Transcript PP for Neurons

Neural and Hormonal Systems
Will Explain Why We FEEL……
Nervous
Strong
Pain
Sick
It all Starts with the Neuron
Neuron Structure
Neurons do NOT touch each otherthe space in between is call the
Synapse
axon of presynaptic
neuron
dendrite of
postsynaptic
neuron
bipolar.about.com/library
How a Neuron Fires
It is an electrochemical
process
• Electrical inside the neuron
• Chemical outside the neuron
(in the synapse in the form of
a neurotransmitter).
• The firing is call Action
Potential.
The All-or None Response
• The idea that
either the
neuron fires or
it does not- no
part way firing.
• Like a gun
Take a look -
Steps of Action Potential
• Dendrites receive neurotransmitter from another
neuron across the synapse.
• Reached its threshold- then fires based on the
all-or-none response.
• Opens up a portal in axon, and lets in positive ions
(Sodium) which mix with negative ions (Potassium)
that is already inside the axon (thus Neurons at
rest have a slightly negative charge).
• The mixing of + and – ions causes an electrical
charge that opens up the next portal (letting in
more K) while closing the original portal.
• Process continues down axon to the axon
terminal.
• Terminal buttons turns electrical charge into
chemical (neurotransmitter) and shoots message
to next neuron across the synapse.
Action Potential
Take a
look -
How Neurons Communicate
The Membrane
• The membrane surrounds the neuron.
• It is composed of lipid and protein.
The Resting Potential
• There is an electrical charge across the membrane.
• This is the membrane potential.
• The resting potential (when the cell is not firing) is a
70mV difference between the inside and the outside.
+
-
+
-
+
-
-
+
+
-
Resting potential of neuron = -70mV
outside
inside
Neurotransmitters
• Chemical messengers released
by terminal buttons through
the synapse.
• We should know at least 4
types and what they do.
Take a look -
Ion concentrations
Outside of Cell
K+
Na+
Cl-
Cell Membrane in resting state
K+
Na+
Cl-
Inside of Cell
A-
The Cell Membrane is Semi-Permeable
K+
Na+
Cl-
Outside of Cell
Cell Membrane at rest
K+
Na+
ACl-
Inside of Cell
Potassium (K+)
can pass through
to equalize its
concentration
Sodium and
Chlorine cannot
pass through
Result - inside is
negative relative
to outside
- 70 mv
Resting Potential
• At rest the inside of the cell is at -70 microvolts
• With inputs to dendrites inside becomes more
positive
• if resting potential rises above threshold an action
Depolarization ahead of AP
• AP opens cell membrane to allow sodium (NA+) in
• inside of cell rapidly becomes more positive than
outside
• this depolarization travels down the axon as leading
edge of the AP
Repolarization follows
• After depolarization potassium (K+) moves out
restoring the inside to a negative voltage
• This is called repolarization
• The rapid depolarization and repolarization produce
a pattern called a spike discharge
Finally, Hyperpolarization
• Repolarization leads to a voltage below the resting
potential, called hyperpolarization
• Now neuron cannot produce a new action potential
• This is the refractory period
Acetylcholine
• Its 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
• Its function is motor
movement and alertness.
Lack of dopamine
is associated
with Parkinson’s
disease.
Overabundance
is associated
with
schizophrenia.
Serotonin
• Function deals with mood
control.
Lack of serotonin
has been linked
to depression.
Take a look -
Endorphins
• Function deals with pain
control.
We become addicted
to endorphin causing
feelings.
Agonists and Antagonists
Drug Effects
How about a mouse party?
Types of Neurons
Sensory Neurons
Motor Neurons
Inter Neurons
Neurons and Synapses
Types of Neurons
Sensory
Motor
Interneurons
Sensory Neurons
(Afferent Neurons)
• Take information from the
senses to the brain.
Sensory Neurons
• INPUT From sensory organs to the
brain and spinal cord.
Drawing shows a
somatosensory
neuron
Vision, hearing,
taste and smell
nerves are cranial,
not spinal
Sensory
Neuron
Brain
Spinal
Cord
Motor Neurons
• OUTPUT From the brain and spinal
cord To the muscles and glands.
Sensory
Neuron
Brain
Spinal
Cord
Motor
Neuron
Motor Neurons
(Efferent Neurons)
• Take information from brain
to the rest of the body.
Interneurons
• Interneurons
carry
information
between other
neurons only
found in the
brain and spinal
cord.
Sensory
Neuron
Brain
Spinal
Cord
Motor
Neuron
Inter Neurons
• Take messages
from Sensory
Neurons to
other parts of
the brain or to
Motor
Neurons.
Divisions of the Nervous
System
Take a look -
Sympathetic Nervous System
Flight or Fight Response
A Simple Reflex
A Simplified Neural Network
Neurons that learn to work
together as a team.
The Endocrine System
A system of glands that secrete
hormones.
Similar to nervous system,
except hormones work a lot
slower than neurotransmitters.
Hormones
Neurotransmitters
The Major Endocrine Glands