GCSE AQA Biology B3

Transport system = Vital as BILLIONS of cells are LONG WAY from direct supply of FOOD/OXYGEN.

Circulatory system consists of HEART (pump), VESSELS (pipes), BLOOD (medium)

Double circulation

1st Carries Blood from the Heart to the LUNGS and BACK (right side)

2nd Carries Blood to REST OF BODY (Left side)

Very efficient method of circulation: OXYGENATED blood bought back from lungs and sent to everywheere in Body. Thus cells recieve OXYGENATED blood quicker.

Heart is split into Two parts for DOUBLE CIRCULATION. Wall made out of almost entirely Muscle. Left side thicker as pumps blood to WHOLE BODY.

Blood Vessel + Features

Artery : Carry Blood from HEART to ORGANS. Usually OXYGENATED blood making it bright red. They STRETCH as blood flows through them and then go back to ORIGNIAL SHAPE.

Vein : Carry Blood to HEART. Usually LOW in OXYGEN making it deep purply-red. Dont have Pulse but have VALVES to PREVENT the BACK FLOW of Blood.

Capillary : INSIDE Organs. BETWEEN Arteries (supply blood) and Veins (collect blood). Blood flows through HUGE NETWORK of capillaries. No cell in the body is more than 0.05mm away from a capillary. NARROW with THIN WALLS allowing substances to EASILY DIFFUSE to and from cells.

Plasma = Liquid part of Blood. Yellow in colour. Transports blood cells amongst other things around body. CO2 produced in organs of body carried in plasma back to the lungs.

Red Blood Cells

More red blood cell than any other blood cell in body. Approx. 5 Million RBC's in ea 1mm3 of blood. Average person has 4.7 - 5L of blood. Carry Oxygen from Lungs to tissues and cells in - need.

- Biconcave- pushed in on both sides. Increases surface area for More Oxygen

- Packed with Haemoglobin (special red pigment) to carry Oxygen.

- No Nucleus. More space for Haemoglobin.

Haemoglobin = Large Protein Molecule folded around 4 iron atoms. In high conc. of Oxygen e.g. in Lungs it reacts to form Oxyhaemoglobin. Bright scarlet in colour. In areas where oxygen conc is low, Opposite happens. Oxyhaemoglobin splits to give Oxygen + Haemoglobin.Oxygen can then diffuse to cells.

As Haemoglobin is based on iron , a lack of iron reslts in not enoough red blood cells causing anemia Anaemic people are pale and lack energy due to the fact that they cannot carry enough oxygen round body.

Muscle Overview

Muscles are Vital to move you around & even support you against gravity. Basically, you need it.

Muscle tissue made from PROTEIN FIBRES which contract when suplied with energy (respiration). Need alot of energy 2 contract. Therefore contain many MITOCHONDRIA to supply energy by AEROBIC respiration.

Muscles hav GLYCOGEN stores. Can b Rapidly convertd to GLUCOSE (suplies food needed 4 cellular resp.)

Even at REST, muscles use oxygen & glucose as muscle fibres constantly contract to keep you in position (against gravity). Plus involved in life processes (e.g breathing, blood circulation)

Excercise

During excercies, muscles contract harder, faster. Hence more Oxygen/Glucose needed.Also more CO2 produced which needs to be rid of to keep them working effectively. Therefore during excercise:

-HEART RATE is INCREASED. And ARTERIES supplying blood DILATE (become wider). Thus increasing blood flow to Muscles ---> more Oxygen/Glucose supplied.

- BREATHING RATE is INCREASED. Plus DEEPER BREATHS. Meaning more oxygen breathed into lungs for Red Blood Cells as well as more CO2 REMOVED via breathing out.

Regular excercse benefits Heart and Lungs. Making them larger.Develop more efficient blood supply. Tehrefore they CONSTANTLY perform BETTER.

Muscles

Muscle movements are possible due to Aerobic Resp. (Uses Oxygen). However, during vigorous exercise, might be short supply of Oxygen. Muscles can still get energy from Glucose but need to use ANAEROBIC resp. (Without Oxygen).

After alot of exc., may become FATIGUED (less efficient contracting). This is when they switch to Anaerobic Resp.

Not as effective as aerobic. Glucose not 100% broken down. End products are : LACTIC ACID and water. INstead of CO2 and water.

Anaerobic Respiration : glucose --> Lactic acid (+ energy)

Oxygen Debt

After hard excercise is finished. Still puff and pant. The legth of this depends of personal fitness. This is because Lactic Acid cannot be breathed out (like CO2). Has to be BROKEN DOWN (via OXYGEN) to produce CO2 + Water.

Amount of Oxy. needed to break down Lactic Acid = OXYGEN DEBT

Bigger the debt. Longer you puff and pant

Oxygen debt repayment:

Lactic Acid + Oxygen --> Carbon Dioxide + Water