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Systems Regulating
Change in Humans
The Nervous System
A. Divisions of the Nervous System
http://www.youtube.com/watch?v=sjyI4CmBOA0
http://www.youtube.com/watch?v=x4PPZCLnVkA
The Nervous System - CrashCourse Biology #26
Nervous System
CNS
PNS
Brain
Spinal Cord
Autonomic
Sympathetic
Parasympathetic
Somatic
Sensory
Neurons
Motor
Neurons
A1. Central Nervous System
A. Protection


Surrounded by bone (skull and vertebrae)
Wrapped in meninges




Dura mater – superficial (“tough mother”)
Arachnoid – intermediate
Pia mater – deep, lies against the brain
Space between the meninges is filled with
cerebrospinal fluid (CSF) which absorbs shock,
nourishes, and eliminates waste
http://www.nlm.nih.gov/medlineplus/ency/imagepages/19080.htm
BLOOD BRAIN BARRIER
The Blood-Brain Barrier
The blood-brain barrier protects the neurons and glial cells in the brain
from substances that could harm them. Unlike blood vessels in other
parts of the body that are relatively leaky to a variety of molecules, the
blood-brain barrier keeps many substances, including toxins, away from
the neurons and glia.
Most drugs do not get into the brain. Only drugs that are fat soluble can
penetrate the blood-brain barrier. These include drugs of abuse as well
as drugs that treat mental and neurological illness.
The blood-brain barrier is important for maintaining the environment of
neurons in the brain, but it also presents challenges for scientists who
are investigating new treatments for brain disorders. If a medication
cannot get into the brain, it cannot be effective. Researchers attempt to
circumvent the problems in different ways. Some techniques alter the
structure of the drug to make it more lipid soluble. Other strategies
attach potential therapeutic agents to molecules that pass through the
blood-brain barrier, while others attempt to open the blood-brain barrier.4
A1. Central Nervous System
B. Brain

Two types of Nervous Tissue




White matter –myelinated, run in tracks (bundles)
Gray matter – unmyelinated
nerve cell bodies are often clustered together
into functional units called nuclei
Glial cells are cells within the nervous system
that provide support and nourishment to the
other cells
http://latourettesindrome.blogspot.com/2005_12_01_archive.html
www.ascd.org/.../books/jensen2005_fig1.2.gif
A1. Central Nervous System
C. Spinal Cord

Extends from the base of the brain into the
vertebral canal





Central root – contains CSF
Dorsal root – sensory information enters
Ventral root – motor information exits
Gray matter – centrally located, forms an “H”
shape, composed of interneurons
White matter – region around the gray matter that
takes information to the brain and delivers
information from the brain
A1. Central Nervous System
C. Spinal Cord
A2. Peripheral Nervous System
A. Somatic Nervous System

voluntary
http://normandy.sandhills.cc.nc.us/psy150/somatic.html
A2. Peripheral Nervous System
B. Autonomic Nervous System



Involuntary
Controls the internal environment, maintains
homestasis
Divided into two parts: sympathetic and
parasympathetic
A2. Peripheral Nervous System
B. Autonomic Nervous System
1) Sympathetic System

Looks like a string of pearls along the spinal
cord




Fight or flight response
Prepares body for emergencies
Everything is stimulated
Has ganglion (ganglia) - cluster of neuron cell bodies,
many connections to be made and many synapses
occur
A2. Peripheral Nervous System
B. Autonomic Nervous System
2) Parasympathetic System


Brings everything back to homeostasis
see page 398 for a comparison of the
sympathetic and parasympathetic systems
http://www.drstandley.com/bodysystems_centralnervous.shtml
B. The Neuron
How do nerves work? - Elliot
Krane

http://www.youtube.com/watch?v=uU_4uA6zcE&list=PLJicmE8fK0Ehrg3meytY7DT8LJiw
uU3Th&index=144
B1. Neuron Structure





Dendrites: Receive info and deliver it to cell body
Cell Body (soma): contains major cell organelles
and neuroplasm. It is the bridge between the
dendrites and the axon.
Axon: conduct nerve impulses away from cell
body.
Axon terminal: synaptic knob, site of
neurotransmitter release into the synaptic cleft.
Synapse: gap between the pre-synaptic neuron
and post-synaptic neuron
B1. Neuron Structure

Axons



In the PNS, axons are coated with an insulating
material called myelin
Myelin is a fatty protein sheath composed of
Schwann cells that increases the speed of nerve
transmission by ~50X
Schwann cells also provide nourishment and
regeneration of new nerve tissue
Note: Myelinated nerves = white matter
Unmyelinated nerves = gray matter
B1. Neuron Structure

Axons



Neurolemma is produced by the Schwann cells in the
PNS and other glial cells in the CNS, it is a membrane
that promotes the regeneration of damaged axons
Spaces between the myelin sheath are called Nodes
of Ranvier
Impulses jump from node to node.


An action potential can propagate down a non-myelinated
axon at speeds as slow as 0.5 metres per second (1.8
km/h).
In contrast, the saltatory conduction that takes place in
myelinated axons allows a potential to travel at speeds of
up to 120 metres per second (over 400 km/h)! That is why
your brain can communicate with your big toe in a few
hundredths of a second
B2. Types of Neurons
a)
b)
c)
Sensory Neurons – take messages from
body parts to the CNS, transmitting
impulses from sensory receptors in the body
Interneurons (association neuron) – in
the spinal cord associated with the CNS,
connects one neuron to the next
(association neurons)
Motor Neurons – bring messages out of
the CNS to an effector (muscle, gland etc. )
What is ALS? The disease
behind the ice bucket
challenge

http://globalnews.ca/video/1512882/dr-davidtaylor
B2. Types of Neurons
•
Receptors
•
NS uses receptors to collect info about
internal/external environment






Chemoreceptors: sensitive to chemicals
Baroreceptors: sensitive to pressure
Osmoreceptors: sensitive to fluid levels
Mechanoreceptors: sensitive to vibrations
Photoreceptors: sensitive to light
Thermoreceptors: sensitive to changes in
temperature
B2. Types of Neurons
•
Receptors




Collected info is sent to the CNS by sensory
(afferent) neurons
CNS is composed of association (inter or relay)
neurons. Theses neurons interpret the
information
Response is sent back to effectors by motor
(efferent)
Effectors are muscles, glands or organs that
help the organism respond to the stimulus.
B2. Types of Neurons
Reflex Arc
PNS
CNS
Receptor  Sensory Neuron
http://www.brainviews.com/abFiles/AniPatellar.htm
Association
(Interneuron)
Neuron
Effector Motor Neuron
REFLEX LAB
Babinski
 http://www.articleoutlook.com/the-babinskitest-and-the-babinski-response/
 https://www.youtube.com/watch?v=kOq5Np0
eZ6A

B3. Impulse Transmission


All activities depend on nerve impulses
The plasma membrane of the neuron allows the
axon to conduct an impulse through charge
separation


Passive Transport
 Protein channels are needed for ions to pass across the
membrane
 There are K+ channels (leaky) and Na+ channels
Active Transport
 Important in maintaining resting membrane potential
 Ex. Sodium Potassium Pump


Embedded proteins in the neuron membrane pump out 3 Na+ for
every 2 K+ allowed in, with the use of ATP
Maintains polarization at rest
Sodium Potassium Pump

http://www.mcgrawhill.ca/school/applets/abbi
o/ch11/sodium-potassium2_sodiu.swf
B3. Impulse Transmission
http://www.getbodysmart.com/ap/nervoussystem/neurophysiology/actio
npotentials/actionpotential/tutorial.html

Membrane potential



Based on the distribution of ions across the
membrane
Usually –70 mV inside, outside is considered zero
Sodium ions naturally move into the cell while
potassium ions move out of the cell
(electrochemical gradient)
B3. Impulse Transmission

Resting Membrane potential




Inside neuron: high concentration of K+ and
negatively charged proteins
Outside neuron (ECF): high concentration of Na+,
Ca2+ and Clresting membrane potential is approx. -70 mV
at rest, the membrane is polarized due to the
higher concentration of positive charge in the ECF
and the negative charge inside the cell
membrane.
B3. Impulse Transmission

Action Potential
1) Depolarization
 Stimulation occurs and Na+ channels open
allowing Na+ to rush into the cell
 Membrane potential increases to +30 mV
B3. Impulse Transmission

Action Potential
2) Repolarization
 Na+ channels close
 K+ channels open allowing K+ out to equalize and return
the polarity back to normal
 Using ATP, Na+/K+ pumps quickly re-establish the original
resting membrane (3 Na+ for every 2 K+ allowed in)
 Results in a negative charge inside the cell and a positive
charge outside the cell
 Once an action potential occurs at one spot along an axon,
it excites and adjacent portion of the membrane into an
action potential. A wave of action potential sweeps all the
way down the neuron
B3. Impulse Transmission

Action Potential
http://media.pearsoncmg.com/bc/bc_campbell_
biology_7/media/interactivemedia/activities/lo
ad.html?48&B
More animations

http://bcs.whfreeman.com/thelifewire/content/
chp44/4402s.swf

http://www.mcgrawhill.ca/school/applets/abbi
o/ch11/voltagegated_voltage_ga.swf

http://highered.mcgrawhill.com/sites/0072495855/student_view0/cha
pter14/animation__the_nerve_impulse.html
B3. Impulse Transmission

Action Potential
3) Hyperpolarization
 The membrane briefly drops below resting
membrane potential do to the relative leakiness of
K+ channels
 This prevents another action potential and
maintains the refractory period
4) Refractory Period
 Refractory period is the recovery time required
before a neuron can produce another action
potential
 It is an resetting of ionic distribution
B3. Impulse Transmission

Action Potential
5) Threshold Level
 Threshold level is the minimum level of a stimulus
required to produce a response (approx. –55 mV)
 All or none – not graded
 Threshold value – stimulus is just strong enough
to cause voltage gated Na+ channels to open
 Subthreshold

Graded responses – summation of subthreshold
stimuli can lead to action potential
B3. Impulse Transmission

Action Potential
6) All or None Response
 The all or none response of a nerve or a muscle
fibre means that the nerve or muscle responds
completely or not at all to a stimulus
What Determines the Intensity of the
Response?


More neurons are depolarized
Impulse frequency – brain reads it as more pain
B3. Impulse Transmission

Action Potential

http://brainu.org/files/movies/action_potential
_cartoon.swf

http://media.pearsoncmg.com/bc/bc_0media_
ap/apflix/ap/ap_video_player.html?pap
C. More on The Synapse
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter14/animatio
n__transmission_across_a_synapse.html
C. The Synapse



nerve impulses travel from one neuron to another
across a small spaces that separates them called a
synapse
a synapse consists of (1) a terminal bouton, (2) a
gap between the adjoining neurons called the
synaptic cleft, (3) synaptic vesicles which
produce and store neurotransmitters, and (4) the
membrane of the dendrite or postsynaptic cell
the neuron that transmits the impulse is the
presynaptic neuron; the one that receives the
impulse is the postsynaptic neuron
C. The Synapse

Events at the presynaptic neuron




action potential reaches the axon terminal
Ca2+ causes vesicles containing
neurotransmitters to bind to the axon terminal
membrane
Neurotransmitter is released
Neurotransmitters diffuse across synapse to
post-synaptic neuron receptors on the membrane

Neurotransmitters can be excitatory (depolarization) or
inhibitory (hyperpolarization)
C. The Synapse

Events at the presynaptic neuron
C. The Synapse

Events at the postsynaptic neuron



Inhibitory or excitatory signal is received
When the neurotransmitters bind to receptors,
the permeability of the postsynaptic neuron is
affected
May cause an action potential if the threshold is
reached
C. The Synapse

Neurotransmitter Chemicals





Acetylcholine - released by nerves that stimulate muscle
contraction, typically excitatory (broken down by
cholinesterase)
(Acetyl)Cholinesterase – released from glial cells, breaks
down acetylcholine, prevents continuous stimulation.
Norepinephrine (noradrenaline) – produced by the
adrenal glands in a fight or flight response, increases blood
glucose levels
Dopamine – produces feeling of pleasure when released,
usually inhibitory
Serotonin - it acts as a neurotransmitter regulating normal
brain processes, inhibits pain pathways
C. The Synapse

Drugs



synthetic or naturally occurring chemicals
can alter mood or emotional state
bind to receptors present on post-synaptic membranes
Note:
 See the graph on page 363
 Sometimes neurons need simultaneous stimulation to
get to threshold level of the next neuron
Table 2.1 Major Neurotransmitters in the Body1,7,8
Neurotransmitter
Role in the body
Acetylcholine
A neurotransmitter used by spinal cord neurons to
control muscles and by many neurons in the brain
to regulate memory. In most instances,
acetylcholine is excitatory.
Dopamine
The neurotransmitter that produces feelings of
pleasure when released by the brain reward
system. Dopamine has multiple functions
depending on where in the brain it acts. It is
usually inhibitory.
GABA (gamma-aminobutyric acid)
The major inhibitory neurotransmitter in the brain.
Glutamate
The most common excitatory neurotransmitter in
the brain.
Glycine
A neurotransmitter used mainly by neurons in the
spinal cord. It probably always acts as an
inhibitory neurotransmitter.
Norepinephrine
Acts as a neurotransmitter and a hormone. In the
peripheral nervous system, it is part of the fightor-flight response. In the brain, it acts as a
neurotransmitter regulating normal brain
processes. Norepinephrine is usually excitatory,
but is inhibitory in a few brain areas.
Serotonin
A neurotransmitter involved in many functions
including mood, appetite, and sensory perception.
In the spinal cord, serotonin is inhibitory in pain
pathways.
http://science-education.nih.gov/supplements/nih2/addiction/default.htm
D. Central Nervous System

The brain and spinal cord
The Unfixed Brain

http://www.youtube.com/watch?v=jHxyPnUhUY&feature=youtu.be
Pinky and the Brain
 http://www.youtube.com/watch?v=h5f56Ynb0
1E&feature=youtu.be
Phineas Gage
 http://www.youtube.com/watch?v=MvpIRN9D
4D4
D1. The Brain
The Cerebrum
a)



Cerebral cortex –
outermost part of the
brain composed of
gray matter, folded to
increase surface area
Gyri (folds) and sulci
(indentations)
http://www.youtube.co
m/watch?v=MvpIRN9
D4D4
MRI
D1. The Brain
a)

The Cerebrum
Cerebral hemisphere is divided into
the right (creativity) and left
(mathematical) cerebral cortex




Frontal Lobe: controls movement
(walking and talking), sometimes linked
to intellectual activities and personality
Temporal Lobe: controls smelling and
hearing, sometimes linked memory
and interpretation of sense information
Parietal Lobe: controls touch and
temperature awareness, sometimes
linked to emotions and speech
interpretations, reading
Occipital Lobe: controls vision, and
interprets visual information
D1. The Brain
The Cerebrum
a)
Cerebral hemisphere is divided into the right (creativity)
and left (mathematical) cerebral cortex
Speech:

temporal – the Wernicke’s area picks up written and
spoken words

frontal – Broca’s area is involved in language processing,
speech production and comprehension

D1. The Brain
The Cerebellum
b)
coordination of muscle
activities (balance,
muscle tone, body
position etc)

ensures movements are
coordinated

can be programmed to
remember movements
https://www.facebook.com/Ca
lgaryHumaneSociety/post
s/582899035084614

D1. The Brain
The Brainstem
c)
•
•
•
known as the medulla oblongata
cardiac center, breathing, vasa-motor
control
reflex actions – vomiting, sneezing,
coughing, swallowing
The Pons
d)
•
the region of the brain that acts as a relay
station by sending nerve messages
between the cerebellum and the medulla
The Thalamus
e)


Located below the cerebrum
Screens sensory information so that it
can direct attention to stimuli of
importance (acts as a filter for information
brought to conscious thought)
D1. The Brain
Hypothalamus
(the brain within a brain)
f)










control of the ANS, it is the way the
internal environment works (maintains
homeostasis)
receives information from internal organs
co-ordinates nervous and endocrine
systems
connection between emotions and
physiology
feelings of rage/anger
body temperature depression control
hunger/fullness center
thirst/osmoreceptors
sex drives
sleeping/waking patterns
D1. The Brain
Pituitary Gland
g)
•
The master gland
Corpus Callosum
h)
•
Region of white matter that connects the
left and right hemispheres
Meninges
i)



act as shock absorbers
protects from chemicals entering (blood
brain barrier) and going all the way down
the spine
Dura mater, arachnoid, pia mater
Cerebrospinal Fluid
j)


shock absorber – carries red blood cells
and nutrients
produced in the ventricles of the brain
(spaces/gaps in the brain)
Girl Living With Half
Her Brain
http://www.youtube.com/watch?v
=2MKNsI5CWoU
http://www.youtube.com/watch?v
=yNWQUN4jg-s
Brain dissection
D2. The Spinal Cord
Two Main Functions
•
a)
b)
communication between peripheral nervous system and the brain
simple reflex actions
reflex arc (see page 354)

stimulus

sensory receptor

sensory neuron

interneuron

motor neuron

effector (muscle/gland)
D3. Cranial Nerves
Do not pass through the spinal cord
•
a)
Vagus nerve

from the brainstem, down neck, and through the whole body – bladder, kidney,
digestive system
E. Autonomic Nervous System






nerves designed to maintain
homeostasis which are not under
conscious control
sympathetic nervous system
prepares the body for stress
parasympathetic nervous system
returns body to normal resting
levels
see table 15.1 on page 366 and the
diagram on page 367
ganglion (ganglia) - cluster of
neuron cell bodies, many
connections to be made and many
synapses occur
sympathetic nervous system has
ganglia