THE NERVOUS SYSTEM

Introduction to:

The Nervous System

Highly organized network of billions on neurons and even more neuroglia

Contains:

Brain Cranial NervesSpinal CordSpinal NervesGangliaEnteric PlexusSensory 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:

http://vitalfrequency.com/blogs/2010/03/09/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 SystemAutonomic 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 SystemAutonomic Nervous SystemEnteric 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” responseParasympathetic Division

○ Takes care of “rest and digest” activities

*The 2 divisions usually have opposing actionsEx: 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 governcontractions of GI tract smooth musclesecretions of GI tract organs (stomach acid

secretions)activity of GI tract endocrine cells