The Nervous System

Functions of the Nervous SystemRespond to internal and external stimuliTransmit nerve impulses to and away from CNSInterpret nerve impulses at the cerebral cortexAssimilate experiences in memory and learningInitiate glandular secretions and muscle

contractionProgram instinctual behavior

Divided into…Central Nervous System (CNS)Peripheral Nervous System (PNS)

Central Nervous System (CNS)Composed of:BrainSpinal Cord

Peripheral Nervous System (PNS)Composed of:

Cranial Nerves (from the brain)Spinal Nerves (from the spinal cord)Ganglia (clusters of cell bodies of

neurons)Plexuses (networks of nerves)

Autonomic Nervous System (ANS)Functional division of nervous systemStructures in the brain are the control

centers of the ANSNerves are the pathways for

conduction of these nerve impulsesFunctions to automatically speed up

or slow down body activities

NeuronsNerve cells found in both CNS and PNS

Parts of a neuronCell Body

Similar to other types of cellsContains a nucleus

DendritesExtensions that project from the cell bodyShort and branchingReceive signals from other neuronsTransmit impulses to the cell body

AxonCovered in a myelin sheath (like insulation on a wire)

Myelin is produced by Schwann cellsTransmit impulses away from the cell body

Types of NeuronsSensory Neurons: transmit impulses to the CNS

Somatic sensory: carry impulses from receptors in the skin, bones, muscles, and joints

Visceral sensory: carry impulses from the visceral organs

Motor Neurons: transmit impulses away from the CNS

Association neurons (interneurons): conduct impulses from sensory to motor neurons

CNS: The BrainFive Regions

Brain Region Structures

Telencephalon Cerebrum

Diencephalon Thalamus, Hypothalamus, Pituitary GlandMesencephalon Superior & Inferior colliculus, Cerebral peduncles

Metencephalon Cerebellum and PonsMyelencephalon Medulla oblongata

Cerebrum (Telencephalon)Two hemispheres

Connected by the corpus collosum

Five lobesFrontal, Parietal, Temporal, Occipital, Insular

Responsible for higher functionsPerception of sensory impulses, instigation of

voluntary movement, memory, thought, and reasoning

Cortex (outer surface) has elevated fields (gyri/gyrus) and grooves (sulci/sulcus)

5 LobesFrontal Lobe: voluntary control

of skeletal muscles; personality; intellectual process; verbal communication

Parietal Lobe: cutaneous and muscular sensations; understanding and utterance of speech

Temporal Lobe: interpretation of auditory sensations; auditory and visual memory

Occipital Lobe: integration of movements in focusing the eye; correlation of visual images with previous experiences; conscious seeing

Insular: memory; integration of other cerebral activities

DiencephalonThalamus: a relay center for all sensory impulses

to the cerebral cortex, except for smellHypothalamus: cardiovascular regulation, body

temperature regulation, water and electrolyte balance, gastrointestinal activity and hunger, sleeping and wakefulness, sexual response, emotions, and control of endocrine functions through stimulation of the anterior pituitary

Pituitary Gland: has endocrine functions

Mesencephalon (Midbrain)Short section of the brain stemContains:

Superior colliculi (visual reflexes) Inferior colliculi (auditory reflexes)Cerebral peduncles (coordinates reflexes)

MetencephalonPons

Relays impulses from one region of the brain to another

Many cranial nerves originate here Involved with regulating respiratory rate

CerebellumConsists of two hemispheres Involuntary coordination of skeletal-muscle

contractions within muscles, tendons, joints, and sensory organs

MylencephalonMedulla oblongata

Connects to spinal cordMakes up much of the brain stemControls autonomic functions (heart rate, contraction

of blood vessels, rate and depth of breathing)

CNS: The Spinal CordExtends through the vertebral canal of the

vertebral columnConducts nerve impulses to and from the brain

PNS: Cranial NervesInnervate structures of the head, neck, and trunkIdentified by Roman numerals in order of

appearance from front to back12 cranial nerves

PNS: Spinal Nerves31 pairs

8 cervical 12 thoracic 5 lumbar 5 sacral 1 cocccygeal

After exiting the vertebral column, they split, combine, and split again forming a plexus (there are 4) Cervical plexus Brachial plexus Lumbar plexus Sacral plexus

http://health.nih.gov/category/BrainandNervousSystem