Q: What is the most complex
entity in the known universe?

A: The human brain
The human brain consists of about
100 billion nerve cells!
 A given neuron may have several
thousand connections; therefore,
the human brain has at least
100,000,000,000,000 web-like
connections. WOW!
 One hundred trillion connections is
larger than the total number of
atomic particles that make up the
known universe (Thompson, 3).

Biology and Behavior
The Nervous System –

All living organisms have a nervous system.

The nervous system varies depending on the
species.

The human nervous system is the most
complex of all species.

The human nervous system is involved in
thinking, dreaming, feeling, moving, and
everything that makes you … well you!

The nervous system also regulates all our
internal functions.
1.
Division –

The nervous system is divided into two main
parts:


The Central Nervous System (CNS)
The Peripheral Nervous System (PNS)
The Central Nervous System






The central nervous system consists of the brain and the
spinal cord.
The spinal cord extends from the brain and down the back.
The spinal cord is a bundle of neurons about as thick as an
adult’s thumb.
The spinal cords function is to transmit messages between
the brain and the muscles, organs, and glands through the
body.
The spinal cord is also involved in spinal reflexes.
A spinal reflex is a simple, automatic response to a sudden
stimulus – where the sensory receptor is stimulated and
the message is sent to the spinal cord only and a response
is sent immediately from the spinal cord to the extremity.
The Peripheral Nervous System


The peripheral nervous system is made up of all the
neurons that send messages to the central nervous
system from all parts of the body.
The peripheral nervous system is divided into two
parts:
a) The Somatic Nervous System
b) The Autonomic Nervous System
Organization of the Nervous
System
Nervous
System
Central
NS
Brain
Spinal
Cord
Peripheral
Somatic
Autonomic
Sympathetic
Parasympathetic
Divisions of the Nervous
System
The Somatic Nervous System
The somatic nervous system transmits sensory messages
to/from the central nervous system.
 The somatic nervous system is activated by touch, pain,
change in temperature, and changes in body position, as well
as muscular movement.
 The somatic nervous system allows us to experience the
sensations of hot and cold, and to feel pain and pressure.
 The somatic nervous system sends messages to the muscles
and glands and helps us maintain posture and balance.

The Autonomic Nervous System
The “autonomic” means “occurring
involuntarily” or automatically.
 The autonomic nervous system regulates the
body’s vital functions, such as heartbeat,
breathing, digestion, and blood pressure.
 The autonomic nervous system is involved in
the experience of emotion.

The Autonomic Nervous System (continued)

The autonomic nervous system is divided into two
parts:
– a) the sympathetic
– b) the parasympathetic
These two parts work in opposition.
The sympathetic is activated when a person is going
into action, perhaps because of some stressful
situation.
 The sympathetic nervous system prepares the body
either to confront the situation or to run away. This is
called the “flight or fight” response.


– Example: Attacked by a large angry dog – The sympathetic nervous
system suppresses digestion, increases the heart and respiration rates,
and elevates the blood pressure, preparing the body to deal with the
situation (run or fight).

The parasympathetic nervous system restores the
body’s reserves of energy to normal levels, after an
action has occurred.
Sympathetic Nervous System
*Flight or Fight Response
*Automatically accelerates heart rate,
breathing, dilates pupils, slows down
digestion.
Parasympathetic Nervous System
Automatically slows
the body down after
a stressful event.
 Heart rate and
breathing slow down,
pupils constrict and
digestion speeds up.

Neural and Hormonal
Systems
Will Explain Why We FEEL……
Nervous
Strong
Pain
Sick
It all Starts with the Neuron
The Neuron = Nerve Cell



Neurons run through our entire bodies
and communicate with each other.
Each person has approx. 100 billion
neurons, most of which are found in the
brain.
There are three basic types of neurons:
1.
2.
3.
Motor neurons
Sensory neurons
Interneurons
Sensory Neurons
(Afferent Neurons)
 Take
information from the
senses to the brain.
Motor Neurons
(Efferent Neurons)
 Take
information from brain to
the rest of the body.
Inter Neurons
 Take
messages
from Sensory
Neurons to
other parts of
the brain or to
Motor Neurons.
Neural Anatomy & Physiology

Every neuron consists of: a cell body (soma),
dendrites, and an axon with axon terminals
Neural Anatomy & Physiology
Synapse
Neurotransmitters (chemicals held in terminal
buttons that travel through synaptic gap)
Synapse
Neural Anatomy & Physiology (continued)


The cell body (soma) produces energy that
fuels the activity of the cell.
Dendrites are thin fibers which branch out from
the cell body.


Dendrites receive information from other neurons and
pass the message through the cell body.
The axon carries messages away from the cell
body and towards the axon terminals.

A neuron has many dendrites but only one axon. Axons
vary greatly in length.
Neural Communication
Neurons
 The building blocks are neurons (i.e., nerve cells).
 Each neuron consists of a cell body (soma) and its
branching fibers, called dendrites.
 The information is passed from soma to the axon down
to the axon terminals across the synaptic cleft to other
neurons or to muscles or glands.
 A layer of fatty tissue, called myelin sheath, insulates
the axons of some neurons and helps speed the
electrical transmission (impulse).
 Evidence of myelin sheath’s importance appears in
multiple sclerosis – a disease in which myelin sheath
degenerates.
 Depending on the type of neuron, the neural impulse
(electrical impulse) travels at speeds ranging from a
sluggish 2 miles per hour to 200 or more miles per hour.
Candy Neuron
* Cell Body (Soma) – Marshmellow (1)
*
*
*
*
Dendrites – Pretzels (6)
Axon – Twizzler (1)
Terminal Branches – Mike And Ikes (6)
Terminal Buttons - M&Ms (6)
Directions: Label AND Define each part
of your neuron – then snap a picture of
your completed neuron and upload this
picture to Edmodo.
*For 2 extra credit points, upload a
picture of YOU with your candy neuron
to Edmodo! Candy Neuron Selfie!!!
Neural Communication




The fluid interior of a resting axon has an
excess of negatively charged ions, while the
fluid outside the axon membrane has more
positively charged ions.
This positive outside / negative inside polarization is
called the RESTING POTENTIAL.
Neurons at rest have a slightly negative charge
Neuron firing is an electrochemical process
*electrical inside the neuron
*chemical outside the neuron (in the synapse in the
form of neurotransmitters)
Neural Communication





A neuron fires an impulse when it receives
signals from sense receptors stimulated by
pressure, heat, light, or a chemical message from
adjacent neurons.
This impulse is called the ACTION POTENTIAL – it is a
brief electrical charge that travels down the interior of
the axon, like a line of dominoes falling, each one
tripping the next ion channel changing the polarity of
the nerve cell (all the way down the axon and into the
axon terminal).
A handful of neurons together produce enough power to
light up a flashlight bulb.
Neurons, like batteries, generate electricity from
chemical events.
This involves the exchange of electrically charged atoms,
called ions.
Neural Communication






From hundreds, even thousands of other neurons,
a single neuron receives signals on its dendrites
and cell body.
Some signals are excitatory, somewhat like pushing a
neuron’s accelerator.
Some signals are inhibitory, more like pushing the
brakes, signaling the neuron to stop sending an electrical
impulse.
The neuron’s threshold for firing an impulse is an all-ornone response, like a gun – it either fires or it doesn’t.
Neurons interweave so intricately that even with a
microscope it is hard to see where one neuron ends and
another begins.
The axon terminal of one neuron and the dendrite of
another neuron are separated by a gap less than a
millionth of an inch wide. This gap is called the
SYNAPSE.
Let’s Do the Neuron Dance!!!
Neurotransmitters
Chemical messengers released by
terminal buttons through the synapse
 We should know at least 5 types and
what they do.

Norepinephrine

Circuits in the brain arise from a small
collection of neurons in the brain stem and
project to all forebrain structures. It is
thought to moderate levels of arousal and
consolidate memory (interneuron).
 Its
Acetylcholine
function is motor movement
and maybe memory.
To much and you will….
Not enough and you will….
Lack of ACH has
been linked to
Alzheimer’s
disease.
Dopamine



Deals with motor
movement and alertness.
Lack of dopamine has
been linked to
Parkinson’s disease.
Too much has been
linked to schizophrenia.
Serotonin
Function deals with mood
control
Lack of serotonin has
been linked to
depression
This is one mildly
depressed sheep!!! I guess
we should try to shear her
up (get it?)
Endorphins
Function deals with pain control
 Produces “runner’s high”
 We become addicted to
endorphin- causing feelings.

Drugs can be…..



Agonists- make neuron fire / produce
temporary high by amplifying sensations
of arousal or pleasure
Antagonists- stop neural firing / inhibit
Reuptake Inhibitors- block reuptake;
the sending neuron normally reabsorbs
excess neurotransmitter molecules