Transcript CHAPTER 21 THE NERVOUS SYSTEM and SENSES

CHAPTER 21
THE NERVOUS SYSTEM and SENSES
• Homeostasis-maintaining a constant internal
balance; responding to stimuli
• Stimuli- an external or internal change that
brings about a stimuli
• NERVE CELLS•
Neurons- nerve cells that are made up of
axons, dendrites and cell body.
•
•
Axons- carry impulses away from the cell
body
Dendrites- carry impulses to the cell body
• Sensory neurons- send impulses (information) to
the brain and spinal cord
•
interneurons-found in brain and spinal cord
and send impulses from sensory neurons to
motor neurons.
•
Motor neurons- relay information to muscles
or glands in the body.
• IMPULSE TRANSFER
• Impulse moves from axon of one neuron to
dendrites of another; moves across synapse
• Synapse- space between axon and dendrites
•
neurotransmitters-chemicals that are
released that carry impulse across synapse
• http://www.youtube.com/watch?v=90cj4NX8
7Yk&feature=related
• Central Nervous System (CNS)
• -made up of brain and spinal cord
• Peripheral Nervous System (PNS)
• -made up of all nerves outside of CNS; all nerves
in your head and coming off of spinal cord
• BRAIN
• Three parts
•
1) Cerebrum- largest part; where thinking
occurs; memory is stored; movements are
controlled
•
Cortex- outer portion; have ridges
and grooves that increase surface area so
more complex thoughts can occur
• 2) Cerebellum-under cerebrum; coordinates
voluntary muscle movements, maintain
balance and muscle tone. i.e.) helps ride a
bike
• 3) Brain Stem- base of brain; connects to
brain to spinal cord
•
a) Contains medulla-controls
involuntary actions like heartbeat, breathing,
blood pressure, coughing, sneezing,
swallowing and vomiting.
• SPINAL CORD
•
-in adult is as wide as adult thumb
-carries impulses from the body to the
brain and from the brain to the body
• http://www.youtube.com/watch?v=90cj4NX8
7Yk&feature=related
• Reflexes
• -involuntary automatic response to a stimulus
• -controlled in your spinal cord
•
-brain acts after reflex to help you figure
out what to do to make pain stop
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•
•
•
Drugs
-directly affect the nervous system
-destroy brain and liver cells
-can be a depressant and slow down
responses of CNS as well as thinking processes
• -can be stimulant that speeds up heart rate,
cause sleeplessness and can cause kidney to
make more urine
• http://www.amenclinics.com/brainscience/spect-image-gallery/spectatlas/images-of-alcohol-and-drug-abuse/
• http://video.about.com/alcoholism/Cirrhosisof-Liver.htm
• SENSES-taste, touch, smell, sight, hearing
• http://www.kidcyber.com.au/topics/body_sen
ses.htm
• http://www.nlm.nih.gov/medlineplus/ency/
anatomyvideos/000109.htm
• SIGHT
• Nearsighted-focus in front of retina
• Farsighted-focus behind retina
• Parts of Eye:
• Cornea-transparent membrane that protects
the eye-allows light to enter
• Pupil-opening the front of the eye that allows
light to enter
• Retina-light sensitive area in the back of the
eye
•
-rods-detect dim light; used in night vision
•
-cones-detect colors
• *impulses from these photoreceptors travel to
brain along the optic nerve
• Iris-the part of the eye gives it its color
• Lens-piece of curved material behind the pupil
that allows the light to pass through but
changes its direction.
•
-focuses entering light on the retina
•
-looking at objects close to the eye-lens is
more curved
•
-looking at objects far away- lens is flatter
• Hearing
• -sound begins when object starts to vibrate
b/c air particles push on each other and
transfer energy.
• -waves move from outer ear to middle ear
(causes tiny bones in eardrum to vibrate) to
cochlea of the inner ear fluid
• -neurons in cochlea convert waves to
electrical impulses and sends them to the part
of the brain that interprets sound.
• http://www2.worksafebc.com/Publications/M
ultimedia/Videos.asp?reportid=34284
• TASTE
• Taste buds - contain receptors for taste;
located in the papillae
•
Four types- sweet, sour, salty, bitter
• SMELL
• Olfactory cells- receptors for smell that are
located in the upper part of your nasal cavity.
• -brain combines information from your taste
buds and nose to give a sense of smell.
• http://videos.howstuffworks.com/tlc/29841understanding-the-smell-center-video.htm
• http://videos.howstuffworks.com/howstuffwo
rks/461-how-smell-works-video.htm
• Touch Touch receptors are the nerve cells that
tell your brain about tactile sensations. There
are several types of touch receptors, but they
can be divided into two groups.
• (1) mechanoreceptors that tell you about
sensations of pushing, pulling or movement,
– The mechanoreceptors contain the most types of
touch receptors.
• (2) thermoreceptors that tell you about
sensations of temperature.
• Types of Mechanoreceptors
• Free nerve endings informs the brain about
pain, and they are located over the entire
body.
Pacinian corpuscles detects pressure, telling the brain
when a limb has moved. After the brain has told a limb,
such as an arm, to move, the pacinian corpuscles tells
the brain that that limb has actually moved into the
correct position.
The Tactile Corpuscles of Meissner are grouped on the skin of
the fingertips, lips, and orifices of the body and the nipples. Only
stimulated when touched, meissner corpuscles tells the brain
the shape and feel of an object in the hand. They adjust
constantly to the environment, which is why the brain eventually
ignores clothing that you are wearing.
• Thermoreceptors are the other major group
of touch receptors.
There are two types of thermoreceptors:
• A) end-bulb of Krause, which detects cold
• B) Ruffini's end organ, which detects heat.
The end-bulb of Krause can be found in the skin, conjunctiva,
lips, and tougue
Ruffini's end organs are found over the entire
body in the skin.