General Outcome: Explain how the Nervous System controls
physiological processes
Slide 3
The Nervous System A system of the body that coordinates &
regulates the activities of the body
Slide 4
Control System Maintains homeostasis homeo/stasis
(same/changing) changes in order to keep a balance
Slide 5
5 major components Stimulus receptor modulator/regulator
effector Action Sensory Pathway Motor Pathway -highly specific
-receive stimuli -Selects appropriate Response (spinal cord or
brain) -carries out the response (muscle or gland)
Slide 6
The Nervous System & Homeostasis Organization of the
Nervous System Structure of a neuron Action Potential Synaptic
Transmission Structure of the Brain Senses: The Eye & Ear
Slide 7
Nervous System Organizational Tree! Peripheral Nervous System
(PNS) Feeds into & out of CNS Central Nervous System (CNS)
Decision maker Nervous System Somatic Pathway (Voluntary) under
conscious control Examples? Autonomic Pathway (Involuntary)
unconscious control Examples? Parasympathetic (Restores to normal)
Restores balance! Restores Homeostasis! Sympathetic (Stimulatory)
Speeds you up! Excites you! Brain & Spinal CordMotor
PathwaySensory Pathway NS Overview
Anatomy of a Nerve Cell Two different types of cells are found
in the nervous system: Glial Cells: non-conducting; important for
support and metabolism of nerve cells Neurons: functional units of
the nervous system (conduct nerve impulses)
Slide 11
The Neuron: Wires within a nerve! See diagram on p.410 of
text
Slide 12
Types of Neurons see your handout! Motor Neuron Connects the
central nervous system to a muscle or a gland (also called efferent
neurons) Sensory Neuron Connects a sensory receptor to the central
nervous system (also called afferent neurons) Interneuron (or
Association Neuron) Connect sensory neurons to motor neurons
Connects two or more neurons Found in CNS
Slide 13
The Neuron Dendrite receives information from receptors or
other neurons and conducts nerve impulses toward the cell body.
Cell Body contains nucleus and organelles Axon conducts nerve
impulses away from the cell body Myelin a fatty protein that covers
the axon Insulate the axon allowing nerve impulses to travel faster
(Myelination is only found outside the brain and spinal cord) Nodes
of Ranvier gaps within the myelin sheath Impulses jump from
node-to-node therefore speeding up the impulses Neurillemma
delicate membrane that promotes regeneration of damaged neurons
Only found in myelinated neurons Schwann Cells special type of cell
that produces the myelin sheath
http://www.youtube.com/watch?v=36DSFSyxHw0
Slide 14
To Do: Read p. 408-411 from text and Complete 66 word summary
Complete Sections A thru C in your Notes Package Color and Label
Neuron Diagram
Slide 15
Structure of a Neuron From Nelson Biology
Slide 16
The Job of Schwaan cells = Wrap Axons ! Schwaan cells: Schwaan
cells: Nourish the axon Provide insulation (myelin) Repair axon
damage (neurilemma) Found mainly in PNS Neurilemma = concentric
rings around axon created by the Schwaan cell makes the impulse
fast (insulated)
Slide 17
Job of Myelin! Provide insulation like the covering on speaker
wire Prevent loss of signal down axon! Damaged myelin results in a
loss of signal down the axon! (Results in ) Multiple Sclerosis
(MS)
Slide 18
Above is a map giving the geographical prevalence of Multiple
Sclerosis (MS) world-wide. It has long been established that MS is
more likely to occur in communities in the further Northern and
Southern Lattitudes, possibly due to less sunlight, environmental
factors or dietary reasons.sunlightenvironmental factorsdietary
http://www.msrc.co.uk/index.cfm?fuseaction=show&pageid=2325
Slide 19
A beauty of a neuron!
Slide 20
Slide 21
Slide 22
Slide 23
Types of Neurons Sensory Neurons (Afferent Neurons) conducts
nerve impulse from sense organs to the brain and spinal cord (CNS)
Motor Neuron (Efferent Neurons) conducts nerve impulses from CNS to
muscle fiber or glands (effectors) Interneuron (Association Neuron)
found within the CNS No myelination Intergrates and interprets
sensory information and relays information to outgoing neurons
Slide 24
To Do: Textbook Questions pg. 410 #1-4 Work on STS Assignment
Remember: Purchase Key Booklet by next Friday Parent letter if I
dont already have it
Slide 25
Daily Review
Slide 26
Returning involuntary body functions to normal after a period
of stress is the function of which division of the nervous system?
A.Central B.Somatic C.Sympathetic D.Parasympathetic
Slide 27
Syphilis is a STI that affects the central nervous system. The
neurons damaged by syphilis are A.interneurons B.sensory neurons
C.somatic motor neurons D.autonomic motor neuron
Slide 28
Common Reflexes Babinski reflex: a tickle of a babies foot
causes the toes to curl Pupillary reflex: iris diameter changes in
response to light conditions Cross extensor reflex: in a standing
position, fatigue of one leg causes withdrawal of weight onto the
other leg Stretch reflex: -the body senses the muscles shortening
so the tendency is to stretch them out in order to perform motor
functions properly Knee jerk reflex (patellar): a tap on the
patellar tendon causes top leg muscles to contract & lower leg
muscles to relax simultaneously Withdrawal reflex: defensive
strategy in response to a painful stimuli like heat & cold or a
cut or pinch of some kind Others include: Vomiting, coughing,
defecation, & milk release some of which are voluntary
reflexes.
Slide 29
Reflexes: are well established neural circuits that are pre-
programmed to allow motor responses to certain stimuli some may be
instinctual as in newborns some are learned as in repeated motor
tasks involved in sport some are defensive to enhance survival and
other reflexes help your eye to move as you read this page. Dont
need to write yet
Slide 30
Reflex Arc A reflex that does not require the brain Reflexes
may be innate or acquired
Slide 31
Reflex Arc Reflexes are autonomic responses to certain stimuli
Involuntary/automatic They pathway that a nerve impulse takes is
called a reflex arc
Slide 32
Anatomy of a Reflex Arc
Slide 33
How the Reflex Arc Functions: 1) Sensory organs (receptors)
detect dangerous stimuli! 2) Impulse is passed from the sensory
organ to a sensory neuron! 3) Sensory Neuron transfers the impulse
to the Association neuron in the spinal cord!
Slide 34
4) The INTERNEURON links the SENSORY to the MOTOR neuron! 5)
The MOTOR neuron takes the impulse to the EFFECTOR! 6) The effector
(usually a muscle) reacts. 7) Simultaneously, interneurons send the
signal up to the BRAIN for interpretation! How the Reflex Arc
Functions
Slide 35
Reflex Arc Video
Slide 36
Learner Outcome: Describe the composition and function of
reflex arcs Design and perform an experiment to investigate the
physiology of reflex arcs
Slide 37
To Do: Reflex Lab Section E in your notes package P. 414
Questions # 2, 3, 5, 6
Slide 38
Action Potential how do nerves work??? In 1900 Bernstein
hypothesized that nerve impulses where electrochemical in nature.
Future experimentation proved this. Giant Squid Experiment: Cole
and Curtis placed two tiny electrodes one inside the large axon of
a squid and the second across from the first outside the axon.
Slide 39
Cole and Curtis measured the electrical potential across the
membrane. The resting potential was found to be about 70mV. Squid
Axon Giant Squid Experiment
Slide 40
When stimulated, the action potential jumped to about +40 mV.
The action potential only lasted for a few milliseconds before the
nerve cell returned to the resting potential. -70 +40 mV 1234 ms
threshold
Slide 41
Definitions: Action Potential: the voltage difference across a
nerve cell membrane when the nerve is excited (~40 mV) Resting
Potential: Voltage difference across a nerve membrane when it is
NOT transmitting a nerve impulse (almost always -70 mV)
Slide 42
Caused by an uneven distribution of positively charged ions
across the membrane Set up and maintained by a Sodium-Potassium
pump. 3 Na + are pumped out of the cell, 2 K + ions are pumped into
the cell. Maintaining Resting Potential sodium/potassium ion pump
sodium/potassium pump 2 http://www.youtube.com/watch?v=9euDb4TN 3b0
http://www.youtube.com/watch?v=yQ- wQsEK21E
Slide 43
These positive ions want to move with their concentration
gradient by diffusion. More sodium moves out than potassium moves
in leaving a relative negative charge inside the cell. The cell is
polarized. resting potential clip
Slide 44
A Nerve impulse is an Action Potential When a neuron receives a
stimulus it becomes more permeable to sodium than potassium When
stimulated the ion gates for sodium open up. Positive ions flood
into the cell making it positive. This rapid inflow is referred to
as depolarization. Action Potential
Slide 45
After the impulse, the Na + channels close and the K + channels
open. This is called repolarization. The flow of potassium ions out
of the cell (with their concentration gradient) restores the
resting potential. The potassium gates close relatively slowly
which makes the inside of the neuron slightly more negative then
resting potential (hyperpolarization) The Na+/K+ pump continues to
pump the sodium and potassium across the membrane against the
concentration gradient to restore the resting potential.
Slide 46
Diagram from Textbook
Slide 47
Summary of Impulse. 1. At rest Na+/K+ pump moving 2.
Stimulation sodium gates open 3. The flood of sodium into the
cytoplasm stimulates adjacent areas 4. Refractory potassium gates
open sodium gates close 5. At rest Na+/K+ pump moving ions Action
potential overview Electropotential graph
Slide 48
Movement of Action Potential Many action potentials are
generated one after another along the cell membrane, causing a wave
of depolarization (similar to falling dominos). When axons are
myelinated, nerve impulses travel by saltatory conduction Gated ion
channels are concentrated at the nodes of Ranvier Flow of ions
across cell membrane can only happen at the nodes so action
potentials jump from node to node This causes the signal to be
transmitted down an axon much faster. myelinated vs. unmyelinated
impuse
Slide 49
Refractory Period: The time it takes (~0.001 s) for a
depolarized neuron to repolarize return to resting potential During
the refractory period another impulse can NOT be sent along the
neuron.
Slide 50
Threshold The amount of stimulus required to initiate an action
potential (or, to cause depolarization to occur) Once threshold is
reached the nerve impulse is passed along Draw diagram
Slide 51
All-or-None Response A neuron will fire either 100%, or not at
all. There is no difference in strength of a nerve impulse
Slide 52
Slide 53
To Do: Read pages 415 419 in your textbook Complete Section D
in your notes package Nerve impulse coloring diagram (pg. 7 notes
package) Schwann Cell & Action Potential
http://www.mcgrawhill.ca/school/applets/abbio/ch11/actionpotential_action.swf
Slide 54
Slide 55
Synaptic Transmission Neurons are not directly connected to
each other. The electrochemical action potential cannot jump the
synaptic cleft (or synapse). Synaptic transmission is entirely
chemical in nature. Synapse movie clipmovie clip
1.http://www.youtube.com/watch?v=vGS7g
uM1Gw0http://www.youtube.com/watch?v=vGS7g uM1Gw0
Slide 56
Synapse At the end of axons, tiny synaptic vesicles contain
neurotransmitters When an impulse reaches the end of an axon, these
synaptic vesicles migrate toward the end of the axon They then
release their neurotransmitter and it diffuses across the synaptic
cleft
Slide 57
Synapse Neurotransmitters attach to specific receptor sites and
causes sodium channels to open resulting in a depolarization in the
membrane. An action potential is created and the impulse travels
down the neuron. Diffusion takes time, so the more synapses
involved, the slower the response.
Slide 58
Synapse Synaptic transmission can only occur in one direction.
Since only presynaptic neurons contain synaptic vesicles, and only
post synaptic neurons have receptor sites for them, the messages
cant be sent in the other direction This explains why impulses can
only travel from sensory neuron to interneuron to motor neuron and
never in the other direction
Slide 59
Figure 10(b), pg. 420 Synaptic vesicles in the end plate of the
presynaptic neuron release neurotransmitters into the synaptic
cleft. The neurotransmitters attach themselves to receptors on the
postsynaptic membrane, causing it to depolarize. The action
potential continues along the postsynaptic neuron.
Slide 60
Slide 61
Slide 62
Synapse action at muscular juction
Slide 63
Neurotransmitters Acetylcholine (Ach): (excitatory passes
message along) neurotransmitter produced in the pre- synaptic knob
and stored in vesicles. when an action potential reaches the pre-
synaptic knob the vesicles rupture releasing their contents
(acetylcholine) into the synaptic cleft The acetylcholine diffuses
across the synapse and binds to receptor sites on the post-
synaptic knob
Slide 64
Neurotransmitters How do we stop the message? Before another
message can cross the cleft, it must be cleaned (remove the
neurotransmitter) The enzyme acetyl cholinesterase removes
acetylcholine from the receptor sites and breaks it into acetic
acid & choline the acetic acid & choline are reabsorbed
into the presynaptic knob to be reused
Slide 65
Neurotransmitters Neurotransmitters can be: excitatory - passes
along message to the next neuron, or Inhibitory binds to the next
neuron and inhibits the message from being passed on See figure 11
p. 422 Not all neurons cause depolarization in the post synaptic
membrane. Some neurons are inhibitory.
Slide 66
Neurotransmitters Often it takes more than one neuron releasing
its neurotransmitter into the synaptic cleft to elicit a response
in the post synaptic neuron. This is referred to as SUMMATION
Slide 67
Figure 11, pg. 422 Action potentials must occur simultaneously
in A and B to reach the threshold in D.
Slide 68
Other Types of Neurotransmitters: Serotonin Dopamine
Norepinephrine GABA You will fill in some information regarding
these in your notes package but do NOT have to memorize them. If
used on a diploma you will be told what you need to know about
them
Slide 69
13.2 Summary Electrochemical Impulse Nerves conduct
electrochemical impulses from the dendrites along the axon to the
end plates of the neuron. Active transport and diffusion of sodium
and potassium ions establish a polarized membrane. An action
potential is caused by the inflow of sodium ions. Nerve cells
exhibit an all-or-none response. Neurotransmitters allow the nerve
message to move across synapses.
Slide 70
Slide 71
To Do: Reflex/Synapse Worksheet Complete section F in your
notes package Case Study Drugs and the Synapse p. 423-424 of text
For Extra Practice: Pg. 418 # 1-4 Pg. 420 # 5-7 Pg. 425 #3-7