The Body And Its Internal Environment

Question 0

List the organelles of the cell.

Answer 0

• Plasma membrane
• Nucleus
• Mitochondria
• Ribosomes
• Endoplasmic reticulum (rough and smooth)
• Golgi apparatus
• Lysosomes

Question 1

What is the difference between prokaryotic and eukaryotic cells?

Answer 1

• Eukaryotic - multicellular organism, membrane bound nucleus/nucleolus, bigger than prokaryotic, simple cell wall (if present at all), extensive organelles and cytoskeleton.
• Prokaryotic - single cell organism, no nucleus, much smaller, complex cell wall, no organelles, no cytoskeleton
• BOTH - flagella, plasma membrane, cell division, cytoplasm, ribosomes and chromosomes

Question 2

What are the characteristics and function of epithelium tissue?

Answer 2

• A group of tissues found covering the body and lining of the cavities and tubes.
• Functions - protection, secretion and absorption
• Cells are closely packed and lie on a ‘basement membrane’.
• Can be ‘simple’ or ‘stratified’

Question 3

What is simple epithelium?

Answer 3

• A single layer of flattened cells fit very close together like pavement, forming a very smooth and thin membrane.
• Divided into 4 types (squamous, cuboidal, columnar, ciliated)
• Usually found an absorptive or secretory surfaces where the single layer enhances these processes

Question 4

What is stratified epithelium?

Answer 4

• Several layers of cells of various shapes.
• Superficial layers grow up from below.
• Protects underlying structures.
• 2 types (stratified and transitional)

Question 5

Describe the general composition of connective tissue.

Answer 5

• The cells forming the connective tissue are more widely separated from each other than epithelium.
• Sometimes contain fibres present in the matrix, which may be of a solid jelly-like consistency or dense and rigid depending on the position and function.
• Functions - binding and support, protection, transport and insulation.

Question 6

What is the difference between connective tissue and specialised connective tissue?

Answer 6

• Connective Tissue - connects and supports, connects cells together and provides physical support such as inflammation.
• Specialised Connective Tissue - consists of an extra cellular matrix made up of proteins, tissue fluid and fibres. Found in bone and cartilage (hard tissues with high density).

Question 7

Describe homeostasis and the factors affecting it.

Answer 7

’ A tendency towards the stability of the internal environment of a healthy organisms’
- Affected by temperature, water/electrolytes, acidity (pH), glucose levels, O2 and CO2 levels, blood pressure.

Question 8

How is homeostasis controlled?

Answer 8

• It is controlled through negative feedback and continuous activity of the receptors.
• Control measures aim to maintain a variable (change in internal environment) as it’s set point (value at which variable must be maintained for health’

Question 9

What is the difference between negative and positive feedback?

Answer 9

• NEGATIVE FEEDBACK-
  The effector response decreases or negates the effect of original stimulus, restoring homeostasis. Most of homeostatic controls in the body utilise negative feedback to prevent serious changes in the internal environment.
• POSITIVE FEEDBACK -
  The effector and it’s response further increase the original stimulus, triggering a cascade reactions. There are only a few systems that use this (blood clotting and contractions during birth)

Question 10

List 5 physiological variables controlled by negative feedback.

Answer 10

• Body temperature
• Blood volume
• Blood sugar
• Blood pressure
• Osmolarity of blood

Question 11

Why is water important?

Answer 11

• It is a universal solvent (a lot of things are dissolved in water)
• Chemical reactions occur in water.
• It is a major component of plasma and cells.
• It lubricates joints and keeps organs healthy (e.g. synovial fluid)
• It retains heat remarkably well.

Question 12

How is water balance maintained?

Answer 12

• Water balance always needs to be maintained to achieve homeostasis.
• Increase water - drinking, food, water of metabolism
• Decrease water - urine, stools, sweat, respiratory loss

Question 13

Define body fluid compartments and state their relative proportions.

Answer 13

• Total body water (40L)
• Extracellular Fluid (12L) - fluid in the blood and lymph vessels, cerebral spine fluid and fluid in the interstitial spaces in the body.
• Intracellular Fluid (28L) - high in potassium and magnesium, low in sodium and chloride. Everything ‘inside’ cells.

Question 14

Describe how fluid moves in-between compartments.

Answer 14

• DIFFUSION-
  Movement from an area of high concentration to an area of low concentration across a semi-permeable membrane until equal concentration on both sides is achieved. Diffusible substances must be smaller than pores in membrane.
• OSMOSIS -
  The diffusion if water across a semi-permeable membrane when equilibrium cannot be achieved by diffusion of solutes (too big for the pores). The force with which this occurs is ‘osmotic pressure’ - a ‘pull’ of fluid from high concentration to low concentration.

Question 15

Define solute and solution.

Answer 15

• Solute - An electrocyte dissolved substance or particle.

- Solution - A homogenous mixture of one or more dissimilar substances.

Question 16

What is the difference between Osmolarity and Osmolality?

Answer 16

• Osmolarity - number of osmoles/L of a solution.

- Osmolality - number if osmoles/KG of a solution.

Question 17

Explain tonicity.

Answer 17

• The ability of a solution to affect the cell.
• Can be isotonic, hypotonic or hypertonic.
• Isotonic - concentration of electrolytes outside of cell is equal to that inside of the cell.
• Hypotonic - has a low concentration of solutes that do not pass the membrane (cell may burst)
• Hypertonic - high concentration and low concentration do not cross the membrane (cell shrinks)

Question 18

Define the term ‘electrolytes’

Answer 18

• Electrolytes are ions that are electrically charged.
• They affect the amount of water in your body, the acidity of your blood, your muscle function and other important processes.
• They move across plasma membrane by diffusion then water follows - osmosis.

Question 19

List the common electrolytes and their functions.

Answer 19

-SODIUM-
Most dominant extracellular ion, creates osmotic pressure. Needed for nerve conduction and propagation of action potential.
-POTASSIUM-
Nerve conduction (returning cells to it’s resting state after excitation).
-CALCIUM-
Required for healthy bones and teeth and muscle contraction.

Question 20

Explain how substances move in and out of cells.

Answer 20

• Carrier proteins - bind to solutes and transfer them across the membrane, can be active or passive.
• Facilitated diffusion - movement of large molecules that can’t cross the membrane from high concentration to low concentration down the concentration gradient. Does not require energy.
• Active transport - against the concentration gradient, requires ATP
• Sodium-Potassium pump - sodium out, potassium in.
• Exocytosis - eliminating or secretory material from cell.

Question 21

The plasma membrane is freely permeable to:

Answer 21

Steroid hormones

Question 22

In negative feedback control systems involved in homeostatis:

Answer 22

The effector tissue is often a muscle or a gland

Question 23

Homeostatis:

Answer 23

Usually involves the continuous activity of sensory receptors

Question 24

The cell organelle responsible for protein synthesis is:

Answer 24

Ribosomes

Question 25

Extracellular fluid differs from intracellular fluid in adults, is that it’s:

Answer 25

Volume is smaller

Question 26

Prokaryotic cells:

Answer 26

Lack a nucleus

Question 27

Simple cuboidal tissue is found:

Answer 27

In the thyroid gland

Question 28

Collagen is not in the matrix of:

Answer 28

Blood