5.8 The Nervous System Flashcards
What are the three major parts of the bee brain?
Protocerebrum, Deutocerebrum, Tritocerebrum
Which part of the bee brain is the largest?
Protocerebrum
What structures are included in the protocerebrum?
- Optic lobes
- Mushroom bodies
- Central complex
What are mushroom bodies involved in for bees?
- Olfactory learning
- Visual learning
- Decision making
In which type of bee are mushroom bodies more prominent?
Forager bees
What is the function of the central complex in the bee brain?
Monitoring and organizing motor patterns
What type of stimuli do neurons in the central complex respond to?
- Mechanosensory
- Visual
- Chemical
What is the role of the dorsal rim of the compound eye in bees?
Sensitive to polarized light used as a compass for navigation
What structures are found in the deutocerebrum?
- Antennal lobes
- Antennal mechanosensory and motor center
Where do the antennal nerves terminate?
Deutocerebrum
What is the tritocerebrum?
A small part of the brain consisting of two lobes beneath the deutocerebrum
What connects the two lobes of the tritocerebrum?
A commissure that passes behind the oesophagus
From where do the circumoesophageal connectives to the sub-oesophageal ganglion originate?
Tritocerebrum
Fill in the blank: The tritocerebrum contains nerves with _______ and _______ elements.
Sensory, Motor
What is each compound eye made up of?
5-6,000 individual lenses called ommatidia.
How are ommatidia connected to the brain?
via neurons.
What initiates the development of the ommatidium?
The development of the ommatidium arises from a thickening of the ectoderm over the surface of the optic lobe.
What happens to ommatidia in a newly hatched larva?
In a newly hatched larva, the ommatidium is not apparent.
What do the cells in the larva develop into?
The cells join to form spindle-shaped cells whose ends send out processes into the optic lobe.
What do retinulae cells form from?
Retinulae cells form from the spindle-shaped cells moving inwards away from the cuticle.
How is the corneal lens formed?
The cytoplasm of 4 cells converts into a vitreous substance, forming the corneal lens.
What surrounds the corneal lens?
Two further cells surround the lens, forming the primary pigment cell.
What encloses the retinula?
The secondary pigment cells enclose the retinula.
How many cells initially form the retinula?
The retinula is formed initially of 8 cells and ultimately of 9 cells.
What is the structure of the retinula cells?
The cells are twisted around a core and join on the axis, with microvilli from each cell oriented to form the rhabdom.
What types of light wavelengths do retinula cells have sensitivities to?
Retinula cells have differing sensitivities to colours:
2 green, 2 blue, 2 ultraviolet light, 2 blue or green and the 9th short cell is sensitive to polarized light.
What photopigment do microvilli contain?
A photopigment called rhodopsin.
What happens when rhodopsin reacts with light?
A signal is passed to the optic lobe.
When is the compound eye fully formed?
By the pupal stage.
Crystaline cone
4 cells with vitreous centre
Primary pigment
Cells containing pigment in ommatidium. Stops light transferring to adjacent cells
Retinula
9 twisted cells 8 long one short except at eye edge 9 long
Rhabdom
microvilli of retinula cells reactive to differing wavelengths
Rhodopsin
pigment in microvilli creates energy for generation of information passed to optic lobe
What are ocelli?
Three simple eyes (ocellus) located on the forehead of the bee.
* Location is to front in drone because of size of compound eyes.
* Construction (see slide)
* A single lens overlying a retina composed of a layer of about 800 photoreceptor cells.
* Does not focus images on retinal layer as focal plane lies beneath the retina in the ocellar nerve.
* Designed for sensitivity at the expense of acuity.
* Especially sensitive to the UV part of the spectrum.
* Have a role to play in controlling the pitch
How do ocelli differ from ommatidia?
Ocelli do not focus light like ommatidia; they are more concerned with recognizing the presence of light and UV light.
What is the structure of the ocellus?
The ocellus has a corneal lens formed from thickened transparent cuticle.
What is beneath the lens of the ocellus?
Beneath the lens are approximately 800 light-sensitive retinal cells in a layer.
What is a retinula?
A retinula is a grouping of 2-3 retinal cells that forms an axis creating a rhabdom.
How do retinula connect to the brain?
The retinula have axons that connect to the brain.
When do ocelli form during development?
Ocelli form early in a young pupa as a thickening of the epidermis.
What happens to some cells in the early stage of ocelli development?
Even at an early stage, some cells differentiate light and connect to the brain via the optic nerve.
How do honeybees perceive colors?
Honeybee sight is shifted towards the ultra violet end of the spectrum, red is seen as black and the bee can perceive ultra violet sensitive patterns on plants.
What is the role of ommatidia in honeybee vision?
Each ommatidium focuses an inverted image at the tip of the rhabdom, but the image is blurred due to the fused rhabdomeres.
How do rhabdoms contribute to honeybee vision?
Collectively, the rhabdoms across the ommatidia transmit an erect mosaic image made up of adjacent contributions from all ommatidia.
What determines color perception in honeybees?
Colour is determined by the sensitivity of the rhodopsin.
What is unique about the peripheral ommatidia in honeybee eyes?
Polarised light passes through ommatidia on the periphery of the eye, where the 9th retinula cell extends the full length of the sensory part of the ommatidium.
What is the organ associated with smell?
Sensilla placodea - Plate organ
* Fundamentally important.
* Sensilla placodea or plate organs.30,000 on each of a drone’s antennae. 2-3,000 on queen and
5-6,000 on worker.
* Up to 50 nerve cells in single sense plate.
* Cuticle over cap is porous with 2.400-3,000 pores
What is the organ associated with taste?
Sensilla basiconica - Peg organs
What is the organ associated with touch?
Sensilla trichodea - Hair
What is the organ associated with hearing?
Sensilla scolopophora - Subgenual organs
What is the organ associated with gravity perception?
Proprioceptors - Hair plates of mechanoreceptors
What is the organ associated with heat perception?
Sensilla coeloconica - Pit-peg organs
What is the organ associated with time sense?
X and Y type receptors - POL area of compound eye Narrow band of ommatidia on dorsal rim rim 2-3 deep
What are sense plates in bees?
Sense plates, or sensilla placodea, are sensory structures found on the antennae of bees.
How do the number of sense plates vary among different bees?
The number of sense plates varies by the sex and caste of the bee.
How many sense plates does a drone bee antenna have?
approximately 15-16,000 sense plates on each antenna out of 500,000 sensilla.
How many sense plates does a queen bee have?
2-3,000
How many sense plates does a worker bee have?
5-6,000
How many nerve cells can be found within a single sense plate?
up to 50
What is the general structure of the honey bee’s compound eye?
Each compound eye is made up of a number of single ommatidia which are hexagonal lenses positioned next to each other covering the surface of the eye.
How many ommatidia do different types of honey bees have?
The queen has around 3000, a worker 4000-6900, and a drone 8600.
Why is the image from the ommatidia blurred?
The image is blurred because the rhabdoms are fused rhabdomeres (microvilli of a single cell).
What are Sensilla Placoeda and what do they detect?
Sensilla Placoeda are plate organs that detect smell. They are found on the antennae, with the amount varying by the sex and caste of the bee.
How many sense plates do the queen and worker bees have?
The queen has 2-3,000 sense plates and the worker has 5-6,000 sense plates.
What are Sensilla basiconica, where are they and what do they detect?
Sensilla basiconica are peg organs that detect taste.
* Sensilla basiconica or peg organs.
* Found in 8 terminal sub sections of the flagellum, on the mouth parts and in the mouth.
* 3-5 nerve cells within the organ
* Structure very similar to a trichodea with peg being a very shorthair.
* Each sensilla may react to a different chemical or to a group of chemicals
How do bees use their sensillae during foraging?
Bees use their sensillae to detect the taste and smell of forage while antenating during the waggle dance, matching it to a flower during foraging duties.
What is the role of Sensilla trichodea and where are they located?
Sensilla trichodea are hair-like structures that sense touch. They are located all over the bee and bend when touched.
How does the bee’s brain respond to touch stimuli?
When something touches the bee, it generates many impulses that the brain or ganglia interprets. If the stimulus is strong enough, the bee will take action.
* Five different types of trichoid sensilla and very difficult to distinguish between them: short, slender, flexible to long, stiff and thick walled. Found all over the body.
How they work (Davis)
* The seta receives the stimulus, when something touches it, it bends.
* The membrane cell is a thin flexible part of the cuticle
which allows the seta to move.
* The trochogen cell produces the seta.
* The tormogen cell produces the thin membrane and fills the space beneath it.
* The neuron (nerve cell) is activated by the stimulus and sends an impulse along its axon to the central nervous system.
* The scolopale is a thin cap which contains the dendrites of the nerve cell
What are Sensilla scolopophora responsible for and where are they located?
Sensilla scolopophora are subgenual organs responsible for hearing. They are present on the legs of the bee in groups.
What do proprioceptors hair plates of mechanoreceptors perceive?
They perceive gravity.
What do Sensilla coeloconica detect?
Sensilla coeloconica are pit-peg organs that perceive temperature, carbon dioxide, and relative humidity.
What is the function of X and Y type receptors in the POL area of the compound eye?
They are involved in time perception, consisting of a narrow band of ommatidia on the dorsal rim, 2-3 deep.
How do honey bees perceive color?
Honeybee sight is shifted towards the ultra violet end of the spectrum; red is seen as black. This allows bees to perceive ultra violet sensitive patterns on plants.
What is the significance of the patterns on flowers for bees?
Bees can see patterns on flowers that direct them to the nectaries.
How does each ommatidium contribute to bee vision?
Each ommatidium focuses an inverted image at the tip of the rhabdom, resulting in a blurred image.
What is the role of rhabdoms in bee vision?
Collectively, the rhabdoms across the ommatidia transmit an erect mosaic image made up of contributions from all ommatidia.
How is color determined in bees?
Color is determined by the sensitivity of the rhodopsin.
What is the function of the 9th retinula cell in bee vision?
The 9th retinula cell extends the full length of the sensory part of the ommatidium, allowing for the perception of polarized light.
List 5 colours that the adult honey bee can see
- Green
- Blue
- Yellow
- Polarised light
- Ultraviolet
What are the three key elements of the honeybee nervous system?
The three key elements are:
1. The central nervous system
2. Nerves
3. Sense organs
What comprises the Central Nervous System of a honeybee?
The Central Nervous System is made up of the brain, sub-oesophageal ganglion, segmental ganglia, and the ventral nerve cord.
How is the brain of a honeybee formed?
The brain is formed from three segmental ganglia, while the sub-oesophageal ganglion is formed from the remaining three ganglia.
How many pairs of segmental ganglia are there in a honeybee?
There are 7 pairs of segmental ganglia: 2 in the thorax and 5 in the abdomen.
What is the basic element of the nervous system?
The basic element is the nerve cell or neuron, which consists of a cell body (soma) and cytoplasmic projections.
What are the functions of dendrites and axons in a neuron?
Dendrites specialize in the reception of information, while axons are responsible for transmitting information.
What is a synapse?
A synapse is the point at which neurons pass on or receive information via chemical messengers.
What happens when a stimulus activates a dendrite?
A stimulus causes changes in the membrane surrounding the dendrite, initiating an impulse in the axon, which travels rapidly along its length.
How does the strength of a stimulus affect the response in a honeybee?
The number of impulses from many dendrites determines the subsequent response to a stimulus.
Where are the ocelli located on a bee?
The ocelli are found on the top of the head of the bee, pushed forward in a drone due to the size of the compound eyes.
What is the primary function of the ocelli?
They are thought to detect light intensity and the position of the horizon.
What happens if the ocelli are covered?
If these are covered, the bee forages later in the day and stops earlier.
What forms the outer part of the ocellus?
A convex lens forms the outer part of the eye.
What is located behind the convex lens of the ocellus?
Behind this are transparent cells forming a vitreous layer, probably shaping the lens.
How many light-sensitive cells are found behind the vitreous layer?
Behind these are about 800 light-sensitive cells that detect light and pass a signal along nerve fibres to the brain.
What surrounds the whole ocellus?
The whole ocellus is surrounded by pigmented cells, absorbing any stray light that enters the structure.
The brain consists of :
- Protocerebrum which includes the optic lobes and the corpora pedunculata, which are involved
in the olfactory, learning and visual learning of the honey bee. - Deutocerebrum contains the antennal lobes and the antennal mechanosensory and motor
centre. - The tritocerebrum consists of two lobes that sit beneath the deutocerebrum. Nerves connect to
the labrum and the front part of the oesophagus. It also has important connections to the sub-
oesophageal ganglion.
The ventral nerve cord. There are seven pairs of segmental ganglia, two in the thorax and five in
the abdomen situated on the ventral side of the bee. The ganglion are interconnected by the
ventral nerve cord, two cords of nerve fibres.
Senses - Stretch and movement
- Sensilla scolopophora.
- Elongated and dendrites in two moveable parts so sensitive to movement and vibration.
- Found on the legs of the bee in groups.
- See also Organ of Johnston.
Senses - Cuticular stress
- Sensilla campaniformia. Found in small groups on the mouth parts, antennal bases, bases of
wings, the legs and the sting. - Only one neuron.
- React to stresses in the cuticle.
Sense of Gravity
- Mechanoreceptor sensilla in the neck region, at the petiole and where the leg meets the thorax.
- Detect changes in the body orientation.
Senses - Heat Perception
- Sensilla coeloconica. Pit Peg organs. Sensilla sunk into a cavity.
- Found on the antenna.
- Each sensilla reacting to just one stimulus.
- Responsible for detecting carbon dioxide levels, temperature and relative humidity.
