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ANIMAL
PHYSIOLOGY
BIOL 3151:
Principles of Animal
Physiology
Dr. Tyler Evans
Email: [email protected]
Phone: 510-885-3475
Office Hours: F 8:30-11:30 or appointment
Website: http://evanslabcsueb.weebly.com/
AN EXCELLENT STUDENT QUESTION FROM
CELL MOVEMENT & MUSCLES LECTURE
1. What is an example of tetanic muscle contraction?
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does not occur under normal physiological conditions
instead caused by toxins or drugs
common cause is neurotoxin released by bacteria Clostridium tetani
also induced by strychnine (rat poison)
LAST LECTURE
MUSCLE DIVERSITY-TYPES OF MUSCLE
• smooth muscle also lacks TROPONIN, they key protein involved in regulating the
contraction of striated muscle
• use a different protein called CALDESMON, which binds to actin thin filaments
and blocks myosin binding sites when not stimulated
• when Ca+2 is released in smooth muscle cells it binds to a protein called
CALMODULIN
• calmodulin then removes caldesmon from actin, exposing the myosin binding site
• then events in the sliding filament model occur
LAST LECTURE
MUSCLE DIVERSITY-TYPES OF MUSCLE
SOUND PRODUCING ORGANS
• the frequency that these SONIC MUSCLES contract is impressive
considering potential time consuming cellular events that could
delay contraction, such as the formation of myosin-actin cross
bridges and cycling of Ca+2
• 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?
LAST LECTURE
MUSCLE DIVERSITY-TYPES OF MUSCLE
HEATER ORGAN IN BILLFISH
• billfish constantly cycle Ca+2 between
the sarcoplasmic reticulum and the
interior of the cell
• this activity produces metabolic heat,
but because the heater organ contains
few myofibrils and the Ca+2 is cycled so
quickly, no actual contraction occurs
• to facilitate this process heater organs
have high numbers of sarcoplasmic
reticula and mitochondria, but very
few muscle cells
TODAY’S LECTURE
CARDIOVASCULAR PHYSIOLOGY
Chapter 8
pg 348-409
Circulatory system of a crab
TODAY’S LECTURE
CHARACTERISTICS 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 PHYSIOLOGY
CHARACTERISTICS 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
• Recall concept of “UNITY IN DIVERSITY”
CARDIOVASCULAR PHYSIOLOGY
CHARACTERISTICS OF CIRCULATORY SYSTEMS
• 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
• 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
Circulatory system of a crab
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY 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
textbook Fig 8.3 pg 353
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY 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
• cnidarians propel water
(that carries oxygen and
food with it) through their
gastrovascular cavity using
muscular contractions of
the body wall.
textbook Fig 8.3 pg 353
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY 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
• Flatworms
(Platyhelminthes) also
have a gastrovascular
cavity, which is often lined
with FLAME CELLS whose
CILIA propel water to all
parts of the body
textbook Fig 8.3 pg 353
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
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
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
2. Annelids
• the majority of annelids have closed circulatory systems and possess a network 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 fluid down the ventral blood vessel
• the dorsal blood vessel itself is contractile and moves fluid from the ventral blood
vessel back to the five hearts
textbook Fig 8.4 pg 354
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
2. Annelids
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polychaetes are annelids that possess open circulatory systems
circulate body fluids using cilia or muscular contractions of the body wall
vessels drain into sinuses
substances diffuse from sinuses into cells
textbook Fig 8.34 pg 354
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
3. Molluscs
• all have well defined hearts or contractile organs and most have blood vessels
• almost all molluscs have open circulatory systems
• e.g. CLAMS-have open circulatory systems where fluid drains into sinuses before
diffusing into cells
textbook Fig 8.5 pg 354
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
3. Molluscs
• some cephalopods (squid, octopus, cuttlefish) have evolved completely closed
circulatory systems
textbook Fig 8.5 pg 354
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 reoxygenated
• re-oxygenated blood then
flows back to the systemic
heart
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
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
• vessel contains many OSTIA (holes) that allow
fluid to re-enter the main vessel
textbook Fig 8.6 pg 355
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
4. Arthropods
• almost all have one or more hearts and at least some blood vessels, but none can
be considered completely closed
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 reoxygenated prior to returning to the heart
• blood enters the heart though
OSTIA that can be opened or
closed
textbook Fig 8.6 pg 355
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
4. Arthropods
• almost all have one or more hearts and at least some blood vessels, but none can
be considered completely closed
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
textbook Fig 8.7 pg 355
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
4. 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
textbook Fig 8.8 pg 356
CARDIOVASCULAR PHYSIOLOGY
DIVERSITY IN CIRCULATORY SYSTEMS
CLOSED CIRCULATORY SYSTEMS EVOLVED INDEPENDENTLY MULTIPLE
TIMES
• evolved independently in the vertebrates, cephalopod molluscs and annelid
worms
• 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
CARDIOVASCULAR PHYSIOLOGY
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
textbook Fig 8.9 pg 357
CARDIOVASCULAR PHYSIOLOGY
VERTEBRATE CIRCULATORY SYSTEMS
• 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
textbook Fig 8.10 pg 358
CARDIOVASCULAR PHYSIOLOGY
VERTEBRATE CIRCULATORY SYSTEMS
• 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 same high pressure flow
textbook Fig 8.10 pg 358
CARDIOVASCULAR PHYSIOLOGY
VERTEBRATE CIRCULATORY SYSTEMS
• vertebrate circulatory systems contain one or more pumps in series
• water-breathing fish have a single circuit 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
textbook Fig 8.12 pg 360
• Hagfish and carpet
sharks use caudal
hearts
CARDIOVASCULAR PHYSIOLOGY
VERTEBRATE CIRCULATORY SYSTEMS
• 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
textbook Fig 8.12 pg 360
CARDIOVASCULAR PHYSIOLOGY
VERTEBRATE CIRCULATORY SYSTEMS
• 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
textbook Fig 8.12 pg 360
CARDIOVASCULAR PHYSIOLOGY
VERTEBRATE CIRCULATORY SYSTEMS
• 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
• 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
CARDIOVASCULAR PHYSIOLOGY
VERTEBRATE CIRCULATORY SYSTEMS
• 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
textbook Fig 8.13 pg 362
LECTURE SUMMARY
• circulatory systems are necessary because diffusion is extremely slow over long
distance and need a way to distribute substances to the body
• circulatory systems are classified as either OPENED or CLOSED, but not always
clear distinction as in decapod crustaceans
• 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
• vertebrate blood vessels are structurally diverse and their structure varies
depending on the function of the vessels (e.g. arteries vs. capillaries)
• fish have a single circuit, while reptiles, amphibians, birds and mammals have
two circuits: PULMONARY and SYSTEMIC
• having separated pulmonary and systemic circuits has an important
advantage: allows pressure in each circuit to be different
• trade-off to completely separated circuit is that the circulatory system
becomes relatively inflexible
• unlike birds and mammals, amphibians and reptiles have incompletely divided
hearts
NEXT LECTURE
HEARTS