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

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.

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

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

Improved medical tech makes it safer than before

Some governments cover costs on NHS

Hope is given to those who can’t conceive naturally

Unused embryos can be used for later (dontated or as stem cells)

Playing god?

The risk of multiple pregnancies

Expensive

High emotional costs if it fails

Termination of excess embryos count as murder?

Pavina, Brittany, Emmelyn