2. Chapter 19
Nervous System
19.1 Structure of the Nervous System
Neurons
Neurons are specialized nerve cells that help you gather information about your environment, interpret the information, and react to it.
Neurons consist of three main regions: the dendrites, a cell body, and an axon.

3. The axon passes those impulses on to the other neurons or muscles.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
Dendrites pass signals they receive on to the cell body in electrical impulses.
The axon passes those impulses on to the other neurons or muscles.

4. Interneurons carry impulses to motor organs.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
There are three kinds of neurons: sensory neurons, interneurons, and motor neurons.
Sensory neurons send impulses from receptors in the skin and sense organs to the brain and spinal cord.
Interneurons carry impulses to motor organs.

5. resulting in a secretion or movement.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
Motor neurons carry impulses away from the brain and spinal cord to a gland or muscles,
resulting in a secretion
or movement.
The nerve impulse completes a reflex arc, or a nerve pathway that
consists of a sensory neuron, an interneuron,
and a motor neuron.

8. Neurons at rest do not conduct impulses.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
A Nerve Impulse
Neurons at rest do not conduct impulses.
Sodium ions (Na+) collect on the outside of the cell membrane.

9. Potassium ions (K+) collect on the inside of the cell membrane.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
Potassium ions (K+) collect on the inside of the cell membrane.
Negatively charged proteins actively transport sodium ions out of the cell and
potassium ions into the cell.

10. A nerve impulse is also known as an action potential.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
An Action Potential
A nerve impulse is also known as an action potential.
The minimum stimulus to cause an action potential to be produced is called a threshold.

11. 19.1 Structure of the Nervous System
Chapter 19
Nervous System
19.1 Structure of the Nervous System
When a stimulus reaches threshold, channels open in the plasma membrane.
Sodium ions are rapidly pumped through these channels causing a temporary change in the electrical charges.
More positive charges are now inside the membrane.

12. The potassium restores the positive charge outside the cell.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
The now positive charge inside the membrane causes other channels to open and the potassium is quickly pumped out of the cell.
The potassium restores the positive charge outside the cell.

13. Chapter 19
Nervous System
19.1 Structure of the Nervous System
This rapid positive to negative to positive charge reversal moves along the axon like a wave.
The movement can be seen by finding the sodium-potassium reversal pattern in the three diagrams.

14. Speed of an Action Potential
Chapter 19
Nervous System
19.1 Structure of the Nervous System
Speed of an Action Potential
Nodes along the axon allow ions to pass through the myelin layer to the plasma membrane.
The ions jump from node to node and increase the speed of the impulse.
Visualizing Action Potential

15. An action potential is carried across these gaps by neurotransmitters.
Chapter 19
Nervous System
19.1 Structure of the Nervous System
The Synapse
The small gap between the axon of one neuron and the dendrite of another neuron is called a synapse.
An action potential is carried across these gaps by neurotransmitters.

16. The brain is sometimes called the control center of the entire body.
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The Brain
The brain is sometimes called the control center of the entire body.
Divided into the cerebrum, the cerebellum, and the brain stem.

17. Chapter 19
Nervous System
19.2 Organization of the Nervous System
The cerebrum is divided into two halves called the left and right hemispheres.
The functions of the brain include thought processes (learning), memory, language, speech, voluntary body movements, and sensory perception.

18. The cerebellum controls balance, posture, and coordination.
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The cerebellum controls balance, posture, and coordination.
The skeletal muscles are controlled to make your motor skills coordinated and smooth.

19. The pons also aids in breathing.
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The brain stem connects the brain and spinal cord and is composed of the medulla oblongata and the pons.
The medulla oblongata helps control breathing rate, heart rate, and blood pressure.
The pons also aids in breathing.

20. Regulates body temperature, thirst, appetite, and water balance.
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The hypothalamus, located between the brain stem and the cerebrum, is essential for homeostasis.
Regulates body temperature, thirst, appetite, and water balance.

21. Nerve column that extends from the brain to the lower back.
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The Spinal Cord
Nerve column that extends from the brain to the lower back.
Protected by the vertebrae
Processes reflexes

22. The Peripheral Nervous System
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The Peripheral Nervous System
A nerve is a bundle of axons and may contain sensory and motor neurons.
The peripheral nervous system (PNS) contains all the neurons that are not part of the central nervous system.

23. The Somatic Nervous System
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The Somatic Nervous System
Nerves in the somatic nervous system relay information from external sensory receptors to the central nervous system, and motor nerves relay information from the central nervous system to skeletal muscles.
Voluntary movements and reflexes are a part of the somatic nervous system.

24. The Autonomic Nervous System
Chapter 19
Nervous System
19.2 Organization of the Nervous System
The Autonomic Nervous System
The autonomic nervous system carries impulses from the central nervous system to the heart and other internal organs.
The body responds involuntarily, not under conscious control.

25. There are two branches of the autonomic nervous system.
Chapter 19
Nervous System
19.2 Organization of the Nervous System
There are two branches of the autonomic nervous system.
The sympathetic nervous system is most active in times of emergency or stress when the heart rate and breathing rate increase.
The parasympathetic nervous system is most active when the body is relaxed.

26. Chapter 19
Nervous System