The CNS, PNS, SNS, and ANS

 A control and communications system ◦ Consists of the brain, spinal cord, nerve cells, and nerve fibers that run throughout the body  Originates and coordinates physical reactions to the environment  Controls involuntary muscles and organs  Maintains homeostasis ◦ A balanced state within the body  C.S. 24

 Nerve cells are called neurons ◦ Star-shaped bodies with 2 long nerve fibers projecting from them ◦ Messages to the cell body are carried by nerve fibers called dendrites (part of the star) ◦ Messages that travel away from the cell body are carried by nerve fibers called axons (the tail)  The axon is covered by a myelin sheath for protection – deterioration of this sheath is called MS  The dendrite receives a message, transmits it to the cell body, and the cell body sends the message along to another neuron or to the organ that is to be affected (such as a muscle)

 The neurons and their fibers form a network that covers the entire inside of the body and all of the skin  The long fibers of neurons are arranged in bundles called nerves ◦ The fibers of neurons within the nerves don’t actually touch ◦ They meet at a place called a synapse, which is a space where an electrical impulse is transmitted from an axon to a dendrite

 Classified according to the direction in which they transmit impulses  Afferent neuron: sensory neurons – transmits impulses TO the brain and spinal cord from the sensory organs  Efferent neuron: motor neurons – transmits impulses AWAY from the brain and spinal cord or other nerve centers ◦ Transmit only to muscles and organs  Interneuron: transmits impulses from sensory to motor neurons ◦ Used in reflexes for defensive purposes  C.S. 25

 It is divided into categories depending upon function  Central Nervous System (CNS) ◦ Brain ◦ Spinal cord  Peripheral Nervous System (PNS) ◦ Somatic Nervous System (SNS) ◦ Autonomic Nervous System (ANS)  Sympathetic Nervous System  Parasympathetic Nervous System

 Made up of: ◦ The brain ◦ The spinal cord  Control center for the movement and actions of the entire body ◦ Messages come to the CNS from throughout the body, where they are interpreted ◦ the CNS then sends out reaction impulses

 The most complex and specialized organ in the body  3 areas – forebrain, midbrain, hindbrain  Divided into specialized sections ◦ Cerebrum  2 hemispheres – right and left  4 ventricles/lobes – frontal, parietal, temporal, and occipital ◦ Cerebellum ◦ Corpus Callosum ◦ Pons ◦ Medulla

 1. Frontal lobe of cerebrum (f)  2. Pituitary gland  3. Temporal lobe of cerebrum (f)  4. Pons (h)  5. Medulla oblongata  6. Parietal lobe of cerebrum (m)  7. Corpus callosum (f)  8. Occipital lobe of cerebrum (m)  9. Cerebellum (h)  10. Spinal cord

 Main part of the brain  Divided into hemispheres  Outer surface is called the cortex ◦ Wrinkled with deep furrows to increase the surface area of the brain  Consists of the forebrain and the midbrain  Has 4 lobes (aka ventricles)

 Frontal lobe ◦ Top, front regions of each of the cerebral hemispheres. ◦ Used for reasoning, emotions, judgment, and voluntary movement  Parietal lobe ◦ Middle lobe of each cerebral hemisphere between the frontal and occipital lobes ◦ Contains important sensory centers  Temporal lobe ◦ Region at the lower side of each cerebral hemisphere ◦ Contains centers of hearing and memory  Occipital lobe ◦ Region at the back of each cerebral hemisphere ◦ Contains the centers of vision and reading ability

 Part of the brain below the back of the cerebrum  Regulates balance, posture, movement, and muscle coordination

 A large bundle of nerve fibers that connect the left and right cerebral hemispheres  Allows for communication and coordination between the hemispheres  In the lateral section, it looks a bit like a "C" on its side

 The part of the brainstem that joins the hemispheres of the cerebellum and connects the cerebrum with the cerebellum  It is located just above the Medulla oblongata

 The lowest section of the brainstem (at the top end of the spinal cord)  It controls automatic functions including heartbeat, breathing, etc  C.S. 26

 Descends from the medulla oblongata down into the canal formed by the vertebrae  Made up of white (nerve tissue) and gray matter (same matter as brain tissue)  Has 2 functions: ◦ Serves as the sensory-motor mechanism for reflex actions ◦ Is the 2-way transmitter of impulses, reactions, and stimuli triggered by various internal and external conditions

 Surround the brain and spinal cord for protection  Dura mater – Outer layer  Arachnoid – Middle layer  Pia mater – Inner layer  Cerebrospinal fluid (CSF) – between pia mater and arachnoid (sub-arachnoid space)  Meningitis – an infection of the meninges ◦ Can be in any of the layers ◦ Can involve the CSF as well

 Made up of the nerves of the body that connect the CNS to the other parts of the body  Includes the cranial and spinal nerves

 Cranial nerves link the brain with sensory receptors and muscles  There are 12 cranial nerves  Designated by Roman numerals I-XII and names

 IOlfactory Smell  II Optic Vision  IIIOculomotorEye/eyeball movements  IVTrochlearEyeball movements  VTrigeminalChewing; facial sensation  VIAbducensEyeball movements  VIIFacialTaste; facial expression  VIIIAuditory/Vestibulocochlear Hearing; balance

 IXGlossopharangealTaste; swallowing; saliva secretion  XVagusSwallowing; voice; gag reflex; slowing of heartbeat (parasympathetic)  XISpinal accessoryMuscles of neck/shoulder  XIIHypoglossalTongue movements

 Mnemonic device: “On Old Olympus Towering Tops A Fin And German Viewed Some Hops” - OR – “Oh Oh Oh To Touch And Feel A Girl’s V……. So Happy”

 Olfactory (I) – Identify smells  Optic (II) – Eye chart; reading  Oculomotor, Trochlear, Abducens (III, IV, VI) – With head still, follow a finger up/down/left/right; pupillary response (III)  Trigeminal (V) – Bite down; Light touch on face  Facial (VII) – Smile, frown; Taste on tip of tongue

 Vestibulocochlear (VIII) – Check hearing; stand on one leg with eyes closed, then the other leg  Glossopharangeal and Vagus (IX, X) – Swallow; taste on back of tongue  Spinal Accessory (XI) – Resisted shrug  Hypoglossal (XII) – Stick out tongue and move it side to side

 Spinal nerves link the spinal cord with various structures  Conduct impulses between the spine and the parts of the body not supplied by the cranial nerves ◦ Transmit sensory info to the spinal cord through afferent neurons and transmit motor signals to muscles and organs through efferent neurons  Make sensation and movement possible  31 pairs ◦ One root of each pair goes to each side of the body

 31 pairs come from the spinal cord as follows: ◦ 8 cervical nerve roots ◦ 12 thoracic nerve roots ◦ 5 lumbar nerve roots ◦ 5 sacral nerve roots ◦ 1 coccygeal nerve root  Each nerve divides to form several branches called rami ◦ Dorsal rami – control muscles and skin of the back ◦ Ventral rami – innervate all structures of the limbs and torso

 Ventral rami and adjacent nerves form networks called plexuses that go to general areas ◦ Cervical plexus – serves neck, upper shoulders, and diaphragm ◦ Brachial plexus – serves upper limbs, neck, and shoulder muscles ◦ Lumbar plexus – serves abdominal area and part of the legs ◦ Sacral plexus – serves buttocks area and lower legs

 Dermatome – Area of skin supplied by a single spinal nerve root  Myotome – Specific muscle supplied by a single nerve root  Sclerotome – Area of bone supplied by a single nerve root  C.S. 27

 Subdivision of the PNS  Made up of motor nerves that control the voluntary actions of skeletal muscles

 Subdivision of the PNS  Made up of certain motor neurons of the PNS that conduct impulses from the spinal cord/brain stem to ◦ Cardiac muscle tissue ◦ Smooth muscle tissue ◦ Glandular epithelial tissue (tissue that forms glands)  Regulates the body’s automatic/involuntary functions such as heart rate, breathing, contractions of intestinal musculature, and secretions of hormones from the glands

 Responsible for “fight or flight” mechanism  Triggered by strong emotional situations (i.e. anger, fear, anxiety, hate, etc.) and by strenuous exercise  Increases heart rate, blood pressure, sweat excretion  Decreases digestion  Charges you up!

 Opposite of sympathetic nervous system  Decreases heart rate and blood pressure (Vagus nerve)  Increases digestion processes  Calms you down