BIOL 3151: Principles of Animal Physiologyevanslabcsueb.weebly.com/uploads/1/2/1/9/12193389/...• animal circulatory systems have threemain components required for bulk flow: 1. A

BIOL 3151:

Principles of Animal

Physiology

ANIMAL

PHYSIOLOGY

Dr. Tyler EvansEmail: [email protected]

Phone: 510-885-3475

Office Hours: F 8:30-11:30 or appointment

Website: http://evanslabcsueb.weebly.com/

PREVIOUS LECTUREMUSCLE DIVERSITY

• the frequency that these SONIC MUSCLES contract is impressive considering

potential time consuming cellular events that could delay contraction, such as

refractory periods and formation of myosin-actin cross bridges

• surprisingly, the contractile machinery of sonic muscles is not that different from

skeletal muscle

So what makes sonic muscles able to contract and relax so

quickly?

SOUND PRODUCING ORGANS

PREVIOUS LECTUREMUSCLE DIVERSITY

SOUND PRODUCING ORGANS

1. ENHANCED ABILITY TO CYCLE CALCIUM

2. FAST CROSS-BRIDGE CYCLING

3. SHORTENED SARCOMERE LENGTH BEYOND LIMITS

SEEN IN OTHER ANIMALS

TODAY’S LECTURE

CARDIOVASCULAR PHYSIOLOGY

Circulatory system of a crab

Chapter 8

pg 348-409

TODAY’S LECTURECHARACTERISTICS OF CIRCULATORY SYSTEMS

• circulatory systems transport oxygen and nutrients to actively metabolizing tissues

and remove carbon dioxide and other waste products

• unicellular organisms and some multicellular organisms lack circulatory systems

and instead rely upon diffusion to transport molecules form place to place

• although diffusion can be rapid

over short distances, it is very

slow over long distances

• even a small molecule like

glucose take about 5 seconds to

diffuse across the length of a cell

• about 60 years to diffuse from

the heart to the feet

textbook Fig 8.1 pg 216

CARDIOVASCULAR PHYSIOLOGYCHARACTERISTICS OF CIRCULATORY SYSTEMS

• to overcome the limitations of diffusion animals use BULK FLOW to move fluids

through their bodies

• human circulatory system can move 1 ml of blood from the heart to the feet

and back again in about 60 seconds

• animal circulatory systems have three main components required for bulk flow:

1. A pump to apply the force necessary to drive fluid flow

2. A system of tubes, channels or spaces through which fluid can flow

3. A fluid that circulates through the system

• despite these basic components being present in all animal circulatory systems,

there is substantial diversity in the structure and organization of each of these

components

• “UNITY IN DIVERSITY” again…


• circulatory systems can either be OPENED or CLOSED

• in a CLOSED circulatory system, fluid remains within blood vessels at all points and

substances must diffuse across the walls of blood vessels to enter tissues

• in an OPEN circulatory system, fluid enters a SINUS (space) at some point and

there comes into direct contact with tissues allowing exchange

• there is often uncertainty as to which type of system an animal possesses

Circulatory system of a crab

• decapod crustaceans have both

sinuses and fine branching blood

vessels. Their circulatory systems

are usually classified as open, but

like closed systems, diffusion can

across the membrane of some fine

blood vessels

CHARACTERISTICS OF CIRCULATORY SYSTEMS

CARDIOVASCULAR PHYSIOLOGYDIVERSITY IN CIRCULATORY SYSTEMS

1. Sponges, cnidarians and flatworms• lack a circulatory system that transports an internal fluid, but all nonetheless

have mechanisms for propelling fluids around their bodies

• sponges propel water

through the bodies using

specialized cells called

CHOANOCYTES that have

rhythmically beating

flagellae



1. Sponges, cnidarians and flatworms• lack a circulatory system that transports an internal fluid, but all nontheless


• cnidarians propel water

(carrying oxygen and food

with it) from the external

medium through their

mouths into a

gastrovascular cavity using

muscular contractions.



1. Sponges, cnidarians and flatworms• lack a circulatory system that transports an internal fluid, but all nontheless


• Flatworms

(Platyhelminthes) also

have a gastrovascular

cavity, which is often lined

with FLAME CELLS whose

CILIA propel water to all

parts of the body



2. Nematodes• also lack a specialized circulatory system

• but can move fluid through their body cavities by contracting the muscles in their

body walls.

• are rarely more than 1 mm thick and primarily obtain oxygen via diffusion

• Instead, bulk flow is used for transporting signaling molecules and immune cells

• The nematode

Caenorhabditis elegans is

an important laboratory

model system


2. Annelids• tubeworms, earth worms and leeches are generally able to circulate body fluids

using cilia or muscular contractions of the body wall

• some rely solely on this mechanism

• e.g. some POLYCHAETE WORMS



2. Annelids• Classified as open, but the majority also possess a system of blood vessels that

circulates body fluid

• have a series of small vessels that connect two large vessels running the length of

the animal

• five simple tube like hearts propel blood down the ventral blood vessel

• the dorsal blood vessel itself is contractile and moves blood from the ventral

blood vessel back to the five hearts



3. Molluscs• all have hearts or contractile organs and most have blood vessels

• almost all molluscs have open circulatory systems

• e.g. CLAMS-have open circulatory systems



3. Molluscs• some cephalopods (squid, octopus, cuttlefish) have evolved completely closed

circulatory systems

e.g. squid and octopus

• possess three muscular hearts

• the single SYSTEMIC HEART

pumps oxygenated blood to

the body

• after passing through body

tissues, deoxygenated blood

flows into the two BRANCHIAL

HEARTS that pump blood

through gills to be-re-

oxygenated

• re-oxygenated blood then

flows back to the systemic

hearttextbook Fig 8.5 pg 354


4. Arthropods• almost all have one or more hearts and at least some blood vessels, but none can

be considered completely closed

a. CRUSTACEANS

• again lots of variation within this group of arthropods

• brachiopod crustaceans like the fairy shrimp have a simple tubular heart that may

extend almost the entire length of the body and only a few blood vessels



4. Arthropods• almost all have one or more hearts and at least some blood vessels, but none can


a. CRUSTACEANS

• in contrast, lobsters, crabs and crayfish have a single muscular heart and an

extensive network of blood vessels. These blood vessels branch out from the

heart and eventually empty into several sinuses deep within tissues

• after passing through tissues, blood drains into a sinus near the gills where it is re-

oxygenated prior to returning to the heart


• blood enters the heart though

small holes that can be opened

or closed called OSTIA

DIVERSITY IN CIRCULATORY SYSTEMS4. Arthropods• almost all have one or more hearts and at least some blood vessels, but none can


b. INSECTS

• in many insects, the only hint of a circulatory system is a large dorsal vessel that

extends the length of the body

• parts of the blood vessel are contractile and acts as hearts, one per segment


• the hearts pump the blood toward the

head emptying into a sinus near the brain

• normal body movements help move the

blood through other sinuses before

returning to the heart via ostia

• may also have accessory pumping organs in

their wings, antennae or limbs

• can end up with dozens of small hearts


DIVERSITY IN CIRCULATORY SYSTEMS4. Chordates• vertebrates belong to the Phylum Chordata, which also contains the urochordates

(tunicates) and cephalochordates (lancets)

• a simple heart propels fluid through a series of well-defined channels within

tissues

• these channels lack walls, so the circulatory system of urochordates and

cephalochordates is considered open.

• in contrast, vertebrates have closed circulatory systems in which the blood

remains within vessels at all points in its passage through the body


• the tunicate Ciona or

sea squirts


DIVERSITY IN CIRCULATORY SYSTEMS


CLOSED CIRCULATORY SYSTEMS EVOLVED INDEPENDENTLY MULTIPLE

TIMES• evolved independently in the vertebrates, cephalopod molluscs and annelid

worms

• examples of convergent evolution

• closed circulatory systems provide two main advantages over open systems:

1. ability to generate high pressure and flow rates

2. ability to better control and direct blood flow to specific tissues

• these features are important for oxygen delivery to metabolically active tissue and

closed systems tend to be found in highly active organisms or those living in low-

oxygen environments

VERTEBRATE CIRCULATORY SYSTEMS


• jawed vertebrates (not including hagfish and lampreys) share a common

circulatory plan:

• a systemic heart pumps blood through ARTERIES that carry blood away form the

heart. These arteries branch into smaller ARTERIOLES, which in turn branch into

smaller CAPILLARIES, where diffusion occurs

• capillaries combine to VENULES, which in turn group into VEINS to return blood

to the heart




• these vessels have a complex walls composed of up to three distinct layers:

the TUNICA EXTERNA, the TUNICA MEDIA and the TUNICA INTIMA

• the thickness of these layers varies between each type of vessel:

• Arteries close to heart have a thick tunica externa

• this layer is composed of collagen fibers that support and reinforce the vessel

to withstand high pressure during circulation

• capillaries lack a tunica externa and tunica media and have extremely thin walls

to promote the exchange of substances between blood and tissues




• these vessels have a complex walls composed of up to three distinct layers:

the TUNICA EXTERNA, the TUNICA MEDIA and the TUNICA INTIMA

• the thickness of these layers varies between each type of vessel:

• veins often have a thinner tunica externa than arteries

• generally, do not have to cope with high pressure flow




• vertebrate circulatory systems contain one or more pumps in series

• water-breathing fish have a single system in which blood flows from the heart

through to the gills and body tissues before returning to the heart

• because heart must pump blood through both the tissues and the gills in one

circuit, some fish have evolved a CAUDAL HEART to assist with blood flow back to

the heart

• other fish use normal movements to assist in blood return

• Hagfish and carpet

sharks use caudal

hearts




• in contrast tetrapods (amphibians, reptiles, birds and mammals) have two

circuits:

• PULMONARY CIRCUIT-the right side of the heart pushes blood through the

lungs

• SYSTEMIC CIRCUIT-left side of the heart pushes blood through the body

tissues




• although left and right sides of the heart are joined together in a single organ, in

birds and mammals these sides are functionally separated

• functionally, more like a single circuit with two pumps

• having separated pulmonary and systemic circuits has an important advantage:

allows pressure in each circuit to be different

• in lungs, capillaries must be thin to allow for gas exchange and cannot withstand

high pressure

• in contrast high pressure is needed in the systemic circuit to force blood

throughout the body




• trade-off to completely separated circuit is that the circulatory system becomes

relatively inflexible

• for example, if a mammal holds it’s breath, blood must still flow to the lungs

despite that the fact that blood is not becoming oxygenated when it arrives

• because breathe continuously, has been selection pressure to divert blood flow

from pulmonary circuit

• however, there are some

important adaptations

that marine mammals

have acquired to facilitate

long periods of holding

their breathe, which we

will discuss in a future

lecture

Sperm whale



• unlike birds and mammals, amphibians and reptiles have incompletely divided

hearts

• because ventricles of the heart are interconnected, blood can be diverted from

pulmonary to systemic circuit or vice-versa.

• for example, can divert blood from the pulmonary circuit to the systemic circuit

during diving to avoid the inactive lung


LECTURE SUMMARY

• circulatory systems are classified as either OPENED or CLOSED, but not always

clear such as in decapod crustaceans

• closed circulatory systems evolved independently in the vertebrates,

cephalopod molluscs and annelid worms.

• vertebrate blood vessels are structurally diverse and their compositions varies

depending on the function of the vessels (e.g. arteries vs. capillaries)

• vertebrate circulatory systems contain one or more pumps in series

• fish have a single circuit, while reptiles, amphibians, birds and mammals have

two circuits: PULMONARY and SYSTEMIC

• unlike birds and mammals, amphibians and reptiles have incompletely divided

hearts

NEXT LECTURE

HEARTS

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BIOL 3151: Principles of Animal Physiologyevanslabcsueb.weebly.com/uploads/1/2/1/9/12193389/...• animal circulatory systems have threemain components required for bulk flow: 1. A