B5 - Homeostasis

ruler drop test method

1. work with a partner.

2. person A holds out hand with gap between thumb and 1st finger

3. person B holds ruler with the 0 at top of person A’s thumb

4. person B drops ruler without telling person A and they must catch it

5. The number level with the top of person A’s thumb is recorded in a suitable table. Repeat 10 times.

6. Swap places and record the other 10 attempts

7. Use the conversion table to help convert your ruler measurements into reaction time or just record the catch distance in cm.

in the ruler drop test, what effect does noise have in the reaction time?

increases reaction time

the brain is made of

billions of interconnected neurones

the brain controls

complex behaviour

the 4 main areas of the brain are

the cerebrum, the cerebellum, the medulla and the hypothalamus

the cerebrum function

controls intelligence, personality, conscious thought and high-level functions eg. language and verbal memory

the cerebrum description

split into 2 hemispheres and highly folded

what is the outer layer of the cerebrum called

cerebral cortex

the cerebellum function

controls balance, coordination of movement and muscular activity

the medulla function

controls unconscious activities such as heart rate and breathing rate

the hypothalamus function

regulating centre for temperature and water balance within the body

How have neuroscientists been able to map regions of the brain to their particular functions?

Studying patients with brain damage , electrically stimulating different parts of brain and using MRI scanning techniques

Who and when has an accident whilst laying railway tracks and what happened to him?

Phineas Gage in 1848 had an iron rod go through his skull

What happened after the skull accident in the 19th century

He survived but he lost his inhibitions socially and emotionally due to the rod passing through particular parts of his brain

Non-invasive brain procedures include

EEGs and MRIs

What does MRI stand for

Magnetic resonance imaging

What does EEG stand for

Electroencephalogram

How does an EEG work

Different parts of brain stimulated with a weak electrical current. If motor area is stimulated, patient makes involuntary movement. If visual area stimulated, patient can see flash of colour. Results can be traced and studied to observe electrical activity in brain using an EEG reading.

How do MRIs work

Use strong magnetic fields and radio waves to show details of brain structure and function. Patient is asked to do various tasks and by looking at scans it is visible which parts of brain are active during each task.

Risks of brain surgery

Due to complexity and delicacy of brain, more damage or side-effects could be created, which could affect patient’s quality of life.

Possible reasons for brain surgery

Removing tumour or excess fluid eg. Blood

Eye definition

A sense organ containing receptors sensitive to light intensity and colour

Cornea function

Refracts light - bends it as it enters the eye

Iris definition

Controls how much light enters pupil

Lens function

Further refracts light to focus it onto retina

Retina function

Contains the light receptors

Optic Nerve function

Carries impulses between eye and brain

Sclera function

Tough white outer layer of eye. Helps protect eye from injury

how does vision work?

rays of light are bent so the brain can make sense of them and they hit the retina. this sends impulses to the brain. the light is focused by the lens.

main types of light receptors

rods and cones

which type of light receptor is more sensitive to light

rods, so they’re useful for seeing in dim light/in the dark

the amount of light entering the eye is controlled by a ____ ____

reflex action

when the eye is in dim light, the pupil _____ to …

dilates to take in more light

what controls the changing of the pupil’s shape

the muscles of the iris

eyes in dim light diagram

eyes in bright light diagram

accommodation definition

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

to focus on a near object

lens becomes thicker to allow light rays to refract (bend) more strongly. for this, the suspensory ligaments loosen, so there is low muscle tension.

to focus on a distant object

lens is pulled thinner to allow light rays to refract (bend) only slightly. for this, the suspensory ligaments stretch, so there is high muscle tension.

parts of the eye diagram (10)

2 most common defects of the eye

• myopia (short-sightedness)

• hyperopia (long-sightedness)

what causes the 2 most common eye defects

the rays on light do not focus on the retina so a clear image is not formed

potential causes of myopia

• elongated eyeball, so distance between lens and retina is too great

• lens being too thick and curved, so rays are refracted too much

in all cases, light is focused in front of the retina rather than on it

potential causes of hyperopia

• eyeball is too short, so distance between lens and retina is too small

• loss of elasticity in the lens, so light is not refracted enough (often age-related)

in all cases, light focuses behind the retina rather than on it

fix to myopia

placing a concave lens in front of the eye as shown

fix to hyperopia

placing a convex lens in front of eye as shown

how do contact lenses work

work by being ‘in contact’, float on surface of cornea, work like spectacle lenses by fo

how does laser surgery work

reshapes cornea surgically. common for myopia but can be used for some hyperopia conditions

how do replacement lenses work

implanting artificial lenses to be placed in front of original lens of eye through a small cut in the cornea. this is a recent development.

hormone definition

chemical substance produced by a gland which alters the activity of specific target organs

what happens to a hormone after it has been used

it is destroyed in the liver

what are the effects of the endocrine system in comparison to nervous system

the effects of hormones are much slower than nervous system but they last much longer

what type of signal does the nervous system send

electrical (chemical at synapses)

what type of signal does the endocrine system send

chemical

how are the signals transmitted in the nervous system?

by nerve cells (neurones)

how are the signals transmitted in the endocrine system?

by the bloodstream

what are the effectors of the nervous system?

muscles or glands

what are the effectors of the endocrine system?

target cells in particular tissues

what type of response is received as an effect of the nervous system?

muscle contraction or secretion

what type of response is received as an effect of the endocrine system?

chemical change

what is the speed of the response for the nervous system?

very rapid

what is the speed of the response for the endocrine system?

slower

what is the duration of the response for the nervous system?

short (until nerve impulses stop)

what is the duration of the response for the endocrine system?

long (until hormone is broken down)

what gland is known as the master gland

the pituitary gland

what is the function of the pituitary gland?

to secrete several hormones into the blood in response to body’s condition, such as blood water levels. it can also act on other glands to stimulate release of different types of hormones

where is the pituitary gland

in the brain

where is insulin produced

pancreas

where is thyroxine produced

thyroid gland

where is testosterone produced

testes

where is oestrogen produced

ovaries

why is the role of adrenaline

preparation for ‘fight or flight’, meaning body can perform a quick action where it is essential

where is adrenaline produced

adrenal glands

what are the target organs for adrenaline

several targets including respiratory and circulatory systems

what are the target organs for insulin

liver

what does ADH stand for

anti-diuretic hormone

where is ADH produced

pituitary gland

what is the target organ for ADH

kidneys

what is the role of ADH

controlling water content of blood

effects of ADH

increases reabsorption of water by the collecting ducts

effects of adrenaline

increases breathing rate, heart rate, flow of blood to muscles (therefore diverting blood away from areas such as digestive system), conversion of glycogen to glucose

role of insulin

controlling blood glucose levels

effects of insulin

increases conversion of glucose into glycogen for storage

negative feedback control system

responds when conditions change from optimum point and returns conditions to normal. continuous cycle of events

negative feedback control system diagram

what is the role of thyroxine

stimulates the basal metabolic rate by controlling the speed at which oxygen and food products react to release energy for the body to use

what do low thyroxine levels stimulate

stimulate hypothalamus to release TRH, causing pituitary gland to release TSH so thyroid releases more thyroxine and blood levels return to normal

what do normal thyroxine levels stimulate

prevent/inhibit TRH release from hypothalamus and this inhibits TSH release from pituitary, so normal blood levels are maintained

are thyroxine levels controlled by negative feedback?

yes

are adrenaline levels controlled by negative feedback?

no

when is adrenaline released

in times of fear or stress

what does TSH stand for

thyroxine stimulating hormone

if the blood glucose concentration is too high…

pancreas produces insulin that causes glucose to move from the blood into cells. in liver/muscle cells, excess glucose is converted into glycogen for storage

effects of low glucose on pancreas

insulin not secreted into blood

effects of low glucose on liver

does not convert glucose into glycogen

effects of low glucose on blood glucose level

increases

effects of high glucose on pancreas

insulin secreted into blood

effects of high glucose on liver

converts glucose into glycogen

effects of high glucose on blood glucose level

decreases