Homeostasis - B5

Def: Homeostasis

regulation of internal environment between set limits

3 Egs of what control systems control

body temp, blood glucose, water levels

Def: negative feedback

response of the body if levels gets too high or low to return it to normal

What is the process of a response coordinated by the CNS?

stimuli → receptor → coordination centre → effector → response

Def: stimuli

a factor that causes a response from the body

Eg: stimuli

bee sting

Def: Receptor

detects a stimulus

Eg: Receptor

skin

Def: Coordination Centre

receives and processes information then organises a response

Eg: Coordination Centre

Brain

Def: Effector

produces a response

Eg: Effector

muscle

Def: Response

act of restoring optimum level

Eg: Response

sweating lowers temperature

Def: Nervous system

allows humans to react to their surroundings and coordinate their behaviour

What is the the Nervous system made up of

CNS, sensory neurones, motor neurones, effectors

Def: CNS

Central Nervous System - brain and spinal cord

Def: sensory neurone

carry information via electrical impulses from receptors to CNS

Def: motor neurone

carry information via electrical impulses from CNS to effectorsa

Def: Reflex action

automatic and rapid response to a stimuli

What is the process of a reflex arc?

stimuli → stimulus → sensory neurone → relay neurone → motor neurone → effector response

What is the difference between a reaction coordinated by CNS and a reflex action?

doesn’t involve conscious part of the brain

Why do reflex arcs not involve conscious part of the brain?

to prevent injury by acting rapidly

What is the required practical on reaction times?

how long it takes to react to the dropping of a ruler (with and without caffeine)

What does the cerebral cortex do?

responsible for consciousness, intelligence, memory and language

What does the medulla do?

unconscious activities

What does the cerebellum do?

muscle coordination

What are the methods for studying the brain?

* studying patients with brain damage
* electrically stimulating the brain
* MRI scans

What does the iris do when exposed to light?

circular muscles contract, radial muscles relax → pupil shrinks → reduces amount of light enter the eye

What does the iris do in dim light?

circular muscles relax, radial muscles contract → pupil widens → reduces amount of light enter the eye

Def: accommodation

the changing shape of the lens to focus on an object

How does the lens change in shape to see short distance?

ciliary muscles contract, suspensory ligaments slacken → lens becomes thicker and more curved → light refracted more

How does the lens change in shape to see long distance?

ciliary muscles relax, suspensory ligaments contract → lens thins and flattens → light refracted less

Def: myopia

short sightedness - light focuses in front of the retina

Def: hyperopia

long sightedness - light focuses ‘behind’ retina

What type of lens would a myopia suffer’s glasses have?

concave

What type of lens would a hyperopia suffer’s glasses have?

convex

What are the treatments for vision defects?

* glasses
* contact lenses
* laser eye surgery
* replacement lens surgery

What is optimum human body temp?

37°C

What is the coordination centre for temperature control?

thermoregulatory centre

What does the body do to cool down?

* sweat
* vasodilation

Why does sweating cool you down?

transfers energy to the environment

Why does vasodilation cool you down?

blood flow is closer to the skin and helps transfer energy to the environment

What does the body do to warm up?

* hairs stand up
* vasoconstriction
* shiver

Why does hairs standing up help warm you up?

creates an insulating layer

Why does vasoconstriction help warm you up?

closes of skin’s blood supply so energy doesn’t transfer away from the body

Why does shivering help warm you up?

muscles contract → cells respire → transfers energy

Def: endocrine system

system of glands that release hormones

Def: hormone

chemical messenger sent in the blood

What does the pituitary gland do?

releases many hormones that regulate body conditions including other glands

What does the thyroid produce?

thyroxine

What does thyroxine do?

regulates metabolic rate, heart rate, temp

What does the adrenal gland release?

adrenaline

What does the adrenaline do?

prepares body for ‘fight or flight’:

* increases heart rate
* increases breathing rate

What does the pancreas release?

insulin and glucagon

What does insulin do?

removes glucose from the blood

What does glucagon do?

releases glucose from glycogen stores into the blood

Def: glycogen

glucose stores

Where is glycogen produced and stored?

liver

What causes Type 1 diabetes?

pancreas produces little to no insulin

How is Type 1 diabetes treated?

* insulin therapy
* regular exercise
* limited intake of simple carbohydrates

What causes Type 2 diabetes?

when the body becomes resistant to insulin

How is Type 2 diabetes treated?

* regular exercise
* carbohydrate-controlled diet

What process do kidneys carry out?

filtration

What substances are removed from the bloodstream by filtration?

* urea
* ions
* water

\

What is urea made of?

ammonia

Why is ammonia removed from the bloodstream?

it is toxic

What is ammonia the product of?

deamination

Def: deamination

the conversion of excess amino acids into carbohydrates and fats

Eg: an ion found in the filtration process

ion

Why are ions removed from the bloodstream?

excess ions could unbalance water content of the body

What is the consequence of the wrong water content in the body?

wrong amount of water absorbed by osmosis → cell damage, inefficient cells,

Def: ADH

anti-diuretic hormone

What does ADH do?

controls concentration of urine

What are the treatments for kidney failure?

* dialysis
* kidney transplant

Def: dialysis

when the blood is filtered externally by a machine between partially permeable membrane

How long does dialysis take?

3-4 hours

How often do patients receive dialysis?

3 times per week

What is the main risk with kidney transplant?

patient’s body rejects the new kidney

What 4 hormones control the menstrual cycle?

* oestrogen
* FSH
* LH
* progesterone

Where is oestrogen produced?

ovaries

What does oestrogen do?

* causes uterus lining to grow
* stimulates production of LH
* inhibits release of FSH

Where is progesterone produced?

ovaries

What does progesterone do?

* maintains uterus lining
* inhibits release of LH and FSH

Def: LH

Luteinising Hormone

Where is LH found?

the pituitary gland

What does LH do?

stimulates release of the egg

Def: FSH

Follicle Stimulating Hormone

Where is FSH produced?

pituitary gland

What does FSH do?

* causes egg to mature
* stimulates oestrogen production

How can oestrogen be used as a contraceptive?

taking it every day keeps levels permanently high and inhibits production of FSH

How can progesterone be used as a contraceptive?

maintained high levels produces thick mucus that prevents sperm reaching the egg

What is ‘the pill’?

an oral contraceptive pill containing oestrogen and progesterone

What are other hormonal contraceptive methods?

* patches
* implant
* injection
* IUD

What are barrier methods of contraception?

* condoms
* diaphragm
* spermicide

How can FSH and LH be a fertility treatment?

can make up for naturally lower levels of each hormone in the body and stimulate ovulation

What are the possible risks of hormonal fertility treatment?

* doesn’t always work
* expensive
* can stimulate too many eggs and result in multiple pregnancies

Def: IVF

in vitro fertilisation - fertilisation of an egg externally before implanting the embryo into the uterus

What are the cons of IVF?

* expensive
* emotionally taxing
* low success rate
* possible reaction to hormones
* risk of multiple births

Why are some people against IVF?

* unused embryos are destroyed
* unused embryos can be used in genetic testing
* potential for gene editing