Co-ordination and response Flashcards
What is homeostasis
Maintaining a constant internal environment
What is a hormone
Chemical messengers that are secreted by glands and carried in the bloodstream
How is a change in core body temperature detected
By the thermoregulatory centre in the hypothalamus
Why is it important that core body temp remains constant
For enzymes at work at their optimum temp and not denature
How does the body respond to an increase in temp
sweating- sweat glands produce sweat which cools the body upon evaporation
Hair lies flat- increases heat loss
Vasodilation- arterioles become wider, blood flow closer to the skin and increases heat loss from radiation
How does the body decrease blood sugar levels
Brain sends signal to pancreas
Pancreas releases insulin into bloodstream
Glucose is stored as glucagon in the liver from the bloodstream
How does the body respond to a decrease in temp
Shivering- muscular contractions require respiration which releases heat
Hair stands on end- insulation, traps air
Vasoconstriction- arterioles become narrower, blood flow further from skin and reduces heat loss from radiation
How does the body increase blood sugar levels
Brain send signal to pancreas
Pancreas releases glucagon into bloodstream
Glucagon splits up into individual glucose molecules again from liver into bloodstream
Identify glands and the hormones they release
Adrenal glands- adrenaline
Testes- testosterone
Pituitary glands- ADH
Pancreas- insulin
Ovaries- oestrogen
what 2 structures make up the central nervous system
Brain
Spinal cord
What is a stimulus
A change in the environment
What is a receptor
A special type of cell that detects changes in the environment
what is an effector
produce a specific response to a detected stimulus
muscle or glands
what makes reflex actions involuntary and faster responses
they bypass the brain to minimise damage to body and be quicker
why are fast reflex actions important
essential for survival and avoiding damage
why is the iris reflex important
prevents the bright light from damaging the receptor cells in the retina
Iris reflex in bright light
circular muscles contract
radial muscles relax
pupil constricts
less light can enter eye
iris reflex in dim light
radial muscles contract
circular muscles relax
pupil dilates
more light can enter eye
how do electrical impulses move from one neurone to another
nervous impulses arrive at end of neurone causing vesicles to move towards membrane
neurotransmitters (chemicals) released from vesicles and diffuses from one side of synapse to the other
neurotransmitters attaches to receptor causing new electrical impulses to move down the neurone
what is accomodation
ability to focus on objects which are at different distances from the eye
what happens when you focus on a near object
ciliary muscles contract
suspensory ligaments loosen
lens shape thickens
what happens when you focus on a far object
ciliary muscles relax
suspensory ligaments tighten
lens shape thins
what is a tropism
a growth in response to a stimulus
what effect does auxin have in the roots and shoots of plants
roots- inhibits growth
shoots- stimulates growth
how do the roots respond to gravity
auxin gathers in bottom side due to gravity
as auxin inhibits cell elongation in roots, this causes the roots to grow downwards
how do the shoots respond to gravity
auxin gathers in bottom side due to gravity
auxin stimulates cell elongation in shoots, causing the shoots to grow upwards
how does a plant shoot respond to light
shoot grows towards light
auxin builds up on shaded side, so cell elongates faster on this side
this causes shoot to bend so they can absorb more light for photosynthesis
