B1.2 Responses to a changing envioronment Flashcards
What is the internal environment?
The conditions inside the body
What can happen if too much water is trapped within the body?
Swellings and high blood pressure
What is homeostasis?
The process of keeping the internal environment stable
What does the body lose water through?
- breath
- sweat
- urine
Where is sweat produced?
The sweat glands
What is osmoregulation?
The control of water in the body
What temperature does the body maintain?
37 degrees
What is thermoregulation?
The control of body temperature
What part of the brain monitors temperature?
The hypothalamus
What layer of the skin are nerve endings found at?
The dermis
How does the hypothalamus receive information about temperature?
- through the nerve endings in the dermis of the skin
- from the blood inside the body
How does the hypothalamus increase temperature when the body’s temperature goes below 37 degrees?
- cause muscles to shiver
- cause the erector muscles in the dermis to contract
- vasoconstriction
How does shivering increase the temperature of the body?
The respiration from shivering releases heat
What happens when the erector muscles contract?
The body hairs stand upright
How does contracting the erector muscles increase temperature?
When the body hairs stand up they can trap more air next to the skin to be used as insulation
What gland is oil released from?
The sebaceous gland
What do oils released from the sebaceous glands do?
Keep the skin well lubricated and in good condition
How does vasoconstriction increase temperature?
Less heat from the blood is lost to the air
How does the hypothalamus decrease the body’s temperature when it is over 37 degrees?
- vasodilation
- sweating
How does sweating decrease temperature?
When sweat evaporates it transfers heat energy from the skin to its surroundings
How does vasodilation decrease temperature?
It increases blood flow to the surface of the skin so that it’s easier for the blood to lose heat to air
What is the uppermost layer of skin called?
The epidermis
What is vasoconstriction?
The constriction of blood vessels
What is vasodilation?
The dilation of blood vessels
What do sense organs do?
Detect changes inside and outside of the body
What is a stimulus?
Something that causes a response
What cells detect stimuli?
Receptor cells
What are impulses?
Electrical signals that carry information
What is another name for a neurone?
A nerve cell
What do impulses travel along?
Neurones
What is the travelling of impulses along neurones called?
Neurotransmission
What is a dendron?
Extension of a neurone that carries impulses to the cell body
What are dendrites?
The fine extensions of a dendron that collect impulses from other neurones or receptors
What is an axon?
The long extension of a neurone that carries an impulse away from the cell body towards other neurones
What are nerves?
Bundles of neurones packed together
What does CNS stand for?
Central Nervous System
What organs make up the central nervous system?
The brain and the spinal cord
What does the CNS do?
Control the body
What is the thickest nerve in the body?
The sciatic nerve
How long is an adult spinal cord?
43-45cm
How wide is the sciatic nerve?
1.5cm in diameter
What does an effector do?
Carry out actions
What neurones receive impulses from receptor cells?
Sensory neurones
What neurones take impulses to effectors?
Motor neurones
What do relay neurones do?
Link sensory and motor neurones
Where are relay neurones found?
The spinal cord
What is the myelin sheath?
The fatty layer surrounding axons in neurones
What does the myelin sheath do?
- protect from surrounding tissue and other neurones
- helps the impulses be carried faster
What is a synapse?
The small gap between one neurone and another
What are neurotransmitters?
Chemicals that carry impulses across synapses
How do synapses make sure that an impulse is only sent in one direction?
They can only be released from axon endings
How big is the gap in a synapse?
0.00002cm wide
What are reflexes?
Actions that are automatic
What are the benefits of reflexes?
They are extremely quick so they protect the body
What is a reflex arc?
A neurone pathway in which a sensory neurone directly controls a motor neurone
What are coordinated responses?
Responses that require conscious thought
Why are reflexes faster than coordinated responses?
Reflex arcs bypass parts of the brain involved in conscious thought
What are some examples of human reflexes?
- the knee jerk reflex
- the pupils constricting in strong light
- blinking if something flies towards your face
What are hormones produced by?
Endocrine glands
What are hormones?
Chemical messengers
What happens when human growth hormone increases?
Muscles and bones start to grow at a faster rate
What is a target organ?
The organ on which a hormone has an effect
What happens to the concentration of blood glucose after a meal?
It increases
What does insulin do?
Makes cells take glucose out of the blood and turn them into glycogen
Where is insulin released from?
The pancreas
What does the body do when there is too much glucose in the blood?
Release insulin
What is glycogen?
The storage material of glucose
Where is ADH released from?
The pituitary gland
Where is adrenaline released from?
The adrenal glands
What does adrenaline do?
Speed up the heart rate
Where is glucagon produced?
The pancreas
What does glucagon do?
Cause cells to convert glycogen into glucose
What causes the development of female reproductive organs during puberty?
Oestrogen
What causes the development of male reproductive organs during puberty?
Testosterone
What produces testosterone in males?
The testes
What produces oestrogen in females?
The ovaries
What percentage of diabetics have Type 1 diabetes?
5-10%
What is diabetes?
A disease where the body cannot control blood glucose very well
What happens if blood glucose concentrations are too low?
Unconsciousness
What happens if blood glucose concentration levels are too high?
Tiredness and damage to the organs
What happens if blood glucose concentration is very high?
The kidneys get rid of glucose by putting it in urine
What causes Type 1 diabetes?
The pancreas doesn’t produce insulin
Where does insulin need to be injected?
The subcutaneous fat layer
What do people with Type 1 diabetes do to help with their disease?
- inject insulin everyday
- exercise
Why is insulin injected into the subcutaneous fat layer?
Fat absorbs insulin more easily
What happens to insulin levels when someone exercises?
They decrease
What causes type 2 diabetes?
The cells become resistant to insulin
What factors cause a risk of Type 2 diabetes?
- high-fat diets
- lack of exercise
- getting older
- being obese
How do people class obese people?
They find their BMI and if it is over 30 they are obese
What does BMI stand for?
Body mass index
How do you calculate BMI?
BMI = mass in kg/height in metres squared
How can you control Type 2 diabetes?
By changing the person’s diet and increasing the amount of exercise they do
What is a tropism?
A response to stimuli by growing towards or away from it
What is phototropism?
A tropism caused by light
What is a negative tropism?
When something grows away from a stimulus
What tropism do plant roots have?
Negative phototropism
What tropism do plant shoots have?
Positive phototropism
Why are shoots positively phototropic?
To get enough light for photosynthesis
What are plant growth substances?
Plant hormones
What hormone causes positive phototropism in plant shoots?
Auxin
Where are auxins produced?
The tip of shoots and roots
What does auxin in plant shoots do?
Cause the elongation of cells
Where do auxins go when light is put on a shoot?
The shaded side
How do auxins cause shoots to grow towards the light?
They elongate cells on the shades side so that the shoot curves towards the light
What is geotropism?
Growth towards gravity
What is another name for geotropism?
Positive gravitotropism
What does auxin in plant root tips do?
Cause cells to stop elongating
What causes geotropism in plant roots?
Auxin
How does the geotropism of plant roots help the plant?
- anchors the plant in place
- helps it reach moisture underground
What happens when a seed germinates?
Roots and a shoot start to grow
What does gibberellin do?
Cause starch stored in a seed to convert into sugars
Why is gibberellin produced?
- so that a seed has enough energy to germinate
- to stimulate flower and fruit production in some species
When is gibberellin produced?
At the beginning of germination
What conditions do some seeds need before they germinate?
Periods of darkness and cold
What is selective weedkiller made from?
Artificial auxin
What does selective weedkiller kill?
Plants with broad leaves like daisies and dandelions
How does selective weedkiller work?
It causes weeds with broad leaves to grow out of control and die while leaving crops with narrow leaves unaffected
What is artificial auxin used for?
- selective weedkiller
- rooting powders
What are rooting powders used for?
It makes cuttings develop roots more quickly
What are the benefits of using cuttings to produce plants?
Large numbers of the same plant can be produced in comparison to growing them with seeds
Where are plant hormones sprayed to produce seedless fruit?
The flowers
What hormones are fruits sprayed with to make them bigger?
Gibberellins
What controls the ripening of fruit in a plant?
Hormones
What happens when hormones are sprayed on fruit trees?
- it stops the fruit from falling off
- it speeds up the ripening process
Why are plant hormones sprayed on fruit trees to stop fruit falling off?
- so that they don’t fall and get damaged
- so that they grow bigger
Why are plant hormones sprayed on fruit trees to speed up ripening?
So that all the fruit ripens together and they can all be picked in one go
Why are plant hormones sprayed on unripe fruit?
To make them ripe
