1. Pavina, Brittany, Emmelyn
Topic 6.4: Gas Exchange
Ventilation
Movement of air into and out of the lungs during inspiration and expiration. The
diaphragm and ribcage help conduct this movement.
Breathing in brings in oxygen and breathing out removes carbon dioxide.
Alveoli increases surface area for gas exchange. That is why it is more efficient.
Mechanics of Ventilation
Inspiration: Expiration:
External intercostals muscles contract Internal intercostals muscles contract
Diaphragm contracts (drops) Diaphragm relaxes (rises)
Abdominal muscles relax Abdominal muscles contract
Chest volume increases Chest volume decreases
Pressure in lungs decreases Pressure in lungs increases
Air enters Air is pushed out

2. Pavina, Brittany, Emmelyn
Topic 6.5: Nerves, Hormones, and Homeostasis
Nervous system
Central nervous system consists of the brain and spinal cord.
The peripheral nervous system are all the other nervous throughout the body
The nervous system is composed of neuron.
Resting potential: electoral potential across the cell membrane that is not conducting an
impulse. It is maintain by active transport. Outside of the cell is more positive and inside in more
negative.
Action Potential: The depolarization and repolarization of the electrical potential across a cell
membrane as a nerve impulse passes along a neuron.
Synaptic transmission:
1. Nerve impulse reaches terminal end of pre-synaptic neuron
2. . Depolarization causes calcium channels to open and calcium ions rush in.
3. Calcium ions cause synaptic vesicles to move to membrane and fuse.
4. Neurotransmitter in the vesicles are released and moved across the synaptic gap.
5. The neurotransmitter binds with post-synaptic receptors.
6. Sodium channels open causing sodium ions to enter which leads to depolarization.
7. Neurotransmitters are broken down and move back to the pre-synaptic neuron.

3. Pavina, Brittany, Emmelyn
Homoeostasis monitors levels of variables and makes corrections by negative
feedback and mechanisms.
Example: Thermoregulation
Thermoregulation controlled by hypothalamus
Too Cold Too Hot
Arterioles constrict Arterioles dilate
Sweat glands close Sweat glands open
Hairs stand up, trap layer of air Hairs lie flat, no boundary level
Muscles spasm (Shivering) RESULT: Blood Cools
RESULT: Blood Warms
Blood glucose is maintained through the actions of the pancreas and liver
When blood glucose is high:
-Beta cells in the pancreas secrete insulin  liver and fat converts glucose to glycogen
When blood glucose is low:
-Alpha cells in the pancreas secrete glucagon  liver converts glycogen to glucose

4. Pavina, Brittany, Emmelyn
Topic 6.6: Reproduction
Gametes – cells that fuse in fertilization during sexual reproduction
Functions of Testosterone: pre-natal development of male genitalia, secondary sexual
characteristics in puberty, sex drive and aggression
Menstrual Cycle Hormones (controlled by endocrine system)
o FSH: stimulates egg development
o LH: matures egg and causes release (ovulation)
o Estrogen: develops endometrium (uterus lining)
o Progesterone: maintains endometrium; negative feedback on FSH and LH
o HCG: pregnancy hormone – keeps estrogen and progesterone high
o Oxytocin: birth hormone – contractions of uterus
In-Vitro Fertilisation (IVF)
1. FSH and LH given to stimulate multiple egg releases
2. Eggs are collected
3. Eggs are fertilized with father’s sperm in a dish and incubated
4. Fertilized blastocytes are selected and developed into embryos
5. Up to 3 can be selected for implantation – hopefully one will “take”
6. After bedrest and about a month, woman takes pregnancy test. If positive: pregnancy
continues. If not, woman can wait a few months to try again
Arguments for IVF Arguments against IVF
The right to have children Playing god?
Improved medical tech makes it safer than The risk of multiple pregnancies
before
Some governments cover costs on NHS Expensive
Hope is given to those who can’t conceive High emotional costs if it fails
naturally
Termination of excess embryos count as
Unused embryos can be used for later murder?
(dontated or as stem cells)

5. Pavina, Brittany, Emmelyn