8.2 Reception Of Stimuli Flashcards
Receptor, Receptor cells
Receptor cells that detect stimuli and send impulses to the central nervous system. Many receptors are spread throughout the body, but some types of receptor cells are grouped together into sense organs. Rods and cones are the receptor cells in the eye that detect light.
Sense organs
The eye, ear and skin are examples of sense organs. Each contains receptor cells that detect stimuli and send electrical impulses to the central nervous system. Receptor cells in the eye detect light, those in the ear detect sound, and several different types in the skin can detect touch, pressure, pain and changes in temperature.
Conjunctiva
Protects cornea
Cornea
Bends light
Lens
Focuses light on retina
Iris
Controls annoy the of light entering the eye
Sclera
Protective layer
Blind spot
No light sensitive cells where optic nerve leaves the eye
Yellow spot (fovea)
Most sensitive part of the retina located within the macula, the central area of the retina
Retina
Contains light sensitive cells
Vitreous humour
Transparent jelly
Choroid
Black layer prevents internal reflection of light
Ciliary muscle
Alters thickness of lens for focusing
Photoreceptor
A receptor cell that is stimulated by light and enables us to detects changes in our environment. In the human eye photoreceptors are contained in the retina. There are two distinct types, rods and cones.
Rod, Rods, Rod cell
A receptor cell, found in the retina of the eye, which is sensitive to light. Rod cells contain a light-sensitive pigment called rhodopsin. When light falls on rhodopsin, it breaks down into retinal and opsin. This reaction leads to the generation of an action potential in a neurone in the optic nerve. Rod cells only give black and white vision but are able to work in dim light conditions.
Cone
A receptor cell, found in the retina of the eye, which is sensitive to light. Cone cells contain pigments which are sensitive to light of different wavelengths. Because of this, cones allow colour vision.
Bipolar neurone
A type of nerve cell which has a cell body with two long, thin branches. One of these is a dendron which brings impulses to the cell body. The other is an axon which transmits impulses away from the cell body to other neurones. Bipolar cells in the retina of the eye are important in vision
Ganglion neurone
A particular type of neurone found in the eye. The rods and cones are located in the retina and they are the photoreceptors. They form synapses with bipolar cells which, in turn, synapse with ganglion neurones. The axons of these ganglion neurones make up the optic nerve, which leads to the brain
Rhodopsin
A light-sensitive pigment found in rod cells in the retina of the eye. When light falls on rhodopsin, it breaks down into retinal and opsin. This reaction leads to the generation of an action potential in a neurone in the optic nerve
Non-specific cation channel
A channel in the cell surface membrane that allows any positive ions through, such as Na+ and Ca2
Glutamate
A neurotransmitter thought to be released by rod cells at their synapses with bipolar neurones in the retina of the eye
Dark adaptation
Rhodopsin, the photochemical pigment in the rod cells of the retina, breaks down when it absorbs light. This causes chemical changes within the cell that result in an action potential being generated in the optic nerve. On entering a darkened room, only black is seen because the rhodopsin must be reformed so it can once again be broken down. The reforming of rhodopsin is known as dark adaptation.
Phytochrome
Red and far-red light photoreceptor pigment in plants, some bacteria and fungi. When a red photon is absorbed there is a conformational change from the Pr form to the Pfr,
Photoperiod
The light period during a day. In
temperate regions the amount of daylight varies
throughout the year. In the winter, it is light for a relatively short part of the day. In the summer, it is light for much longer. Photoperiod affects
many living organisms. It controls when birds migrate, when plants flower, and when some marine worms lay their eggs.
Long day plants
Flower when uninterrupted darkness is less than 12hrs. They need Pfr to stimulate flowering.
Short day plants
Flower when the period of uninterrupted darkness is greater that 12hrs. Pfr inhibits flowering
Day neutral plants
Flowering is not affected by day length
Chi-squared test
to determine if an observed set of categorical data differs from the expected using a null hypothesis that there is no significant difference.
Greening
Informal term for the changes that
occur in a plant shoot in response to sunlight,
including development of chloroplasts,
inhibition of shoot lengthening, and stimulation
of cotyledon and leaf expansion. The process is
controlled by phytochromes.
Internode
length of stem between leaves