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NERVOUS
SYSTEM
AIDS IN REMEMBERING, THINKING,
MOVING, BEING AWARE, AND
COORDINATING ALL OTHER BODY
FUNCTIONS TO MAINTAIN HOMEOSTASIS.
Chapter 9
2 PARTS OF THE NERVOUS SYSTEM


Central Nervous System (CNS)
 Brain and spinal cord
Peripheral Nervous System (PNS)

nerves
NERVOUS SYSTEM FUNCTIONS

SENSORY


INTEGRATIVE


Neurons contain sensory receptors (cells) at their ends.
 Detect changes inside and outside the body
 Convert information into nerve impulses that travel through the
PNS to the CNS
In the CNS, impulses are brought together creating sensations,
adding memory, producing thoughts, etc.
 Making conscious and subconscious decisions
MOTOR

Impulses are carried from the CNS to effectors (muscles and glands).
 2 categories
 Somatic Nervous System


Consciously controlled; skeletal muscle
Automatic Nervous system

Involuntary; heart, smooth muscle, glands
 Brain

and Spinal Cord
Protected by layered membranes called meninges.
Dura mater (outermost layer- contains blood vessels)
 Arachnoid mater (no blood vessels)
 Pia mater (thin, contains nerves and b.v that nourish
the cells of the brain and spinal
cord)
 Cerebrospinal fluid (CSF) –clear,
watery fluid b/w the arachnoid
and pia maters that is a shock
absorber. Secreted by masses
of specialized capillaries called
choroid plexuses.

BRAIN STRUCTURE AND FUNCTIONS

Contains 100 billion multipolar neurons.
4 MAIN PARTS OF BRAIN
Brain area
Location
Function
Cerebrum
Largest, most of cranial
cavity
Sensory and motor functions
Higher mental functions
-memory
-reasoning
Cerebellum
Posterior and inferior
region
Coordination
Balance
Muscle tone
Brain area
Diencephalon
Location
Middle
1. Thalamus
2. Hypothalamus
Brainstem
1. Medulla
2. Pons
3. Midbrain
Base of brain
Function
Limbic system-controls
emotional experience and
expression
1.Process sensory info (pain,
touch, temp)
2.Maintains homeostasis:
appetite center, sleep-wake,
water balance
Connect various parts of NS
Regulates visceral activities
1.Breathing, heart rate
2.Origin of cranial nerves
3.Coordinate head/eye
movements to sound& light
STRUCTURE OF CEREBRUM


Cerebral cortex is the outermost layer of gray matter that
contains 75% of all neuron cell bodies of the NS.
Left & Right cerebral hemispheres are connected by a
bridge of nerve fibers called the corpus callosum.


Dominant hemisphere-controls the ability to understand
language
Surface contains many ridges called gyri (gyrus) separated
by grooves. Shallow groove is a sulcus and a deep groove is
a fissure.


Longitudinal fissure separates the right and left hemispheres.
Transverse fissure separates the cerebrum from the cerebellum.
5
lobes-frontal, parietal, temporal, occipital,
insula (inner)
 4 ventricles
12 PAIRS OF CRANIAL NERVES
Nerve
1. Olfactory
2. Optic
3. Oculomotor
4. Trochlear
5. Trigeminal
6. Abducens
7. Facial
8. Vestibulocochlear
9. Glossopharyngeal
10. Vagus
11. Accessory
12. Hypoglossal
Function
smell
vision
moves/focus eye
moves eye
chewing
moves eye
facial expression, taste
equilibrium, hearing
swallowing
heart, digestion
neck
move tongue
Oh, Oh, Oh, To Touch And Feel Very Good Velvet, AH

SPINAL CORD (pg 247)
◦
Contains 31 segments, each giving rise to a pair of spinal nerves.
Foramen Magnum
-Where the spinal cord begins
Cervical Enlargement
-supplies nerves to upper limbs
Spinal Cord
Vertebral Canal
Lumbar Enlargement
-supplies nerves to lower limbs

Cross section of spinal cord (pg. 233)
Posterior Sulcus: divides spinal
cord into right and left halves.
White Matter:
myelinated
neurons
Contains CSF
Unmyelinated neurons
Anterior fissure
Divides spinal cord into right
and left halves

Spinal Cord
Functions (pg. 234)
1. Conducting impulses
2 way communication
system
 Ascending tracts: carry
sensory info to the
brain (afferent=arrives)
 Descending tracts:
conduct motor impulses
from the brain to
effectors (efferent=exit)

2. Spinal Reflexes:
 Patellar Reflex
 Withdrawal Reflex
NERVE PATHWAYS (PG. 229)
Are routes nerve impulses follow as they travel
through the nervous system.
 The simplest of these pathways includes only a few
neurons called a reflex arc.
 Reflexes are automatic responses to stimuli that
help maintain homeostasis.




Heart rate
Coughing
Breathing
blood pressure
vomiting
sneezing


Patellar reflex: uses only 2 neurons (sensory
and motor), helps maintain upright posture
Withdrawal reflex: sends sensory messages
to spinal cord and out to motor neurons, aids
in limiting tissue damage caused by touching
something harmful.
NERVOUS SYSTEM FUNCTIONS

SENSORY


INTEGRATIVE


Neurons contain sensory receptors (cells) at their ends.
 Detect changes inside and outside the body
 Convert information into nerve impulses that travel through the
PNS to the CNS
In the CNS, impulses are brought together creating sensations,
adding memory, producing thoughts, etc.
 Making conscious and subconscious decisions
MOTOR

Impulses are carried from the CNS to effectors (muscles and glands).
 2 categories
 Somatic Nervous System


Consciously controlled; skeletal muscle
Automatic Nervous system

Involuntary; heart, smooth muscle, glands
THE TYPICAL NEURON
NEURONS

Nervous tissue contains masses of nerve cells called
neurons.
Specialized to react to physical and chemical changes.
 Transmit info in the form of electrochemical changes called
nerve impulses.
 Bundles of axons make nerves.
 Also contains neuroglial cells that provide physical support,
insulation,
and nutrients for neurons.

REVIEW OF
KEY NEURON
PARTS
CLASSIFICATION OF NEURONS
Vary in structure, size, shape, and the number of
connections they make with other neurons.
 3 major structural groups (pg. 218)




Bipolar: cell body has 1 axon & 1 dendrite (found in eyes, ears,
nose )
Unipolar: cell body has 1 axon (lead to PNS and CNS, can form
ganglia)
Multipolar: cell body has 1 axon & many dendrites (found in
brain and spinal cord)
3 major functions of
1) Sensory neurons (afferent)
•
•
•
neurons
Carry impulses from PNS to CNS
Receptor cells found at end of dendrites or in skin or
sensory organs
Most are unipolar
Interneurons
2)
•
•
•
In brain and spinal cord
Transmit impulses from one part of the brain or spinal cord
to another
multipolar
Motor neurons (efferent)
3)
•
•
Carry impulses out of brain or spinal cord to effectors
multipolar
NEUROGLIAL CELLS (PG. 215)

Neurons cannot exist without these cells

Outnumber neurons in CNS

Can divide (neurons do not normally divide)

4 TYPES
1)
•
2)
•
•
3)
•
•
•
•
•
Microglial cells
Support neurons and phagocytize bacterial cells and cellular debris
Oligodendrites
Align along nerve fibers
Provide insulating layers of myelin (myelin-forming cells)
Astrocytes
Found b/w neurons and blood vessels
Provide structural support
Regulate nutrient and ion concentration within tissue
Form scar tissue that fill spaces following an injury in the CNS
“blood-brain barrier”
•
Shields delicate tissue from chemical fluctuations
•
Some drugs can get in some can’t
4.) Ependymal cells

Forms an epithelia-like membrane that covers specialized
brain parts (cells that line the central canal)

Forms inner linings that enclose spaces within the brain
and spinal cord
*Schwann Cells: are neuroglial cells that form a myelin
sheath around axons.
SO HOW DO NEURONS
COMMUNICATE WITH EACH
OTHER??????
IMPULSES TRAVEL FROM ONE
NEURON TO ANOTHER TO REACH THE
CNS BY CROSSING A SYNAPSE
THE SYNAPSE

The junction between two communicating neurons








Synaptic cleft: the gap between 2
communicating neurons.
Synaptic transmission:
-process of the impulse crossing
the cleft
-one-way process carried out by
neurotransmitters
-neurotransmitters can be excitatory
or inhibitory
-about 50 neurotransmitters in
nervous system (pg. 226 chart)
4
3
Steps of a Nerve
Impulse/ Synaptic
Transmission
5
2
6
1
Nerve Impulse Animation
NERVE IMPULSES – ACTION POTENTIAL
o
The surface of a cell membrane is polarized (electrically charged)
o
At rest, membrane potential is negative and the membrane is polarized.
Na+++++++++++++
K+++++++++++
K+++++++++++
Na++++++++++++++

When the membrane reached its threshold stimulus, Na channels open, Na ions
diffuse in, and membrane is depolarized.
K+K+Na+Na+
Na+Na+ K+K+

K channels open, K ions diffuse out, and the membrane repolarizes.
Na+++++++
K++++++
NERVE IMPULSES –ACTION POTENTIAL
A wave of action potentials travels the length of
the axon as a nerve impulse.
 Nerve impulse conduction is an ALL-OR-NONE
response – if neuron responds at all, it responds
completely!

VIDEO
Nerve Impulse & Action Potential

A wave of action potentials is occurring
throughout the membrane of a neuron.
*This is an ALL-OR-NONE response*
SYNAPSE AFFECTORS/OTHER PROBLEMS



Caffeine: stimulates the nervous system by lowering the
threshold at the synapse so neurons are more easily
excited.
Antidepressants: keeps the neurotransmitter, serotonin,
in the synapse longer.
Epileptic seizures: caused when nerve impulses reach
the synaptic knob to fast, exhausting the
neurotransmitter.

Multiple sclerosis (MS): is a disease in which the
fatty myelin sheaths around the axons of the brain
and spinal cord are damaged, leading to
demyelinization and scarring. The body’s immune
system attacks and damages the myelin. Axons can
no longer effectively conduct signals. Symptoms
include muscle weakness, spasms, difficulty in
moving, coordination,
balance, speech, or
swallowing, visual
problems, fatigue, and
bladder and bowel
difficulties.
MISCELLANEOUS/PROBLEMS


Subdural hematoma: collection of blood from
broken blood vessels that will increase pressure
in the skull and will lead to functional losses or
death.
Cerebral palsy: partial paralysis and lack of
muscular coordination caused by damage to the
cerebrum.