Objectives for Nervous System Unit

Organization of the Nervous System  Define central nervous system and peripheral nervous system and list the major parts of each. ▸ Central nervous system (CNS) ◦ Brain ◦ Spinal cord ▸ Peripheral nervous system (PNS) ◦ Nerves outside the brain and spinal cord  Spinal nerves- 31 pairs  Cranial nerves- 12 pairs Nervous Tissue: Structure and Function  State the function of neurons and neuroglia. Neurons : transmit messages (nerve impulses) from one part of the body to another. Neuroglia 1. supporting cells act as phaogcytes 2. protect and myelinate 3. act as a selective barrier between the capillary blood supply and neurons  Describe the general structure of a neuron, and name its important anatomical regions.

◦ ◦ Major regions of neurons  Cell body —nucleus and metabolic center of the cell  Processes —fibers that extend from the cell body  List the two major functional properties of neurons. Irritability and conductivty  Classify neurons according to structure and function. Function . Sensory (afferent) neurons . Carry impulses from the sensory receptors to the CNS . Motor (efferent) neurons . Carry impulses from the central nervous system to viscera, muscles, or glands . Interneurons (association neurons) . Found in neural pathways in the central nervous system . Connect sensory and motor neurons Structure 1. Multipolar neuron have several processes extending from its cell body All motor neurons and interneurons! 2. Bipolar neurons—one axon and one dendrite Found in eyes and nose as receptor cells 3. Unipolar neurons—have a short single process leaving the cell body Sensory neurons found in PNS ganglia  Describe the events that lead to the generation of a nerve impulse and its conduction from one neuron to another.

 Define reflex arc and list its elements. • 1. Reflex—rapid, predictable, and involuntary response to a stimulus

Central Nervous System  Identify and indicate the functions of the major regions of the cerebral hemispheres, diencephalon, brain stem, and cerebellum on a human brain model or diagram. 1. Cerebral hemispheres (cerebrum) 2. Diencephalon 3. Brain stem Medulla oblongata- most important autonomic center of the brain & contains autonomic centers regulating heart rate, respiration, and other visceral activities.

4. Cerebellum- coordinates complex muscular movements

 Name the three meningeal layers and state their functions.

Protection of the Central Nervous System 1. Dura mater-outermost layer; tough fibrous connective tissue,

2. Arachnoid layer

3. Pia mater-innermost vascular layer covering the brain; follows every convolution

Discuss the formation and function of cerebrospinal fluid and the blood-brain barrier. Protection of the Central Nervous System cerebrospinal fluid  choroid plexus- structure that forms the cerebrospinal fluid  Forms a watery cushion to protect the brain blood-brain barrier  Includes the least permeable capillaries of the body  Excludes many potentially harmful substances

 List two important functions of the spinal cord. 1. Conduction pathway 2. Reflex center

 Describe spinal cord structure.

Peripheral Nervous System  Describe the general structure of a nerve.

 Identify the cranial nerves by number and by name, and list the major functions of each. I Olfactory nerve—sensory for smell II Optic nerve—sensory for vision III Oculomotor nerve—motor fibers to eye muscles IV Trochlear—motor fiber to eye muscles V Trigeminal nerve—sensory for the face; motor fibers to chewing muscles VI Abducens nerve—motor fibers to eye muscles VII Facial nerve—sensory for taste; motor fibers to the face VIII Vestibulocochlear nerve—sensory for balance and hearing IX Glossopharyngeal nerve—sensory for taste; motor fibers to the pharynx X Vagus nerves—sensory and motor fibers for pharynx, larynx, and viscera XI Accessory nerve—motor fibers to neck and upper back XII Hypoglossal nerve—motor fibers to tongue Describe the origin and fiber composition of

 (a) ventral and dorsal roots,

Ventral roots are motor dorsal roots are sensory. (b) the spinal nerve proper, : both motor and sensory

(c) ventral rami and dorsal rami. both: motor and sensory

 Discuss the distribution of the dorsal and ventral rami of spinal nerves.

Dorsal rami supply the posterior body trunk whereas the thicker ventral rami supply the rest of the body trunk and the limbs Name the four major nerve plexuses, give the major nerves of each, and describe their distribution. 1. Cervical: serves the diaphragm and muscles of shoulder and neck  phrenic nerve

2. Brachial: upper limbs • Axillary • Radial • Median • Musculocutaneous • Ulnar

• 3. Lumbar: serve the abdominal region and the anteromedial thigh. • Femoral • Obturator

4. Sacral : supply buttock, posterior thigh, and almost all leg and foot.  The sciatic nerve – largest nerve in the body; divides into common fibular nerve and tibial nerve.  Superior and Inferior Glutea  Identify the site of origin and explain the function of the sympathetic and parasympathetic divisions of the autonomic nervous system. Sympathetic Division = Fight/Flight

Originates from T1 through L2 Ganglia are at the sympathetic trunk (near the spinal cord) Short pre-ganglionic neuron and long post-ganglionic neuron transmit impulse from CNS to the effector Norepinephrine and epinephrine are neurotransmitters to the effector organs

Parasympathetic division = Take it Easy

Originates from the brain stem and S1 through S4 Terminal ganglia are at the effector organ Always uses acetylcholine as a neurotransmitter  Contrast the effect of the parasympathetic and sympathetic divisions on the following organs: heart, lungs, digestive system, blood vessels Organ Parasympathetic Sympathetic Heart Decrease heart rate Increase heart rate Lungs Contracts bronchiole (small air Dilates bronchioles. passage) smooth muscle. Digestive System Increases peristalsis and Decreases glandular and enzyme/mucus secretion. muscular activity.

Blood vessels constricts dilates