable
    results in the case of blood glucose levels, if
    negative feedback fails, the glucose levels in
    the blood may begin to rise dramatically, thus
    resulting in diabetes.

138
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