The Nervous System

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THE NERVOUS SYSTEM PHYSIOLOGY AND ANATOMY OF BODY CONTROLING SYSTEM Don’t get nervous about the nervous system!! 1 Mahmudul hasan sakib Department of pharmacy University of Science and Technology Chittagong (USTC)

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Somatic NS comprises: cranial nerves(12 pairs) and spinal nerves(31 pairs) 2

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Functions of nervous system: Sensory function Motor functions: involuntary(reflex) & voluntary functions Associated functions: idea, memory, intelligence, etc. Motor components of NS: Spinal cord Reticular substance of medulla, pons & mesencephalon Basal ganglia Cerebellum Motor cortex Sensory components of NS: Spinal cord at all levels Reticular substance of the medulla, pons & mesencephalon The cerebellum The thalamus Areas of the cerebral cortex Motor unit: A motor nerve together with the group of muscle fiber which innervates is called motor unit. 3

Structure and mechanism of a neuron (nervous cell):

Structure and mechanism of a neuron (nervous cell) The human body is made up of trillions of cells. Cells of the nervous system, called nerve cells or neurons, are specialized for reception, conduction, integration & transmission of "messages" through an electrochemical process. The human brain has about 100 billion neurons that carry out the nerve impulses through a process called action potential . 4

Structure and mechanism of a neuron (nervous cell):

Neurons are similar to other cells in the body because: 1. Neurons are surrounded by a cell membrane. 2. Neurons have a nucleus that contains genes. 3. Neurons contain cytoplasm, mitochondria and other “organelles” 4. Neurons carry out basic cellular processes such as protein synthesis and energy production. However, neurons differ from other cells in the body because: 1. Neurons have specialized extensions called dendrites and axons. Dendrites bring information to the cell body and axons take information away from the cell body. 2. Neurons communicate with each other through an electrochemical process. 3. Neurons contain some specialized structures (for example, synapses) and chemicals (for example, neurotransmitters). Structure and mechanism of a neuron (nervous cell) 5

Structure and mechanism of a neuron (nervous cell):

Structure and mechanism of a neuron (nervous cell) Neurons are the oldest and longest cells in the body! You have many of the same neurons for your whole life. Although other cells die and are replaced, many neurons are never replaced when they die. In fact, you have fewer neurons when you are old compared to when you are young. On the other hand, data published in November 1998 show that in one area of the brain (the hippocampus), new neurons can grow in adult humans. Neurons can be quite large - in some neurons, such as corticospinal neurons (from motor cortex to spinal cord) or primary afferent neurons (neurons that extend from the skin into the spinal cord and up to the brain stem), can be several feet long! 6

Structure and mechanism of a neuron (nervous cell):

A single neuron consist of: CELL BODY : is the metabolic center of the neuron, contains the Nucleus and Mitochondrion. DENDRITES : convey incoming messages to the cell body. AXON HILLOCK : a cone like region from where an axon arises. AXONS : generates nerve impulses and topically conduct them away from the cell body." A nerve is a group of axons”. PRESYNAPTIC TERMINAL: The swollen, distal end of an axon; contains a neurotransmitter substance within synaptic vesicles. Also called synaptic ending or synaptic bouton. Structure and mechanism of a neuron (nervous cell) 7

Structure and mechanism of a neuron (nervous cell):

Axons Take information away from the cell body Nissle granules are absent Smooth Surface Generally only 1 axon per cell No ribosome Can have myelin Branch further from the cell body Dendrites Bring information to the cell body Nissle granules are present Rough Surface (dendrite spines) Usually many dendrites per cell Have ribosomes No myelin insulation Branch near the cell body Structure and mechanism of a neuron (nervous cell) 8

Structure and mechanism of a neuron (nervous cell):

Nucleus - contains genetic material (chromosomes) including information for cell development and synthesis of proteins necessary for cell maintenance and survival. Covered by a membrane. Nucleolus - produces ribosomes necessary for translation of genetic information into proteins Nissl Bodies - groups of ribosomes used for protein synthesis. Endoplasmic reticulum (ER) - system of tubes for transport of materials within cytoplasm. Can have ribosomes (rough ER) or no ribosomes (smooth ER). With ribosomes, the ER is important for protein synthesis. Golgi Apparatus - membrane-bound structure important in packaging peptides and proteins (including neurotransmitters) into vesicles. Microfilaments/Neurotubules - system of transport for materials within a neuron and may be used for structural support. Mitochondria - produce energy to fuel cellular activities. Structure and mechanism of a neuron (nervous cell) What is inside of a neuron? A neuron has many of the same "organelles," such as mitochondria, cytoplasm and a nucleus, as other cells in the body. Components of a neuron 9

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Functional parts of a neuron: Receptor or dendritic zone: Here, multiple local potential changes generated by the synaptic connections are integrated. Action potential generator zone: A site where propagated action potentials are generated.e.g. 1. The initial segments in spinal motor neurons 2. The initial node of Ranvier in cutaneous sensory neurons Axon: It transmits propagated impulse to the nerve endings Nerve endings: Here, action potential cause release of synaptic transmitters. Name of the motor neurons: Motor neurons in the cerebral & cerebellar cortex Upper motor neurons(UMN): These are the neurons in the descending motor tract.e.g.pyramidal cell, purkinje fibres Lower motor neurons(LMN): e.g. anterior horn cell, γ (gamma) – motor neuron, cranial motor nerve Preganglionic & postganglionic motor neurons of the sympathetic and parasympathetic nervous system. 10

1. One way to classify neurons is by the number of extensions that extend from the neuron's cell body (soma):

1. One way to classify neurons is by the number of extensions that extend from the neuron's cell body (soma) Bipolar neurons have two processes extending from the cell body (examples: retinal cells, olfactory epithelium cells). Pseudounipolar cells (example: dorsal root ganglion cells). Actually, these cells have 2 axons rather than an axon and dendrite. One axon extends centrally toward the spinal cord, the other axon extends toward the skin or muscle. Multipolar neurons have many processes that extend from the cell body. However, each neuron has only one axon (examples: spinal motor neurons, pyramidal neurons, Purkinje cells). Types of neurons 11

2. Neurons can also be classified by the direction that they send information::

2. Neurons can also be classified by the direction that they send information: Sensory (or afferent) neurons: Send information from sensory receptors (e.g., in skin, eyes, nose, tongue, ears) TOWARD the central nervous system. Motor (or efferent) neurons: Send information AWAY from the central nervous system to muscles or glands. Interneurons: Send information between sensory neurons and motor neurons. Most interneurons are located in the central nervous system. 3. According to position: Upper motor neuron: The neurons in the cerebral cortex & brainstem, the axons of which form the descending motor tract. Lower motor neuron: The spinal & cranial motor neurons that leave the CNS and directly innervate the muscles. Types of neurons 12

Synapse :

Synapse Definition: It is the junction and functional continuity between two neurons where one neuron ends & the other begins. Components of synapse : 1) Presynaptic membrane; also called synaptic / terminal knob. Axoplasm of presynaptic membrane contains: neurotransmitter vesicles, mitochondria lysosomes. 2) Synaptic cleft: It is a space between presynaptic & post synaptic membrane. It contains neurotransmitter degrading enzyme (e.g. acetylcholine esterase), polysaccharides. 3) Post synaptic membrane: It is the part of post synaptic neuron or other effector cells (i.e. muscle & gland cells) on which presynaptic neuron ends. Functions of synapse: a) Transmission of nerve impulse from neuron to neuron b) Integration of nerve impulse c) Formation of reflex arc d) Modulation of neural activity 13

Neurotransmitters :

Neurotransmitters Definition: These are highly active chemical agents released at the nerve endings & transmits impulses from nerve to nerve or nerve to effector tissues. Types: Please turn over pg. no. 560,565 of “shakhawat” for more Excitatory Inhibitory Both excitatory & inhibitory Acetylcholine Adrenaline Nor adrenalin Glutamate Dopamine Taurine Alanine Glycine Gamma amino butyric acid (GABA) Serotonin Substance P 5 - HT Histamine Prostaglandin Nor epinephrine 14

Mechanism of impulse transmission:

Mechanism of impulse transmission Presynaptic events : Arrival of the impulse at presynaptic nerve terminal ↓ Depolarization of the nerve terminal by the action potential (impulse) ↓ Entry of Ca 2+ through voltage gated Ca 2+ channel ↓ Ca 2+ causes fusion of synaptic vesicles of the presynaptic membrane with the release of neurotransmitter into synaptic cleft ↓ Diffusion of neurotransmitter across the synaptic cleft Post synaptic membrane : Binding of neurotransmitter with receptors ↓ Activation of receptor which opens Na + channel ↓ Depolarization(by Na + influx) or hyperpolarization ( Cl - influx & K + efflux) of the post synaptic membrane either produce or not produce impulse respectively Then, dissociation of the neurotransmitter from the receptor→ removal of neurotransmitter from synaptic cleft via enzyme degradation(reuptake). 15

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Excitatory postsynaptic potential(EPSP): When an excitatory impulse excites a motor neuron, depolarization of the post synaptic membrane occurs, which is called EPSP. Inhibitory post synaptic potential(IPSP): When a motor neuron receives an inhibitory impulse, hyperpolarization of the postsynaptic membrane occurs, which is called IPSP. Role of Ca 2+ in neurotransmission: Ca 2+ , from the synaptic cleft, enters the axon terminal of the motor neuron and causes release of neurotransmitter from that motor neuron. Neuromuscular junction: The junction between muscle fiber & motor nerve ending is called neuromuscular junction. It has 3 parts: 1. Axon terminal (presynaptic element) 2. Synaptic cleft 3. Motor endplate (post synaptic element) Receptor: These are the specialized tissues that can be stimulated by any changes of both external or internal environment. Sensory receptor is a specialized cell or may be a part of a neuron that generates action potentials in neurons. (see page no. 567 from “shakhawat”) 17

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Properties of receptors: a. Excitability b. Specificity c. Adaptation: frequency of discharge from a receptor gradually decline d. Doctrine of specific nerve energies e. Projection Reflex: Involuntary motor response due to any sensory stimulus is called reflex action.e.g.knee jerk, ankle jerk, vomiting, pupillary reflex. Properties of reflex: Summation, synaptic delay, irradiation, occlusion, recruitment, facilitation, fatigue, rebound activity, inhibition. Reflex arc: Complete pathway of a reflex action is called reflex arc. Reflex arc consists of: afferent limb, efferent limb, center & synapse. Classification: Monosynaptic reflex arc (2 neurons & one synapse) Disynaptic reflex arc (3 neurons & 2 synapses) Polysynaptic reflex arc (more than 2 synapses) 18

Nerve fiber:

Nerve fiber Nerve fiber is the name given to an axon or a dendrite of a nerve cell(neuron). Classification of nerve fibers: Histological: 1) Myelinated fiber(having myelin sheath) 2) Unmyelinated fiber Physiological: 1) General – type A, type B, type C 2) Sensory Functional: 1) Motor fiber (somatic, visceral) 2) Sensory fiber Chemical: 1) Cholinergic 2) Adrenergic Properties of nerve fibers: Excitability Conductivity All or none law Refractory period summation 19

Degeneration of neuron:

Degeneration of neuron Definition: The total destructive changes that happen to a nerve fiber after its injury or complete transaction is called degeneration. Types: It is of 2 types: 1) Retrograde degeneration : The degeneration that affect the cell body and proximal part of the cut fiber. 2) Wallerian degeneration : The process of changes occurring in the axon distal of the lesion including its termination. Causes: a) Transection of nerve fiber b) Crushing of nerve fiber c) Local injection of toxic substance d) Interference with blood supply Regeneration of nerve cell: It occurs outside the CNS due to presence of neurolemma & Schwann cell multiplication by mitosis. 20

Neuroanatomy and an introduction to the Nervous system:

Neuroanatomy and an introduction to the Nervous system Neuro-anatomy is the structure of the nervous system. To learn how the nervous system functions, you must learn how the nervous system is put together. The nervous system maintains body homeostasis with electrical signals; provides for sensation, higher mental functions, and emotional response; and activates muscles and glands. The nervous system is the master controlling and communicating system of the body. Every thought, action and emotion reflects its activity. Its signaling device, or means of communicating with body cells, is electrical impulses, which are rapid and specific and cause almost immediate responses. 21

Neuroanatomy and an introduction to the Nervous system:

To carry out its normal role, the nervous system has three over lapping functions: 1) Much like a sentry , it uses its millions of sensory receptors to monitor changes occurring both inside and outside the body. These changes are called stimuli , and the gathered information is called sensory input . 2) It processes and interprets the sensory input and makes decisions about what should be done at each moment – a process called integration . 3) It then effects a response by activating muscles or glands ( effctors ) via motor output . Neuroanatomy and an introduction to the Nervous system 22

Structural classification of the nervous system:

Structural classification of the nervous system First: The Central Nervous System (CNS) Second: The Peripheral Nervous System (PNS) The nervous system can be divided into several connected systems that function together. Let's take the simple division: The Nervous System is divided into: 23

The Central Nervous System:

The Central Nervous System The central nervous system is divided into two parts: the brain and the spinal cord . The average adult human brain weighs 1.3 to 1.4 kg (approximately 3 pounds). The brain contains about 100 billion nerve cells (neurons) and trillions of "support cells" called “ glia” . The spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 grams. The vertebral column, the collection of bones (back bone) that houses the spinal cord , is about 70 cm long. Therefore, the spinal cord is much shorter than the vertebral column. The Central Nervous System (Brain and Spinal Cord) 24

The Peripheral Nervous System:

The Peripheral Nervous System The peripheral nervous system is divided into two major parts: the somatic nervous system and the autonomic nervous system. 2. Autonomic Nervous System: The autonomic nervous system is divided into three parts: the sympathetic nervous system , the parasympathetic nervous system and the enteric nervous system . The autonomic nervous system controls smooth muscle of the viscera (internal organs) and glands. The preganglionic neuron is located in either the brain or the spinal cord. This preganglionic neuron projects to an autonomic ganglion. The postganglionic neuron then projects to the target organ . Notice that the somatic nervous system has only one neuron between the central nervous system and the target organ while the autonomic nervous system uses two neurons. The enteric nervous system is a third division of the autonomic nervous system that you do not hear much about. The enteric nervous system is a meshwork of nerve fibers that innervate the viscera (gastrointestinal tract, pancreas, gall bladder). 1. Somatic Nervous System: The somatic nervous system consists of peripheral nerve fibers that send sensory information to the central nervous system AND motor nerve fibers that project to skeletal muscle. The picture on the left shows the somatic motor system. The cell body is located in either the brain or spinal cord and projects directly to a skeletal muscle . 25

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In the Peripheral Nervous System, neurons can be functionally divided in 3 ways: 26

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Some differences between the Peripheral Nervous System (PNS) and the Central Nervous System (CNS) In the CNS, collections of neurons are called nuclei. In the PNS, collections of neurons are called ganglia. In the CNS, collections of axons are called tracts. In the PNS, collections of axons are called nerves 27

The Brain…:

The Brain… 28

The Brain…:

The Brain… Although some people may think that the brain is like a bowl of jell-O, the brain is NOT a bowl of jell-O. Unlike a bowl of jell-O, the brain is not a uniform material. Rather, the brain is made up of many different areas, each having a particular structure and function . 29

The skull: home of the brain:

The skull: home of the brain Your brain is protected by several bones. There are eight bones that surround your brain: one frontal bone ; two parietal bones , two temporal bones , one occipital bone , one sphenoid bone and one ethmoid bone . These eight bones make up the cranium. Another 14 bones in the face make up the entire skull. There are also 3 small bones in each ear. Also protecting your brain are 3 layers of tissue called the meninges. A few of the bones have been colored in the diagram to the right. 30

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There is a large opening, called the foramen magnum, located in the back of the occipital bone. This is where the medulla ends and projects out of the skull. Smaller holes in the skull, called foramina, allow nerves and blood vessels to enter and leave the cranium. The picture in the bottom shows the base of the skull. The places in the skull where the bones come together are called sutures. These sutures are flexible in young children, but become fixed as you age. 31

Divisions of the Brain:

Divisions of the Brain 32

The subdivisions of the brain:

The subdivisions of the brain Telencephalon Diencephalon Mesencephalon (Midbrain) Metencephalon Myelencephalon 33

Lobes of the brain:

Lobes of the brain The average human brain weighs about 1,400 grams (3 lb). When the brain is removed from the skull, it looks a bit like a large pinkish-gray walnut. The brain can be divided down the middle lengthwise into two halves called the cerebral hemispheres. Each hemisphere of the cerebral cortex is divided into four lobes by various sulci and gyri ...the sulci (or fissures) are the grooves and the gyri are the "bumps" that can be seen on the surface of the brain. The folding of the cerebral cortex produced by these bumps and grooves increases the amount of cerebral cortex that can fit in the skull. (In fact, the total surface area of the cerebral cortex is about 324 square inches - about the size of a full page of newspaper!). Although most people have the same patterns of gyri and sulci on the cerebral cortex, no two brains are exactly alike. 34

Layers of the cerebral Hemispheres (Cerebrum):

Layers of the cerebral Hemispheres (Cerebrum) Gray matter Outer layer Composed mostly of neuron cell bodies White matter Fiber tracts inside the gray matter Example: corpus callosum connects hemispheres The surface is made of ridges (gyri) and grooves ( sulci) 35

Lobes of the brain:

FRONTAL LOBE Located in front of the central sulcus. Concerned with reasoning, planning, parts of speech and movement (motor cortex), emotions, and problem-solving. PARIETAL LOBE Located behind the central sulcus. Concerned with perception of stimuli related to touch, pressure, temperature and pain. TEMPORAL LOBE Located below the lateral fissure. Concerned with perception and recognition of auditory stimuli (hearing) and memory (hippocampus). OCCIPITAL LOBE Located at the back of the brain, behind the parietal lobe and temporal lobe. Concerned with many aspects of vision. Lobes of the brain 36

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Figure: Some major subdivisions of the human cerebral cortex The four lobes: occipital, parietal, temporal, and frontal. 37

Brain structures:

Brain structures 38

Cerebral Cortex:

Cerebral Cortex Functions: Thought Voluntary movement Language Reasoning Perception The word "cortex" comes from the Latin word for "bark" (of a tree). This is because the cortex is a sheet of tissue that makes up the outer layer of the brain. The thickness of the cerebral cortex varies from 2 to 6 mm. The right and left sides of the cerebral cortex are connected by a thick band of nerve fibers called the "corpus callosum." In higher mammals such as humans, the cerebral cortex looks like it has many bumps and grooves. A bump or bulge on the cortex is called a gyrus (the plural of the word gyrus is "gyri") and a groove is called a sulcus (the plural of the word sulcus is "sulci"). Lower mammals, such as rats and mice, have very few gyri and sulci. 39


Cerebellum Functions: Smooth & accurate voluntary movements (cerebrocerebellum) Balance Regulation of posture Planning and timing of sequential voluntary body and limb movements. The word "cerebellum" comes from the Latin word for "little brain." The cerebellum is located behind the brain stem. In some ways, the cerebellum is similar to the cerebral cortex: the cerebellum is divided into vestibulocerebellum, cerebrocerebellum/ neocerebellum & spinocerebellum. 40

Brain stem:

Brain stem Functions: Breathing Heart Rate Blood Pressure The brain stem is a general term for the area of the brain between the thalamus and spinal cord. Structures within the brain stem include the medulla, pons, tectum, reticular formation and tegmentum. Some of these areas are responsible for the most basic functions of life such as breathing, heart rate and blood pressure. Hypothalamus Functions: Regulation of body temperature Emotions & behavior Regulation of Hunger & thirst Control of Circadian Rhythms (e.g. renal secretion, adrenocortical activity) Neurosecretion : oxytocin, ADH Regulation of sexual behavior and reproduction The hypothalamus is composed of several different areas and is located at the base of the brain. The hypothalamus acts as a "thermostat" by sensing changes in body temperature and then sending signals to adjust the temperature. Nuclei of hypothalamus: in medial zone – preoptic nucleus, paraventricular nucleus, posterior nucleus, infundibular nucleus. In lateral zone – supraoptic nucleus, large lateral nucleus, lateral tubular nucleus. 41

Basal ganglia:

Basal ganglia Functions: Timing and scaling the intensity of movements.i.e. to control the speed and time for a movement To help the cortex execute subconscious but learned patterns of movements To help plan multiple parallel and sequential patterns of movement that the mind must put together to accomplish a purposeful task. Control emotional expression movement. The basal ganglia, like the cerebellum, constitute another accessory motor system that functions usually not by itself but in close association with the cerebral cortex. B.G receives most of their input signals from the cerebral cortex and also return almost all their output signals back to the cerebral cortex. On each cerebral hemisphere, the B.G consist of the caudate nucleus, putamen, globus pallidus, substantia nigra and subthalamic nucleus. 42


Thalamus Functions: Sensory processing Movement The thalamus receives sensory information and relays this information to the cerebral cortex. The cerebral cortex also sends information to the thalamus which then transmits this information to other areas of the brain and spinal cord. Midbrain Functions: Vision Audition Eye Movement Body Movement The midbrain includes structures such as the superior and inferior colliculi and red nucleus. There are several other areas also in the midbrain. 43


Pons Functions : Cardiovascular and respiratory control center The pons are continuous with the medulla Medulla oblongata Functions : Heart rate Breathing Blood pressure Swallowing and vomiting 44

Cerebrospinal fluid (CSF):

Cerebrospinal fluid (CSF) Definition: It is a clear, colorless crystal – free modified tissue fluid formed by ultrafiltration of plasma in CNS. It is formed mainly in the choroid plexus of lateral ventricles. Composition: Protein: 15 – 45 mg/dl Glucose: 50 – 85 mg/dl Cl - : 720 – 750 mg/dl Cells: 0 – 3 lymphocytes/ mm 3 Functions: Protects the delicate structure of the brain & spinal cord from injury Provides nutrition for the brain Lightens the brain (makes more cheerful) Helps in drainage of metabolic end products Give protection from microorganisms by forming antibody 45

She brain – He brain:

She brain – He brain Bigger - Stronger - Faster...are there really any differences between female brains and male brains? Differences between the brains of men and women have generated considerable scientific and public interest. If there are differences in the way that men and women behave, then it is reasonable to suppose that their brains have something to do these behavioral differences. Just what are these differences and where in the brain might these differences be located? For hundreds of years, scientists have searched for differences between the brains of men and women. Early research showing that male brains were larger than female brains was used to "prove" that male brains were superior to female brains. Of course, this "proof" is NOT so simple and straight forward as you will see. Nevertheless, even today, there is plenty of controversy about the differences in the brains of men and women. Not only from an anatomical point of view, but also from a functional point of view - in other words, just what do the differences in the brains mean? 46

How the nervous system interacts with other body systems:

How the nervous system interacts with other body systems All of the systems within the body interact with one another to keep an organism healthy. Although each system has specific functions, they are all interconnected and dependent on one another. The nervous system controls various organs of the body directly. The brain also receives information from many organs of the body and adjusts signals to these organs to maintain proper functioning. 47

The Skeletal system:

The Skeletal system Function of the skeletal system.. The skeletal system makes up the framework of the body and allows us to move when our muscles contract. It stores minerals (e.g. calcium, phosphorous) and releases them into the body when they are needed. The skeletal system also protects internal organs and produces blood cells. Interaction with the nervous system.. Bones provide calcium that is essential for the proper functioning of the nervous system. The skull protects the brain from injury. The vertebrae protect the spinal cord from injury. Sensory receptors in joints between bones send signals about body position to the brain. The brain regulates the position of bones by controlling muscles. 48

The Cardio vascular system:

The Cardio vascular system Function of the cardiovascular system… The cardiovascular system delivers oxygen, hormones, nutrients and white blood cells around the body by pumping blood, and it removes waste products. Interaction with the nervous system… Endothelial cells maintain the blood-brain barrier. Baroreceptors send information to the brain about blood pressure. Cerebrospinal fluid drains into the venous blood supply. The brain regulates heart rate and blood pressure. 49

The muscular system:

The muscular system Function of the muscular system… Different types of muscles enable motion, generate heat to maintain body temperature, move food through digestive tract and contract the heart. Interaction with the nervous system… Receptors in muscles provide the brain with information about body position and movement. The brain controls the contraction of skeletal muscle. The nervous system regulates heart rate and the speed at which food moves through the digestive tract. 50

The Endocrine system:

The Endocrine system Function of the endocrine system… The endocrine system secretes hormones into blood and other body fluids. These chemicals are important for metabolism, growth, water and mineral balance, and the response to stress. Interaction with the nervous system… Hormones provide feedback to the brain to affect neural processing. Reproductive hormones affect the development of the nervous system. The hypothalamus controls the pituitary gland and other endocrine glands. 51

The Lymphatic system:

The Lymphatic system Function of the lymphatic system… The lymphatic system protects the body from infection Interaction with the nervous system… The brain can stimulate defense mechanisms against infection The Respiratory System Function of the respiratory system… The respiratory system supplies oxygen to the blood and removes carbon dioxide. Interaction with the nervous system… The brain monitors respiratory volume and blood gas levels. The brain regulates respiratory rate. 52

The Digestive system:

The Digestive system Function of the digestive system… The digestive system stores and digests foods, transfers nutrients to the body, eliminates waste and absorbs water. Interaction with the nervous system… Digestive processes provide the building blocks for some neurotransmitters. The autonomic nervous system controls the tone of the digestive tract. The brain controls drinking and feeding behavior. The brain controls muscles for eating and elimination. The digestive system sends sensory information to the brain. 53

The Reproductive system:

The Reproductive system Function of the reproductive system… The reproductive system is responsible for producing new life. Interaction with the nervous system… Reproductive hormones affect brain development and sexual behavior The brain controls mating behavior. The Urinary system Function of the urinary system… The urinary system eliminates waste products and maintains water balance and chemical balance. Interaction with the nervous system… The bladder sends sensory information to the brain. The brain controls urination. 54

Upper & lower motor neuron:

Upper & lower motor neuron Upper motor neuron(UMN): Supraspinal neurons(i.e. pyramidal cells) and their axons are called UMN. Lesion in this tract is called UMNL. Lower motor neuron(LMN): Anterior horn cells of the spinal cord and their axons are called LMN. Lesion in this tract is called LMNL. Differences between UMNL & LMNL: UMN lesion LMN lesion 1. Paralyzed muscles are rigid 1. Paralyzed muscles are flaccid 2. Tendon reflexes exaggerated 2. Tendon reflexes diminished 3. Muscles are hypertonic *muscle tone is the state of partial contraction present in the muscle during resting condition. 3. Muscles are hypotonic 4. Superficial reflexes are lost 4. S. reflexes are often unaltered 5. Babinski sign present 5. Babinski sign absent 6. No change in skin 6. Skin is cold, bluish 55

Alzheimer’s Disease:

Alzheimer’s Disease Dementia (mental deterioration of organic or functional origin) is a brain disorder that seriously affects a person’s ability to carry out daily activities. The most common form of dementia among older people is Alzheimer’s disease (AD), which initially involves the parts of the brain that control thought, memory, and language. Clinical features of AD are: 1) an amnesic type of memory impairment, 2) deterioration of language, and 3) visuospatial deficits. Although scientists are learning more every day, right now they still do not know what causes AD, and there is no cure. AD is named after Dr. Alois Alzheimer, a German doctor. In 1906, Dr. Alzheimer noticed changes in the brain tissue of a woman who had died of an unusual mental illness. He found abnormal clumps (now called amyloid plaques; accumulation of β - amyloid peptide) and tangled bundles of fibers (now called neurofibrillary tangles). Today, these plaques and tangles in the brain are considered signs of AD. 56

Causes of Alzheimer’s Disease:

Causes of Alzheimer’s Disease Scientists do not yet fully understand what causes AD. There probably is not one single cause, but several factors that affect each person differently. Age is the most important known risk factor for AD. The number of people with the disease doubles every 5 years beyond age 65. Family history is another risk factor. Scientists believe that genetics may play a role in many AD cases. For example, early-onset familial AD, a rare form of AD that usually occurs between the ages of 30 and 60, is inherited. The more common form of AD is known as late-onset. It occurs later in life, and no obvious inheritance pattern is seen in most families. However, several risk factor genes may interact with each other and with non-genetic factors to cause the disease. The only risk factor gene identified so far for late-onset AD is a gene that makes one form of a blood protein called apolipoprotein E (ApoE). Everyone has ApoE, which helps carry cholesterol from blood to tissues. Only about 15 percent of people have the form that increases the risk of AD. It is likely that other genes also may increase the risk of AD or protect against AD, but they remain to be discovered. Scientists still need to learn a lot more about what causes AD. In addition to genetics and ApoE, they are studying education, diet, and environment to learn what role they might play in the development of this disease. Scientists are finding increasing evidence that some of the risk factors for heart disease and stroke, such as high blood pressure, high cholesterol, and low levels of the vitamin folate, may also increase the risk of AD. Evidence for physical, mental, and social activities as protective factors against AD is also increasing. 57

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An early, accurate diagnosis of AD helps patients and their families plan for the future. It gives them time to discuss care while the patient can still take part in making decisions. Early diagnosis will also offer the best chance to treat the symptoms of the disease. Today , the only definite way to diagnose AD is to find out whether there are plaques and tangles in brain tissue. To look at brain tissue, however, doctors usually must wait until they do an autopsy, which is an examination of the body done after a person dies. Therefore, doctors can only make a diagnosis of “possible” or “probable” AD while the person is still alive. At specialized centers, doctors can diagnose AD correctly up to 90 percent of the time. Doctors use several tools to diagnose “probable” AD, including: Questions about the person’s general health, past medical problems, and ability to carry out daily activities, Tests of memory, problem solving, attention, counting, and language, Medical tests—such as tests of blood, urine, or spinal fluid, and brain scans. Sometimes these test results help the doctor find other possible causes of the person’s symptoms. For example, thyroid problems, drug reactions, depression, brain tumors, and blood vessel disease in the brain can cause AD-like symptoms. Some of these other conditions can be treated successfully. How is AD Diagnosed? 58

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Parkinson’s Disease Parkinson's disease (PD) belongs to a group of conditions called motor system disorders, which are the result of the destruction of dopamine-producing portion of “substantia nigra”(in basal ganglia). The four primary symptoms of PD are involuntary tremor , or trembling in hands, arms, legs, jaw, and face; rigidity, or stiffness of the limbs and trunk; bradykinesia, or slowness of movement; and postural instability, or impaired balance and coordination. As these symptoms become more pronounced, patients may have difficulty walking, talking, or completing other simple tasks. PD usually affects people over the age of 50. In some people the disease progresses more quickly than in others.  As the disease progresses, the shaking, or tremor, which affects the majority of PD patients may begin to interfere with daily activities.  Other symptoms may include depression and other emotional changes; difficulty in swallowing, chewing, and speaking; urinary problems or constipation; skin problems; and sleep disruptions.  There are no blood or laboratory tests available to diagnose PD. 59

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Treatment of Parkinson’s Disease At present, there is no cure for PD, but a variety of medications provide dramatic relief from the symptoms.  Usually, patients are given levodopa combined with carbidopa.  Carbidopa delays the conversion of levodopa into dopamine until it reaches the brain.  Nerve cells can use levodopa to make dopamine and replenish the brain's dwindling supply.  Although levodopa helps at least three-quarters of parkinsonian cases, not all symptoms respond equally to the drug. Bradykinesia and rigidity respond best, while tremor may be only marginally reduced. Problems with balance and other symptoms may not be alleviated at all.  Anticholinergics may help control tremor and rigidity.  Other drugs, such as bromocriptine, pergolide, pramipexole, and ropinirole, mimic the role of dopamine in the brain, causing the neurons to react as they would to dopamine.  An antiviral drug, amantadine, also appears to reduce symptoms. 60

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Huntington’s Disease In 1872, the American physician George Huntington wrote about an illness that he called "an heirloom from generations away back in the dim past." He was not the first to describe the disorder, which has been traced back to the Middle Ages at least. One of its earliest names was chorea,* which, as in "choreography," is the Greek word for dance. The term chorea describes how people affected with the disorder writhe, twist, and turn in a constant, uncontrollable dance-like motion. Later, other descriptive names evolved. "Hereditary chorea" emphasizes how the disease is passed from parent to child. "Chronic progressive chorea" stresses how symptoms of the disease worsen over time. Today, physicians commonly use the simple term Huntington's disease (HD) to describe this highly complex disorder that causes untold suffering for thousands of families. 61

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Huntington's disease is an inherited disease that causes the progressive breakdown (degeneration) of nerve cells in the brain. Huntington's disease has a broad impact on a person's functional abilities and usually results in movement, thinking (cognitive) and psychiatric disorders. Most people with Huntington's disease develop signs and symptoms in their 40s or 50s, but the onset of disease may be earlier or later in life. When disease onset begins before age 20, the condition is called juvenile Huntington's disease. Earlier onset often results in a somewhat different presentation of symptoms and faster disease progression. Huntington's disease (HD) is a  neurodegenerative genetic disorder  that affects muscle coordination and leads to  cognitive  decline and  psychiatric problems . It typically becomes noticeable in mid-adult life. HD is the most common genetic cause of abnormal involuntary writhing movements called chorea , which is why the disease used to be called Huntington's chorea. Huntington’s Disease 62

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What Causes Huntington's Disease? HD results from genetically programmed degeneration of nerve cells, called neurons,* in certain areas of the brain. This degeneration causes uncontrolled movements, loss of intellectual faculties, and emotional disturbance. Specifically affected are cells of the basal ganglia, structures deep within the brain that have many important functions, including coordinating movement. Within the basal ganglia, HD especially targets neurons of the striatum, particularly those in the caudate nuclei and the pallidum. Also affected is the brain's outer surface, or cortex, which controls thought, perception, and memory. What are the Major Effects of the Disease? Early signs of the disease vary greatly from person to person. A common observation is that the earlier the symptoms appear, the faster the disease progresses. Family members may first notice that the individual experiences mood swings or becomes uncharacteristically irritable, apathetic, passive, depressed, or angry. These symptoms may lessen as the disease progresses or, in some individuals, may continue and include hostile outbursts or deep bouts of depression. The disease can reach the point where speech is slurred and vital functions, such as swallowing, eating, speaking, and especially walking, continue to decline. Some individuals cannot recognize other family members. 63

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Is There a Treatment for HD? Physicians may prescribe a number of medications to help control emotional and movement problems associated with HD. Antipsychotic drugs, such as haloperidol, or other drugs, such as clonazepam, may help to alleviate choreic movements and may also be used to help control hallucinations, delusions, and violent outbursts. Antipsychotic drugs, however, are not prescribed for another form of muscle contraction associated with HD, called dystonia, and may in fact worsen the condition, causing stiffness and rigidity. These medications may also have severe side effects, including sedation, and for that reason should be used in the lowest possible doses. For depression, physicians may prescribe fluoxetine, sertraline, nortriptyline, or other compounds. Tranquilizers can help control anxiety and lithium may be prescribed to combat pathological excitement and severe mood swings. Medications may also be needed to treat the severe obsessive-compulsive rituals of some individuals with HD. Most drugs used to treat the symptoms of HD have side effects such as fatigue, restlessness, or hyperexcitability. Sometimes it may be difficult to tell if a particular symptom, such as apathy or incontinence, is a sign of the disease or a reaction to medication . 64

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