Download Action Potentials

Week #3 (1/21 – 1/24)
Warm Up – Tues, 1/21:
- Review of Intro to NS
Anatomy Fun Fact:
Neurons, which are the
largest cells in the
human body, do not
undergo the process of
mitosis.
- Why is this important to
know?
Agenda:
1. Begin Action Potential notes
Pick up:
Action Potential
notes
Syn. Pot. & NT
Review wkst
Have out:
???
Homework:
1.
Reflex Lab
Abstract (5I) –
Fri, 1/24
2. Syn. Pot. & NT
Review wkst – Fri,
1/24
3. Action Potential
Quiz – Fri, 1/24
Warm-up: Intro to NS
Review
• What organs are
included in the CNS?
• What are the 3 main
parts of a neuron?
• What is the function of
the dendrites? Cell
body? Axon?
• What does SNS stand for
& what kind of tissue
does it control?
• Are reflexes controlled
by the SNS
monosynaptic or
polysynaptic?
• Let’s play a game of “Telephone”! I’ll start by giving a message
to….
• In a Reflex Arc, what role are you & I playing (hint: it’s a cell)?
▫ Neurons
• In anatomy, what is the space between each communicator
called?
▫ Synaptic cleft or synapse
• Was the message sent successfully?
▫ If not, why not?
How many parts were there to communicating the message?
1st: the person had to receive it (listening) – role of the dendrites of a neuron
2nd: the listener had to process the information (understanding the context of the
words) –
role of the
soma/cell body
3rd: the person
had to send the
message
(speaking/
sending it to the
next person) –
role of the axon
Understanding
• Information from one neuron flows to another neuron across a
synapse/synaptic cleft…
▫ a small gap separating
neurons that consists of:
 a presynaptic ending
(axon terminals) that
contains neurotransmitters
(NTs), mitochondria &
other organelles,
 a postsynaptic ending
(dendrites) that contains
receptor sites for NTs &
 a synaptic cleft or space
between the presynaptic
& postsynaptic endings.
BIOLOGY REVIEW:
What is the process of Diffusion?
• When it comes to understanding
how neurons communicate
(Action Potential or Nerve
Impulse), you must understand
how the process of diffusion
works!
▫ Diffusion Animation
▫ Particles move down their
concentration gradients (from
high to low)
• Is it an active or passive form of
transporting dissolves nutrients?
▫ Passive – NO ATP REQUIRED!
• Also known as “Nerve Impulses”
• Self-regenerating wave of
electrochemical activity that allows
neurons to carry a signal over a
distance (“game of telephone”)
• Pulse-like waves of voltage that
travel along several types of cell
membranes
• Analogy – assume students are POSITIVELYCHARGED Na & K IONS!
• Initiation/Resting Stage:
▫ Outside the classrooms (neuron) vs. inside classrooms (neuron)
▫ At 7:20 a.m., more students are arriving to school than are sitting
in a “0” hr class
▫ So the inside of the classrooms (neurons) have a “negative”
polarity.
• Initiation/Resting Stage:
▫ Some K+ channels are open: K+ diffusion occurring (out)
▫ Initiated by stimulus above a certain intensity or threshold
(~-70mV – resting potential)
▫ Could be a pin prick, light, heat, sound or an electrical disturbance
in another part of the neuron (“telephone call”)
▫ Electrical signal rises from changes in permeability of the
neuron’s axon membranes to
specific ions (Na+ & K+)
• Analogy – assume students are POSITIVELYCHARGED Na & K IONS!
 Depolarization (Rising Phase):
▫ Outside the classrooms vs. inside classrooms
▫ First bell rings & students move from the
halls into the classrooms
▫ This gives the inside of the classroom
(neuron) a more “positive” polarity.
 Depolarization (Rising Phase)
 K+ Channel gates are closed
 Stimulus causes gate in the Na+ Channel to open
 High concentration of Na+ outside, Na+ diffuses into neuron
 Electrical potential changes to ~ +40 mV
• Analogy – assume students are POSITIVELY-CHARGED
Na & K IONS!
 Repolarization (Falling Phase):
▫ Outside the classrooms vs. inside classrooms
▫ Dismissal bell rings & students leave the
classroom & enter the halls
▫ This gives the inside of the classroom
(neuron) a “negative” polarity again.
 Repolarization (Falling Phase)
 Depolarization causes K+ Channel gates to immediately open &
Na+ Channels close
 K+ diffuses out of neuron
 Reestablishment of initial electrical potential
of ~-60 mV
 Refractory Period (Recovery Phase)
 Na+ & K+ Channels cannot be opened by a
stimulus
 Na+/K+ Pump actively (ATP required) pumps
Na+ out of & K+ into neuron (against/up their
concentration gradients)
 Reestablishment of ion distribution of
resting neuron
 This AP acts as stimulus to neighboring proteins
within neuron membrane & initiates AP in
another part of neuron
 Wave of APs travel from dendrites to axon
terminals
 At axon terminal, electrical impulse is converted
to a chemical signal (neurotransmitter)
Week #3 (1/21 – 1/24)
Warm Up – Wed, 1/22 & Thurs, 1/23:
- Analyzing the Change in Impulse
Anatomy Fun Fact:
The sciatic nerve is the largest
in the human body, about as
thick as a pencil (~0.78 in). It
is composed of nerve fibers
(collection of neurons) that run
from the spinal cord to & down
the back of each leg.
Agenda:
1. Getting the Message across the Synapse
2. Neuron/Action Potential Model-building
OR Pushing the Limits: Brain Power
Have out:
Reflex Lab handout
Pick up:
Analyzing the
Change in Impulse
wkst
Homework:
1.
Reflex Lab
Abstract (5I) –
Fri, 1/24
2. Syn. Pot. & NT
Review wkst – Fri,
1/24
3. Action Potential
Quiz – Fri, 1/24
Action Potential
animation
• Getting the message
across (the synapse)?
▫ At axon terminal, chemical
signal (NT) crosses synapse
between adjacent neurons
 Starts AP on this neuron
▫ This activates Ca2+ channel to open
 Ca2+ diffuses into neuron
 Causes NT vesicles to move to end & fuse with cell membrane
 Through exocytosis, NTs are released into synapse
▫ NTs diffuse across synapse & bind to NT receptors on
another neuron
 Causes Na+ channels to open & AP is initiated in next neuron
Let’s Review…
How do neurons communicate?
• Action potential animation (~3 mins)
• What is another name for the nerve impulse that travels from
the cell body down the axon to the axon terminal?
• What happens in the Rising Phase/
Depolarization?
▫ Falling Phase/Repolarization?
▫ Recovery Phase/Refractory Phase?
• Once the AP has reached the axon
terminal, what ion entering the
neuron instigates the movement of
synaptic vesicles to the cell
membrane?
• What do the vesicles release into
the synapse?
Action Potential/Neuron
Model
• You will be divided into 4 groups to create 4 different
Neuron models!
• You will be presented with various materials you may
choose to use for your model.
• Each group will develop a model of a neuron, including:
▫ Dendrites
▫ Axon
- Cell body (soma)
- Synaptic terminal (axon terminal)
• Your neuron will also demonstrate the transmission of:
▫ Action potential
- Neurotransmitters
• You will be demonstrating your model to the class on Fri, 1/24
(before Quiz on Action Potentials)!
• Return any unused materials to where you found them!
• Do NOT waste materials…all materials were bought by me!
Action Potential/Neuron Model
• Each model of a neuron has to include:
▫
▫
▫
▫
Dendrites
Cell body (soma)
Axon
Synaptic terminal (axon terminal)
• Your neuron will also demonstrate the
transmission of:
▫ Action potential
▫ Neurotransmitters
Pushing the Limits – Brain Power
• Title your paper “Pushing the Limits:
Brain Power Facts” paper & have out a
pen/pencil.
▫ Identify & explain at least 5 new
concepts/ideas/facts you learn
about the human brain/mind from
the video.
 Add these to your paper!
Week #3 (1/21 – 1/24)
Warm Up – Fri, 1/24:
- Neuron Models Demo/Syn. Pot. & NT Review
wkst
Anatomy Fun Fact:
An action potential (nerve impulse) is very
quick & has the ability of transmitting
impulses at the speed of 100 meters/second.
The speed of message transmission to the
brain can be as high as 180 mph.
Agenda:
1. Action Potential Quiz
2. Ch. 14 Tour (Brain)
Turn in:
Reflex Lab
Abstract (5I)
Have out:
Neuron models?
Syn. Pot. & NT
Review wkst
Homework:
1.
Ch. 14 Tour –
Wed, 1/29 &
Thurs, 1/30