Nervous System

(1)

3. Functional

Organization Of Nervous System, Hormone And

Cell Signalling

(2)

A. ANIMAL

COORDINATION

(NERVOUS SYSTEM)

(3)

Topic :

A.

Neuron : Structure and

Conduction of nerve Impulse

B.

Comparing Animal Nervous System

C.

All or None principle

D.

Chemistry Impulse

(Endocrinology)

(4)

A. Neurons

Structure and Conduction of a

Nerve Impulse

(5)

Two coordinating systems which respond to environmental stimuli

Nervous System & Endocrine (hormone) System

Begin with Nervous System (data processing system) 3 interconnected functions  input / integration / output

(6)

Basic Organization

• Sensory Input triggered by stimuli

– conduction of signals to processing center

• Integration

– interpretation of sensory signals within processing centers

• Motor output

– conduction of signals to effector cells (i.e. muscles, gland cells)

sensory receptor (sensory input)  integration  (motor output)

 effector

(7)

Neuron

 Dendrite - conducts “signal” toward the cell body -- [input zone]

◦ often short, numerous & highly branched

◦ signal comes from sensory cell or neighboring neuron

 Axon - usually a single fiber -- [conducting zone]

◦ conducts signal away from cell body to another neuron or effector cell

 Axon Ending

◦ a cluster of branches (100’s to 1000’s)

◦ each with a bulblike synaptic knob

◦ relays signal to next neuron / effector cell

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Generation - Conduction of Neural Impulses

• Dependent on concentration gradients of Na⁺ & K⁺

–Na⁺ 14x greater outside –K⁺ 28x greater inside

• Membrane permeability

–lipid bilayer bars passage of K⁺ & Na⁺ ions –protein channels and pumps regulate

passage of K⁺ & Na⁺

• at rest more K⁺ move out than Na⁺ move in

• K⁺ ions diffuse out leave behind excess negative charge

• Sodium-potassium pump

–Na⁺ out - K⁺in (more Na+ out than K⁺ in –contributes to loss of (+)

(9)

Overview of Neural Impulse

(10)

 Maintenance of negative charge within neuron

◦ resting membrane potential about -70 millivolts

◦ [5% voltage of AA battery]

 Dissolved organic molecules [negative charge] kept inside

 Na⁺ - K⁺ balance

(11)

• Stimulus causes opening of Na⁺ gates

& closing of K⁺ gates -

• Threshold [~ +30 mV]

–all - or - nothing response

• Action potential localized electrical event

• Changes permeability of region immediately ahead

–changes in K⁺ & Na⁺ gates –domino effect

–propagation of signal (perambatan)

• Intensity of stimuli (i.e. pinch vs.

punch) = number of neurons firing

• Speed on impulse based on diameter of axon & amount of myelination [wire for internet]

(12)

(13)

Myelin Sheath

 Resembles chain of beads

 Prevents ions from flowing through membranes

 Na⁺ channels highly concentrated at nodes

 Allows signal to travel faster because impulse “jumps”

from node of Ranvier to

node of Ranvier (with myelin sheath (225 mph / without 11 mph)

 MS  destruction of mylin sheath by own immune

system (progressive loss of signal conduction, muscle control & brain function)

(14)

Neurons Communicate at Synapses

• Electrical [no synapse]

– common in heart & digestive tract - maintains steady, rhythmic contraction

– All cells in effector contain receptor proteins for neurotransmitters

• Chemical - skeletal muscles & CNS

– presence of gap (SYNAPTIC CLEFT) which prevents action potential from moving directly to receiving neuron

– ACTION POTENTIAL (electrical) converted to CHEMICAL SIGNAL at synapse (molecules of neurotransmitter) then generate ACTION

POTENTIAL (electrical) in receiving neuron

(15)

Overview of Transmission of Nerve Impulse

• Action potential

 synaptic knob

 opening of Ca⁺channels

neurotransmitter vesicles fuse with membrane

release of neurotransmitter into synaptic cleft

binding of neurotransmitter to protein receptor molecules on receiving neuron membrane

opening of ion channels

triggering of new action potential

• Neurotransmitter is broken down by enzymes &

ion channels close -- effect brief and precise

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Nerve Impulse

 Presynaptic neuron

 Vesicles

 [Calcium channels]

 Synaptic cleft

 Postsynaptic neuron

 Neurotransmitter receptor

(17)

Nerve Impulse

 Action potential

 synaptic knob

 opening of Ca⁺ channels

release of

neurotransmitter into synaptic cleft

Ca²⁺

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Nerve Impulse

release of

neurotransmitter into synaptic cleft

(19)

binding of

neurotransmitter to protein receptor

molecules on receiving neuron membrane

opening of sodium (Na) channels

triggering of new action potential

(20)

Neurotransmitters

• Catecholamine Neurotransmitters

–Derived from amino acid tyrosine

• Dopamine [Parkinson’s], norepinephrine, epinephrine

• Amine Neurotransmitters

–acetylcholine, histamine, serotonin

• Amino Acids

–aspartic acid, GABA, glutamic acid, glycine

• Polypeptides

–Include many which also function as hormones –endorphins

(21)

• Transmission of signals based on MULTIPLE STIMULI

– combined excitatory & inhibitory neurons

• Inhibition in Pre-synaptic neuron

– Ca⁺ channels blocked

• stops release of neurotransmitter

• Inhibition in Post-synaptic neuron

– opens Cl- channels

• makes interior more [-]

• increase permeability of K⁺ ions

– makes interior more [-]

(22)

B. Comparing Animal

Nervous Systems

(23)



Compare them



Ask:

◦What does a nervous system need to do?

◦How does a particular animal’s nervous system do this?

How do animal nervous systems

differ?

(24)



Input

◦Sensory neurons



Decision-making

◦Interneurons



Output

◦Motor neurons

(25)

 Nine “traditional” taxonomic phyla:

 Porifera - sponges

 Cnidaria - jellyfish

 Platyhelminthes - flatworms

 Nematoda - roundworms

 Annelida - segmented worms, hirudinae, L.terestroides

 Arthropoda - crustaceans, arachnids, insects

 Mollusca - squid, etc.

 Echinodermata - starfish, sea urchins

 Chordata - includes vertebrates

What kinds of animals are there?

(26)



What kinds of sensory input?



What kinds of decision making?



What kinds of response?

What to ask about each phylum?

(27)



Light - photons



Chemicals - (food/poison/mate) molecules



Sound/touch - pressure waves

What kinds of sensory input?

(28)



Photoreceptors (lightbulb wingding)



Simple light detectors:

eye-cups ocellli

omatidia eyes

Light:

(29)



Chemoreceptors

◦Food - (webding banana)

◦Poison - (webding bomb)

◦Mate - (webding heart)

Chemicals:

(30)



Chemoreceptors

◦Simpler animals: localized in several places on animal’s surface

◦More complex animals:

concentrated at head

 (e.g. smell/taste @ nose/mouth)

Chemicals:

(31)



Pressure waves

◦Air - moving air molecules

◦Water - moving water molecules

◦Touch - physical contact (predator/prey/mate)

Sound/touch:

(32)



Mechanoreceptors (hand/speaker wingdings)



Usually contain cilia that trigger when moved



Simpler animals:

◦Distributed throughout surface



More complex animals:

◦Surface (e.g. skin)

◦Localized (e.g. lateral line, ears)

Sound/touch

(33)



Choosing an appropriate response:

◦E.g. fight/flight/mating/homeostasis



Requires interneurons:

◦Direct the sensory input to the output

Decision making:

(34)



Simpler animals - not present



More complex animals:

◦Central nervous system:

 Brain - located at the front (head)

 Spinal cord - runs down the center, branches off where needed

Interneurons

(35)



Motor neurons:

◦Trigger response - (usu. Movement)

Rapid Response

(36)



Identify the sensory neurons:

◦Photoreceptors (lightbulb wingding)

◦Chemoreceptors

(banana/bomb/heart wingding)

◦Mechanoreceptors (hand/speaker wingdings)

For each animal:

(37)

 Common name: moon jellyfish

 Species: Aurelia

 Phylum: Cnidaria

(38)

 Common name: moon jellyfish

 Species: Aurelia

 Phylum: Cnidaria

(39)

 Common name: planarian

 Species: dugesia

 Phylum: platyhelminthes

(40)

 Common name: planarian

 Species: dugesia

 Phylum: platyhelminthes

(41)

 Common name: C. elegans (a roundworm)

 Species: C. elegans

 Phylum: Nematoda

(42)

 Common name: C. elegans (a roundworm)

 Species: C. elegans

 Phylum: Nematoda

(43)

 Common name: Earthworm

 Species: Lumbricus

 Phylum: Annelida

(44)

 Common name: Earthworm

 Species: Lumbricus

 Phylum: Annelida

(45)

 Common name: Crayfish

 Species: Procambarus

 Phylum: Arthropoda (crustaceans)

(46)

 Common name: Crayfish

 Species: Procambarus

 Phylum: Arthropoda (crustaceans)

(47)

 Common name: Garden spider

 Species: Argiope

 Phylum: Arthropoda (arachnida)

(48)

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QuickTime™ and a TIFF (Uncompressed) decompressor

are needed to see this picture.

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QuickTime™ and a

TIFF (Uncompressed) decompressor are needed to see this picture.

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 Common name: grasshopper

 Species: romalea

 Phylum: Arthropoda (insects)

(53)

 Common name: grasshopper

 Species: romalea

 Phylum: Arthropoda (insects)

(54)

 Common name: Squid

 Species: Lolliguncula

 Phylum: Mollusca

(55)

 Common name: Squid

 Species: Lolliguncula

 Phylum: Mollusca

(56)

 Common name: Starfish

 Species: Asterias

 Phylum: Echinodermata

(57)

 Common name: Starfish

 Species: Asterias

 Phylum: Echinodermata

(58)

 Common name: Frog

 Species: Rana pipiens

 Phylum: Chordata

(59)

 Common name: Frog

 Species: Rana pipiens

 Phylum: Chordata

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 Campbell Biology, 6th edition (2002)

◦ Ch. 33 Invertebrates (p.646-77)

◦ Ch. 34 Vertebrate Evolution and Diversity (p.678-717)

◦ Ch. 48 Nervous Systems (p.1038-51)

◦ Ch. 49 Sensory and Motor Mechanisms (p.1057-84)

 Invertebrate Zoology, a Functional

Evolutionary Approach, 7th ed. (2004) Ruppert EE, Fox RS, Barnes RB. Brooks Cole Thomson, 963 pp.

For further reading:

(61)

C. ENDOCRINE SYSTEM

CHAPTER 5

(62)

Communication Chemical



Main Function:

It releases hormones into the blood to

signal other cells to behave in certain

ways. It is a slow but widespread form

of communication.

(63)

Endocrine system in Invertebrate

Several of the hormones in

invertebrates are neurohormones,

that is, they are produced by nerve

cells.

(64)

Insects



Increase in linear dimensions of an insect can only occur at periodic

intervals when the restricting

exoskeleton is shed during a process known as molting  ganti kulit/bulu



The orderly sequence of molts that leads from the newly hatched insect to the adult is controlled by three

hormones

(65)

Crustaceans

Higher crustaceans have a structure, the sinus gland, which in most stalk- eyed species lies in the eyestalk and

is the storage and release site of a

molt-inhibiting hormone

(66)

Annelids



Strong evidence for hormones in annelids has been obtained from studies of the reproductive system



One substance that has been found in some marine annelids inhibits

maturation of the gametes



substance was thought to have been

produced by the brain

(67)

Echinoderms



The radial nerves of starfishes contain two substances that are required for the maintenance of a normal reproductive cycle



One, the shedding substance,

induces spawning. The second,

shedhibin, inhibits the former.

(68)

Mollusks

 The best-established endocrine organs in mollusks, the optic glands, occur in the octopus and squid

 . They are a pair of small structures, found near the brain, that produce a substance which causes gonadal

maturation

 The optic glands in turn are regulated by inhibitory nerves from the brain.

(69)

Endocrine glands

Release hormones into the bloodstream.

Hormones are chemicals released in one part of the body that travel through the bloodstream and

affect the activities of cells in other parts of the body.

Consists of:

HUMAN Endocrine System

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Endocrine System in Vertebrate

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THE END