Transcript Principals of General Zoology (Zoo-103)

Lecture 21: Animal physiology
Animal organ System & Homeostasis:
 Animal organs are usually composed of more than one cell type.
 Each organ typically performs a given function.
 The stomach is an organ composed of tissues that aid in the
digestion of food as part of the digestive system..
 Most organs have functions in only one organ-system.
 Organ systems, such as the digestive system, are collections of
organs ‫ مجموعة األعضاء‬that perform a major function for the
organism.
Homeostasis: ‫ضبط وتنظيم البيئة الفسيولوجية الداخلية للجسم‬
 Homeostasis: is a term describe the physical and chemical
parameters that an organism must maintain to allow proper
functioning of its component cells, tissues, organs, and systems.
 Enzymes function best when a certain range of temperature and
pH, that cells must maintain a balance between having too
much or too little water in relation to their external
environment.
 Our body has a range of environmental (internal & external)
parameters within which it works best.
a)Multicellular organisms accomplish homeostasis by having
organs and systems that coordinate their homeostasis by the
help of the nervous system.
b)Unicellular organisms accomplish homeostasis within a single
cell by moving materials into and out of the cell by regulation
of the cell membrane and its functioning.
 Unicellular organisms such as paramecium, can dump wastes
‫ يُخرج الفضالت‬outside the cell by exocytosis ‫اإلخراج الخلوي‬.
 Multicellular organisms, such as a human, dump wastes outside
cells then, carting away of these wastes outside the body is by
both the circulatory ‫ الدوري‬and excretory ‫ اإلخراجي‬systems.
 Heat control is a major function of homeostatic conditions that
involves the skin, muscular and nervous & circulatory systems.
 The ultimate control of homeostasis is accomplished by the
nervous system (for rapid responses such as quick reflexes) and
the endocrine system ‫( الغدد الصماء‬for longer-term responses,
such as maintaining the body levels of calcium).
Feedback Systems in
Homeostasis
Biological Feedback
 Most physiological systems in the body use
feedback to maintain the body's internal
environment.
Positive feedback:
Causes an amplification
of the stimulus by
the reaction.
 Often this homeostatic control takes the
form of two types of feedback cycles:
I- Positive feedback control:
is used in some cases as input increases or
accelerates the response.
II- Negative feedback control mechanisms:
is used by most of the body's systems, the
information caused by the feedback causes
a reverse response ‫إستجابة عكسية‬.
Negative feedback:
Turns off the stimulus
that caused it in
the first place
Parameters of
homeostasis
‫عوامل الثبات الفسيولوجي‬
Internal components
Internal environment
‫المكونات الداخلية‬
‫البيئة الداخلية‬
Concentration of O2 and CO2
The extra-cellular fluid that
surrounds cells
pH of the internal environment
Plasma of the blood.
Concentration of nutrients
and waste products
Concentration of salts
Volume and pressure of
Extra-cellular fluid
Control Systems of homeostasis
‫األجهزة التي تتحكم في الثبات الفسيولوجي‬
A. Extrinsic control ‫التحكم الخارجي‬:
Most homeostatic systems are extrinsic: they are controlled from outside the
body. For example:
I. The nervous system:
Depends on sensors ‫ مناطق إحساس‬in the skin or sensory organs to receive
stimuli and transmit a message to the spinal cord or brain. Signal is sent to
an effector system, such as muscles or glands, that effects the response to
the stimulus.
II. The endocrine system:
Involves hormones. Sensors detect a change within the body and send a
message to an endocrine effector (parathyroid), which release hormones
into the blood when blood minerals levels are low resulting in raising the
blood minerals levels.
B. Intrinsic control ‫التحكم الداخلي‬:
Local controls usually involve only one organ or tissue. When muscles use
more O2, and also produce more CO2, intrinsic controls cause dilation of the
blood vessels allowing more blood into those active areas of the muscles.
Eventually the vessels will return to "normal".
Body Systems and Homeostasis
A. Muscular System: (facilitates movement and locomotion); The
muscular system produces body movements and body heat.
B. Skeletal System: provides support and protection, and
attachment points for muscles. The skeletal system provides
rigid framework for movement. It supports and protects the
body and body parts, produces blood cells, and stores minerals.
C. Skin ‫ الجلد‬or Integument ‫الجليد‬: (the outermost protective layer);
It prevents water loss and protect the body from invasion of
foreign microorganisms and viruses.
D. Respiratory System:
Moves O2 from the external environment into the internal
environment; also removes CO2. This occurs by exchanging gas
between lungs and the blood. It also maintains pH of the blood
and facilitates exchange of CO2 and O2.
E.Circulatory System:
Transports O2, CO2, nutrients, waste products, immune
components, and hormones via the heart, capillaries, arteries,
and veins. The lymphatic system also transports excess fluids to
and from circulatory system and transports fat to the heart.
F. Immune System:
Defends
the
internal
environment
from
invading
microorganisms and viruses. It provides cells that aid in
protection of the body from disease by the antigen/antibody
response.
G.Excretory System:
Regulates volume of internal body fluids as well as eliminates
metabolic wastes from the internal environment. it removes
organic wastes from the blood. These wastes are then removed
as urine. It is also responsible for maintaining fluid levels.
H.Nervous System:
Coordinates and controls actions of internal organs and body
systems. Memory, learning, and conscious thought are the
functions of the nervous system. Maintaining autonomic
functions )‫ الوظائف الذاتية (الال إرادية‬such as heartbeat, breathing,
control of involuntary muscle actions.
I. Endocrine System:
Works with the nervous system to control the activity of
internal organs. it secretes hormones that regulate body
metabolism, growth, and reproduction.
J. Reproductive System:
Is mostly controlled by the endocrine system, and is responsible
for survival and perpetuation of the species. Organs of this
system produce gametes that combine in the female system to
produce the next generation (embryo).