1. The Nervous System Health Science 1

2. Organs and Divisions of the Nervous System
Central nervous system (CNS)—brain and spinal cord
Peripheral nervous system (PNS)—all the nerves; 12 pairs of cranial nerves extending from the brain and 31 pairs of spinal nerves extending out from spinal cord, divides into:
Somatic - carries messages between CNS and body
Autonomic- contains sympathetic and parasympathetic which work together to control involuntary body function

3. Division Flowchart

4. Nervous System Function (CNS)
It is the communication and coordination system in the body
It receives messages from stimuli all over the body
The brain interprets the message
The brain responds to the message and carries out an activity
The brain is also the seat of intellect and reasoning

5. Nervous System Function (PNS)
To control the autonomic or involuntary activities of the body
To act as the reflex center of the body

6. Cells of the Nervous System
Neurons (Nerve cell) – The basic structural unit of the nervous system. It transmits messages from one cell to the next
Dendrites: conduct impulses toward cell body of neuron, there are several dendrites
Cell body - The largest part, contain the nucleus and much of the cytoplasm, most the metabolic activity of the cell, including the generation of ATP (Adenine Triphosphate Compound that store energy and synthesis of Proteins).
Axon: conducts impulses away from cell body of neuron, only one axon
Axons have a lipid (fat) covering called Myelin Sheath which increases impulse transmission and insulates axon

7. Cells Cont.
Synapse: spaces between axon of one cell and dendrite of another cell where messages are transmitted. They never touch
Neurotransmitters – Special chemicals located at the end of each axon that allow the nerve impulses to pass from one neuron to another.

8. The Synapse (Neurotransmitters)
Names of neurotransmitters—
Acetylcholine
catecholamines (norepinephrine, dopamine, and serotonin)
endorphins
enkephalins
nitric oxide (NO), and other compounds

9. Transmission of Impulse (conduction) Through the Synapse with Neurotransmitters

10. Neurons classified according to function
Sensory (Afferent): carry messages (conduct impulses) from all body parts to the spinal cord and brain
Motor (Efferent): Carry messages (conduct impulses) from brain and spinal cord to muscles and glands
Interneurons (Associative): conduct impulses from sensory neurons to motor neurons

11. Cells of the Nervous System
Glia (neuroglia) – Insulate, support, and protect the neurons
All neurons possess the characteristics of being able to react when stimulated (irritability) and pass impulse to other neurons (conductivity)

12. Disorders of the Nervous System
Disorders of nervous tissue
Multiple sclerosis—characterized by myelin loss in central nerve fibers and resulting conduction impairments
Tumors
General name for nervous system tumors is neuroma
Most neuromas are gliomas, glial tumors
Multiple neurofibromatosis—characterized by numerous benign tumors

13. Disorders of the Nervous System Cont.
Tumors
General name for nervous system tumors is neuroma
Most neuromas are gliomas, glial tumors
Multiple neurofibromatosis—characterized by numerous benign tumors

14. Reflex Arcs
Nerve impulses are conducted from receptors to effectors over neuron pathways or reflex arcs; conduction by a reflex arc results in a reflex (that is, contraction by a muscle or secretion by a gland)

15. Nerve Impulses
Definition—self-propagating wave of electrical disturbance that travels along the surface of a neuron membrane
Mechanism
A stimulus triggers the opening of Na+ channels in the plasma membrane of the neuron
Inward movement of positive sodium ions leaves a slight excess of negative ions outside at a stimulated point; marks the beginning of a nerve impulse

16. Impulse Pathway

17. Signs of Parkinson’s Disease
Parkinson disease—characterized by abnormally low levels of dopamine in motor control areas of the brain

18. Central Nervous System
Divisions of the brain
Brainstem:
Consists of three parts of brain; named in ascending order, they are the medulla oblongata, pons, and midbrain
Function—gray matter in the brainstem functions as reflex centers (for example, for heartbeat, respirations, and blood vessel diameter); sensory tracts in the brainstem conduct impulses to the higher parts of the brain; motor tracts conduct from the higher parts of the brain to the spinal cord

19. Central Nervous System
Diencephalon:
Structure and function of the hypothalamus
Consists mainly of the posterior pituitary gland, pituitary stalk, and gray matter
Acts as the major center for controlling the ANS; therefore, helps control the functioning of most internal organs
Controls hormone secretion by anterior and posterior pituitary glands; therefore it indirectly helps control hormone secretion by most other endocrine glands
Contains centers for controlling appetite, wakefulness, pleasure, etc.

20. Central Nervous System
Structure and function of the Thalamus
Dumbbell-shaped mass of gray matter in each cerebral hemisphere
Relays sensory impulses to cerebral cortex sensory areas
In some way produces the emotions of pleasantness or unpleasantness associated with sensations

21. Central Nervous System
Cerebellum:
Second largest part of the human brain
Helps control muscle contractions to produce coordinated movements so that we can maintain balance, move smoothly, and sustain normal postures
Recent evidence shows the cerebellum may also have wider coordinating effects, assisting the cerebrum and other regions of the brain

22. Central Nervous System
Cerebrum:
Largest part of the human brain
Outer layer of gray matter is the cerebral cortex; made up of lobes; composed mainly of dendrites and cell bodies of neurons
Interior of the cerebrum composed mainly of white matter (that is nerve fibers arranged in bundles called tracts)
Functions of the cerebrum—mental processes of all types, including sensations, consciousness, memory, and voluntary control of movements

24. Central Nervous System
BRAIN DISORDERS
Destruction of brain tissue
Cerebrovascular accident (CVA)—hemorrhage from or cessation of blood flow through cerebral blood vessels; a “stroke”. Opposite side is usually affected. Thrombolytic must be given quickly to avoid further damage
Cerebral palsy—condition in which damage to motor control areas of the brain before, during, or shortly after birth causes paralysis (usually spastic) of one or more limbs

25. Central Nervous System Disorders
Dementia—syndrome that includes progressive loss of memory, shortened attention span, personality changes, reduced intellectual capacity, and motor control deficit
Alzheimer disease (AD)—brain disorder of the middle and late adult years characterized by dementia
Huntington disease (HD)—inherited disorder characterized by chorea (purposeless movement) progressing to severe dementia
HIV (also causes AIDS) can infect neurons and thus cause dementia

26. Central Nervous System
Seizure disorders
Definition
Seizure—sudden burst of abnormal neuron activity that results in temporary changes in brain function
Epilepsy—many forms, all characterized by recurring seizures

27. Central Nervous System
Spinal cord
Outer part is composed of white matter made up of many bundles of axons called tracts; interior composed of gray matter made up mainly of neuron dendrites and cell bodies
Functions as the center for all spinal cord reflexes; sensory tracts conduct impulses to the brain, and motor tracts conduct impulses from the brain

28. Central Nervous System
Coverings and fluid spaces of the brain and spinal cord
Coverings
Cranial bones and vertebrae
Cerebral and spinal meninges—the dura mater, arachnoid mater, and the pia mater
Fluid spaces—subarachnoid spaces of meninges, central canal inside cord, and ventricles in brain

29. Peripheral Nervous System
Cranial nerves (12)
attached to undersurface of the brain
Connect brain with the neck and structures in the thorax and abdomen
Spinal nerves (31)
Structure—contain dendrites of sensory neurons and axons of motor neurons
Function—conduct impulses necessary for sensations and voluntary movements

32. Peripheral Nervous System
Peripheral nerve disorders
Neuritis—general term referring to nerve inflammation
Sciatica is inflammation of the sciatic nerve that innervates the legs
Neuralgia, or muscle pain, often accompanies neuritis
Trigeminal neuralgia—recurring episodes of stabbing pain along one or more branches of the trigeminal (fifth cranial) nerve in the head
Bell’s palsy—paralysis of facial features resulting from damage to the facial (seventh cranial) nerve

33. Peripheral Nervous System
HERPES ZOSTER OR SHINGLES
Viral infection caused by chickenpox virus that has invaded the dorsal root ganglion and remained dormant until an episode of shingles
Usually affects a single dermatome, producing characteristic painful plaques or vesicles

34. Autonomic Nervous System
Autonomic nervous system—motor neurons that conduct impulses from the central nervous system to cardiac muscle, smooth muscle, and glandular epithelial tissue; regulates the body’s automatic or involuntary functions

35. Autonomic Nervous System
Composed of two divisions: the sympathetic system and the parasympathetic system

36. Autonomic Nervous System
Sympathetic nervous system
Function
Serves as the emergency or stress system, controlling visceral effectors during strenuous exercise and strong emotions (anger, fear, hate, or anxiety)
Group of changes induced by sympathetic control is called the fight-or-flight response

37. Autonomic Nervous System
Autonomic nervous system as a whole
Regulates the body’s automatic functions in ways that maintain or quickly restore homeostasis
They receive fibers from parasympathetic and sympathetic divisions and are influenced in opposite ways by the two divisions

38. Autonomic Nervous System
Parasympathetic nervous system
Function
Dominates control of many visceral effectors under normal, everyday conditions

39. Autonomic Nervous System
Autonomic nervous system as a whole
Regulates the body’s automatic functions in ways that maintain or quickly restore homeostasis
They receive fibers from parasympathetic and sympathetic divisions and are influenced in opposite ways by the two divisions

40. Disorders of Autonomic Nervous System
Stress-induced disease
Prolonged or excessive response to stress can disrupt normal functioning throughout the body
Examples of stress-induced conditions
Heart disease
Digestive problems
Reduced resistance to disease
Tumors
Neuroblastoma—highly malignant tumor of the sympathetic nervous system, primarily affecting young children