Detection and Responses Flashcards
What is Phytochrome involved in?
It is a pigment found in many plants and it is involved in several plant growth responses
What are three of the plant growth responses?
- Seed germination: inhibited by far red light and stimulated by red light in many plants
- Shoot elongation: lack of red light and shoots elongate
- Detection of plant spacing: crowded plants receive far-red light from neighboring plants and increase their height
Describe red light and far red light?
- Red light: more direct
- Far red light: reflected light
What is Phototropin?
It is the bending of growing stems toward light sources that have blue wavelengths
Describe how gravity effects plant growth?
- Gravity is sensed along the stem in endodermal cells
- The signaling structures are amyloplasts that sink in the cytoplasm
Describe how a plant moves?
- Plant movement is controlled by cell surface proteins, water potential, and plant hormones
- They do not have muscles
What are the five types of plant movement?
- Photomorphogenesis
- Thigmomorphogenesis
- Phototropisms
- Thigmotropism
- Gravitrophisms
Describe Photomorphogenesis?
-Development in plants is triggered by light
Describe Thigmomorphogenesis?
- Effects the way the plant grows due to “touch”
ex. If a plant is growing on a hill, it will grow larger trunks
Describe Phototropisms?
-Plants will grow toward the light
Describe Thigmotropism?
- Plants grow toward mechanical stimuli
ex. vines grow up walls because they grow toward pressure/touch
Describe Gravitrophisms?
- Plants grow directionally due to earths gravity
ex. Plants detect gravity so they know which end their roots should go
Describe turgor and touch related turgor?
- Turgor: the rigidity of cells, mainly due to fluid absorption
- Touch induced plant movements involve reversible changes in turgor pressure
- If water leaves turgid cells, they may collapse
- If water enters limp cells, they become turgid
- These cells are known as pulvini (area of stem that is effected by turgor changes)
What are two examples of touch responses?
- Snapping of a venus fly trap
- Curling of tendrils
Describe light related turgor?
- Some turgor movements are triggered by light which maximizes photosynthesis
ex. Sunflowers face the sun ALL DAY which is a turgor light response (not a growth response)
ex. Bean leaves are horizontal during the day when their pulvini are rigid but are more/less vertical at night as pulvini lose turgor
Describe gravitrophism?
- Shoot exhibit = negative gravitrophism (grow away from gravity)
- Roots exhibit = positive gravitrophism (grow with gravity)
Describe Auxin and what it causes in plants?
- It accumulates on the lower side of the stem due to amyloplast position
- It causes asymmetrical cell elongation and curvature of the stem upward
ex. If a plant is turned sideways, its stem will begin to grow longer on the bottom side so that the plant will be growing upright still
Where is gravity percieved in a plant?
- In the roots, the cap is where gravity is detected
- Once detected, signaling triggers differential cell elongation and division
Describe dormancy?
- Dormancy = results in cessation of growth during unfavorable conditions
- Often results in Abscission (dropping of leaves/petals)
- This conserves resources
Describe hormones in plants?
- Chemicals produced in one part of an organism and are transported to another where they exert a response
- In plants, hormones aren’t produced by specialized tissues
Describe Auxin?
- One effect is that is causes an increase in plasticity of the plant cell wall
- It is produced in the lit tip of plant and then migrates to the opposite side (dark side)
- It causes elongation of the cells on the dark side of the plant which therefor causes the plant to bend
Describe Cytokinins?
- Produced in the root apical meristems and developing fruits
- It stimulates cell division and differentiation and promotes growth of lateral buds into branches
- There is also a plant pathogen that introduces genes into the plant genome that increase production of both cytokinin and auxin = causes massive cell division and formation of crown gall tumor
Describe Gibberellins?
- Gibberellins acid hastens seed germination
- Used to extend internode length in grapes which results in larger grapes
Describe Ethylene?
-It’s a gas
-It retards growth by…
Suppressing stem and root elongation
Controlling leaf, flower, and fruit abscission
Hastens fruit ripening
Describe Abscisic Acid?
- Is synthesized main in mature green leaves, fruits, and root caps
- It induces the formation of dormant winter buds
- Counteracts gibberellins and auxin
- It is needed for dormancy in seeds and is important in opening and closing the stomata
What are the three systems that cause animal responses to the environment?
- Sensory
- Endocrine
- Nervous
What are exteroceptors and interceptors in sensory receptors?
- Exteroceptors: sense external stimuli
- Interoceptors: sense internal stimuli
What are mechanoreceptors?
- Part of sensory receptors
- Stimulated by mechanical forces like pressure
What are chemoreceptors?
- Part of sensory receptors
- Detect chemicals or chemical changes
What are energy-detecting receptors?
- Part of sensory receptors
- React to electromagnetic and thermal energy
ex. pigeons can find their way home
How do sensory cells respond to stimuli?
- They respond through stimulus-gated ion channels that are in their membranes
- These channels are open or closed based on the sensory system involved
- They will only respond to specific stimulus
What are Nociceptors?
- Part of mechanoreceptors
- They transmit impulses based on cell damage
- Perceived as pain
- Most are free nerve endings
What are Thermoreceptors?
- Part of mechanoreceptors
- Naked dendritic endings of sensory neurons
- Sensitive to changes in temperature
- Contain ion channels that are responsive to hot/cold
- Cold receptors are located higher in the skin and are more numerous than warm receptors
Describe touch receptors?
- Part of mechanoreceptors
- They contain sensory cells with ion channels that open in response to membrane distortions
What are Proprioceptors?
- Part of mechanoreceptors
- Monitor muscle length and tension
- Provide information about relative position or movement of animals body parts
What are Baroreceptors?
- Part of mechanoreceptors
- Branched network of afferent neurons in the carotid sinus and aortic arch
- Detect tension or stretch in the walls of these blood vessels
What are Sensory Hair cells?
- Part of mechanoreceptors
- Specialized cells with cytoplasmic extensions called stereo cilia
- When stereo cilia bend they send action potential to a sensory neuron
Describe the lateral line system in fish?
- Consists of canals running the length of the fish’s body beneath the skin surface
- Contain hair cells in a gelatinous cupula
- Innervated by sensory neurons that transmit impulses
- Bending of stereo cilia detects currents
Describe hearing?
- Detection of vibrations that are perceived as sound
- Also involves stereocilia
- Auditory stimuli travel faster and further than chemical ones
- Provide better directional info than chemoreceptors
Describe the inner ear?
-Cochlea has three fluid filled chambers, vibrations travel down these canals
-Organ of Corti (in cochlea)…
Has basilar membrane with hair cells
Vibrations of the basilar membranes hair cells press stereo cilia against the tectorial membrane
Send nerve impulses to brain where interpreted as sound
Describe Echolocation?
- Few mammals have this ability which perceives presence and distance of objects by sound
- Emit sounds then determine the time it takes the sounds to return
Describe Balance in vertebrates?
- Gravity receptors consist of two chambers in the membranous labyrinth
- Within utricle and saccule are hair cells (embedded in a calcium rich otolith membrane)
- Sensitive to head orientation (head movement causes the otolithic membrane to move and stereo cilia to bend)
Describe acceleration?
- Semicircular canals detect angular acceleration in any direction
- Have swollen chambers called ampullae
- Hair cell stereo cilia within a gelatinous cupola protrude into them
Describe chemoreceptors?
- Can bind to particular chemicals in extracellular fluid
- Membrane of sensory neuron becomes depolarized and produces action potentials
Describe Gustation?
- Taste
- Broken down into five receptor types (sweet, sour, salty, bitter, umami
- Taste buds are collections of chemosensitive cells associated with afferent neurons
How do arthropods taste?
- Many have taste chemoreceptors
- Flies have sensory hairs that are located on their feet
Describe Olfaction?
- Smell
- Involves neurons in the upper portion of the nasal passages
- Transmits impulses directly to the brain through olfactory nerve
Describe pH?
- Peripheral chemoreceptors are found in the aortic and carotid bodies and is mainly sensitive to plasma pH
- Central chemoreceptors are found in the medulla oblongata and is sensitive to the pH of cerebrospinal fluid
Describe vision?
- Begins with the capture of light energy by photoreceptors
- Four phyla have evolved well-developed, image-forming eyes
- Annelids, mollusks, arthropods, chordates
Describe photoreceptors?
- Vertebrate retina contains two types…
- Rods (black and white vision when illumination dim)
- Cones (color vision and high visual sharpness, most located in central region of retina)
Describe photopigments?
- Rods have rhodopsin (more light sensitive)
- Cones have photopsins
- Each have different amino acid sequence
Describe photopsins?
- Carnivors are dichromats (2 kinds of cones)
- Humans are trichromats (3 kinds of cones)
- Birds are tetrachromats (4 kinds of cones and can see in ultraviolet light)
Describe focus?
- Lens is a transparent structure that completes focusing of light onto the retina
- Nearsighted or farsighted do not properly focus the image on the retina
Describe Infrared?
- Only vertebrates that can sense infrared are snakes
- Have pair of pit organs on either side of the head
- Locate heat sources in the environment
Describe electroreception?
- Energy receptor
- The elasmobranchs (sharks, rays, skates) have electroreceptors
- Ampullae of Lorenzini: can sense electrical currents generated by the muscle contractions of their prey
What is magnetoception?
-When animals can navigate along magnetic field lines of the earth
Descrive sensory receptors and motor effectors of the nervous system?
-Sensory receptors detect stimulus (ex. light, heat, touch)
-Motor effectors respond to the stimulus (ex. muscle)
The nervous system links these two
Describe the central and peripheral nervous systems?
- Central Nervous System: brain and spinal cord
- Peripheral Nervous System: sensory and motor neuron
Describe the Invertebrate nervous system?
- Sponges are only main phylum without nerves
- Cnidarians have the simplest nervous system because their neurons are link in a nerve net, they have no associative neurons, and they’re one big reflex machine
What is the simplest animal with associative activity?
- Free living Platyhelminthes are simplest
- They have two nerve cords that run down the body
- This permits complex muscle control
- Have a rudimentary “brain”
Describe other invertebrate nervous systems?
-Basically elaborations of platyhelminth model
Describe vertebrate brains?
- Enlargement of anterior portion of the nerve cord
- Simplest vertebrate brain has three basic divisions:
1. Hindbrain: heartbeat, respiration
2. Midbrain: process visual and auditory info.
3. Forebrain: process olfactory info, cognition (dominant feature)
Describe the cerebrum?
- In forebrain
- Split into right and left cerebral hemispheres that are connected by a tract called corpus callosum
- It’s hemispheres are divided into four lobes
1. Frontal
2. Parietal
3. Temporal
4. Occipital
Describe the Thalamus and Hypothalamus?
- Thalamus: Integrates visual, auditory, and somatosensory info.
- Hypothalamus: Integrates visceral activities (what happens in the body) and control pituitary gland
Describe the spinal cord?
- Body’s “information highway”
- Interprets simple information with interneurons
- Relays messages between the body and brain
Describe the Peripheral nervous system?
- Consists of nerves and ganglia
- Nerves are bundles of axons bound by connective tissues
- Ganglia are aggregates of neuron cell bodies
Describe the Somatic nervous system?
- Somatic motor neurons stimulate skeletal muscles to contract
- They do this is response to conscious commands or reflex actions
- It only involves one motor neuron
Describe the Autonomic nervous system?
- Subconscious control
- The motor pathway has two neurons
- The first of these neurons is in the CNS and synapses to the autonomic ganglia
- The seconds neuron is in the ganglia and regulates the effectors (which are smooth or cardiac muscle or glands)
