Coordination and response - Paper 1 Flashcards
what happens in the skin when we get too hot
Sweat glands in the skin release more sweat. The sweat evaporates, removing heat energy from the skin.
Blood vessels leading to the skin capillaries become wider - vasodilation - allowing more blood to flow through the skin, and more heat to be lost.
what are stimuli?
stimuli are changes in an organisms environment which we detect using receptors
what are three examples of reflexes and describe their purpose
the pupil reflex - pupils get smaller in bright light to regulate the amount of light which enters the eye,
the blink reflex- eyes blink when there is near movement to potentially protect the eyes from damage,
the swallowing reflex - makes it harder to swallow straight after having swallowed just before, to prevent the throat from over filling and therefore preventing choking
what are the 5 sense organs
skin, tongue, nose, eyes, ears
what is the stimulus for skin
pressure, pain, temperature
what is the stimulus for tongue
chemicals in food and drink
what is the stimulus for nose
chemicals in the air
what is the stimulus for the eyes
light
what is the stimulus for ears
sound
what is the central nervous system
- the central nervous system (CNS) is made up of the spinal cord and the brain.
- the peripheral nervous system carries information to or from the CNS
- when a stimulus is detected by a receptor, impulses (messages) pass down neurones to the CNS which then sends more impulses out along neurones to an effector which causes a response.
what is a reflex
a reflex is an automatic and rapid response, such as when you touch something hot or sharp.
what are neurones
- specialised cells which make up nerves
- sensory neurones carry impulses from sense organ to CNS
- relay neurones are found inside the CNS and connect sensory and motor neurones
- motor neurones carry impulses from the CNS to effectors (muscles or glands)
what are synapses
- the gaps between neurones are called synapses
- the impulse is transmitted from one side to the other using neurotransmitters, which travel across the gap via diffusion
- synapses mean that nerve impulses are unidirectional, meaning they only travel in one direction
- they can also connect more than one neurone
what is homeostasis
the maintenance of a constant internal environment. The nervous system and hormones are responsible for this. e.g the concentration of carbon dioxide in the blood being carefully controlled, body temperature, body water content
how do plants respond to stimuli
- stems will grow towards the light stimulus (positive tropisms)
- roots grow away from light (negative tropisms)
- stem grows against the force of gravity (Negative geotropism)
- roots grow in the direction of gravity (positive geotropism)
describe tropsims in plants
positive tropisms – the plant grows towards the stimulus
negative tropisms – the plant grows away from the stimulus
Phototropism is a response where the stimulus is light, whereas geotropism (also called gravitropism) is a response where the stimulus is gravit
what are auxins in plants
- Auxins are a family of plant hormones. They are mostly made in the tips of the growing stems and roots, which are known as apical meristems, and can diffuse to other parts of the stems or roots.
- Auxins control the growth of plants by promoting cell division and causing elongation in plant cells (the cells get longer).
- Stems and roots respond differently to high concentrations of auxins:
- cells in stems grow more
- cells in roots grow less
how do auxins cause plants to grow toward light
In a stem, the shaded side contains more auxin and grows longer, which causes the stem to grow towards the light. It is vital to note that the plant does NOT bend towards the light.
What does a coordinated response consist of
A stimulus, a receptor and an effector
how does the eye focus light from a distant object?
- when light enters the eye from a distance, the light rays are almost parallel when they enter the eye
- this means they need less rarefaction to be focused onto the retina
- the cornea starts to bend the rays and the lens is less involved
- to get the lens into this shape, special muscles called ciliary muscles relax and the lens is pulled thinner by the suspensory ligaments
how does the eye focus light from a close object?
- light rays from a near object are diverging when they enter the eye and so need more bending to focus them onto the retina
- to do this, the lens must change shape and become more rounded
- to enable this, the ciliary muscles contract which means that the suspensory ligaments are pulled less and the lens becomes more rounded.
what is the bending of light called?
refraction
why do peoples vision get worse when they age
their lens becomes less bendy
what happens in the skin when we get too cold
Muscles contract rapidly - we shiver. These contractions need energy from respiration, and some of this is released as heat.
Blood vessels leading to the skin capillaries become narrower - vasoconstriction - letting less blood flow through the skin and conserving heat in the body.
what happens if blood glucose concentrations get too high
what happens if blood glucose concentration is too low
Cells in the pancreas detect the decreased blood glucose levels
The pancreas produces the hormone glucagon
Glucagon causes the glycogen stored in the liver to be converted into glucose and released into the blood
This increases the concentration of glucose in the blood back to normal levels, at which point the pancreas stops secreting glucagon
