BPK 205
Introduction to Human Physiology
Lecture 1
Overview of the Course;
Homeostasis & Physiological Organization
Dr. N. Wicks
Fall 2024
1
Lecture Objectives
• Define the term “physiology”
• Define and give examples of homeostasis
– Negative and positive feedback loops affect
homeostasis
– Feedforward control and homeostasis
• Describe the biological hierarchy of organization in the
context of compartments
– Functional compartments: Cells, tissues, organs
– Fluid compartments: Intracellular vs Extracellular
• Describe the key properties of cellular membranes
2
Readings
• Chapter 1: Introduction to Physiology
• Chapter 2: Molecular interactions (review)
• Chapter 3: Compartmentalization: Cells and
Tissues
3
What is Physiology?
“Physiology is the study of living things and how
they function. Physiology helps us understand
how the body works, from the smallest part
(cells) all the way to the whole body. It helps
us understand how different parts of the body
work together.”
American Physiological Society
http://www.the-aps.org/
4
Where does physiology fit into the life
sciences?
PHYSIOLOGY
ECOLOGY
CELL
BIOLOGY
MOLECULAR
CHEMISTRY
Atoms
BIOLOGY
Molecules
Cells
Tissues
Organs
Organ
systems
Organisms
Populations of
one species
Ecosystem of
different species
Biosphere
Fig 1.1
5
The Goal of Physiological Systems:
HOMEOSTASIS constance
:
The maintenance of a relatively stable internal environment
•
We have a “set point” that dictates the level of
certain variables.
•
The goal is to maintain these variables within a
tight range based on the set point
•
Body must maintain mass balance
(deviation from – i.e. if the amount of a substance in the body
set point)
is to remain constant, then:
•
Fig. 1.4
input + production = output + consumption;
see Fig. 1.6
Examples:
– Temperature
– Blood pressure
– Blood glucose level
– pH
6
* Chemical dis-equ is essential
to
Homeostasis ≠ Equilibrium cellular
external
cellular
fluid
internal
biological processes
fluid
Fig. 1.7
Consider homeostasis as maintenance of a dynamic steady-state
dynamic eyu .
7
Maintaining Homeostasis:
Negative Feedback loops
I
shuttingoff
after rainone
Signal to effector to
initiate change
Signal to
integrating center
Integrating Center
elevatedtempe
Sensor
Stimulus
Effector
Output
Output level changes
and “feeds back” to sensor
8
Negative Feedback loop
* trial
e.g. Regulation of Body Temperature
ul different
Signal to
integrating center
Nerve signal AP
about
temperature
Signal to effector to
initiate change
Nerve Signal
outgoing AP
:
Sensor
Nerve endings
stimulus
Integrating Center
Hypothalamus
Stimulus
Stimulus:
Temperature
Effector
Skeletal Muscles
Output
Blood vessels
Output level changes
and “feeds back” to sensor
9
Negative vs. Positive Feedback Loops
• In a negative feedback system, the feedback
reduces the difference between the desired
setpoint and the actual value; i.e. it works to
reduce the initial stimulus and regain
homeostasis.
>
-
self-reinforcingloop
(milk let down as ey or
• In a positive feedback system, the feedback childbirth)
increases the difference between the normal
setpoint and the actual value; i.e. it enhances the
stimulus and moves the system away from
homeostasis
10
Positive Feedback Loops:
A deviation from homeostasis
e.g. Labour and childbirth
Stimulus
Baby Drops, presses on cervix
Sensor
e
Stretch Receptors in Cervix
Integrating Center
>
-
increaser we
Brain → Oxytocin release
Effector
Smooth muscles of the uterus
Response Increased contractions
11
Fig. 1.13
Feedforward Control
• Initiation of a response in anticipation of the
stimulus
– E.g. Sight, smell or thought of food is enough to
initiate salivation and digestion
– E.g. Increase in ventilation (breathing) as soon as
exercise begins
12
* first quiz question
* attempt to reproduce
Biological Hierarchy of Organization
> main
-
four
Compartmentalization allows for separation of complex processes
13
* review system functions
Organ Systems
A collection of parts that work together in a
predictable way to achieve a common function.
Fig.141.2
Compartments of the Body
Organs
Tissues
Cells
Compartments Are Separated by Membranes
Pericardial
membrane
Tissue membranes
Phospholipid bilayers
have many cells.
create cell membranes.
Cell
Heart
The pericardial sac is
a tissue that surrounds
the heart.
Loose
connective
tissue
Seen magnified, the pericardial
membrane is a layer of
flattened cells supported by
connective tissue.
Each cell of the
pericardial membrane
has a cell membrane
surrounding it.
The cell membrane
is a phospholipid
bilayer.
Fig 3.1
Lumen: The interior of hollow organs
Cytoplasm: The interior of cells
15
k + inside ,
Nall outside Labundance)
g
Body Fluid Compartments
i
m
bal
a
nce
-
can cause
ention detema
[
Fig. 5.1a
16
Body Fluid Distribution
3L
11 L
28 L
Plasma
Volumes for standard 70 kg male (60% water)
Water content varies with age and sex (Table 5.1)
Interstitial
fluid
Intracellular
fluid
ECF
1/3
Cell
membrane
ICF
2/3
ECF = Extracellular Fluid
ICF = Intracellular Fluid
See fig 5.1 17
The Cell: Review
Cell membrane = plasma membrane
The Cell
• Provides structural support
• Physical barrier between ICF/ECF
• Selectively permeable
• Regulates exchange
• Regulates communication
Cytosol = intracellular fluid
Cytoplasm = intracellular fluid +
organelles, inclusions, proteins
a & COL
:
green light
(an poss
fredy)
Fig 3.4
REVIEW: Ch 2 – Basic Chemistry & Protein interactions
Ch 3 – Cell membranes & Intracellular compartments of the cell, pp 65-72 (Fig. 3.4)
18
The Cell Membrane: Review
→Mostly phospholipid
bilayer
Fig 3.2
→Also contains:
hydrophil
▫ Proteins
Transmembrane Krosd
Peripheral (non-covalent
attachment)
Lipid-anchored (covalent
bond)
hydrophilic
>
-
&
hydrophilicefacing
a
into rolun
.
▫ Carbohydrates
▫ Glycoproteins & Glycolipids
▫ Cholesterol
▫ Affects membrane fluidity and permeability
19
Lecture Review Questions
• Chapter 1, Level 1 Questions 1-5, 7-8
• Chapter 1, Level 2 Questions 12-13
• Chapter 3, Level 1 Questions 1-3, 10-12
• Chapter 3 Level 2 Questions 16, 19, 21
*Review questions are recommended to reinforce key
concepts and most often do not represent exam-style
questions. Practice questions are given in tutorials and
provided prior to exams.
20
Lecture 1
Define
-
Summary & Mind Map
Physiology
The
study of living things & how they function
↳
the body works from
What is homeostasis ?
↳
Give
a
study allows us to understand how
micro-macro level & how
systems work with eachother
The
.
,
examples.
relatively table internal environment.
↳
Keeping certain systems to 'set point
Homeostan's is the
maintenance of a
a
Examples: Temperature of body blood pressure
Homeostasis #
Egm
Elf diff
↳
ECF
=
,
instead it is maintenance
Extra cellular
ICF = Entra
matrix :
cellular
matrix
:
gluore
,
,
blood
plt
dynamiccontent changa
of a
High Nat Med CI-
,
Low
K+
High K +, Low Nat& C-
Negative feedback loops Reduces difference between
:
homeostan's
Diagram
blood
,
,
set
point current value
...
reduce initial stimulus o
regain
Blood plt decrease
:
Medulla
& Pons
Peripheral
Chemoreceptors
Norve Signal
Respiratory
Blood pH
System Renal
,
getem
-
Positive Feedback Loop : Increases difference between
away from homeostar's
Diagram
setpoint& current value
↑ constant loop till
i
:
enhances a stimulus to
baby is delivered
G
Feed Forward Control : Initiation of
stimulus
response in anticipation of a
↳
of food causes us to salivate
Sight
...
more
Biological Hierachy of Organization
cell
T
Time
Atoms
>
-
organ
Systems
physiology
* Main Rowe is moleuter & their roles in
Molecule
2
:
->
Organism
Organ systems
:
-
=>
-
=
-
-
=
-
-
Compartments of Body Organs
:
>
-
Tissues >
↳ Lumen : Interior of hollow
↳
Cytoplarm
:
Cell
organs
Interior of cells
Fluid Compartments
Body
:
↳ of
-
ICF &ECF = both have
different chemical compositions
body water volume is ICF& / of total body water volume is ECF
total
InterstitiBlood
Plasma
Fluid
Volume Standard for Tony Male : 60% water
↳ 31 blood
The Cell :
Membrane
=
plasma 112 interstitial fluid 201 Intracellular fluid
membrane
plasma
↳
Structural Support
↳
Physical Barrier between ICE& ECF
fluid inclusions
Cytosol Intracellular
ICF
& proteins
Organelles
Cytoplasm
:
:
+
,
,
,
,
=
selectively permeable regulate exchanged
,
regulates communication
Membrane Phospholipid Bilayer
:
↳ Includes ·
:
·
proteins transmembrane Peripheral & lipid-anchored
:
,
Carbohydrates Glycoproteins & lipid
:
·
cholesterol : membrane fluidity &
permeability
0
