peripheral nervous system

the sensory division

The sensory division carries messages from sense organs and internal organs to the central nervous system. Human beings have several senses. They include sight, hearing, balance, touch, taste, and smell. We have special sense organs for each of these senses. What is the sense organ for sight? For hearing? Sensory neurons in each sense organ receive stimuli, or messages from the environment that cause a response in the body. For example, sensory neurons in the eyes send messages to the brain about light. Sensory neurons in the skin send messages to the brain about touch. Our sense organs recognize sensations, but they dont tell us what we are sensing. For example, when you breathe in chemicals given off by baking cookies, your nose does not tell you that you are smelling cookies. Thats your brains job. The sense organs send messages about sights, smells, and other stimuli to the brain ( Figure 1.3). The brain then reads the messages and tells you what they mean. A certain area of the brain receives and interprets information from each sense organ. For example, information from the nose is received and interpreted by the temporal lobe of the cerebrum. Which senses would be stimulated by these raspberries?

textbook_image

textbook_image

the peripheral nervous system

There are other nerves in your body that are not found in the brain or spinal cord. The peripheral nervous system (PNS) ( Figure 1.1) contains all the nerves in the body that are found outside of the central nervous system. They include nerves of the hands, arms, feet, legs, and trunk. They also include nerves of the scalp, neck, and face. Nerves that send and receive messages to the internal organs are also part of the peripheral nervous system. The peripheral nervous system is divided into two parts, the sensory division and the motor division. How these divisions of the peripheral nervous system are related to the rest of the nervous system is shown below ( Figure 1.2). Refer to the figure as you read more about the peripheral nervous system in the text that follows.

textbook_image

the motor division

The motor division of the peripheral system carries messages from the central nervous system to internal organs and muscles. The motor division is also divided into two parts ( Figure 1.2), the somatic nervous system and the autonomic nervous system. The somatic nervous system carries messages that control body movements. It is responsible for activities that are under your control, such as waving your hand or kicking a ball. The girl pictured below ( Figure 1.4) is using her somatic nervous system to control the muscles needed to play the violin. Her brain sends messages to motor neurons that move her hands so she can play. Without the messages from her brain, she would not be able to move her hands and play the violin. The autonomic nervous system carries nerve impulses to internal organs. It controls activities that are not under your control, such as sweating and digesting food. The autonomic nervous system has two parts: 1. The sympathetic division controls internal organs and glands during emergencies. It prepares the body for fight or flight ( Figure 1.5). For example, it increases the heart rate and the flow of blood to the legs, so you can run away from danger. 2. The parasympathetic division controls internal organs and glands during the rest of the time. It controls processes like digestion, heartbeat, and breathing when there is not an emergency. Have you ever become frightened and felt your heart start pounding? How does this happen? The answer is your autonomic nervous system. The sympathetic division prepared you to deal with a possible emergency by increasing

textbook_image

textbook_image

instructional diagrams

No diagram descriptions associated with this lesson

questions

there are nerves that send and receive messages to the internal organs.

-->  a. true

b. false

the peripheral nervous system sends messages along nerves from the brain to the spinal cord.

a. true

-->  b. false

which part of the pns carries messages from internal organs to the cns?

-->  a) the sensory division

b) the motor division

c) the somatic nervous system

d) the autonomic nervous system

which part of the pns controls involuntary activities such as activities such as digestion?

a) the sensory division

b) the motor division

c) the somatic nervous system

-->  d) the autonomic nervous system

what part of the pns allows you to circle the correct answer to this question?

-->  a) the somatic nervous system

b) the autonomic nervous system

c) the sympathetic division

d) the parasympathetic division

what part of the pns increases the heart rate in an emergency situation?

a) the sensory division

b) the motor division

-->  c) the sympathetic division

d) the parasympathetic division

what part of the nervous system tells you that cookies are being baked?

-->  a) the central nervous system

b) the sensory division

c) the autonomic nervous system

d) the somatic nervous system

diagram questions

No diagram questions associated with this lesson