Plant and Animal Responses Flashcards
Name three chemical defences in plants
- Tannins
- Alkaloids
- Pheremones
How do tannins protect a plant?
They make the leaves taste bad
How do alkaloids protect a plant?
They’re a feeding deterrent to animals, tasting bitter
What is Chemotropism?
On a flower, pollen tubes grow down, attracted to chemicals, towards the ovary where fertilisation can take place
What is Thigmotropism?
Shoots of climbing plants wind around other plants or solid structures to gain support
If a plant responds TOWARDS a stimuli, it is called what?
A positive tropic response
Non-directional responses to external stimuli are called what?
Nastic responses
What is Thigmonasty?
When a plant responds to touch with a sudden folding of the leaves
Name the four effects of Cytokinins
- Promote cell division
- Delay leaf death/fall
- Overcome apical dominance
- Promote cell expansion
Name 2 effects of Abscisic acid
- Inhibits seed germination and growth
- Makes stomata close during low water availability
Name 3 effects of Auxins
- Promote cell elongation
- Inhibit growth of side shoots
- Inhibit leaf fall
What effect to Gibberellins have on plants?
Promote seed germination and growth of stems
What effect does Ethene have on plant growth?
Promotes fruit ripening
In what 3 ways do hormones move around the plant?
- Active transport
- Diffusion
- Mass flow in the Phloem sap or in Xylem vessels
The nervous system divides into what?
The CNS and the PNS (peripheral nervous system)
The PNS is divided into what?
The Sensory System and the Motor System
The Motor System is further divided into what?
The Somatic Nervous System and the Autonomic nervous system
The MYELINATED neurones in the brain do what?
They carry action potentials up and down the spinal cord for rapid communication over longer distances
What is the role of the Peripheral Nervous System (PNS)?
To ensure rapid communication between the sensory receptors, the CNS, and the effectors
The Somatic Nervous System consists of what?
Motor Neurones that conduct action potential from the CNS to the effectors that are under voluntary control e.g. skeletal muscles
Name two differences between the Somatic Nervous System and the Autonomic Nervous System
Somatic = MYELINATED neurones Autonomic = NON-MYELINATED neurones
The Autonomic Nervous System divides further into what?
The Sympathetic and Parasympathetic Nervous System
What is the function of the Sympathetic System?
It prepares the body for activity
What is the function of the Parasympathetic System?
It conserves energy
Name 4 effects of the Sympathetic system
- Pupils dilate
- Increases heart rate
- Increase ventilation rate
- Reduces digestive activity
Name 3 effects of the Parasympathetic system
- Constricts pupils
- Decreases heart rate
- Reduces Ventilation rate
- Increase digestive activity
Name the four major parts of the human brain
- Cerebrum
- Cerebellum
- Medulla Oblongata
- Hypothalamus-Pituitary Complex
What is the Cerebrum, and what is its function?
Largest part of the brain, and organises most of our higher thought process e.g.. conscious thought and memory
What is the Cerebellum responsible for?
It Coordinates movement and balance
What is the Hypothalamus-Pituitary complex responsible for?
It organises homeostatic responses and controls various physiological processes
What is the Medulla Oblongata responsible for?
It coordinates many of the autonomic responses
What are the names of the two cerebral hemispheres?
- Corpus Callosum
- Cerebral Cortex
The cerebellum coordinates the fine control of muscular movements such as:
- Maintaining body position and balance e.g. cycling
- Tensioning muscles
- Judging the position of objects
The Hypothalamus controls homeostatic mechanisms in the body such as:
- Temperature Regulation
- Osmoregulation (Monitor water potential of the blood)
What are the names of the two lobes of the Pituitary gland?
- Posterior lobe
- Anterior lobe
What is the function of the Posterior lobe of the Hypothalamus?
Hormes e.g. ADH that are manufactured in the Hypothalamus, pass down neurosecretory cells and are released into the blood from the pituitary gland
What is the function of the Anterior lobe of the pituitary gland?
It produces its own hormones, which are released into the blood in response to releasing factors produced by the hypothalamus
The Medulla Oblongata contains centres for regulating several vital processes, including:
- The cardiac centre, which regulates heart rate
- The Vasomotor centre, regulates circulation and bp
- Respiratory centre, controls rate/depth of breathing
What are reflex actions?
Responses to changes in the environment that do not involve any processing in the brain to coordinate movement.
Whats the name of a reflex that’s nervous pathway passes through the brain?
A Cranial reflex
What 3 reasons may a blinking reflex be stimulated?
- A foreign object touching the eye
- Sudden bright light
- Loud sounds
What kind of reflex is the knee-jerk reflex?
A Spinal Reflex
Outline the process of the knee-jerk reflex
- Muscles at front of thigh are stretched,
- Muscle spindles (receptors) detect the increase in length of the muscle
- If this stretching is unexpected, a reflex action causes contraction of the muscle
Why is the Knee-jerk reflex quick?
It only involves two neurones, therefore there is only one synapse involved
What are the differences between the knee jerk reflex and the blinking reflex? (2)
Knee Jerk = Spinal reflex Blinking = Cranial reflex
Knee Jerk = 2 neurones Blinking = 3 neurones
Why must the action potentials to override a reflex be carried by myelinated neurones?
Because the neurones carrying impulses to and from the cerebral cortex transmit action potentials more rapidly
Name 3 Physiological changes associated with the fight of flight response
- Pupils Dilate
- Heart rate/bp increases
- Blood Glucose levels increase
- Arterioles to liver/muscles are dilated
The Cerebrum uses sensory inputs from receptors e.g. eyes, to coordinate a suitable fight or flight response
- Inputs feed into sensory receptors in the cerebrum
- The Cerebrum passes signals to the associated centres
- If a threat is recognised, the cerebrum stimulates the hypothalamus
- Hypothalamus increases activity in the sympathetic nervous system
- Hypothalamus stimulates release of hormones from Anterior pituitary gland
What is the role of the sympathetic nervous system in the fight or flight response?
Increased stimulation of the sympathetic nervous system will increase the activity of the effectors.
What system is used if a fight or flight from danger may need a prolonged response?
This is achieved by the endocrine system
Outline the mechanism of adrenaline action
- Adrenaline binds to receptor on cell surface membrane, associated with a G-protein on the inner surface
- G-protein stimulated to activate enzyme Adenyl Cyclase
- Adenyl Cyclase converts ATP to Cyclic AMP (cAMP)
- cAMP causes an effect inside the cell by activating an enzyme
What does the hypothalamus secrete?
Releasing hormones/factors into the blood
What do releasing factors do?
Pass down the portal vessel to the pituitary gland and stimulate the release of tropic hormones from the anterior part of the pituitary gland.
Name the 3 important roles of circulation
- Transport of Oxygen and Nutrients
- Removal of waste products
- Transport of Urea from the liver to the kidneys
Cardiac muscle can be described as what?
Myogenic
Outline the process of initiating a heart beat
- The SAN initiates waves of excitation
- Waves of excitation travel over the arterial walls, through the AVN and down the purkyne fibres
- Continuing to the walls of the ventricles, causing them to contract
The frequency of excitation waves is altered by what?
The output from the cardiovascular centre in the medulla oblongata
Nerves from the cardiovascular centre in the medulla oblongata do not initiate a contraction, but can effect what?
The frequency of the contractions
Action potentials sent down a sympathetic nerve cause what?
The release of the neurotransmitter, Nonadrenaline at the SAN, increasing the heart rate.
Action potentials sent down the Vagus nerve release what?
The neurotransmitter acetylcholine, which reduces the heart rate
What do Stretch receptors do in relation to output to the SAN?
Stretch receptors in muscles detect movement, these send impulses to the cardiovascular centre, informing it that extra oxygen may soon be needed, heart rate increases
What do Chemoreceptors do?
Monitors PH of blood. They detect PH and send action potentials to the cardiovascular centre, increasing the heart rate
How do Chemoreceptors work?
- Exercise makes muscles produce more CO2
- Some reacts with water in the blood plasma, forming an acid, reducing the PH of the blood
- This will affect the transport of oxygen in the blood
- PH change is detected, action potentials sent to cardiovascular centre, increasing heart rate
How do stretch receptors work?
An increase in blood pressure is detected by the receptors. If pressure rises too high they send action potentials to the cardiovascular centre, reducing heart rate
What is involuntary muscle?
Smooth muscle that contracts without conscious control
What is Skeletal (Striated) muscle?
Muscle under voluntary control
Contraction is achieved by interaction between which two protein filaments?
Actin and Myosin
Muscles cannot elongate without what?
An Antagonist (Therefore muscles are usually arranged in pairs)
What shape are the cells in Involuntary/Smooth muscles?
Individual cells, tapered at both end (spindle shapes)
Each individual cell in Smooth muscles contain what?
- Nucleus
- Bundles of Actin and Myosin
Describe the contraction of Smooth muscles
Slowly and Regularly
Where is Smooth muscle found?
Walls of tubular structures e.g. Digestive System/blood vessels
How is Smooth muscle arranged?
In longitudinal and circular layers that oppose each other
How are cardiac muscles arranged?
Cells form long fibres, branching to form cross-bridges to ensure electrical stimulation spreads evenly over the walls
What are cardiac cells joined by?
Intercalated discs
When do cardiac cells contract and relax?
Continuously throughout life
How are Voluntary muscles arranged?
In Antagonistic pairs
What are Voluntary muscle cells composed of?
They’re multinucleate (contain multinucleate)
Surrounded by a membrane called the Sarcolemma
Voluntary Muscle cell cytoplasm is known as what?
Sarcoplasm
The contents of the Voluntary muscle fibres are arranged into a number of what?
Myofibrils
The Voluntary muscle fibre myofibrils are divided into a chain of subunits known as what?
Sarcomeres
What gives Voluntary muscles tissue its striated look?
Actin and Myosin are arranged in a particular banded pattern. Dark bands are A bands, and lighter bands are the I bands
How does Voluntary muscle contract?
Quickly and powerfully
Which nervous system stimulates contractions of skeletal muscles?
The Somatic nervous system
The junction between the nervous system and the muscle is known as what?
A Neuromuscular junction
Outline the process of stimulation of contraction of Skeletal muscle?
- Action potentials arrive at end of axon open calcium ion channels allowing calcium ions to flood into axon tip
- Vesicles of Acetylcholine move towards membrane and fuse
- Acetylcholine molecules diffuse across gap and bind to receptors
- Sodium ion channels open and enter muscle fibres causing depolarisation
- Wave of depolarisation passes along sarcolemma and down transverse tubules
What is a motor unit?
When motor neurones divide and connect to several muscle fibres, which all contract together providing a stronger contraction
What two types of protein filament make up Myofibrils of skeletal muscle?
Thin filaments, aligned to make up the light band. Held together by the Z line
Thick filaments, make up the dark band
What are thin filaments?
Two chains of Actin subunits twisted around each other. Wound around the Actin is a molecule of Tropomyosin
what are thick filaments composed of?
A bundle of Myosin molecules. Each molecule has two protruding head, sticking out either end
What is the sliding filament hypothesis?
During contraction, the light band and H zone get shorter, thus the Z lines get closer together and the sarcomere gets shorter. The thick and thin filaments slide past one another
How does the mechanism of contraction work?
- The sliding action is caused by the movement of the Myosin head
- When the muscle is stimulated, the tropomyosin is moved aside, exposing the binding sites on the actin
- The myosin heads attach to the actin and move causing the actin to slide past the myosin
Outline the process of controlling contraction
- Muscle stimulated, action potential passes along sarcolemma and into muscle fibres
- The action potential is carried to sarcoplasmic reticulum, releasing sodium ions into sarcoplasm
- Calcium ions bind to the troponin, which alters shape, pulling the tropomyosin aside. Exposing binding sites on the actin
- Myosin heads bind to the actin, forming cross-bridges between the filaments
- Myosin heads move, pulling actin filaments past the myosin filament
- The Myosin heads detach from the actin and can bind again further up the actin filament
Outline how ATP provides the energy for contraction
- Myosin head attaches to the actin filament, forming a cross-bridge
- Myosin head tilts backwards causing the thin filament to slide past the myosin filament. (The power stroke) During power stroke ADP is released from myosin head
- After power stroke, a new ATP molecule attaches to the myosin head, breaking the cross-bridge
- Myosin head returns to returns to original position as ATP is hydrolysed. The Myosin head can now make a new cross-bridge further along the actin filament
There is a huge demand for ATP in muscle due to the millions of Myosin. ATP must be regenerated quickly to allow continued contraction. What are the three mechanisms involved in maintaining the supply of ATP?
- Aerobic respiration in mitochondria
- Anaerobic respiration in the sarcoplasm of muscle tissue
- Creatine Phosphate in the sarcoplasm acts as a reserve store of phosphate molecules
(The Phosphate can be transferred from the Creatine Phosphate to ADP molecules, creating ATP v. rapidly)
What are Gibberellins?
Plant hormones responsible for control of stem elongation and seed germination
What are Auxins?
Plant hormones responsible for regulating plant growth
What are Cytokinins?
Plant hormones that promote bud growth
What does Abscisic acid do?
Inhibits bud growth
Name 2 commercial uses of Cytokinins
- In tissue culture to help mass-produce plants
- Promote bud and shoot growth, separate into smaller individual plant, and grown separately
Name 2 commercial uses of Gibberellins
- Delay citrus fruit senescence, extending time it can be left unpicked, extending availability in shops
- Causes sugar cane elongation, and sugar cells are stored in the internodes, which are made longer
Name 2 comercial uses of Ethene
- Speeding up fruit ripening e.g. in apples
- Promoting fruit drop e.g. in Cherries
