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BIOLOGY A LEVEL > CHAPTER 13 - NEURONAL COMMUNICATION > Flashcards

CHAPTER 13 - NEURONAL COMMUNICATION Flashcards

Coordination, Neurones, Sensory receptors, Nervous Transmission, Synapses, Organisation. of Nervous system, Structure and function of the brain, reflexes, Voluntary and involuntary muscles and Sliding Filament Model

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1
Q

What are some internal environments that needs to be maintained

A

Blood glucose concentration
internal temperature
Water Potential
Cell pH

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2
Q

Name Some external environments

A

Humidity
External temperature
Light intensity
New or Sudden sound

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3
Q

How do animals and plants respond to changes?

A

Electrical responses - neurones
Chemical responses - Hormones

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4
Q

What is Homeostasis?

A

Functions of body coordinating to maintain a relatively constant internal environment

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5
Q

What organs work together to maintain a constant blood glucose concentration

A

Exocrine pancreas, duodenum, ileum, liver and endocrine pancreas

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6
Q

What is cell signalling

A

Coordinating responses by releasing chemicals to cause a change or effect on another cell

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7
Q

How can cell signalling be used locally and over long distances

A

Locally - neurotransmitters at a synapse
Long distances - Hormones eg. ADH from Pituitary gland to kidneys to maintain water balance

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8
Q

State one internal factor which causes a response in A plant and an animal

A

A plant - Water potential in cells
Animal - Blood pH

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9
Q

Describe how cells are able to communicate with one another

A

Cell releases a chemical

which has an effect on a target cell

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10
Q

Using examples, explain how and why coordination is required in a multicellular organism

A

Organism needs to respond to internal/external changes for survival

occurs by electrical impulses/nervous system in animals

chemicals/hormones/hormonal system in plants/animals

/ named example of hormone or chemical

different cells rely on others for materials/removal of waste

named example e.g., glucose/oxygen

different organs work together to ensure homeostasis

named example e.g., brain and skin in temperature control

cells communicate through cell signalling

named example of where this occurs

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11
Q

What do neurones do?

A

Transmit electrical impulses rapidly around the body so that the organism can respond to changes in internal and external environment

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12
Q

What is a Neurone comprised of?

A

Cell body - contains nucleus, with lots of endoplasmic reticulum and mitochondria to produce neurotransmitters

Dendrons - Short extensions from the cell body, divides into dendrites, takes impulse towards cell body

Axons - Elongated nerve fibres that take impulse away from cell body

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13
Q

What type of Neurones are there

A

Sensory
Relay
Motor

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14
Q

What do sensory neurones do?

A

Transmit impulses from sensory receptor cell to a relay neurone, motor neurone or the brain, containing 1 dendron and 1 axon

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15
Q

What do relay neurones do?

A

Transmit impulses between neurones eg from sensory neurones to motor neurones
Containing many short axons and dendrons

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16
Q

What do motor neurones do?

A

Transmit impulses from a relay neurone or sensory neurones to an effector, such as a muscle or gland - containing one long axon and many short dendrites

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17
Q

What is the electrical impulse pathway?

A

Receptor - Sensory Neurone - Relay Neurone - Motor Neurone - Effector Cell
RSRME

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18
Q

What are myelin sheaths made out of?

A

Schwann Cells

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19
Q

What do myelin sheaths do?

A

Provides electrical insulation and allows for Neurones to conduct the electrical impulse at faster speeds

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20
Q

What speeds can myelinated and unmyelinated neurones transmit impulses at?

A

100 metres per second myelinated
1 metre per second unmyelinated

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21
Q

What are Nodes of Ranvier

A

Small gaps between Schwann cells so the electrical impulse jumps from one node to another as it travels across the neurone

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22
Q

Why is jumping across nodes of ranvier fasrer than a non-jumping impulse

A

Continuous transmission along the nerve fibre is much slower

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23
Q

State the difference between the function of a motor neurone and a sensory neurone

A

Sensory neurones transmit impulses to the CNS from receptor,

motor neurones transmit impulses away from the CNS / to an effector

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24
Q

Describe the difference in structure between a myelinated and non-myelinated neurone and how this affects the speed a nerve impulse is transmitted

A

Axon of a myelinated neurone is covered in myelin
myelin is an electrical
insulator
the sheath is formed by Schwann cells growing around the axon several times
there
are gaps in the myelin sheath known as nodes of Ranvier
electrical impulse moves in a series of
‘jumps’ from one node to the next/saltatory conduction
impulse transmitted much faster than
along an unmyelinated axon

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25
Q

What is MS (multiple sclerosis)

A

MS is an autoimmune disease which affects nerves in the brain and spinal cord, causing a wide range of symptoms, including problems with muscle movement, balance and vision`

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26
Q

Why is MS an autoimmune disease

A

Immune system attacks healthy body tissue, leading to a thinning or complete loss of myelin sheath - eventually leading to a breakdown of axons

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27
Q

State what is meant by an autoimmune disease

A

A disease causing the body’s immune system to attack its own cells

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28
Q

Describe the role of myelin in the body

A

Speeds up transmission of nerve impulses

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29
Q

One of the symptoms of MS is the loss of vision normally in only one eye. Suggest why a damaged myelin sheath could prevent a person from being able to see

A

Light energy detected by sensory receptor/rod/cone cell in eye

impulse does not reach CNS/brain or impulse received too slowly

due to sensory neurone axon being broken down

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30
Q

What do sensory receptors do?

A

Convert stimulus they detect into a nerve impulse

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31
Q

What are the two main features of sensory receptors

A

Specific to a single type of stimulus

Acts as transducer - convert a stimulus into a nerve impulse

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32
Q

What are the 4 main types of sensory receptor present in an animal?

A

Mechanoreceptor
Chemoreceptor
Thermoreceptor
Photoreceptor

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33
Q

What is the stimulus, example of receptor and example of sense organ for a mechanoreceptor

A

S: Pressure and movement
R: Pacinian corpuscle (detects pressure)
O: Skin

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34
Q

What is the stimulus, example of receptor and example of sense organ for a Chemoreceptor

A

S: Chemicals
R: Olfactory receptor (detects smells)
O: Nose

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35
Q

What is the stimulus, example of receptor and example of sense organ for a Thermoreceptor

A

S: Heat
R: End-bulbs of Krause
O: Tongue

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36
Q

What is the stimulus, example of receptor and example of sense organ for a Photoreceptor

A

S: Light
R: Cone cells (detects different light wavelengths)
O: Eye

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37
Q

What are Pacinian corpuscles?

A

Specific sensory receptors that detect mechanical pressure, located deep within skin

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38
Q

What type of sodium ion channel do pacinian corpuscles have?

A

Stretch-mediated sodium channels

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39
Q

How do pacinian corpuscles convert mechanical pressure into a nervous impulse?

A

In normal state, stretch-mediated sodium ion channels are too narrow to allow sodium ions through them, at resting potential

When pressure is applied, corpuscle changes shape, causing membrane to stretch

Causes Na+ channels to widen - Na+ can now diffuse into neurone

Influx of sodium ions causes membrane depolarisation - creating generator potential

Generator Potential creates action potential (nerve impulse) that passes along the sensory neurone (transmitted all the way through to CNS)

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40
Q

Describe the role of a sensory receptor in the body

A

Detect stimuli
convert energy into a nervous impulse

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41
Q

State the transformation that takes place in a cone cell

A

Light energy is converted into a nervous impulse/action potential

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42
Q

Explain how your body detects that your finger has touched a pin

A

When you touch the pin it exerts mechanical pressure on your skin

Pacinian corpuscle found within skin detects pressure

pressure changes shape of Pacinian corpuscle

stretch-mediated sodium channel in neuronal membrane stretches

channel widens

sodium ions diffuse into membrane

membrane is depolarised/generator potential created

generator potential creates an action potential

action potential transmitted along neurones to CNS/brain

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43
Q

What is resting potential

A

When neurone isn’t transmitting an impulse, the difference in charge between inside and outside of axon is the resting potential

Outside of membrane is more positively charged than inside of axon

Membrane is polarised as there is a potential difference across it = -70mV

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44
Q

What events result in the creation of a resting potential

A

Na+ are actively transported out of the axon whereas K+ are actively transported into the axon by Sodium-potassium pump (3 Na+ out, 2 K+ in)

Results in more Na+ outside the membrane than inside axon cytoplasm, but more K+ inside than outside - hence more sodium ions can diffuse back into the axon down its electrochemical gradient whereas potassium ions diffuse out

Most of the gated Na+ channels are closed - prevents movement of sodium ions but K+ channels are open, so K+ can diffuse out - more positive charged ions outside the axon than in, creating the -70mV resting potential

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45
Q

What happens to the membrane when a stimulus is detected

A

Potential difference across the membrane rapidly changes and becomes +40MV - depolarisation

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46
Q

What happens when the impulse passes?

A

Repolarisation occurs - postive back to negative

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47
Q

How do action potentials occur

A

When protein channels in axon membrane change shape as a result of the change of voltage across its membrane, results in opening or closing (voltage-gated ion channels)

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48
Q

What events take place during an action potential

A

Neurone at resting potential - no impulse transmitted, K+ channels open, Na+ closed

Energy of the stimulus causes Na+ volatge-gated ion channels to open - increase permeability to Na+ - more enter - less negative

This charge causes more Na+ to diffuse into axon - positive feedback

Potential difference reaches +40mV - Voltage gated Na+ channels close and K+ open

K+ ions diffuse out of axon, reducing charge, axon more negative than the outside

Loss of K+ results in becoming more negative than resting state - Hyperpolarisation - leading to closing of K+ channels, and only Sodium-potassium pump causes removal of sodium ions - leading to return to resting potential - Repolarised

(Page 350 for graph)

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49
Q

Describe the series of events in the propogation of action potentials

A

At resting potential, the [Na+] outside the axon are higher than inside, where as [K+] is higher inside than outside. The overall [+ve] is greater outside than inside (polarised membrane)

Stimulus causes influx of Na+ and depolarisation of membrane - action potential created

Localised electrical circuits established by the influx of Na+ in region causes depolarisation. behind this region, Na+ channels close and K+ channels open

Action potential is propagated along the axon, inward influx of K+ causes repolarisation behind section

Following repolarisation of axon membrane ,the axon membrane returns to its restin gpotential in readiness for new stimulus

(pg 351 for diagram)

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50
Q

What is the refractory period?

A

The period of time where the axon cannot be excited again, Na+ channels remain closed preventing movement of Na+ into axon

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51
Q

Why is a refractory period important?

A

Prevents propagation of an action potential backwards as well as forwards, makes sure unidirectional and that action potentials dont overlap

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52
Q

Why can depolarisation only occur at nodes of ranvier

A

No myelin present so Na+ channels are in membrane `

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53
Q

What is saltatory conduction?

A

Action potential jumping from one node to another due to localised circuits

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54
Q

Why is saltatory conduction faster than a wave of depolarisation

A

Every time channels open, it takes for ions to move,

saltatory conduction reduces the amount of times the channels open

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55
Q

Why is saltatory conduction more efficient than wave of depolarisation?

A

Less ATP needed during repolarisation as less of the axon is depolarised

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56
Q

What 3 factors affect the speed at which an action potential travels

A

Myelination

Axon diameter - the bigger the diameter, the faster the impulse - less resistance to the flow of ions in a cytoplasm

Temperature - Higher temp, quicker impulse, Ions have higher KE, diffuse quicker

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57
Q

What is the all or nothing principle?

A

If the threshold is reached, an action potential will always be created,

if the threshold is not reached, no action potential will be triggered

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58
Q

What affect does the size of a sufficient action potential have upon stimuli

A

Greater action potential, increased number of stimulus in a given time

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59
Q

State how the body detects the difference between a small and a large stimulus

A

The larger the stimulus the more frequent the nerve impulses/action potentials

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60
Q

State the difference between depolarisation, repolarisation and hyperpolarisation

A

Depolarisation – voltage/potential difference becomes more positive;

repolarisation – voltage/potential difference becomes more negative

hyperpolarisation – when potential difference is lower than resting potential

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61
Q

Describe what would happen if the refractory period didnt exist?

A

The axon could be immediately depolarised after an action potential

therefore the action
potential could travel backwards / in both directions / not reach target cell

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62
Q

Describe how the movement of ions establishes the resting potential in an axon

A

Sodium potassium pump actively transports sodium and potassium ions

three sodium ions moved out
two potassium ions moved in

potassium ions can diffuse out through
open potassium ion channels / sodium ions cannot diffuse in as sodium ion channels closed

more positive ions outside than inside the axon / outside of the cell is more positively charged

cell/axon membrane is polarised / there is a difference in voltage across it

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63
Q

Explain how temperature receptors in the hand generate an action potential in the sensory neurone to tell the body that you are touching a hot object

A

Heat energy acts a stimulus

stimulus causes (voltage–gated) sodium ion channels
to open

sodium ions diffuse into axon

down electrochemical gradient

inside of axon
becomes less negative/more positive/depolarises

an action potential is triggered

along a sensory neurone to the CNS/Brain

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64
Q

What is a synapse?

A

The junction between two neurones (or a neurone and an effector)

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65
Q

How are impulses transmitted across a synapse

A

Neurotransmitters (chemical)

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66
Q

What are the 6 components of the synapse structure

A

Synaptic cleft
Presynaptic neurone
Postsynaptic neurone
Synaptic knob
Synaptic vesicle
Neurotransmitter receptors

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67
Q

What is the synaptic cleft?

A

The gap which separates the axon of one neurone from the dendrite of the next - 20-30nm across

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68
Q

What is a presynaptic neurone

A

Neurone along which the impulse has arrived

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69
Q

What is the postsynaptic neurone

A

Neurone that receives the neurotransmitter

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70
Q

What is the synaptic knob

A

The swollen end of the synaptic neurone, containing many mitochondria and large amounts of endoplasmic reticulum to enable it to manufacture neurotransmitters

71
Q

What is the synaptic vesicle

A

Vesicles containing neurotransmitters, which fuse with the presynaptic membrane and release their contents into the synaptic cleft

72
Q

What are neurotransmitter receptors

A

Receptor molecules which the neurotransmitter binds to in the postsynaptic membrane

73
Q

What are the types of neurotransmitters

A

Excitatory and inhibitory

74
Q

What do excitatory neurotransmitters do

A

Result in the depolarisation of the postsynaptic neurone. If the threshold is reached in the postsynaptic membrane an action potential is triggered - eg. acetylcholine

75
Q

What do Inhibitory neurotransmitters do

A

Result in hyperpolarisation of the postsynaptic membrane. This prevents action potential being triggered. eg. Gamma-aminobutyric acid (GABA)

76
Q

How do transmission of impulses across synapses occur

A

Action potential reaches end of presynaptic neurone

Depolarisation of the presynaptic membrane - Ca2+ channels open

Ca2+ ions diffuse into the presynaptic knob

Causes synaptic vesicles containing neurotransmitters to fuse to presynaptic membrane

Neurotransmitters released by exocytosis

NTs Diffuse across the synaptic cleft and binds to receptor on postsynaptic membrane

Causes Na+ diffusion into the postsynaptic neurone

Triggers an action potential and the impulse is propagated along the postsynaptic neurone

77
Q

Why is it important to remove action potential after it as passed

A

So another stimulus can arrive at the synapse and affect it

78
Q

How are action potentials stopped

A

Any neurotransmitter left in synaptic cleft is removed, acetylcholine is released from receptors on postsynaptic membrane and is broken down by enzymes, RECYCLING

79
Q

What are cholinergic synapses?

A

Synapses that use acetylcholine as the neurotransmitter

80
Q

What enzyme hydrolyses acetylcholine

A

Acetylcholinesterase

81
Q

Describe the events that occur at a cholinergic synapse

A

Arrival of action potential at Presynaptic neurone causes Ca2+ channels to open and ions to enter synaptic knob

Influx of Ca2+ ions causes vesicles to fuse with Presynaptic membrane, acetylcholine released into cleft

Acetylcholine fuses with receptor on postsynaptic neurone, causing Na+ channels to open, causing an influx in sodium ions

which generate an action potential in postsynaptic neurone

Acetylcholinesterase hydrolyses acetylcholine (also released by receptors) into choline and ethanoic acid (acetyl), so it can be recycled

ATP released by Mitochondria used to recombine choline and acetyl to recycle, Na+ channels close due to lack of Acetylcholine in receptors

pg 357

82
Q

What is the role of synapses

A

Ensure impulses are unidirectional - receptors only present on postsynaptic neurone

Can allow one neurone transmitted to multiple synapses - many simultaneous responses

Many neurones can feed into one synapse - many receptors to produce single result

83
Q

What is summation

A

If the amount of neurotransmitter builds up sufficiently to reach the threshold then this will trigger an action potential

84
Q

What are the two types of summation

A

Spatial and temporal

85
Q

What is spatial summation

A

Many presynaptic neurones connect to one postsynaptic neurone. Each releases neurotransmitter which builds up to a high enough level in the synapse to trigger an action potential in the single postsynaptic neurone

86
Q

What is temporal summation

A

When a single presynaptic neurone releases neurotransmitter as a result of several action potentials over a short period, Builds up until the quantity is sufficient to trigger an action potential

87
Q

How do stimulant drugs work?

A

Mimicks shape of neurotransmitter, so they can bind to receptors on postsynaptic membrane to trigger action potentials in postsynaptic neurone (eg. nicotine and acetylcholine)

Or

Stimulates release of more Neurotransmitter (amphetamines)

Or

Inhibits the enzyme responsible for the breakdown of neurotransmitter in the synapse - can result in loss of muscle control (nerve gases stop breakdown of acetylcholine)

88
Q

How do inhibitor drugs work?

A

Blocks receptors so neurotransmitter (eg. curare and acetylcholine) can no longer bind to the receptor and no action potentials can be created, no muscle stimulant - paralysis

Binds to only specific receptors on some of the neurones changing the shape of the receptor so that binding of neurotransmitter increases (eg. Alcohol and GABAa receptors)

89
Q

State the difference between the result of an inhibitory and a stimulatory drug that acts on the nervous system

A

An inhibitory drug results in less action potentials being created

A stimulatory drug creates more action potentials

90
Q

Explain how amphetamines (stimulant) will affect the nervous system

A

Amphetamines stimulate the release of more neurotransmitter

from the presynaptic neurone

therefore it will bind to more receptors/more receptors activated

on the postsynaptic membrane

threshold is reached

more action potentials generated in the post synaptic neurone

greater response to stimulus

91
Q

Explain how alcohol affects the nervous system

A

Alcohol binds to GABA receptors

this changes shape of receptor allowing more A
neurotransmitter (GABA) to bind

this increases activity of the neurotransmitter

GABA decreases the activity of the brain by preventing nervous transmission

92
Q

Serotonin is a neurotransmitter involved in the regulation of sleep and other emotional states. Low levels of serotonin are found in patients suffering from depression. Prozac is an example of a drug used to treat depression. It works by blocking the reuptake of serotonin into the presynaptic neurone. Using your knowledge of synapses, explain how Prozac works

A

Serotonin would normally be taken back into the presynaptic neurone to be used again

prozac would prevent this occurring resulting in higher levels of serotonin in synapse

more serotonin can bind to neurotransmitter receptors

on postsynaptic membrane

depolarisation threshold reached

more action potentials

nervous system more stimulated, reducing depression symptoms

93
Q

State what is meant by a synapse

A

Junction between one neurone and another (or neurone and effector cell)

94
Q

Explain how synapses ensure impulses are only transmitted in one direction

A

Neurotransmitter receptors are only present on the postsynaptic membrane

so can only cause depolarisation of this membrane resulting in action potential

95
Q

Describe one similarity and one difference between temporal and spatial summation

A

Similarity –
both result in a build-up of neurotransmitter in the synapse / both result in an action potential being triggered

difference –
spatial is a result of neurotransmitter being released from many neurones into the same synapse, temporal is a result of small amounts of neurotransmitter being released from a neurone several times in a short period

96
Q

Explain in detail how a motor neurone causes a postsynaptic neurone to depolarise

A

The action potential reaches the end of the pre-synaptic/motor neurone

depolarisation of the pre-synaptic membrane causes calcium ion channels to open

calcium ions diffuse into the presynaptic knob

synaptic vesicles fuse with the presynaptic membrane and release neurotransmitter / exocytosis takes place

neurotransmitter diffuses across the synaptic cleft /binds with receptor on the postsynaptic membrane

sodium ion channels open and sodium ions diffuse into the post-synaptic neurone

threshold potential reached / depolarisation triggers an action potential

muscle cell contracts

97
Q

What are the two systems that the nervous system is organised into

A

Central nervous system (CNS) - Brain and Spinal Cord

Peripheral Nervous system (PNS) - all the neurones that connect the CNS to the rest of the body
(pg 361)

98
Q

What are the two types of functional organisation of the nervous system

A

Somatic and autonomic nervous systems (pg 360+361)

99
Q

What is the Somatic nervous system

A

The system is under conscious control, when you decide to voluntarily do something eg. moving a muscle in your arm. Somatic nervous system carries impulse to the body’s muscles

100
Q

What is the Autonomic Nervous system

A

A constant and subconscious part of the nervous system, used when the body does something automatically without you deciding to do it - involuntary eg. Heart to beat, digestion of food
Autonomic nervous system carries nerve impulses to glands, smooth and cardiac muscles

101
Q

What is the autonomic nervous system further divided into

A

The Sympathetic (Increase in activity) and Parasympathetic (decrease of activity)
(pg 360)

102
Q

State the difference between the peripheral and the Central nervous system

A

The CNS is the brain and the spinal cord

the PNS is all other neurones

103
Q

Sort the following activities into those which are controlled by the somatic nervous system and those which are controlled by the autonomic nervous system
Pupil dilation, Blood pressure, Throwing a ball, Walking

A

Somatic - Throwing a ball, walking
Autonomic - Pupil dilation, Blood pressure

104
Q

State and explain why many autonomic functions can also be controlled by the somatic nervous system

A

for example:
breathing can be controlled

so that a person can hold their breath underwater

as it is not possible to breathe normally in this environment

105
Q

What is an advantage of having a central control centre for the whole body

A

Communication between the billions of neurones is a lot faster than if many control centres for different functions were distributed around the body

106
Q

What is the only nervous reaction that isn’t processed by the brain

A

Reflex actions

107
Q

How is the brain protected?

A

Skull and protective membranes (meninges)

108
Q

What are the 5 main structures in the brain

A

Cerebrum, Cerebellum, medulla oblongata, Hypothalamus and Pituitary gland

109
Q

What does the cerebrum control?

A

Control voluntary action, such as learning, memory, personality and conscious thought

110
Q

What does the cerebellum control?

A

Controls unconscious functions such as posture, balance, and non-voluntary movement

111
Q

What does the Hypothalamus control?

A

Regulatory centre for temperature and water balance

112
Q

What does the pituitary gland control?

A

Stores and releases hormones that regulate many body function

113
Q

Why is the cerebrum highly convoluted

A

Increasing its surface area, increases capacity for complex activity

114
Q

What is the cerebrum split into two of

A

Cerebral hemispheres, each controlling one half of the body

115
Q

What is the outer layer of the cerebral hemisphere known as

A

Cerebral cortex

116
Q

Where do sophisticated processes such as reasoning and decision making occur?

A

Frontal and prefrontal lobe of the cerebral cortex (in cerebral hemisphere/cerebrum)

117
Q

How many lobes are there in the cerebrum and what are they

A

4 - Frontal, Parietal, occipital and temporal

118
Q

What side of the body does the right brain control

A

Left (and vice versa)

119
Q

What does the cerebellum do and what happens if the brain is damaged

A

Control of muscular movement, body posture and balance - but doesn’t initiate movement, coordinated it, receives information from organs of balance in the ears and information about the tone of muscles and tendons. Then relays information to cerebral cortex which controls motor action

If this area of the brain is damaged, suffers from jerky uncoordinated movement

120
Q

What does the medulla oblongata do

A

Regulates Autonomic nervous system which controls actions like breathing rate and heart rate. Also controls activities such as swallowing, peristalsis and coughing

121
Q

What are the functions of the hypothalamus

A

Has centres of parasympathetic and sympathetic nervous systems,

Controls complex patterns of behaviour, such as feeding, sleeping and aggression

Monitors composition of blood plasma, such as the concentration of water and blood glucose - therefore it has a very rich blood supply

Produces hormones - it is an endocrine gland

122
Q

What do the two sections of the pituitary glands do

A

Anterior pituitary gland (front section) - Produces six hormones including follicle-stimulating hormone (FSH) involved in reproduction and growth hormones

Posterior pituitary (back section) - Stores and releases hormones produced by the hypothalamus, such as ADH involved in urine production

123
Q

State the difference between the function of the anterior pituitary and the posterior pituitary

A

Anterior pituitary produces hormones,

posterior pituitary stores and secretes hormones produced by the hypothalamus

124
Q

Sounds are interpreted by the auditory area in the temporal lobe. State the pathway followed by a nervous impulse produced by a sound wave

A

Sound receptor in left ear ———> sensory neurone —-> temporal lobe in right cerebral hemisphere

125
Q

A patient displays 3 symptoms: Asynergia - a lack of coordination in their motor movement, Adiadochokinesia - an inability to perform rapid movements and ataxic gait - staggering movements. Suggest and explain which part of the brain may have been damaged to explain which part of the brain may have been damaged to cause these symptoms

A

Cerebellum

because this region of the brain is responsible for muscular movement, body posture, and balance

126
Q

What is the Reflex arc pathway

A

Receptor (detects stimulus and creates an action potential in the sensory neurone)

Sensory Neurone (carries impulse to spinal cord)

Relay Neurone (connects the sensory neurone to the motor neurone within the spinal cord or brain)

Motor Neurone (carries impulse to the effector to carry out the appropriate response)

Receptor - Sensory Neurone - Relay neurone - Motor Neurone - Effector

127
Q

What is the spinal cord

A

Column of nervous tissue running up the back, surrounded around the spine for protection

128
Q

What is the knee-jerk reflex

A

Spinal reflex testing neural circuit

Leg tapped just below the kneecap, stretching patellar tendon and acts as stimulus

Stimulus initiates reflex arc that causes the extensor muscle on the top of the thigh to contract.

At the same Time, the relay neurone inhibits the motor neurone of the flexor muscle causing it to relax

This contraction coordinated with the relaxation of the antagonistic flexor hamstring muscle causes the left to kick

If this doesn’t occur, it my be a sign of a cerebellar disease

129
Q

Describe the blinking reflex and what can cause it

A

Occurs when cornea is stimulated, to keep the cornea safe from damaged due to foreign bodies (dust, insects etc…) entering the eye.

Blink reflex occurs when sounds greater than 40-60 dB are head,

Occurs when in very bright light to protect the lens and the retina

Impulse passes through a relay neurone in the lower brain stem, sent along motor neurone to initiate a motor response to close eyelids in a consensual response (both eyes are closed in response to stimulus)

If the reflex is not seen, the patient may be brain-dead

130
Q

plan an investigation into how the concentration affects a person’s reaction time

A

Reaction time should be tested before a caffeine drink is given

this should be repeated many times / with many people to obtain reliable results

caffeine drink of known concentration is given to subjects

after a fixed time period, reaction time test is repeated in an identical way to the initial test

a range (ideally 5+) of caffeine concentrations should be investigated

control group / use of placebo caffeine drink

131
Q

Why are reflexes essential for survival?

A

Help body avoid harm, or reduce severity of damage

132
Q

How do reflexes increase survival

A

Being involuntary - prevents an overload of stimulus and Brian can deal with more complex responses

Not learnt - provides immediate protection and is present at birth

Extremely fast - reflex arc is short, only involving a few synapses

Many reflexes are everyday actions such as keeping upright and controlling digestion

133
Q

State the reflex arc which occurs when a doctor test the knee-jerk reflex

A

pressure receptor in skin —– sensory neurone —- relay neurone —- motor neurone — (extensor) muscle

134
Q

Which of the following actions are reflexes - Gagging, speaking, jumping pupil dilation

A

Gagging and pupil dilation

135
Q

State and explain how a reflex action can improve an organisms chances of survival

A

eg. hand placed over burning material, reflex arc formed does not include the brain / it is an involuntary response

which decreases the time taken for the body to react to the situation

136
Q

State and explain the considerations a researcher should take into account when planning an investigation into the effect of drugs, such as caffeine on a group of human volunteers

A

Researcher should take into account: Health benefits / risks

the drug administered could have an effect on the subject’s body

which could be positive or negative

Ethical considerations

when employing a placebo, people may believe that they have received a drug which has a beneficial effect which may or may not be the case

exemplification on the use of a placebo – for example, an experimental drug may be able to cure a condition; use of a placebo means that some of the sample group would not receive the drug

137
Q

What are the 3 types of muscle and what do they do

A

Skeletal - Most of body muscle tissue responsible for movement eg. Biceps and Triceps

Cardiac - Cardiac muscle only found in heart - myogenic (contract without nervous stimulus) causing heart to beat in regular rhythm

Involuntary (Smooth) muscle - Found in many areas eg. walls of hollow organs such as stomach and bladder, and in walls of blood vessels and digestive tract

138
Q

How do the muscles types vary in Fibre appearance, control, arrangement, contraction speed, length of contraction and structure compare

A

pg369 table

139
Q

How are skeletal muscle structured

A

Bundles of muscle fibres, which are enclosed within a plasma membrane known as the sarcolemma

140
Q

Why do muscle fibres win skeletal muscle contain Long nuclei

A

Formed as a result of many individual embryonic muscle cells fusing together, which makes the muscle stronger as there are no gaps between adjacent cells so no weaknesses and ensure the whole fibre contracts at the same time

141
Q

Why do skeletal Muscle fibres have a lot of mitochondria

A

to provide the ATP needed for muscle contraction

142
Q

What is sarcoplasmic reticulum

A

Modified endoplasmic reticulum which extends throughout the muscle fibre and contains calcium ions required for muscle contraction

143
Q

What are myofibrils

A

Long cylindrical organelles made of proteins and specialised for contraction, which collectively are very powerful

Lined up in parallel to provide maximum force

144
Q

What two protein filaments are myofibrils made up

A

Actin - the thinner filament. Consisted of two strands twisted around each other

Myosin - The thicker filament, consisting of long rod-shaped fibres with bulbous head that project to one side

145
Q

What are the 4 components to a myofibril

A

Light bands - regions where actin and myosin filaments don’t overlap (I-bands)

Dark Bands - presence of thick myosin filaments overlapped by actin (A-bands)

Z-line - Line found at the centre of light band (the distance between two Z lines is called a sarcomere)

H-Zone - a lighter coloured region found in the centre of each dark band - only myosin filaments are present at this area

146
Q

Why are there light bands within a sarcomere

A

These are areas where actin and myosin filaments to not overlap.
pg.371, 372

147
Q

What are the properties of slow-twitch fibres

A

Slow contraction
Less powerful contractions
Long period
Dont tire easily
Gain energy from aerobic respiration
Rich in myoglobin (red protein which stores oxygen)
Rich supply of blood vessels and mitochondria

148
Q

Properties of fast-twitch fibres

A

Fibres contract very-quickly
Produce powerful contractions
Short period
Easily tire
Gain energy from Anaerobic respiration
Pale coloured - low levels of myoglobin and blood vessels
Contain more myosin filaments
Stores Creatine Phosphate to rapidly generate ATP from ADP in anaerobic conditions

149
Q

State and explain how you could tell the difference between areas of fast-twitch and slow twitch muscle when observing skeletal muscle under the microscope

A

Slow twitch muscle fibres would appear redder in colour

due to more myoglobin/blood vessels

there would be more blood capillaries and more mitochondria

as these cells carry out aerobic respiration

150
Q

State and explain any differences in composition which may exist in the skeletal muscles of marathon runners and sprinters

A

Marathon runners will have a higher proportion of slow twitch fibres

as these fibres provide contraction over long periods of time

without tiring

marathon runners mainly use aerobic respiration during exercise

which provides the energy for slow-twitch muscles

151
Q

Describe simply the structure of skeletal muscle

A

Muscles are made up of bundles of muscle fibres

each fibre is made up of bundles of myofibrils

each myofibril is made up of protein filaments / actin and myosin

152
Q

Describe the similarities and differences in the structure and function of cardiac and involuntary muscle

A

Similarities:
Both involuntary / unconscious control
both uninucleated / one nucleus per cell

Differences:
Cardiac striated, involuntary not
Cardiac – fibres branched, involuntary – fibres spindle shaped
involuntary are slower to contract
involuntary can contract for longer

153
Q

What model is used to describe muscle contraction

A

Sliding Filament model
(pg 374)

154
Q

What happens to the bands of muscle fibres when the muscle contractions and why

A

Myosin filaments pull actin filaments inwards towards centre of sarcomere

Light bands become narrower
Z-lines move closer together, shortening sarcomere
H-zone becomes narrower

155
Q

What part of the structure of myosin filaments allow them to move backwards and forwards

A

Hinged Globular heads with binding sites for actin and ATP

156
Q

What are present on actin filaments

A

Binding sites for Myosin heads

157
Q

What inhibits the binding sites for myosin heads on actin filaments

A

Tropomyosin, held in place by troponin

158
Q

What is a neuromuscular junction?

A

The point where a motor neurone and skeletal muscle fibre meet

Triggers muscle contraction when an action potential arrives at it

159
Q

How do neuromuscular junctions help to ensure muscle fibres contract simultaneously

A

There are many along the length of a muscle, if only one existed, there would be a wave of contraction and would be slower

160
Q

What is a motor unit

A

All the muscle fibres supplied by a single motor neurone

161
Q

How does force required relate to motor unit stimulation

A

If a strong force is needed, a large number of motor units are stimulated, if a weak force is needed, a small force is required

162
Q

Where does the depolarisation spread to in the sarcolemma

A

T-tubules

163
Q

What are the T-Tubules in contact with

A

Sarcoplasmic reticulum, which contains Ca2+ absorbed actively from the sarcoplasm

164
Q

What happens in the sarcoplasm when an action potential occurs

A

Sarcoplasmic reticulum stimulates Ca2+ channels to open, Ca2+ diffuse down conc gradient flooding sarcoplasm with Ca2+

Ca2+ bind to troponin, causing it to change shape - hence moving away from the Actin-Myosin binding sites, which then allow The bonding of Actin+Myosin

Once myosin head is attached to actin filament, it flexes, pulling actin filament along.

ADP bound to Myosin head is released, ATP binds to myosin head causing detach from actin filament

Ca2+ in sarcoplasm also activate ATPase in myosin, causing hydrolysis of ATP to ADP and Pi, releasing energy for myosin to return to original state

Cycle repeats
(pg 377)

165
Q

How is the energy provided for muscle contraction

A

ATP hydrolysed into ADP and Phosphate group (Pi)

166
Q

What pathways is ATP Generated from

A

Aerobic respiration
Anaerobic respiration
Creatine Phosphate

167
Q

What type of reaction forms ATP in Aerobic respiration, where does it take place and what does it need to occur

A

Oxidative phosphorylation

Mitochondria (Plentiful in muscle)

Oxygen is required (Aerobic respiration used for long periods of low-intensity exercise)

168
Q

How is ATP formed from Anaerobic respiration and what is the drawbacks from it

A

Glycolysis

No oxygen present, pyruvate produced converts to lactic acid which builds up and leads to muscle fatigue (Anaerobic used for short high intensity exercise eg. sprinting)

169
Q

How is ATP produced from Creatine Phosphate

A

ADP is phosphorylated by creatine phosphate, which acts as a reserve supply to immediately combine with any ADP present.

Stores of creatine are used up rapidly as it generates ATP quickly so it is used for short bursts of vigorous exercise (eg tennis serve)

Creatine phosphate store replenished using phosphate from ATP

170
Q

Maybe make flashcard of EMGs

A
171
Q

State two differences in the appearance of a sarcomere in a relaxed and contracted muscle when observed through a microscope

A

In a contracted muscle the light band is narrower

Z lines closer together
H- zone becomes narrower

172
Q

Professional sprinters have high levels of creatine phosphate in their muscle cells. Describe why this is advantageous

A

During a sprint, muscles work so hard oxygen cannot be replaced as quickly as it is used up

aerobic respiration alone can’t be used / anaerobic respiration required

creatine phosphate is a source of phosphate

the more creatine phosphate, the more ADP can be phosphorylated

muscles can perform at maximum rate for longer

173
Q

After a persons death, their body can no longer produce ATP. This results in the stiffening of muscles (Rigour Mortis). Explain why a lack of ATP prevents muscles relaxing

A

ATP is needed to break bond/cross-bridge between actin and myosin

if no ATP available actin remains bonded to myosin

filaments remain in contracted state / filaments can’t slide back to original position

174
Q

Bepridil is a drug that can be used to treat angina, a form of heart disease. It works by partially blocking Calcium ion channels. Explain the effect of bepridil upon heart muscle contraction

A

Muscles do not contract as much

as fewer calcium ions released into sarcoplasm/from sarcoplasmic reticulum

fewer calcium ions bind to troponin

less troponin moves/pulls tropomyosin

myosin-actin binding sites remain blocked

myosin cannot bind to actin to pull filament

BIOLOGY A LEVEL (24 decks)

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