The Nervous system

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The Nervous system
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Do Now

• Put together the puzzle without talking, making
  eye contact, or using hand gestures.
• Did you find this difficult?
• What would make it easier?
• How does this relate to your body?

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Communication

• Nearly all multicellular organisms have
  communication systems.
• Specialized cells carry messages from one cell to
  another so that communication among all body
  parts is smooth and efficient.

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Communicate to maintain homeostasis

• There are two systems used for communication in
  your body
• The nervous system controls and coordinates
  functions throughout the body and responds to
  internal and external stimuli with the use of
  nerves
• The endocrine system performs a similar function
  with the use of hormones

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Nervous Response

• Stimulus any change that results in a change in
  the organism.
• temperature, light, pressure, sound, smell, etc.
• Response any action resulting from a stimulus.
• contraction of muscle cells
• secretion by a gland
• stimulation of another nerve fiber.

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Neurons

• Messages carried by the nervous system are
  electrical signals impulses
• Nerve cells that transmit impulses neurons
• Sensory neurons carry impulses from sense organs
  to the spinal cord and brain
• Motor neurons carry impulses from the brain and
  spinal cord to muscles and glands
• Interneurons connect sensory and motor neurons
  and carry impulses between them

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Parts of a Neuron

• Cell body largest part containing nucleus and
  cytoplasm (most metabolic activity occur here)
• Dendrites short, branched extensions spreading
  out from the cell body and they carry impulses
  from the environment or other neurons towards the
  cell body
• Axon long fibers that carry impulses away from
  the cell body and ends at the axon terminal

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A Neuron
Section 35-2
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Nerves

• Neurons bundle together to form nerves
• Some nerves may be only a few neurons, and others
  may be hundreds or thousands
• The myelin sheath may insulate axons by
  surrounding it
• There may be some gaps in the myelin sheath
  called nodes
• Impulses jump from one node to the next,
  increasing the speed impulses travel

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Resting Nerve

• Nerve impulses are electrical
• The electric potential is created as the result
  of a sodium - potassium pump
• It uses ATP to pump sodium ions (Na) out and
  potassium ions (K) in active transport
• This results in a negative charge inside the cell
  membrane and positive charge outside resting
  potential

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Nerve Impulse

• An impulse begins when a neuron is stimulated by
  another neuron or by the environment.
• An impulse causes positively charged sodium ions
  to flow in temporarily reversing the charge of
  the cell membrane action potential
• As the impulse passes, positively charged
  potassium ions flow out and the charges restore
  to the normal resting potential

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Figure 35-7 An Impulse
Section 35-2
Action Potential
As the action potential passes, potassium gates
open, allowing K ions to flow out.
At rest.
Action Potential
Action Potential
The action potential continues to move along the
axon in the direction of the nerve impulse.
At the leading edge of the impulse, the sodium
gates open. The membrane becomes more permeable
to Na ions and an action potential occurs.
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Synapse

• At the end of the neuron, the impulse reaches an
  axon terminal where the impulse may be passed
  along to another neuron or another cell
• The location where a neuron can transfer an
  impulse to another cell synapse
• The synapse is a small gap that separates the
  axon terminal from the dendrites of the next
  neuron or another cell
• The terminals contain tiny sacs or vesicles
  filled with neurotransmitters chemicals used by
  a neuron to transmit an impulse across a synapse
• The neurotransmitters stimulate the next neuron
• The impulse will continue with the stimulation
  exceeds the cells threshold

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Figure 35-8 The Synapse
Section 35-2
Direction of Impulse
Dendrite of adjacent neuron
Axon
Receptor
Vesicle
Axon terminal
Synaptic cleft
Neurotransmitter
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Reaction activity

• Reaction time the amount of time required for
  an impulse travel from your sensory neurons to
  your motor neurons

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The Nervous System

• Neurons work together forming the nervous system
• There are two major divisions of the nervous
  system
• Central nervous system (CNS)
• Peripheral nervous system (PNS)

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Parts of the Nervous system

• Central nervous system (CNS)
• Brain
• Spinal Cord
• Peripheral nervous system (PNS)
• Sensory division
• Motor division
• Somatic nervous system
• Autonomic nervous system

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Central Nervous System

• The CNS is the control center of the body
• Relays messages
• Processes information
• Analyzes information

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Brain and Spinal cord

• Both are
• protected by bone
• wrapped in 3 layers of connective tissue
  meninges
• layers may have a space between them filled with
  cerebrospinal fluid which protects (shock
  absorber) and exchanges nutrients and waste

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Brain

• About 100 billion neurons, mainly interneurons
• Major parts of the brain
• Cerebrum
• Cerebellum
• Brain stem
• Thalamus
• Hypothalamus

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Figure 35-9 The Brain
Section 35-3
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Spinal Cord

• Links communication between the brain and the
  rest of the body
• 31 pairs of spinal nerves branch out from the
  spinal cord connecting brain to body
• Reflexes quick, automatic responses to stimuli
  are processed directly in the spinal cord

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Figure 35-11 The Spinal Cord
Section 35-3
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Peripheral Nervous System
PNS animation (Pain receptor)
http//pennhealth.com/encyclopedia/em_DisplayAnima
tion.aspx?gcid000054ptid17

• Consists of nerves and associated cells that are
  not part of the brain or spinal cord
• Receives information from the environment and
  relays commands from the CNS to organs and glands
• Divided into two parts
• Sensory division transmits impulses from sense
  organs to the CNS
• Motor division transmits impulses from the CNS
  to the muscles or glands

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Somatic System

• Part of motor division that regulates activities
  that are under conscious control (movement of
  skeletal muscles)
• Some reflexes too

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What is a Reflex?

• A reflex is an involuntary behavior. Reflexes
  are usually coordinated in the spinal cord not
  the brain.
• They are present from birth
• They are automatic
• They are meant to protect the body
• Examples
• blinking (keeps your eyes hydrated)
• pulling your hand away when you touch something
  hot.
• changing pupil size as you move from dark to
  light.

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Receptors Effectors

• Receptor a specialized nervous tissue that is
  sensitive to a specific stimulus.
• nerve cells in skin
• eyes
• ears
• taste buds
• Effectors the part/s of the body that respond
• muscles or glands

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Reflex Arc

• The pathway that an impulse travels
• 1. from the sensory receptor
• 2. up the sensory neuron
• 3. over the synapse
• 4. to the spinal cord (interneuron)
• 5. over another synapse
• 6. back down the motor neuron
• 7. to the effector

Reflex arc animations 1. http//www.sumanasinc.c
om/webcontent/animations/content/reflexarcs.html 2
. http//msjensen.cehd.umn.edu/1135/Links/Animatio
ns/Flash/0016-swf_reflex_arc.swf
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Autonomic System

• Part of the motor division that regulates
  activities that are automatic or involuntary
  (heart beat and smooth muscle in digestive system
  and blood vessels)
• Two parts that have opposite effects on the
  organs they control
• Sympathetic (gas pedal)
• Parasympathetic (brake)

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Concept Map
Section 35-3
The Nervous System
is divided into
which consists of
that make up
which is divided into
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Sensory Receptors

• Neurons that react directly to stimuli from the
  environment and send impulses to other neuron and
  CNS
• Light
• Sound
• Motion
• Chemicals
• Pressure
• Changes in temperature

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Sense organs

• Sensory receptors are concentrated in the sense
  organs
• Eyes
• Ears
• Nose
• Mouth
• Skin

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Types of Sensory receptors

• Sensory receptors within each organ enable it to
  respond to particular stimuli. The five general
  categories of sensory receptors are
• Pain receptors
• Thermoreceptors
• Mechanoreceptors
• Chemoreceptors
• Photoreceptors

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The 5 Senses

• See
• Hear
• Smell
• Taste
• Touch

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See (Vision)

• Photoreceptors sense light

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Hearing and Balance

• Sound vibration in air detected by
  mechanoreceptors
• Balance As head moves, fluid shifts and hair
  cells bend and send impulses to the CNS to
  determine body motion and position

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Smell

• Smell ability to detect chemicals detected by
  chemoreceptors in nasal passageway and send
  impulses to CNS through sensory nerves

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Taste

• How food tastes is strongly influenced by smell
• Taste ability to sense chemicals by
  chemoreceptors in taste buds mostly on tongue
  (sweet, sour, salty and bitter sensitivity is
  different on different parts of tongue)

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Touch

• Skin largest sense organ containing pain
  receptors, thermoreceptors, and mechanoreceptors

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Senses activity

• Different parts of skin have different
  sensitivity because theres a different numbers
  of receptors at different locations

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Problems

• Drugs substance that changes the structure or
  function of the body
• Drugs can interfere with the action of
  neurotransmitters at the synapse, which can
  disrupt the functioning of the nervous system

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Stimulants

• Increase the actions regulated by the nervous
  system by increasing the release of
  neurotransmitters at synapses (increase heart
  rate, blood pressure, and breathing rate)
• Amphetamines
• Cocaine
• Nicotine
• Caffeine

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Depressants

• Decrease the actions regulated by the nervous
  system (lowering heart rate, breathing rate,
  blood pressure, relaxing muscles, and relieving
  tension)
• Alcohol
• Tranquilizers

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Alcohol

• One of the most dangerous and abused depressant
  drug that slows down functioning rate of CNS
• Fetal alcohol syndrome (FAS) a group of birth
  defects caused by the effects of alcohol on the
  fetus (heart defects, malformed faces, delayed
  growth, and poor motor development
• Alcoholism disease of people who have become
  addicted to alcohol
• Causes damage to liver where alcohol is broken
  down

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Addictions

• Some drugs that act on neurons of the pleasure
  centers of the brain can produce an addiction
  an uncontrollable craving for more of the drug or
  dependence on a drug
• Cocaine causes sudden release of the
  neurotransmitter dopamine
• Opiates mimic natural endorphins to overcome
  pain
• Marijuana produces temporary feeling of
  euphoria and disorientation
• Drug abuse using any drug in a way that most
  doctors couldnt approve

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Commonly Abused Drugs
Section 35-5