Biology - Unit 2c - Control, Response and Homeostatsis

What makes up the central nervous system?

The spinal cord which is a long column of neurones(nerve cells) from the base of the brain down the spine. With neurones that branch of to other parts of the body

What is the function of the spinal cord?

To relay information between the body and the brain

What is the brain made up of?

Billions of interconnected neurones

What’s a receptor?

Group of cells that can detect a stimulus

What’s a stimulus?

Change in your enviroment

What are the stimuli for the receptors in the tongue, skin, ear and eyes?

Tongue - chemicals

Skin - pressure/temperature

Ear - sound waves

Eyes - light

Describe the pathway of the reflex arc from the receptor to effector

When a stimuli is detected by a receptor, the information converts to electrical impulses that are sent along the sensory neurone. When the impulses reach the synapse between the sensory neurone and the relay neurone (in the CNS), they trigger chemicals to be released that can diffuse across the synapse. The chemicals then set off a new electrical impulse through the relay neurone. The same thing happens between the relay neurone and the motor neurone. The impluses then travel to the effector, which will either contract of secrete a hormone (depending on whether the effector is a muscle or gland).

What slows down the transmission of a nervous impulse?

The diffusion of chemicals at the synapse takes time

How can reflexes help revent injuries?

They are protective because its goes through an unconsious part of the brain, this means the reflex will be automatic and rapid

What is the sclera?

Tough, white outer coat that covers and protects the eye.

What’s the cornea?

Transparent part of sclera at front of eye. It refracts ligth through pupil

Whats the pupil?

Hole in the middle of the iris

What is the Iris?

Coloured bit of the eye that contains muscle that allow it to control the size of the pupil. This will control the amount of light that enters the eye

What is the lens?

Placed behind the pupil that changes shape to focus the light onto the retina

What is the retina?

The retina is a layer on the inside of the eye which is light sensitive. It contains receptor cells that detect ligth intensity and colour

What is the optic nerve?

It carries impluses from the retina to the brain to form an image

What is the choroid?

A pigmented layer found between the sclera and the retina that contains blood vessels to supply O2 and nutrients to the retina. It also absorbs light which prevents light from preventing off the inside of the eye so the only light reaching the retina comes directly from the lens for a clearer image

What is the blind spot?

A small area in your field of vision that the eye can’t detect any light from. This is because there are no receptor cells where the retina is attatched to the optic nerve

How do we not notice your blind spot?

Your brain automatically fills in the missing part of the image based of the rest of the information it has collected (including the image from other eye)

How can reflexes protect the eye?

Light receptors will detect high light intesity and send impulses along the sensory, relay and motor neurone to the effector that tells circular muscles in the iris to contract which makes the pupil shrink. If the pupil shrinks, it will restrict the amount of light that enters the eye

Blinking is also a protective reflex as it stops the eye from anything touching it

What is homeostasis?

Maintaining a constant internal enviroment

Why does the body keep homeostasis?

So that the body continues to have an optimum temperature/pH and has enough of the right nutrients and water, this is so that all metabolic reactions can occur as they are vital for keeping you alive

What are the two things that your body needs to keep steady?

Blood glucose concentration

Body temperature

What is negative feedback?

Process of bringing the level of something that is too high or too low back to normal

What is a problem with trying to balance out something in the body and how do we fix it?

The effectors will just keep on producing the responses, which might cause the opposite problem, so we use negative feedback to keep regulating it to a balanced level

Why is the body kept at around 37c?

Its the optimum temperature for enzymes in the body

How does your body gain energy?

Through the byproduct of respiration

What is the Thermoregulatory centre ?

It contain receptors that detect the temperature for the blood flowing through the brain. It can also receive nervous impulses from temperature receptors in the skin

Explain how the cycle of the Thermoregulatory centre works

Temperature receptors detect high core body temp

Thermorgulatory centre coordinates information and sends impulses to effectors

Effectors produce a response and counteract the change

The body cools down

Temperature receptors detect low core body temp

Thermorgulatory centre coordinates information and sends impulses to effectors

Effectors produce a response and counteract the change

The body warms up

What happens when the core body temp is too hot?

• Erector muscles relax so hairs lie flat

• Lots of sweat produces - sweat will evaporate and transfer energy from your skin to the enviroment. This is because the water requires energy to change to gas

• Vasodilation - blood vessels near skin surface will dilate and allow more blood to flow near the surface so it can transfer more energy to surroundings because the surface of your skin is cooler that the rest of your body

What happens when your core body temp is too cold?

• Erector muscles contract so hair stand up to trap layer of air for insulation

• Very little sweat is produced

• Vasoconstriction - blood vessels near skin surface constrict and allow less blood flow near the surface so less energy can be transferred

• Shivering - your muscles contract automatically. This will require respiration which transfers energy to warm the body

Whats a hormone and how does it work?

Chemical messenger that control body functions. Released into the blood and carried to other parts of the body parts that particular cells in particular order. They control things that need to be constantly adjusted

Where does glucose enter the blood stream?

Small intestines

Explain what happens to the excess glucose that hasnt been used for either exercise or metabolism of cells?

The excess glucose is converted into insoluble glycogen in the liver. It is then stored in the liver and in muscle cells

What happens when the liver and muscles are too full to store anymore glucose?

The glucose will then be stored at lipids(fat) in the tissues

How does the body keep the level of glucose in the blood steady?

If the pancreas detects a high glucose concentration in the blood then it will secrete a hormone called Insulin directly into the blood. Insulin will travel will the glucose towards the liver. When it reaches the liver, insulin tells the liver to convert the glucose into glycogen which reduces the concentration of glucose in the blood

If the pancreas detects a low glucose concentration in the blood then it will secret a hormone called Glucagon directly into the blood. Glucagon will travel with the glucose towards the liver. When it reaches the liver, glucagon tells the liver to convert glycogen into glucose which increases the concentration of glucose in the blood

Explain Type 1 diabetes

• The pancreas stops producing insulin which makes the blood glucose concentration rise to deathly levels.

• Insulin therapy is needed which involves insulin injections several times a day. They are usually at meal times so that carbohydrates can be removed from the blood straight after its been digested to stop glucose concentration in the blood from getting too high. The amount od inslulin being injected depends on the persons diet and how active they are.

• They also need to watch their intake of food rich in simple carbohydrates which cause the gucose in blood to rise rapidly. They should also take regular exercise which will remove excess glucose from the blood

Explain Type 2 diabetes

• A person becomes resistant to insulin or pancreas doesnt produce enough insulin which cuases high glucose levels in the blood which can be deadly

• Being overweight will increase chances of developing type 2 diabetes because you are consuming so much carbohydrates that your cells stop responding to the insulin and become resistant to it

• They should have a healthier diet and exercise regularly

Why are complex carbohydrates better for you than simple carbohydrates?

Complex carbohydrates take long to be broken down. This means your body can easily use up most of the glucose being produced as its over a longer period of time. This also means your body wont get a insulin spike, which can cause the development of inslulin resistance over time.

Whereas, simple carbohydrates have a simple structure that can be broken down much quicker and so your body wont be able to use up most of the glucose in a shorter amount of time which means it will be stored as fat

Whats a depressant and give an example

A substance that reduces the activity of the nervous system and slows down reaction time as it effects chemical processes in the body e.g. alcohol

What are 6 things that drinking too much alcohol lead to?

Impaired judgment, poor balance, poor coordination, slurred speech, blurred vision and sleepiness

How can alcohol damage your body?

Toxic products are produced when its broken down by enzymes in your liver. Over a long period of time these toxic products can cause the death of liver cells, forming scar tissue that stops blood reaching the liver - called cirrhosis. This means the liver cant filter the blood from dangerous substances and they will begin to build up and damage the rest of the body

It can also lead to increased blood pressure which can lead to circulatory and heart disease

Which cancers are linked to alcohol consumption and why?

Mouth, throat, bowels and liver because the toxic products damage DNA and cause cells to divide faster than normal

What are 4 withdrawal symptoms to giving up alcohol?

Depression, anxiety, nausea and hand tremors

What are the two main classes in illegal drugs?

Soft - cannabis

Hard - heroin and ecstasy

Hard drugs are more addictive/harmful than soft drugs

What are 2 health problems that illegal drugs can cause?

Heart problems and circulatory problems

Cannabis can increase risk of developing mental health problems

Explain what anabolic steroids are?

They are performance enhancing drugs that athletes take. However, they have negative impacts like high blood pressure

What is Auxin?

Plant hormone that controls growth at tips of shoot and root. Its produced at the tip and diffuses backwards to simulate the cell elongation process which occurs in the cell just behind the tips

How does Auxin work?

It promotes growth in the shoot but it actually inhibits growth in the root

What is Phototropism?

The growth response of a plant to light. Auxin helps in bending the plant towards the light source

What is Gravitropism?

The growth response of a plant to gravity. Auxin influences root growth downward and shoot growth upwards

What is positively phototropic?

A plant grows toawrds the light

What is positively gravitropic?

A plant grows towards gravity, into the soil

What happens when a shoot tip is exposed to light?

The shaded side of the shoot tip will accumulate more auxin. This makes the cell elongate faster on the shaded side, so the shoot bends towards the light

What happens when a root grows on its side?

The root will have more auxin on its lower side. This makes the cell elongate faster on the lower side, so the root bends downwards

What are the kidneys 3 main roles?

• Removal of urea and other waste products from blood

• Adjustment of salt levels in blood

• Adjustment of water content in blood

Describe the blood’s journey through the kidneys

The blood enters the kidney through the renal artery, which branch of the aorta. It is then carried in an arteriole to the capillary knot. Small molecules are filtered out of the capillary knot into the Bowman’s capsule. These molecules travel down the tubule whilst the filtered blood carries along a capillary network. Useful substances are reabsorbed back into the blood. The blood then exits the kidney through the renal vein and travels to the heart via the vena cava. Whatever isn’t reabsorbed forms urine and continues out of the nephron via the collecting duct. It then travels into the ureter and down to the bladder for storage. Urine is then excreted through the urethra

What is the capillary knot and how does it filter blood?

The capillary knot is a ball of capillaries. The arteriole that enters the capillary knot has a larger diameter than the arteriole that leaves it. This creates high pressure inside the capillary knot that forces small molecules like water, urea, salts and glucose to leave the capillary knot through a selectively permable membrane and enter the Bowman’s capsule

What is the medulla?

The innermost part of the kidney

What is the cortex?

Part of the kidney where the nephrons are positioned

What are nephrons?

The kidney’s filtraion units. There are around a million

What is excretion?

Removing the unwanted waste products that metabolic reactions produce from the body

What’s the pelvis in terms of the kidney?

Its the wide part of the kidney thats at the top of the ureter. It collects the urnine and funnels it into the rest of the ureter

Why are protiens and blood cells not filtered out of the blood in the capillary knot?

They are big molecules so they can fit through the SPM in the capillary knot and are not forced out

Which three useful substances are reabsorbed into the blood?

• Glucose - selectively reabsorbed as its moved back into the blood against the concentration gradient

• Sufficient salts are reabsorbed

• Sufficient water is reabsorbed - according to level of ADH

Which hormone controls the reabsorption of water in the kidneys and how does it do it?

Anti-diuretic hormone (ADH) controls the reabsopetion of water. The brain monitors the water content in the blood and instructs the pituitary gland to secrete ADH into the blood according to how much is needed. ADH makes the collecting ducts more permeable so more water is reabsorbed into the blood.

What happens to the urine when more water is reabsorbed?

Kidneys will produce a smaller volume of more concentrated urine

What are 2 ways we can use urine to indicate that someone has a disease?

• The pressence of blood cells and protiens in the urine could indicate kidney damage/disease because these molecues usually shouldn’t be able to pass through the kidney membrane

• A high concentration of glucose in urine could indicate someone has diabetes because the concentration of glucose can be so high in their blood that the kidney cant reabsorb all of it and so some of it stays in the nephron and enters the urine

How would you test urine for glucose and protien?

Test for glucose - Benidicts solution - coloured precipitation will form if glucose is present and the colour will indicate the concentration of glucose

Test for protiens - Biuret solutuion - solution will turn violet if protien is present

What machine is used to filter a persons blood whos kidneys stopped working?

Dialysis machine

How does a dialysis machine work?

Dialysis fluid will have the same concentration of salts and glucose as blood plasma so that these molecuse wont be removed from the blood. Blood will travel along a tube with a selectively permable barrier. The barrier is permable to things like salt and waste substances, but not big molecules like protiens. The barrier is surronded by dialysis fluid that flows in the oppsite direction of the blood (counter-current system). This means the concentration of urea in the blood will always be higher than in the dialysis fluid. This means the urea concentration gradient in diffusion is maintained and urea diffuses out of the blood and into the dialysis fluid at a constant rate

What are 3 disadvantages to Dialysis?

Time consuming - three times a week for 3-4 hours

Can cause blood clots and infection

Expensive for the NHS to run

Whats the main reason for dialysis?

To buy a patient with kidney failure valuable time until a donor organ is found

How can we try prevent rejection from a kidney transplant?

• Having a donour with a closely matched tissue type to the patient (e.g. relatives)

• The patient is treated with drugs that supress the immune system so that it wont attack the transplant (doenst always work)