Transcript Document 7895078

Neurons
I bet your neurons are all fired
up now!
The Nervous System
NEURON
= 1 cell

Nerve =
a bundle of neurons
Types of Neurons
• Efferent (Motor) Neurons
carry outgoing messages from the brain
and spinal cord to the muscles and glands
• Interneurons -
neurons within the
brain and spinal cord that communicate
internally and between sensory inputs
and motor outputs
• Afferent (Sensory) Neurons carry messages from tissues and sensory
organs to the brain and spinal cord for
processing
Neurons
Neurons
How neurons communicate
Neurons use an electro-chemical process to
send messages
• Why electrical?
– Pushing information through axon is based on
process of positive and negative charges of
electrical atoms (ions)
• Potassium (K+), Sodium (Na+), Chloride (Cl-)
• Why chemical?
– Neurotransmitters cross synapse: different ones
send different impulses and need to find receptors
– It can either excite (fire) or inhibit (prevent
firing)
•
Messages are sent at a speed of 2-200 mph
• Neurons are altered with use (learning) – unused
neurons die (“neural sculpting)
How does a neuron fire
The electrical impulse is called the action potential
Step 1 - Resting potential
Polarized – positive outside, negative inside
–
(Na+)
(Cl- & K+)
Selectively permeable – gates do not allow
sodium ions to pass through the cell membrane
–
Step 2 - Action potential – brief electrical charge
that travels don the neuron
– Transmits neural messages to other neurons, muscles
or glands
–
When stimulated – depolarizes
•
Sodium (Na+) rushes in
Step 3 - Repolarization
–
Potassium (Ka+) flows out repolarizing the Axon.
Step 4 - Return to Resting Potential
•
Sodium/Potassium pumps push Sodium (Na+) out and
Potassium in (Ka+) bringing axon back to a resting state
Step 5 - Refactory period
–
Brief period of time when neuron won’t fire no
matter how much stimulation
Action Potential
Electrical Transmission –
The Action Potential
http://outreach.m
cb.harvard.edu/
animations/actio
npotential.swf
How to generate a neural impulse
1. Neuron is stimulated by light, heat,
pressure or chemical messages
(neurotransmitters) from other neurons.
2. Signals from other neurons are either
–
–
excitatory inhibitory -
–
(excitatory) – (inhibitory) reach minimum threshold -
3. All or None Law –
How do neurons communicate with
each other?
The chemical process
How Neurons Communicate
Synaptic Transmission
http://learn.genetics.utah.e
du/content/addiction/rewar
d/neurontalk.html
Neurotransmitters
Neurotransmitters –
Excitatory neurotransmitters
Inhibitory neurotransmitters
Acetylcholine (ACH)
• Deals with motor movement,
memory and learning.
• Too much and you will _________
• Too little and you will __________
• Lack of AcH has been linked to
______________________
• Black widow –
• Botox –
• Curare –
Dopamine
• Deals with motor
movement and
alertness/attention,
emotion, rewards.
• Lack of dopamine –
linked to
_______________
• Too much - linked to
_______________
• Too little –
_______________
Serotonin
• Involved in mood
control, hunger,
sleep and arousal.
• Lack of serotonin
has been linked to
_________________
• Anorexia = _______
• Bulimia = ________
Norepenephrine
•
• Helps control
• Undersupply can
depress mood
GABA
• Major
• Hunger and Sleep
• Undersupply linked
to
______________
• _______________
causes an increase in
Gaba
Endorphins
• Involved in pain
control.
• “endorphins make
you happy” – runners
high (emotions)
• Drugs that mimic -
Glutamate
• Major __________
meaning _________
• Involved in memory
and learning
• Oversupply can over
stimulate brain,
producing migraines
or seizures
•
Drugs can be…..
• Agonists• Antagonists• Reuptake Inhibitors-
Agonists and Antagonists
http://thebrain.mcgill.ca/flash/i/i_03/i_03_m/
i_03_m_par/i_03_m_par_cocaine.html#dro
gues
Agonist and Antagonists
Examples:
Agonists – Opiate Drugs Heroine,
Morphine (Endorphins)
Black Widow Spider Venom (AcH)
Prozac (serotonin)
Antagonists – Botulin (AcH), Botox
(AcH), Curare (AcH)
The Nervous System
Central Nervous System
• The Brain
and spinal
cord
• CNS
Peripheral Nervous System
• All nerves that are
not encased in bone.
• Everything but the
brain and spinal
cord.
• Divided into two
categories….somatic
and autonomic.
Somatic Nervous System
• Controls
• Uses
Autonomic Nervous System
• Controls
• Divided into two
categories
Sympathetic Nervous System
• Fight or Flight
Response.
Parasympathetic Nervous System
• Automatically
Reflexes
• Reflex - a simple, automatic,
inborn response to a sensory
stimulus
– ______________take info up
through spine to the brain.
– Some reactions occur when
– Survival adaptation.
A Simple Reflex
A Simplified Neural Network
Neurons that learn to work together as a team.
The Endocrine System
A system of
Similar to ___________________________
Work
Hormones
Neurotransmitters
The Major Endocrine Glands