Transcript Nervous Systems (ch. 48 & 49) Sum13

Lecture 14 – Ch. 48 & 49: Nervous Systems
I.
Neuron Structure
and Function
II. Relationship
between Stimuli
 Input
III. Nervous System
Organization
IV. Brains
V. Preparation for
next lecture
Neurons
Specialized “excitable” cells: receive input, integrate, send output
1 Synaptic terminals:
Bring signals from
other neurons.
2 Dendrites:
Receive signals
from other neurons.
3 Cell body:
Integrates signals;
Coordinates.
synaptic
terminal
4 Action potential
starts here.
5 Axon: Conducts
the action potential.
dendrite
synapse
6 Synaptic terminals:
Transmit signals to
other neurons.
7 Dendrites
(of other neurons).
4
What parts of neurons are OUTSIDE the CNS?
1. All sensory, motor, and interneurons neurons
2. Sensory neuron dendrites & cell bodies AND
motor neuron axons
3. Interneurons only
4. Motor neuron dendrites and interneuron axons
Neurons
Neurons are electrical:
• At rest, neurons maintain
an electrical difference
across their membrane
• (-) inside cell; (+) outside cell
• charge = about -70 mV
Na+ pumped out,
K+ pumped in, but
K+ can leak out
Neurons
Synapse: Region
connecting two neurons
or neuron and muscle
synaptic
terminal
synaptic
vesicle
Neurotransmitter
signals next
neuron.
Signal reaches
end of axon.
Synaptic vesicles
release neurotransmitter.
Neurotransmitter
may excite or
inhibit the next
neuron
gap
neurotransmitter
Receptor binds
neurotransmitter.
dendrite of
postsynaptic
neuron
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
(+) inside cell; (-) outside cell
• During action potential,
Na+ channels open,
flows in
• Charge difference lost
= depolarized
Na+
action potential
(axon)
(extracellular fluid)
Na+
• Triggers K+ channels
to open, flows out
action potential
(axon)
• Repolarized
K+
(extracellular fluid)
Action Potentials
Na+ channels open
K+
channels
open
Before K+ channels close, greater
charge difference = hyperpolarized
Action Potentials
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)
Action Potentials
Action potentials can be measured electrically:
• Stimulation from a neighbor neuron excites the cell
(brief increase in voltage = EPSP)
potential
(millivolts)
• Inhibition from another neuron causes a brief decrease
in voltage (IPSP)
threshold
resting
potential
EPSP
IPSP
time
(milliseconds)
Action Potentials
synaptic
vesicle
Pre-synaptic
terminal
IPSP = inhibitory postsynaptic potential
(-) Neurotransmitter
potential
(millivolts)
neurotransmitter
dendrite of
Post-synaptic
neuron
EPSP = excitatory
post-synaptic potential
(+) Neurotransmitter
Individual EPSP & IPSP weak
EPSP
IPSP
time
(milliseconds)
Action Potentials
Action Potentials
• Sum of all excitatory & inhibitory ‘blips’ =
summation
action potential
potential
(millivolts)
• If threshold
voltage is
reached, an
action
potential
occurs
resting
potential
threshold
Less (-)
More (-)
time
(milliseconds)
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
Stimuli  Input
Information Coding in the Nervous System:
1 fires slowly
1 fires rapidly
2 silent
2 fires slowly
1
fires moderately
2 silent
Stimuli  Input
Information Coding in the Nervous System:
3) 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)
Spinal Cord:
Nervous System Organization
Myelin = Insulation around axons
• Increases AP conduction rate
Nervous System Organization
Spinal Cord:
What part of the spinal cord contains
motorneuron cell bodies?
1.
2.
3.
4.
White matter
Dorsal root ganglia
Gray matter
Ventral roots
CNS
Nervous System Organization
Brain and Spinal Cord
Motor Pathways
PNS
Sensory Pathways
Sensory neurons
registering external
stimuli
Sensory neurons
registering external
stimuli
Somatic nervous
system
(voluntary)
Sympathetic nervous
system
"fight or flight"
Autonomic nervous
system
(involuntary)
Parasympathetic nervous
system
"rest and repose"
Nervous System Organization
If you are surprised by a “predator”, what
happens in your nervous system?
1.
2.
3.
4.
Sympathetic nervous system increases heart rate
Somatic nervous system increases heart rate
Autonomic nervous system increases saliva
Parasympathetic NS increases saliva secretion
The Brain:
Human Brain
meninges
skull
1) Hindbrain:
Automatic
Behaviors
A) Medulla: Controls
breathing, heart rate,
blood pressure
B) Pons: Controls
wake/sleep transitions;
sleep stages
C) Cerebellum:
Coordinates movement
hindbrain
cerebellum
pons
medulla
spinal cord
Human Brain
The Brain:
pituitary
gland
pineal
gland
midbrain
- Reticular
Formation
2) Midbrain: Relay /
“Screening” Center
A) Reticular Formation:
Controls arousal of brain
• Filters sensory input from body
B) Visual / Auditory Reflex Centers
The Brain:
Human Brain
cerebral
cortex
3) Forebrain (Cerebrum):
“Seat of Consciousness”
A) Cerebral Cortex
• Two hemispheres (Connection =
Corpus Callosum)
• Left hemisphere controls right side
of body (and vise versa)
corpus
callosum
The Brain:
Human Brain
Parietal
Lobe
Frontal
Lobe
Occipital
Lobe
Temporal
Lobe
3) 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
Human Brain
primary
sensory area
Frontal
Lobe
primary
motor area
premotor
area
higher
intellectual
functions
leg
trunk
arm
hand
Parietal
Lobe
sensory
association
area
face
speech
motor area
tongue
primary
auditory
auditory association
area
area: language
comprehension
memory
Temporal
Lobe
visual
association
area
primary
visual
area
Occipital
Lobe
Human Brain
Motor and
Sensory
areas
Which is a correct match between
brain region and function:
1.
2.
3.
4.
Parietal lobe : visual processing
Reticular formation : filters sensory input
Cerebellum : controls sleep stages
Cerebrum : dictates breathing rate
Human Brain
Cortical Regions Involved
in Different Tasks:
Hearing Words
Seeing Words
Reading Words
Generating Verbs
0
max
The Brain:
Human Brain
hypothalamus
thalamus
3) Forebrain (Cerebrum)
B) Limbic System
• Produce emotions; form memories
C) Thalamus
• Relays information from body to limbic system / cerebral cortex
The Brain:
Human Brain
limbic region
of cortex
B) Limbic System
• Hypothalamus:
Homeostatic control center
• Amygdala: Produces
sensations of pleasure,
fear, or sexual arousal
• Hippocampus:
Formation of long-term memory
C) Thalamus
• Relays to limbic system /
cerebral cortex
cerebral cortex
corpus
callosum
thalamus
hypothalamus
hippocampus
amygdala
Damage to the hippocampus could result in:
1.
2.
3.
4.
Failure to understand speech
Reduced fear response
Lack of homeostatic control
Loss of long-term memory formation
Things To Do After Lecture 14…
Reading and Preparation:
1.
Re-read today’s lecture, highlight all vocabulary you do not
understand, and look up terms.
2.
Self-Quiz: Ch. 48 #1-3, 5; Ch. 49 #1, 2, 4, 5, 6 (correct answers in
back of book)
3.
Read chapters 48 & 49, focus on material covered in lecture (terms,
concepts, and figures!)
4.
Skim next lecture.
“HOMEWORK” (NOT COLLECTED – but things to think about for studying):
1.
Explain the difference between the somatic and autonomic nervous
systems.
2.
Diagram a basic neuron – for sensory, motor, and interneurons explain
the location of each region with respect to peripheral or central nervous
system.
3.
Compare and contrast the embryonic vertebrate brain with that of adults.
4.
List the regions of the brain (with functions) from the “outside” of the
brain, inward.