Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology A Level > Survival And Response > Flashcards

Survival And Response Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Autonomic nervous system is made up of

A

Motor neurone which carry impulses to the involuntary muscles ( muscles which we generally have no conscious control)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Two branches of the autonomic nervous system

5

A

Sympathetic and parasympathetic

They are antagonistic so they work in opposition

Normal circumstances= impulses travel simultaneously at a low rate

In times of stress= rate of impulses increases in sympathetic branch

In times of relaxation= rate of impulses is higher in parasympathetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The human heart pumps bloood around the body. The blood supplies…. and removes
4

A

Oxygen and nutrients such as glucose, amino acids and fatty acids

Waste products such as carbon dioxide and urea

The heart must be able to vary its output to suit the body’s level of activity

Heart output can be altered by changing the number of heart beats per minute, the stroke volumes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Myogenic

2

A

Generates its own impulsees with a regular ‘rhythm’

Heart muscle is myogenic and does not require impulses from the nervous system to initiate electrical impulses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

SAN

3

A

Sino atrial node

Natural pacemaker

Located in the wall of the right atrium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Control of heart beat

5

A
  1. SAN initiates a wave of excitement
  2. This spreads over the walls of the atria causing them to contract - atrial systole
  3. The impulses reach the atrioventricular node. Delayed to allow complete contraction of atria before ventricles start to contract
  4. The wave of excitement then travels down highly conductive tissue int the septum called the bundle of his —> purkyne tissue. It reaches the bottom of ventricles and causes them to contract upwards. Ventricular systole
  5. Heart then goes into a period of relaxation called diastole
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Modifying the heartbeat

A

Rate at which heart beats is modified by nerve impulses from the cardiovascular centre in the medulla oblongata of the brain

2 centres concerned with heart rate, nerve fibres lass form here to SAN and AVN

Increases heart rate = sympathetic nervous system linked to SAN

Decrease heart rate = Parasympathetic nervous system linked to SAN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Chemoreceptors during recovery

6

A

High O2
Less CO2 causes rise in PH
Chemical change detected
Fewer impulses sent to cardiovascular centre in medulla oblongata
More impulses sent along parasympathetic neurone which secrete acetylcholine which binds to receptors on SAN
This causes heart rate to decrease to return O2, CO2 and PH to normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Baroreceptors during recovery

5

A

Vasoconstriction causes less blood to be sent to muscles so pressure in arteries rises
More impulses sent to cardiovascular system in medulla oblongata
More impulses sent to parasympathetic neurones which secrete acetylcholine which attaches to receptors on SAN
This results in decrease in impulses from SAN so decreases in impulses to and from AVN
Heart rate slows to reduce blood pressure back to normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Chemoreceptors during exercise

7

A

Increase CO2, Low O2, low PH
Increases CO2 reacts with water so lowering PH
Change in PH is detected by chemoreceptors
More impulses sent along a sensory neurone to cardiovascular centre
Nerve Impulses sent along sympathetic neurone which secrete noradrenaline which binds to receptors on SAN
Heart rate increases in order to return oxygen, CO2 and PH to normal
Increase in blood flow also results in more CO2 being removed by lungs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Baroreceptors during exercise

5

A

Vasolidation directs more blood to muscles so pressure in arteries falls
Fewer impulses to cardiovascular centre of brain
Increased impulses along sympathetic Neurone which secrets noradrenaline which binds to receptors on SAN
Increased impulses from SAN so increased impulses to and from AVN
heart rate speeds up to return pressure to normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Survival and response 7

A

Organisms increase their chances of survival by responding to changes in their external environment
Animals and plants respond differently
Any change in external or internal environment is called a stimulus.
Stimulus leads to a response
The ability to respond increases the organisms chance of survival
Those that survive have a greater chance to reproducing and passing on alleles
Selection pressure favouring organisms with the most appropriate response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Survival and response order

A

Stimulus- receptor - coordinator - effector - response

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Tropism definition

2

A

A directional growth response In Which the direction of the response is determined by the direction of external stimulus

Positive tropismes are growing towards the direction of the stimulus and negative are growing away from the direction of the stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

5 types of Tropisms

A

Phototropism- shoots grow towards ty r light to increase the rate of photosynthesis
Gravitropism- shoots grow upwards and roots grow downward towards the pull of gravity
Chemotropism- pollen tubes grow towards chemicals given off by the ovary in a flower
Thigmotropism- shoots respond to touch by growing around other plants
Hydrotropism- roots grow towards water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Plant growth regulators/ plant growth factors ( plant hormones)

A

Cells plant growth

They are produced in small quantities and are transported to the target cells by active transport, diffusion and in the phloem and xylem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Phototropism

A

A shoot will grow towards a light stimulus because cells in the side of the shoot away from the light elongate more rapidly than cells in the side facing the light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Process of phototropism

3

A
  1. Cells in the tip of the shoot produce indoleacetic acid(IAA) this belongs To a group of substances called auxins. This is then transported down the stem
  2. Light on one side of the stem cause IAA to move to the shaded side, so a high concentration build up on the shaded s side
  3. IAA cause cell elongation and there are more IAA on the shaded side the cells elongate more and the shoot bends towards the light
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Role of IAA

A

Hydrogen ions are actively transported into the cell walls by an ATPase enzyme in the plasma membrane.
The resulting low PH activates wall loosening enzymes which break bonds within the cellulose so that the wall becomes less rigid and can expand as water moves into the cell by osmosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Gravitropism

2

A

The response of a horizontally growing root to gravity
IAA also controls the bending of the roots in response to gravity.
Wheras in shoots a high concentration of IAA increases cell elongation in the roots it inhibits cell elongation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Process of gravitropism

4

A
  1. Cells in the tip of the root produce IAA, which is then transported along the root. Initially it is transported to all sides of the root.
  2. Gravity influences the movement of IAA from the upper to lower side of the root
  3. A greater concentration of IAA builds up on the lower side of the root
  4. IAA inhibits cell elongation so the cells on this side elongate less and the root bends down.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Taxis

2

A

A change in directional movement in response to a stimulus

Positive taxis is moving towards a stimulus and negative taxis is moving away from a stimulus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Kinesis

A

A change in the rate of movement of an animal in response to a stimulus
Increasing the rate of movement in unfavourable conditions, increases the chance of moving away from the conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Organisation of the nervous system

2

A

The nervous system compromises: sensory neurones, the relay neurones found in the brain and spinal cord and motor neurones

The neurones found in the brain and spinal chord make up the central nervous system and the motor and sensory neurones are found in the peripheral nervous system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Reflex arc

4

A

A rapid, involuntary, short-lived response to a stimulus.
These reflexes are protective-help organisms avoid danger
Present from birth and do not need to be learnt
Sensory, relay and motor neurone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Sensory neurones

A

Transmit electrical impulses from a sensory receptor to the CNS (brain or spinal chord)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Interneurone/ relay neurone

A

Transmit nerve impulses between other neurones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Motor neurone

A

Transmit nerve impulses from the CNS to an effector such as a muscle or gland

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Cell body

A

Part of neurone containing nucleus and organelles. Associated with the production of proteins and neurotransmitter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Axon

A

Carries nerve impulse away from the cell body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Myelinated neurones

3

A

Some axons and dendrites have Schwann cells wrapped around them producing multiple layers of cell surface membrane called myelin

A myelin sheath speeds up the transmissions of a nerve impulse along a neurone

The gaps between the Schwann cells are called nodes of Ranvier

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

The nerve impulse

2

A

Produced by altering the permeability of the membrane of the nerve cell to sodium and potassium ions
The movement of ions through specialised channel proteins in the axon membrane changes the potential difference across the membrane and impulses are transmitted along axons of neurones as a series of action potentials.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Four cation pumps/ channels involved in axon membrane

A
  1. Sodium potassium pump- requires ATP
  2. Potassium ion leakage channel
  3. Sodium ion voltage gated channel
  4. Potassium ion voltage gated channel
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Resting potential

A

The potential difference or voltage across the neurone cell membrane while the neurone is at rest- not conducting a nerve impulse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Resting potential process

4 + 2

A
  1. Sodium potassium pumps in the plasma membrane actively transport 3 Na+ out and 2 K+ into the axon
  2. The membrane is relatively impermeable to the sodium ions so they build up on the outside of rhe axon but it is permeable to potassium ions which diffuse form the inside to the outside of the axon yrh through the leakage channel down their conc gradient. They won’t completely leak out because they are attracted inwards by the negative charge inside the cell.
  3. This results in the outside of the axon being positively charged in relation to the inside- the membrane is polarised. The PD across the membranes is called the resting potential and measured roughly 70mV.
  4. the sodium and potassium gated voltage channels are closed. These are only involved in the action potential

ATP required as as source of energy to maintain resting potential

The outside of the membrane becomes positive- so as a result an electrochemical gradient is produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

The action potential

2

A

A depolarisation of the cell membrane so that the inside is more positive than the outside, with a potential difference across the membrane of +40mV.
This can be transmitted along the axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Sequence of action potential

9

A
  1. Membrane at resting potential 70mV
  2. Stimulus applied which exceeds the threshold value- opens voltage gated sodium ion channels and sodium ions diffuse into the axon down a gradient
  3. Membrane depolarises
  4. Inside of axon becomes more positive compared to outside
  5. Potential difference across the membrane is approximately +40mV
  6. Voltage gated sodium ion channels close and voltage gated potsssium ion channels open
  7. Potassium ions diffuse out of the axon- potential difference becomes negative- repolarisation. Potassium ion channels close
  8. Hyper polarisation- membrane cannot depolarise. This is caused bu the overshot which occurs because the outward flid if potassium ions reaches equilibrium before the resting potential is restored.
  9. Resting potential restored because of the action of Na+/K+ ATPase
38
Q

An action potentials will only be initiated if

A

The stimulation reaches a certain value called the threshold potential
The stimulation must be sufficiently strong to trigger opening of the voltage gated sodium ion channels
If the stimulation is not sufficiently strong the threshold potential will not be reached and an action potential will not take place

39
Q

All or nothing law

A

If the stimulation exceeds the threshold potential then all the voltage gated sodium channels open and a full action potential occurs

40
Q

The intensity of a particular stimulus is distinguished bu

A

The frequency of the action potentials it initiated and not the size of them

41
Q

Transmission of an action potential in non myelinated neurones
5

A

The action potential occurs in just one section of the axon
Small electrical currents called local currents are set up, these have the effect of opening up the gates sodium ion channels in the adjacent small section of the axon.
Sodium ions diffuse across the membrane of the next small section and an action potential is initiated
The impulse is therefore propagated as a series of action potentials, each action potential initiated another action potential in the next section of the axon
The larger the diameter of the axon the faster the impulse is transmitted

42
Q

Transmission of action potential in myelinated neurones

5

A

Ions can only cross the membrane of myelinated axons at the nodes of Ranvier which are about 1mm apart
Action potentials therefore jump from one node to the next- saltatory conduction
The rate of transmission of impulses is consequently much faster in myelinated axons than non- myelinated
Myelinated neurones tend to therefore be smaller in diameter than non-m
Myelin is a fatty substance which insulates the axon and prevent s impulses in one neurone passing to other adjacent neurones

43
Q

Refractory period

2

A

Once an action potential has been created in any region of an axon, there is a period afterwards when inward movement of sodium ions is prevented because the sodium voltage gated channels are closed
During this time, it is impossible for a further action potential to be generated

44
Q

Role of refractory period

3

A
  1. It ensures that action potential are in one direction only
  2. Produces discrete ( separate) impulse
  3. Limits the number of action potential
45
Q

3 factors affecting the speed of an action potential

A

Myelin sheath

Diameter of axon

Temperature

46
Q

Myelin sheath affecting the speed of an action potential

A

Acts as an electrical insulator, preventing an action potential generating in the area of axon covered by myelin
Action potential jumps from node of rancier

Speeds up

47
Q

Diameter of axon affecting the speed of an action potential

A

The greater the diameter the faster the speed of conduction because there is less resistance to the flow of ions than in the cytoplasm of smaller axons. With less resistance, depolarisation reaches other parts of the neurone cell membrane quicker

48
Q

Temperature affecting the speed of an action potential

A

The speed of conduction increases as the temperature increases because ions have more kinetic energy. Very high temperature proteins denature

49
Q

Structure and function of synapses
Cholinergic
4

A

A synapse is a junction between two neurones or between a neurone and an effector

Impulses can cross from one neurone to the next by means of a chemical neurotransmitter, acetylcholine binds to cholinergic receptors

Synapses are very important because they give the nervous system control over the transmission of impulses, impulses can be stopped, passed on to more than one neurone or directed along certain neuronal pathways

At a synapse he neurones are not in directs contact, there is a small gap, called the synaptic cleft 20-20nm. An impulse from one neurone is carried across the gap by a neurotransmitter which initiates or inhibits action potentials in the adjacent neurones

50
Q

Transmission across a cholinergic synapse sequence

8

A
  1. Action potential arrives at presynaptic membrane
  2. Ca2+ channels open and Ca2+ ions diffuse through the presynaptic membrane into the synaptic knob.(pumped out after by AT
  3. synaptic vesicles containing acetyl choline move towards presynaptic membrane(ATP)
  4. Vesicle fuses with presynaptic membrane and acetylcholine is released from synaptic vesicles into the synaptic cleft by of
  5. ACh diffusés across synaptic cleft to post synaptic membrane
  6. ACh binds with specific receptor protein of postsynaptic membrane
  7. Sodium channels in post synaptic membrane open and sodium ions enter and depolarise the membrane starting a new action potential
  8. The enzyme acetylcholineesterase breaks down the ACh and it diffusés back into the synaptic knob where it is resynthesised into neurotransmitter- requires ATP
51
Q

Acetylcholinesterase use in synapse

2

A

Hydrolyses acetylcholine to ethanoic acid and choline

Stops the transmission of signals so that the synapse does not continue to produce action potentials in the postsynaptic neurone

52
Q

Excitatory synapses

A

The binding of neurotransmitter to the receptor proteins opens sodium channels in the post- synaptic membrane initiating an action potential

53
Q

Inhibitory synapses

A

the binding of the neurotransmitter makes the resting potential of the post synaptic membrane more negative( hyperpolarise the post synaptic membrane) and therefore making it less likely that the threshold potential will be reached and an action potential initiated

54
Q

Role of synapse

A

Allows the nerve impulse to be transmitted between neurones and ensures that transmission of action potentials is in one direction only- vesicles of neurotransmitter are only in the presynaptic knob and receptors only on the post synaptic membrane

55
Q

Summation

A

Sometimes the quantity of neurotransmitter resulting form one impulse in the presynaptic membrane is not sufficient to cause depolarisation of the post synaptic membrane
To produce depolarisation, several action potentials are needed to produce enough transmitter to overcome the threshold of the post synaptic membrane. Done in two ways- spatial or temporal

56
Q

Spatial summation

A

When several action potentials from different neurones arrive at the post synaptic membranes at the same time,each releasing small quantities of neurotransmitter which combines to produce an action potential in the post synaptic neurone
Each presynaptic neurone releases a small quantity of neurotransmitter which together results in an action . Potential in the post synaptic neurone

57
Q

Temporal summation.

A

When several action potentials arrived very closely after one another and each releases a set volume of neurotransmitter which combines to initiate an action potential in the post synaptic neurone. If the impulses arrive too far apart(weak stimulus) then the neurotransmitter has been degraded before the effects of impulses can be combined
This can prevent over stimulation or fatigue of the neurone

58
Q

Receptors

2

A

The CNS receives sensory information from its internal and external environment through a variety of receptors, each type responding to a different and specific type of stimulus

Sensory reception is the function of these receptors, wheras sensory perception involves making sense of the information from the receptors

59
Q

Role of a transducer

2

A

To convert one form of energy (from the stimulus) into another form.
Receptors in the nervous system convert the energy of the stimulus into electrical energy used by neurones

60
Q

THE resting potential

3

A

When a receptor has not been stimulated it is in it it’s resting state.
There is a difference in charge between the inside and the outside of the cell. The inside is more negatively charged.
There is a voltage across the membrane- potential difference

61
Q

The generator potential

A

When a stimulus is detected the cell membrane is excited and becomes more permeable, allowing more ions to move in and out of the cell- altering the potential difference
A change in potential difference due to a stimulus is known as a generator potential

62
Q

The action potential

A

If the generator potential is big- reached the threshold- it will trigger an action potential- an electrical impulse along a neurone

63
Q

Pacinian corpuscle

5

A

Responds to mechanical pressure
Receptors which occur deep in the skin and are most abundant on fingers and soles of feet
Also in joints, tendons, ligaments, enable the organism to know which joints are changing direction
The single sensory neurone of a Pacinian corpuscle is at the centre of layers of tissue, each separated by a gel. (Onion appearance)
The sensory neurone ending at the centre of the Paxinian corpuscle has a special type of sodium channel in its plasma membrane- stretch mediated sodium channels. These change the permeability of sodium ions when they are deformed

64
Q

Pacinian corpuscle process

5

A
  1. In its resting state the stretch mediated sodium ion channels of the membrane are too narrow to allow sodium ions to pass through
  2. When pressure is applied the Pacinian Corpuscle lamellar becomes deformed and the membrane around the neurone becomes stretched
  3. This stretching widens the sodium channels and allows sodium ions to diffuse into the neurone
  4. This influx changes the potential and depolarises the membrane- producing a generator potential
  5. Generator potential rises above the threshold level and creates an action potential
65
Q

Receptors in the eye

A

Photoreceptors are found on the retina of the eye
The two types are rods and cones
Both act as transducers converting light energy into electrical energy

66
Q

Rods

6

A

Rod shaped

Greater number

Distribution more at the periphery of the retina absent at the fovea

Poor visual acuity

Sensitive to low light intensity

One type only

67
Q

Cones

6

A

Cone shaped

Fewer number

Distribution- fewer at the periphery of the retina, concentrated at the fovea

Good visual acuity

Not sensitive to low light intensity

Three types- each to different wavelength

68
Q

Three different types of muscle cells

A

Cardiac muscle contracts without conscious control. Only found on the heart

Skeletal muscle, also called striated, stripped or voluntary muscle moves the skeleton

Smooth muscle, also called involuntary muscle contracts without conscious control. Found in the walls of internal organs eg stomach, intestine, blood vessels

69
Q

Role of skeletal muscle

4

A

To bring about movement two bones have to move in relation to one another about a joint
Skeletal muscles are attacked to bones by tendons
Ligaments attach bone to other bones to hold them together
Pairs of skeletal muscles contact and relax to move bones at a joint- the bones of the skeleton are incompressible so they act as levers

70
Q

Muscles are usually found in

4

A

Antagonistic pairs
One muscle contacts to bring about movement in one direction and it’s pair contracts to bring about movement in the opposite direction.
This is because muscles can only exert a force when they are contracting.
They can only lengthen again when they are passively stretched bu the action of an antagonistic muscle

71
Q

Muscles cannot push,

A

they contact or relax

72
Q

To bend the elbow

A

the biceps muscle contacts pulling the radius upwards and the triceps relaxes. The biceps is called a flexor muscles because it causes flexing of the elbow

73
Q

To straighten the elbow

A

the biceps relaxes and the triceps contracts pulling the ulna downwards the biceps is passively stretched. The triceps is called an extensor muscle because it straightens the elbow.

74
Q

Structure of skeletal muscle

7

A

Made up of large bundles of long cells walked muscle fibres.
Cell membrane is called sarcolemma
Parts of the sarcolemma fold inwards across the muscles fibre and stick into the sarcoplasm(cytoplasm) which are called t tubules and help to spread electrical impulses throughout the sarcoplasm so they can reach the muscle fibre
A network of internal membranes called sarcoplasmic reticulum runs through the sarcoplasm.
The sarcoplasmic reticulum stores and releases calcium ions that are needed for muscle contraction.
Muscles fibres have lots of mitochondria to provide ATP.
They are multinucleate

75
Q

Each muscle cell contains

A

Bundles of myofibrils

Myofibrils are made up of protein filaments which Interlock in a regular way. The thin filaments are actin and the thick are myosin

This gives skeletal muscles a striated(striped) appearance

76
Q

The sliding filment model of muscular contraction

A

When a muscle contracts the actin filaments are drawn in between the myosin filaments so shortening the sarcomere, because the sarcomere contracts the whole myofibrils contracts

77
Q

Bands and zones when muscle contracts

A

H zone and I band are narrower

A stays the same

78
Q

Tropomyosin

A

Reinforced actin and blocks binding site

79
Q

Neuromuscular junction

A
  1. Action potential arrive at many neuromuscular junctions simultaneously, this depolarises the membrane and causes Ca2+ protein channels to open and Ca2+ to diffuse into the synaptic knob
  2. Ca2+ cause synaptic vesicles to fuse with the presynaptic membrane and release acetylcholine into the synaptic gap
  3. Acetylcholine diffuses across the synaptic cleft and binds with receptors on the muscle sarcolemma causing depolarisation
  4. Action potential travels down the the T tubule and cause Ca2+ to be released from sarcoplasmic reticulum
  5. Ca2+ causes tropomyosin molecules that wee blocking the binding site in the actin filament to pull away, unblocks binding site on the actin allowing actin myosin cross bridge to form
  6. ADP molecules attached to the myosin head mean that they are in a state to bind to the actin filament and form a cross bridge
  7. Once attached to the actin filament, the myosin heads change their angle, pulling the actin filament along as they do so and releasing ADP and Pi. Power stroke
  8. An ATP molecules attaches to the myosin head, causing it to detach from actin filament
  9. The Ca ions then activated ATPase, which hydrolyses ATP to ADP and Pi. The hydrolysed provides energy for myosin head to return to its original position
  10. The myosin head, once more with an attached ADP molecule then reattaches itself further along the actin filament and the cycle is repeated as long as the concentration of calcium ions remains high
80
Q

As the mousing molecules are joined tail to tail in two oppositely facing sets
4

A

The movement of one set of myosin heads is in the opposite direction to the other set
This means the actin filaments are also moved in opposite direction
This movement pulls the actin filaments towards each other and so shortness the sarcomere
It is important that the myosin ‘tails’ are joined in the middle in order for the contraction of a sarcomere to result in shortening of the muscle

81
Q

Muscle relaxation

3

A

When nervous stimulation stops, calcium ions are actively transported back into the sarcoplasmic reticulum using energy from the hydrolysis of ATP
The réabsorption of the Ca2+ allows tropomyosin to block the actin filament again
Myosin heads are no longer able to bind and contraction stops, the muscle relaxes, actin filament slide back to their original position due to the action of antagonistic muscle

82
Q

Role of ATP

4

A
  1. ATP causes myosin head to detach from actin filament
  2. Hydrolysis of ATP to ADP + Pi causes myosin head to move back to original position
  3. Presence of ADP attached to myosin head allows a crossbridge between actin and myosin to form
  4. Release of ADP+Pi to allow power stroke to take place
83
Q

Role of Ca2+

2

A
  1. Causes tropomyosin to move and unblock actin binding site which allows myosin to bind to actin
  2. Activates ATP hydrolase causing ATP to hydrolyse to ADP + Pi
84
Q

Energy supply during muscle contraction

A

There is very little ATP stored in a muscle so as soon as contraction starts more ATP has to be generated, done in 3 ways:

Aerobic respiration using glucose and oxygen

Anaerobic respiration- leads to toxic lactate production

Créatine phosphate is a molecule stored in the cytoplasm of muscle cells. The Phosphate group can be used to phosphorylate ADP to ATP

85
Q

Slow twitch muscle fibres

5

A

Contract slowly and can work for a long time without tiring.
High proportion of these can be found in muscles used for posture
Energy is released slowly through aerobic respiration
They have lots of mitochondria and good blood suply
They are rich in myoglobin, high affinity to O2, a red coloured protein that stored oxygen so are reddish in colour

86
Q

Fast twitch muscle fibre

A

Contact very quickly but tire easily
Good for sprinting and and eye movement
Energy released quickly through anaerobic respiration using glycogen in fast twitch muscle fibres
They also have stores of créatine phosphate
They have very few mitochondria and a lot less myoglobin, whitish colour

87
Q

Which cell doesn’t undergo cytokinesis

A

Muscle cells

88
Q

Difference between synapse and neuromuscular junction

3

A

Between neurone post synaptic cell is a neurone whereas at neuromuscular junction post synaptic cell is a muscle cell

Between neurones neurotransmitter may be noradrenaline, acetylcholine or GABA whereas at neuromuscular junction it is always acetylcholine.

Between neurones synapse can be inhibitory or excitatory whereas in neuromuscular junction it os always excitatory

89
Q

Similarities. Of synapse between neurones and neuromuscular junction

A

Neurotransmitter is secreted from vesicles, diffuses across the cleft, binds to receptor proteins on post synaptic membrane and is broken down by an enzyme

90
Q

vasodilation

A

widening of your blood vessels,

91
Q

vasoconstriction

A

narrowing of blood vessels.

Biology A Level (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions