Transcript Nervous System

Neurons- The matter of the
nervous system
Chapter 7: Pgs 120-133
The Nervous system controls the
entire body
• It is the interface
between stimulus and
response
• Allows animals to interact
with their environment
• Brain and spinal cord:
central nervous system
(CNS)
• Other nerves: peripheral
nervous system (PNS)
The nervous system is the interface
between stimulus and response
Neurons come in 3 basic types:
Sensory neuron, Interneuron, Motor
The Neuron is the base unit of the
nervous system
Neurons are large cells supported by a
variety of glial cells
• Human neurons can be
1m in length
• Potentially thousands of
glial cells support a
single neuron
• Provide nutrition,
support, insulation
• Schwann cells are an
example
The synapse is the connection point
between neurons
Many synapses make complex
information processing possible
• Cell interactions form
logic circuits
• AND, NOT, etc. gates are
formable
• Human Brain: 100
billion neurons
• Up to 10,000 synaptic
connections/neuron
The nervous system runs on electricity
• Current- The movement of charge (electrons
or ions)
• Voltage- potential energy stored in a charge
disparity over distance
• Nervous system uses ions (Na+, K+, Cl-, Ca++)
to send signals from one neuron to another
Ion channels in synapses generate
electric current
At rest, neurons are low in sodium,
high in potassium
Neurotransmitters are the chemical
signals with which neurons
communicate across a synapse
• Neurotransmitters bind
to gated ion channels in
the cell membrane of
the next neuron
• Binding opens the ion
channel
• Hydrolysis or reuptake
removes the
neurotransmitter
Many Drugs copy the action of
neurotransmitters
• Methamphetamine is
structurally similar to
dopamine
• Dopamine involved in
learning and reward
systems
Dopamine
Methamphetamine
Some important neurotransmitters
• AcetylcholineNeuromuscular
• Dopamine-Exitatory
• Norepinephrine
• GABA- Inhibitory
• Serotonin-Regulatory
Which one of the following statements is false?
A) Sensory neurons convey signals from the CNS to
sensory receptors.
B) Motor neurons convey signals from the CNS to
effector cells.
C) Interneurons integrate data and relay
appropriate signals to other interneurons or to
motor neurons.
D) The PNS includes nerves and ganglia.
E) The CNS consists of the brain and spinal cord.
• What is the functional unit of the nervous
system?
• A) dendrite
• B) cell body
• C) neuron
• D) axon
• E) synapse
Neurons have a resting membrane
potential
• Negatively charged
• Keeps the neuron
poised for instant action
• -70mV
• Maintained by constant
active transport of ions
•
When depolarized, neurons respond in
milliseconds
• Depolarization is the
activation event
• Depolarization is
caused by opening of
gated sodium
channels
Nerve impulse Synopsis:
1. Neuron at rest, -70mV
2. Opening of gated sodium channels
depolarizes the cell
• Action potentials normally travel along an
axon
• A) toward the cell body.
• B) away from the cell body.
• C) in either direction, depending on the needs
of the animal.
• D) away from the synapse.
• E) from axons into dendrites.
4-5. Potassium (K+) channels
hyperpolarize the cell behind the
action potential
3.5: The impulse is propagated down
the axon
• In between the
Schwann cell ,myelin,
Na+ channels open
• The action potential
moves cown the cell
rapidly
6. Depolarization at the axon terminal
causes vesicle fusion with membrane
• Vesicles contain
neurotransmitter
• Neurotransmitter is
released into the
synapse, stimulating the
receiving neuron
• Stiumuls is terminated
by ruptake or
destruction of the
neurotransmitter
0.5: Vesicles were marched down the
axon previously by kinesin
Antidepressants can block reuptake of
neurotransmitters
• SSRI- “Selective
Serotonin Reuptake
Inhibitors”
• Prozac, Paxil, Zoloft,
etc.- all SSRI’s
Sarin nerve gas is an
Acetylcholinesterase Inhibitor
• How does it work?
• How does it kill people?
The reflex arc is the most basic neural
circuit
The Ganglion splits the signal to notify
the brain
What causes the signal that crosses a synapse to
stop?
A) A second action potential traveling down the
signaling cell sounds a sort of "retreat," and the
ions reverse direction.
B) The responding cell runs out of sodium and is no
longer able to respond to the stimulus.
C) The responding cell runs out of potassium and is
no longer able to respond to the stimulus.
D) The chemically gated ion channels of the
receiving cell's membrane can only transport for
a short period of time before they close.
E) The neurotransmitter is broken down or
transported back to the signaling cell.
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Once the threshold potential is reached
A) the membrane potential is positive.
B) K+ channels open.
C) Na+ channels close.
D) an action potential is inevitable.
E) None of the choices are correct.
The human brain has 3 major regions
Higher thought is compartmentalized
to the cerebrum
Regions of the cerebral cortex are
themselves compartmentalized
A homonculus shows the area of the
brain devoted to regions of the body
• Which of the following statements about the
sodium-potassium pump is false?
• A) It is a membrane protein.
• B) It keeps the concentration of sodium low
inside the cell.
• C) It moves sodium across the membrane and
into the cell.
• D) It helps maintain the resting membrane
potential.
• E) It actively transports potassium into the cell
• Which of the following neurotransmitters is
associated neuromuscular junctions?
• A) acetylcholine
• B) GABA
• C) epinephrine
• D) serotonin
• E) endorphins