Transcript Motor neuron

Biological bases of
cognition and behavior
Part 1
How your “wetware”
works...
Biological (Physiological) Psychology
(Neuroscience)
Neuron
a nerve cell
the basic building block of the nervous system
Communication Highway!!!
How we work...
Neurons
 Neurons do the “talking”
The human brain has about 100 billion
neurons, interconnected at 100 trillion
synapses.
Here’s what a trillion pennies looks like:
How it works...
Neurons come in 3 basic flavors…
Sensory neurons (“afferent” neurons) senses
to brain for processing
Motor neurons (“efferent” neurons) brain to
muscles/glands for reaction
Interneurons connectors; only in brain and
spinal cord
Example: Water temp in shower
The Neuron
Neural communication down the axon
Dendrite
the bushy, branching extensions of a neuron that
receive messages and conduct impulses toward the
cell body
Axon
the extension of a neuron, ending in branching
terminal fibers, through which messages are sent to
other neurons or to muscles or glands
Neural communication down the axon
Myelin [MY-uh-lin] Sheath
a layer of segmented fatty cells encasing the fibers of
many neurons
greater transmission speed of neutral impulses (Duct
Tape)
Made from glial cells
At rest, the neuron is polarized (at “resting
potential”)
Sodium (Na+) and chloride (CL-) outside and
potassium (K+) inside
“Sodium pump” – Ion pump, resets to resting
potential
When does a Neuron “Talk”
Dendrite acts as a NET and grabs the
chemical messages, sending info to the
cell body/nucleus
Nucleus or the “Office Executive” assesses
and decides whether to command
Neural communication:
down the axon
Action Potential
a neural impulse; a brief electrical charge
that travels down an axon
positively charged ions in and out of channels
in the axon’s semi-permeable membrane
Threshold
the level of stimulation required to trigger a
neural impulse
The “All or None” law; coded by firing rate
Neural communication:
down the axon
Cell body end
of axon
Direction of neural impulse: toward axon terminals
Rapid influx of positive charge triggering electrical message:
“RELEASE THE MESSAGE!!”
Neural communication:
down the axon
Graded Potentials
Small changes that make a neuron more or
less likely to fire (i.e., change the threshold)
Depolarization = more sensitive
Hyperpolarization = less sensitive
Nucleus
Message comes in as either a excitatory
(Fire) or inhibitory (Don’t Fire)
neurotransmitters (chemicals)
Neural Communication at the synapse
Synapse [SIN-aps]
Junction/gap between the axon end bulb and the
dendrite “net”
tiny gap at this junction is called the synaptic gap or
cleft
Neurotransmitters
chemical messengers that traverse the synaptic gaps
between neurons (leave the axon)
when released, neurotransmitters travel across the
synapse and bind to receptor sites on the receiving
neuron (dendrite part)
This produces a graded potential in the receiving
neuron!
Neural Communication:
at the synapse
Neurotransmitters
Excitatory neurotransmitters: FIRE!!!!!
Inhibitory neurotransmitters: Don’t FIRE!!!
Modulatory neurotransmitters
(“neuromodulators”)
A shopping list of
neurotransmitters...
Acetylcholine
Learning & memory, but also triggers
muscle contraction (botulism = Ach receptor
blocker)
Dopamine
Influences movement, learning, and
attention.
 May be linked to schizophrenia &
Parkinson’s disease
A shopping list of
neurotransmitters...
Serotonin
Affects mood, hunger, sleep, and
arousal.
Prozac/Zoloft raises serotonin levels.
Norepinephrine and epinephrine
Affects alertness and arousal; also
anxiety
A shopping list of
neurotransmitters...
Gamma-aminobutyric acid (GABA)
Inhibitory neurotransmitter.
May be involved in eating and sleep
disorders.
Note that the effects of neurotransmitters
depend on the receptor
A given neurotransmitter can trigger different
types of receptors with different results!
Neural
Communication
Dopamine pathways
Neural
Communication
Serotonin pathways
Fun with
neuromodulators...
Endorphines
“morphine within”
natural, opiate-like neurotransmitters
 linked to pain control and to pleasure
Drugs and Neural
Communication
Neurotransmitter
molecule
Receptor site on
receiving neuron
Receiving cell
membrane
Just write down what
agonist and antagonists do
Agonist mimics
neurotransmitter
Antagonist
blocks
neurotransmitter
The Nervous System configured
Nervous
system
Central
(brain and
spinal cord)
Peripheral
Autonomic (controls
self-regulated action of
internal organs and glands)
Skeletal (controls
voluntary movements of
skeletal muscles)
Sympathetic
(arousing)
Parasympathetic
(calming)
The Nervous System
The body’s speedy, electrochemical
communication system
consists of all the nerve cells of the peripheral
and central nervous systems
Central Nervous System (CNS)
the brain and spinal cord
Peripheral Nervous System (PNS)
the sensory and motor neurons that connect
the central nervous system (CNS) to the rest
of the body
The Peripheral Nervous
System – part A
Autonomic Nervous System
controls the glands and the muscles of the
internal organs (such as the heart)
Sympathetic Nervous System
arouses the body, mobilizing it in stressful
situations
Parasympathetic Nervous System
calms the body, conserving its energy
The Peripheral Nervous
System – part B
The skeletal nervous system
Lots of efferent neurons (Motor)
But also afferent (sensory) for the kinesthetic
sense
http://findarticles.com/p/articles/mi_g2699/is_0001/ai_2699000193/
The peripheral nervous
system
The peripheral nervous
system
An example of neural
communication:
Reflex: a simple, automatic, inborn response to a
sensory stimulus
Brain
Sensory neuron
(incoming information)
Muscle
Skin
receptors
Motor neuron
(outgoing
information)
Interneuron
Spinal cord
How your brain is
“wired”
Neurons in the brain
connect with one
another to form networks
Inputs
The brain learns by modifying
certain connections in
response to feedback
Neural Networks
interconnected neural
cells
with experience,
networks can learn, as
feedback strengthens
Outputs
or inhibits connections
that produce certain
results
computer simulations
of neural networks
show analogous
learning