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Chapter 40
Lecture 12
Physiology and Homeostasis
Dr. Chris Faulkes
Heat Limits Performance
Physiology & Homeostasis
Aims:
•  To introduce the organisation of animal bodies
•  To introduce homeostasis
•  To be able to define cells, tissues, organs and
organ systems.
•  To be able to link the structure of the four
tissues with function
Physiology & Homeostasis
Aims:
•  To introduce the organisation of animal bodies
•  To introduce homeostasis
•  To be able to define cells, tissues, organs and organ systems.
•  To be able to link the structure of the four tissues with function
These lecture aims form part of the knowledge
required for learning outcome 1:
Describe the structure, diversity and reproductions
of selected plants and animal groups (LOC1).
Physiology & Homeostasis
•  40.1 Why Must Animals Regulate Their Internal
Environments?
Essential reading
•  page 854-860
40.1 Why Must Animals Regulate Their Internal Environment?
A stable internal environment of
extracellular fluid makes complex
multicellular animals possible.
Cells are specialized for maintaining
parts of the internal environment.
40.1 Why Must Animals Regulate Their Internal Environment?
External functions: transport of nutrients
and waste and maintenance of ion
concentrations.
Internal functions: circulation, energy
storage, movement, and information
processing.
40.1 Why Must Animals Regulate Their Internal Environment?
Homeostasis is the maintenance of
stable conditions in an internal
environment.
Physiological systems are controlled
by the nervous and endocrine
systems.
Regulation of the internal environment
requires information.
Figure 40.1 Maintaining Internal Stability
40.1 Why Must Animals Regulate Their Internal Environment?
Types of information necessary for
physiological systems:
• Set point: a reference point
• Feedback information: what is
happening in the system
• Error signal: any difference between
the set point and feedback information
40.1 Why Must Animals Regulate Their Internal Environment?
Effectors of systems effect changes in
the internal environment.
Effectors are controlled systems
because they are controlled by
regulatory systems.
40.1 Why Must Animals Regulate Their Internal Environment?
Regulatory systems:
• Obtain, integrate, and process
information
• Issue commands to controlled
systems
• Contain sensors to provide feedback
information that is compared to the
set point
Figure 40.2 Control, Regulation, and Feedback
40.1 Why Must Animals Regulate Their Internal Environment?
Sensory information in regulatory
systems includes:
• Negative feedback
• Positive feedback
• Feedforward information
40.1 Why Must Animals Regulate Their Internal Environment?
Negative feedback:
•  Causes effectors to reverse the influence that
creates an error signal
•  Returns a variable to its set point
Positive feedback:
•  Amplifies a response
•  Increases deviation from a set point
Feedforward information anticipates internal
changes and changes the set point.
40.1 Why Must Animals Regulate Their Internal Environment?
Physiological systems are made up of
organs that serve specific functions.
Organs are made up of tissues, which
are then made up of cells.
40.1 Why Must Animals Regulate Their Internal Environment?
Four types of tissue:
• Epithelial
• Connective
• Muscle
• Nervous
40.1 Why Must Animals Regulate Their Internal Environment?
Epithelial tissues are sheets of tightly
connected epithelial cells.
The tissues form skin and line hollow
organs.
40.1 Why Must Animals Regulate Their Internal Environment?
Some epithelial cells can:
• Secrete substances, like hormones
• Move substances with cilia
• Act as chemical receptors
• Create boundaries
• Control filtration and transport
Figure 40.3 Epithelial Tissue
40.1 Why Must Animals Regulate Their Internal Environment?
Muscle tissues consist of elongated
cells that generate force and cause
movement.
Three types of muscle tissues:
• Skeletal
• Cardiac
• Smooth
40.1 Why Must Animals Regulate Their Internal Environment?
• Skeletal: responsible for locomotion
and other body movements (e.g.,
breathing, shivering).
• Cardiac: makes up the heart and is
responsible for the heartbeat and
blood flow.
• Smooth: involved in movement and
generation of forces in internal
organs (e.g., gut, blood vessels).
Figure 40.4 Filaments in Skeletal Muscle Cells
Muscle Cells
Cardiac muscle
Smooth muscle
40.1 Why Must Animals Regulate Their Internal Environment?
Connective tissues are dispersed cells in
an extracellular matrix that they secrete.
The matrix contains protein fibres:
•  Collagen: strong and resistant to stretch,
supports skin and connections between
muscles and bones
•  Elastin: can be stretched and then recoils;
found in tissues that stretch (e.g., lungs,
arteries)
40.1 Why Must Animals Regulate Their Internal Environments?
Connective tissues:
• Cartilage provides structural support
and is flexible: has chondrocytes;
cells that secrete the extracellular
matrix.
• Bone: provides support and is
hardened by calcium phosphate
deposition in the matrix.
Cartilage
Bone
40.1 Why Must Animals Regulate Their Internal Environments?
More connective tissues:
•  Adipose tissue: includes adipose cells that form and
store lipids.
•  Blood: consists of cells in a very liquid extracellular
matrix, the blood plasma.
Adipose tissue (fat)
40.1 Why Must Animals Regulate Their Internal Environments?
Nervous tissues contain two basic
cell types: neurons and glia.
Neurons encode information as
electrical impulses that travel over
axons to their targets.
Chemical signals from the neuron
stimulate a response in the target
cell, via receptors.
Glia provide support for neurons.
Figure 40.6 Nervous Tissue Includes Neurons and Glia
40.1 Why Must Animals Regulate Their Internal Environments?
Organs consist of multiple tissues.
An organ system is a group of organs
that function together.
40.1 Why Must Animals Regulate Their Internal Environments?
Example: The stomach wall is
arranged in layers:
• Epithelial cells
• Connective tissue
• Smooth muscle
• Neurons
• Connective tissue
Figure 40.7 Tissues Form Organs
Physiology & Homeostasis
Check out
•  40.1 RECAP, page 860
•  40.1 CHAPTER SUMMARY, page 871
Self Quiz
page 871: Chapter 40, question 1
For Discussion
•  page 872: Chapter 40, questions 1-2
Physiology & Homeostasis
Key terms:
adipose tissue, axons, blood, blood plasma, cardiac,
cartilage, cell, chemoreceptor, cilium (pl. cilia),
collagen, connective, effector, endocrine, epithelial,
feedback, Glial cell, homeostasis, loose connective
tissue, matrix, metabolism, muscle, nerve, nervous,
organ, organ system, reticular connective tissue,
sensor, skeletal, smooth, tissue