IVMS-Multisystem- Body Communication Systems

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IVMS-Multisystem- Body Communication Systems The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs. By the time the human reaches adulthood, the body consists of close to 50 trillion cells, the basic unit of life. These cells are organised biologically to eventually form the whole body. http://www.the-human-body.net/

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Body Communication Systems : Body Communication Systems Anatomy Loyola University - Structure of the Human Body Anatomy - Radiology USUHS - Radiologic Anatomy Browser Biochemistry and Cell Biology Indiana University - Medical Biochemistry Page Physiology University of Copenhagen - Textbook in Medical Physiology and Pathophysiology Resources: Marc Imhotep Cray, M.D. BMS Professor 1 IVMS©1999-2009

Divisions of Nervous System : Divisions of Nervous System Central Nervous System (CNS) Brain Spinal Cord Peripheral Nervous System (PNS) Nerves between brain and spinal cord and the muscles, glands, and sense organs 5 IVMS©1999-2009

Slide 6 : I. Central Nervous System (CNS) A. Brain B. Spinal cord II. Peripheral Nervous System (PNS) A. Afferent (sensory) B. Efferent (motor) 1. Somatic 2. Autonomic a. Sympathetic b. Parasympathetic 6 IVMS©1999-2009

Nerve Fibers versus Nerves : Nerve Fibers versus Nerves Nerve fiber Single projection (axon) from one nerve cell Nerve Group of many nerve fibers that travel together along a similar pathway in the PNS No nerves in the CNS Groups of nerves that travel together in CNS = pathway or tract 7 IVMS©1999-2009

Nerves : Nerves Neurons = nerve cells Basic unit of the nervous system Afferent Neurons Carry messages from body and organs to CNS Efferent Neurons Carry messages from CNS to effectors (muscles and glands) or other neurons Interneurons Connect nerves within the CNS Ratio A:I:E = 1:200,000:10 8 IVMS©1999-2009

Afferent Neurons : Afferent Neurons Lack dendrites Single axon Divides shortly after leaving cell body One end receptor; other end CNS Only small portion of axon enters CNS Receptors Located at peripheral ends (farthest from CNS) Respond to changes in the internal or external environment Generate electrical signals in response to changes Send messages from receptors into CNS 9 IVMS©1999-2009

Efferent Neurons : Efferent Neurons Have cell body, multiple dendrites, and branched or unbranched axon Cell body and dendrites within CNS, axon outside CNS Carry messages from CNS to muscles and organs 10 IVMS©1999-2009

Slide 13 : IVMS©1999-2009 13 Neurotransmitter molecules, released by synaptic vesicles, cross the tiny synaptic space (or cleft) between the axon terminal (or synaptic knob) of the sending neuron and the dendrite of the receiving neuron, where they latch on to a receptor site, much the way a key fits into a lock. This is how they pass on their excitatory or inhibitory messages. Synaptic transmission ? communication between neurons

Slide 15 : I. Central Nervous System (CNS) A. Brain B. Spinal cord II. Peripheral Nervous System (PNS) A. Afferent (sensory) B. Efferent (motor) 1. Somatic 2. Autonomic a. Sympathetic b. Parasympathetic 15 IVMS©1999-2009

Slide 16 : IVMS©1999-2009 16 THE CENTRAL NERVOUS SYSTEMThe billions of neurons in the brain are connected to neurons throughout the body by trillions of synapses. The nervous system is organized into two parts: the central nervous system, which consists of the brain and the spinal cord, and the peripheral nervous system, which connects the central nervous system to the rest of the body Schematic diagram of divisions of the nervous system and subparts

Cells within the CNS : Cells within the CNS Neurons 10% by number 50% by volume Glial Cells ‘nurse’ cells; supply nutrients, remove wastes Form myelin sheaths Perform immune functions Direct neuron migration 18 IVMS©1999-2009

CNS (continued) : CNS (continued) White matter Myelinated fibers Inner part of brain Outer part of spinal cord Conducts nerve impulses Gray matter Non-myelinated fibers Outer part of brain Inner part of spinal cord Receives and interprets nerve impulses 19 IVMS©1999-2009

Basal Ganglia : Basal Ganglia Gray matter deep within white matter of brain Code and relay information about body movements Important in maintenance of balance and posture Lesioned in Parkinson’s disease Symptoms: uncontrolled movements, muscular rigidity, tremors, difficulty in initiating movement Associated with deficient dopamine levels Treatment with L-Dope = dopamine precursor capable of crossing the blood-brain barrier 20 IVMS©1999-2009

Meninges : Meninges Protective membranes covering the brain and spinal cord 3 membranes Dura mater Just beneath skull Arachodonic Middle membrane Pia mater Adjacent to (immediately overlies) neural tissue Subdural space Subarachnoid Space Epidural Space 21 IVMS©1999-2009

Cerebrospinal Fluid (CSF) : Cerebrospinal Fluid (CSF) Fluid that fills the subarachnoid space Subarachnoid space = space between the pia mater and the arachnoid membranes CNS ‘floats’ in CSF Fluid is secreted by epithelial cells lining ventricles Ventricles = cavities within brain Restricted diffusion of proteins and other substances into the CSF by blood-brain barrier Composition of fluid around brain is not same as that of extracellular fluid in other parts of body 22 IVMS©1999-2009

Brain Divisions : Brain Divisions Cerebrum Diencephalon Core of anterior part of brain Contains hypothalamus and thalamus Brainstem Midbrain Pons Medulla oblongata Cerebellum Forebrain 23 IVMS©1999-2009

Brainstem : Brainstem Located at base of brain Relay station; transfers signals between spinal cord, cerebellum, and cerebrum Involved in motor functions Respiratory control Cardiovascular control Involved in reflexive functions Swallowing, vomiting, coughing Involved in sleep/wakefulness and attention 24 IVMS©1999-2009

Brainstem Divisions : Brainstem Divisions Midbrain Connects cerebrum and lower brainstem Involved in posture maintenance and movement Pons Connects midbrain and medulla oblongata Relay station to connect cerebrum and cerebellum Medulla oblongata Site of cardio and respiratory control centers 25 IVMS©1999-2009

Cerebral cortex : Cerebral cortex Cerebral cortex Outer shell of gray matter; 15 billion neurons Inner layer white matter Nuclei of gray matter deep within white matter Corpus collosum Nerve tract connecting right and left hemispheres Central core = diencephalon Contains thalamus and hypothalamus 27 IVMS©1999-2009

Cerebral Cortex (continued) : Cerebral Cortex (continued) Divided into four lobes Temporal Parietal Frontal Occipital Three major areas of function Sensory cortex; recognizes/perceives sensory stimuli Motor cortex; initiates/coordinates voluntary movements Associative cortex; involved in cognitive functions such as memory, reasoning, abstract thought, and consciousness 28 IVMS©1999-2009

Slide 29 : IVMS©1999-2009 29 These four lobes are both physically and functionally distinct. Each lobe contains areas for specific motor sensory function as well as association areas See Notes of this and the previous slide The four lobes of the cerebral cortex

Primary Cerebral Areas : Primary Cerebral Areas Sensory area Receives and processes sensory input from body regions Motor area Concerned with coordinated movements Specific region of primary cortex controls specific body region; not necessarily proportionate Motor area on left side of brain controls muscles on right side of body and vice versa 30 IVMS©1999-2009

Association Cortex : Association Cortex Regions not part of, but adjacent to motor/sensory cortex Involved in more complex analysis of incoming information Combines sensory input with input from arousal, memory, language, and emotional regions of brain 32 IVMS©1999-2009

Frontal Lobe : Frontal Lobe Region of anterior cerebral cortex Motor area of brain Initiates voluntary movement and fine movements Contains Broca’s speech center Important in translating thought into speech ‘Word formation center’ When damaged results in inability to speak Also some ‘association’ areas of brain 33 IVMS©1999-2009

Parietal Lobe : Parietal Lobe Located in middle of each cerebral hemisphere Is the general sensory area Integrates and interprets sensation i.e. pressure, heat, and cold Contains some ‘associative centers’ 34 IVMS©1999-2009

Temporal Lobe : Temporal Lobe Located under frontal and parietal lobes Primary auditory center Interprets and distinguished sounds Site of Wernicke’s area Region important in understanding written or spoken language Also important in memory 35 IVMS©1999-2009

Diencephalon : Diencephalon Thalamus Relay station Relays/intergrates sensory inputs (all except olfactory) Important in nonspecific arousal and focused attention Hypothalamus Lies below thalamus ‘Master command center’ for neural and endocrine system coordination Most important control area for internal environment homeostasis and behaviors essential to survival of the individual (eating/sleeping) and species (reproduction) 37 IVMS©1999-2009

Spinal Cord : Spinal Cord Gray matter Central portion Interneurons, cell bodies and dendrites of efferent fibers, entering tips of afferent fibers, glial cells White matter Outer portion Groups of interneurons in ‘tracts’ 39 IVMS©1999-2009

Nerve Entry Into and Exit From Spinal Cord : Nerve Entry Into and Exit From Spinal Cord Sensory fibers enter on dorsal (toward back) side of cord Efferent fibers exit on ventral (toward belly) side of cord Spinal nerves A short distance outside cord, dorsal and ventral roots from same level combine to form spinal nerves 31 pairs of spinal nerves; 8 cervical, 12 thoracic, 5 lumbar, 5 sacral , 1 coccygeal (tailbone) regions 40 IVMS©1999-2009

Slide 41 : IVMS©1999-2009 41 The spinal cord is a complex cable of nerves that connects the brain to most of the rest of the body It is made up of bundles of long nerve fibers and has two basic functions: to permit some reflex movements and to carry messages to and from the brain. Spinal Cord

Reflexes : Reflexes Stereotyped (predictable), rapid responses to stimuli applied to the periphery Mediated by nerves within the spinal cord Two types Monosynaptic; has a single synapse between an afferent and an efferent fiber e.g. patellar knee jerk reflex Faster than polysynaptic reflex Polysynaptic; has multiple synapses, between afferent neuron, interneuron(s), and efferent neuron e.g. withdrawl reflex 42 IVMS©1999-2009

Components of Reflex Arcs : IVMS©1999-2009 43 Components of Reflex Arcs Monosynaptic Reflex Arc: Sensory Receptor Afferent Neuron Synapse Efferent Neuron Effector Polysynaptic Reflex Arc: Sensory Receptor Afferent Neuron Synapse Interneuron Synapse Efferent Neuron Effector

Slide 44 : I. Central Nervous System (CNS) A. Brain B. Spinal cord II. Peripheral Nervous System (PNS) A. Afferent (sensory) B. Efferent (motor) 1. Somatic 2. Autonomic a. Sympathetic b. Parasympathetic 44 IVMS©1999-2009

Peripheral Nervous System (PNS) : Peripheral Nervous System (PNS) Nerve fibers that connect sensory receptors and effectors (muscles/glands) with CNS 43 pairs of nerves 12 pairs cranial nerves 31 pairs of spinal nerves 45 IVMS©1999-2009

Cranial Nerves : Cranial Nerves Connect brain and muscles, glands, and sensory receptors of the head, organs of thoracic/abdominal cavities Examples Olfactory Optic Oculomotor Trochlear Glossopharyngeal Vagus 46 IVMS©1999-2009

Spinal Nerves : Spinal Nerves 31 pairs Enter and exit spinal cord at specific points 8 cervical Transmit neural signals to and from muscles and glands of neck, shoulders, arms, and hands 12 thoracic Associated with the chest and abdominal walls 5 lumbar Associated with the hips and legs 5 sacral Associated with genitals and lower digestive tract 1 coccygeal 47 IVMS©1999-2009

PNS Pathways : PNS Pathways Ascending pathways (tracts) Sensory pathways Nerve fibers and nerves that bring information to the brain Descending pathways (tracts) Motor pathways Nerve fibers and nerves that carry information from the CNS to the periphery 48 IVMS©1999-2009

‘Crossing Over’ Within CNS : ‘Crossing Over’ Within CNS Ascending sensory input can cross over to the side of the CNS that is opposite to the location of the stimulated receptors Information from left side of body is transferred to right side of brain and vice versa Signals can cross over within the spinal cord, or within the brain 49 IVMS©1999-2009

Anterior-lateral Pathway : Anterior-lateral Pathway Crossover occurs within the spinal cord Fibers are small and myelinated Conduction velocity is slower than in dorsal column lemniscal pathways 51 IVMS©1999-2009

‘Crossing Over’ Within CNS : ‘Crossing Over’ Within CNS Descending motor responses originating in the motor cortex cross over to the alternate side Result: Motor control of right side of body originates in left side of brain and vice verse 52 IVMS©1999-2009

Sensory Receptors : Sensory Receptors Generally, peripheral end of sensory nerve fiber has multiple branches, each with terminal receptor There are different types of sensory receptors Mechanoreceptors; touch, sound, deep pressure, Chemoreceptors; oxygen, glucose, osmoreceptors Electromagnetic receptors; vision Thermal receptors; cold/heat Nociceptors; pain 53 IVMS©1999-2009

Receptive Fields : Receptive Fields Multiple receptor endings associated with a single sensory nerve fiber Sensory unit = single afferent neuron and all its receptor endings Receptive field = the portion of the body that, when stimulated, activates a particular afferent neuron 54 IVMS©1999-2009

Referred Pain : Referred Pain Pain receptors are activated by stimuli that cause or are near the point of causing tissue damage Respond to mechanical, chemical, and/or thermal stimuli Phenomenon in which sensation of pain is experienced at a site other than at the site of tissue injury or damage e.g. heart attack causes feelings of indigestion/arm pain Occurs because visceral and somatic afferent fibers often converge on the same interneurons in spinal cord pain pathways 55 IVMS©1999-2009

Efferent Motor Pathways in PNS : Efferent Motor Pathways in PNS Somatic Innervates skeletal muscles; controls voluntary motor activity Pathways always cross over in CNS so that right side of brain controls skeletal muscles on left side of body and vice versa Autonomic Innervates smooth muscle and glands Controls involuntary motor activity 56 IVMS©1999-2009

Slide 57 : I. Central Nervous System (CNS) A. Brain B. Spinal cord II. Peripheral Nervous System (PNS) A. Afferent (sensory) Efferent (motor) 1. Somatic 2. Autonomic a. Sympathetic b. Parasympathetic 57 IVMS©1999-2009

Slide 58 : IVMS©1999-2009 58 The second major division of the nervous system, the peripheral nervous system, carries messages to and from the central nervous system It comprises two parts: the somatic and the autonomic nervous systems THE PERIPHERAL NERVOUS SYSTEM

Somatic Division of (Efferent) PNS : Somatic Division of (Efferent) PNS Nerves go to skeletal muscle Single fiber from CNS to muscle No synapses outside CNS Stimulate motor end plate via neurotransmitter release Neurotransmitter released is always acetylcholine (ACh) ACh is always stimulatory 59 IVMS©1999-2009

Autonomic Division of (Efferent) PNS : Autonomic Division of (Efferent) PNS Innervates smooth/cardiac muscle and glands Two divisions Sympathetic Parasympathetic Fibers always synapse outside of the CNS Ganglia = cluster of neuronal cell bodies outside CNS Presynaptic fiber = fiber that leaves CNS and terminates at synapse Postsynaptic fiber = fiber that originates at synapse and terminates at effector Ach is NT released from presynaptic fibers 60 IVMS©1999-2009

Autonomic Division of (Efferent) PNS : IVMS©1999-2009 61 The autonomic nervous system carries messages between the central nervous system and the internal organs. It is broken into two parts: the sympathetic and parasympathetic divisions. The first acts primarily to arouse the body; the second, to relax and restore the body to normal levels of arousal. Autonomic Division of (Efferent) PNS

Sympathetic Division of Autonomic NS : Sympathetic Division of Autonomic NS Short presynaptic fiber; long postsynaptic fiber Norepinephrine (NE) = neurotransmitter released at effector NE can have stimulatory or inhibitory effect on effector Functions in ‘Fight or Flight’ stress response 62 IVMS©1999-2009

Parasympathetic Division of Autonomic NS : Parasympathetic Division of Autonomic NS Long presynaptic fiber; Short post- synaptic fiber ACh = neurotransmitter released at effector ACh can have stimulatory or inhibitory effect on effector Functions in ‘housekeeping’ capacity 63 IVMS©1999-2009

Hearing : Hearing Ear = mechanical receptor converts mechanical energy (sound waves) into electrical energy (action potentials) Three subdivisions outer ear middle ear inner ear Sound receptors = hair cells in Organ of Corti Balance/movement receptors = hair cells in semicircular canals 65 IVMS©1999-2009 http://en.wikipedia.org/wiki/Ear 3D Ear page Details of various ear problems

Outer Ear : Outer Ear Auricle (pinna) cartilagenous collects sound waves External ear canal funnels sound to middle ear protection; cerumen (ear wax) 66 IVMS©1999-2009 3D Ear page The tutorial consists of the following sections: Overview Ossicles Tympanic Membrane Tendons Nerves Inner Ear

Middle Ear : Middle Ear Middle ear = tympanic cavity tympanic membrane (eardrum) separates from outer ear canal Air-filled chamber Eustachian tube = tube that connects middle ear to throat and equalizes pressure in middle ear to atmospheric pressure Middle ear bones malleus (hammer), incus (anvil), stapes (stirrup) 67 IVMS©1999-2009

Middle Ear Bones : Middle Ear Bones Three bones Malleus (hammer) Incus (anvil) Stapes (stirrup) Conduct sound vibrations from eardrum to inner ear eardrum vibrates, moves malleus, movement of malleus moves incus, movement of incus moves stapes vibrations of stapes transmitted to membrane of oval window Amplify sound pressure 68 IVMS©1999-2009

Inner Ear : Inner Ear Fluid-filled cavity Functions in auditory system (hearing) and vestibular (balance & equilibrium) system acoustic nerve (cranial nerve 8) transmits action potentials for both hearing and balance/movement cochlear branch carries impulses for sound vestibular nerve carries impulses for balance/movement Site of the sound receptors 69 IVMS©1999-2009 3D Ear page The tutorial consists of the following sections: Overview Ossicles Tympanic Membrane Tendons Nerves Inner Ear

Cochlea : Cochlea Fluid-filled, spiral-shaped chamber Location of the receptor cells for auditory stimuli Organ of Corti Sits on basilar membrane high frequency (high pitch) sounds vibrate membrane closest to middle ear low frequency (low pitch) sounds vibrate membrane farthest from middle ear contains receptor cells (hair cells) 71 IVMS©1999-2009

Hair Cells : Hair Cells Mechanoreceptors transform pressure waves (sound waves) into action potentials hair cells bend as they move across tectorial membrane bending opens ion channels, allows for membrane depolarization and generation of receptor potential hair cell depolarization release of NT (glutamate) activates afferent fibers that transmit impulse to brain via cochlear nerve 72 IVMS©1999-2009

Vestibular System : Vestibular System Vestibular apparatus series of fluid-filled tubes (semi-circular canals) detect angular acceleration during head rotation in three planes utricle saccule Receptor cells = hair cells 73 IVMS©1999-2009

Eye Structure : Eye Structure Pupil Hole in center of eye Diameter changes to regulate light entry Iris Colored ring around the pupil Composed of smooth muscle Sympathetic stimulation of iris enlarges pupil Parasympathetic stimulation of iris makes pupil smaller 75 IVMS©1999-2009 Gross Anatomy of the Eye

Slide 76 : Eye Structure Cornea Outer covering over the iris Bends incoming light rays to focus image on retina in back of eyeball Image projected onto retina in UPSIDE DOWN and BACKWARDS Lens Lies beneath iris Important in accommodation Change in shape of lens to allow for viewing of objects at different distances Lens flattened and oval-shaped for viewing distant objects Lens rounded and spherical for viewing near objects 76 IVMS©1999-2009 http://en.wikipedia.org/wiki/Eye Gross Anatomy of the Eye

Slide 77 : Eye Structure (continued) Sclera ‘White’ of the eye Fibrous membrane that protects and supports the eye Choroid Coat Lies inside the sclera Richly vascularized Supplies tissues of eye with nutrients and oxygen 77 IVMS©1999-2009 Gross Anatomy of the Eye

Slide 78 : Fovea Centralis Central portion of the retina Cone density very high Is region of greatest visual acuity Blind spot Area of retina where optic nerve exits Lacks photoreceptive cells (rods and cones) Eye Structure (continued) 78 IVMS©1999-2009 Gross Anatomy of the Eye

Slide 79 : Lacrimal glands Produce tears Functions in lubrication and protection of eye Keeps eyes moist Flushes particulate debris/foreign material from surface of the eye Conjunctiva Membrane lining inside of eyelid Highly sensitive Eye Structure (continued) 79 IVMS©1999-2009

Slide 80 : Liquid between iris and cornea in anterior chamber Nourishes tissues of cornea and lens Produced by ciliary process Drained by canal of Schlemm into lymph system Aqueous Humor 80 IVMS©1999-2009

Slide 82 : Retina Pigmented layer Fixed to the choroid Contains Melanin; pigment that prevents light scattering and sharpens image Albinos lack melanin; results in blurred vision Inner (Sensory) layer Locations of sensory receptors for vision Rods and Cones = modified neurons that convert electomagnetic (light) waves into neural (electrical) signals 82 IVMS©1999-2009

Slide 83 : Rods 130 million per eye Photopigment = Rhodopsin Vitamin A derivative Highly light sensitive, breaks down when exposed to light Extremely sensitive; respond to very low levels of illumination Function primarily in night and peripheral vision 83 IVMS©1999-2009

Slide 84 : Cones 5.5 million per eye Photopigment = iodopsin Less light sensitive, requires more illumination to break it down Less sensitive; respond only to bright illumination Function primarily in day vision, color discrimination, and perception of sharp visual detail 84 IVMS©1999-2009

Nervous System Aging : Nervous System Aging Neuronal loss occurs in aging varies from brain region to brain region varies from individual to individual neurons, dendrites, and synapses are lost Accumulation of substances in brain occurs lipofuscin neurofibrillary tangles neuritic plaques Biochemical changes; neurotransmitter imbalances 88 IVMS©1999-2009

Sensory System Aging : Sensory System Aging Presbyopia inability to clearly view nearby objects due to stiffening of lens Cataracts pigment accumulation in the eye causes lens to change from clear to opaque Glaucoma increased pressure in the eye rate of production of aqueous humor that exceeds rate of removal of aqueous humor 89 IVMS©1999-2009

Sensory System Aging : Sensory System Aging Presbycusis = loss of hearing with aging loss of high pitch acuity in men cochlea hair cells degenerate auditory nerves degenerate/demyelinate 90 IVMS©1999-2009

Neural Plasticity : Neural Plasticity Nerve cell regeneration can occur New synapse formation can occur Nerve ‘growth factors’ are involved direct neural reorganization and repair are more abundant in younger individuals Prevention of accumulation of excessive levels of neurotransmitter (i.e. glutamate production following brain injury and stroke) 91 IVMS©1999-2009

Treating the Damaged Brain : Treating the Damaged Brain Drugs must be designed to get through BBB Antibody ‘carriers’ to deliver drugs Viral ‘carriers’ to deliver genetic material Bacterial alkyloids naturally-occurring bacterial proteins that bind to and activate neural growth factor receptors 92 IVMS©1999-2009

Parkinson’s Disease : Parkinson’s Disease 500,000 afflicted in US alone Progressive loss of neurons critical to movement basal ganglia defect; inadequate dopamine levels causes: free radical damage and overactive immune system Disease typically manifests @ 60 yrs of age Michael J Fox = exception to the rule 93 IVMS©1999-2009

Symptoms of Parkinson’s Disease : Symptoms of Parkinson’s Disease Rhythmic tremor pill rolling movement often in one hand Leaning loss of balance and coordination Muscle Rigidity Difficulty in rising Microphagia = shrinkage of handwriting 94 IVMS©1999-2009

Treatment of Parkinson’s Disease : Treatment of Parkinson’s Disease Treat with L-Dopa dopamine cannot cross BBB L-Dope = dopamine precursor that can cross BBB L-Dopa effectiveness diminishes with prolonged treatment 95 IVMS©1999-2009

The glands of the endocrine system : The glands of the endocrine system IVMS©1999-2009 96 THE ENDOCRINE SYSTEMThe endocrine system—the other communication system in the body—is made up of endocrine glands that produce hormones, chemical substances released into the bloodstream to guide such processes as metabolism, growth, and sexual development. Hormones are also involved in regulating emotional life.

The Thyroid Gland : The Thyroid Gland The thyroid gland secretes thyroxin, a hormone that can reduce concentration and lead to irritability when the thyroid is overactive, and cause drowsiness and a sluggish metabolism when the thyroid is under active. IVMS©1999-2009 97 http://en.wikipedia.org/wiki/Thyroid

The Parathyroid Glands : The Parathyroid Glands Within the thyroid are four tiny pea-shaped organs, the parathyroids, that secrete parathormone to control and balance the levels of calcium and phosphate in the blood and tissue fluids. This, in turn, affects the excitability of the nervous system. IVMS©1999-2009 98 http://en.wikipedia.org/wiki/Parathyroid _glands

The Pineal Gland : The Pineal Gland The pineal gland is a pea-sized gland that apparently responds to exposure to light and regulates activity levels over the course of the day. IVMS©1999-2009 99 http://en.wikipedia.org/wiki/Pineal_Gland

The Pancreas : The Pancreas The pancreas lies in a curve between the stomach and the small intestine and controls the level of sugar in the blood by secreting insulin and glucagon. IVMS©1999-2009 100