Topic 9

What are sensory signals and cues used for?

Organisms use them to inform short-term and long-term environmental changes

What are abiotic changes?

They are changes in non-living parts of an ecosystem

What are biotic changes?

Changes in an ecosystem's living features

On what scales can biotic and abiotic changes vary?

Spatial and temporal

Do cues and signals have intrinsic meaning?

No, only the meaning that is interpreted by different organisms

What are signals?

Signals are communicative changes in an environment that helps the sender be selected for and is beneficial to the sender if the receiver responds

What features of cues are important in detection?

It being readily reliable and discernible.

How do organisms distinguish between cues?

Sensory methods based on the cue, their habitat and lifestyle

What sensory modalities can organisms use to distinguish between cues?

Chemical, electrical, mechanical, photic, magnetic and auditory

The range of sensory modalities is dependent on what?

The organism

What are cues often used to indicate?

The presence of predatory or prey

Are responses to cues and signals innate or learnt?

They can be either.

What are signals?

Organism produced acts or structures used to communicate and influence other organisms behaviour to their benefit.

What are receivers?

Organisms that alter their behaviour based on signal they receive?

How do signals evolve?

When they effect receivers

What are cues?

Incidental sources of information that unintentionally influences a receiver's behaviour that is usually not beneficial to the sender.

What contexts are signals and cues usually used?

Social contexts, like social hunting

What are signals detected by?

Sensory receptors

What are sensory receptors?

Specialised protein molecules

What are the most common sensory receptors?

Chemoreceptors, thermoreceptors, mechanoreceptors and photoreceptors

What are the signals detected by chemoreceptors?

chemical compounds

What are the signals detected by thermoreceptors?

Temperature

What are the signals detected by mechanoreceptors?

Motion

What are the signals detected by photoreceptors?

Light

How do chemical signals open sensory receptors?

Through molecule and receptor specific binding for direct or indirect activation.

What is direct activation?

When the binding directly opens a channel in the cell membrane

What is indirect binding?

When the binding causes an intracellular protein to be activated, which they carries a signal to open another protein channel

How do thermoreceptors open ion channels or activate other proteins?

They change shape in response to temperature

How are mechanoreceptors activated?

Through mechanical signals of movement, stretch and vibration.

How are photoreceptors activated?

They temporarily change shape in response to light wavelengths, then cause a signalling cascade to travel to central sensory organs or control centres

Sensory receptors can evolve to become more selective in stimuli detection.

Why do plants detect light using photoreceptors?

to modulate their response to them.

What is chromophore?

Chromophore is the pigment that allows for photoreceptors to absorb light

What the absorbance of different lights cause?

Change in photoreceptor structure so signalling cascades can be facilitated

What do signalling cascades lead to?

Growth and morphological development

What are phytochromes?

Photo receptors that use active and inactive phytochrome to control metabolic patterns

What does active phytochrome absorb?

Far red light

What does inactive phytochrome absorb?

red light

When is there far red light?

At high temperatures

When is Pfr converted into Pr?

When there is far red light or in the dark.

What does the presence of active phytochrome do?

Repress stem elongation

Why does closure of a Venus flytrap only occur after two deflections?

The CNS of a Venus flytrap can't detect was the stimulus is with one deflection and won't invest energy

What are biological clocks?

Molecular mechanisms that coordinate physiological changes in respond to recurrent changing light levels

What do biological clocks follow?

circadian rhythms

What do biological clocks respond to?

Light and seasonal changes

What can photochromes measure?

The day lengths which indicate what season it is

What do photons regulate?

Photoperiodism

What is photoperiodism?

A plant's collective biological response to a photon period

What does regulation of photoperiodism depend on?

The conversion between active phytochrome and inactive phytochrome

What occurs when inactive chrome converts into active phytochrome?

Cytoplasmic molecules are activated or translocated to the nucleus to regulate gene expression

When does inactive chrome converts into active phytochrome?

When there is red light

What happens to active phytochrome levels in winter?

They completely drop by sunrise because of the longer nights.

What do fluctuating phytochrome levels activate in plants?

Their flowering patterns to synchronise their behaviour with the seasons

What is gravitropism?

How plants grow and move in response to gravity and develop directional senses

What is positive gravitropism?

Growth in the direction of gravity, downwards

What is negative gravitropism?

Growth in the opposite direction of gravity, upwards

What do root caps contain?

Statocytes, gravity sensing cells

What do statocytes function as?

Statoliths

How do statocytes sense gravity?

They contain amyloplasts, starch filled organelles, that settle downwards in response to gravity.

Where is the location of statoliths in vertically oriented roots?

Near the bottom of the cell

Where is the location of statoliths in horizontally oriented roots?

On top of the previous vertical wall, after rotation

What allows plants to sense gravity?

Settled amyloplast

What is thigmotropism?

How plants directionally grow in response to touch

What is negative thigmotropism?

When plant roots grow away from the objects they touch, occurring when the side of contact elongates faster than that of the other side.

What is positive thigmotropism?

When plant roots grow towards the object they touch and contraction occurs at the side of contact and elongation occurs at the side of non-contact

How do sensory modalities send signals to the brain?

Through the nervous system so the brain can process, perceive and respond to the stimuli

What do sensory receptors produce?

Action potentials

How do action potentials create different senses of perception?

They are transported to different parts of the nervous system

How are stronger perceptions produced?

Through increasing stimuli that increasingly activates a sensory receptor

What else does perception depend on?

If the stimuli is perceived within the receptor's optimal range, the number of receptors activated and the rate of action potentials produced by the sensory receptor

What is olfaction?

The sense of smell

How does olfaction occur in vertebrates?

Through chemoreceptors binding to odorant molecules in the nasal cavities epithelial tissue and sends information to nerves in the olfactory bulb or to the brain for processing

What is olfactory sensitivity?

The discrimination of odorants through odorant molecules being able to bind to different receptor proteins, which can be up to 350.

How is a complex odorant molecule perceived?

Through the activation of glomeruli, unique combinations of nerve clusters

What are pheromones?

Chemical signals between conspecifics

What are conspecifics?

Individuals of the same species

What do pheromones affect?

Behavioural responses

How do animals measure day length?

Through photoreceptors in the eyes

How does light detection influence animal behaviour?

Migration that indicates when an environment is optimal for resources, to survive in, etc.

What are the structures of photoreceptors in animals?

Bundled sensory structures

What are rhopalids?

Sensory structures of neuron networks, gravity cells and photoreceptor cells in jellyfish that detect different light wavelengths, transport the information to the bell, which changes muscle contraction to direct migration

What causes stinging within jellyfish tentacles?

The firing of cnidocyte cells through photoreceptor detection

What do photoreceptors control in vertebrates?

The biological clock

What controls the release of neurotransmitters and peptides for physiological processes?

The SCN receiving photoreceptor information through the retinohypothalamic nerve tract\

Explain how sensory processing in animals differ from plants?

In most animals, sensations are transported to the central nervous system in order to be process, perceived and so the body can prepare a response to it. Contrastively, plants use their receptors to conduct an immediate response to signals and cues

What is the somatosensory system?

CNS and PNS parts that can sense and process touch, pressure, pain, temperature, body movement, etc.

What do sensory receptors convert information into?

Action potentials that can generate a nerve impulse

Where do nerve impulses travel to?

The CNS through ascending pathways

What are preceptive impulses?

Those related to body movement

Where to proprioceptive impulses go?

The somatosensory area of the cerebral cortex or the cerebellum

Where are impulses consciously perceived?

In the cerebral cortex

Describe the somatosensory system and its three main levels.

CNS and PNS parts that can sense and process touch, pressure, pain, temperature, body movement, etc. It has a receptor level, circuit level and perceptual level. At the receptor level, the stimulus excites a sensory receptor, which then is converted into an electrical signal to generate an action potential. When the action potential of a neuron reaches a certain threshold, a nerve impulse is generated, reaching the circuit level. This is where the nerve impulse reaches the CNS through several ascending pathways. Here, majority of sensory impulses reach the cerebral cortex's primary somatosensory area, whilst proprioceptive impulses are processed in the cerebellum. This is when sensory information can be interpreted by the CNS on a perceptual level