I. Animal Size/Shape and the EnvironmentII. Four tissue categoriesIV. Feedback Control and temperature regulationV. Metabolic Rate and Energy Use

VII. Summary

Lecture 12 Outline (Ch. 40)

2What things to animals do to maintain homeostasis?

3

Overview: Diverse Forms, Common Challenges

• Anatomy: study of biological form of an organism

• Physiology: study of biological functions of an organism

• Communication and integration

• Support and movement

• Regulation and maintenance

• Defense• Reproduction and

development

Cells must continually be bathed in aqueous medium to exchange gasses, nutrients, wastes – all by

diffusion which is only effective over short distances.

A. How long does it take a small molecule to travel 1 um?

B. How long to travel 1 mm?

5

0.5 cmNutrients

Digestivesystem

Lining of small intestine

MouthFood

External environment

Animalbody

CO2 O2

Circulatorysystem

Heart

Respiratorysystem

Cells

Interstitialfluid

Excretorysystem

Anus

Unabsorbedmatter (feces)

Metabolic waste products(nitrogenous waste)

Kidney tubules

10 µm

50 µ

m

Lung tissue

• More complex organisms have highly folded internal surfacesOverview: Diverse Forms, Common Challenges

Cells bathed in interstitial fluid

How does the surface area to volume ratio change as a cell increases in size? (let’s say

cells are roughly spherical)

diameter: SA cell: Volume cell:d = 1 µmd = 10 µmd = 100 µm

SA = 4r2 V = 4/3r3

7

Exchange

0.15 mm

(a) Single cell

1.5 mm

(b) Two layers of cells

Exchange

Exchange

Mouth

Gastrovascularcavity

Rate of exchange related to SAAmount of exchange related to V

Overview: Diverse Forms, Common Challenges

8

• Tissues are classified into four main categories:

Tissue Structure and Function

Humans: 210 different cell types – can you name them?! ;)

9

Epithelial Tissue

Cuboidalepithelium

Simplecolumnarepithelium

Pseudostratifiedciliatedcolumnarepithelium

Stratifiedsquamousepithelium

Simplesquamousepithelium

Note differences in cell shape and type of layering

Tissue Structure and Function

10

Apical surface

Basal surfaceBasal lamina

40 µm

Tissue Structure and Function

Epithelial cells are attached to a basal lamina at their base.

11

Connective Tissue

Connective tissue binds / supports other tissues• sparsely packed cells scattered

in extracellular matrix• matrix - fibers in a liquid,

jellylike, or solid foundation

There are six main types of connective tissue.

12

Connective Tissue

Collagenous fiberLooseconnectivetissue

Elastic fiber120

µm

Cartilage

Chondrocytes

100

µm

Chondroitinsulfate

Adiposetissue

Fat droplets

150

µm

White blood cells

55 µ

m

Plasma Red bloodcells

Blood

Nuclei

Fibrousconnectivetissue

30 µ

m

Osteon

Bone

Central canal

700

µmTissue Structure and Function

13

Muscle Tissue• Muscle tissue: long cells (muscle fibers) that contract in

response to nerve signals

Skeletal muscle - striated, voluntary movementSmooth muscle – not striated, involuntary body activitiesCardiac muscle – striated, contraction of the heart

14

Muscle Tissue

50 µmSkeletalmuscle

Multiplenuclei

Muscle fiber

Sarcomere

100 µm

Smoothmuscle

Cardiac muscle

Nucleus

Musclefibers

25 µm

Nucleus Intercalateddisk

Tissue Structure and Function

Glial cells

Nervous Tissue

15 µm

DendritesCell body

Axon

Neuron

Axons

Blood vessel

40 µm

15

Tissue Structure and Function

• Nervous tissue senses stimuli, transmits signals Nervous tissue contains:

Neurons transmit nerve

impulsesGlial cells nourish, insulate,

and replenish neurons

16

Self-Check

Tissue Category Tissues/Cells Included; Functions

Epithelial

Connective

Muscle

Nervous

17

Response:Heater turnedoff

Stimulus:Control center(thermostat)reads too hot

Roomtemperaturedecreases

Setpoint:20ºC

Roomtemperature

increases

Stimulus:Control center(thermostat)

reads too cold

Response:Heater turnedon

Feedback control loops maintain the internal environment in many animals

Examples of negative and positive feedback?

Which maintains homeostasis?

• Animals manage their internal environment by regulating or conforming to the external environment

18

• regulator: uses internal mechanisms to maintain during external change.• Ex: River otter

• conformer: allows internal variables to change with environment.• Ex: Largemouth bass

Temperature Regulation

19

• Five general adaptations help animals thermoregulate:

– Insulation– Circulatory adaptations– Cooling by evaporative

heat loss– Behavioral responses– Adjusting metabolic heat

production

Balancing Heat Loss and Gain

Dragonfly “obelisk” posture

20

Temperature Regulation

• Thermoregulation: process by which animals maintain an internal temperature

(a) A walrus, an endotherm

(b) A lizard, an ectotherm

• Endothermic animals generate heat by metabolism (birds and mammals)

• Ectothermic animals gain heat from external sources (invertebrates, fishes, amphibians, and non-avian reptiles)

We’ve discussed several mechanisms related to homeostasis and in particular temperature

regulation.

Are all endotherms regulators? Are all ectotherms conformers?

Can you think of any examples that do not follow this trend?

22

• Metabolic rate is the amount of energy an animal uses in a unit of time

Energy Use

Measured by amount of oxygen consumed or carbon dioxide produced

• Basal metabolic rate (BMR) is the metabolic rate of an endotherm at rest at a “comfortable” temperature

23

Shrew

Harvest mouseMouse

Ground squirrelRat

Cat Dog

SheepHuman

Horse

Elephant

Body mass (kg) (log scale)

BM

R (L

O2/h

r) (l

og s

cale

)

(a) Relationship of BMR to body size

10–3 10–210–2

10–1

10–1

1

1

10 102 103

10

102

103

Energy Use

24

10310210110–110–210–30

1

2

3

4

5

6

7

8

Body mass (kg) (log scale)

(b) Relationship of BMR per kilogram of body mass to body size

BM

R (L

O2/

hr) (

per k

g)Shrew

Harvest mouse

MouseRat

Ground squirrelCat

Sheep

DogHuman

HorseElephant

Energy Use

Human average daily metabolic rate is only 1.5X BMR!

Which animal would have the highest BMR per unit body weight?

1. human2. dog3. mouse4. whale5. turtle

26

Energy Budgeting

• Hibernation is long-term torpor that is an adaptation to winter cold and food scarcity

• Torpor = physiological state with low activity and metabolism decreased – allows animals to save energy while avoiding difficult and dangerous conditions

In discussing homeostasis, regulation, and hibernation, consider the following:

Why would an animal use hibernation? What might be gained by this behavior?

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Additional metabolism that would benecessary to stay active in winterActual

metabolism

Arousals

Bodytemperature

Outsidetemperature Burrow

temperature

Met

abol

ic ra

te(k

cal p

er d

ay)

Tem

pera

ture

(°C

)

June August October December February April–15

–10–5

05

15

10

25

20

3530

0

100

200

Energy Use