Introduction to:

The Nervous System  Highly organized network of billions on neurons and even more neuroglia  Contains: Brain Cranial Nerves Spinal Cord Spinal Nerves Ganglia Enteric Plexus Sensory Receptors

Parts of the Nervous System: Brain  Enclosed by skull  Contains 100 billion neurons

Parts of the Nervous System: Cranial Nerves  12 pair  Labeled I-XII  Emerge from base of brain

Parts of the Nervous System: Nerve  Bundle of hundreds to thousands of axons plus connective tissue and blood vessels  Lie outside of the brain and spinal cord  Each has defined path and serves specific region of the body

Parts of the Nervous System: Spinal Cord  Connects to the brain  Encircled by bones of the vertebral column  Contains approx. 100 million neurons

Parts of the Nervous System: Spinal Nerves  Emerge from the spinal cord  31 pairs  Serve specific regions on each side of the body  Spinal nerve diagram: pain-free-drug-free/spinal-nerves-2/

Parts of the Nervous System: Ganglia  Small masses of nervous tissue located outside of the brain and spinal cord  Contain cell bodies of neurons  Closely associated with cranial and spinal nerves

Parts of the Nervous System: Enteric Plexus  Extensive network of neurons  Found in the walls of organs in the gastrointestinal (GI) tract  helps regulate the digestive system

Parts of the Nervous System: Sensory Receptors  Dendrites of sensory neurons or  separate specialized cells that monitor change in internal and external environment

Functions of the Nervous System 1. Sensory Function Sensory receptors detect different types of internal and external stimuli Sensory Neurons (Afferent Neurons) carry sensory info. TO the spinal cord and brain through cranial and spinal nerves

Functions of the Nervous System 2. Integrative function Information processed by analyzing and storing information and making decisions for appropriate responses Perception – conscious awareness of sensory stimuli Interneurons – participate in integration contain short axons contact nearby neurons in the brain and spinal cord Comprise vast major of neurons in the body

Functions of the Nervous System 3. Motor Function: Response to stimulus through use of motor neurons (Efferent Neurons) Motor Neurons carry information FROM the brain toward the spinal cord to muscles and glands through cranial and spinal nerves Causes muscle contraction and gland secretions

Organization of the Nervous System  Central Nervous System  Peripheral Nervous System Somatic Nervous System Autonomic Nervous System ○ Sympathetic Division ○ Parasympathetic Division Enteric Nervous System

Central Nervous System (CNS)  Consists of: Brain and Spinal Cord  Integrates and correlates different kinds of sensory information  Source of thoughts, emotions, and memories  Most nerve impulses that stimulate muscle contraction and gland secretion originate in the CNS

Peripheral Nervous System  Consists of: cranial nerves, spinal nerves, ganglia and sensory receptors  3 divisions Somatic Nervous System Autonomic Nervous System Enteric Nervous System

Somatic Nervous System (SNS)  Voluntary  Consists of sensory neurons that convey info from receptors in the head, body wall and limbs and receptors for special senses (vision, hearing, taste, smell) TO the CNS  Consists of motor neurons that conduct impulses FROM the CNS to skeletal muscles

Autonomic Nervous System (ANS)  Involuntary  Consists of sensory neurons which convey information from receptors in organ (i.e. stomach, lungs) TO the CNS  Consists of motor neurons that conduct impulses FROM CNS to smooth muscle, cardiac muscle, glands

Autonomic Nervous System (ANS)  2 Divisions of the ANS Sympathetic Division ○ Helps support exercise and emergency actions of “fight or flight” response Parasympathetic Division ○ Takes care of “rest and digest” activities  *The 2 divisions usually have opposing actions Ex: Sympathetic neurons speed the heartbeat and parasympathetic neurons slow it down

Enteric Nervous System (ENS)  Involuntary  “the brain of the gut”  Sensory neurons monitor chemical changes within the GI tract and the stretching of its walls  Motor neurons govern contractions of GI tract smooth muscle secretions of GI tract organs (stomach acid secretions) activity of GI tract endocrine cells