BIOL 3151: - PowerPoint Presentation

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BIOL 3151: Principles of Animal Physiology

ANIMAL PHYSIOLOGY

Dr. Tyler EvansEmail: tyler.evans@csueastbay.eduPhone: 510-885-3475Office Hours: M,W 10:30-12:00 or appointmentWebsite: http://evanslabcsueb.weebly.com/Slide2

LAST LECTURE

Why do squid have giant axons?

axons that activate muscles at the far end of the mantle have VERY LARGE DIAMETERSaxons that activate muscles in the region of the mantle closest to the central nervous system have smaller diameterscombining axons of various diameters allows the near-simultaneous contraction of the mantleSlide3

LAST LECTURE

TRADE-OFFS OF GIANT AXONS?

although increasing axon diameter provides increases in conduction velocity, there are two main disadvantages to using large axons to increase conduction velocity:

Large axons

take up more space

and this may limit the number of neurons that can be packed into the nervous

system

Large diameter axons have a much larger volume of cytoplasm per unit length, making them energetically expensive to make and maintain.Slide4

LAST LECTURE

true myelin sheaths were

an important evolutionary innovationallowed rapid signal conduction in a small amount of spacehelped to provide conditions for complex vertebrate nervous systemsmore complex nervous systems allowed animals to evolve more complex behavior, physiology, social systems, etc.

Lampreys/Hagfish

(no myelin)

Mammals

(lots of myelin)

MYELIN SHEATHSSlide5

LAST LECTURE

ELECTRICAL VS CHEMICAL SYNPASES

ELECTRICAL SYNAPSES and CHEMICAL SYNAPSES differ in a number of ways:DIRECTION OF FLOW OF INFORMATIONin

electrical synapses, information can flow in

BOTH

DIRECTIONS

because

pre- and post-synaptic cells are directly connectedSPEEED OF TRANSMISSIONelectrical synapses are fast

chemical synapses are slower because of delays associated with the diffusion of neurotransmitters across the synaptic cleft and their binding to receptors on the post-synaptic neuronSlide6

TWO EXCELLENT STUDENT QUESTIONS FROM NEUROPHYSIOLOGY LECTURES

Does the thickness of myelin differ between axons?

YES!vertebrates have axons that vary in diameter, though not to the same degree as we see in squidl

arge diameter axons have thick myelin sheaths and small diameter axons have thin myelin sheaths

r

atio between axon diameter and myelin thickness is constant (0.6-0.7)

http://www.nature.com/scitable/topicpage/myelin-a-specialized-membrane-for-cell-communication-14367205Slide7

TWO EXCELLENT STUDENT QUESTIONS FROM NEUROPHYSIOLOGY LECTURES

2. Which type of synapse is more energetically demanding: chemical or electrical?

chemical synapse require more energy due to formation and transport of SYNAPTIC VESICLESvesicles can be recycled, but still more energy demanding

http://www.albany.edu/faculty/cafrye/apsy601/Ch.04feb10,psychopharmacology.htmlSlide8

TODAY’S LECTURECELLULAR MOVEMENT AND MUSCLES

muscles are a distinctive cell type found only in animals

simplest animals lack true muscles, but do have cells that contractwhat’s full of holes but can hold water?Slide9

CELLULAR MOVEMENT AND MUSCLES

muscle-like cells first arose in Cnidarians such as

Hydrathe Hydra uses MYOEPITHELIAL CELLS to support and extend their body stalkSlide10

CELLULAR MOVEMENT AND MUSCLES

true muscles first appeared in a group of animals call ctenophores (comb jellies)

c

tenophores like sea walnuts (right) and sea goose berries have true smooth muscles in their bodies walls that they use for locomotionSlide11

CELLULAR MOVEMENT AND MUSCLES

although these primitive animals have several different types of muscles, complex animals display much greater diversity in muscle anatomy and

physiology the greatest muscle diversity occurs in the vertebrateswith the transition to land and the challenges of movement under the full weight of gravity, muscle diversified rapidly and became specialized for many different processes

Tiktaalik

fossil represents an important group of vertebrates involved in the transition toward life on land Slide12

CELLULAR MOVEMENT AND MUSCLES

regardless of the type of movement, the same intracellular machinery underlies each one

a quote from your textbook: “when you marvel at the athleticism of a cheetah sprinting, a tuna swimming or a hummingbird hovering, remember these impressive capacities depend on cellular machinery not unlike that found in the fungus growing on your shower curtain” Slide13

CELLULAR MOVEMENT AND MUSCLES

common machinery is the CYTOSKELETON

and associated MOTOR PROTEINSmicrotubules and microfilaments are most important of these componentsdiversity in cellular movement is possible because these basic elements can be arranged and used in countless combinations

t

hree general ways cells use these elements to move:

1. use cytoskeleton like a “roadway” (most common)

m

otor proteins act as trucks carrying cargo over cytoskeleton roadways

e.g. transport of proteins between different organelles

cytoskeleton

cargo

Textbook Fig 5.1 pg 198

m

otor proteinSlide14

Textbook Fig 5.1 pg 198

CELLULAR MOVEMENT AND MUSCLES

2

. Cytoskeletal fibers act like a “bulldozer” to push cellular contents forward

o

ften referred to as

AMOEBOID

movement and is common in protists

e.g. cells involved in the immune response use amoeboid movementthree general ways cells use these elements to move:

cytoskeleton

cargo

m

otor proteinSlide15

CELLULAR MOVEMENT AND MUSCLES

3. Motor proteins pull a cytoskeleton rope

c

ells then reorganize in cytoskeleton so that this pulling translates into movement

e.g. these types of cytoskeletal structures are the basis of cilia, flagella and muscle

three general ways cells use these elements to move:

Textbook Fig 5.1 pg 198

cytoskeleton

cargo

m

otor proteinSlide16

CELLULAR MOVEMENT AND MUSCLES

MICROTUBULES and

MICROFILAMENTS are most important of components of cell movementsMICROTUBULES

m

icrotubules are so named because of their tube-like appearance and are composed of long strings of the protein

TUBULIN

, which is a dimer of two closely related proteins alpha (

α) tubulin and beta (β) tubulinthe first step of tubulin assembly occurs when

α and β-tubulin combineGTP (stored energy) is bound to α tubulinα and β-tubulin combine with a reaction that uses the stored energy of GTP

result

is

α

-tubulin now has a negative charge relative to

β

-tubulin

c

harge difference is key to assembly

Textbook Fig 5.4 pg 201Slide17

CELLULAR MOVEMENT AND MUSCLES

MICROTUBULES

like magnets, the positive and negative ends of tubulin attach to form a growing chain or PROROFILAMENTprotofilaments then line up to form a sheet that eventually rolls into a tube to form a complete

MICROTUBULE

Textbook Fig 5.4 pg 201Slide18

CELLULAR MOVEMENT AND MUSCLES

MICROTUBULES

most cells arrange their microtubules like spokes on a wheel, radiating out to the periphery of the cell from a central

MICROTUBULE ORGANIZING CENTER

c

ells use this microtubule network to control the movement of vesicles and

other cargo to different parts of the cell

“-” end of the microtubule is closest to the microtubule organizing center, while the “+” end is closest to the cell periphery

Textbook Fig 5.6 pg 202Slide19

CELLULAR MOVEMENT AND MUSCLES

MICROTUBULES

cells use this microtubule network to control the movement of vesicles and and other cargo to different parts of the celle.g. color change in camouflaged animals

Textbook Fig 5.3 pg 200

Xenopus

frog darkens its skin by transporting pigment granules from the

MICROTUBULE ORGANIZING

CENTER

to the periphery of the skin along microtubulesSlide20

CELLULAR MOVEMENT AND MUSCLES

MICROTUBULES

m

icrotubules are involved in

important

cell movements required for

survival

things like cell division, axon structure, movement of cilia and flagellaTextbook Table 5.1 pg 206Slide21

CELLULAR MOVEMENT AND MUSCLES

MICROTUBULES

microtubules are very sensitive to temperature: they will disassemble if too coldnot a problem for ENDOTHERMS (warm-blooded animals), but ECTOTHERMS (cold-blooded animals) can live in very cold environments (e.g. polar regions)

m

icrotubules assemble at lower temperatures in

ectotherms

from cold environments

requires only single mutation in tubulin gene to promote cold stability

animals in living in the Antarctic Ocean have adaptations that prevent microtubules from disassembling in the cold water (-2°C)Slide22

CELLULAR MOVEMENT AND MUSCLES

TRANSPORT USING MICROTUBULES

if microtubules are like roads, how does cargo know which direction to travel?orientation of α and β-tubulin give tubulin POLARITY (a charge difference)

t

he negative ends stay near microtubule organizing center and the positive ends stretch towards the cell periphery

MOTOR PROTEINS

(proteins that move along microtubules)

recognize this polarity and each motor protein moves in a characteristic direction

Textbook Fig 5.4 pg 201Slide23

CELLULAR MOVEMENT AND MUSCLES

motor proteins recognize this polarity and each motor protein moves in a characteristic direction:

KINESIN: moves along the microtubule in the POSITIVE directionDYNEIN: moves along the microtubule in the NEGATIVE direction

KINESIN

DYNEIN

TRANSPORT USING MICROTUBULESSlide24

CELLULAR MOVEMENT AND MUSCLES

e.g. neurotransmitters transport down axons

textbook Fig 4.16 pg 162

n

eurotransmitters are released at synapses to induce a response

n

eurotransmitters are carried from the cell body

(i.e. soma)

down the axon on microtubuleskinesin can transport neurotransmitters to the end of the synapse (+ direction)dynein then carries the empty synaptic vesicle back to the soma (- direction)

t

extbook Fig 5.7 pg 204

TRANSPORT USING MICROTUBULESSlide25

CELLULAR MOVEMENT AND MUSCLES

e.g. neurotransmitters transport down axons

TRANSPORT USING MICROTUBULES

t

extbook Fig 5.7 pg 204Slide26

CELLULAR MOVEMENT AND MUSCLES

MICROTUBULES

CILIA and FLAGELLA rely on microtubules to generate movementmicrotubules in cilia and flagella are arranged into a structure called the AXONEMEe

ach doublet microtubule around the periphery of the

axoneme

contains a dynein motor-a signal triggers dynein to stretch out and attach to negative end of neighboring tubulin, then pulls itself forward

b

y altering this movement between opposite sides of the axoneme, a whip-like movement is generated

t

extbook Fig 5.8 pg 205Slide27

CELLULAR MOVEMENT AND MUSCLES

MICROFILAMENTS

microfilaments are the other type of cytoskeletal element used in movementalso involved in transport within cells, but in cell shape changes and moving from place to placemicrofilament

based

movement uses

ACTIN

and the motor protein MYOSINmicrofilaments are composed of long string of ACTIN

microfilaments form in much the same way microtubules: “+” and “-” ends of actin assemble

actin

monomers are termed

G-ACTIN

“G” stands for globular

referred

to as

F-ACTIN

when in polymers

“F” stands for filamentousSlide28

CELLULAR MOVEMENT AND MUSCLES

MICROFILAMENTS

actin polymerization (formation of F-actin) can generate cell movementimportant in two types of amoeboid movement in cells:1. FILIPODIA: thin extensions of cells

digestive

cells use

filipodia

to build microvilli

c

ells of the small intestine use microvilli to increase surface areas of cells responsible for absorbing nutrients from foodSlide29

CELLULAR MOVEMENT AND MUSCLES

MICROFILAMENTS

actin polymerization (formation of F-actin) can generate movementimportant in two types of amoeboid movement in cells:

2. LAMELLIPODIA

:

are sheet-like protrusion of the cell and are involved

in cell migration, for example during development

LamellipodiumSlide30

CELLULAR MOVEMENT AND MUSCLES

MICROFILAMENTS

sperm also use actin polymerization during fertilizationfertilization depends on sperm controlling growth of actin toward the eggsperm use actin polymerization to push an extension of their plasma membrane into the egg

o

nce this occurs the sperm can transfer nuclear DNA to the egg

Textbook Fig 5.11 pg 208Slide31

CELLULAR MOVEMENT AND MUSCLES

MICROFILAMENTS

although possible to use actin polymerization for movement, in most situations microfilaments are used in combination with motor protein MYOSINthere are many ISOFORMS of myosin (17 actually), but the structure is similar in diverse organisms: head, tail, neck

HEAD

: possesses ATPase activity, which provides the energy required for movement

NECK

: allows regulatory proteins to bind to myosin and modify its activity

TAIL

: binds cargo, like vesicles, organelles, or membranes

Textbook Fig 5.12 pg 209Slide32

CELLULAR MOVEMENT AND MUSCLES

MICROFILAMENTS

MOTOR PROTEINS like MYOSIN (but also KINESIN and DYNEIN) use ATPase activity to convert the energy stored in ATP into mechanical energy.

t

he series of events that culminate in actin-myosin based movement is called the

SLIDING FILAMENT MODEL

t

his model can be used to describe many different types of movement involving myosin from vesicular transport to muscle contraction

A useful analogy for actin-myosin based movementSlide33

CELLULAR MOVEMENT AND MUSCLES

MICROFILAMENTS

WHAT DOES THE ROPE REPRESENT?WHAT DOES YOUR ARMS REPRESENT?WHAT DO YOUR HANDS REPRESENT?WHICH PART REQUIRES MOST ATP?Slide34

CELLULAR MOVEMENT AND MUSCLES

SLIDING FILAMENT MODEL

the myosin molecule extends by straightening its NECK (i.e. arms extending)the myosin HEAD then forms a bond with the actin filament (i.e. hands grasping onto the rope)

t

his strong interaction between actin and myosin is called a

CROSS BRIDGE

m

yosin bends and pulls the actin filament towards its tail (i.e. pull up)this step is called the POWER STROKE

HEAD then uncouples from actin and myosin returns to the resting unattached position

Actual movement depends on whether it is actin or myosin that is free to move

if rope attached, you will pull yourself (myosin is mobile)

If rope not attached, you will pull the rope (actin is mobile)

Textbook Fig 5.12 pg 209Slide35

CELLULAR MOVEMENT AND MUSCLES

1. UNITARY DISPLACEMENT-corresponds to the distance myosin steps during each cross bridge cycle

in rope analogy, depends on length of armsfor myosin depends of length of the NECKmyosin step are variable, but on average cover 36 nm per step

Textbook Fig 5.12 pg 209

Unitary

displacementSlide36

CELLULAR MOVEMENT AND MUSCLES

SLIDING FILAMENT MODEL

ATP provides the chemical energy for the movement of actin and myosinthe hydrolysis of ATP causes the neck of myosin to extend forward and grasp further up the actin filamente

nergy released from this hydrolysis allows myosin to pull actin filament

t

he head remains attached until another ATP binds, which causes neck to extend once again.

i

f no ATP present remains myosin head remains attached to actin. This is the cause of RIGOR MORTISanimal dies, ATP is depleted and muscle remain locked Slide37

LECTURE SUMMARY

muscles are a distinctive cell type found only in animals: true muscles first appeared in a group of animals call

CTENOPHORES (comb jellies).regardless of the type of movement, the same intracellular machinery underlies each onemicrotubules and microfilaments are most important components of cellular movement

orientation

of

α

and

β-tubulin give microtubules POLARITY (a charge difference) and microtubule motor proteins (

kinesin, dynein) recognize this polarity and each motor protein moves in a characteristic directionfoundation of microfilament based movement is ACTIN and the motor protein MYOSINthe series of events that culminate in actin-myosin based movement is called the

SLIDING FILAMENT

MODEL

UNITARY

DISPLACEMENT

-corresponds to the distance myosin steps during each cross bridge

cycleSlide38

NEXT LECTURE

Muscle Structure and Regulation of Contraction