Download The Nervous System

Division of the Human Nervous System
Nervous System (NS)
Peripheral NS
Autonomic NS
sympathetic
Central NS
Somatic NS
parasympathetic
Brain
forebrain
Cerebrum
Hippocampus
Amygdala
Thalamus
Hypothalamus
Spinal cord
midbrain
hindbrain
Cerebellum
Pons
Medulla
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The human nervous system is divided into
three sub-systems:
 The Central Nervous System (CNS): the brain and the
spinal cord
 The Peripheral Nervous System (PNS): nerves that
bring information to and from the CNS
 The Autonomic Nervous System: controls organs and
functions independently from the CNS
The Central Nervous System
The central nervous system includes the Brain and the
spinal cord
The average adult human brain weighs 1.3 to 1.4 kg
(approximately 3 pounds). The brain contains about 100
billion nerve cells (neurons) and trillions of "support
cells" called glia (glial cells).
The spinal cord is about 43 cm long in adult women and
45 cm long in adult men and weighs about 35-40 grams.
The vertebral column, the collection of bones (back
bone) that houses the spinal cord, is about 70 cm long.
Therefore, the spinal cord is much shorter than the
vertebral column
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Located inside of the cranium
Divided into three parts:
 The Cerebrum
 The Cerebellum
 The Brain Stem
See this website:
http://www.brainline.org/multimedia/interactive_brain/the_huma
n_brain.html?gclid=CO6kmfTFqrACFQoDQAodWDd0Sg
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The largest part of
the brain
The cerebrum is
composed of grey
matter (in the
cortex and the
limbic system) and
white matter (the
rest of the
cerebrum)
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The cerebral cortex, the outer part, is divided
into four lobes: frontal, parietal, occipital and
temporal

Each lobe has its own particular responsibilities:
 Frontal: movement, thinking, problem-solving
 Parietal: touch, pain and pressure information
 Occipital: visual information
 Temporal: auditory information
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The Cerebrum is
divided into two
Hemispheres.
The left hemisphere
controls the right side
of the body.
The right hemisphere
controls the left side of
the body.
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The thickness of the cerebral cortex varies from 2 to
6 mm. The right and left sides of the cerebral cortex
are connected by a thick band of nerve fibers called
the “corpus callosum”
In higher mammals such as humans, the cerebral
cortex looks like it has many bumps and grooves. A
bump or bulge on the cortex is called a gyrus (the
plural of the word gyrus is "gyri") and a groove is
called a sulcus (the plural of the word sulcus is
"sulci"). Lower mammals, such as rats and mice,
have very few gyri and sulci.
Functions of the Cerebral Cortex:
1. Thought
2. Voluntary movement
3. Language
4. Reasoning
5. Perception.

The inner part of the
cerebrum known as
the limbic system,
controls learning,
emotion and
memory (long-term
and short-term
memory)

The Hypothalamus
1. Controlling Body
Temperature
2. Emotions
3. Hunger

1. Sensory processing
2. Movement

4. Thirst
5. Circadian Rhythms
The Thalamus
1.
2.
3.
Amygdala and
Hippocampus
Emotions
Learning
Memory

1.
2.
3.
4.
5.
6.
7.
8.
Frontal Lobe
Planning
Organizing
Problem solving
Memory
Impulse control
Decision making
Selective attention
Controlling behaviour
and emotions
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
Olfactory Lobe
Relays Sensory Signals
to the Olfactory Tract
Sense of Smell
The
Cerebellum
The rear part of the brain
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Is responsible for:
 Posture
 Coordination of
movement
 Balance
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The bottom of the brain
between the thalamus and
spinal cord
Connects the brain to the
spinal cord.
This is where you will find
most of the cranial nerves.
Is responsible for:
 Sleep, waking & dreaming
 Heart rate, respiration & blood
pressure
 Coughing & sneezing
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Medulla Oblongata - The medulla oblongata functions
primarily as a relay station for the crossing of motor
tracts between the spinal cord and the brain. It also
contains the respiratory, vasomotor and cardiac
centers, as well as many mechanisms for controlling
reflex activities such as coughing, gagging, swallowing
and vomiting.
Pons - The pons is a bridge-like structure which links
different parts of the brain and serves as a relay station
from the medulla to the higher cortical structures of the
brain. It contains the respiratory center.
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A cord between 40 and 50 cm long found
inside the vertebral column
Made of grey matter (inside) and white matter
(outside)
Is responsible for:
 Transmitting nerve impulses
 Reflexes
The Peripheral nervous system includes all nerve
fibers that run in and out of the brain and spinal
cord.
A. Somatic Nerves - These are “Voluntary fibers” .
These are part of the Somatic nervous system.
1. Sensory fibers - bring impulses to the CNS
2. Motor fibers - bring impulses away from the CNS to the
voluntary skeletal muscles
B. Autonomic nerves - These are “Involuntary Fibers”
These are part of the Autonomic Nervous system
1. Sympathetic nerves
2. Parasympathetic nerves
Both of these fibers may activate or deactivate certain body
functions during times of stress or stimulus.
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Made up of nerves
 12 pairs of cranial nerves
 31 pairs of spinal nerves
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Types of nerves:
 Sensory nerves – carry info from the sensory organs
towards the CNS
 Motor nerves – carry info from the CNS to muscles and
organs
1. Sensory Neurons
2. Motor Neurons
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Reflexes are automatic, involuntary responses.
They are usually controlled by the spinal cord
Reactions involve the brain. The cerebrum
interprets sensory information and decides
how to respond
The Autonomic Nervous System is a part of the Peripheral
Nervous System.
It is made up of nerve Fibers that control involuntary body
action. It acts as a control system to maintain
homeostasis in the body.
There are two types of Fibers that connect to different
regions of the spinal cord
a) The Sympathetic fibers -thoracic and lumbar
b) The Parasympathetic fibers- cervical and sacral
What the sympathetic fibers do to a certain
part of the body the parasympathetic fibers
will have the opposite effect. Here are some
examples:
Sympathetic
Parasympathetic
Accelerates heartbeat
Slows heartbeat
Dilates pupil
Constricts pupil
Inhibits flow of saliva
Stimulates flow of saliva
Inhibits peristalsis
Stimulates peristalsis
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Neurons
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All of the organs and nerves of the nervous system
are made of neurons
Neurons are special cells that can send, receive and
transmit electrical messages called nerve impulses
Each neuron is made of:
 Dendrites
 An Axon
 A Cell Body
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Neurons are connected
to each other by small
gaps or spaces called
SYNAPSES
Nerve impulses are
carried across the
synapses by chemicals
called
NEUROTRANSMITTERS
The dendrites and axons of sensory neurons and motor
neurons that lie outside of the central nervous system in the
peripheral nervous system may be myelinated.
Myelin sheaths (neuron wraps) are formed by Schwann
Cells. Schwann cells form multiple layers of membrane
around the neuron and insulate it. In between the areas if
myelin sheath, Nodes of Ranvier or bare patches exist.
The nerve impulse or action potential (more on this later)
will jump form node to node greatly increasing the speed of
nerve transmission.
This node to node transmission, called saltatory conduction,
can produce transmission speeds of up to 200 meters per
second and explains the speed at which we can react to
potentially harmful stimuli.
Information from one neuron flows to another
neuron across a synapse. The synapse contains a
small gap separating neurons. The synapse
consists of:
1. Presynaptic ending that contains
neurotransmitters, mitochondria and other cell
organelles
2. Postsynaptic ending that contains receptor sites
for neurotransmitters
3. Synaptic cleft or space between the presynaptic
and postsynaptic endings.
Myelinated nerves can conduct
impulses at up to 720 km/hr