week nine - Homeostasis

Internal conditions need to be kept steady. THe balance is refered to as homeostasis.

Things that need to be kept in balance:

Water - In sweat, vapour, urine, faeces

Temperature - Maintains the optimum temperature for processes / emzymes

Ions - Managed by the kidneys - Calcium, chloride, copper

Blood Glucose - controlled by the pancreas.


Hormones
One of the body's system of communication

Nervous system:
-Electrical impulses
-Chemicals
-Neurones

Hormones:
-Chemicals
-Travel in blood
-Slow
-Released from (endocrine) glands indirectly to Target Organs


The menstrual cycle.

1.Folicle stimulating hormone (FSH) is produced in the pituitary gland

2. It eventually gets to the ovaries where it causes an egg to mature in ovary

3. the process causes oestrogen to be released in response, makes its way to pituitary gland to confirm.

4. the Pituitary gland then releases Leuterising Hormone (LH) This causes the matured egg to be released from the ovary.


Looking at this process gives us some clues about fertility and contraception

FSH is given in fertility treatment to increase the likelyhood of conception
This treatement causes many eggs to mature > multiple births

Contraception
In contraception, FSH is inhibited. Oestrogen is given to block and stop FSH

Excess oestrogen can have side effects:

Greater risk of breast cancer
It can be difficult to restart cycle if should conception become desirable

For women with history of breast cancer in the family, progesterone is an alternative to oestrogen.

Week Eight - Nervous system

The nervous system and hormones enable us to respond to external changes. They also help us to control conditions inside out bodies. THe menstual cycle is controlled by hormones.

- The nervous system enables humans to react to their surroundings and coordinate their behaviour.

- Receptors detect stimuli which include light, sound, changes in position, chemicals, touch, pressure, pain and temperature.

- Information from receptors passes along cells (neurons) in nerves to the brain. The brain coordinates the response - but not in reflex response.

- Reflex actions are automatic and rapid. THy often involve sensory, relay and motor reurons.

Internal conditions which are controlled include:

-The water content of the body -water leaves the body via the lungs when we breathe out, via the skin when we sweat, and excess water is lost via the kidneys in urine.

-The ion content of the body - Ions are lost via the skin when we sweat and excess ions are lost via the kidneys in the urine.

-Temperature - to maintain the temperature at which enzymes work best

-Blood sugar levels - to provide the cells with a constant supply of energy.


Reflex action. such as: blinking, sneezing, pupil dilation, knee jerk.

Stimulus > Sensory Neuron > Relay neuron > Motor Neuron

Between each neuron there is a gap, a synapse, neuro-transmitter passes this gap via active transport. The more frequent the stimulus, the more frequent the electrical signal and greater neuro-transmitter.

Proper week seven - Exchange surfaces

Echange surfaces

• Lungs
• Villii
• Stomata
• Root hairs

THe lungs are located in the thorax, beneath them is the diaphragm, a sheet of stong tissue with muscles attached. THe diaphragm can only move thanks to these diaphragm muscles. WHY NOT DIAFRAM?! They are behind the ribcage. The intercostal muscles of the ribcage can contract to draw the ribs up.

Two types of breathing.

Shallow: Diaphragm muscles contract and relax ( 14 breaths per minute at rest)

Deep: Diaphragm muscles contract and relax. Intercostal muscles of the ribs also contract and draw the ribcage up and out.

Bronchi>brochiole>alveoli

Alveoli are single ceslls in contact with a rich blood supply, they are moist and facilitate diffusion.




Air in Air out

N - Nitrogen (78%) N - Nitrogen (78%)

O2 - Oxygen (21%) O2 - Oxygen (16%)

CO2 - Carbon Dioxide (0.04%) CO2 - Carbon Dioxide (4&)


Respiration is the release of energy from glucose in cells - Anaerobic of anaerobic. All living things respire (virus doesn't respire independently)

Breathing is moving air in and out of the lungs.


Root Hairs have a high surface are to absorb wate and mineral salts. THe surface area of roots and leaves has hairs to increase absorbtion of water.

Stomata (on leaves)

• Gaseous exchange
• Surface area for photosynthesis
• can open and close (fill with water)

There is more to add to this week, but it is late and I am tired. Modify later.

Links of excitement but possible dashed hopes

http://www.discoveryon.info/2009/10/master-mechanism-behind-regeneration.html

http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000197

http://her.oxfordjournals.org/cgi/content/abstract/cym084v1

http://learn.genetics.utah.edu/content/begin/cells/scale/

http://imascientist.org.uk/download-science-debate-kits/

Weeeeeeeek seven

No lesson today. Here is a picture of passive face shoes.

Week 6 My exam result!

Har Har Har! 80%!

... Yes, I did get my name wrong first time, but I didn't lose points for it.

Week 6: the heart - Dissection and excercise

Here are some pictures of a sheep's heart that I dissected.

1.This is a sheep's heart. It is not complete, only the lower ventricles remain. Also shown is a pair of sharp scissors that I used to cut it with. See it here Here is a closeup. See it here.
You can see the stumpy remains of the Vena Cava and the Pulmonary vein. Pulmonary is probably latin for lungs. Had the butcher left the organ whole, there would have been the Pulmonary Artery and the Aorta. There would also have been the left and right aorta. Both of those are thick tubes. They have to be thick to contain the high pressures that they are exposed to. Blood exits the heart thru the ARTERIES. Blood re-enters the heart thru veins. Arteris branch and narrow until they become capillaries. Capillaries have thin walls.

Substances needed by cells in the body tissues pass out of the blood, and substances produced by the cells pass into the blood through the walls of the caplillaries.

2. The first cut. See it here.
Clearly one ventricle has a thicker wall than the other. The left ventricle is strong. After welcoming the oxyhaemoglobin from the lungs, it then has to propell the blood all the way around the body, visiting all of the organs.

3. The second cut. See it here.
What's that between the left ventricle and atrium? Its a mitral valve. Its stops blood going the wrong way.
There is a similar one between the right ventricle and atrium called the tricuspid valve


Excercise

• Increases heart rate
• increases breathing rate in response to greater co2 - need for more 02
• all blood vessels to muscles dilate (more blood > more oxygen > greater capacity to expell co2 and lactic acid.)
• Increases respiration rate
• ^accumulation of lactic acid

Respiration happens in the cells. It is the increased presence of carbon dioxide that initiates increase in breating rate.


Respiration (aerobic)

Glucose + oxygen > Carbon dioxide + water + Energy


Respiration (anaerobic, no 02)

Glucose is broken down without oxygen > lactic acid + energy.
Lactic acid must be taken away, it is a toxin. Lactic acid is taken to the liver to be oxidised. Until this has happened, it is said there is an oxygen dept.

THere is a store of glucose in the muscles for use in respiration. Glycogen. Glycogen = lots of glucose molecules. Anaerobic respiration begins after 5 seconds of intense activity



During excercise

• Heat rate increases - increase o2 thru the lungs and carries out co2
• Increase breathing rate - Co2 out, O2 in.
• Arteries supplying the muscles dilate
• Blood flow which aids digestion lowers - Blood supply varies

The energy that is released during respiration is used to enable muscles to contract.

During excersice a number of changes take place

• Heart rate increases
• Rate and depth of breathing increases
• the arteries supplying the muscles dilate

These changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide

Glycogen stores in the muscles are used during excercise.

If muscles are subjected to long periods of vigourous activity they become fatigued, ie, they stop contracting efficiently. If insuuifient oxygen is reaching the muscles they use anaerobic respiration to obtain energy.

Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid. As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration. Anaerobic respiration results in oxygen debt that must be repaid in order to oxidize lactic acid to carbon dioxide and water.





"i wish i was a helicase enzyme, because i'd love to unzip your genes..."
"Went to the shop to buy a bottle of energy. 'That'll be ATP' said the shopkeeper."