Homeostasis and Response Flashcards
What is the definition of homeostasis?
The maintenance of the internal conditions in the body in response to internal or external changes
What are the three main components of the control system?
Receptor: Cells that detect stimuli, or changes in the environment. E.g. touching a needle
Coordination centres: Areas that process the information sent from the receptors and send out signals to respond to this. E.g. Brain, spinal cord
Effector: Muscles or glands that act to restore conditions to optimum. E.g. Biceps contracting to pull hand away from needle.
What are the three types of neurones?
Sensory neurones, Relay neurones and motor neurones
Why does the body need to be regulated
The body needs to be regulated in order for the enzymes to function optimally
What is the negative feedback for when a level is too low or too high
The receptor detects a stimuli that the level is too low or too high
The coordination centre receives the information and processes it to find a solution
The effectors counteract this and bring the level back up or down to optimal level
What is a synapse
a synapse is the gap between two neurones. A chemical is diffused across the gap and then the electrical signal continues
What are reflexes
reflexes are rapid, involuntary responses that aim to reduce harm to us. They do not go through a conscious part of the brain.
What is a reflex arc
A reflex arc is the passage of information from the receptor to the effector
What is the path of the reflex from the receptor to the effector
The stimulus is detected by the receptor, and the electrical signal is sent via the sensory neurones to a relay neurone in the CNS. The relay neurones then pass it along to the motor neurones who carry the signal to the effector which acts accordingly.
What is myopia
Short-sightedness - unable to focus on distant objects
What is hyperopia
Long-sightedness - unable to focus on near objects
What causes myopia
The lens is the wrong shape and refracts the light too much so it is formed in front of the retina, or the eyeball is too long
What causes hyperopia
The lens is the wrong shape and doesn’t refract the light enough, so the image forms after the retina, or the eyeball is too short.
What is the sclera
The tough supporting wall of the eye
What is the cornea
The transparent outer layer of the eye that refracts the light
What is the iris
The iris is the coloured section that contains muscles that change shape of the pupil to determine how much light enters the eye
What is the lens
The lens focuses the light onto the retina where tie image forms
What are the suspensory ligaments and ciliary muscles
These are muscles that control the shape of the lens for accomodation
What is the optic nerve
The optic nerve carries impulses from the receptors on the retina to the brain
How does the pupil adjust for bright or dim light
The Circular muscles Contract to allow less light in, and the Radial muscles Relax to allow less light in.
The opposite happens in dim light
What is accommodation
The adjusting of the lens for near or far objects
How does the eye accommodate for a near object
The Ciliary muscles Contract, and the Suspensory ligaments Slacken which makes the lens flat and refract light greater
How does the eye accommodate for a far object
The ciliary muscles relax and the Suspensory ligaments tighten, making the lens thin and refract light lesser
What are some treatments for long or short-sightedness
Contact lenses compensate for the refraction
Laser eye surgery can change the shape of the eye
The lens in the eye can be replaced with surgery
What is the name given to the centre in the body that controls temperature
Thermoregulatory centre
Why does the body have to keep the temperature at a constant
To allow enzymes to function optimally
What does the body do when you are too hot
Sweat is produced which transfers heat to the environment
Hairs lie flat to reduce insulation
Vasodilation - the blood vessels dilate so more heat energy can be lost from the skin
What does the body do when you are too cold
Shiver - the respiration used to shiver transfers heat to the body
Hairs stand on end to create an insulating layer of air
No sweat
Vasoconstriction - the blood vessels constrict to preserve heat
what is the hormone that controls blood glucose levels
insulin
What is the hormone which prepares the body for ‘fight or flight’
adrenaline
What happens when blood glucose levels are too high
Insulin is released, which causes glucose to be taken in by cells, and for some glucose to be converted to glycogen and stored in the liver
What is glycogen
A storage form of glucose which is stored in the liver and muscles
What happens when blood glucose levels are too low
Glucagon is released, which causes some of the glycogen to be converted into glucose, increasing blood glucose levels
What is type 1 diabetes
The pancreas does not secrete enough insulin, so blood glucose levels could rise to dangerous levels
What is type 2 diabetes
The body stops responding to its own insulin that was produced
What two factors are plants sensitive to
Light and gravity
What is a plant’s response to light known as
Phototropism
What is a plant’s response to gravity known as
Gravitropism or geotropism
What is the hormone which controls the responses of plants to light and gravity
auxin
If light is falling on on the left of a shoot and the right is unlit, which side does auxin build up on
unlit side
What are some uses of auxin
weedkiller, rooting powders, tissue culture
How can ethene be used in agriculture
To ripen fruits
What can gibberellins be used for
Increase fruit size
End seed dormancy
promote flowering
what are the two main waste products of the body
carbon dioxide
urea
What is urea
nitrogenous waste produced by the breakdown of excess amino acids in the liver
How is urea removed from the body
through urine
