b3 - organism level systems

what does the centeral nervous system consist of

brain and spinal cord

what are the central nervous systems main functions

• take in sensory information,

• process information

• send out orders to the rest of the body

what does the peripheral nervous system consist of

nuerones, receptors and effectors

what is the peripheral nerous systems main functions

• collecting information

• sending it to the cns

• acting on instructions from the cns

whats a nuerone

nerve cells which are adpated to carry electrical impulses from one place to another

whats a stimulus

a change in the enviroment we react to

whats a receptor

detects a stimulus and sends an electrical impulse to the cns through sensory neurones

whats a sensory nuerone

Sensory neurones carry electrical signals - nerve impulses - towards the central nervous system (spinal cord and brain).

whats a motor nuerone

carry nerve impulses away from the central nervous system to the effectors.

what are effectors

a muscle/ gland which acts in response to a stimulus

whats the order of a reflex arc

stimulus →receptor → sensory nuerone → cns → motor nuerone → effector → response

where are electrical pulses passed along a nuerone

the axon

why do nuerones have branched endings and what are they called

called dendrites and they mean they can connect with lots of other nuerones

whats a myelin

a fatty sheath surrounding some axons in a neuron which acts as an electrical insulator speeding up the electrical impulse

why is a long nuerone better than short ones joined together

connecting with another nuerone slows the impulses down

what is the gap between two nuerones called

synapse

how are electrical impulses sent between nuerones

1. an electrical impulse travels along the first **axon**
2. this triggers the nerve-ending of a neurone to release chemical messengers
3. these chemicals **diffuse** across the synapse (the gap) and bind with receptor molecules on the **membrane** of the second neurone
4. the receptor molecules on the second neurone bind only to the specific neurotransmitters released from the first neurone
5. this stimulates the second neurone to set off another electrical impulse.

what are reflex actions

automatic actions to stop you from injuring yourself

how do reflex actions work

1. The **receptor** in the skin detects a stimulus - the change in temperature.
2. The **sensory neurone** sends nerve impulses to the spinal cord.
3. The **relay neurone**, which is located in the spinal cord, carries the nerve impulses from sensory neurones to **motor neurones**.
4. The **motor neurone** sends nerve impulses to the **effector**.
5. The **effector** - the biceps muscle in the arm - contracts so that the hand is moved away.

whats homeostatis

maintaining constant internal body conditions

Where is adrenaline released from ? where is it located in the body ?

adrenal gland, just above the pancreas

What does adrenaline do ? how does it do it ?prepares body for fight or flight response

• prepares body for fight or flight response

• does this by binding to receptors in the heart causing it to contract more and with more force - increasing heart rate an blood pressure and blood flow to muscles

• hormones also bind to receptors in the liver to make it produce glucose

When your brain detects a stressful situation what does it do ?

sends nerve impulses to adrenal glands, respond by secreting adrenaline

how does thyroxine regulate the metabolism with negative feedback

• thyroxine released by thyroid gland

• thyroxine is released in respond to thyroid stimulating hormone (TSH) released from pituatry gland

• negtaive feedback system keeps the amount of thyroxine levels in the blood right

what does the bodyy do when levels of thyroxine are higher than normal in the bloodstream

• the secretion of THS from the pirtuatry gland is inhibited

• reduces amount of thyroxine released from the thyroid gland so the levels in blood fall back to nomal

What is a gland ?

An organ that makes one or more substances, such as hormones, digestive juices, sweat, tears, saliva, or milk

What are hormones ?

Chemicals produced in various glands called endocrine glands and released directly into the blood to the target cells which have the right receptors to respond to that hormone

what does the pituitary gland do in the endocrine system

is the master gland and tells other glands to secrete their hormone in the pituitary system

what does the adrenal gland do in the endocrine system

fight or flight response

what does the pancreas do in the endocrine system

regulates blood glucose

what do the testes do in the endorcine system

only found in males , secrete testosterone

what do the ovaries do in the endorcine system

in females, secrete oestrogen

whats negative feedback

When your body **detects** that the level of a substance has **gone above or below the normal leve**l, it triggers a **response** to bring the **level back to normal** again. e.g. thyroid regulating the metabolic rate

Name the two hormones secreted by the ovaries

oestrogen, progesterone

name the three hormones secreted by the pituitary gland

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FSH, LH, TSH

what is FSH and LH

• FSH(follicle stimulating hormone) and LH (luetinising hormone) are released from the pituitary gland and help support the menstrual cycle

What does FSH do ?

Causes egg to mature

stimulates ovaries to produce oestrogen

what is oestrogen

main female sex hormone produces in the ovaries which is involved in mesntrual cycle and devloping femal charcteritics (e.g. breasts)

what does oestrogen do ?

causes lining of uterus to thicken

stimulates production of LH

inhibits production of FSH so that only one egg is released in each cycle

What does LH do ?

stimulates release of egg (ovulation)

indirectly stimulates progesterone production

what is progesterone

hormone produced in the ovaries to help support ovaries and also is involved in the menstrual cycle

what does progesterone do ?

maintains uterus lining. when level falls and there's low oestrogen -lining breaks down

inhibits production of FSH and LH

low levels allow FSH to increase- whole cycle starts again

Name the 4 stages of the menstrual cycle

1\. menstruation starts- uterus lining breaks down and is released

2\. lining of uterus builds up again 4-14 thick spongy layer full of blood vessels ready to receive a fertilsed egg.

3\. egg develops and is released from ovary (ovulation)

4\. lining is maintained- if no fertilised egg then lining sheds and cycle starts again.

what does testosterone do

stimulate sperm production from the testes

why would low levels of FSH cause infertility ?

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some women have low levels of FSH so there eggs can't mature- no ovulation takes place- cant get pregnant

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how can ovulation be stimulated ?

by injection of FSH and LH

explain how ivf works

IVF involves giving a mother FSH and LH - stimulate the maturation of several eggs.

The eggs collected from mother and fertilised by sperm from father in a dish in a lab

The fertilised eggs develop into embryos.

At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother's uterus (womb).

what are contraceptives used for ?

to prevent pregnanacy

name the types of hormonal contraception that use progesterone and how long they are effective for

injection -up to 3 months

implant- inserted beneath skin if the arm for 3 years

the coil (ius) - t shaped piece of plastic inserted into uterus 3-5 years

mini pill( progesterone only pill) has to be taken every day

how do contraceptive methods involving progesterone work

* stimulates production of **thick cervical mucus** making it less likey for the sperm to get through
* **thins lining of uterus** to make it less likely for egg to implant
* prevents ovulation by **inhibiting production of lh and fsh**

name the methods of hormonal contraception using progesterone and oestrogen

combined pill - taken in a 21 day pill, 7 days no pill cycle

patch- worn in skin in 4 week cycle

how does oestrogen prevent pregnancy ?

prevents ovulation by inhibiting FSH

what is a barrier method is contraception?

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stop the egg and sperm meeting

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Name the barrier methods of contraception

condoms, female condoms and diaphragm

what are the no hormonal methods of contraception

* intrauterine devices-IUDS
* natural planning
* sterilisation

how does an iud work

its non hormonal t shaped device made from copper inserted into the uterus and it works by stopping the sperm and egg from surviving in the womb or fallopian tubes.

whats natural planning

not having sex when the womans most fertile

whats sterilisation

surgical procedure to cut/tie tubes in reproductive system

what are bad things about hormonal methods of contraception

* side effects
* possibility of doing/taking it wrong so is ineffective
* dont protect against sti’s

name advantages of hormonal methods of contraception

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long lasting methods- don't have to worry about it every day

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what is diabetes ?

Diabetes is a disease in which the body is unable to produce any or enough insulin causing elevated levels of glucose in the blood.

whats type 1 diabetes

the pancreas produces little or no insulin

how do you treat type 1 diabetes

through insulin therapy - injecting insulin several times a day (often at mealtimes)

stops level of glucose in blood from getting too high- very effective

what is type 2 diabetes ?

* the body cells lose their sensitivity ( no longer respond to insulin being produced)
* makes it difficult to control blood glucose levels

how is type 2 diabetes treated

healthy diet, exercising regularly ( increases amount of energy used up by body and decreases amount of stored body fat) and losing weight if necessary

what can increase the chance of getting type 2 diabetes ?

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* being overweight
* too much saturated fat which increases blood cholesterol

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whats does insulin do and wheres it made

lowers blood glucose levels and made in pancreas

what does glucagon do and wheres it made

increases blood sugar levels and made in pancreas

whats glucose and wheres it made

a sugar used to make energy and is made in the liver

whats glycogen

Glycogen is a carb stored in liver and muscles. It's a quick energy source made up of glucose molecules.

what happens of your blood glucose levels are too high

* pancreas is stimulated
* **insulin** is secreted
* insulin stimulates glucose uptake from blood
* blood glucose level falls

what happens of out blood glucose levels are too low

* pancreas is stimulated
* glucagon is secreted
* glucagon stimulates liver to release glucose
* blood glucose level rises