5.1.5 Plant And Animal Responses Flashcards
State the different neurones located in the central and periphel nervous system
PNS- sensory and motor neurones
CNS- mostly made up of relay neurones
State the role of rhe sympathetic nervous system
Activates what is termed as ‘fight or flight’ response
Prepares the body for activity and stimulates effectors
Describe how the sympathetic nervous system act in balance with each other at times of rest and at times of stress
work antagonistically
Any given time both systems will be active
Times of stress: SNS sends more signals than the PNS
Rest: parasympathetic ns sends more signalsa than SNS
State the function of the medulla oblongatta
Resposnible for controlling involountary/autonomic functions such as heart rate
State one function of the pituitary gland
Stores and releases hormones that regulate homeostatic mechanisms such as thermoregulation or osmoregulation
State 2 processes dontrolled by the hypothalamus
Minitoring composition of blood plasma and hormone production
Describe the structure and function of the cerebrum
Carries out higher volountary brain function such as langauge
Divided into 2 hemispheres, outer layer is ther cerebal cortex
Describe the steps in a stimulus response reflex arc
Receptor detect stimulus, receptor creates an impulse,passed through a sensory neurone, impulse passes to the spinal cord and move through a co ordinator OR relay neurone to a motor neurone
Impulse moves to an effector/ muscle gland
Describe how the knee jerk response is generated after a tap on the knee
Spinal reflex, nervous pathway passes through the spinal cord rather than the brain
When knee is tapped, muscle spindles detect stretch of thigh muscles, sensory neurone to spinal cord, passed onto a motor neurone, contraction of quadriceps
What is meant by a reflex action, give examples
Blinking and knee jerk
Reflex action is involounatry and innate, stimulus always produces the same response
Describe the steps in a spinal cord based stimulus response reflex arc
Receptor detects stimulus, creates an impulse which is passes through the sensory neurone, impulse moves through a sensory neurone to a relay neurone and through a motor neurone. Signal from the spinal cord to an effector. Effector brings appripoate response
Explain the cordination that occurs between nervous and endocrine systems of the body during fight or flight
Threat detected by the autonomic nervous system, the hypothalamus communicates with the sympathetic nervous system and the adrenal cortical system.
SNS sends out impulses to glands and smooth muscles and tells the adrenal medulla to release adrenaline and noradrenaline into the blood stream
TSH is a protein bases hormone. How would TSH stimulate production of thyroxine at the thyroid gland
Peptide hormones are charged and cannot cross the lipid bilayer of the cells of the thyroid gland. TSH will bind to receptors on the surface of the cells of the gland. Trigger a series of membrane bound reactions, which form a second messanger inside the cell. SM will activate variuos enzymes and proteins within the cell
Describe what is meant by a ‘second messenger molecule’
Signalling molecule inside a cell that is activated by a hormone binding to the outside of the cell, which stimulates a changw in the activity of the cell
How does the medulla oblongata change frequency of heart rate
One centre increases HR by sending impulses through the sympathetic nervous system, transmitted by the accelerator nerve
One centre decreases HR by sending impulses through the parasympathetic nervous system , transmitted by the vagus nerve
Controls the frequency of impulses to SAN
Describe the basic structure of mammalian skeletal muscle
Many myofribils
Myofribils made up of many repeating units called sacromeres
Explain how the structure of cardiac muscle is related to its function
Arranged as long fibres that branch to form cross bridges
Branching allows electrical stimulations to spread evenly allows a saueezing contraction > one dimensional contraction
Describe 2 similarities and 2 differences between neuromuscular junction and a synapse
Neurotransmitters both travel across the synapse and NM by diffusion, both have receptors that are stimulated when bound with a specfic neurotransmiter, influx of sodium ions
NM only ever excitatory, stimulating a muscle contract only ever between a motor neurone/myofribrils
Synapses- can be excitatory or inhibitory, between two neurones or a neurone and any effector
Describe how actin and myosin are arranged in resting mucle
Not interlocked
Wide I bands present and visible H zones
Describe the role of calcium ions in muscle contraction (tropomyosin)
CA2+ uncovers the binding site on actin by binding to troponin, moving tropomyosin. Allows myosin heads to attach to actin filaments. A and myosin filaments slide so that the actin filaments are closer togther, shortening the sacromere. ATP binds to the head,hydrolysis releases energy changes the mysoin head, release from the actin
What happens during contraction in the sacromere
Z line move closer together
I band and H zone get narrowee
A band remains the same
Describe 2 similarities in the action of plant and animal hormones in cell signalling
hormone bind to receptor
may have affect on more than one target tissue
Outline the difference between motor neurone in the somatic and autonomic nervous system
Motor neurones in the SNS carry impulses to effectors in the skeletal muscles
Motor neurones in the ANS carry impulses to glands and muscles in the gut and heart
Explain how different neurotransmitters in the autonomic nervous system cause antagonism
Neurones in the parasympathetic nervous system use acetylcholine as a neurotransmitter which has inhibitory effects
SNS uses noradrenaline which has stimulatory effects
Describe how adrenaline acts within a secondary messenger model
Adrenaline binds to a receptor on a target cell to form adrenaline receptor complex, activates enzyme adenyl cyclase, causes production of cAMP from ATP,cyclic AMP acts as a secondary messenger molecule, activates further enzymes involved in glucose regulation
How does medulla oblongata control heart rate during exercise
Medulla oblongata receives signals from the chemoreceptors located in the carotid and aortic bodies
Detect CO2 in the blood
During exercise the increase in CO2 triggers the medulla oblongata to send signals down the sympathetic nerve to the SAN to increase heart beat
Explain why a toxin that prevent the release of acetylcholine at neuromuscular junction can be fatal
Acetylcholine is a neurotransmitter, if it is prevented, nerve impulses could not cross synapses
Skeletal muscles such as diaphragm would not contract and breathing would stop
Cardiac muscle would not be able to contract,which would cause the heart to stop beating
Simplify the process of the sliding filament model
Acetylcholine released from NM junction triggers calcium ions to be released within the sarcoplasm of MC
Ions alter the tropomyosin wrapped around the actin filament - reveals the binding sites on filaments
Myosin head attach to binding sites, forming actinmyosin cross bridges, once attached, head change angle and slide the filaments past each other
ATP attaches to the heads and causes them to detach and return normal position. Creatine phosphate provides phosphorus to maintain ATP supply
Outline the organisation of the mammalian nervous system
Split into CNS- brain and spinal cord - peripheral nervous system - neurones that connect to the CNS to the rest of the body-.
Peripheral split into - somatic NS: conscious activities, autonomic NS- unconscious activities e.g digestion
Autonomic split into two divisions - sympathetic - ‘fight or flight’,sympathetic neurones release noradrenaline
Parasympathetic - ‘rest and digest’, parasympathetic neruones release acetylcholine
Outline the structure and function of the brain
Cerebrum - divided in 2 cerebral hemispheres joined by corpus callosum, controls voluntary actions, learning memory, personality, conscious thought
Cerebellum - controls unconscious functions,muscle coordination, posture
Medulla oblongata - autonomic control,HR and BR
Hypothalamus - main controlling region for the autonomic nervous system, regulatory centre for temp and water balance,endocrine gland
Pituitary gland - anterior - 6 hormones including FSH,Posterior - stores and release hormones incl ADH,stores and release hormones, stimulates other glands
Outline the receptors which affects heart rate and the response for high and low pressures
Baroreceptors - pressure receptors, detect changes in blood pressure, present in aorta, vena cava,carotid arteries
Chemoreceptors - chemical receptors, detect change in o2 level,CO2 and pH of blood, present in aorta, carotid artery,medulla
HR- electrical impulses from receptors sent to medulla via sensory neurones, medulla process information, send impulses to SAN along motor neurones (accelerator and vagus nerve)
HBP- baroreceptors detect high blood pressure, impulse sent to medulla via sensory neurone, medulla to SAN via vagus nerve, acetylcholine secreted binds to SAN, cardiac muscles decreases
LBP- baroreceptors detect low BP,impulse sent to medulla via sensory neurone,medulla to SAN via accelerator nerve, noradrenaline secreted binds to receptors on SAN,increase blood pressure
Outline features of the skeletal,involuntary and cardiac
Skeletal - Responsible for movement,contraction controlled consciously, consist of many muscle fibres that are multi nucleated, stripped pattern, muscles contract in one direction
Involuntary - contraction controlled involuntarily, muscle fibres are spindle shaped and uniculeated,contract in different directions, e.g walls of hallow organs
Cardiac - involuntarily, myogenic, many muscle fibres, uninucleated, faint striated appearance, interconnect, do not fatigue
Explain the structure of skeletal muscle fibre with more detail
Sarcolemma - muscle membrane
T tubles are parts of the sarcolemma that fold inwards, help spread electrical throughout the sarcoplasm
Sarcoplasmic reticulum run throughout the sarcoplasm, store and release ca2+ ions for muscle contraction
Lots of mitochondria
Myfobrils
Describe the features of myofibrils
Consist of thick and thin myofilaments, THICK- myosin, THIN- actin
Dark bands - thick myosin filaments, some overlapping actin filaments, A bands
Light bands - contain actin filaments, I bands
Myofibrils consist of short units called sarcomeres
Z line- end of sarcomere
M line - middle of myosin filaments
Around M - line is the H zone - contains only myosin filaments
What happens to sarcomeres during muscle contraction
Myosin and actin filaments slide over one another to cause sarcomeres to contract, myofilaments don’t contract themselves A bands stay the same length I band gets shorter H zone gets shorter Sarcomeres get shorter
What are the structures within myofilaments
Globular head that are hinged, can move back and forth
Each myosin head has a binding site for actin and binding site for ATP
Actin filaments have binding site for myosin heads, actin myosin binding sites
2 other proteins, tropomysoin and troponin found between each actin filaments
Proteins are attached to each other,help myofilaments move past each other
What occurs during the binding sites in resting muscles
Actin myosin binding site is blocked by tropomyosin, held in place by troponin
Means that myofilaments can’t slide past each other because myosin heads can’t bind to the actin myosin binding sites on the actin filaments
Outline the stages at a neuromuscular junction
AP arrives at the presynaptic knob , voltage gated calcium ion channels open,influx of Ca2+ diffuse into the knob, synaptic vesicles containing acetylcholine move towards and fuse w the presynaptic membrane,acetylcholine is released into the NM junction by exocytosis,Ach binds to receptors on the sarcolemma , sodium ion channels open, influx of Na+ diffuse inside the muscle fibres, depolarisation of the sarcolemma, AP spreads along sarcolemma
Outline the stages of muscle contraction at the sarcoplasm
Depolarisation of sarcolemma travels down T Tubules, sarcoplasmic reticulum is polarised and voltage gated calcium ion channels on the SR open, Ca2+ diffuse out of the sarcoplasmic reticulum into the sarcoplasm, ca2+ bind to troponin causing it to change shape, tropomyosin moves away to expose actin -myosin bringing sites on the actin filaments, myosin head binds and filaments slide, muscle contraction
What happens at the neuromuscular junction after contraction
Acetylcholine unwinds from receptors; broken down by acetylcholinesterase - prevents muscle from being overstimulated
Sodium ions diffuse out of muscle fibres via special transporters
Calcium ions are actively transported into sarcoplasmic reticulum once the sarcolemma, T tubules and sarcoplasmic reticulum are no longer polarised, movement of Ca2+ ions terminates muscle contraction
Explain the sliding filament model (sarcolemma, calcium ion, ATPase,troponin)
AP from motor neurone stimulates muscle cell
Sarcolemma depolarised
Depolarisation spreads down T Tubules to the sarcoplasmic reticulum
Voltage gated calcium ion channels open on the SR
Stored calcium ions diffuse into the sarcoplasm
Calcium ion binds to troponin, causing it to change shape
Tropomyosin moves away, exposing actin-myosin binding sites on the actin filament,
Myosin heads bind to binding site,actin myosin cross bridge forms
Calcium ion also activates enzyme ATPase, breaks down ATP to ADP and Pi,energy released
Provides energy for muscle contraction
Energy released from ATP moves the myosin head, which pulls the actin filament along with it
ATP provides energy to break actin myosin cross bridge,myosin head detaches after actin filament is Moved
Myosin head attaches to a different binding site further along the actin filament new acting motion Crossbridge forms , cycle is repeated, sarcomere shortens causing the muscles to contract the cycle continues as long as calcium ions are present and bound to troponin molecules,actin myosin binding sites exposed
Explain the sliding filament model when excitation stops
Calcium ions leave binding site on troponin molecules
Calcium ions are actively transported into the sarcoplasmic reticulum
Troponin molecules return to original shape, pulling attached tropomyosin molecules along with them
Actin myosin binding sites are now blocked again and myosin heads can no longer bind to them
Muscles relaxes
Actin filaments slide back to their original positions
Sarcomere lengthen
How does Abscisic acid able to trigger stomatal closure
ABA binds to receptors on the guard cell membrane - specific ion channels open,allows calcium ions to enter the cytosol from vacuole
2) increased concentration of calcium ions in the cytosol causes other ion channels to open, allows ions to leave guard cells
3) water leaves the guard cells via osmosis
4) guard cells become flaccid and stomata close
How does ethene stimulate leaf loss
Ethene produced by ageing leaves, more older ethene is produced
- a layer of cells called the abscission layer develops at the bottoms of the lead stalk where the leaf joins the stem, this layer separates lead from the rest of the plant
- ethene stimulates the cells in the abscission layer to expand and breaking the cells wall and causing lead to fall off
Explain why glucose is required for contraction of skeletal muscle
Glucose is used as a respiratory substrate to produce ATP
ATP needed in muscle contraction for breaking cross bridges between myosin and actin
ATP for active transport of calcium ions back into the sarcoplasmic reticulum
How does TTX (neurotoxin) effect the activity of neurones
Sodium ions cannot enter, prevents depolarisation of membrane, remains at resting potential, prevents action potential being generated, impulse not conducted, so no release of neurotransmitter
Why is transmission of action potentials along the axon slower in the absence of saltatory conduction
No nodes of ranvier, whole axon needs to be depolarised
Explain the advantages of response of an object moving towards the eye
Rapid blinking/shutting and closing of eye
Involuntary, prevents damage to object entering eyes
