5.1.5 Plant And Animal Responses

Question 1

State the different neurones located in the central and periphel nervous system

Answer 1

PNS- sensory and motor neurones

CNS- mostly made up of relay neurones

Question 2

State the role of rhe sympathetic nervous system

Answer 2

Activates what is termed as ‘fight or flight’ response

Prepares the body for activity and stimulates effectors

Question 3

Describe how the sympathetic nervous system act in balance with each other at times of rest and at times of stress

Answer 3

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

Question 4

State the function of the medulla oblongatta

Answer 4

Resposnible for controlling involountary/autonomic functions such as heart rate

Question 5

State one function of the pituitary gland

Answer 5

Stores and releases hormones that regulate homeostatic mechanisms such as thermoregulation or osmoregulation

Question 6

State 2 processes dontrolled by the hypothalamus

Answer 6

Minitoring composition of blood plasma and hormone production

Question 7

Describe the structure and function of the cerebrum

Answer 7

Carries out higher volountary brain function such as langauge
Divided into 2 hemispheres, outer layer is ther cerebal cortex

Question 8

Describe the steps in a stimulus response reflex arc

Answer 8

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

Question 9

Describe how the knee jerk response is generated after a tap on the knee

Answer 9

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

Question 10

What is meant by a reflex action, give examples

Answer 10

Blinking and knee jerk

Reflex action is involounatry and innate, stimulus always produces the same response

Question 11

Describe the steps in a spinal cord based stimulus response reflex arc

Answer 11

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

Question 12

Explain the cordination that occurs between nervous and endocrine systems of the body during fight or flight

Answer 12

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

Question 13

TSH is a protein bases hormone. How would TSH stimulate production of thyroxine at the thyroid gland

Answer 13

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

Question 14

Describe what is meant by a ‘second messenger molecule’

Answer 14

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

Question 15

How does the medulla oblongata change frequency of heart rate

Answer 15

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

Question 16

Describe the basic structure of mammalian skeletal muscle

Answer 16

Many myofribils

Myofribils made up of many repeating units called sacromeres

Question 17

Explain how the structure of cardiac muscle is related to its function

Answer 17

Arranged as long fibres that branch to form cross bridges

Branching allows electrical stimulations to spread evenly allows a saueezing contraction > one dimensional contraction

Question 18

Describe 2 similarities and 2 differences between neuromuscular junction and a synapse

Answer 18

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

Question 19

Describe how actin and myosin are arranged in resting mucle

Answer 19

Not interlocked

Wide I bands present and visible H zones

Question 20

Describe the role of calcium ions in muscle contraction (tropomyosin)

Answer 20

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

Question 21

What happens during contraction in the sacromere

Answer 21

Z line move closer together
I band and H zone get narrowee
A band remains the same

Question 22

Describe 2 similarities in the action of plant and animal hormones in cell signalling

Answer 22

hormone bind to receptor

may have affect on more than one target tissue

Question 23

Outline the difference between motor neurone in the somatic and autonomic nervous system

Answer 23

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

Question 24

Explain how different neurotransmitters in the autonomic nervous system cause antagonism

Answer 24

Neurones in the parasympathetic nervous system use acetylcholine as a neurotransmitter which has inhibitory effects
SNS uses noradrenaline which has stimulatory effects

Question 25

Describe how adrenaline acts within a secondary messenger model

Answer 25

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

Question 26

How does medulla oblongata control heart rate during exercise

Answer 26

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

Question 27

Explain why a toxin that prevent the release of acetylcholine at neuromuscular junction can be fatal

Answer 27

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

Question 28

Simplify the process of the sliding filament model

Answer 28

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

Question 29

Outline the organisation of the mammalian nervous system

Answer 29

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

Question 30

Outline the structure and function of the brain

Answer 30

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

Question 31

Outline the receptors which affects heart rate and the response for high and low pressures

Answer 31

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

Question 32

Outline features of the skeletal,involuntary and cardiac

Answer 32

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

Question 33

Explain the structure of skeletal muscle fibre with more detail

Answer 33

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

Question 34

Describe the features of myofibrils

Answer 34

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

Question 35

What happens to sarcomeres during muscle contraction

Answer 35

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

Question 36

What are the structures within myofilaments

Answer 36

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

Question 37

What occurs during the binding sites in resting muscles

Answer 37

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

Question 38

Outline the stages at a neuromuscular junction

Answer 38

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

Question 39

Outline the stages of muscle contraction at the sarcoplasm

Answer 39

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

Question 40

What happens at the neuromuscular junction after contraction

Answer 40

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

Question 41

Explain the sliding filament model (sarcolemma, calcium ion, ATPase,troponin)

Answer 41

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

Question 42

Explain the sliding filament model when excitation stops

Answer 42

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

Question 43

How does Abscisic acid able to trigger stomatal closure

Answer 43

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

Question 44

How does ethene stimulate leaf loss

Answer 44

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

Question 45

Explain why glucose is required for contraction of skeletal muscle

Answer 45

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

Question 46

How does TTX (neurotoxin) effect the activity of neurones

Answer 46

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

Question 47

Why is transmission of action potentials along the axon slower in the absence of saltatory conduction

Answer 47

No nodes of ranvier, whole axon needs to be depolarised

Question 48

Explain the advantages of response of an object moving towards the eye

Answer 48

Rapid blinking/shutting and closing of eye

Involuntary, prevents damage to object entering eyes