BIOL 191A Unit 3

All animals share similarities in how they…

1. exchange materials with their surroundings
2. obtain energy from organic nutrients
3. synthesize complex molecules
4. detect and respond to signals in their environment
5. reproduce themselces

4 types of animal tissues

1. muscle tissue
2. nervous tissue
3. epithelial tissue
4. connective tissue

muscle tissue

contain cells that are specialized to contract(shorten) which generates mechanical forces that may

* produce body movements(skeletal)
* decrease the diameter of a tube(smooth)
* exert pressure on a fluid-filled cavity(cardiac)

nervous tissue

complex networks of neurons from one part of the body to another

* electrical signal produced in one neuron may
* stimulate or inhibit another neuron
* stimulate muscle cells to contract
* stimulate glandular cells to secrete their products(ex. sweat glands, digestive glands)

neurons

cells that communicate by initiating and conducting electrical signals(action potentials) from one part of the body to another

epithelial tissues

sheets of densely packed cells that cover body surfaces, enclose organs, or line the walls of body cavities

* cells specialized for protection and transport
* asymmetrical(basal and apical surfaces)
* squamous, cuboidal, columnar
* tissues may be simple, stratified, pseudostratified, or transitional

connective tissues

diverse group of tissues that connect, surround, anchor, and support the structures of an animal’s body

* adipose tissue
* bone cartilage
* loose connective tissue
* dense connective tissue
* blood

high surface area/volume(SA/V) ratio

ideal for functions related to transport, absorption, or detection of environmental stimuli(ex. frog skin, human intestine)

homeostasis

process of maintaining relatively stable internal environment, despite changes in external surroundings

* fluctuations in air temp., water temp., nutrient availability, water availability, pH, and O2 availability occur in variable environments
* dynamic process

conformers

features of internal environment match external environment; restricted to stable environments; inexpensive

* ex. body fluids in a marine crab having same solute concentration, same w/ fish water temp.

regulators

features of internal environment differ from external environment; expensive strategy

* ex. human body temp. regulation

variables maintained within a normal range

1. concentrations of nutrients, wastes, and ions in the blood
2. concentration of O2 and CO2 in body fluids
3. pH of body fluids
4. blood pressure and blood volume

homeostatic control systems

1. decrease in body temp. disrupts homeostasis
2. **sensor** is typically group of neurons, such as temp. sensitive neurons in the skin
3. **integrator** located in brain and compares input from sensor w/ a **set point**
4. **effector** produces a response that compensates for change caused by homeostatic challenge

negative feedback loop

change in the variable being regulated brings about a response that moves the variable in the __opposite__ direction; maintains variable w/in normal range

positive feedback loop

accelerates a process; change in variable leads to events that __amplify__ that change; ex. blood clotting and uterine contractions

feedforward regulation

present in animals w/ well-developed nervous systems; animal’s body prepares for possible challenge to homeostasis

* ex. elevated heart rate prior to activity increase

mammalian narrow range of body temperatures

resting body temperature: 35-38 degrees C

humans: body temp of 41 degrees C results in organ damage and temp of 42-43 degrees C is fatal

3 ways that temperature affects animals’ bodies

1. chemical reactions


1. inc. in body temp. speeds up reactions
2. low temp. makes it hard to carry out homeostasis
2. protein functions


1. high temps. can cause protein denaturing
3. membrane structure - think of it like ice


1. low temps. membranes too rigid(freezing)
2. high temps. membranes too fluid(melting)


1. both can disrupt membrane function

metabolic rate

amount of energy an organism uses in a given period of time to power its activities

* greater this is, more heat an animal generates
* calories used to quantify energy of metabolism

basal metabolic rate(BMR)

most common measure used to compare metabolic rates of different species

* metabolic cost of living in a resting animal under controlled conditions

endotherms

animals that generate their own internal heat through their metabolism

* require larger amounts of energy → food consumption
* risk of overheating during activity
* risk of loss of body fluids(esp. from evaporation due to cooling, sweating)

ectotherms

animals that rely on heat from the external environment to warm themselves

homeotherms

can maintain their body temp. w/in a narrow range

heterotherms

have body temps. that undergo considerable variations

heat exchange: radiation

emission of electromagnetic waves by the surface of objects; rate of emission determined by temp. of surface

* ex. heat from the sun radiates into the body, body heat radiates into air

heat exchange: evaporation

conversion of water from a liquid to a gaseous state; animals lose heat through evaporation of water from body surfaces

* heat is released by this due to sweating, panting

heat exchange: conduction

heat exchange through direct contact w/ other objects; greater temp. difference, greater rate of heat transfer

* ex. heat from body is transferred into cooler water

heat exchange: convection

transfer of heat by the movement of air or fluid next to the body

* ex. wind cools the body

How can endotherms regulate how much heat is gained or lost between the environment and their bodies?

1. changes in skin blood flow
2. countercurrent exchange
3. evaporative heat loss
4. behavioral adaptations

endotherms: countercurrent exchange

heat is transferred between fluids flowing in opposite directions

* regulates heat loss by returning heat to body’s core and keeping core warmer than extremeties
* ex. warm blood travels down arteries in bird leg, heat moves by **conduction** to adjacent veins carrying cooler blood in the opposite directione

endotherms: evaporative heat loss

regulated by changes in perspiration(for organisms w/ sweat glands) by panting

endotherms: behavioral adaptations

changing exposed body surface area(stretched out when hot; huddle when cold) and changing surroundings(seek shade, immerse in water when hot; stay in burrow when cold) THE BURROWING OWLS

types of changes in muscle activity for control of heat production in endotherms(staying warm when cold)

1. **shivering thermogenesis** - skeletal muscles contract rapidly without any locomotion; chem. reaction energy released as heat
2. nonshivering thermogenesis - heat production occurring in **brown adipose tissue**


1. uncoupling proteins modify mitochondria functions so energy of H+ gradient dissipated as heat(rather than energy for ATP synthesis)

intracellular fluid

water contained inside cells

* fluid inside little yellow ball cells in picture; little balls outside blood vessel

extracellular fluid

primarily present as:


1. blood plasma - fluid flowing inside blood vessel around erythrocytes
2. interstitial fluid - fluid surrounding cells; yellow substance outside blood vessel

(these are separated by the walls of blood vessels)

osmosis

allows water to move between fluid compartments in response to pressure differences

maintenance of normal body water levels is important for several reasons

1. water is solvent which aids dissolved solutes to participate in chemical reactions
2. water is transport vehicle the brings O2 and nutrients to cells and removes wastes generated by metabolism


1. dehydration compromises circulatory system and body temp. regulation

2 reasons ion balance is critical for cellular activites

1. muscle contraction
2. communication in nervous system

(can be compromised by dehydration; measured by **osmolarity)**

osmolarity

measure of solute concentration; value around 300 mOsm/L typical for animal body fluids

obligatory processes which have potential to disturb ion and water balance

1. eliminate nitrogenous wastes
2. obtain O2 and eliminate CO2
3. consume and metabolize food
4. regulate body temp.

(generally req. additional energy expenditure)

nitrogenous wastes

when proteins and nucleic acids are broken down in metabolized, these are generated; toxic in high concentrations and must be eliminated

respiration

in animals with lungs; associated w/ significant water loss

* why you might wake up dehydrated

gills

water and ions can move across…

freshwater fish

* doesn’t drink water
* H2O enters gill capillaries by osmosis
* active uptake of Na+ and Cl- across gill epithelia into capilaries
* urine very dilute, copious containing very few ions
* osmolarity of water: 0-50 mOsm/L

takes in as much solutes as possible and excretes as much water as possible

saltwater fish

* drinks seawater
* H2O leaves gill capillaries and enters seawater by osmosis
* active excretion of Na+ and Cl- across gill epithelia
* small amount of concentrated urine containing large amounts of ions
* osmolarity of seawater: 1,000 mOsm/L

takes in as much water as possible and tries to excrete as much solutes as possible

foods

contribute to ion and water balance; some water also created during metabolism

sweating and panting

in endotherms; used to cool the body, water lost from both, ion loss for one(think salty)

circulatory systems

transport necessary materials to all the cells to an animal’s body and transports wastes away from cells

open circulatory system

**hemolymph** fluid is pumped by one or more contractile hearts into the body cavity(**hemocoel**) of an animal

* metabolically inexpensive
* limits:
* inability to selectively deliver hemolymph to different tissues
* arthropods and some mollusks have this

hemolymph

in open circulatory systems; fluid in blood vessels and the interstitial fluid that surrounds cells are __mixed__; this is the mixture

* nutrients and wastes are exchanged between this and cells(BUT O2 and CO2 are __not__ transported in this)
* returned through vessels or ostia to the heart

closed circulatory system

**blood** and **interstitial fluid** __separate__ and distinct; blood flows through **vessels**

* found in all earthworms, cephalopods, and all vertebrates
* distribution of blood flow can be adjusted to meet metabolic demands
* larger animals

blood

fluid connective tissues that contains a mixture of cells and solutes; transports nutrients, wastes, O2, and CO2; pressurized by one or more contractile hearts

* transport medium of animals with closed circulatory systems; moves all necessary materials to cells and takes away wastes
* components include:
* plasma
* leukocytes
* erythrocytes
* platelets

plasma

composed of water, dissolved nutrients, ions, wastes, proteins, and gases; typically half total volume of blood

leukocytes(white blood cells)

protect and defend the body

erythrocytes(red blood cells)

transport O2

* contain large amounts of **hemoglobin**, reversibly binds O2(and CO2)
* in most vertebrates, mature retain nuclei, but in mammals, nuclei lost during maturation

hemoglobin

large amounts in erythrocytes, reversibly binds O2(and CO2)

platelets

in vertebrate blood; cells/cell fragments that function in blood clot formation

* known as **thrombocytes** in other vertebrates


1. injury ruptures blood vessel
2. platelets stick to each other and to collagen fibers, forming a plug; blood loss reduced
3. fibrin forms meshwork which traps erythrocytes and platelets, forming clot that seals wounds

arteries

carry blood away from a heart

veins

carry blood towards a heart

capillaries

sites of blood exchange

vertebrate circulatory systems(closed)

1. **single circulation** - in fishes
2. **double circulation** - in crocodiles, birds and mammals

single circulation

in fishes; heart has single filling chamber(atrium) and single exit chamber(ventricle)

double circulation

in crocodiles, birds, and mammals; heart has 4 chambers and 2 circuits of blood flow(**pulmonary** and **systemic circulation**)

septum

muscular wall that separates the two sides of the heart

blood flow through the heart

\*begin with deoxygenated blood


1. vena cava
2. right atrium
3. tricuspid valve(right atrioventricular valve)
4. right ventricle
5. pulmonary semilunar valve
6. pulmonary trunk → arteries
7. lungs → oxygenated blood
8. pulmonary veins
9. left atrium
10. bicuspid valve(left atrioventricular valve)
11. left ventricle
12. aortic semilunar valve
13. aorta → rest of body

neurogenic heart(arthropods)

heart that ONLY beats when it receives impulses from the nervous system

myogenic heart(in vertebrates)

signaling mechanism that initiates contraction resides WITHIN the cardiac muscle itself

* nervous system can regulate rate and forcefulness of contraction

electrical excitation

leads to contraction in the heart beginning with the atria → ventricles

pacemaker

group of specialized cells that are located at the **sinoatrial(SA) node**

sinoatrial(SA) node

generates an electrical impulse beginning electrical excitation which spreads quickly across the atrial muscle to the **atrioventricular(AV) node**

atrioventricular(AV) node

receives electrical impulse form SA node during electrical excitation where it then conducts electrical signals from the atria to the ventricles

cardiac cycle

contraction and relaxation events that produce a single heartbeat; heart chambers progress through 2 phases during this

cardiac cycle phase: diastole

muscle is relaxed; chamber is filling

cardiac cycle phase: systole

muscle is contracting; chamber is emptying

process of the cardiac cycle

1. atrial systole
2. atrial systole ends, atrial diastole begins
3. ventricular systole - 1st phase
4. ventricular systole - 2nd phase
5. ventricular diastole - early
6. ventricular diastole - late

heart valves

open and close in response to pressure gradients; prevent backflow; makes sounds when they close(heartbeat)

blood pressure(P)

force exerted by the blood on the walls of the blood vessels; changes throughout the cardiac cycle, why blood pressure is measured w/ 2 numbers; drives blood flow

* highest during ventricular systole
* lowest during ventricular diastole
* typical healthy blood pressure in a human is around 120/80 mmHg(systolic/diastolic)

electrocardiogram(ECG or EKG)

overall recording of electrical impulses generated during the cardiac cycle

* reveals several waves of electrical excitation
* P wave
* QRS complex
* T wave

P wave

corresponds to atrial excitation

QRS complex

corresponds to ventricular excitation

T wave

corresponds to the reset of the ventricles back to their resting state

* tea is calm

blood flow through blood vessels in a closed circulatory system

1. heart
2. larger arteries
3. small arteries
4. arterioles
5. capillaries
6. venules
7. small veins
8. large veins
9. heart

arteries

thick walled vessels that conduct blood __away__ from the heart

* contain many layers of smooth muscle and a slick inner lining called an **endothelieum**
* large ones often contain elastin fibers as well

arterioles

smaller, branched arteries; composed of one or two layers of smooth muscle and connective tissue surrounding a layer of endothelium

* can **dilate** or **constrict** to control blood distribution to tissues

capillaries

sites of exchange

* composed of single layer of endothelial cells, supported by a layer of extracellular matrix
* solutes readily diffuse between the blood in a capillary and the surrounding tissue

capillary blood flow

pressure forces some fluid out of the blood at the beginning of the capillary; most fluid returned to blood at the venule-end of a capillary(lymphatic system collects excess interstitial fluid)

venules

small thin-walled vessels that carry blood away from the capillaries; empty into **veins** that return blood to the heart

veins

return blood to the heart

* walls of veins are thinner, less muscular, and more easily distorted than arteries; blood pressure is low

factors that assist blood flow through the veins

1. communication from the nervous system
2. skeletal muscle activity in limbs
3. valves

blood flow(F)

the movement of blood; blood pressure drives this

resistance(R)

impedes or slows blood flow; blood vessels are a source of resistance because because of the friction that occurs between blood and vessel walls

R = 1/r^4 so if the lumen of an arteriole increased by a factor of 2, then the resistance would DECREASE by a factor of 16(2^4)

blood flow(F) equation

Flow(F) = change in pressure(P)/resistance(R)

or change in P = F X R

* blood flow is directly proportional to difference in pressure(between. the beginning and end of the vessel/circuit)
* inversely proportional to the resistance

radius of arterioles

can be changed to regulate resistance and the activity of the heart can be changed to regulate flow

vasodilation

increase in radius

vasoconstriction

decrease in radius

cardiac output

amount of blood the heart pumps per unit of time and is typically expressed in L/min

* determined by 2 parameters: heart rate(beats/min) and stroke volume(mL/beat)
* CO = SV x HR

Poiseuille’s law

expresses the relationship between flow, pressure, and resistance can be adapted to the whole body:

* BP = CO x TPR
* BP - arterial blood pressure
* CO - cardiac output(flow)
* TRP - total peripheral resistance

arterial blood pressure

function of how hard the heart is working and how constricted or dilated the various arterioles are

air composition

* 78% nitrogen
* 21% oxygen
* 1% carbon dioxide
* other gases

partial pressure

of a gas provides the driving air force for its diffusion; all gases diffuse from regions of higher pressure → lower pressure

* individual pressure exerted by each gas, which is exactly proportional to its amount in the mixture