Nervous system

INTEGRATION AND CONTROL

• The nervous and endocrine systems interact to control most ofthe body functions

• The nervous system exerts rapid controls via nerve impulses; theendocrine system’s effects are mediated by hormones and aremore prolonged.

• Both systems are communication systems that receive anddeliver messages throughout the body.

The Nervous

System

Integration and Control

• The nervous system control most of thebody functions

• This exerts rapid controls via nerveimpulses

• are communication systems thatreceive and deliver messagesthroughout the body.

• The nervous system allows reaction toa stimulus

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• The nervous system allows reaction to a stimulus.−A stimulus is a change in the

environment that elicit a response• Example: A hot stove

• The reactions are automatic.−no need to think about the reactions• Example: If a bug flies by the eye,

automatically the eye will blink

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The Nervous System

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THREE (3) FUNCTIONS OF NERVOUS SYSTEM

3. Generates Motor Output - motor output is the conduction of signals from the integration center, to the effector cells, the muscle cells or gland cells that actually carry out the body´s responses to the stimuli

2. Performs Integration- processes and interprets sensory input and decides what should be done at each moment

1. Receives Sensory Input- uses millions of sensory receptors (present in skin and other organs )to monitor changes occurring both inside and outside of the body Sensory input

Motor output

Integration

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Basic structure of a nerve cell

• Neuron/Nerve cell - The functional unit of thenervous system

• Cell body – integrates the message• Dendrites - are highly branched extensions

that receive signals from other neurons andconvey this information toward the cell body

• Axon - typically a much longer extension thattransmits signals to other cells

• The myelin sheath, resembles a chain ofoblong beads, wraps around the axon

• Gaps between Schwann cells are called nodesof Ranvier

• A typical axon has hundreds or thousands ofthese branches, each with a synaptic terminalat the very end.

• The junction between a synaptic terminal andanother cell is called a synapse.

Types of neurons

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Sensory neuron – transmit signals/nerve impulses from the afferent or sensory organs of the brain (sense)

- Sensory (afferent) neurons take nerve impulses from sensory receptors to the CNSMotor neuron - take nerve impulses from the CNS to muscles or glandsInterneurons - Occur entirely within the CNS. convey nerve impulses between various parts of the CNS. some take messages from one side of the spinal cord to the other or from the brain to the cord, and vice versa

NERVE SIGNALS AND THEIR TRANSMISSION

• Membrane Potential – potential energyexists as an electrical charge differenceacross the neuron’s plasma membrane

• The potential of a neuron that is notbeing stimulated is its resting potential

• A resting membrane has many openpotassium (K+) channels but only a fewopen sodium (Na+) channels, allowingmuch more potassium than sodium todiffuse across the membrane.

• Therefore, Na+ is more concentratedoutside the neuron than inside.

• Sodium-potassium (Na+-K+) pumps –membrane proteins that help maintainresting potential

Nerve function depends on charge

differences across neuron membranes

• Action potential - a change in membrane voltage that transmits a nervesignal along an axon.

• It is caused by the opening and closing of channel proteins with gatesthat open at a particular voltage or membrane potential

A nerve signal begins as a change in the membrane potential

1. When this region of the axon(blue) has its Na+ channels open,Na+ rushes inward, and anaction potential is generated

2. Soon, the K+ channels in thatsame region open, allowing K+to diffuse out of the axon; at thistime, its Na+ channels are closedand inactivated at that point onthe axon

3. A short time later, we would seeno signs of an action potential atthis (far-left) spot because theaxon membrane here hasrestored itself and returned toits resting potential

Propagation of the action potentialalong an axon

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Chemical synapse- The communicationpoint between twoneurons, or between aneuron and a muscle orgland

Nervous system of representative organisms

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Comparative functional anatomy of nervous system in invertebrates

Protozoa

- Protozoans lack specialized nervous system to respond to the environment.-Single cell function as both the receptor and

the effector.-Contain an eyespot that act as a light

sensitive receptor.


Porifera

-Poriferans or the sponges are the

only multicellular animals without a nervous

system. They do not show any neurons or

sensory cells.

-Although they lack a nervous system

they are sensitive to pressure and touch that

helps in their locomotion.


Cnidaria

-Contains a diffuse nerve net.

-Sensory neurons, intermediate

neurons and motor neurons are present

-These neurons are connected

together by synapses.

-Synapses carry impulses to both

directions within the nerve net.Hydra sp.

Nerve net is present.

Contain multipolar neurons.

Echinodermata

-Echinoderms show ganglia along the

radial nerves.

-They include the cell bodies of

almost all motor neurons and

intermediate neurons.

-A central nerve ring surrounds the

gut connecting the radial nerves.

-Some shows Ocelli to sense light.

- Sensory neurons lie within the

ectoderm, and send axons to the radial

nerves.



Platyhelminthes- Bilateral symmetry and cephalization have led to the nervous system.

- Shows the primitive arrangement of the central nervous system.

- Nervous system resembles a ladder.

- Two long nerves are connected to the cerebral ganglia

located in the head region.

- Short, smaller nerves are connected to the nerve cord.

- Auricles can be found at the sides of the head.

- These contain sensory receptors.

- Eyespots are also present.

Turbellaria (Planarians)

Cestoda (Tapeworms)

Nematoda- At the anterior end cerebral ganglion is present

composed of dense circular nerve ring surrounding the

pharynx.

- Arising from the nerve ring four nerves run along the

length of the body as one dorsal, one ventral and two lateral

nerves.

- Each nerve is located within a cord of connective tissue

lying beneath the cuticle and between muscle cells.

- Dorsal nerve trunk is motor, lateral trunks are sensory

and ventral nerve function as both.


Annelida- Nervous system is segmented.

- Pair of cerebral ganglia (supra-pharyngeal)

situated above and in front the pharynx.

- Two lateral nerves (circum or pharyngeal

connectives) form a ring around the pharynx connecting

the ganglia.

- A pair of mid ventrally placed nerves that

connected to the anterior nerve ring, run throughout the

length of the body. These nerves have a ganglion in

each of the body segment from which nerves are given

out to various organs.

- Most annelids have giant axons.

- Some annelids have ocelli or simple eyes.


Mollusca-Shows great range of nervous systems.

-Typical nervous system of Mollusks is

composed of three pairs of ganglia connected

with one another by bundles of nerve fibers but

distributed in a characteristically scattered

manner.

- One pair of ganglia above the oesophagus

is called as "supra-oesophageal" or "cerebral"

ganglion.

- A pair of ganglia below the oesophagus is

called as "infra-oesophageal" or "pedal"

ganglion.

- The other pair of ganglia is called as

"branchial" or "parieto-splanchnic" ganglion.

- In higher Molluscs, the cerebral and pedal

ganglia are fused forming an oesophageal ring.

- Several ganglia are present that are

connected with long nerves.


Arthropoda

-Similar to annelid nervous system

but more advanced in structure.

-Central nervous system is present.

-Supra-oesophageal or cerebral

ganglion is located in the head

segment. This serves as the brain.

-Most arthropods show well

developed sensory organs such as

compound eyes and antennae.

-Compound eyes contain

‘Ommatidia’ that samples a small

part of the visual field.


• Peripheral Nerves

WHAT PARTS DO YOU KNOW THAT ARE IN THE NERVOUS SYSTEM?

•Brain

• Spinal Cord

Vertebrate Nervous System

Stages in the processing of information by Nervous System

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Divisions of the Nervous System

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Divisions of the nervous system

A. Central nervous systemA. Includes the brain and spinal cord• Seat of complex brain functions such as

memory, intelligence, learning and emotion (love, hate, fear, anger, elation and sadness)

• Receives and interprets the countless signals that are sent to it from other parts of the body and from the external environment

• The brain controls everything in the body

• The human brain is about 1.3kg of jelly-like tissue made up of ca. 100B neurons

• divided into three parts and is protected by the skull or cranium

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1) Dura matter- outermost membrane, the toughest and the thickest

2) Arachnoid-middle membrane below the dura matter

3) Pia matter-the innermost membrane consisting mainly of small blood vessels following the surface of the brain supported by cerebrospinal fluid

4) Basic nuclei – important centers for planning, learning movement sequences

Protection of the brain

5) Cerebral cortex - sensory information is analyzed, motor commands are issued & language is generated

Surface Anatomy

• Gyri (plural of gyrus)• Elevated ridges

• Entire surface

• Grooves separate gyri• A sulcus is a shallow groove (plural, sulci)

• Deeper grooves are fissures

The brain has three main parts…

1) Cerebrum

2) Cerebellum

3) Brain Stem

4) Diencephalon

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Parts of Brain

• Cerebrum - also called thetelencephalon, is the largest portion of the brain in humans

• performs sophisticated integration; plays major role in memory, learning, speech, emotions; formulates complex behavioral responses

• Divided into four lobes

Cerebellum- receives sensory inputfrom the eyes, ears, joints,and muscles about thepresent position of bodyparts, and it also receivesmotor output from thecerebral cortex aboutwhere these parts shouldbe located.- After integrating this

information, the cerebellumsends motor impulses byway of the brain stem tothe skeletal muscles.

• The Brain Stem connects the brain to the spinal cord

• The nerves in the brain stem control your heartbeat, breathing, and blood pressure

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•Hypothalamus – located below thethalamus. The main visceral controlcenter of the body and is vitallyimportant to overall bodyhomeostasis i.e. autonomic controlcenter, center for emotional response,body temperature regulation,Regulation of food intake, waterbalance and thirst, sleep-wake cyclesand control of endocrine systemfunctioning

Diencephalon

central core of the forebrain and surrounded by the cerebral hemispheres

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• Thalamus - specializes in sense reception

• Epithalamus – the most dorsal portion of the diencephalon and forms the roof of the third ventricle Extending from its posterior border and visible externally is the pineal gland. – The pineal gland secretes the

hormone melatonin (a sleep-inducing signal and antioxidant; and, along with hypothalamic nuclei, helps regulate the sleep-wake cycle. 39

Simplified Function of the Brain…

•Back of brain: perception

•Top of brain: movement

•Front of brain: thinking

Spinal cord

http://www.apparelyzed.com/spinalcord.html

• The spinal cord isthe part of thenervous systemthat connects thebrain to the rest ofthe nervoussystem.

• The spinal cordsends messages tothe brain.

• Responsible for providing sensory (afferent) information to the central nervous system

• Carries motor (efferent) commands out to the body’s tissues

• Includes all neural tissue outside of the central nervous system−Somatic nervous system−Autonomic nervous system

B. Peripheral nervous system

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The peripheral nervous system is composed of the nerves and the sense

organs.

Ear Eye

Skin

Nerves

Tongue

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Receptors and Sense Organs

• Aristotle classified five senses, continued to be regarded as the classical senses, although scientists have determined the existence of as many as 15 additional senses

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Cranial Nerves

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Oh, Oh, Oh, To Touch And Feel Virgin Girl'sVagina Ahhhh Heaven

Spinal Nerves

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Somatic nervous system isthe part of the peripheralnervous system associatedwith the voluntary control ofbody movements via skeletalmuscles.

- consists of efferentnerves responsible forstimulating muscle contraction,including all the non-sensory neurons connectedwith skeletal muscles and skin.

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Parasympathetic Division- Peaceful, Housekeeping Division- in control most of the time- “rest and digest” or “feed and breed” system- activities that occurs when the body is at rest, especially after eating,

including sexual arousal, salivation, lacrimation, urination, digestion and defecation

- it functions with actions that do not require immediate reaction

Sympathetic Division- Stressful, Action Division- usually speeds up actions like heart rate, blood pressure, breathing

rate- “fight or flight” system- the sympathetic division typically functions in actions requiring quick

responses- preparing the body for intense, energy-consuming activities, such as

fighting, fleeing, or competing in a strenuous game

• An automatic reaction without thinkinghappens quickly in less than a second.

Reflex arc (Withdrawal)

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The Endocrine System

Endocrine System• “internal” glands of secretion

that release a hormone into thebloodstream, right within thegland itself

• influences the metabolic activityby means of hormones (Gk.Hormon = to excite), which arechemical messengers releasedinto the blood to be transportedthroughout the body

• is instrumental in regulatingmetabolism, growth anddevelopment, reproduction andcomplex behaviors includingparts of our mood, courtshipand migration.

• is the slow message system ofyour body

Activity of a Hormone-Secreting Cell

ENDOCRINOLOGY

ENDOCRINE GLANDS

Functions:-Regulation of metabolism & nutrient supply- reproduction and sexual differentiation- development and growth- maintenance of the internal environment

HORMONES

-Lacks the ducts- discrete organs for production and secretion of chemical substances

Chemically, the hormones are of 3 types

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•Derivatives of the amino acid tyrosine

e.g. Thyroxine (T4), Triiodothyronine (T3),Epinephrine and Norepinephrine

•Proteins or peptides

e.g. Oxytocin, Luteinizing hormone (LH), Prolactin,Growth hormone (GH), Insulin, Glucagon

•Steroid hormones

are synthesized from cholesterol e.g. EstrogenProgesterone, Androgens, Mineralocorticoids,Glucocorticoids

Hypothalamus makes hormones that control the pituitary gland. In addition, it makes hormones that are stored in the pituitary gland.

Pineal gland releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles.

Thyroid produces thyroxine, which regulates metabolism.

Adrenal glandsrelease epinephrine and norepinephrine that help body deal with stress.

Pituitary gland produces hormones that regulate many of the other endocrine glands.

Parathyroid glandsThese four glands release parathyroid hormone, which regulate the level of calcium in the blood.

Thymusreleases thymosinduring childhood that stimulates T cell devt

Testis produce testosterone responsible for sperm production and the development of male secondary sex characteristics

Ovary produces estrogen and progesterone. Estrogen is necessary for development of secondary sex characteristics and eggs. Progesterone prepares the uterus for a fertilized egg.

PancreasThe pancreas produces insulin and glucagon, which regulate the level of glucose in the blood.

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Hypothalamus

• The main controlcenter of theendocrine system

• makes hormones thatcontrol the pituitarygland.

• In addition, it makeshormones that arestored in the pituitarygland

Pituitary Gland

• pea-sized glandconsisting of twodistinct parts: aposterior lobe and ananterior lobe, bothsituated in a pocket ofskull bone just underthe hypothalamus

• produces hormonesthat regulate many ofthe other endocrineglands

Pineal Gland

• a pea-sized mass oftissue near the centerof the brain

• releases melatonin,which is involved inrhythmic activities,such as daily sleep-wake cycles

Thyroid Gland

• located in the neckjust under yourlarynx (voice box)

• produces thyroxine,which regulatesmetabolism.

Thymus

• lies under thebreastbone inhumans

• releasesthymosin duringchildhood thatstimulates T celldevt

Parathyroid Gland

• These four glandsrelease parathyroidhormone, whichregulate the level ofcalcium in theblood

Adrenal Gland

• one sitting on top ofeach kidney

• release epinephrineand norepinephrinethat help body dealwith stress.

Pancreas

• The pancreasproduces insulinand glucagon,which regulate thelevel of glucose inthe blood

Testes• produce testosterone

responsible for spermproduction and thedevelopment of malesecondary sexcharacteristics

Ovaries• produces estrogen

and progesterone.

• Estrogen is necessaryfor development ofsecondary sexcharacteristics andeggs.

• Progesteroneprepares the uterusfor a fertilized egg.

Concept Map

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Hypothalamus and Pituitary gland • Hypothalamus – in vertebrates,this is part of the brain and helpsregulate the internal environment ofthe body; for example in the controlof heart rate, body temperature andwater balance. This also controls theglandular secretions of the pituitarygland

• Pituitary gland- this is a smallgland that lies just inferior to thehypothalamus; this consist of theanterior and posterior pituitary bothproduce hormones. It is also calledthe “master gland” because manyof its hormones regulate the otherendocrine function

Actions of Insulin and Glucagon

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Liver converts glucose to glycogen

The Menstrual Cycle

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Principal Endocrine Glands & Hormones in the body

Endocrinegland

Hormones released TargetTissues/Organs

Function(s) of Hormone

Hypotha-lamus

Hypothalamic-realeasing and

releasing inhibiting

Anterior pituitary Regulate anterior pituitary hormones

Posterior pituitary

Antidiuretic (ADH)

Oxytoxin

Kidney

Uterus, mammary gland

Stimulates water reabsoprtion by kidneys

Stimulates uterine muscle contraction, release of

milk by mammary glands

Anteriorpituitary

Thyroid-stimulating(TSH)

Adrenocortico-trophic (ACTH)

Gonadotrophic(follicle

stimulating,FSH)

Thyroid

Adrenal Cortex

Gonads

Stimulates thyroidhormone

Synthesis adrenal cortex

Egg and sperm production and sex

hormones

Anteriorpituitary

Luteinizinghormone (LH)

Gonads Egg and sperm production and sex

hormones

Prolactin (PRL) Mammary glands

Milk production

Growth (GH) Soft tissues,bones

Cell division, protein synthesis and bone

growth

Melanocyte stimulating (MSH)

Melanocytes in skin

Unknown function in humans

Regulates skin color in lower vertebrate

Thyroid Thyroxine (T4) and

triiodothyronine (T3), Calcitonin

All tissuesBones,kidneys,

intestine

IncreaseLowers blood calcium

level

Thymus Thymosin Stimulates T cell development

Endocrinegland

Hormones released TargetTissues/Organs


Para-thyroid

Parathyroid (PTH)

Bones, kidneys, intestine

Raises calcium in blood

Adrenalcortex

Glucocorticoids (cortisol)

All tissues Raise blood glucose level; stimulate

breakdown of protein

Mineralcorticoids (cortisol)

All tissues Reabsorb sodium and excrete potassium

Sex hormones Gonads, skins,muscles, bones

Stimulatereproductive organs

Adrenalmedulla

Epinephrine and

nonepinephrine

Cardiac and other muscles

Emergency situations; raise

blood glucose level

Endocrinegland

Hormonesreleased

TargetTissues/Organs


Pancreas Insulin Liver, muscles, adipose tissues

Lowers blood glucose level; promotes

formation of glycogen

Glucagon Liver, muscles, adipose tissues

Raises blood glucose level

Testes Androgens (testosterone)

Gonads, skins,muscles, bones

Stimulates secondarymale sex characteristics

Ovaries Estrogens and

progesterone

Gonads, skins,muscles, bones

Stimulates female sex characteristics

Pineal gland

Melatonin Brain Circadian and circannal rhythms; possibly

involved in maturation of sex organs

Endocrinegland

Hormonesreleased

Target Tissues/ Organs


Endocrine Diseases and Disorders

Disease Effects of deficiency/excess

Diabetes mellitus(Type I)

is characterized by destruction of the beta cells of the islets of Langerhans and a complete lack of insulin.

Diabetes mellitus(Type II)

insulin is produced but cannot exert its effects because of a deficiency of insulin receptors on cell

membranes

Diabetes insipidusDeficiency of vasopressin, one of the antidiuretichormones (ADH) thus, abnormal increase in urine

output

Hyperthyroidism

Underactive thyroid gland, cause myxedema and cretinism, known as congenital hypothyrodism.

Characterized by enlargement of the thyroid gland, most often called thyroid goiter

Grave’s diseasean autoimmune disease in which specific antibodies are produced , producing an excessive amount of

thyroid hormones

Endocrine Diseases and Disorders

Hypocalcaemia when the blood levels of calcium are low

Hypoparathyroidisminsufficient secretion of parathyroid hormones

which leads to increased nerve excitability

Addison’s disease

Decreased function of the adrenal cortex result toweakness, fatigue, abdominal pains, nausea,

dehydration, fever and hyperpigmentation (tanning withought sun exposure) are among the symptoms

Cushing’s Syndrome

Excessive secretion of glucocorticoids; corticosteroid produced by the adrenal glands

Hypoglycemiathe clinical syndrome that results from low blood

sugar

Acromegaly and gigantism

Both are caused by a pituitary tumor that stimulates production of excessive growth

hormone, causing abnormal growth in particular parts of the body

Pituitary dwarfismGrowth hormone deficiency in children results in

slowed long bone growth

Hyperthyroidism

Grave’s disease

Gigantism

Pituitary dwarfism

Nervous system

Science

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