8.4 The Peripheral Nervous System UNIT 4 Chapter 8: The Nervous System and Homeostasis Section 8.4 8.4 The Peripheral Nervous System The peripheral nervous system consists of nerves that link the brain and spinal cord to the rest of the body. The two main divisions are: the somatic system the autonomic system
The Somatic System UNIT 4 Chapter 8: The Nervous System and Homeostasis Section 8.4 The Somatic System -Controls the voluntary movement of skeletal muscles. -Its neurons service the head, trunk, and limbs. The spinal nerves are named for the region of the body where they are located: cervical, thoracic, lumbar, and sacral. The somatic system includes 12 pairs of cranial nerves and 31 pairs of spinal nerves, all of which are myelinated. Each spinal nerve contains both sensory and motor neurons.
The Autonomic System UNIT 4 Chapter 8: The Nervous System and Homeostasis Section 8.4 The Autonomic System -Controls involuntary glandular secretions and the functions of smooth and cardiac muscle. -Maintains homeostasis by adjusting the body to variations in the external and internal environments without an individual having to think about it. -Controlled by the hypothalamus & medulla oblongata -Divided into sympathetic & parasympathetic systems
The Sympathetic Nervous System UNIT 4 Chapter 8: The Nervous System and Homeostasis Section 8.4 The Sympathetic Nervous System The sympathetic nervous system is typically activated in stressful situations and is often referred to as the “fight-or-flight” response. Sympathetic neurons and adrenal glands release epinephrine and norepinephrine( excitatory neurotransmitters) that activate the stress response (increased heart rate, increased blood pressure, and decreased digestion). Meditation may reduce the activity of the sympathetic nervous system.
The Parasympathetic Nervous System UNIT 4 Chapter 8: The Nervous System and Homeostasis Section 8.4 The Parasympathetic Nervous System The parasympathetic nervous system is activated when the body is calm and at rest. It acts to conserve energy and is often referred to as the “rest-and-digest” response. It uses the neurotransmitter acetylcholine to control responses (reduced heart rate, reduced blood pressure, and increased digestion). Both branches of the autonomic system work in opposition to balance reactions and maintain homeostasis.
Functions of the Sympathetic and Parasympathetic Nervous Systems UNIT 4 Chapter 8: The Nervous System and Homeostasis Section 8.4 Functions of the Sympathetic and Parasympathetic Nervous Systems