Animal and Plant Responses 5.1.5 Flashcards
What is the function of the CNS and PNS?
-The central nervous system receive and process information and coordinate the body’s response
-The Peripheral Nervous system consists of neurones that carry action potentials to and from the CNS
What is the role of the autonomic nervous system and the somatic nervous system?
-Autonomic nervous system: controls the involuntary activities of glands, smooth muscle, and cardiac muscle, it works under subconscious control
-Somatic nervous system: controls the voluntary activities of body muscles and is under conscious control
What are the two parts of the autonomic nervous system and what do they do?
-The sympathetic and parasympathetic nervous systems
-If the outcome is increasing activity then it involves the sympathetic nervous system
-If the outcome is decreasing activity then it involves the parasympathetic nervous system
What neurones make up most of the brain?
-Most of the brain contains relay neurones which are non-myelinated (makes them look grey)
What are the functions of the Cerebrum and the Cerebellum?
-Cerebrum: controls voluntary action like learning, memory, personality and conscious thought
-Cerebellum: controls unconscious functions like posture, balance and non-voluntary movement, if a persons cerebellum is damaged they may suffer from jerky movement
What are the functions of the Medulla Oblongata, Hypothalamus and Pituitary gland?
-Medulla Oblongata: used in autonomic control e.g. control of heart rate
-Hypothalamus: regulatory centre for temperature and water balance
-Pituitary gland: stores and releases hormones that regulate body functions
What is the structure of the cerebrum?
-Split into two hemispheres connected by corpus callosum, the left side of the brain controls effectors on the right side of the body vice versa.
-The outer layer is thin and highly folded (cerebral cortex)
What parts of the body will the cerebellum receive sensory information from?
-Retina
-Balance organs in inner ear
-Spindle fibres in muscles
What is the structure of the pituitary gland?
Consists of two lobes:
-Posterior lobe: linked to the hypothalamus by specialized neurosecretory cells e.g ADH
-Anterior lobe: produces its own hormones which are released in response to factors produced by hypothalamus
What is the structure of the hypothalamus?
-The hypothalamus contains sensory receptors
-It has two centres- one for parasympathetic and sympathetic nervous system
What is the structure of the Medulla Oblongata?
-It controls the non-skeletal muscles by sending action potentials through the autonomic nervous system
-Contains three centres (cardiac centre: regulates heart rate, vasomotor centre: regulates blood circulation and pressure and respiratory centre: regulates rate and depth of breathing)
What is a reflex action?
-When the body responds to a stimulus without making a conscious decision to respond, as the pathway of communication does not involve the conscious part of the brain
-It is involuntary and they are protective to help the organism avoid damage
What stimuli can cause blinking?
-Sudden movement close to the eye
-A foreign object touching the eye
-Bright light
-Loud sounds
How can the blinking reflex be overridden?
-The reflex can be consciously overridden when a relay neuron is involved with inhibitory signals, allowing the person to touch their eye.
What is the purpose of the knee-jerk reflex and the stimulus?
-It is used to help maintain posture and balance by causing the lower leg to straighten rapidly
-The stimulus is when the patella tendon is depressed which causes the quadricep muscle to be stretched
What physiological responses occur during the fight or flight response?
-Glycogenolysis: breakdown of glycogen–> glucose
-Increased heart rate
-Increased breathing and wider airways
-Dilated pupils
What receptors are involved in detecting a threat and what part of the brain receives this sensory input?
-External receptors(eyes, ears and nose) and internal receptors (pain and blood pressure)
-The cerebellum receives this sensory input
What does the hypothalamus do in the flight or fight response process?
-The hypothalamus releases two hormones TRH and CRH
-CRH causes the release of ACTH from the pituitary gland which causes the adrenal cortex to release glucocorticoids, which regulates the metabolism of carbohydrates (increasing gluconeogenesis)
-TRH causes the release of TSH which stimulates the thyroid gland to release more thyroxine which increases metabolic rate
What does the adrenal cortex do in the flight or fight response process?
-The adrenal cortex also releases mineralocorticoids which increase blood volume and pressure by increasing the uptake of sodium ions and water by the kidney
What does the sympathetic nervous system do in the fight or flight response process?
-It activates the release of adrenaline from the adrenal medulla.
-Both the SNS and adrenaline cause heart rate and force to increase, bronchioles relax causing airways to widen, intercostal muscles of diaphragm contract faster, glycogenolysis, vessels supplying heart and muscles dilate and constrict for digestive system.
What are the effects of prolonged exposure to stress?
-Prolonged high blood pressure and high blood sugar can lead to diabetes and CVD
-Suppression of immune system can lead to disease
How is the cardiac cycle controlled and how is heart rate increased and decreased?
-It is controlled by the autonomic nervous system, the medulla oblongata is linked to SAN in the heart by motor neurons
-If the heart rate needs to be increased action potentials pass along the sympathetic nerve causing the release of noradrenaline at the SAN
-If the heart rate needs to be decreased action potentials pass along the parasympathetic nervous system causing acetylcholine to be released
What are Baroreceptors?
-They are pressure receptors that detect changes in blood pressure in the aorta, vena cava and carotid arteries. For example when blood pressure is low heart rate needs to be increased to prevent failing
What are chemoreceptors?
-Chemical receptors that monitor changes in carbon dioxide and oxygen in the aorta, carotid arteries and medulla
What happens to the PH of blood when carbon dioxide increases and why? and how is most carbon dioxide transported?
-The PH lowers as carbon dioxide reacts with water to form carbonic acid which is acidic
-Most carbon dioxide is transported as hydrogen carbonate ions, carbonic acid also dissociates to release hydrogen ions
What is the effect of hydrogen ions and carbonic acid on red blood cells?
-The H+ affects the PH of the cytoplasm in the red blood cells, which alters its shape affecting its affinity for oxygen
-Both the H+ and carbonic acid can react with hemoglobin making compounds unable to combine with oxygen
How is the heart rate controlled when there is high blood pressure?
- Baroreceptors detect high blood pressure and send impulse to CVC which sends impulses along parasympathetic neurons.
2.This causes the secretion of acetylcholine which binds to receptors on SAN
3.Heart rate slows down and blood pressure reduces
How is the heart rate controlled when there is Low blood pressure?
1.Baroreceptors detect the low blood pressure and send impulses along the sensory neurones to the CVC which send impulses along the sympathetic neurones
2.This causes the secretion of noradrenaline which binds to receptors on the SAN
3. Heart rate increases and blood pressure increases back to normal
How is heart rate controlled when there is high oxygen concentration in blood, low carbon dioxide concentration in blood or high blood PH levels?
1.Chemoreceptors detect the chemicalchanges and send impulses along sensory neurone to CVC which send impulses along parasympathetic neurones.
2.This causes the secretion of acetylcholine which binds to receptors on SAN
3.This causes heart rate to decrease and levels to return to normal
How is heart rate controlled when there is low oxygen concentration, high carbon dioxide concentration or low blood pH?
1.Changes are detected by chemoreceptors which send impulses along sensory neurone to CVC which send impulses along sympathetic neurone
2. These secrete noradrenaline which bind to receptors on SAN
3.This causes heart rate to increase and levels return to normal
Why and how does moving limbs cause an increase in heart rate
1.Stretch receptor in muscles detect movement of limbs
2. They send action potentials to the CVC in the medulla oblingata which cause an increase in heart rate (via the sympathetic neurone)
Define tropism?
-a phenomenon indicating the growth or turning movement of an organism, usually in response to an environmental stimulus
What are the different types of muscles?
-Involuntary muscle(Smooth muscle)
-Cardiac muscles
-Skeletal muscles(voluntary muscles)
What is the sarcolemma and the sarcoplasmic reticulumn?
-Sarcolemma: plasma membrane enclosing muscle fibres, parts of it fold inwards (T tubules) their role is to spread electrical impulses so that the whole fibre receives the impulse and contracts simultaneosly
-Sarcoplasmic reticulumn: modified endoplasmic reticulumn that supplies muscle fibres with calcium ions for muscle contraction
What are myofibrils?
-They are contractile units responsible for contraction of skeletal muscles
What are the two protein myofilaments that make up myofibrils?
-Actin: thinner filament
-Myosin: thicker filament
What are sacromeres?
-The smallest contractile unit of a muscle, they are arranged end to end along the length of the myofibril
Draw the structure of the sarcomere?
What parts of the myofibril change size during contraction and relaxation (sarcomere,A-band,I-band,H-zone and Z-line)?
What is a neuromuscular junction?
-Neuromuscular junction: the point at which a motor neurone and skeletal muscle fibre meet
-Small forces only require a few motor units to be stimulated whereas large forces require many motor units to be stimulated
What is the structure of myosin?
-A single myosin molecule consists of two intertwined polypeptide chains, with globular heads that can move back and forth
-Each head is a binding site for actin and ATP
What is the structure of actin?
-Made of two chains of actin monomers joined together, they have binding sites for myosin which are often blocked by another protein called tropomyosin held in place by troponin. (This is in its relaxed state)
Describe the Sliding filament theory?
- Tropomyosin is blocking actin binding sites
- Ca²⁺ released from sarcoplasmic reticulum bind to troponin changing tropomyosin’s shape and exposing binding sites, myosin heads are now able to bind
- Myosin head changes shape as a result of binding to actin filament and pulls the filaments and ADP and Pᵢ are released
- ATP can now bind to the myosin head causing it to release from the actin
- ATP breaks down into ATP and Pᵢ and the cycle is able to repeat
What are abiotic factors and abiotic stresses that plants respond to?
-Components in an ecosystem that are non-living
-Abiotic stresses that plants respond to:
=> Closing stomata in response to draught
=> High temperatures lead to thicker layer of wax on leaf
How do plants respond to the threat of herbivores?
-They produce chemicals in defence e.g Tannins, Alkoids, Terpenoids and Pheromones
What is the role of auxins, gibberellins and ethene?
-Auxins: Cell elongation and prevents leaf abscission
-Gibberellins: stimulate amylase which breaks down starch releasing glucose for respiration
-Ethene: promotes fruit ripening and leaf abscission (leaf fall)
What is the role of ABA(abscisic acid) and describe its effect on the membrane of a guard cell and what this does to the stomata?
-ABA inhibits seed germination and causes stomatal closure when the plant is stressed by low water availability
1.Abscisic acid binds to ABA receptors on the guard cell surface membrane and this causes calcium ions to enter the cell
2. This causes potassium ions to leave the cell and water follows by osmosis making the guard cell turgid and closing the stomata
What do the terms synergism and antagonism refer to in terms of plant hormones?
-Synergism: plant hormone that increases the effect of another
-Antagonism: plant hormone that reduces the effect of another
How do plants prevent freezing?
-If cells freeze their membranes are disrupted and they die
-The cytoplasm and sap contain solutes which lower the freezing point
Describe the process of a leaf abscission?
- The part of the stem that breaks is called the abscission zone, leaf abscission is normally inhibited by auxins
- The abscission zone is made up of an abscission layer and protective layer
- As leaves age auxin production is reduced and ethene increased which makes the cells in the abscission zone more sensitive to ethene
- Ethene increases the production of cellulase which digests the cell walls in the abscission zone causing the leaf to fall
What is the difference between two plants grown in all round light but one plants has low-light conditions and the other has bright light?
-Bright light plant: grow straight upwards
-Low-light plant: still grows straight upwards but will grow taller in a short space of time compared to the bright even light
What are auxins?
-Stimulants that are continuously made in the shoot apexes of plants, the primary auxin is IAA and is involved in cell elongation and phototropism
-They can move by diffusion or be transported by the phloem
How was it discovered that auxins where in the plant tip and was chemical?
-Plants was placed by a lamp on one side
1. When the tip was cut or covered the plant didnt respond suggesting the root tip must detect the light stimulus
2. A mica plate(conducts electricity) was inserted on the side of the tip that the light was on and plant grew towards the light, however when it was inserted on the other side the plant didn’t respond suggesting the chemical signal was on the shade side
3. Shoot tip was cut and replaced with a block of gelatin (conducts chemical not electrical) and the plant still responded suggesting the signal was chemical
Describe apical dominance?
-Apical dominance: growth of the main central stem of the plant with a reduced production of lateral shoots and branches, this is controlled by auxins
What is evidence to support the role of gibberellin in stem elongation?
-Applying gibberellic acid to varieties of plants causes them to grow taller
-Taller plants have a higher concentration of gibberellic acid
-When plants have a mutation which blocks gibberellin production they usually only grow around 1cm tall
