biology - topic 5, homeostasis

sept-

conditions we need to control in order for the human body to function and why (3)

• correct glucose concentration in blood - too much can lead to problems like diabeties and damage to cells and tissues. Too little can lead to problems with energy

• correct body temp - to maintain optimum conditions for enzymes to work in. Too high and enzymes are denatured. Too low and rates of reaction are too slow for cells to survive

• correct water content - to maintain the correct concentrations of salts and sugars in our cells, tissues and organs

homeostasis define

the regulation of the internal conditions of a cell/organism to maintain optimum conditions

how our body responds to a stimulus

stimulus →receptor(sensory neorons will be found in sense organs)→coordinstion centre(motor neurons will allow muscles to move or substances to be released from glands →effector →responce

receptor (3)

define

examples

a group of cells that are sensitive to a stimulus

they take in info from the surroundings

e.g. light receptor cells in the eye are sensitive to light

coordination centre (2)

define

examples

an ORGAN that processes info from the receotirs and organises a responce for the effectors

e.g. the brain, the spinal cord, the pancreas

effector (3)

define

examples

responds to nervous impulses and causes a reaction

can be a muscle or a gland

e.g. leg muscles, pancreas

Nervous system

nerves

EWZDRXCTFGVBHNJMOGYTFURETS

• long fibres

• transmit electrical impulses from the brain and spinal cord (central nervous system (CNS)) to the rest of the body + back again

how are neurons adapted to send electrical impulses quickly

• how are long and thin so that they carry messages quicker

• they have many mitochondria so they have the energyto transmit electrical impulses

• they have branches to connect to other neurons

• they have a fatty surrounding the axon so that it is insulated

Nevous system

Effectors

effectors = muscles or glands which carry out a responce

• a gland responds by secreating chemical substances

• a muscle responds by contracting

how does your body respond to the information that you want to eat a cake in front of you

The receptor is in your eyes detect the stimuli. This is converted to an electrical impulse. This message is carried by the neurons To the brain, then the Effector (Salivary gland) Response to the nervous impulse and starts producing saliva when you eat the cake, the brain sends motor neurons to the effector making you reach for the cake

define synapse

Where two neurons meet there is a small gap called the synapse

what happens at a synapse

1. An electrical nerve impulse travels along the first axon

2. When the nerve impulse reaches the dendrites At the end of the axon chemical messengers called neurotransmitters are released

3. These chemicals diffuse across the synapse the chemicals bind with receptor molecules of the membrane to the second neuron

4. The receptor molecules on the second neuron can only bind to the specific neurotransmitters released from the first neuron

5. The binding of the neurotransmitter to the receptor stimulates the second neuron to transmit electrical impulse along its axon the signal therefore has been carried from one neuron to the next

define reflex actions

Rapid automatic response to a stimulus to protect the body from harm

reflex action flow diagram

Stimulus→ Receptor→(Sensory neuron) Relay neuron→(Motor neuron) effector → response

what is a reflex action

dangerous external stimuli is Detected by receptors

An electrical impulse is sent through the sensory neuron to the spinal cord

This trigger is a chemical called neurotransmitter to diffuse across the synapse

This causes the impulse to be carried through a relay neuron to the motor neuron

this causes a very rapid response by the effector E.G Muscle to contract

reaction time define

How long it takes to respond to a stimulus

factors affecting reaction time (5)

• age

• gender

• caffeine

• medication

• practice

REQUIRED PRACTICLE: REACTION TIME

equipment (4)

• 30cm ruler

• chair

• table

• partner

REQUIRED PRACTICAL: REACTION TIME

instructions (6)

1. use your week a hand for this experiment. Sit down on the chair with good upright posture and eyes looking across the room. Place your Full arm of your weaker arm across the table with your hand overhanging the edge of the table

2. Your partner will hold a ruler vert piece of the zero mark is level with the top of your thumb. They will tell you to prepare to catch the ruler.

3. Your partner will drop the ruler without telling you you must catch the real as quickly as you can when you sense the router is dropping

4. After catching the brewer look at the number level with the top of your thumb record this in the results table

5. Have a short rest and repeat up to 10 times

6. what places with your partner and repeat

REQUIRED PRACTICAL: REACTION TIME

IDC variables

I- the person

D- reaction time - how far the ruler is dropped

C- same hand

• same amount of time between goes

• placement of ruler - 0 cm between fingers

REQUIRED PRACTICAL: REACTION TIME

why aren’t you told wheb the ruler is foung to drip

so you aren’t aware and consciousit is happening - and reduced the bias

REQUIRED PRACTICAL: REACTION TIME

how could you improve the method

havw conversion chart in mm not cm (more precise scale)

test more students

drop from same height

more repeates

what is the pituitary gland

secrets several hormones into the blood in response to body conditions

what is the cerebral cortex

important in conscious thiught language memory and intelligence

what is the medulla

controls unconscious activities such as heartbeat, movements of the gut and breathing

ehat is the cerebellum

coordinates muscle activity and controls balance

what is the thermoregulatory centre

contains receptors sensitive to blood temp

br able to label parts of the brain

how can scientists study the brain

1. study people with brain damage

2. electrically stimulate different parts of the brain

3. scan the brain - CT scan, PET scan, MRI scan

ehats the difference between CT, PET, MRI scans

CT - uses Xrays

PET - uses radioactive chemicals

MRI - uses magnetic fields

ehy is treating the brain so difficult

1. wide range of things that can go wrong (timors, trauma, mental health, infection)

2. difficult to physically fix anything - invaded in a skull and surrounding brain tissue is fragile

3. the brain is so complex and we don’t fully understand it its difficult to fix wiyh drugs and chemicals

what is the function of the cornea

is the convex, transparent and allows light to enter the eye

what is the function of the lens

is transparent + bioxonvex, focuses light onto retina

what is the function of the pupil

a hole through which light passes to enter the eye

what is the function of the iris

contracts and relaxes to control the amount of like entering the eye

what is the function of the ciliary muscle

can change the shape of the lens to help focus light on the retina

what is the function of the retina

the lining of the vack of eye which contains light receptors

what is the function of the optic nerve

bundles of neurons which carry impulses from the eye to the brain

be able to label parts of the eye

lens reflex sheet

describe the antagonistic action (in bright + dim light)

• the antagonistic action of muscles in the iris control pupil diameter. there are radial and circular muscles in the iris. when jt contracts, the other relaxes

• in bright light, the pupil reflex decreases the diameter of the pupil. This decreases the amount of light that enters the eye. The circular muscles contract and the radial muscles relax

• in dim light, the pupil reflex increases the diameter of the pupil. This increases amount of light that enters the eye. The circular muscles relax and the radial muscles contacts

define accommodation

the process of changing the shape of the lens to focus on near or distant objects

what happens when you focus on a near object

and a distant object

near object - lens vefomes thicker, allowing the light rays to refract (bend) more strongly

Distant objects - lens is pulled thin, allowing the light rays to refract slightly

Define shortsightedness

why does this happen

and how it can be corrected

PICTURE

When someone can see near objects closely but is unable to focus on distant objects

This is because the lens focuses light in front of the retina instead of on it. Short sightedness xan be caused by the eyeball being elongated or the lens being too thick or curved. Shortsightedness can be corrected by putting a concave lens in front of the eye

Define longsightedness

why does this happen

and how it can be corrected

PICTURE

longsightedness = when someone can see distant objects clearly but is unable to focus on near objects

this is because the lens focuses light behind the retina instead of on it. Long sightedness can be caused by the eyeball being too short or the lens losing elasticity (often age related). longsightedness can be corrected by putting a convex lens in front of the eye

what is the hypothalamus

is the temperature - regulating centre of the brain. It contains receptors which are sensitive to the temperature of the blood flowing through the brain

negative feedback loop for body temperature

what does deamination do

prevents the buildup of excess AA

deamination process

1. the digestion of proteins (from diet) results in excess AA which need to be excreted safely

2. the liver removes the amino part of the AA by the process of deamination

3. they form ammonia (toxic) is immediately converted to urea in the liver cells, far less harmful

4. the urea enters the blood stream so it can be filtered out in the kidneys in urine

where are the

pituitary gland

thyroid gland

adrenal gland

pancreas

ovaries

testes (only male)

are in the body

what’s the main hormone produced in the

pituitary gland

thyroid gland

adrenal gland

pancreas

ovaries

testes

and what does each of them do

pituitary gland - thyroid gland - metabolism, growth and development of human body

thyroid gland - thyroxine - stimulates metabolic rate + protein synthesis

adrenal gland - adrenaline - prepares body for emergency

pancreas - insulin - allows glucose to enter cells

glycogen - regulate blood sugar

ovaries - oestrogen- bone strength, puberty, menstrual cycle

progesterone - prepares lining of uterus

testes - testosterone - signals body to make red blood cells + produces sperm

hormones

what are they

speed of message

where are they secreted from

means of travel

where do they travel to

chemical messengers

slow

long lasting

glands

in the blood

target organs/cells

adrenaline

where are the adrenal glands situated

what does it do

just above the kidneys, release a few hormones, including adrenaline

prepares the body for any emergency and increases heart rate, breathing rate and sending more oxygen and glucose to our cells

thyroxine

where is the thyroid gland situated

what does it produce

whats igs roles in the body

is the thyroid gland in control of its own secretions

situated in the neck

produce a few hormones including thyroxine

important roles jn the body:

-stimulates metabolic rate; this is the speed at which chemical reactions occur in the body

-also stimulates protein synthesis in cells - important for growth + development

thyroid gland is not in control of its own secretions - instead it requires an additional hormone to stimulate the gland to get it to perform iys function

TSH

what does the pituitary gland secrete

what does this stimulate

what happens thyroxine levels in the blood are too high

pituitary gland secretes a hormone called thyroid stimulating hormone (TSH)

this stimulates the thyroid gland to secrete thyroxine

when thyroxine levels in the blood are too high, less TSH and less thyroxine produced

thyroxine levels in the blood are reduced- known as negative feedback

negative feedback by thyroxine

what is negative feedback

-negative feedback mechanisms in homeostasis help to maintain conditions in the body wiyh an optimal narrow range

-any movement away from ideal conditions results in changes occurring which bring them back

regulation of metabolic rate involving thyroxine

1. yhere is a fall in the energy which is available to cells

2. receptors in the hypothalamus detect the fall in energy

3. the hypothesis causes the pituitary gland to release TSH into the blood

4. TSH binds to the thyroid gland and causes it to release thyroxine into the blood

5. the cells now have enough energy, which is detected by the hypothalamus

glucose

what is it

whats it made up of

whats 1 molecule of glucose have the formula of

the simplest form of sugars/carbohydrate

made up of carbon, hydrogen and oxygen atoms

1 molecule of glucose has the formula of C(6)H(12)O(6)

glycogen

what is it

why is it longer

where is it stored

glycogen is also a carbohydrate but is much longer than glucose becasue it is actually formed when lots of the excess glucose molecules joined together

can be stored inside cells

how do you feel when you have too much and too little glucose concentration in blood

too much - thirsty, dizzy

too little - faint, lethargic, tired

how insulin lowers blood glucose levels

1. blood glucose levels increase

2. pancreas detects high blood glucose

3. pancreas responds and releases insulin (travels in the bloodstream)

4. glucose is removed from the blood and stored as glycogen

5. blood glucose levels return to normal

• isn’t a quick process

how glucagon increases blood glucose levels

1. blood glucose levels decrease

2. pancreas detects low blood glucose

3. pancreas responds and secretes glucagon (into bloodstream)

4. glucagon is transported to the liver and muscle cells. glucagon causes the muscle cells to break down into glucose

5. both types of cells use glucose in respiration

6. liver cells release the glucose into the bloodstream

7. blood glucose levels return to normal

controlling blood glucose negative feedback loop

is it

glucagon

glucose

glycogen

insulin

diabetes

symptoms

frequent urination (esp at night)

weight loss

blurred vision

thirsty

more tired

cuts + wounds taking ages to heal

diabetes

what is diabetes

a condition that affects how your body uses glucose

because ppl with diabetes have higher levels of glucose in their bodies and they either don’t have enough insulin to move it, or their cells don’t work as they should wiyh the insulin they have

diabetes

treating diabetes

ppl with type 1 diabetes have regular check up to make sure they are healthy

regular insulin injections/insulin pump to help their bodies to use glucose effectively

take extra care of their health + eat a healthy diet

diabetes

insulin injections + pump

ppl with diabetes dont produce their own insulin they need to get from somewhere else to make sure their glucose levels are controlled

insulin pumps - fitted with a tube that is inserted under the skin. pump is battery operated abd releases insulin into the body throughout the day

insulin injections - use a syringe + needle (often called a pen) needles are small and inject the insulin under the skin where it is taken into the blood

diabetes

type 1 diabetes

• inherited NOT by your diet

• pancreas can’t create insulin because immune system attacks pancreas by mistake

• without insulin, your body isn’t able to move glucose from your blood + into your cells for you to use for energy

diabetes

type 2 diabetes

lifestyle related risk factors for developing type 2 diabetes are: obesity, poor diet, lack of excerise

body’s cells lose their sensitivity (no longer respond) to insulin being produced - makes it dofficult to control blood glucose levels - is preventable

ways water is removed from the body

skin → in sweat

lungs → water vapour leaves during process of exhalastion

kidneys → excess water leaves as part of urine

1. blood circulate the body under pressure and is brought to the kidneys in the renal artery (the amount of water and minerals ions yhat are reabsorbed varies - called selective re-absorption)

2. The kidneys filter the blood and then reabsorb all the useful material materials E.G.glucose

3. after it has been purified, the blood returns to the circulation through the renal vein

4. The kidneys make urine from the excess water, salt and urea

5. urea becomes toxic at high concentrations and must be removed from the blood

6. Urine travels away from the kidneys and tubes called uretes

7. Urine is stored in the bladder

8. When the bladder is full, urine has lost through the urea

• urea is produced from the breakdown of excess AA in the liver

how a kidney tubule filters out waste molecules

1. blood flows to the tubule

2. small molecules are filtered out of the blood, including:

-urea

-water

-glucose

-ions of salt

-bigger molecules (e.g.proetins) and blood cells are too large to be filtered out

3. useful molecules are re-absorbed back into the blood:

-all glucose

-some water

-some ions of salt (happens by diffusion + active transport)

4. the amounts kf water re absorbed is controlled by ADH, which is released by the pituitary gland

5. waste molecules from urine. This is stored in the bladder for excretion

filtration

• small molecules are squeezed out of the blood into the Bowman’s capsule

• the walls have small holes in them. Any molecules small enough to go through these holes will be squeezed through, into the bowman’s capsule (e.g water salt glucose and urea)

• most protein molecules are too big, so will stay in. blood along with the blood cells

role of ADH

is a hormone which is released by the pituitary gland and tracked through the blood to the kidneys

• when the blood is too concentrated → ADH acts on the kidney tubules causing more water to be reabsorbed baxk knto the blood

• this response lowers the concentration of blood and therefore less ADH is produced

• negative feedback

how is urea produced

ues is produced from the breakdown of excess AA in the liver

dialysis - how it works

1. unfiltered blood (high in urea) is taken from a blood vessel jn the arm, mixed with blood thinners/ anti-coagulant (prevents clotting) is pumped into the dialysis

2. inside the machine, blood + dialysis fluid are separated by a partially permeable membrane, the blood flows opposite direction to the dialysis fluid - allows exchange to occur between the 2 where a concentration gradient exists

3. the dialysis fluid has no urea in it - there is a large concentration gradient exists the- means the urea moves across the partially permeable membrane (from blood → dialysis fluid by diffusion) important as urea needs to be removed from the blood

4. dialysis fluid has a glucose concentration = to normal blood sugar levels - prevents the net movement of glucose across the membrane as no consentration gradient exists. important as patient needs glucose for respiration

5. as dialysis fluid contains an ion concentration similar to ideal blood plasma concentration, movement of ions across the membrane only occurs where there is an imbalance

• blood low in ions → diffuse from the dialysis fluid into the blood, restoring ideal blood levels

• blood high in ions → excess ions diffuse from blood to dialysis fluid

ehat does the dialysis fluid contains

• glucose concentration- similar to normal level jn blood

• concentration of ions - similar to normal blood plasma

• NO urea

the dialysis fluid needs to be sterile and at room temp - so that no pathogens entering the blood and the blood temp doesn’t change

urea and water pass from the blood into the dialysis fluid down their concentration gradient by diffusion and osmosis

glucose foesnt pass out of the blood into the dialysis fluid so there’s no concentration gradient between them

ions in the dialyss fluid are at normal blood consentration so only those ions that are at a higher concentration will diffuse into the dialysis fluid