2. Lecture 14 – Ch. 48 & 49: Nervous Systems
Overview
Neuron Structure and Function
Relationship between Stimuli  Input
Nervous System Organization
Brains
Preparation for next lecture

3. Peripheral nervous system (PNS) Central nervous system (CNS)
Nervous System Overview
Sensor
Effector
Sensory input
Motor output
Integration
Peripheral nervous system (PNS)
Central nervous system (CNS)

4. Neurons
Nucleus
Dendrites
Stimulus
Axon hillock
Cell body
Presynaptic cell
Signal direction
Axon
Synapse
Neurotransmitter
Synaptic terminals
Postsynaptic cell
Specialized “excitable” cells: receive input, integrate, send output

5. Neurons Neurons are electrical: (-) inside cell; (+) outside cell
At rest, neurons maintain an electrical difference across their membrane
charge = about -70 mV
Key
Na K
Sodium- potassium pump
Potassium channel
Sodium channel
OUTSIDE OF CELL
INSIDE OF CELL
Na+ pumped out
K+ pumped in
but K+ can
leak out
Few Na+
channels open

6. Action Potentials Neurons Transmit Signals via Action Potentials:
Action Potential (AP): The electrical signal passed along the length of a neuron
Neuron membrane polarized = charge difference
(extracellular fluid)
Na+
(axon)
action potential
(+) inside cell; (-) outside cell
During action potential, Na+ channels open, flows in
Charge difference lost = depolarized
(extracellular fluid)
Na+
(axon)
action potential K+
Triggers K+ channels to open, flows out
Repolarized

7. Membrane potential (mV)
Action Potentials
Action potential
Threshold
Resting potential
Time
Membrane potential (mV)
50
100
50 1 2 3 4 5
K+ channels closed
Repolarization:
Some Na+ channels close, K+ channels open
Depolarization:
Na+ channels
open
Undershoot: K+ channels stay open
Before K+ channels close, greater charge difference = hyperpolarized

8. Action Potentials K
Na
Action potential
Axon
Plasma membrane
Cytosol 2 1 3
Na+ and K+ channels are voltage gated – as first Na+ channels open, more triggered to open (i.e. positive feedback)
Action potentials are propagated down the length of the neuron – after the AP, neuron resets itself (Na+ out, K+ in)

9. Action Potentials Action potentials can be measured electrically:
Stimulation from a neighbor neuron excites the cell (brief increase in voltage = EPSP)
IPSP
time
(milliseconds)
potential
(millivolts)
resting
threshold
EPSP
Inhibition from another neuron causes a brief decrease in voltage (IPSP)

10. Action Potentials EPSP = excitatory post-synaptic potential
dendrite of
Post-synaptic
neuron
neurotransmitter
synaptic
vesicle
Pre-synaptic
terminal
EPSP = excitatory post-synaptic potential
(+) Neurotransmitter
IPSP = inhibitory post-synaptic potential
(-) Neurotransmitter
IPSP
time
(milliseconds)
potential
(millivolts)
EPSP
Individual EPSP & IPSP weak

11. Action Potentials

12. Action Potentials
Sum of all excitatory & inhibitory ‘blips’ = summation
action potential
potential
(millivolts)
Less (-)
time
(milliseconds)
resting
threshold
More (-)
If threshold voltage is reached, an action potential occurs

13. Stimuli  Input Information Coding in the Nervous System:
1) Determine stimulus type (e.g. light / sound / touch)
All neurons use same basic signal
Wiring pattern in brain distinguishes stimuli
2) Signal intensity of stimulus
All signals similar in size (all-or-none response)
Intensity coded by:
1) Frequency of action potentials
2) # of neurons responding

14. Stimuli  Input Information Coding in the Nervous System: fires slowly
silent 1 2
fires rapidly
fires slowly 1 2
fires moderately
silent 1 2

15. Stimuli  Input Information Coding in the Nervous System:
Integrate/coordinate signals
4) Determine Output
Neural Pathways Direct Behavior:
1) Receptor: Detects stimulus
2) Sensory neuron: Sends stimulus message
3) Interneuron(s): Integrates stimuli
4) Motor neuron: Activates effector
5) Effectors: Performs function (muscle / gland)

16. Reflexes Cell body of sensory neuron in dorsal root ganglion
Quadriceps muscle
Cell body of sensory neuron in dorsal root ganglion
Gray matter
White matter
Hamstring muscle
Spinal cord (cross section)
Sensory neuron
Motor neuron
Interneuron

17. Nervous System Organization

18. Nervous System Organization

19. Cerebellum: Coordinates movement & balance
Human Brain
The Brain:
spinal cord
meninges
skull
cerebellum
pons
medulla
Cerebellum: Coordinates movement & balance
2) Brain Stem: Automatic Behaviors
A) Medulla: Controls breathing, heart rate, blood pressure
B) Pons: Controls wake/sleep transitions; sleep stages

20. Human Brain The Brain: 2) Brain Stem: 3) Diencephalon:
pituitary
gland
pineal
midbrain
The Brain:
2) Brain Stem:
C) Midbrain: Relay / “Screening” Center
Filters sensory input from body
Visual / Auditory Reflex Centers
3) Diencephalon:
Thalamus
Input center for sensory information
Hypothalamus
Regulates homeostasis, thermostat, biological clock

21. 4) Forebrain (Cerebrum): “Seat of Consciousness”
Human Brain
The Brain:
cerebral
cortex
corpus
callosum
4) Forebrain (Cerebrum): “Seat of Consciousness”
A) Cerebral Cortex
Two hemispheres (Connection = Corpus Callosum)
Left hemisphere controls right side of body (and vise versa)

22. 4) Forebrain (Cerebrum)
Human Brain
The Brain:
Parietal
Lobe
Frontal
Lobe
Occipital
Lobe
Temporal
Lobe
4) Forebrain (Cerebrum)
A) Cerebral Cortex
Four regions:
1) Frontal: Primary motor area; complex reasoning
2) Parietal: Primary sensory area
3) Temporal: Primary auditory and olfactory areas
4) Occipital: Primary visual area

23. Human Brain Frontal Lobe Parietal Lobe Occipital Lobe Temporal Lobe
primary
sensory area
Frontal
Lobe
primary
motor area
Parietal
Lobe
premotor
area
leg
trunk
arm
sensory
association
area
higher
intellectual
functions
hand
Occipital
Lobe
face
visual
association
area
tongue
speech
motor area
primary
visual
area
primary
auditory
area
auditory association
area: language
comprehension
memory
Temporal
Lobe

24. Motor and Sensory areas
Human Brain
Motor and Sensory areas

25. Human Brain Seeing Words max Reading Words Generating Verbs
Cortical Regions Involved in Different Tasks:
Seeing Words
max
Reading Words
Generating Verbs
Hearing Words

26. Human Brain The Brain: cerebral cortex limbic region of cortex
hypothalamus
corpus callosum
limbic region
of cortex
cerebral cortex
amygdala
hippocampus
thalamus
B) Limbic System
Parts of thalamus: Information relay
Amygdala: Produces sensations of pleasure, fear, or sexual arousal
Hippocampus: Formation of long-term memory

27. Things To Do After Lecture 14…
Reading and Preparation:
Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms.
Self-Quiz: Ch. 48 #1-3, 5; Ch. 49 # 2, 4, 5, 6 (correct answers in back of book)
Read chapters 48 & 49, focus on material covered in lecture (terms, concepts, and figures!)
Skim next lecture.
“HOMEWORK” (NOT COLLECTED – but things to think about for studying):
Explain the difference between the motor and autonomic nervous systems.
Diagram a basic neuron and describe how an action potential begins and propagates. For sensory, motor, interneurons explain the location of each region with respect to peripheral or central nervous system.
Compare and contrast the embryonic vertebrate brain with that of adults.
List the regions of the brain (with functions) from the “bottom” of the brain, toward the “top”.