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Organs of the nervous system are divided into Central Nervous System (CNS) Central Nervous System (CNS) Peripheral Nervous System (PNS) Peripheral Nervous.

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Presentation on theme: "Organs of the nervous system are divided into Central Nervous System (CNS) Central Nervous System (CNS) Peripheral Nervous System (PNS) Peripheral Nervous."— Presentation transcript:


2 Organs of the nervous system are divided into Central Nervous System (CNS) Central Nervous System (CNS) Peripheral Nervous System (PNS) Peripheral Nervous System (PNS)

3  Central Nervous System  Brain  Spinal Cord  Peripheral Nervous system – cranial & spinal nerves & ganglia  Somatic (voluntary) – connect to skin and Skeletal Muscles  Autonomic (involuntary, homeostatic control) – cardiac muscle, smooth muscle, and glands  Sympathetic – dominates in times of stress; “fight or flight” syndrome (increases heart rate, blood pressure, breathing)  Parasympathetic – acts as counterbalance, conserves energy (decreases heart rate, blood pressure, breathing rate)


5  Brain – largest & most complex part of NS. Contains nerve centers associated with sensations. Issues motor commands & carries on higher mental functions: Fig. 8-9, 8-10


7  Extends from base of the cerebrum to the spinal cord  Consists of midbrain, pons, & medulla oblongata  Medulla oblongata – transmits all ascending & descending impulses, & contains several vital & nonvital relex centers (cardiac, respiratory, vasomotor)  Pons- transmits impulses between the cerebrum & other parts of the NS, and contains centers that help regulate the rate & depth of breathing  Midbrain – contains reflex centers associated with eye & head movements (visual & auditory impulses)

8  Thalamus – central relay station for incoming sensory impulses; emotions and alerting or arousal mechanisms  Hypothalamus – maintain homeostasis, regulation of body temp., water balance, sleep- cycle control, appetite & sexual arousal (**very important gland of the endocrine system)

9  Consists of two hemispheres that are connected by the vermis  Composed of white matter surrounded by a thing cortex of gray matter  Functions primarily as a reflex center in the co-ordination of skeletal muscle movements & the maintenance of equilibrium

10  Two hemisphere connected by the corpus callosum  Surface marked by convolutions (ridges) and gyri (grooves); 4 lobes each hemisphere – frontal, parietal, temporal, occipital  Composed of thin layer of gray matter near surface; white matter found deeper  Higher brain functions such as thought, reasoning, interpretations of sensory impulses, control of voluntary muscles, and storage of memory

11  Nerve column that extends from the brain into the vertebral canal. It terminates at the level between L 1 and L 2 ; fig. 8-11, 8- 12


13  Composed of 31 segments, each of which gives rise to a pair of spinal nerves  Characterized by two deep longitudinal grooves that divide it into right and left halves  Has a central core of gray matter that is surrounded by white matter  White matter is composed of bundles of myelinated nerve fibers

14  Provides a two way communications system between the brain & body parts outside the NS  Primary reflex center  Ascending tracts carry sensory impulses to the brain; descending tracts carry motor impulses to muscles and glands  Many of the fibers in the ascending and descending tracts cross over in the spinal cord or brain

15  Meninges – protective membrane covering brain & spinal cord; three layers; Fig  Dura mater – outer layer  Arachnoid – middle layer  Pia mater – inner layer  Cerebrospinal fluid occupies the space between the arachnoid & pia mater

16  Ventricles – interconnected cavities within the cerebral hemisphere & brain stem that are filled with cerebrospinal fluid: Fig. 8-14

17  Consists of cranial and spinal nerves that branch out from the brain and spinal cord to all body parts. Subdivided into somatic & autonomic portions.


19  12 pairs that connect the brain to parts in the head, neck, & trunk  Most cranial nerves are mixed (sensory & motor); some are pure sensory & other primarily motor  Some cranial nerve fibers are somatic & others are autonomic


21  31 pairs originate from the spinal cord  These mixed nerves provide a two way communication system between the spinal cord & parts in the arm, legs, neck, and trunk  Each nerve emerges by a dorsal and ventral root  Dorsal (posterior) root contains sensory fibers and is characterized by the presence of a dorsal root ganglion  Ventral root contains motor fibers

22  Each spinal nerve divides into several branches & then combines with other spinal nerves to form plexuses in which nerve fibers are sorted and recombined so that those fibers associated with a particular part reach it together.


24  Skeletal muscle & skin  Conduction of nerve impulse is all the way from the spinal cord or brain to the effector  No synapses  Fig (left side of picture)



27  Portion of nervous system that function without conscious effort  Concerned primarily with the regulation of visceral activities that aid in maintaining homeostasis  Fig (right side of picture)  Made up of motor neurons that conduct impulses to cardiac and smooth muscle tissue & glandular epithelial tissue

28  Conduction pathway is a 2 neuron relay – in the ganglia the impulses are integrated before passing out to effectors  ANS is divided into 2 divisions  Sympathetic  Parasympathetic


30  Prepares the body for stressful and emergency conditions “fight or flight syndrome”  Increase in heart rate, breathing, decrease in activities of digestive tract  Sympathetic preganglionic dendrites and cell bodies are located in the gray matter of the thoracic and upper lumbar segments of the spinal cord  Sympathetic preganglionic axons synapse with many postganglionic neurons in sympathetic ganglion & these postganglionic neurons frequently terminate in widely separated organs; therefore, sympathetic responses are usually widespread

31  Most active under ordinary conditions  Decreases heart rate and breathing  Opposite (antagonist) to sympathetic  Parasympathetic preganglionic dendrites and cell bodies are located in gray matter of brain stem and sacral segments of the spinal cord; axons extend some distance before terminating in parasympathetic ganglion  Parasympathetic postganglionic neurons have short axons that extend into nearby structures; therefore parasympathetic stimulation usually involved responses by only one organ

32  The different effects of the autonomic divisions are due to the different neurotransmitters released by the postganglionic fibers  There are various types of receptors present on the cell membranes and a cell’s response to neurotransmitters depends upon the number and type of receptors present in their membranes.  Fig. 8-20


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