4. Communication Flashcards
Identify the role of the receptor
To convert energy into nervous messages which can be transmitted throughout the body.
Identify the purpose of communication
Increase efficiency when:
- collecting poles
- warning a nearby predator
- hunting and defending resources
- nest building, raising and protecting young
Define: receptors
Sensory structures that fetch changes in the environment. Can be nerve endings, single receptor cells or receptor cells in groups.
Identify and describe the five types of receptors
Mechanoreceptors: stimulated by forms or mechanical energy, such as pressure (touch), motion and sound. Hair cells are mechanoreceptors which can be found in the ear for hearing and they detect motion.
Nociceptors: detect excess heat, pressure and other stimuli which can create the sensation of pain.
Thermoreceptors: respond to heat energy, helping to regulate body temperature. These receptors send nervous impulses to the hypothalamus.
Chemoreceptors: detect changes in the osmolarity (solute concentration) of blood and can stimulate the reabsorption of water from the kidneys. Other receptors respond to specific molecules, or can produce taste and smell.
Electromagnetic receptors: detect electromagnetic energy much as light, electricity and magnetism. Photoreceptors detect visible light and are responsible for sight. Electroreceptors can detect electric fields in order to detect surroundings (such as in platypuses)
Explain the stimulus response pathway
- Stimulus: a change in the environment that stimulates one or more receptors
- Receptor sends nerves impulses to messenger
- Sensory nerve sends impulse to the CNS which coordinates a response
- Messengers (motor neurones) send impulses to effectors to carry out response
- Organisms responds to stimuli.
Identify the two communication systems and where they intersect
Nervous system
Endocrine system
Hypothalamus
Describe the different between a sensation and a stimulus.
A sensation is not a stimulus. A sensation is the feeling we experience when the nerve impulses fro the stimulus arrives in the brain
Identify how different organisms use three different sense
Auditory: Bat; uses ultrasound and ears to eco-locate surroundings. Can locate prey and its environment at night.
Olfactory: silkworm moths; females emit pheromones that males detect by chemoreceptors in their antennae. When moths are together, pheromones also trigger courtship behaviours
Tactile: Chimps; greet each other with touch to establish social relationship.
Define: Visual Acuity
The ability to see objects sharply and clearly
Identify the structure and function of the conjunctiva
S: Layer of surface cells, forming mucous membrane of inner surface of eyelid and outer surface of sclera
F: keep eye moist
Identify the structure and function or the cornea
S: At font, sclera becomes transparent cornea. No blood vessels Cells obtain oxygen from tears Form nerve endings F: Fixed lens Does 60% of light refraction
Identify the structure and function of the sclera
S: tough, connective tissue, thickest as the back of the eye, surface contains small blood vessels and nerves
F: mechanical support and physical protection. Attachment site for 6 muscles, assist in focussing process
Identify the striation and function of the choroid
S: thin layer of between sclera and retina. Extensive blood capillaries, cell secrete melanin
F: deliver blood and oxygen to retina, prevent internal refraction of light into the eye.
Identify the structure and function of the retina
S: Photosensitive layer, outer layer of cells containing pigment, melanin
Thicker, inner layer containing photoreceptors (rods and cones), nerve cells and blood vessels
F:Melanin absorbs light to prevent reflection
Photoreceptor transforms lighting energy into electrical impulses that brain can read.
Liquid lens
Identify the structure and function of the iris
S: Blood vessels, pigment cells and 2 layers of smooth muscle fibres
- Pupil-constricting muscles form a series of concentric circles around the pupil. In response to bright light, they contract and the diameter of the pupil decreases
- Pupil-dilating muscles extend radially away from the edge of the pupil. In response to dim light, they contract and the diameter of the pupil increases.
F: Muscles contract and relax to control amount of light that penetrates the eye
Identify the structure and function of the lens
S: Lies behind the cornea and held in place by suspensory ligaments
Transparent colourless
No blood supply
F: Focus visual image into photoreceptors in retina by changing physical shape
Distance = flattened shape
Close object = spherical
Identify the structure and function of the Aqueous Humour
S: In front of lens, behind cornea
Transparent colourless
Clear, watery fluid produced by ciliary body
F: Forms a fluid cushion and pressure to help maintain shape and stabilises position of retina
Provide nutrient supply and removal of wastes through tiny ducts
Identify the structure and function of the Vitreous Humour
S: Behind lens Transparent colourless Does not circulate Jelly-like F: No nutritional function Maintains spherical shape Supports retine Liquid lens
Identify the structure and function of the ciliary body
S: Attached to outer edge of iris and junction of sclera and cornea
Ciliary muscle connected to suspensory ligaments that hold the lens in place
F: Contraction and relaxation to control amount of light that penetrates the eye
Identify the structure and function of the optic nerve
S: Each nerve = 1 million nerve fibres
Meet at optic chiasm from both eyes
F: Carries visual information as electrical signals from photoreceptors to brain
Receives information from both eyes
Allows depth perception.
Right visual field goes to left occipital lobe.
Left visual field goes to right occipital lobe
Describe the limited wavelength of light detected by humans and compare with other organisms
Light is a type of electromagnetic radiation. Visible light is a small band on the electromagnetic spectrum, also including gamma, UV rays.
Humans can only see wavelengths between 380-780 nanometers.
Bees can detect UV radiation (shorter than 380nm).
Rattlesnakes can detect infrared radiation (greater then 780)
Identify the condition in which the refraction of light occurs
Light changes speed when it moves through different medium (300,000km/s in air). This causes it to change direction, referred to as refraction.
Light rays bend in different ways depending on the shape of the transparent media. In Concave lens, the light rays diverge, and in convex they converge.
The point in which all light rays meet is the focal point.
Identify the refractive media in the eye
Visual acuity of the eye depends on the image being clear, which is achieved by the focal point landing on the retina. Cornea: 60% of refraction Aqueous Humour Lens: 40% of refraction Vitreous Humour
Define: accomodation
The process in which ciliary muscles expand and contract to change the convexity of the lens, to adjust the focus of an object so the focal point of the refracting light is on the retina
Describe how accomodation works when views close objects
ciliary muscles contract, causing sensory ligaments to relax, making the lens more spherical. The rounded shape increases the refracting power.
Describe how accomodation works when view distant objects
ciliary muscles relax, causing sensory ligaments to pull at the edge of the lens, causing the lens to flatten and become narrow. Refracting power of the lens of low
Define Myopia and technologies used to repair it
if the eyeball is too deep, or the restring curvature of the lens is too great, the focal point of an image of a distant object will form in front of the retina. As a result, an individual will see distant objects out of focus.
To fix: Corrected by using concave (diverging) lenses. These lenses spread refracting light rays apart, as if the object were closer to the eye.
Contact lenses: rest on cornea, using natural moisture to adhere to eye. The back surface of the contact lens is contoured to exactly fit the curvature of the cornea, in order to prevent scratching and damage. They provide a more normal image size as they are closer to the eye.
Define Hyperopia and technologies used to fix it
if the eyeball is too shallow, or the resting curvature of the lens is to flat, the lens cannot provide enough refraction to focus near images onto the retina. As a result, the focal point occurs beyond the retina, causing blurry vision.
To fix:
Corrected by using convex (converging) lenses. These provide additional refraction.
Identify technologies used to correct myopia and hyperopia
Radial keratotomy: surgically reshaping the cornea to alter its refractive power. A surgeon makes radial cuts with a diamond knife on the outer edge of the cornea. Corneal healing can take several years and there are concerns that the procedure creates weak points in the cornea.
Photorefractive keratectomy: uses a computer-guided laser to shape cornea to exact specifications. However, issues with cloudiness of the cornea.
Define: cataract
Abnormal lens that has lost its transparency. Lens takes on a ‘yellowish’ hue which causes objects to look hazy because of the irregular refraction of light and are dim because light of reflected off the lens rather than passing through the eye.
Recount the cataract procedure
- Eye is cleaned
- Lens us removed thought a tiny incision, using ultra-sound to break it into pieces
- New lens in inserted
Describe the social impacts of cataract surgery,
Cataracts are the first cause of blindness in the world. Whilst the treatment is simple, 90% of all cataract patients are in developing countries, thus the financial and physical access to treatment is limited.
Fred Hollows established eye lens factories in developing countries, enabling individuals to regain sight. In Nepal, Hollows was able to develop a cataract treatment for $7. The World Cataract Foundation is also involved in giving sight back to the impoverished.They supply countries with the intraocular lenses, equipment and medical supplies, yet train local doctors to perform the surgery.
Identify and describe the two layers of the retina
- Think inner layer of photoreceptors and neurones
2. Thin outer layer of cells containing melanin that absorb light to prevent reflection
