Responding To The Environment Flashcards
What causes leaf loss in deciduous plants?
Ethene is produced by ageing leaves. As the leaf gets older more ethane is produced and a layer of cells called the abscission layer develops at the bottom of the leaf stalk and this separates the leaf from the rest of the plant. Ethene causes the cells in the abscission layer to expand, breaking the cell walls so the leaf falls off.
What is a tropism?
A directional growth response of a plant to a stimulus
How can plant hormones be used commercially?
Ethane stimulates enzymes that break down cell walls, break down chlorophyll and convert starch to sugars. This makes fruit soft, ripe and ready to eat.
Auxins and gibberellins are sprayed onto unpollinated flowers to make them develop fruit without fertilisation.
Auxins can help farmers to make sure all fruit drops off plants at the same time, meaning collection is easier.
What is the structure of the nervous system?
The nervous system consists of the central nervous system (the brain and spinal cord) and the peripheral nervous system (the neurones connecting the CNS to the rest of the body). The peripheral nervous system has two different systems: the somatic nervous system, which controls conscious activities; and the autonomic nervous system which controls unconscious activities such as digestion and heart rate. The autonomic nervous system consists of the sympathetic nervous system and the parasympathetic nervous system.
What effects does the parasympathetic nervous system have on organs?
The parasympathetic nervous system is most active in sleep and relaxation.
It causes heart rate to decrease and the force of each heart contraction to decrease. Pupils constrict, digestive enzymes are secreted so digestion happens. The parasympathetic nervous system is responsible for sexual arousal
What is the fight or flight response?
The fight or flight response is coordinated by the nervous and hormonal systems. The sympathetic nervous system is activated, which also triggers the release of adrenaline. These, combined, have the following effects:
Heart rate and stroke volume are increased
Muscles around the bronchioles relax so airways widen
Intercostal muscles and diaphragm also contract faster and with more strength, so rate and depth of breathing increases.
Glycogen is converted into glucose, so more glucose is available for muscles to respire.
Blood flow is diverted from the skin and gut to the heart, lungs and skeletal muscles, readying them for action.
What is the function of the cerebrum?
The cerebrum is responsible for the higher brain functions, including conscious thought, learning, the ability to override some reflexes, reasoning and judgement, as well as being involved with vision and hearing
What is the hypothalamus responsible for?
Controlling most of the body’s homeostatic mechanisms including maintaining temperature and blood water potential. It also produces hormones that control the pituitary gland
What does the medulla oblongata do?
It controls breathing rate and heart rate, as well as non skeletal muscles
What does the cerebellum do?
It is important for muscle coordination, posture and coordination of balance, as well as fine control of muscular movements, such as when walking or driving a car
What is the role of the brain and nervous system in the coordination of muscular movement?
The CNS coordinates muscular movement, as it recieves sensory information and decides what kind of response is needed. If the response needed is movement then the CNS will send impulses along motor neurones to tell skeletal muscles to contract. Skeletal muscle (striated muscle) is the type of muscle you use to move.
How are skeletal muscles attached to bones?
By tendons
How are bones attached to other bones?
Using ligaments
Why do muscles work in pairs?
Muscles are only capable of producing a force when they contract so the movement of any bone at a joint requires the coordinated action of at least two muscles. Muscles working in pairs opposite each other are described as antagonistic
What type of joint is the elbow?
A synovial joint
What does synovial fluid in the elbow joint do?
It acts as a lubricant to ease the movement of bones at the joint.
What muscles are used for bending your arm at the elbow?
Your biceps contract and the triceps relax
What muscles are used when straightening your arm at the elbow?
Your triceps contract and biceps relax
What is a neuromuscular junction?
A neuromuscular junction is very similar to a synapse, but they are found between motor neurones and muscle cells not between two neurones.
What are the differences between neuromuscular junctions and synapses?
Neuromuscular junctions always use acetylcholine as a neurotransmitter, whereas synapses use various neurotransmitters. Neuromuscular junctions have more postsynaptic receptors than synapses. When the neurotransmitter binds to the postsynaptic receptors in a neuromuscular junction, muscle cells always contract, whereas an action potential may not be fired in a synapse. In neuromuscular junctions the neurotransmitter is always broken down by acetylcholinesterase, whereas the neurotransmitters used in synapses can be broken down in various ways, depending on the neurotransmitter.
What is skeletal muscle made up of?
Large bundles of long cells, called muscle fibres.
What is the structure of muscle fibres?
The cell membrane of muscle fibres is called the sarcolemma. Bits of the sarcolemma fold inwards across the muscle fibre and stick into the sarcoplasm. This helps to spread electrical impulses throughout the sarcoplasm so they reach all of the muscle fibre.
A network of internal membranes called the sarcoplasmic reticulum runs through the sarcoplasm. The sarcoplasmic reticulum stores and releases calcium ions that are needed for muscle contraction. Muscle fibres have lots of mitochondria to provide ATP for muscle contraction. They are multinucleate and have lots of long, cylindrical organelles called myofibrils. Myofibrils are made up of proteins and are highly specialised for contraction.
