Plant and Animal Responses Flashcards
Why might plants respond to stimuli?
In order to improve chance of survival which will increase their chance of having offspring
What could a plant do in response to threat from a herbivore?
Employ chemical defences
Give 3 examples of chemical defences
Tannins - deposited in leaves and are toxic to microorganisms and herbivores, make the leaf taste bad
Alkaloids - derived from amino acids, make plants taste bitter
Pheromones - chemicals released by one individual which can affect the behaviour or physiology of another
What are tropisms?
Directional growth responses of plants
Give 4 examples of different tropisms
Phototropism - grows towards the light
Geotropism - grows away from gravity
Chemotropism - can grow towards or away from a chemical
Thigmotropism - shoots of climbing plants wrap around structures to pull the plant up
What is the name given to the process where a plant grows TOWARDS a stimulus?
Positive tropic response
What is the name given to the process where a plant grows AWAY FROM a stimulus?
Negative tropic response
What is the name given to a non-directional response?
Nastic response
What controls plant responses?
Plant hormones
Give 5 examples of plant hormones
Cytokinins
Abscisic acid
Auxins
Gibberellins
Ethene
What do Cytokinins do?
Promote cell division
delay senescence
overcome apical dominance
What does Abscisic acid do?
Inhibits seed germination
Causes stomatal closure
What do Auxins do?
Promote cell elongation
Inhibit growth of side-shoots
Inhibit leaf abscission
What do Gibberellins do?
Promote see germination
Promote growth of stems
What does Ethene do?
Promotes fruit ripening
Where does growth occur in plants?
Meristems
What are the 3 types of meristem?
Apical meristem - found in the apex of roots and cause them to grow longer
Lateral bud meristem - found in buds, allow side shoots to grow
Lateral meristem - form a cylinder near the outside of shoots and roots and allow them to grow wider
How could you investigate the effect of phototropism?
There is a test plant and a control plant
The control plant is illuminated equally from all sides, whereas the test plant is only illuminated from 1 side
Leave them to grow for a few days
The test plant will grow towards the light whereas the control will grow straight up
How could you investigate the effect of geotropism?
Plants are positioned perpendicular to the ground
A control plant is placed on a klinostat which spends very slowly meaning gravity has the same effect on all sides of the plant
An experimental plant is left to grow in the perpendicular position
The control will grow straight whereas the experimental plant will bend away from the ground
When light is shining on one side of the shoot, where would the auxins move to?
The shaded side
How does auxin cause the stem to bend?
It promotes active transport of H+ from the membrane into the cell wall
This lowers pH to a level which is optimum for certain enzymes which break down bonds in cellulose causing the cell wall to be less rigid
How is auxin involved in geotropic actions of roots?
If a root is lying flat, auxin accumulates on the lower side of the root, inhibiting cell elongation
The top side continues to grow which causes the root to bend
Give some commercial uses for auxins
Rooting powder, for growing plants promotes root growth
Growing seedless fruit - treating unpollinated flowers with auxin can grow seedless fruit
Herbicides - In high concentrations, they promote soot growth so much that the stem cant support itself and dies
Give a commercial use of Cytokinins
Because they delay leaf senescence, used to prevent yellowing of lettuce leaves after they are picked
Give commercial uses of Gibberellins
Fruit production - they can make fruit last longer in shops and allow fruit to grow bigger
Brewing - Increase the rate of production of malt which comes from barley seeds
Sugar production - increases the length of sugar cane which improves yield
Give commercial uses of Ethene
Speeding up fruit ripening
Promoting fruit drop in cotton, cherry and walnut
How and why might one want to restrict ethene’s effects in industry?
Ethene could reduce shelf life of bananas when shipping them from the Caribbean
Storing them at low temperatures with little Oxygen and high Carbon dioxide levels prevents ethene synthesis
What is the role of the nervous system?
To coordinate rapid responses to external stimuli
What are the two parts of the nervous system?
Central nervous system
Peripheral Nervous system
What are the two parts of the peripheral nervous system?
Sensory system
Motor system
What are the two parts of the motor nervous system?
Somatic system
Autonomic System
What is the difference in structure of the cells in white and grey matter in nervous tissues?
White matter contains myelinated neurones, whereas grey matter contains non-myelinated neurones
What is the role of sensory neurones?
To deliver action potentials from sensory receptors to the CNS
What is the role of the somatic motor nervous system?
To conduct action potentials from the CNS to the effector muscles under conscious control
E.g any skeletal muscle
What is the role of the autonomic motor nervous system?
To conduct action potentials from CNS to the effectors that are under subconscious control
E.g the heart or many glands
What are the two parts of the autonomic nervous system?
Sympathetic system
Parasympathetic system
What is the role of the sympathetic nervous system?
To prepare the body for action
e.g fight or flight response
What is the role of the parasympathetic nervous system?
To conserve energy and allow normal vital function
What are the 4 main parts of the brain?
The cerebrum
The cerebellum
The hypothalamus and pituitary complex
The medulla oblongata
What is the role of the cerebrum?
Conscious thought
Conscious action
Emotions
Intelligence
Factual memory
What is the role of the cerebellum?
Coordination and movement e.g
Maintaining body position
Judging position of objects
Skeletal muscle contraction
What is the name of the area which connects the cerebrum and the cerebellum?
The Pons
What is the role of the hypothalamus and pituitary complex?
Control of Homeostatic mechanisms, e.g
Thermoregulation
Osmoregulation
ADH release
Hormonal control
What is the role of the medulla oblongata?
Controls non-skeletal muscle, e.g
Cardiac centre
Respiratory centre
Vasomotor centre - regulates circulation and blood pressure
What is a reflex action?
A response to changes in the environment that don’t require any brain processing
What is the function of a reflex action?
To help an organism survive
get out of danger
avoid damage
maintain balence
Why is the blinking reflex referred to as a cranial reflex?
Because the neuronal pathway goes through the brain, however no conscious thought is required
What is a reflex arc?
When the effector and receptor for a reflex are in the same place
What is the name of the reflex when a foreign object touches the eye?
Corneal reflex
What is the name given to the reflex caused when there is a sudden change in light?
Optical reflex
How and why can the corneal reflex be overridden?
Because the sensory neurone also passes an action potential to myelinated neurones in the pons
This then sends it to the cerebral cortex where conscious thought occurs
This can then send inhibitory signals to the pons overriding the signal
What is a spinal reflex?
A reflex that passes through the spinal cord instead of the brain
Means the reflex can happen faster as signals don’t need to travel all the way to the brain
Give an example of a spinal reflex
Knee jerk reflex
Why does the knee jerk reflex occur?
There are specialised stretch receptors in the patella tendon which detect when the muscles are stretched
They are known as muscle spindles
When this change is unexpected they cause the quadriceps to contract to straighten the leg
Enables us to balance on one leg
How many types of neurones are involved in the knee jerk reflex?
Only 2
Sensory neurone –> Motor neurone
Can you inhibit the knee jerk reflex?
No, it doesn’t pass through the brain so it is impossible to inhibit
Give some physiological changes that occur during the fight or flight response
Pupils dilate
Heart rate and Blood pressure increase
Arterioles to digestives system constrict while those to active muscles dilate
Blood glucose levels increase
Metabolic rate increases
Hairs stand up
Ventilation rate increases
Endorphins released by the brain
Which subdivision of the nervous system does the fight or flight response utilise?
The sympathetic nervous system
How does adrenaline act inside the cell seeing that it is unable to enter the cell itself?
Adrenaline (first messenger) binds to a surface protein on the target cell which is associated with a G protein inside the cell
G protein activates adenyl cyclase which converts ATP to cAMP
cAMP is the second messenger and cause an effect inside the cell
Which part of the brain secretes releasing hormones?
Hypothalamus
Which part of the brain secretes tropic hormones?
Pituitary gland
anterior pituitary
How do the hypothalamus and pituitary gland interact to release hormones?
Hypothalamus secretes releasing hormones into the blood
They pass down a portal vessel to the pituitary gland
These trigger the secretion of tropic hormones from the anterior pituitary gland
How does the hypothalamus-pituitary complex stimulate the adrenal cortex? (named chemicals)
Corticotropin-releasing hormone (CRH) is secreted from hypothalamus
this triggers the release of Adrenocorticotropic hormone (ACTH)
ACTH stimulates the adrenal cortex to release glucocorticoids such as cortisol
Give two examples of hormones released by the hypothalamus and their counterpart that is subsequently released from the pituitary gland
Corticotropin releasing hormone (CRH) and Adrenocorticotropic hormone (ACTH)
Thyrotropin-releasing hormone (TRH) and
Thyroid-stimulating hormone (TSH)
How could a damaged pituitary gland impact ones metabolism? possible symptoms?
Damaged pituitary would not secrete the right amount of thyroid stimulating hormone (TSH)
This would mean less thyroxine is secreted by the thyroid gland (underactive thyroid)
This could make you tired, sensitive to cold, or gain weight
Give 3 ways that heart action can be modified by
Increase or decrease in heart rate
Altering force of contractions of the ventricular walls
Altering stroke volume`
What does the term myogenic refer to?
The ability for a muscle to initiate its own contractions at regular intervals
Which part of the brain controls heart rate?
Medulla oblongata
What sub section of the nervous system is heart rate controlled by?
Autonomic nervous system
Which nerve from the medulla will reduce heart rate?
Vagus nerve
Which nerve from the medulla will increase heart rate?
Accelerans nerve
Give examples of different receptors that will affect heart rate via the medulla
Stretch receptors - detect movement in the limbs and increase heart rate
Chemoreceptors - detect when pH in blood decreases (happens when muscles produce CO2) and increase heart rate
Stretch receptors in Carotid Sinus - detect when blood pressure is too high, reduce heart rate
What is the role of an artificial pacemaker?
To provide electrical impulses to the SAN when it can no longer do it itself
Allows the heart to beat regularly and with the correct strength of contraction
What are the 3 types of muscle?
Involuntary (smooth) muscle
Voluntary (skeletal) muscle
Cardiac muscle
Where might smooth muscle be found?
In the walls of tubular structures such as the digestive system and blood vessels
What sub-division of the nervous system is smooth muscle controlled by?
Autonomic
Describe the structure of smooth muscle
Spindle shaped
Each cell contains a nucleus and bundles of actin and myosin
Describe the structure of cardiac muscle
individual cells form long fibres
Fibres form cross-bridges between each other
Cells joined by intercalated discs, which are specialised membranes which allow the free diffusion of ions
What is the name for a cardiac muscle cell?
Myocyte
What is the role of Purkyne fibres?
Carry electrical impulses in the heart
Coordinate contraction to prevent back flow
What is the name for a skeletal muscle cell?
Sarcomere
Describe the structure of a sarcomere
Multinucleated
Surrounded by sarcolemma
Contains the sarcoplasm which contains lots of mitochondria and sarcoplasmic reticulum
Contains actin and myosin
Which subdivision of the nervous system controls skeletal muscle?
Somatic nervous system
What is the name given to the area where the muscle joins to the nervous system?
Neuromuscular Junction
Describe the process of an action potential causing a contraction at a neuromuscular junction
Action potential causes Ca2+ to flood the axon tip
This causes acetyl choline vesicles to bind with the membrane and release into the gap
Acetyl choline diffuses and binds to receptors on the muscle which open Na+ channels
Na+ moves in and depolarises the muscle causing contraction
What are myofibrils?
The contractile units of skeletal muscle
What are the two types of protien filament in the myofibril?
Thin filament
Thick filament
What makes up the light band (I-band)?
Thin filaments
What is the Z-line?
Where the thin filaments are held together
They show the ends of the sarcomere
What makes up the dark band (A-band)?
Thick filaments
What is the H-zone?
The area in the dark band where there is no overlap of the thin and thick filaments
Which protein makes up the thin filaments?
Actin
What is attached to actin the thin filaments?
A molecule of tropomyosin to which is attached globular molecules of troonin
What protein makes up the thick filaments?
Myosin
Myosin has two heads which are mobile and will bind to actin when the binding sites are available
What is sliding filament theory and how can it be shown experimentally?
States that during contraction the thin and thick filaments slide past one another.
Can be shown as on a micrograph, during contraction, Light band (I-band) and H-zone get shorter. The Z-lines move closer together and thus the sarcomere shortens.
This shows the the light filament is sliding over the thick filament
