1. The Central Nervous System
Unit 6:6

2. Objectives Identify the four parts of a neuron
Name the two divisions of the nervous system
Describe the function of each of the five parts of the brain
Explain three functions of the spinal cord
Name the three meninges
Describe the circulation and function of cerebrospinal fluid
Contrast the actions of the sympathetic and parasympathetic nervous system
Describe at least five diseases of the nervous system

3. Nervous System
Complex, highly organized system that coordinates all the activities of the body
Enables the body to respond and adapt to changes that occur inside and outside the body

4. Neuron Nerve cell (over 100 billion)
Basic structural unit of the nervous system
Extreme longevity of over 100 years

5. Neuron Components Cell body with a nucleus
NO centrioles, therefore cannot divide by mitosis
Nerve fibers called dentrites
Carry impulses toward the cell body from sensory receptors of other axons
Short, tapering diffusely branched (tree-like) fibers
Single nerve fiber called an axon
Carry impulses away from the cell body
Long, slender fiber
Distal tip of axon ends in synaptic knob or end plate
Many axons have a lipid (fat) covering called a myelin sheath
Increases the rate of impulse transmission and insulates and maintains the axon
Myelinated fibers: conduct at 300 mph
Unmyelinated fibers: conduct at 1 mph

6. Synapse The spaces between axons and dentrites (nerve fibers)
Impulses from one axon “jump” the synapse to get to the dentrite of another neuron which carries the impulse in the right directions

7. Neurotransmitters Special chemicals located at the end of each axon
They allow the nerve impulses to pass from one neuron to another

8. Nerves Many nerve fibers outside the brain and spinal cord
Afferent: sensory, nerves carry messages from all parts of the body to the brain and spinal cord
Efferent: motor, nerves carry messages from the brain and spinal cord to the muscles and organs
Associative: nerves carry both sensory and motor messages

9. Divisions Two Main Divisions
Central Nervous System (CNS)
Brain and spinal cord
Peripheral Nervous System (PNS)
Nerves
Autonomic Nervous System: controls involuntary body functions

10. Central Nervous System (CNS)
Brain: mass of 12 billion neurons and nerve tissue well protected by membranes and the cranial bones
Weights approximately 3 pounds

11. Components of the Brain
CNS
Cerebrum: largest and highest section (83%)
Outer part is arranged in folds called convolutions
It is separated into lobes (frontal, parietal, temporal, and occipital)
Responsible for reasoning, thought, memory, speech, sensation, sight, smell, hearing, and voluntary body movement
Cerebral Cortex: outer layer of gray matter; short and long term memory
Convolutions: elevated ridges/folds that increases gray area of brain
Sulci: shallower grooves
Fissures: deep grooves
Cerebellum: section in the back below the cerebrum
Responsible for muscle coordination, balance and posture, and muscle tone

12. Components of the Brain
CNS
Components of the Brain
Diencephalon: section located between the cerebrum and midbrain
Contains two structures
Thalamus: acts as a relay center for sensory incoming and directs impulses to the cerebrum for motor outgoing
Hypothalamus: regulates and controls the autonomic nervous system, temperature, appetite, water balance, sleep, and blood vessel constriction and dilation, GI control. It is also involved in emotions such as anger, fear, pleasure, pain, and affection.

13. Components of the Brain
CNS
BRAINSTEM (damage = coma)
Midbrain: section located below the cerebrum at the top of the brainstem
Responsible for impulses between brain parts and for certain eye and auditory reflexes
Pons: section located below the midbrain and in the brain stem
Responsible for conducting messages to other parts of the brain
Certain reflex actions like chewing, tasting, and saliva production, and assisting with breathing

14. Components of the Brain
CNS
Components of the Brain
Medulla Oblongata: the lowest part of the brain stem and connects with spinal cord
Regulates heartbeat, respiration, swallowing, coughing, and blood pressure
Spinal Cord: continues from the Medulla Oblongata and extends to the 1st and 2nd lumbar vertebrae
Surrounded and protected by vertebrae
Responsible for sensory (afferent) messages up and motor (efferent) messages down to the individual nerves

15. Components of the Brain
CNS
Components of the Brain
Meninges: three membranes with spaces between each that cover and protect the brain and spinal cord
Dura Mater: thick, tough, outer layer
Arachnoid membrane: middle layer that is delicate and weblike
Pia Mater: innermost membrane attached to the brain and spinal cord that contains blood vessels that nourish the nerve tissue

17. Components of the Brain
CNS
Ventricles: 4 hollow spaces that all connect, produce, and fill with cerebrospinal fluid (CSF)
The fluid bathes the skull, brain, and spinal cord and circulates continuously and serves as a shock absorber
Carries nutrients and helps removes waste and metabolic products
ml produced daily

18. The Peripheral Nervous System

19. Peripheral Nervous System (PNS)
Consists of the somatic and the autonomic nervous systems
Somatic: consists of 12 pairs of cranial nerves and their branches and 31 pairs of spinal nerves and their branches
Cranial Nerves: (12 pairs) responsible for special senses such as sight, hearing, taste, and smell
Spinal Nerves: (31 pairs) responsible for carrying messages to/from the spinal cord. 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 pair of coccygeal spinal nerves. Each one goes to a specific part of the body or it networks with others to form a plexus, which supplies sensation to a larger body segment

22. PNS
Autonomic: helps maintain a balance in the involuntary functions of the body and helps react in times of emergency.
Sympathetic: in times of emergency it prepares the body to act by HR, R, BP, and Digestive activity.
“Fight or Flight” response
Parasympathetic: after the emergency it counteracts the action
They both work together to maintain a balanced state called Homeostasis

23. Diseases and Abnormal Conditions
Cerebral Palsy: disturbance in voluntary muscle action caused by brain damage from lack of oxygen, birth injuries, or infection
Symptoms: exaggerated reflexes, tense muscles, contracture development, seizures, speech impairment, spasms, tremors, and in some cases, mental retardation
Treatment: no cure, but PT, OT, and speech therapy is available
Rx: muscle relaxants, anticonvulsive drugs, braces, orthopedic surgery

24. Cerebral Palsy

25. Diseases and Abnormal Conditions
Cerebrovascular Accident (CVA): also known as a stroke and occurs when the blood flow to the brain is impaired, resulting in a lack of oxygen and destruction to the brain
Etiology: can be caused by cerebral hemorrhage caused by hypertension, and aneurysm, or a weak blood vessel. Can also be caused by occlusion, or blockage, caused by atherosclerosis or a thrombus
Symptoms: loss of consciousness, weakness or paralysis on one side of the body (hemiplegia), dizziness, dysphagia (difficulty swallowing), visual disturbances, mental confusion, aphasia (speech impairment) and incontinence.
Treatment: immediate care in first 3 hours is crucial to preventing brain damage. Thrombolytic or “clot busting” drugs like TPA (Tissue Plasminogen Activator) or angioplasty. PT, OT, and speech therapy are the main forms of treatment

26. CVA (Stroke)

27. Diseases and Abnormal Conditions
Encephalitis: inflammation of the brain
Etiology: caused by a virus (mosquito), bacterium, or chemical agent
Symptoms: they vary but includes fever, extreme weakness, visual disturbances, headaches, vomiting, stiff neck and back, disorientation, seizures, and coma
Treatment: antiviral drugs, maintenance of fluid balance, antiseizure medication and monitoring respiratory and kidney function

28. ENCEPHALITIS

29. Diseases and Abnormal Conditions
Epilepsy: or seizure syndrome, is a brain disorder associated with abnormal electrical impulses in the neurons of the brain
Etiology: brain injury, birth trauma, tumors, toxins (lead and CO2), infections; most are idiopathic (spontaneous)
Symptoms: absence seizures occurring mostly in children are milder with a loss of consciousness lasting several seconds, but typically disappear by late adolescence. Generalized tonic-clonic are very severe seizures. Loss of consciousness for several minutes accompanied by convulsions, shaking, and thrashing movements, hypersalivation (foaming mouth), and loss of body functions
Treatment: anticonvulsant drugs are very effective

30. Diseases and Abnormal Conditions
Hydrocephalus: excessive accumulation of cerebrospinal fluid in the ventricles
Etiology: usually caused by a congenital defect, infection, or tumor that obstructs the flow of fluid out of the brain
Symptoms: abnormally enlarged head, prominent forehead, bugging eyes, irritability, distended scalp veins
Treatment: surgical implantation of a shunt (tube) between the ventricles and the veins, heart, or abdominal peritoneal cavity to provide drainage

31. Hydrocephalus

32. Diseases and Abnormal Conditions
Meningitis: inflammation of the meninges of the brain and/or spinal cord
Etiology: bacterium, virus, fungus, or toxins (lead or arsenic)
Symptoms: high fever, headaches, back and neck pain and stiffness, nausea and vomiting, delirium, convulsions, if untreated, coma and death
Treatment: antibiotics, anticonvulsants and/or medications for pain and cerebral edema

33. Meningitis

34. Diseases and Abnormal Conditions
Multiple Sclerosis (MS): chronic, progressive, disabling condition resulting from a degeneration of the myelin sheath in the CNS. It usually occurs between 20-40
Etiology: unknown
Symptoms: early Symptoms include visual disturbances, weakness, fatigue, poor coordination, and tingling and numbness. As it progresses, tremors, muscle spasticity, paralysis, speech impairment, emotional swings, and incontinence
Treatment: no cure, but PT, muscle relaxants, steroids, psychological counseling to maintain functional ability as long as possible.

35. Diseases and Abnormal Conditions
Neuralgia: nerve pain
Etiology: caused by inflammation, pressure, and toxins
Treatment: directed toward eliminating the cause of the pain

36. Multiple Sclerosis

37. Diseases and Abnormal Conditions
Paralysis:
Etiology: results from a brain or spinal cord injury that destroys neurons and results in loss of function and sensation below the level of injury
Hemiplegia: paralysis on one side of the body caused by a tumor, injury, or CVA
Paraplegia: paralysis on the lower extremities caused by a spinal cord injury
Quadriplegia: paralysis of arms, legs, and body below the injury site. There is no cure but billions of dollars are put into research

38. Paralysis

39. Diseases and Abnormal Conditions
Parkinson’s Disease: chronic, progressive condition involving degeneration of brain cells usually in persons over 50
Symptoms: tremors, stiffness, muscular rigidity, forward leaning position, shuffling gait, difficulty in stopping while walking, loss of facial expression, and behavioral changes
Treatment: no cure, but Levodopa is used to relieve the Symptoms. Surgery can be done to destroy selectively a small area of the brain and control involuntary movements. PT is used very frequently

40. Parkinson’s Disease
Stuttering
Cerebral Palsy

41. Diseases and Abnormal Conditions
Shingles: (Herpes Zoster) is an acute inflammation of nerve cells usually occurs in the thoracic area on one side of the body and follows the path of the affected nerves
Etiology: caused by the Herpes Virus, which also caused chicken pox
Symptoms: fluid-filled vesicles appear on the skin, accompanied by severe pain, redness, itching, fever, and abnormal skin sensations
Treatment: directed toward relieving pain and itching