1. Nervous System
Transmission of signals for communication and for coordination of body systems

2. Organization of Body Systems
Organ System
Central Nervous System
Organ
Brain
Tissue
Nerve
Cell
Neuron

3. Structure of a Neuron Dendrites (receive signals)
Cell Body (maintains cell metabolism)
Myelin Sheath (insulator)
Axon terminal
Axon (conducts signals)
Dendrite of another neuron
Axon of another neuron

4. Transmission of Nerve Impulse Along a Neuron
Involves a change in charge across the neuron’s membrane, caused by the movement of ions
Action Potential = rapid depolarization and repolarization of membrane

5. Electrical Events During An Action Potential80 40
-40
-80
Recorded Potential (millivolts)
Action Potential
Extracellular Fluid (uncharged) 2
depolarization
Threshold
Resting Potential
repolarization 3 1
EPSP
polarized
IPSP
Time (milliseconds)

6. Resting Potential Depends on Ionic Gradients
Net negative charge inside neuron
Inside:
Potassium ions are pumped into cell
Na+
Na+
Cl-
Large organic molecules cannot pass through membrane
Cl-
Na+
Org- K+
Org- K+
Org- K+
Org-
Org-
Org-
Na+ K+ K+
Outside:
Cl-
Cl- K+
Org-
Org-
Sodium ions are pumped out
Na+
Na+
Cl-
Org-
Chloride ions found in extra-cellular fluid
Cl- K+

7. An Unstimulated Neuron at Resting Potential
(Extracellular Fluid)
Na+
Cl-
Na+ K+
Na+
Cl-
Cl-
Cl-
Na+
Sodium Channel (closed)
Potassium Channel
(Neuronal Membrane) K+
Org-
Org-
Org- K+ K+
Org-
Org- K+
(Neuronal Cytoplasm, negatively charged)

8. Action Potential (Extracellular Fluid)
Depolarization due to influx of sodium
Repolarization due to efflux of potassium
(Extracellular Fluid)
Org-
Na+ K+
Cl-
Cl-
Na+ K+ K+ K+
Na+
Na+
Na+
Org-
Na+ K+
(Neuronal Cytoplasm, positively charged)
(negatively charged)

9. Propagation of an Action Potential

10. Propagation of an Action Potential

11. Intensity of Nerve Signals1 2 1
Fires slowly
Gentle Touch 2
Silent 1 2 1
Fires more rapidly
Moderate Pressure 2
Silent 1 2 1
Fires even faster
Strong Pressure 2
Fires slowly

12. Transmission of Nerve Impulses Between Neurons
Signal is carried by neurotransmitters that diffuse across the space between neurons
Synapse: junction between neurons
Synaptic cleft: space between neurons
Neurotransmitters bind to receptors on next neuron, opening ion channels
synapse

13. Structure and Operation of the Synapse
1 An action potential is initiated
Structure and Operation of the Synapse
2 Action potential reaches synaptic terminal
3 Synaptic vesicles release neurotransmitter
5 Action Potential can be triggered in post-synaptic cell
4 Receptor binds neurotransmitter & opens ion channel

14. Transmission of Nerve Impulses Between Neurons
Neurotransmitters can be
Stimulatory: initiate action potential
eg. Acetylcholine
Inhibitory: prevent action potential
eg. Dopamine

15. Neurotransmitters carry signals to
muscle cells to stimulate contraction.

16. Applying Your Knowledge
Potassium Ions (K+)
Neurotransmitters
Sodium Ions (Na+)
Which one is responsible for
Transmission of a nerve impulse across a synapse?
Depolarization of a neuron’s membrane?
Transmission of a nerve impulse along an axon?
Repolarization of a neuron’s membrane?

17. Types of Neurons Receives information from environment
Carries signal between sensory and motor neurons
Generates a response

18. Pain-Withdrawal Reflex
2. Signal transmitted by sensory neuron
1. Pain receptor stimulated
3. Signal transmitted within spinal cord
4. Motor neuron stimulates muscle
5. Effector causes withdrawal

19. Nervous System Organization
Central Nervous System (CNS)
brain
spinal cord
Peripheral Nervous System (PNS)
Sensory nerves
carry sensory information
into brain and spinal cord
Motor nerves
carry motor information
from CNS to effectors
somatic sensory
nerves: signals
from skin,
muscles,
joints, special
senses
Somatic motor
nerves: signals
to skeletal
muscles,
voluntary
Autonomic motor nerves: signals to smooth
muscle, cardiac
muscle, glands,
involuntary
visceral sensory
nerves:
signals from
body organs
Sympathetic
division
“fight or flight”
Parasympathetic
division
“rest and digest”

20. Autonomic Nervous System
dilates pupils
constricts pupils
dilates air passages
constricts bronchioles
speeds heart
slows heart
decreases stomach and intestinal activity
increases stomach and intestinal activity

21. Cortex: thinking, learning, memory, speech movement, senses
Parts of the Brain
sends sensory input to cerebrum
homeostasis
breathing, heart rate, blood pressure
muscle coordination

22. Sensory Areas on Cerebral Cortex

23. Limbic System and Thalamus
emotions, drives, behaviors
Thalamus
Cerebral Cortex
relay center
Hippocampus
Hypothalamus
Amygdala

24. Maintaining Homeostasis
Negative Feedback: A change that initiates a series of events to counteract the change and restore the original state

25. Applying Your Knowledge
Central Nervous System
Somatic Nervous System
Autonomic Nervous System
Which one
Is responsible for increasing breathing rate when you start running?
Includes the spinal cord?
Controls muscle movement?