Three body systems that function to respond to the environment and maintain homeostasis

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Three body systems that function to respond to
the environment and maintain homeostasis

• Nervous System
• Endocrine System
• Immune System

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These systems demonstrate three important
principles

• Maintaining homeostasis requires the precise
  coordination of many processes and all of the
  bodys systems
• Maintaining homeostasis involves both autonomic
  and voluntary responses
• An individuals homeostatic responses are
  influenced by their lifestyle and personal choices

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The Nervous System

• Response to stimuli
• A characteristic of life
• Based on both chemical and electrical
  communication

Brain and Ganglia of earthworm communicate with
both sensory and motor nerves
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Basics About the Nervous System

• Central Nervous system
• Brain
• Spinal Chord
• Peripheral Nervous system
• cranial nerves
• spinal nerves

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A really important slide to know
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Basics about the nervous system Anatomy of the
Neuron
Direction of nerve impulse
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• Neurons are cells that transmit impulses
• Nerves are bundles of axons
• Ganglia are bundles of neuron cell bodies
• Glial Cells protect, insulate, and support
  neurons
• Scwann cell
• Produces a myelin sheath

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Sensory Neurons, Interneurons, and Motor Neurons
Sensory Neurons
Motor neurons stimulate Muscles and glands
Interneurons process information
processor
Stimulus, sensor, receptor
Response, effector
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• Cerebrum thinks, reasons, stores memories,
  controls voluntary actions
• Corpus callosum connects two halves of the
  cerebrum
• Thalmus relays sensory info from body to
  cerebrum organizes sensations into pleasure,
  pain, fear, anger

Anatomy of the Brain
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• Hypothalmus communicates chemically and
  electronically with body systems to control heart
  rate, temperature, appetite, fluid balance
• Cerebellum coordinates voluntary muscle activity
  and muscle tone, maintains posture and balance
• Medulla internal functions, breathing rate,
  blood pressure, swallowing, vomiting, coughing,
  and sneezing

Anatomy of the Brain
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Workhorses of the Nervous System

• How does a neuron produce a nerve impulse?
• How are nerve impulses passed from neuron to
  neuron?

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How does a neuron produce a nerve impulse?

• Electrical signal
• Gradient of charges between the outside and
  inside of the neuron (axon)
• The outside of the cell is charged (sodium
  ions)
• The inside of the cell is (-) charged

Sodium ions outside Potassium ions inside
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• Resting neuron
• Potassium channels leak out K
• Keeps inside negatively charged (relative to the
  outside of the cell)

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• How is the unequal distribution of ions
  maintained?
• Sodium-potassium Pump continually pumps sodium to
  the outside and pumps the leaky K ions to the
  inside of the cell

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• The nerve impulse is also called the action
  potential
• Begins when Na channels open and allow Na ions
  into the cell
• This causes the inside of the cell to become
  temporarily () charged
• The sodium channels close and the potassium
  channels open
• Restores the original (-) charge to the inside of
  the cell

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• The action potential continues to move down the
  axon of the neuron
• A domino effect
• The action potential is an all or nothing
  response
• Threshold the amount required to initiate the
  action potential

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The propagation of an action potential along the
length of the neuron is called a nerve impulse
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• How some local anesthetics work make the cell
  membrane less permeable to Na ions
• Dehydration or Kidney failure are dangerous
• An increase or reduction of Na and K ions can
  disrupt the nervous system

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What is known about how the nervous system
processes all the information it receives

• Specialized sensory neurons have receptors that
  are specific to a particular stimulus
• These sensory neurons are connected to specific
  areas in your brain and spinal chord

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Specialized sensory neurons have receptors that
are specific to a particular stimulus
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These sensory neurons are connected to specific
areas in your brain and spinal chord
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Development and Neural Networks
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Bridging the gap between neurons

• The conversion of the nerve impulse (electrical
  signal)
• To a chemical signal between neurons
• The space between neurons is called a synapse

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• Presynaptic cell carries the nerve impulse to
  the synapse
• Postsynaptic cell receives the impulse from the
  synapse

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Neurotransmitter Release at the Synapse

• Neurotransmitters are chemicals
• acetylcholine
• After release from the axon of the presynaptic
  cell
• They diffuse into the synapse
• Bind to receptor proteins on the cell membrane of
  the postsynaptic cell

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• The uptake of neurotransmitters by the dendrites
  triggers the next nerve impulse
• The remaining neurotransmitters get degraded by
  enzymes or reabsorbed by the presynaptic cell

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• Neurotransmitters can have an
• excitatory effect (more likely to generate a
  nerve impulse)
• inhibitory effect (less likely to generate a
  nerve impulse)
• How medications and recreational drugs work
• Barbiturates (slow release of acetylcholine)
• Drugs that increase attention span (prolongs the
  time a neurotransmitter is active in the synapse)
• Ritalin (stimulant/ sedative)
• Nicotine (stimulant, mimics acetylcholine)
• SSRIs

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Structure of Serotonin and its Receptor
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The nervous system and homeostasis

• The nervous system provides the physical
  machinery that produces our reflex actions
• The knee-jerk
• Hot stove
• Sneezing
• Vomiting

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Characteristics of Reflex Responses

• They are automatic
• unconscious
• protective responses to avoid potentially
  dangerous disruptions of homeostasis
• They are very rapid
• very few cells are involved

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Involuntary Physiological Activities
Medulla

• Homeostasis is maintained by the autonomic
  division of your peripheral nervous system.
• And the medulla in your central nervous system
• internal functions, breathing rate, blood
  pressure, swallowing, vomiting, coughing, and
  sneezing

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• The rate of heartbeat is controlled by 2 separate
  sets of nerves
• Sympathetic
• Excites the heart to beat faster
• Parasympathetic
• Inhibits or slows the heart

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Getting out of bed in the morning

• Sudden change in position causes a drop in blood
  pressure
• Blood flow has to move against gravity
• Receptors in blood vessels detect the change in
  blood pressure and send message to the brain
• The brain stimulates the sympathetic nervous
  system
• Heart beat increases
• Blood pressure increases
• What causes dizzy spells?

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Fight or Flight Response

• Sympathetic division of your autonomic nervous
  system
• bronchi relax
• pupils dilate
• heart rate increases
• liver releases glucose
• digestive organs relax
• bladder and colon stretch (increased retention)
• adrenaline rush
• Once danger is over the parasympathetic system
  takes over

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Voluntary Behaviors

• Automatic sensations such as
• Pain
• Thirst
• Cold
• We can choose to respond to these sensations and
  correct the homeostatic imbalance
• Or ignore them
• Choose behaviors to prevent imbalances

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Endocrine System

• Regulates slower, longer lasting responses
• rates of chemical reactions
• transport of substances across membranes
• growth and reproduction
• Hormones
• proteins
• steroids

Basics About the Endocrine System p100-101
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Organs of the Endocrine System
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Some Hormones of the Endocrine System
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Hormones act on specific target cells or organs

• Whether a cell responds to a particular hormone
  depends on whether it has a receptor on its cell
  membrane

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• Secretin is produced by the small intestine in
  response to acidic food
• Travels through the blood to the pancreas
• Stimulated the production of bicarbonate
• Neutralizes the acidity

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Some hormones affect many organs simultaneously

• Adrenaline epinephrine
• Epinephrine has the same effect as the
  sympathetic nervous system
• Both tell the liver to break down glycogen into
  sugar.
• Epinephrines effect lasts 4-5X longer than
  signals from the sympathetic nervous system
• Removed from the bloodstream very slowly

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The Nervous and Endocrine Systems

• Hormones regulate homeostasis in much the same
  way the nervous system does through negative
  feedback mechanisms
• There is a close coordination between the nervous
  and endocrine systems

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The Hypothalamus and the Pituitary Glands

• Connected by nerves in the posterior pituitary
• Connected by blood vessels in the anterior
  pituitary (1930s)
• Hormones are powerful molecules produced in small
  quantities
• 1969 isolated the first hormone produced by the
  hypothalamus
• Connection between brain and pituitary explains
  why psychological factors can influence
  reproductive processes in females

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• Hypothalamus connected to emotional part of the
  brain
• Why sight, sound, smell trigger emotions
• Releasing and inhibiting factors affect the
  pituitary
• Pituitary regulates reproductive functions

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Making Choices, Evaluating risks

• The role of behavior in reducing threats to
  homeostasis
• Illness as an imbalance
• Can you control the risk of developing a
  particular illness?
• Lifetime risk of breast cancer for women in the
  U.S. is 1 in 8
• Scientists cannot define life style changes that
  minimize risks
• Early detection will increase survival rate
• Testing for breast cancer BRCA-1 gene

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• We can avoid smoking related diseases by not
  smoking
• Cigarette smoke has 43 known carcinogens
• Smoking increases heart disease
• Destroys lung tissue
• Life long smoking does not guarantee that someone
  will get lung cancer
• What is the known risk?

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General Strategies for Avoiding Illness or Injury

• What are some of the things you do to stay
  healthy?