Download Human Anatomy and Physiology

Human Anatomy and
Physiology
Mei-Lan Ko
2011 Sep 20th
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Ch 1: A framework for
human physiology
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The scope for human physiology
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Physiology: how living organisms work
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Interest in function & integration
Molecular biology
Genome
Disease:
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pathophysiology
Disruption of homeostasis
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Mechanism and causality
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Mechanist view:
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Physical and chemical laws
Integration
Causal chains: long, multiple
Vitalism:
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Vital force
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A Society of cells
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Cell: the simplest structural unit
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A complex multicelluar organism can be divided and still
retain the functions characteristic of life
Cellular functions
Specialized cells: 200 kinds
 Muscle cell: to generate the mechanical forces
 Nerve cell: to initiate and conduct electric signals
 Epithelial cell: for the selective secretion and absorption of
ions and organic molecules
 Connective-tissue cell: for connecting, anchorig, supporting
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Tissue
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An aggregate of a single type of specialized cell
Muscle tissue, nerve tissue, epithelial tissue, connective
tissue
Extracelluar fluid (matrix)
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consisting: fibers and other protein
Functions:
1): a scaffold for cellular attachments (packing)
2): transmit to the cells information (adhesion/recognition)
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Organ: composed of the 4 tissues
Organ system: 10 organ systems
 In vitro, in vivo
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Muscle Cells and Tissues
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3 types of muscle cells:
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Cardiac
Smooth
Skeletal
involuntary
voluntary
Muscle cells with be covered in depth in
Ch 9
Neurons and Nervous Tissue
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A Neuron
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nervous tissue:
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A collection of neurons
brain or spinal cord
a nerve
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a cell of the nervous system
is specialized to initiate, integrate and conduct electrical
signals to other cells
Axons from many neurons are packaged together along with
connective tissue to form
Neurons, nervous tissue, and the nervous system will
be covered in Chapter 6.
Epithelial cells and epithelial tissue
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Epithelial cells
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are specialized for the selective secretion and absorption of ions and
organic molecules, and for protection.
cuboidal (cube-shaped), columnar (elongated), squamous
(flattened) and ciliated.
Epithelial tissue
 form from any type of epithelial cell.
 Epithelia may be arranged
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in single-cell thick tissue, called a simple epithelium,
or a thicker tissue consisting of numerous layers of cells, called a
stratified epithelium.
The type of epithelium that forms in a given region of the body
reflects the function of that particular epithelium.
 For example, inner surface of the main airway, the trachea,
consists of ciliated epithelial cells (see Chapter 13).
Epithelial cells and epithelial tissue
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Epithelia are located
 at the surfaces that cover the body or individual organs
 the inner surfaces of the tubular and hollow structures within
the body.
Epithelial cells rest on an extracellular protein layer called the
basement membrane.

The side of the cell anchored to the basement membrane is
called the basolateral side; the opposite side, which typically
faces the interior, is called the apical side.
 the two sides of all the epithelial cells in the tissue may
perform different physiological functions.
In addition, the cells are held together along their lateral
surfaces by extracellular barriers called tight junctions
 boundaries between body compartments and to function as
selective barriers regulating the exchange of molecules.
Epithelial Cells
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Epithelial tissue
(= epithelium)
Forms barrier
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separates body from
external environment
lines hollow organs
forms glands
Copyright © 2005 Pearson
Education, Inc., publishing as
Benjamin Cummings.
Figure 2.1c
Figure 1-2
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Connective tissue cells and
connective tissue
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Connective tissue cells connect, anchor,
and support the structures of the body
Types of connective tissues include:
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Loose Connective
Dense Connective
Blood
Cartilage
Adipose
What surrounds the cells?
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the extracellular fluid and extracellular matrix
(ECM)
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ECM consists of a mixture of proteins, polysaccharides,
and in some cases, minerals
The matrix serves two general functions:
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The proteins of the extracellular matrix consist of fibers
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(1) It provides a scaffold for cellular attachments
(2) it transmits information, in the form of chemical messengers, to the cells
to help regulate their activity, migration, growth, and differentiation.
ropelike collagen fibers
rubberband-like elastin fibers
a mixture of nonfibrous proteins that contain carbohydrate.
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Organs and Organ Systems
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Organs are composed of multiple tissue
types (example: blood vessels have layers
of smooth muscle cells, endothelial cells
and fibroblasts).
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Organ systems contain multiple organs
that work together (example: the urinary
system has the kidney, ureters, urethra,
bladder).
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Organ systems
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Circulatory
Respiratory
Digestive
Urinary
Musculoskeletal
Immune
Nervous
Endocrine
Reproductive
integumentary
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Internal environment
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Equal to the extracellular fluid
Homeostasis
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Internal environment: relative constancy
changes:
 small
 within narrow limits
Activities of cells
 Minimal requirements for maintaining individual
integrity and life
 Perform specialized activities: maintaining the stable
internal environment
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Cell: intracelluar fluid (2/3)
Extracellular fluid (1/3)
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Surrounding cells: interstitial fluid: 80% X(1/3)
Inside blood vessels: plasma: 20% X(1/3)
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Compartmentalization
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Membrane: intra & extracellular fluid
Cellular walls of Capillaries: interstitial fluid &
plasma
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Figure 1-3
ICF
ISF
plasma
organs
internal environment
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external
environment
Exchange and communication are key concepts
for understanding physiological homeostasis.
Homeostasis: a defining
Features of physiology
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Defined: a state of reasonably stable balance
between the physiological variables
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Dynamic process
Time-averaged meannormal baseline value
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Eg: hormone in blood 24-hour urine sample
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Blood glucose levels increase after eating
Levels return to their set point via homeostasis
dynamic constancy.
Figure 1-4
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Figure 1-5
(e.g., decreased room temperature
causes increased heat loss
from the body, which leads to a
decrease in body temperature, etc.)
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System Controls
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Feedback loops or systems are a common
mechanism to control physiological processes.
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A positive feedback system (also called a feed
forward) enhances the production of the
product.
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A negative feedback system shuts the system
off once the set point has been reached.
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Figure 1-6
Negative
Feedback
“Active product” controls the sequence of chemical reactions
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by inhibiting the sequence’s rate-limiting enzyme, “Enzyme A.”
General characteristic of
homeostatic control systems
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Steady state
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Equilibrium
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Variable: no change
Input of energy (+)
Variable: no change
Input of energy (-)
Feedback
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Negative : cortisol
Positive: sodium channel
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Resetting of set points
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Eg: fever, decrease in iron during infecton
A rhythmical basis every day
Multiple systems control a single parameter
Feedforward regulation
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Anticipates changes in a regulated variable to
reduces the amount of deviation from the set
point.學習的結果
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Eg: temperature sensitive nerve cells in the skin
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A strategy for exploring homeostasis (see
Tables 1-2 & 1-3)
• Identify the internal environmental variable.
example: concentration of glucose in the blood
• Establish the “set point” value for that variable.
example: 70 to 110 mg glucose/dL of blood
• Identify the inputs and outputs affecting the variable.
example: diet and energy metabolism
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Components of homeostatic
control systems
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Reflexes
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Basic reflex
Learned reflex
Local homeostatic responses
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Stimulus ( ext or internal environment)
→alteration of cell activity
Occur in the area of stimulus
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Eg: tissue injury
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Reflexes
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A reflex is a specific involuntary
The pathway mediating a reflex is known as the reflex arc.
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stimulus, receptor, afferent (incoming) pathway, integration center,
efferent (outgoing) pathway, and effector.
The pathway the signal travels between the receptor and the
integrating center is known as the afferent pathway.
The pathway along which information travels away from the
integration center to the effector is known as the efferent pathway
An integrating center
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often receives signals from many receptors, some of which may respond to
quite different types of stimuli.
the output of an integrating center reflects the net effect of the total afferent
input;
it represents an integration of numerous bits of information.
Nerve system
Endocrine gland
Nerve fiber
Blood borne messenger
Muscle
gland
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Non-nerve Reflexes
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Almost all body cells can act as effectors in homeostatic
reflexes.
two specialized classes of tissues
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muscle and gland
that are the major effectors of biological control systems.
Glands: the effector may be a hormone secreted into the blood
A hormone is a type of chemical messenger secreted into the
blood by cells of the endocrine system (see Table 1–1)
Hormones may act on many different cells simultaneously
because they circulate throughout the body.
Intercellular Chemical Messengers
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Intercellular communication
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Hormone
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blood
Hormone secreting cells
target cells
neurotransmitter
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Nerve cells
effector
Neurotransmitter
paracrines
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Chemical Messengers
• Chemical messengers participate not only in reflexes,
but also in local responses.
• Communication signals in three categories
• Endocrine: signal reaches often-distant targets after transport
in blood.
• Paracrine: signal reaches neighboring cells via the ISF.
• Autocrine: signal affects the cell that synthesized the signal.
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Paracrine/autocrine agents
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Synthesized by cells
extracellular fluid
Not into the blood stream
Local negative effect: often serve to oppose the
effects induced locally by the neurotransmitter or
hormone
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Points to Remember
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A neuron, endocrine gland cell, and other cell
types may all secrete the same chemical
messenger.
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a particular messenger may function as a
neurotransmitter, as a hormone, or as a
paracrine/autocrine substance.
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Example: Norepinephrine is a neurotransmitter in the brain
and is also produced as a hormone by cells of the adrenal
glands.
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Other Types of Cell Communication
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two important types of chemical communication
between cells that do not require secretion of a chemical
messenger.
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Gap junctions (physical linkages connecting the cytosol
between two cells) allow molecules to move from one cell to an
adjacent cell without entering the extracellular fluid.
Juxtacrine signaling is the chemical messenger not actually
being released from the cell producing it, but rather is located in
the plasma membrane of that cell. When the cell encounters
another cell type capable of responding to the message, the two
cells link up via the membrane-bound messenger.
Processes related to
homeostasis
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Adaptation
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Favor survival in specific environments
Change in genetic endowment
Acclimatization
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The improved functioning of an already existing
homeostatic system
No change in genetic endowment
Increase capacity to withstand change
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↑cell: number, size, sensitivity
Reversible( except developmental acclimatization)
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Biological rhythms
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Circadian rhythm
 Activating homeostatic mechanisms at times before
challenge occur
 Most: internally driven
 Environmental factors provide the timing cues for
entrainment
 Free running rhythm: no environment factors
 Jet lag: to reset the internal clock
phase-shift
rhythms
 Hypothalamus: pacemaker of body rhythms

To pineal gland
melatonin
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asleep
Figure 1-10
A full analysis of the
hormone cortisol requires
not only knowledge of the
signals that cause its
synthesis and secretion
but also consideration
of biological rhythms.
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asleep
What have biological rhythms to do with
homeostasis?
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They add an anticipatory component to homeostatic control
systems and in effect are a feed-forward system operating
without detectors.
The negative-feedback homeostatic responses are
corrective responses. They are initiated after the steady
state of the individual has been perturbed.
Biological rhythms enable homeostatic mechanisms to be
utilized immediately and automatically by activating them at
times when a challenge is likely to occur but before it
actually does occur.
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Balance in the Homeostasis of
Chemical Substances in the Body
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Many homeostatic systems regulate the balance
between addition and removal of a chemical
substance from the body.
Two important generalizations concerning the
balance concept:
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(1) During any period of time, total-body balance
depends upon the relative rates of net gain and net loss
to the body;
(2) the pool concentration depends not only upon the
total amount of the substance in the body, but also upon
exchanges of the substance within the body.
Figure 1-11
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Some of the potential inputs and outputs that can
affect the “pool” of a material (like glucose) that is a
dynamically regulated physiological variable.
Figure 1-12
Sodium homeostasis: Consuming greater amounts of dietary sodium
initiates a set of dynamic responses that include greater excretion of
sodium in the urine. Though not shown here, the amount excreted
would likely exceed the amount ingested until the “set point” is restored.
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