Biology 3201 by E8S4V8u

VIEWS: 4 PAGES: 58

									      Biology 3201

Maintaining Dynamic Equilibrium
               II
          Nervous System
The nervous system is the body system that
   allows us to feel things. This happens by
   a network of nerves.

There are two main parts of the nervous
   system
1. Brain
2. Spinal Cord
Human Nervous System
 How the Brain and Spinal Cord
       are Protected…
By
1. Meninges- Spaces around the brain and
   spinal chord that act as buffer zones.
2. Bone (Skull/Vertebrae)- Act as a shield.
3. Cerebral Spinal Fluid – Absorbs energy
   when the brain of spinal cord receive a
   blow.
Meninges
                  The Brain
Parts we must know:
1. Cerebrum – Sorts and interprets all information
    from our senses.It is the center of human
    consciousness.
2. Cerebellum – Controls muscle coordination.
    Contains 50% of the brain’s neurons.
3. Medulla Oblongata – Controls heart rate, and
    force of heart contractions. Also controls reflex
    centers for hiccupping, vomiting, coughing,
    swallowing.
4. Pons – Functions with medulla to regulate
   breathing rate; has the reflex centers involved
   in head movement.
5. Hypothallamus – Controls hunger, body
   temperature, aggression.
6. Thalamus – Sorts sensory information.
7. Midbrain – Involved in sight and hearing.
8. Corpus Callosum – Series of nerve fibers that
   connect the left and right sides of the brain.
The Peripheral Nervous System
• Consists of the autonomic nervous
  system and the somatic nervous
  system.
– The autonomic nervous system is not
  consciously controlled.
– The autonomic nervous system is made up of
  the sympathetic and parasympathetic nervous
  system.
  • The sympathetic nervous system gets the body
    prepared for a fight or flight response.
  • It causes such things as increased heart rate,
    dilation of pupils, release of adrenaline, etc. (Refer
    to Figure 12.5)
     • The parasympathetic nervous system has the
       opposite effect of the sympathetic nervous system.
• The somatic nervous system is in some
  cases under our control.
  – It is made up of:
     • Sensory neurons that carry impulses from the
       body’s sense organs to the CNS.
     • Motor neurons that carry impulses away from the
       CNS to effectors (muscle fibers) that cause a
       response. (eg. Moving your hand away from a hot
       stove.)
Nervous System Response
In order for a nervous system response to occur
    there must be:
1. Information taken in by the senses (eyes, ears,
    skin, etc.)
2. Transmission of an impulse by neurons.
3. Interpretation of the impulse by the brain or
    spinal cord.
4. Effectors (muscle or glands).
The result is an impulse giving rise to a response if
    called a reflex arc.
The Neuron
The functional Unit of the Nervous system is
  called the neuron.
The PNS consists of nerves, which are
  neurons held together by connective
  tissue.
90% of the body nerves are found in the
  CNS.
Capable of living over 100 years.
The Neuron
The neuron consists of three main parts.
1. Cell body – Contains a nucleus, cytoplasm
   with mitochondria, lysosomes, a golgi complex
   and rough ER.
2. An axon – Is the long, cylindrical portion of the
   neuron. Can be 1mm to 1 m in length.
   Impulses are passed along the axon by a wave
   of depolarization.
3. Dendrites – The fingerlike projections that
   extend from the cell body. The receive signals
   from other neurons.
The Neuron
How an impulse is passed
The neuron at rest
Outside the neuron membrane
• +vely charged.
• High [] of Na+ ions. Lower []’s of K+ and Cl-.
Inside the neuron membrane
• High [] of K+. Lower []’s of Na+
• Dominant anions are proteins, amino acids,
  phosphates and sulfates.
At rest the Na+/K+ pump keeps the ion
  distribution.
Resting potential of the neuron is –70mV.
Depolarization
• As an impulse passes, there is a change
  in the charge of the membrane. This is
  called an action potential.
• Na+ channels open that allow ions to
  pass.
• K+ channels close.
Repolarization
• After the impulse passes the Na+ channels
  close.
• The K+ channels open to allow the ions out of
  the membrane.
• The Na+/K+ pump helps reestablish polarity.
The time between neuron impulses in called
  refractory period. For many neurons this can be
  ~0.001s.
The All-Or-None Response

   In order for an impulse to occur the stimulus
 need to be sufficient for the impulse to be sent.
 Ie. There is a Threshold that needs to be met in
 order for an impulse to occur.
 If the Threshold is met then an impulse will be
 sent along the length of the axon.
 The strength of the impulse is always the
 same, there is no mild of stronger impulse.
 The impulse either occurs or it doesn’t ie.
 Either all-or-none.
The Synapse
Once an impulse reaches the Axon terminals, it
  needs to cross the synaptic gap.
Neurotransmitters are released from the
  presynaptic neuron by exocytosis.
Receptor sites on the post synaptic neuron
  recieves the neurtransmitter.
This can cause either an excitatory response or
  inhibitory response.
The enzyme cholinesterase is released quickly to
  break down the neurotransmitter Acetylcholine.
Neurotransmitters
• Acetylcholine – Primary neurotransmitter of the
  somatic and parasympathetic nervous systems.
  May be excitatory or inhibitory.
• Noradrenaline (norephnephrine) – primary
  neurotransmitter of the sympathetic nervous
  system.
• Glutamate- the neurotransmitter of the cerebral
  cortex. Makes up ~ 75% of the neurotransmitters
  in the brain.
• GABA (gamma aminobutyric acid) – Most
  common inhibitory neurotransmitter in the brain.
Neurotransmitters
Dopamine – Elevates mood and controls
 skeletal muscles.
Seratonin – Involved in alertness,
 sleepiness, thermoregulation, and mood.
Requirements of the Nerve cell
Cells within the nervous system require enormous
 amounts of energy to function. This energy is
 provided by the processing of glucose and the
 production of ATP within these tissues, requiring
 an adequate supply of carbohydrates and
 oxygen (Na+/K+ pump). ATP energy is required
 to operate the sodium-potassium pump which
 convert cellular chemical signals into electrical
 signals along a nerve cell and in between
 individual nerve cells (i.e., synapse).
Core Lab #1 - Reflex Arc
What is a reflex arc?
It is the nerve pathway that leads from
   stimulus to reflex action.

Complete Pre-lab Question.
   Technology for Viewing the
            Brain
1. EEG (electroencephalograph): Invented
  by Dr. Hans Borger in 1924.
  This technology measures electrical
  activity in the brain.
  Allows doctors to detect and locate
  brain tumors and disorders such as
  epilepsy.
EEG
Technology Continued
2. Cat Scan: taking a series of cross-
  sectional X-rays to give a computer
  generated 3-D picture of any part of the
  body, including the brain.
Technology Continued
3. MRI (Magnetic Resonance Imaging): This
  technology uses a series of large
  magnets, radio frequencies and a number
  of computers to create a detailed view of
  the brain and other structures in the body.
MRI
Treating Stroke and Spinal Cord
             Injury
Stroke: Is caused by lack of oxygen to a particular
   part of the brain causing that portion of the brain
   to die.
 Treatments for stroke involve:
1. clot-busting drugs- drawback is that they need
   to be administered within three hours after the
   stroke occurs.
2. Asprin may also be administered to a person
   showing signs of stroke. Asprin decreases the
   chance of a clot by reducing stickiness of
   platelets (like the oil that you put in the engine
   of a car)
    Treatments for spinal cord injury (none as of
  yet): There is a large amount of medical
  research dedicated to finding a way to treating
  spinal cord injuries.
§    -Scientists have found a gene that inhibits the
  regeneration of the spinal cord and the CNS.
§    -Researchers hope to use this discovery to
  develop a therapy that will promote regeneration
  of the neurons in the CNS
EEG
MRI
PET Scan
• Shows activity of the
  brain by giving a
  coloured scan on a
  monitor. The more
  intense the colour the
  greater the activity.
Section 12.3 – The Sense
         Organs
       Eye and Ear
The Sense Organs: The Human
            Eye
What are the eyes protected by?

1.   Eyelashes
2.   Eyebrows
3.   Eyelids
4.   Bones in skull
The different parts of the eye:
How many can you think of?
1. Lens: The lens is a clear and flexible part of the
  eye.
    Its purpose is to focus light onto the retina.
    The lens is adjusted by ciliary muscles. These
  adjust the shape of the lens.

2. Iris: The iris opens and closes to control the
  size of the pupil. Which inturn restricts or allows
  more light to get into the eye.
    your iris is the coloured part of your eye. If
  you have green eyes, it’s because you have a
  green iris.
  3. Retina: The retina is the inner layer of the eye.
  It is composed of the photoreceptors of the eye,
  the rods and the cones
     The retina contains approximately 6 million
  cones.

 4. Rods: The rods are very sensitive to light, but
 they do no distinguish between different colors.
5. Cones are less sensitive to light but they
  are able to distinguish between colours.

6. Cornea: The cornea is the transparent,
  dome-shaped window covering the front of
  the eye.
    it is normally clear and has a shiny
  surface
7. Choroid Layer: Is the middle layer of the
  eye. Located between the retina and the
  outer layer of the eye.

a. It absorbs light
b. Prevents reflection of light within the eye
c. The choroids becomes the iris at the
  front of the eye
8. Fovea: The fovea is located directly
  behind the lens of the eye.
 The cones of the eye are concentrated
  within the fovea.
 This area of the eye is responsible for
  producing the most distinct image
9. Pupil: The pupil is the opening in the center of
    the iris. The size of the pupil determines the
    amount of light that enters the eye.
10. Blind spot: There is one area in the eye where
    there are no photoreceptors
    Because of this there is one place in the eye
    where you cannot see.
    Look at page 413
The Eye
                  Links
• http://www.nei.nih.gov/health/eyediagram/i
  ndex.asp
• http://www.exploratorium.edu/learning_stu
  dio/cow_eye/step01.html
Go to unitedstreaming.com
  Pathway of Light Through the
              Eye
  1. Light passes through the cornea
• 2. . Then through the iris
• 3. If there is a lot of light the pupil then
  constricts, if there is low amounts of light the
  pupil will dilate
• 4. The lens then adjusts its shape in order to
  aim the image at the retina.
• 5. Light hits the retina.
      The retina is composed of three layers: 1.
  ganglion layer 2. Bipolar layer 3. the rod and
  cone layer.
•    The rods and cones form the image
     The image is then transmitted to the
  ganglion layer via the bipolar layer of the
  eye.
     The impulse then exits the eye via
  the optic nerve
Layers of the retina (pg 412)
           Disorders of the Eye
In this course we will learn about 5 disorders of the eye.
1. Cataracts – cloudy or opaque areas on the lens
    • Get worse with age
    • Damaged lens can be replaced with an artificial
         one.
2. Glaucoma – Buildup of aqueous humor between lens
     and cornea.
    • The duct that normally drains the fluid becomes
         blocked.
    • Can cause nerve damage to nerves that aid in
         peripheral vision.
    • Can be helped with drugs.
3. Myopia (Near-sightedness) – Can see objects close up.
    – Usually caused by the eyeball being too long.
    – Therefore the image is focused in front of the retina.
    – Treated with concave lens
4. Hyperopia (Far-sightedness) – Can see objects far away
     but not close up.
    – Usually caused by short eyeballs.
    – The image is focused behind the retina.
    – Treated with convex lens
5. Astigmatism – Abnormal shaped lens or cornea,
     resulting in uneven focus.
    – Treated with uneven lens.
Refer to Figure 12.22 in text.
    Treatments of eye disorders
1. Laser treatment
    1. Photorefractive keratectomy (PKU)
       •   Outpatient procedure
       •   Reshapes cornea by removing microscopic amounts of
           tissue.
       •   Controlled by computer
    2. Laser in situ keratomileusis (LASIK)
       •   Helps repair near-sightedness
       •   Knife is used to cut the corneal flap.
       •   Laser is used to remove tissue underneath and flap is
           replaced.
       •   Controlled by surgeon.
•    Both treatments are highly successful.
2. Corrective lenses
3. Cornea transplant
  – When the cornea is beyond repair, a
    transplant can be performed.
  – Cornea comes from a donor, but doesn’t need
    to be matched. Ie any cornea can be used by
    any person.
  – Recovery can be up to 12 months.
  – Prognosis is usually very good.
The Ear
              Parts of the ear
1. Pinna – Channels sound waves into the
    auditory canal.
2. Tymphanic membrane (ear drum) acts like a
    drum head and vibrates as sound waves hit it.
3. Ossicles
  –   Malleus (hammer) – picks up vibrations from the ear
      drum. Vibrates and hits the incus (anvil)
  –   Incus (anvil) – Passes vibrations to the stapes.
  –   Stapes (Stirrup) – Passes vibrations to the Oval
      Window.
4. Eustachian tube (Auditory tube) – Tube behind
  the ear drum that allows pressure behind the
  eardrum to equalize.
5. Semicircular canals – Involved in balance and
  equilibrium. (Fluid filled)
6. Cochlea – Fluid filled – involved in hearing.
  Contains very tiny hairs that pick up sound
  vibrations.
7. Auditory nerve – Takes message away from ear
  to the CNS.
  Pathway of Sound in the Ear
1. Pinna focuses sound waves into the auditory
   canal.
2. Tymphanic membrane vibrates.
3. Vibrations are passed through the ossicles.
4. Sound waves pass through the oval window
   into the cochlea.
5. Hairs in the cochlea pick up sound and are
   changed to nerve inpulses.
6. Nerve impulses are taken away by the auditory
   nerve.
         Disorders of the Ear
There are two main types of deafness that a
  person can have; they are as follows:

1. Nerve deafness: Nerve deafness is caused by
   damage to hair cells in the spiral organ of the
   ear.
a. This type of deafness is usually uneven, ie.
   People with the disorders can hear certain
   frequencies better than others.
b. Damage cannot usually reversed and it
   continues to get worse as a person gets older.
2. Conduction deafness: This type of
  hearing disorder is caused by damage to
  the outer and middle ear
a. Conduction deafness affects the
  transmission of sound waves into the ear.
b. This type of hearing disorder doesn’t
  usually cause total hearing loss.
c. Hearing can usually be improved with the
  use of a hearing aid.
1. Eustachain tube implants: Many
  children have inner middle ear infections
  because their Eustachian tube is on an
  angle that does not allow proper drainage.
a. To prevent these infections, doctors can
  put tubes in the patients ears to allow
  proper drainage and pressure release.
Treatments for Ear Disorders
1. Hearing aids: There are several different types
   of hearing aids available; 1. Conventional
   2. Programmable, and 3. digital aids.
a. Conventional hearing aids have a
   microphone to receive sounds and an amplifier
   to increase their volume
b. Programmable hearing aids have an analog
   circuit that a professional such as an
   audiologists can program to the patients needs.
c. Digital Hearing aids can shape amplifications
   across various pitches and frequencies
   according to individual needs.

								
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