Download Nervous System

The Nervous System
Functions of the Nervous System
• Sensory - gathers info
• Integrative - information in brought together
to be processed and interpreted
• Motor - responds to signals, homeostasis
• Short term coordination of all other organ
systems’ activities
• Reflex responses (You don’t have to think
about it.)
Organization of the Nervous System
• Central Nervous System (CNS): includes
the brain and spinal cord.
• Acts as the integrating and command centers
• Interpret incoming sensory information and issue
instructions
• 98% of all neurons located here
• Peripheral Nervous System (PNS): includes
the nerves of the body
• Act as communication lines that link all parts of
the body
Organization of the Nervous System
Figure 12.2
The PNS is split into two subdivisions:
Somatic Nervous
System - allows us to
consciously control our
skeletal muscles (voluntary
nervous system)
Autonomic Nervous
System - Regulates events
that are automatic like
smooth muscles, cardiac
muscles and glands
NOTES – THE PERIPHERAL NERVOUS SYSTEM (PNS)
Autonomic Nervous System
1. Sympathetic - homeostasis and
the body at rest and is responsible
for the body's "rest and digest"
function.
2. Parasympathic - controls the
body's responses to a perceived
threat and is responsible for the
"fight or flight" response.
Types of Cells in the
Nervous System
Neurons
The type of nerve cell that transmits
information
Major parts of a neuron:
1. Cell Body – main part of
cell that contains the nucleus
2. Dendrites – short extensions
from the cell body, numerous,
receive information
3. Axons – single, long “fiber”
which conducts impulse away from
the cell body, sends information
4. Myelin -insulation surrounding axons
5. Nodes of Ranvier - gaps in the insulation
6. Schwann cell- is the small cells made up of myelin sheaths
that support nerve cells in the PNS.
The Nerve Cell
• Also called Neurons
• Highly specialized cell
• They cannot do mitosis
(Can’t reproduce)
• Born with all you are going
to get
Neuroglial Cells
- provide support for
neurons
1. Microglial Cells:
scattered throughout,
digest debris or
bacteria
Microglial cells respond to
immunological alarms
2. Oligodendrocytes:
provide insulation
around the axons
3. Astrocytes:
connect blood vessels
to neurons
I connect to
blood vessels
Neuroglial Cells (p 208)
4. Ependymal Cells: form a membrane that
covers brain-like parts
5. Schwann cells: form the insulating myelin
sheath around the neurons
Practice with neuroglia coloring!
• Cerebral White Matter
• functions to provide communication
between cerebral areas
•Myelinated axons
• also provides communication
between cerebrum and the rest of
the brain
• Cerebral Grey Matter
• contains the cell bodies,
dendrites and axon terminals of
neurons, so it is where all
synapses are (unmyelinated)
• Called soma
Interesting Facts about the Neuron
• Longevity – can live and function for a lifetime
• Do not divide – fetal neurons lose their ability to undergo
mitosis; neural stem cells are an exception
• High metabolic rate – require abundant oxygen and glucose
The nerve fibers of newborns
are unmyelinated - this
causes their responses to
stimuli to be course and
sometimes involve the whole
body. Try surprising a baby!
Label the Diagram
Types of Neurons
• Motor – carry information from the brain to the
body
• Sensory – carry the information from the body
to the brain
• Association – found only in the brain; transfers
information from the sensory to the motor
Neurons Classified by Function: Sensory vs. Motor Neurons
Figure 12.11
Transmission of a Nerve
Impulse
1. The dendrites are stimulated.
Stimulation can come from light, sound,
pressure receptors or your other senses, but most of
the time they are stimulated from other neurons.
Transmission of a Nerve
Impulse
2. Sodium channels open.
– Normally (when a nerve is at rest) it is positive
on the outside and negative on the inside
because Sodium (NA) is on the outside and
Potassium (K) is on the inside.
– When stimulated sodium channels open
allowing the positive sodium to flow in. This
changes the charge or polarity in the cell.
Nerve Impulses
At rest, the inside of a neuron's membrane
has a negative charge. As the figure shows,
a Na+ / K+ pump in the cell membrane
pumps sodium out of the cell and potassium
into it. However, more potassium ions leak
out of the cell. As a result, the inside of the
membrane builds up a net negative charge
relative to the outside.
Animations of Nerve Impulses
http://highered.mcgrawhill.com/sites/0072495855/student_
view0/chapter14/animation
__the_nerve_impulse.html
http://outreach.mcb.harvard.edu/
animations/actionpotential.swf
Transmission of a Nerve
Impulse
3. The membrane is depolarized
•
Depolarization is when the membrane
of the neuron changes so that now the
inside is more positive than the outside.
•
If the stimulus is strong enough, this
causes the polarity to completely change
and starts an action potential.
Transmission of a Nerve
Impulse
4. An ACTION POTENTIAL is
generated.
• An action potential is also called a nerve
impulse
• Nerve Impulses are an ALL or NONE
response. If enough stimulus occurs then
the nerve impulse will fire down the whole
axon. It will not go half way or die out.
When started it happens down the whole
Transmission of a Nerve
Impulse
5. The Action Potential reaches the
axon terminal.
Transmission of a Nerve
Impulse
6. Neurotransmitters are released
– Excitatory transmitters - increase membrane
permeability, increases chance for threshold to
be achieved
– Inhibitory transmitters- decrease membrane
permeability, decrease chance for threshold to
be achieved
Types of Neurotransmitters:
• Acetylcholine - stimulates muscle
contraction
• Norepinephrine & Dopamine (sense of
feeling good, low levels = depression)
• Serotonin (sleepiness)
• Endorphins (reduce pain, inhibit receptors)
Transmission of a Nerve
Impulse
7. The membrane of the post synaptic
neuron is activated.
The whole process then starts over with
the next neuron.
THE BRAIN
Major Divisions of the Brain
• 1. Cerebrum
• 2. Diencephalon
• 3. Brain Stem
• 4. Cerebellum
The Cerebrum
• Location: The most superior part of the
brain (the top part). Takes up the most
room. Has all the wrinkles in it.
The Cerebrum
What are all the bumps in it?
Gyrus = bump
Sulcus = shallow groove
Fissures = deep grooves that
separate the lobes of the brain
1. Longitudinal fissure - separates right and left sides
2. Transverse Fissure –
separates cerebrum from cerebellum
3. Lateral Fissure separates the temporal lobe from
the Frontal and Parietal lobes
The Cerebrum
• Functions of the Cerebral Cortex:
– Controls speech, memory, logical and
emotional response, consciousness,
interpretation of sensation, and voluntary
movement
• It is split into 4 major lobes
The Cerebrum
• Lobes of the cerebrum:
– Frontal – reasoning,
thinking, language
– Parietal – touch, pain,
relation of body parts
(somatosensory)
– Temporal Lobe – hearing
– Occipital – vision
The Cerebrum
• Specialized areas of the cerebrum
– Broca’s area- responsible for speech usually
located only in the left side. Damage to this
area causes the inability to say words properly
(you know what you want to say but you can’t
vocalize the words)
.
The Cerebrum
• Specialized areas of the cerebrum
– Basal Ganglia- help regulate volunteer motor
activities by stopping or starting movement. It
modifies instructions sent to the skeletal
muscles.
– Parkinson’s disease and Huntington’s disease
are disorders of the basal ganglia. (page 253254)
The Cerebrum
• Specialized areas of the cerebrum
– Corpus Collosum-connects the left and right
hemispheres
Take the Left Brain – Right Brain Test
The Diencephalon
• Location: Under the cerebrum, in the
middle of the brain. It sits on top of the
brain stem.
Parts of the
Diencephalon
1. Thalamus - relay station for sensory impulses
passing to the sensory cortex for interpretation
Parts of the
Diencephalon
2. Hypothalamus – most important regulatory
center of the autonomic nervous system
-controls temperature, water balance, &
metabolism
- also controls many drives and emotions (thirst,
appetite, sex, pain, and pleasure centers)
Parts of the
Diencephalon
-Pituitary Gland:
The "master gland" of the endocrine system. It
controls hormones. Ex: growth hormone
-Pineal Gland: secretes melatonin (for sleep)
Thalamus
Pineal gland
Hypothalamus
Corpus callosum
THE BRAINSTEM
Location: Bottom of the brain leading to the
spinal cord. Is about 3 inches long and the
width of your thumb.
THE BRAINSTEM
Parts of the Brainstem:
Midbrain- visual reflexes, eye movements
Pons- relay sensory information
Medulla Oblongata- regulates breathing, heart
rate, blood pressure
Medulla
Oblongata
Pons
Midbrain
CEREBELLUM
Location: lower, back of brain. It is under
the occipital lobe.
CEREBELLUM
• Function: Balance and coordination
Protection of the Brain
The Meninges & Cerebral Spinal
Fluid
•The Meninges
• 3 membranes that cover and
protect the brain & spinal cord
1. Dura Matter
• tough connective tissue
2. Arachnoid
• thin, transparent, no blood
vessels
3. Pia Matter
• Cerebrospinal Fluid
(CSF)
• inner membrane, delicate,
contains many blood vessels –
nourishment for cells of the cord
• watery broth similar to blood
plasma, important in protection
of nervous tissue
The Meninges
Figure 13.25a
Cerebrospinal Fluid (CSF)
Problems
• Meningitis- inflammation to the meninges.
It is a serious threat because the bacteria or
virus can spread to the CNS.
• Encephalitis- is inflammation of the brain
• Hydrocephalus- is water on the brain
because a tumor (or something) is blocking
drainage of the CSF. Treated with a shunt.
• A spinal tap is done to test CSF
Nerve Pathways
•
•
•
•
Reflex arc - only includes a few neurons
Reflex Behavior - automatic, subconscious responses
Knee-jerk reflex - maintains uprightedness
Withdrawal reflex - avoidance of painful stimuli
• Functions of the Spinal
Cord
• carry sensory impulses to brain
• carry motor impulses from
brain to muscles & glands
• Center for reflex activity
• Reflex Arc
(“no brainer”)
STIMULUS
SENSORY NEURON
INTERNEURON (in spinal cord)
MOTOR NEURON
MOVEMENT
• all of this happens BEFORE
signal is sent to the brain
(“no brainer”)
Drugs and the Nervous System
Drugs that Affect Synapses and Neurotransmitters
•
•
•
•
•
Curare
Strychnine
Cocaine, morphine, alcohol, ether and chloroform
Mescaline and LSD
Ecstasy
Dangers of Ecstasy (MDMA)
The neurotransmitter serotonin is vital
in regulating many of our basic
functions. Serotonin is, among other
things, the feel good neurotransmitter
and helps to regulate body temp.
Our brain cells are constantly trying to
bring some amount of serotonin back
into the cells and out of the synapse
using serotonin reuptake
transporters.
Ecstasy essentially takes these
upkeep transporters and reverses
their roles. This causes a massive
flood of serotonin from the brain cells
into the synapse.
The most common cause of
Ecstasy-related death is
overheating (hyperthermia).
MDMA interferes with the
body's ability to regulate its
own body temperature and
to see other warning signs
allowing the body to
overheat without discomfort
especially when dancing for
hours in hot clubs.
LSD; lysergic acid diethylamide
Actions/Effects: LSD alters the action of the neurotransmitters serotonin,
norepinephrine, and dopamine, triggering extreme changes in brain
function. Physical effects include increased body temperature, heart rate,
and blood pressure. Psychological effects include perceptual and thought
distortions, hallucinations, delusions, and rapid mood swings.
Cocaine blocks reuptake
of dopamine
Antidepressants
• Zoloft is part of a class of drugs called selective
serotonin reuptake inhibitors, or
• SSRIs for short. SSRIs act on a specific chemical
within the brain known as serotonin. This is one of
several chemicals used to send messages from one
nerve cell to another.
• Brain Disorders
(some examples)
• Parkinson’s
Disease
• deficiency of the neurotransmitter
dopamine
• Epilepsy
• sudden burst of irregular electrical
activity in brain – can lead to
seizures, convulsions
• Stroke
• blood clot in brain – paralysis
appears on side of body opposite to
side of brain affected
• Alzheimer’s
Disease
• part of cortex shrinks, neurons lost
• results in dementia, memory loss,
disorientation, loss of body function
Brain Injuries
• Concussion- brain is slammed into the
skull from an impact
– Disoriented, nausea, see “stars”
– May lose consciousness temporary
– No permanent brain damage
• Many concussions may lead to some
damage of the brain
• Contusion- Impact causes tissue
damage
– May cause a coma (temporary or long
term)
• Cerebrovascular Accident- Known as
a stroke
– Blood circulation to an area of the brain
is blocked.
– Some paralysis may occur
– Sometimes functions are recovered
Brain Diseases
• Schizophrenia
– may result in some combination of hallucinations,
delusions, and extremely disordered thinking and
behavior
– Risk factors – family history; exposure to viruses
toxins, or malnutrition in the womb; increased immune
system activation; older age of the father; taking mind
altering drugs during teen years or young adulthood.
– Treatment – medication and/or
psychosocial therapy for life.
Hospitalization may necessary.
• Depression
Brain Diseases
– Characterized by a persistent feeling of sadness and
loss of interest
– Causes – biological differences (makeup of the brain),
brain chemistry, hormones, inherited traits
– Treatments – medications and/or psychological
therapy. Some people may need a hospital stay.