Transcript Nervous System

School House Rock—
Nervous system
Nervous System
Read Ch 7
Review pg 248:
S/A #6, 9, 12, 14
Clinic #2, 5, 10
Read Ch 8
Review pg 277:
S/A #5, 9, 14, 21
Clinic 2, 3, 7
Divisions of the Nervous
System
Central Nervous
System
•Command center of the
NS
•Integrates all impulses
•Consists of brain and
spinal cord
•Enclosed in
bone…nerves aren’t
very sturdy!
Divisions of the Nervous
System
Peripheral Nervous
System
•Consists of all nerves
coming from CNS
•Cranial nerves (12 pair)
•Spinal nerves (31 pair)
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/spindle.gif
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Nerves are amitotic (will not replicate)
because they have no centrioles.
Cranial
Nerves
Spinal
Nerves
Nerve
Anatomy
Functions of Nerve
“parts”
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Cell Body—Metabolic Center
Dendrite—branched projections
conveying messages TOWARD the cell
body
Axon—single, elongated projection
conveying messages AWAY from the
cell body
Functions of Nerve
“parts”
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Myelin—whitish, fatty material that protects
and insulates nerve fibers. Myelin increases
transmission rates. Impulse speed
~400ft/sec!
Synapse—tiny gap separating each axon
from the next neuron.
Nodes of Ranvier—indentations between
each myelinated section of axon
Functions of Nerve
“parts”

Neurotransmitters
—chemicals that
must be present
to transmit
impulses to next
neuron
Types of Neurons
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Sensory (Afferent)
neurons—conveys
impulses to CNS
from rest of body
Motor (Efferent)
neurons—conveys
impulses from CNS
to muscles and
glands
Types of Neurons

Interneurons (Association neurons)—
connect sensory and motor neurons…only
found in CNS.
Spinal Cord
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17 – 18” long travels from occipital
bone to 1st or 2nd lumbar vertebrae
~ thickness of thumb
Primary reflex center
Carries impulses to and from the brain
via a 2-way conduction system
(ascending and descending tracts)
Spinal nerves are named by vertebrae
type and number
Spinal Cord
functions
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Connect PNS and
CNS
Control reflexes
Reflex Arc
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Involuntary response in which the brain
ISN’T involved
Reflex arcs con’t:
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Two-neuron arc
Egs: knee jerk, blinking, AB reflex
Pathway:
Sensory Neuron
Motor Neuron
Reflex arcs con’t:
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Three neuron arc
Egs: hot object, getting a cut
Pathway:
Sensory neuron
Interneuron
Motor Neuron
Brain
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Size: ~2 fists together
Mass: ~3#
Texture: Oatmeal
No sensory neurons
100 billion neurons made prior to birth, will
undergo mitosis until 15 – 18 years of age.
Cerebrum
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Function:
Responsible for
thinking, reasoning,
all willed
movements.
Other info:
Largest, uppermost
part
Functions of cerebral lobes
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Frontal: Intelligence, reasoning, use of
skeletal muscles
Occipital: Visual
•Parietal:
Speech,
reading, pain,
cold, touch,
taste
•Temporal:
Smell, hearing,
memory
Diencephalon
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Located between
midbrain and
cerebrum
Composed of
Thalamus and
Hypothalamus
Thalamus
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Function: Relays
info to Cerebrum,
associates
sensations with
emotions
Other info:
Dumbbell shaped
section of grey
matter, key part of
alerting mechanism
Hypothalamus
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Function: Controls
Autonomic Nervous
System, (temp,
metabolism, H2O
balance)
Other info: Crucial in
maintaining sleep
cycles, appetite,
pleasure, fear, sexual
arousal, anger and
pain.
Pons
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Function: Controls
breathing, facial
expressions
Other info:
Consists of white
matter with
scattered bits of
grey.
Medulla Oblongata
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Function: Regulates
involuntary responses
(heartrate, BP,
swallowing, breathing)
Other info: Enlarged
upward extension of
spinal cord, consists of
both grey and white
matter
Cerebellum
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Function: Coordinates skeletal muscles,
balance, and posture
Other info: 2nd largest part of brain
Meninge Layers
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Dura Mater (outer)
– Function: Tough attachment to skull
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Pia Mater (inner)
– Function: Exchange point
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Arachnoid Mater (middle)
– Function: Take nutrients and O2 to
brain and carry waste products away.
Meninge Layers
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Other info: These areas are fluid
filled membranes surrounding the
brain and spinal cord. The
cerebrospinal fluid fills in the
space between the pia and
arachnoid maters.
Peripheral Nervous
System
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Somatic Division = Voluntary control
Pathway
Brain
Peripheral Nervous
System
End Effect:
Muscle or gland
Stimulated
Spinal cord
Spinal cord
Motor Neuron
Peripheral Nervous
System
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Autonomic Division = NO voluntary
control
Responsible for most vital functions
– Heartrate, breathing, temp reg, etc.
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Pathway:
Brain
Spinal cord or
Cranial nerves
Motor nerves
End Effect
Autonomic Division con’t:
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Divided into Sympathetic and
Parasympathetic Nerves
– Sympathetic—functions as
emergency system (fight or flight)
– Parasympathetic—counteracts the
sympathetic; responsible for normal,
everyday lives. (resting, digesting,
etc)
Parasympathetic
vs Sympathetic
Parasympathetic
vs Sympathetic
Organ
Sympathetic
Parasympathetic
Heart
Stimulates
Represses
Digestive
Tract
Blood
Vessels
Bladder
Slows
Speeds up
Mostly
constricts
Relaxes
Mostly dilates
Bronchi
Dilates
Constricts
Iris of eye
Dilates pupil
Constricts pupil
Constricts
Senses--Vision
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Ciliary body and muscle—changes the shape
of the lens to allow focusing
Senses--Vision
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Iris—controls the amount of light
entering eye.
Senses--Vision
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Aqueous Humor—Watery fluid that
gives the front of the eye its shape.
Senses
Vision
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Lens—Directs
images to retina;
held in place by
ligaments.
Perfectly
transparent
in youth, will become
less flexible and
opaque in older
adulthood = hazy
vision = cataracts
Senses--Vision
 Cornea—
refracts light
into eye
Senses--Vision
Vitreous humor—gel-like fluid giving
the back of the eye its shape.
Senses--Vision
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Optic nerve—Takes image to brain; blind spot
exists where the optic nerve meets the retina.
Senses-Vision
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Sclera—Protective covering; forms white of
eye and transparent cornea
Senses--Vison
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Choroid coat—rich
supply of blood and
decides iris color
Retina—Picks up
image, made up of
photoreceptors
(rods and cones)
Senses—Taste
• 10,000 taste
buds—most on
tongue, some
on cheeks and
soft palate
•Other factors affect
• Taste buds do taste: aroma,
not regenerate! temperature,
texture
Senses--Smell
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Thousands of smell receptors occupy
a space the size of a postage
stamp at the top of the nasal cavity.
As chemicals dissolve in mucus in
area of smell receptors, the impulses
are transferred to the olfactory
nerve.
The olfactory nerve tires of a
continuous odor in < 5 minutes
Half of the people over 80 can’t
smell at all.
Senses—Hearing
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Outer ear
– Pinna
– Auditory canal
– Tympanic
membrane
Senses--Hearing
Middle ear
–Malleus
–Incus
–Stapes
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Inner ear
– Semicircular
canal
– Cochlea
– Eustachian
tube
– Auditory nerve
Senses--Hearing