Transcript Ions in Your Life

Ions in Your Life
An exploration into the role ions
play in your nervous system and
what can affect them.
Your Nervous System
Controls various organs of the
body directly. The brain also
receives information from
many organs of the body and
adjusts signals to these organs
to maintain proper functioning.

Central Nervous System
– Brain
– Spinal Cord

Peripheral Nervous System
– Autonomic System

Neurons
– Somatic System

Neurons
Brain
Cerebral Cortex
Movement)
(Thought, Language, Reasoning, Perception, Voluntary
Corpus Callosum (Processes information between the two sides)
Midbrain (Vision, Hearing, Eye Movement, Body Movement)
Cerebellum (Movement, Balance, Posture)
Thalamus (Sensory Processing and Movement)
Brain Stem (Breathing, Heart Rate, Blood Pressure)
Hypothalamus (Body Temperature, Emotions, Hunger, Thirst)
Limbic System (Emotions)
Hippocampus (Learning and Memory)
Spinal Cord






A cylinder of nerve tissue extending from the brain
stem
Receives sensory information and sends output
motor signals
The gray matter of the spinal cord consists mostly
of cell bodies and dendrites. The surrounding
white matter is made up of bundles of
interneuronal axons (tracts).
Some tracts are ascending (carrying messages to
the brain), others are descending (carrying
messages from the brain).
The spinal cord is also involved in reflexes that do
not immediately involve the brain.
Nerve cell collections extending from the base of
the brain to just below the last rib vertebrae.
Neurons
Three Modes of Nervous Signaling
(Bertil Hille, 2003)
Electrical to Electrical- Down axon
Electrical to Chemical
to Electrical- Across
synapse
Chemical to Multiple Electrical–
Hormones showering many cells
Electrical to Electrical



Moving ions make electrical signals in
neurons (Hodgkin & Huxley 1952)
Neurons have semi permeable membranes
(cell membranes) that allow some ions
through necessary for functions inside and
not others.
Many substances in our body which are
ionically bonded, are broken into ions by the
water found in our body. For example: NaCl
breaks into the Na+ and Cl-.
Faraday (1834) recognizes ions by current flow
between charged electrodes
battery
+
–
Cl–
Na+
Cl–
Cl–
Na+
current
+
Na+
cation
Cl–
anion
–
Na+
Salts dissociate in water to charged anions and cations. Cations have
positive charge and move to the negative electrode. Franklin (1751)
defines the direction of electric current as the direction of flow of positive
charge. Anions move the other way.
Nernst
Nernst (1888) describes equilibrium potentials
first instant
voltmeter = 0
at equilibrium
voltmeter = EK
–
+
IN
K+
Cl– –
+
K
+ Cl
–
K
Cl
+
K+ Cl–
+
K
K
Cl–
K+ K+ flow
Cl– Cl–K+
–
K+ Cl – K+
K+
+
Cl
K
Cl–
–
–
+
Cl Cl K
K+
K+
Cl–
K+
–
Cl
Cl–
OUT
Cl– Cl–
K+
–
K+
K+ Cl–
K+ Cl K+
Cl–K+
–
K+ flow+
K+ Cl
+
K
+
–
– Cl K+ Cl–
K
–
–
Cl Cl K+
Suppose the membrane is permeable only to K+ ions. How does
K+ move? What happens to charge? What do the other ions do?
["Permeable" means that K+ can cross the membrane by diffusion.]
Mechanisms of transport across cell membranes
Channels
Carriers
ATPase
Pumps
Ion Channel in a Neuron
Ions pass through a
gated aqueous pore,
which is narrow at
the selectivity filter.
The voltage sensors
are collections of
charged residues
that are dragged
towards the inside of
the outside as the
membrane’s charge
changes. They
regulate gating.
Flow of ions to make signals



Step 1: A few Na+ ions enter cell so cell
Na+
inside goes positive.
Step 2: A few K+ ions leave cell so cell inside
returns to rest.
Other ions that are
involved include
Cl- and Ca+
K+
Problems with this flow of ions



Limited ions in system due to high activity or low
consumption
Limited water in system to break down ionic bonds
into ions due to high activity or low consumption
Local anesthetics plug Na+ channels
– No/limited excitation, no/limited pain, no/limited
movement

If Na+ channels open too much or K+ channels
open too little…
– Too much excitation occurs leading to pain epilepsy,
arrhythmias, contractions
Electrical to ElectricalDown Axon
Electrical to Chemical to
Electrical – Across Synapse




Electrical impulse created by
flow of ions in and out cell
down the axon (Ca+) triggers
the release of synaptic vesicles
filled with neurotransmitters
into synaptic gap/cleft.
Neurotransmitters bind with
specific channels on next
neuron to start electrical
impulse (flow of ions) down
next neuron’s axon.
Many neurotransmitters each
that bind to different sites to
send different signals to
various locations to make our
body function.
Once neurotransmitters are
used they go through reuptake
channels in original neuron to
be reused.
Movie
Neurotransmitters


50 neurotransmitters have been discovered
The five most common are:
– Serotonin
(emotional stability, calming effect, sleep control,
sensory perception)
– Dopamine (pleasure, reward, euphoria)
– Acetylcholine (memory and learning, mood and arousal,
muscle contractions)
– GABA (muscle relaxant, reduces anxiety, principle inhibitor)
– Enkephalin (pain suppressant)
Problems with transfer of
neurotransmitters



Neurotransmitters get blocked from binding
with receptors to continue signal and signal
is stopped.
Other molecules with similar shapes bind to
receptors and prevent neurotransmitters
from being used. Excitation and extra
excitation occurs and neurotransmitter stops
being produced by the body itself.
Neurotransmitters are blocked from going
through reuptake transporters by original
neuron. Extra excitation occurs and body
stops producing neurotransmitter.
For Example:
One such neurotransmitter
is called "dopamine." In
the normal communication
process, dopamine is
released by a neuron into
the synapse (the small gap
between neurons). The
dopamine then binds with
specialized proteins called
"dopamine receptors" on
the neighboring neuron
thereby sending a signal to
that neuron.
After the signal is sent to the neighboring
neuron, dopamine is transported back to the
neuron from which it was released by another
specialized protein, the "dopamine transporter“.
Drugs of abuse are able to interfere
with this normal communication
process in the brain. Cocaine, for
example, blocks the removal of
dopamine from the synapse by binding
to the dopamine transporters. As
shown in this picture, this results in a
buildup of dopamine in the synapse. In
turn, this causes a continuous
stimulation of receiving neurons,
probably responsible for the euphoria
reported by cocaine abusers.
Movie
The Nervous
System gets
remodeled!!!
Things that cause these
problems







Chemical Imbalances
Alcohol
Marijuana
Cocaine
Opiates
Nicotine
Amphetamines
Acknowledgements:


Professor Physiology and Biophysics
Bertil Hille of the University of
Washington School of Medicine.
Professor W. N. Zagotta of the
University of Washington