1. The Nervous System

2. The nervous system Functions
Receive information from internal/external environment or other nerve cells
Integrate the information and produce an appropriate output signal
Conduct the signal
Transmit the signal to other nerve cells, glands, or muscles

3. The nervous system Structural regions of typical vertebrate neurons
Dendrites respond to external signals through the binding of receptor sites
Cell body serves as the integration center and carries out basic metabolism
3. Axon conducts signals long distances
4. Synaptic terminal releases neurotransmitters to communicate with other cells

4. Receive signals from other neurons. Synaptic terminals:
Dendrites:
Receive signals from other neurons.
Synaptic terminals:
Bring signals from other neurons.
Cell body:
Integrates signals; coordinates metabolic activities.
Action potential starts here.
Myelin:
Insulates the axon and speeds conduction.
Arrows indicate direction of travel of action potential.
Exposed areas of axon.
Figure: 24-01
Title:
A neuron, showing its specialized parts and their functions.
Caption:
Dendrites of other neurons receive signals.
Synaptic terminals:
Transmit signals to other neurons.

5. The nervous system Mechanisms of neural activity
1. Electrical signals and membrane potentials
a. Resting potential
b. Action potential

6. action potential threshold resting potential Figure: 24-02 Title:
An action potential makes the inside of a neuron positive
Caption:
A recording (by oscilloscope) of the electrical events in a neuron. The resting potential is about 60 millivolts negative with respect to the outside. When the neuron is stimulated to threshold, the inside rapidly becomes positively charged. Shortly thereafter, the resting potential is reestablished.

9. The nervous system Mechanisms of neural activity
Communication between neurons
a. Synapses
1) Presynaptic neurons
2) Postsynaptic neurons
b. Neurotransmitters and ion gradients
c. Excitatory and inhibitory potentials

10. An action potential is initiated.
presynaptic neuron
postsynaptic neuron 1
An action potential is initiated. 2
The action potential reaches the synaptic terminal of the presynaptic neuron.
synaptic vesicle
synaptic terminal
Figure: 24-03
Title:
The structure and operation of the synapse.
Caption:
The synaptic terminal contains numerous vesicles that enclose a neurotransmitter for which the postsynaptic neuron has membrane receptors. When the neurotransmitter binds to postsynaptic receptors, ion channels open, causing a postsynaptic potential in the postsynaptic cell. 3
Synaptic vesicles release neurotransmitter.
gap
dendrite of postsynaptic neuron
neurotransmitter
ion channel closed 4
Receptor binds neurotransmitter and opens ion channel.
plasma membrane of postsynaptic neuron

11. Figure: 24-T01
Title:
Some important neurotransmitters.
Caption:

12. The nervous system Operation of the nervous system
1. Four basic requirements
a. Determine the type of stimulus
1) Wiring patterns in the brain
2) Nervous system monitors which neurons are firing

13. The nervous system b. Signal the intensity of the stimulus
Operation of the nervous system
b. Signal the intensity of the stimulus
All action potentials are of the same magnitude
Frequency of action potentials signals intensity
3) Number of firing neurons signals intensity

14. gentle touch; 1 fires slowly, 2 is silent
(a) Gentle
touch
gentle touch; 1 fires slowly, 2 is silent
(b) Moderate
pressure
Figure: 24-04
Title:
Determining the intensity of a stimulus.
Caption:
Consider two touch receptors that have endings in adjacent patches of skin. (a) A gentle touch elicits only a few action potentials from one sensory neuron but none from another. (b) Moderate pressure stimulates only the first receptor, which now fires faster, informing the brain that the touch is more intense than before. (c) Strong pressure activates both receptors, firing the first one very fast and the other more slowly, thus signaling that the pressure is very intense and centered over the faster-firing receptor.
moderate pressure; 1 fires more rapidly, 2 is silent
(c) Strong
pressure
strong pressure: both 1 and 2 fire

15. The nervous system c. Integrate information from many sources
Operation of the nervous system
c. Integrate information from many sources
Convergence of many neuron signals to fewer neurons
d. Initiate and direct the response
1) Divergence—signals sent from a few decision-making cells to many neurons controlling the responses

16. white matter (contains myelinated axons) gray matter
(contains cell bodies of motor and association neurons)
dorsal root
(contains axons of sensory neurons)
central canal
dorsal root ganglion
(contains cell bodies of sensory neurons)
Figure: 24-06
Title:
The spinal cord in cross-section.
Caption:
peripheral nerve
ventral root (contains axons of motor neurons)

17. The nervous system Operation of the nervous system
Neural control of behavior
a. Pathway contains four components
1) Sensory neurons—respond to a stimulus
2) Association neurons—activate motor neurons
3) Motor neurons—activate muscles or glands
4) Effectors—usually muscles or glands

18. The nervous system Neural control of behavior
b. Simple behavior – the reflex
c. Complex behaviors

19. Step 1: a painful stimulus activates a pain receptor
dorsal root
association neuron
sensation relayed to the brain
Step 2: signal transmitted by a sensory neuron
REFLEX
ARC
receptor
stimulus
Step 5: effector muscle causes withdrawal response
Figure: 24-07
Title:
The pain-withdrawal reflex.
Caption:
This simple reflex circuit includes a sensory neuron that has pain-sensitive endings in the skin and a long fiber leading to the spinal cord. The sensory neuron stimulates an association neuron in the spinal cord, which in turn stimulates a motor neuron in the cord. An association neuron also sends the signal to the brain, informing it of the danger.
effector
ventral root
Step 3: signal transmitted within the spinal cord
Step 4: activation of a motor neuron stimulates the appropriate muscle

20. The human nervous system
A. Peripheral nervous system
Somatic nervous system—controls voluntary movement
Autonomic nervous system—controls involuntary responses
a. Sympathetic division—energetic and stressful activities
b. Parasympathetic division—leisure and maintenance activities

21. Figure: 24-05
Title:
The organization and functions of the vertebrate nervous system.
Caption:

22. The human nervous system
B. Central nervous system (CNS)
1. Brain
a. Functions
1) Integration: senses, processes, and directs responses

23. The human nervous system
Brain Structure
1) Hindbrain
a) Contains the medulla, pons, and cerebellum
Controls automatic functions of breathing, heart rate, blood pressure, swallowing, sleeping, and coordination of movements
2) Midbrain
a) Contains the reticular formation
Center for relay control and filtering sensory messages

24. FOREBRAIN (within dashed blue line)
meninges
cerebral cortex
skull
FOREBRAIN (within dashed blue line)
corpus callosum
hypothalamus
thalamus
pituitary gland
Figure: 24-08
Title:
The human brain.
Caption:
A section through the midline of the human brain reveals some of its major structures.
MIDBRAIN
cerebellum
pons
HINDBRAIN
medulla
spinal cord

25. The human nervous system
Brain Structure
3) Forebrain
a) Thalamus shuttles sensory information to the cerebrum and limbic system
b) The limbic system controls instincts and emotions
i) The limbic system includes the hypothalamus, amygdala, and hippocampus
c) The cerebral cortex produces thoughts and perceptions
i) Damage to the cerebral cortex

26. cerebral cortex thalamus hypothalamus hippocampus amygdala
Figure: 24-09
Title:
The limbic system and thalamus.
Caption:
In this view of the brain, the left cerebral cortex is transparent.
hypothalamus
hippocampus
amygdala

27. higher intellectual functions Visual Association Area hand
Primary Motor Area
Primary
Sensory Area
Sensory
Association
Area
leg
trunk
arm
higher intellectual functions
Visual
Association
Area
hand
face
tongue
Primary
Auditory
Area
Primary
Visual
Area
Figure: 24-10
Title:
The cerebral cortex.
Caption:
Structural (colored) and functional (labeled) regions of the human left cerebral cortex. A map of the right cerebral cortex would be similar, except that speech and language are less well developed there.
Speech
Motor Area
memory
language comprehension and formation

28. The human nervous system
B. Central nervous system (CNS) (cont.)
2. Spinal cord
a. A cable of axons protected by the backbone
b. Conducts signals to the brain
c. Spinal cord injuries

29. The human nervous system
C. The brain and the mind
1. Brain and mind research
2. Left-brain functions
3. Right-brain functions
D. Memory and learning
1. Working memory
2. Long-term memory
3. Learning involves the hippocampus
4. Neither is well understood