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Nervous System Allied Health Sciences I Instructor: Melissa Lewis.

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1 Nervous System Allied Health Sciences I Instructor: Melissa Lewis

2 Structure of the Brain: The brain is a highly developed, complex, and intricate mass of soft nervous tissue. Is composed of a billion neurons. Protected by the cranium, meninges and the cerebrospinal fluid.

3 Structure of the Brain cont… Meninges are made up of three membranous coverings and the cerebrospinal fluid. Three meninges are the dura mater (outside and lines skull on inside) arachnoid mater is the middle layer. The inner layer is the pia mater and this covers the brain surface itself and is composed of blood vessels held together by fine areolar connective tissue

4 Structure of the Brain cont… Cerebrospinal fluid is located between the arachnoid and the pia mater. CSF is produced within the ventricles of the brain and acts as a shock absorber and it is a source of nutrients to the brain. Brain is composed of white and gray matter.

5 Structure of the Brain cont… The outer cortex (cerebral cortex) is gray and it is the highest center of reasoning and intellect. The brain is divided into four major parts: the cerebrum, diencephalon, cerebellum, and brain stem.

6 Structure of the Brain cont… The brain is the storage site for our memory. The storage site depends on the type of memory. Ex: Learning how to swim or other exercise activity would be held in the visual area of the brain. The amount of memory we have on an event depends on the time and interest spent on it at the time. Ex: Usually traumatic events are easy to recall.

7 Structure of the Brain cont… There are four hollow spaces or cavities located in the brain and these are called cerebral ventricles. All of the ventricles are connected with each other and with the space under the arachniod membrane, called the subarachniod space. They are filled with fluid called cerebrospinal fluid

8 Structure of the Brain cont… This fluid circulates b/w the ventricles and through the subarachnoid space continually. It serves as a shock absorber to protect the brain and spinal cord. CSF carries nutrients to the brain and spinal cord and helps remove metabolic wastes. CSF is produced by the choroid plexuses which are networks of blood vessels of the pia mater.

9 Cerebrum: Cerebrum is the largest and highest section of the brain. There is a layer of gray matter called the cerebral cortex. It is divided into a R and L Hemisphere by the longitudinal fissure. The outer part is arranged in folds called convolutions and separated into two lobes which are named from the skull bones that surround them, Frontal, Parietal, Temporal, and Occipital.

10 Cerebrum Cont… The cerebrum is responsible for reasoning, thought, memory, speaking, sensation, sight, hearing, and voluntary movement. Frontal lobe controls the motor functions of humans. Cells in the right hemisphere activate voluntary movements that occur in the left side of the body and vice versa.

11 Cerebrum Cont… Broca’s area is located anterior to the central fissure usually in the left hemisphere and is associated with the ability to speak. If damaged one may know what to say but is not able to. The area that allows us to recognize works and interpret their meaning, spoken or read, is located at the junction of the temporal, parietal, and occipital lobes.

12 Cerebrum Cont… Parietal lobe compromises the sensory (somesthetic) area. It is found behind the fissure of Rolando in front of the parietal lobe. Occipital lobe houses the visual area, controlling eyesight Temporal lobe the upper part of the temporal lobe contains the auditory area and the anterior part of the lobe is occupied by the olfactory (Smell) area The cerebral cortex also controls conscious thought, judgment, memory, reasoning, and will power. Thus human intelligence.

13 Cerebellum: Cerebellum is the section below the back of the cerebrum and behind the pons. The cerebellum consists of gray matter on the outside and white matter on the inside. It is responsible for coordination of muscles, balance and posture, and muscle tone. Allows each muscle to contract at the right time, with the right strength, and for the right amount of time so that the overall movement is smooth and flowing.

14 Cerebellum cont… The cerebellum is important when speaking, walking, or writing. If injured motor impairment will result.

15 Diencephalon: Diencephalon is located b/w the cerebrum and midbrain Diencephalon contains Thalamus (Directs sensory impulses) and hypothalamus (Helps store and retain short term memory)

16 Diencephalon Cont… The hypothalamus has nine functions: –Regulates autonomic nervous system –Controls BP –Helps maintain normal body temp. –Assists in regulating the amount of food we eat –Certain cells that respond to osmotic pressure of the blood located within the hypothalamus –Contracts the uterus during labor (oxytocin) –Increases intestinal peristalsis and secretion from intestinal glands –Display of emotions –Helps keep us awake when necessary

17 Brain Stem: Brain stem is made up of three parts: –Midbrain-located below cerebrum at the top of the brain stem. It contains the nuclei for reflex centers involved with vision and hearing. –Pons-located in front of the cerebellum, b/w the midbrain and the medulla oblongata. Serves as a two-way conductive pathway for nerve impulses b/w the cerebrum, cerebellum, and other areas of the nervous system –Medulla oblongata- connects w/ spinal cord. Contains nuclei for vital functions such as the heart rate, the rate and depth of respiration.

18 Spinal Cord: Begins at the foramen magnum of the occipital bone and continues to the second lumbar vertebrae. It functions as a reflex center and as a conduction pathway to and from the brain. Carries sensory (afferent) messages up to the brain and motor (efferent) messages from the brain to the nerves, that go up to muscles and glands

19 Nerves: Composed of bundles of nerve fibers enclosed by connective tissue. If these fibers carry impulses from the sense organs to the brain or spinal cord its called a sensory or afferent nerve. If these fibers carry impulses from the brain or spinal cord to muscles or glands its know as a motor or efferent nerve If these fibers are both sensory and motor it is referred to as a mixed nerve

20 Nerves Cont… The peripheral nervous system includes all the nerves of the body and ganglia (groups of body cells) The autonomic nervous system is a specialized part of the PNS that controls involuntary activities of vital organs So, the function of the PNS is to control automatic or involuntary activities of the body and acts as a reflex center of the body

21 Nerves Cont… Cranial Nerves are twelve pair that begins in the brain. They are designated by name and number; the name may give a clue to its function –Make table with cranial nerves I-XII Spinal Nerves originate at the spinal cord and go through openings in the vertebrae. There are thirty-one pairs of spinal nerves. All spinal nerves are Mixed nerves.

22 The Autonomic Nervous System Autonomic Nervous System- This is an important of the peripheral nervous system. It helps maintain balance in the involuntary functions of the body, but allows the body to react in times of emergency. The ANS includes nerves, ganglia and plexuses that carry impulses to all smooth muscle, secretory glands, and heart muscle. It regulates the activities of the visceral organs. The activities of these organs are usually automatic and not subject to conscious control.

23 The Autonomic Nervous System The ANS is divided into two division: –The parasympathetic nervous system and the sympathetic nervous system.Usually these two systems work together. They maintain balanced state or homeostasis in the body and control involuntary body functions at proper rate.

24 The Sympathetic System It consists of two cords that begin at the base of the brain and proceed down both sides of the spinal column. They are made up of nerve fibers and ganglia of nerve cell bodies. They sympathetic nerves extend to all the vital internal organs, including the liver and pancreas, heart, stomach, intestines, blood vessels, the iris of the eye, sweat glands and the bladder. It is often referred to as the “fight or flight system”. It sends a message to the adrenal medulla which secretes its hormones to prepare our body for this action.

25 The Parasympathetic System It is composed of two important active nerves: the vagus and the pelvic nerves. The vagus nerve extends from the medulla and goes down the neck and branches out over the chest and neck. The pelvic nerve begins at the spinal cord and branches out over the hip to the lower organs of the body. Both of these systems are influenced by emotion. They are antagonistic of each other and therefore maintain perfect balance.

26 Nerves cont… The simplest type of nervous response is reflex. This is an unconscious act and involuntary. Examples are secretion of the salvia when you smell food, blinking of an eye if a particle enters, removing your hand from something hot as well as the movements of the heart, stomach, and intestines. Every reflex is preceded by a stimulus. Any change in the environment is called a stimulus. Example are sounds waves, light waves and heat energy and odors. Receptors pick up the stimuli. A simple reflex is one in which there is only a sensory nerve and a motor nerve involved. A classic example is the “knee-jerk” reflex. When the knee is tapped with a percussion hammer the leg extends. The muscles that respond are called effectors.

27 Draw & Label Nerve Cell to Display Axon (only one per neuron) –Carry message away from cell body Dendrites (multiple per neuron) –Carry message to cell body Myelin sheath –Insulates axon (makes impulse move faster) Synapse –Space between nerve cells (where message jumps from one neuron to another) Stimuli, body recognizes change/stimuli, message sent to brain, brain interprets message, brain tells body how to respond to stimuli

28 Common Nervous System Disorders

29 Cerebral Vascular Accident What is CVA? –Stroke or CVA –Interruption of blood and O2 to brain –Tissue death –Third leading cause of death in the USA Risk Factors –Smoking –Hypertension –Heart disease –Family history Causes of CVA –90% caused by blood clots –Clots lodge in carotid arteries, blocking the flow of blood to the brain –10% caused by ruptured blood vessels in the brain

30 Symptoms –Hemiplegia on opposite side of the body –Sudden, severe headache –Dizziness –Sudden loss of vision in one eye –Aphasia –Dysphasia –Coma –Possible death Treatment –Get to the hospital immediately!! –CT done to determine etiology –If a clot, treatment aimed at dissolving clot Cerebral Vascular Accident Cont..

31 Prevention –If TIAs- one aspirin a day –Stop smoking –Exercise and lose weight –Control hypertension

32 Meningitis Inflammation of the linings of the brain and spinal cord. The cause may be bacterial or viral. Symptoms include: headache, fever, and stiff neck (nuchal rigidity). It can lead to paralysis,coma,and death. Antibiotics are the treatment when the cause is bacterial. As a precaution until the physician has diagnosed the cause, antibiotics are usually given up from due to the seriousness of this disorder. Positive Kernig’s and Brudinski’s signs also occur in meningitis patients.

33 Paralysis Loss of power of motion or sensation. Causes can be trauma, disease or poisoning. –Hemiplegia- paralysis of one side of the body. The kinds are cerebral hemiplegia, facial hemiplegia and spastic hemiplegia –Paraplegia- this is the paralysis characterized by a motor or sensory loss in the lower limbs and trunk. –Quadriplegia- this is a paralysis of the arms, legs, and trunk of the body. Example: Superman

34 Epilepsy A seizure disorder of the brain, characterized by a recurring and excessive discharge from neurons. Epilepsy is due to the result of spontaneous, uncontrolled, cycles of electrical activity in the neurons of the brain. One portion of the brain stimulates another which sets off a cycle of activity that accelerates and runs its course until the neurons become fatigued. A Grand Mal seizure is the most severe seizure and occurs less frequently than the petit mal which is a milder seizure. In petit mal, some victims seem to be staring or daydreaming. Medications used to control seizures are referred to as anticonvulsants. Examples are Phenobarbital, Dilantin, and Tegretol.

35 Nervous System Disorders Cerebral Palsy- a disturbance in voluntary muscular action due to brain damage. Definite causes are unknown. Poliomyelitis- a disease of the nerve pathways of the spinal cord which cause paralysis. Hydrocephalus- a condition in which there is an increased volume of cerebrospinal fluid within ventricles of the brain. Parkinson’s Disease- is characterized by tremors, a shuffling gait, pill-rolling (movement of the thumb and index finger) and muscular rigidity.

36 Nervous System Disorders cont… Multiple Sclerosis (MS)- a chronic inflammatory disease of the central nervous system in which immune cells attack the myelin sheath of nerve cell axons. The myelin sheaths are destroyed, leaving scar tissue on the nerve cells. Diagnosis is made by the signs and symptoms. Dementia- a general term that includes specific disorders such as Alzheimer’s disease, defined as a loss in at least two areas of complex behavior, such as language, memory, visual and spatial abilities, or judgment that significantly interferes with a person’s daily life.

37 Nervous System Disorders cont… Alzheimer’s Disease- a progressive disease in which the initial symptom is usually a problem with remembering recently learned information. –The nerve endings in the cerebral cortex degenerate and block the signals that pass b/w nerve cells. –It’s a form of dementia. The nerve endings form a plaque appearance. The next stage is the nerve cells develop a build-up of abnormal fibers and this creates neurofibrillary tangles, like a group of telephone lines getting tangled. This cause is unknown.

38 Nervous System Disorders cont… There are three stages: –The first stage may last 2-4 years and involves confusion, short-term memory loss, anxiety, and poor judgment. –The second stage may last 2-10 years and there is an increase in memory loss, difficulty in recognizing people, motor problems, logic problems, loss of social skills. –The third stage may last from 1-3 years and involves the inability to recognize oneself, weight loss, seizures, mood swings, and aphasia (loss of speech).

39 Nervous System Disorders cont… Brain tumors may develop in any area of the brain and the symptoms depend on which area of the brain is affected. Hematoma- a localized mass of blood collection and may occur in the spaces b/w the meninges. Can be caused by a blow to the head such as a subdural hematoma which would be located b/w the dura mater and arachnoid layer.

40 Disorders of the Peripheral Nervous System Neuritis- an inflammation of a nerve or a nerve trunk. Causes of neuritis may be infectious, chemical, or occur because of others conditions such as chronic alcoholism. Treatment includes determining the cause to eliminate the symptoms. The pain can be treated with analgesics. Sciatica- a form of neuritis that affects the sciatic nerve. The pain radiates through the buttock and behind the knee down to the foot. The person may have difficulty walking. Treatment includes traction, physiotherapy, exercises and possible surgery to alleviate the symptoms.

41 Disorders of the Peripheral Nervous System cont… Neuralgia- a sudden severe, sharp, stabbing pain along the pathway of a nerve. Trigeminal neuralgia- involves the fifth cranial (trigeminal). Cause is unknown and the onset is very rapid. The pain is severe. Treatment may be analgesics or partial removal of the fifth cranial nerve. Bell’s Palsy- a condition which involves the seventh cranial nerve (facial). The patient seems to have had a stroke on one side of the face. It only affects application and exercises such as whistling to prevent atrophy. Symptoms usually disappear within a few weeks.

42 Disorders of the Peripheral Nervous System cont… Shingles or herpes zoster- an acute viral nerve infection. It is usually one-sided usually on the intercostals area. They are vesicular eruptions along the route of the inflamed nerve. It is caused by the same virus that causes chickenpox in children. Treatment is analgesics and something for the itching (pruritis). Carpal Tunnel syndrome- the condition that affects the median nerve and the flexor tendons that attach to the bones of the wrist. It develops because of repetitive movement of the wrist. Treatment consists of immobilizing the wrist joint and/or surgery.

43 The End!!!

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