Introduction
Anatomy is the branch of biology concerned with the study of the
structure of organisms and their parts. It is concerned with the shape,
size, position, structure, blood supply and innervation of different
organs.
Intro…..
Anatomy is d ivided into : macroscopic /gross anatomy : the examination
of an animal's body parts using unaided eyesight (naked eye)
microscopic anatomy : involves the use of optical instruments
(microscope) in the study of the tissues of various structures, known
as histology and also in the study of cells .
Studied through dissection of cadavers and medical imaging technique
like X -ray, USG (video x -ray), CT scan, MRI.
Intro ….
Physiology is the branch of biology that deals with the scientific study of
the normal function in living organism.
Divided into various sub branches like: animal physiology (including
that of humans), plant physiology, cellular physiology, microbial
physiology, bacterial physiology, and viral physiology.
In medicine, a physiologic state is one occurring at normal body
function.
Physiologic state is different at different stage such as childhood, youth,
old age, pregnancy, lactation, during rest & exercise, different
environmental temperature, pressure.
Why to study Anatomy and physiology?
As a basis of medicine:
Trillions of cells bathed by
a fluid (internal or immediate environment) of right
composition at appropriate pH, temperature
and osmolarity .
Coordinated and cooperative activity of all parts of body to maintain the
relative constancy of internal environment is called Homeostasis
(Homoios : similar, Stasis: position).
Threat to homeostasis is the disease , hence health care workers like
nurses, doctors, laboratory/ radiology technologists, pharmacist should
have the knowledge of homeostatic mechanism through reading with
Anatomy and physiology.
Cell
The human body has 50 to 100 trillion of these tiny building blocks
Fig. Cell diversity
Types of transport across cell membrane
Transport across cell membranes may be governed only by
physical processes, the membrane acting like any non -living
semipermeable structure. In such cases the transport is called
passive.
Or , the transport may involve expenditure of biologically
produced energy ATP. In such cases the transport is called active .
PASSIVE TRANSPORT :
o Passive transport across the cell membrane depends on physi -
cal factors such as concentration gradient, electrical gradient
and pressure gradient .
o In addition, it depends on the permeability of the membrane .
o Permeability of the cell membrane to a substance depends on
its molecular size, lipid solubility, and whether a special
protein (called carrier) is available to shuttle the substance
across the membrane .
Small molecules or ions are transported faster because they
can pass through „pores‟ in the cell membrane .
Lipid soluble substances are transported faster because such
substances can „dissolve‟ in the lipid bilayer of the cell
membrane and cross it.
The major processes by which passive transport is accom -
plished are :
a. S imple diffusion,
b. F acilitated diffusion and
c. O smosis .
a. Simple diffusion
If the substance is present on both sides of the membrane, the
frequency of collisions is higher on the side on which the
substance is present in a higher concentration . Higher the
frequency of collisions, greater is the probability of particles
striking a pore through which they can pass to the other side of the
membrane. Or, in case of lipid soluble substances, higher the
concentration , greater is the probability of the particles
striking the membrane and „dissolving‟ in it and passing to the
other side.
Hence substances diffuse from the side on which they
are present in a higher concentration to one on which
the concentration is lower .
The concentration of the solute is higher on side A than
on side B. Hence random molecular motion results in
transport from A to B at a rate higher than that from B to A.
Thus the net transport is from A to B .
b. Facilitated Diffusion
Transport by diffusion may be made faster , and the
limitation of molecular size overcome , if a suitable
carrier is available in the cell membrane.
The carrier helps incorporate even a water soluble
substance in the membrane. Since the carrier merely
facilitates diffusion, the process is called facilitated
diffusion
3. Osmosis
Osmosis is a special instance of diffusion . Suppose a
selectively permeable membrane (often erroneously called a
semi -permeable membrane) separates two compartments.
The membrane allows water to pass through but not a solute .
On side A is water, and on side B is the solute dissolved in water.
The membrane is permeable only to water, and the concentration
of water is higher on side A.
Hence water diffuses from A to B ,
but in this type of situations water
is said to be transported by osmosis .
The net flow of the solvent stops when
the excess hydrostatic pressure on side
B just counterbalances the osmotic
pull exerted by the solute.
a and b, hydrostatic pressure in
compartment A;
c and d, hydrostatic pressure in compartment B; OP, osmotic
pressure.
Active transport
Like carrier -mediated facilitated diffusion, requires carrier
proteins that combine specifically and reversibly with the
transported substances.
However , facilitated diffusion always honors concentration
gradients because its driving force is kinetic energy .
In contrast, the active transporters or solute pumps move
solutes, most importantly ions (such as Na +, K +, and Ca 2+ ),
“uphill” against a concentration gradient .
To do this work, cells must expend the energy of ATP .
There are two types of active transport distinguished
according to their source of energy .
In primary active transport , the energy to do work comes
directly from hydrolysis of ATP .
In secondary active transport , transport is driven
indirectly by energy stored in ionic gradients created by
operation of primary active transport pumps .).
Secondary active transport systems are all coupled systems;
that is, they move more than one substance at a time .
If the two transported substances are moved in the same
direction , the system is a symport system (sym = same).
If the transported substances “ wave to each other ” as they
cross the membrane in opposite directions , the system is an
antiport system (anti = opposite, against)
Fig. Primary active
transport,
Sodium/potassium
pump
Na +/K + pump: a primary active pump
The carrier protein is a complex of two separate globular
proteins : a larger one called the α subunit, with a
molecular weight of about 100,000, and a smaller one
called the β subunit , with a molecular weight of about
55,000.
Although the function of the smaller protein is not known
(except that it might anchor the protein complex in the lipid
membrane), the larger protein has three specific features
that are important for the functioning of the pump :
It has three receptor sites for binding sodium ions on the
portion of the protein that protrudes to the inside of the cell.
It has two receptor sites for potassium ions on the outside .
The inside portion of this protein near the sodium binding
sites has ATPase activity.
Fig. Postulated mechanism for sodium co -transport of glucose
SECONDARY ACTIVE TRANSPORT
For some cells, such as electrically active nerve cells, 60 to 70
percent of the cells' energy requirement m ay be devoted to
pumping Na + out of the cell and K + into the cell.
The Na +-K + Pump Is Important For Controlling Cell Volume
At two places in the body, primary active transport of
hydrogen ions is important:
(1) In the gastric glands of the stomach H +/K + ATPase for
the release of hydrogen in stomach during HCl
production .
(2) In the late distal tubules and cortical collecting ducts of
the kidneys for ion releasing (H +) in urine.
Two primary active transport of calcium pumps; muscle
contraction
1. One is in the cell membrane and pumps calcium to the
outside of the cell.
2. The other pumps calcium ions into one or more of the
intracellular vesicular organelles of the cell, such as the
sarcoplasmic reticulum of muscle cells and the
mitochondria in all cells.
Secondary active transport .
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