SECTION 1: INTRODUCTION
TO PHYSIOLOGY AND CELL
BIOLOGY
Study unit 1.1 Introduction to physiology
The following are characteristic of living things.
- Living things are open systems.
- They maintain a constant internal environment through homeostasis.
- They are composed of cells.
- Have a life cycle.
- Undergo metabolism.
- Grow.
- Adapt to their environment.
- Respond to stimuli.
- Reproduce.
- Evolve.
Homeostasis.
- Is the maintenance of a balance in a living organism.
- Is a dynamic process; ever changing along with conditions.
- Depends on natural resistance to change and regulation to return to normal range.
- Is the maintenance of a constant internal environment by responding to changes.
→ Homeostatic systems always contain
• Receptors (they need to be able to sense signals)
• Control centre (to make sense of signals)
• Effectors (to mitigate an appropriate response)
Numerous features shared by all forms of life:
1. Genetic information stored in the chemical sequence of DNA is duplicated and passed on to
daughter cells.
- Chromosomes store the information required for cellular growth, multiplication, and
function.
2. Linear chemical sequences stored in DNA code for both the linear sequences and three-
dimensional structures of RNAs and proteins.
- Enzymes called RNA polymerases copy (transcribe) the information stored in genes into
linear sequences of nucleotides of RNA molecules.
, - Genetically encoded control circuits consisting of proteins and RNAs respond to
environmental stimuli through signaling pathways.
- Epigenetic controls involve modifications of DNA or associated proteins that affect gene
expression.
3. Macromolecular structures assemble from subunits.
- Many cellular components form by self-assembly of their constituent molecules without the
aid of templates or enzymes.
- Allows for diversity of identical building blocks.
4. Membranes grow by expansion of pre-existing membranes
- Grow only by expansion of pre-existing lipid bilayers rather than forming de novo.
- Following fluid mosaic model: lipids and proteins are packed withing the lipid bilayer and
have some degree of free movement about the bilayer
- Living organisms are surrounded by a membrane.
5. Signal-receptor interactions target cellular constituents to their correct locations.
- Spatial targeting a form of regulation.
- Depend on protein motifs/signals.
- Soluble proteins start at ribosomes.
- Membrane proteins are carried by vesicles to the target membrane.
6. Cellular constituents move by diffusion, pumps, and motors.
- Most small molecules move through the cytoplasm or membrane channels by diffusion.
- Energy provided by ATP hydrolysis or electrochemical gradients is required for molecular
pumps to drive molecules across membranes against concentration gradients.
- Motor proteins use energy from ATP hydrolysis to move organelles and other cargo along
microtubules or actin filaments.
7. Receptors and signaling mechanisms allow cells to adapt to environmental conditions.
- The reception of chemical or physical stimuli from outside the cell is followed by processing
of these stimuli to change the behavior of the cell.
- Multitude of stimuli, including nutrients, growth factors, hormones, neurotransmitters, and
toxins.
- Stimulation of receptors activates diverse signal-transducing mechanisms that amplify the
message and generate a wide range of cellular responses.
8. Molecular feedback mechanisms control molecular composition, growth, and differentiation.
- Feedback control is the regulation of prior steps in a pathway by downstream products of
that pathway.
,Body planes:
, Body cavity:
- any fluid-filled space in a multicellular organism other than those of vessels (such as blood
and lymph vessels)
- Contain an organ or multiple organs.
Thoracic cavity:
- 2 pleural cavities
- Mediastinum (heart, oesophagus, trachea, thyroid)
Abdominal cavity:
- Lower oesophagus
- Small intestine
- Colon
- Rectum
- Liver
- Gallbladder
- Pancreas
- Spleen
- Kidneys
Pelvic cavity:
- Bladder
- Reproductive organs
TO PHYSIOLOGY AND CELL
BIOLOGY
Study unit 1.1 Introduction to physiology
The following are characteristic of living things.
- Living things are open systems.
- They maintain a constant internal environment through homeostasis.
- They are composed of cells.
- Have a life cycle.
- Undergo metabolism.
- Grow.
- Adapt to their environment.
- Respond to stimuli.
- Reproduce.
- Evolve.
Homeostasis.
- Is the maintenance of a balance in a living organism.
- Is a dynamic process; ever changing along with conditions.
- Depends on natural resistance to change and regulation to return to normal range.
- Is the maintenance of a constant internal environment by responding to changes.
→ Homeostatic systems always contain
• Receptors (they need to be able to sense signals)
• Control centre (to make sense of signals)
• Effectors (to mitigate an appropriate response)
Numerous features shared by all forms of life:
1. Genetic information stored in the chemical sequence of DNA is duplicated and passed on to
daughter cells.
- Chromosomes store the information required for cellular growth, multiplication, and
function.
2. Linear chemical sequences stored in DNA code for both the linear sequences and three-
dimensional structures of RNAs and proteins.
- Enzymes called RNA polymerases copy (transcribe) the information stored in genes into
linear sequences of nucleotides of RNA molecules.
, - Genetically encoded control circuits consisting of proteins and RNAs respond to
environmental stimuli through signaling pathways.
- Epigenetic controls involve modifications of DNA or associated proteins that affect gene
expression.
3. Macromolecular structures assemble from subunits.
- Many cellular components form by self-assembly of their constituent molecules without the
aid of templates or enzymes.
- Allows for diversity of identical building blocks.
4. Membranes grow by expansion of pre-existing membranes
- Grow only by expansion of pre-existing lipid bilayers rather than forming de novo.
- Following fluid mosaic model: lipids and proteins are packed withing the lipid bilayer and
have some degree of free movement about the bilayer
- Living organisms are surrounded by a membrane.
5. Signal-receptor interactions target cellular constituents to their correct locations.
- Spatial targeting a form of regulation.
- Depend on protein motifs/signals.
- Soluble proteins start at ribosomes.
- Membrane proteins are carried by vesicles to the target membrane.
6. Cellular constituents move by diffusion, pumps, and motors.
- Most small molecules move through the cytoplasm or membrane channels by diffusion.
- Energy provided by ATP hydrolysis or electrochemical gradients is required for molecular
pumps to drive molecules across membranes against concentration gradients.
- Motor proteins use energy from ATP hydrolysis to move organelles and other cargo along
microtubules or actin filaments.
7. Receptors and signaling mechanisms allow cells to adapt to environmental conditions.
- The reception of chemical or physical stimuli from outside the cell is followed by processing
of these stimuli to change the behavior of the cell.
- Multitude of stimuli, including nutrients, growth factors, hormones, neurotransmitters, and
toxins.
- Stimulation of receptors activates diverse signal-transducing mechanisms that amplify the
message and generate a wide range of cellular responses.
8. Molecular feedback mechanisms control molecular composition, growth, and differentiation.
- Feedback control is the regulation of prior steps in a pathway by downstream products of
that pathway.
,Body planes:
, Body cavity:
- any fluid-filled space in a multicellular organism other than those of vessels (such as blood
and lymph vessels)
- Contain an organ or multiple organs.
Thoracic cavity:
- 2 pleural cavities
- Mediastinum (heart, oesophagus, trachea, thyroid)
Abdominal cavity:
- Lower oesophagus
- Small intestine
- Colon
- Rectum
- Liver
- Gallbladder
- Pancreas
- Spleen
- Kidneys
Pelvic cavity:
- Bladder
- Reproductive organs
