Sensory concepts Flashcards
Why do organisms need sensory inputs/conceptS?
organisms need information about thier food sources, risk of predation and prescence of competition and location of mates in order to survive and propogate
this can be provided through sensory signals and cues
how are sensory cues conveyed, general?
conveyed by different sensory modalities. It is important that they only convey information if it is reliable and detectible. These signals often have innate responses
abiotic changes
temperature
humidity
sunlight
biotic changes
abundance of food
competition
predators/pathogens/parasites
reproductive partners
what are cues?
readily and reliably discernible from background noise
has to always mean the same thing
has to be different from other background information in order to be meaningful
sensory modalities?
the channels through which animals receive and perceive sensory information from their environment
types include
- chemical
-electrical
- mechanical
-photo
-magnetic
-auditory
each organism has a range within each of its sensory modelities that it can perceive cues from its surroundings (hearing ranges or the visible light spectrum)
signals
are acts of structures, generally created by an organism that influences the behaviours of other organisms or receivers
they evolved specifically because of the effect they have on their intended receivers
can initially evolve for one purpose and be co-opted for another
sensory receptors
the different cues and signals an organism is capable of sending depends on the sensory receptors it possesses
they all function via changes in action potentials across cellular membranes
they are specialised protein molecules
there are 4 basic ones primary sensory receptors are:
- chemo receptors
- thermo receptors
- mechano receptors
- photo receptors
they enable organisms to detect chemical compounds, temperatures, motion and light
chemical receptors
chemical sensitive protein receptors that are activated through physical interaction with specific types of molecules through lock and key mechanism
they can be activated through direct or indirect activation
direct activation
when interaction directly opens a channel in the cell membrane
indirect activation
activation of another protein inside the cell that then carries the signal along, opening a different protein chennal through which ions pass
temperature sensors
modified versions of chemical receptors
they change shape in response to changes in temperature, enabling the passage of ions across the cell membrane
can be both chemical and temperature receptors
motion sensitive proteins
mechanical movement signals through movement, stretch or vibration
channels that extend through the cell membrane, where stimuli causes the channels to open, allowing ions through
photo receptors
respond to specific wavelengths of light
proteins absorbs energy of the photons and temporarily changes shape, using this energy to cause ions to move in channels
photoreceptors in plants
plants have a wide variety of photoreceptors
they often contain photopigments
photochromes are a class of photoreceptor in plants that can sense red and far-red light allowing plants to respond to the intensity and duration of colour of the environmental light
photopigments
protein compound bound to a non-protein light absorbing pigment called the chromophore
can possess more than one type
when it absorbs light they change shape, triggering a signalling cascade which can even trigger gene expression
Growth through photoreceptors
For example, bright direct sunlight contains more red light than far-red light
plants use phytochromes to adapt their growth in response to levels of direct sunlight or shade.
Exposure to far-red light in shaded regions triggers the elongation of stems and petioles in search of light.
On the other hand, exposure to red wavelengths from unfiltered sunlight enhances lateral growth and branching.
what are circadian rhythms
24 hour behavioural cycle
intrinsic, timekeeping, molecular mechanism
allows plants to coordinate physiological activities over a 24-hour cycle called circadian rhythms
What is the phytochrome system
light sensitive receptors that allow plants to respond to seasonal changes
they do this by measuring day length (photoperiod) and enables plants to compare the duration of dark periods over several days
they regulate photoperiodism
photoperiodism what is it and how does it work?
collective term for the biological responses of plants to variations in teh relative lengths of dark and light periods
it depends on the cycling between inactive Pr and active Pfr
phytochromes are synthesised in the dark in their inactive form in the cytoplasm, they absorb red light in the day and turn into the active form
Pfr can activate cytoplasmic molecules or translocate to the nucleus and regulate gene exprerssion
at light Pfr reverts back to Pr through darkness reversion or destruction by enzymes
Due to the changing in day/night ratios in seasons, this changes the Pfr/Pr ratio in plants, changing plant activity
for example: higher Pfr (active) may cause flowering in some plants that flower in longer days (summer), and vice versa
How to plants know which way to grow/which way is up and down (especially for roots)
they adjust their position by changing the rate of growth/elongation in different tissues in asymmetrical ways
this can be done through gravitropism
what is gravitropism?
growth in response to gravity
this is how plants know which way is up down
positive gravitropism
- growth in the opposite direction to gravity/with gravity
negative gravitropism
- growth in the direction of gravity/against gravity
what are statocytes, how do they work?
specialised cells on root caps that can sense gravity
amyloplasts/statolyths are dense starch filled organelles
they settle downward in the statocyte in response to gravity
the direction in which they settle shows gravity, and allows the plants to either undergo:
- assymetrical elongation of roots (horizontal root plants)
growth is stimulated on the top of the root, and supressed on the underside, working to curve roots down - symmetrical elongation of roots (for verticle plants)
What else influences plant direction growth other than gravity and light?
touch
plant grow and wrap around things
plants also grow around obstacles
what is thogmotropism and how does it work?
directional plant growth in response to touch
negative:
when plants encounter an obstacle they grow around it to avoid it
positive:
when plants encounter an obstacle they grow towards them, rapidly coiling
What are sensory organs? What do they do?
sensory receptors are bundled together into sensory organs
they receive information initially and process it, then send it on to the brain depending on the sensory modality of the species in general
How does a signal pass to the brain
pass from peripheral sensory receptors along the nervous system to the brain for processing, perception and response. Using action potentials generated by sensory receptors.
How does the strength of stimuli occur?
range of the specific receptor which is activated, if it is inside the range, you will perceive it
the number of sensory receptors that are being stimulated
the rate of actions potentials produced by the sensory receptor
Smell, how does it work? Example
chemoreceptors embedded in a layer of epithelial tissue in the uppermost tissue in the uppermost region of the nasal cavity
specific oderant molecules bind to the cavity and send informationto other nerves within the olfactory bulb and onto the brain for processing
oderant molecules can be complex and multiple parts of the molecule can bind to multiple different receptors, therefore they can activate a unique sense of nerve clusters within the olfactory bulb called the glomeruli
what are pheromones
chemical signals used for communication among conspecifics (individuals of the same species)
individuals secrete pheromones into the environment and trigger a specific behavioural response
can attract mates, cause alarm signals etc.
Light detection in animals
Eyes and eye-like structures determine light
The suprachiasmatic nucleus (SCN) sits within the hypothalamus deep in the centre of the brain, right above the optic chiasm where the nerve of the eyes cross over via the retinohypothalamic nerve tract
The retinohypothalamic nerve tract stimulates the release of specific neurotransmitters and other peptides that interact with other regions of the brain and control many physiological processes, like sleep, digestion and thermoregulation
what is the somatosensory system? what does it do?
central and peripheral nervous ststem component that senses and processes touch, pressure, pain, temperature, body position or proprioception
what are the 3 levels the process of sensation takes place at/
receptor
circuit
perceptual
How does the somatosensory perception work?
incoming stimulus excites a sensory receptor
converted to electrical signal, generating a graded potential
graded potential reaches a threshold, and a nerve impulse is generated
At the circuit level, the impulse is received and reaches the CNS throgh several ascending pathways
majority of the impulses reach teh somatosensory area of teh cerebral cortex, but some proprioceptive impulses are processes in the cerebellum
sensory information is processes by the CNS at the perceptual level
what is homeostasis
maintenance of relatively constant internal environments
How to thermoreceptors work?
Thermoreceptors detect the change in temperature, the message goes through the CNS and reaches the brain, or the control centre, then the brain compares the stimulus with a set point.
If it is outside this set point/range, then the effectors will cause physiological change in order to counteract the change and regain homeostasis.
One of the physiological changes in this case would be sweat glands producing sweat to cool you down
Thermal response curves and maths
Q10=Rt/(Rt-10)
where Q10 denotes the rate of change of a reaction over a 10 degree change in temperature
the rate of reaction at a given temp/rate of reaction at 10 degrees less
if Q10=1 then the OROR doubles with each increase in temperature of 10 degrees
therefore is Q10=3 a tripling
What is acclimitisation
organisms can eventually adapt to their surroundings, shifting the optimal ROR into the range of temperature to which they are exposed
How do sedentary plants acclimate
they have limited means for controlling their internal temperature, these strategies are effective
How do large mobile plants acclimate
the maintenance of an optimal internal temperature (thermoregulation) occurs via physiological and behavioural means which enable individuals to balance the heat they gain from their environment with the heat they lose
What are ectotherms and endotherms?
Ectotherms
Primarily rely on heat generated from external sources (cold blooded)
Endotherms
produce heat internally (warm blooded)
what are heterotherms and homotherms
body temperature fluctuates=heterotherm
body temp remains the same=homotherm
Physiological thermoregulation for endo and ectotherms
can all regulate physiologically to some degree
endotherms have greater capacity because they can adjust metabolic rate and heat internally
how to organisms gain or lose heat?
radiation from the sun or sky
lose heat produce via metabolism through conduction, convection or evaporation
exampels of physiological responses to thermoregulation
vasoconstriction
vasodilation
shutting off blood to specific regions of the body
thermoregulation curve explained wiht ecto and endo
CTmin and CTmax are at the 2 points of zero on performance, they indicate the thermal tolerance breadth
Topt is the top of the curve
For ectotherms, they will be linearly dependent on heat, whereas for endotherms, they may increase slightly with heat, but too much will ultimately result in a decrease
what is a therone neutral zone
endotherms have a therone neutral zone, a temp range where the cost of maintaining optimal body temperature is minimised,
when it is below, you increase metabolic heat production to compensate for heat loss
when it is above you increase metabolic rate because it costs energy to dump heat from the body when it is already hot
what is thermal conductance
the rate at which an animal exchanges heat wiht its environment
