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Biology OCR A A level > Neuronal Coordination > Flashcards

Neuronal Coordination Flashcards

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1
Q

What are 4 changes in the internal environment that could elicit a response from an organism?

A

Blood glucose concentration
Internal temperature
Water potential
Cell pH

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2
Q

What are 4 changes in the external environment that could elicit a response from an organism?

A

Humidity
External Temperature
Light intensity
New or sudden sound

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3
Q

What are electrical responses made via?

A

Neurones

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4
Q

What are chemical responses made via?

A

Hormones

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5
Q

What are the two main reasons why organisms need to be coordinated?

A

Maintain conditions in and out of the body

Position organism in environment for optimal chance of survival

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6
Q

Define ‘homeostasis’

A

Maintenance of a constant internal environment

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7
Q

How does cell signalling work?

A

A cell releasing a chemical which has an effect on another cell called a target cell

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8
Q

What two things can occur due to cell signalling?

A

Transfer of signals locally between neurones and synapses

Transfer signals across large distances using hormones

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9
Q

What are stimulus?

A

Changes in internal and external environments that a nervous system detects

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10
Q

What is the role of neurones?

A

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

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11
Q

What are the 3 main parts of a neurone?

A

Cell body
Dendrons
Axons

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12
Q

What is the cell body made up of?

A

Nucleus surrounded by cytoplasm, with a large proportion of endoplasmic reticulum and mitochondria used in production of neurotransmitters

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13
Q

What are neurotransmitters?

A

Chemicals used to pass signals from one neurone to the next

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14
Q

What are dendrons?

A

Short extensions from the cell body which are responsible for transmitting electrical impulses towards the cell body

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15
Q

What is the role of axons?

A

Singular, elongated nerve fibres that transmit impulses away from cell body

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16
Q

What is the structure of an axon?

A

A cylindrical fibre with a narrow region of cytoplasm surrounded by plasma membrane

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17
Q

What are the 3 main types of neruone?

A

Sensory neurone
Motor neurone
Relay neurone

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18
Q

What is the role of a sensory neurone?

A

Neurones that transmit impulses from a sensory receptor cell to a relay neurone, motor neurone or the brain

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19
Q

What is the structure of a sensory neurone?

A

One dendron which carries impulse to cell body

One axon which carries impulse away from cell body

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20
Q

What are relay neurones?

A

Neurones that transmit signals between neurones

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21
Q

What is the structure of relay neurones?

A

Short axons and short dendrons

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22
Q

What are motor neurones?

A

Neurones that transmit impulses from a motor/sensory neurone to an effector.

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23
Q

What is the structure of a motor neurone?

A

A long axon and many short dendrites

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24
Q

What is the typical pathway an electrical impulse follows?

A 
Receptor
Sensory neurone
Relay neurone
Motor neurone
Effector cell
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25
Q

How do myelin sheaths form?

A

Schwann cells produce layers of membrane which lay down a double phospholipid bilayer every time they grow. This creates a myelin sheath.

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26
Q

What is the role of myelinated sheaths?

A

Insulating layer

Conduct electrical impulses at a much faster speed

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27
Q

What is the node of Ranvier?

A

Small gap(1-3mm) between adjacent Schwann cells

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28
Q

How do electrical impulses travel on myelinated neurones?

A

Electrical impulse ‘jumps’ from one node to the next

Faster

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29
Q

How do electrical impulses travel on unmyelinated neruones?

A

Transmits continuously along nerve fibre

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30
Q

What is the role of a sensory receptor?

A

Convert a stimulus they detect into a nerve impulse

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31
Q

Explain process from sensory receptor to the effector

A

Convert a stimulus they detect into a nerve impulse
Impulse passed to central nervous system via nervous system
Brain coordinates response and sends an impulse to the effector
Effector initiates a response

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32
Q

What are the two main features of a sensory receptor?

A

Specific to a single type of stimulus

Act as a tranducer

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33
Q

What is a tranducer?

A

Something that converts a stimulus into a nerve impulse

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34
Q

What is the name of a nervous impulse produced by a sensory receptor?

A

Generator potential

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35
Q

What do Pacinian corpuscles detect?

A

Mechanical pressure

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36
Q

Where are Pacinian corpuscles located?

A

Deep within skin
Fingers and soles of feet
Joints to know which joints are changing direction

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37
Q

Explain the structure of a Pacinian corpuscle

A

End of sensory neurone within the centre of corpuscle

Surrounded by layers of connective tissue with viscous gel between

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38
Q

What specific structure is present in the Pacinian corpuscle? What is its role?

A

Sodium ion channel

Responsible for transporting sodium ions across the membrane

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39
Q

What is present in the neurone ending of a Pacinian corpsucle?

A

A stretch mediated sodium channel

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40
Q

Give one specific feature of a stretch mediated sodium channel

A

When the channel changes shape it also changes in permeability to sodium

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41
Q

Explain how a Pacinian corpuscle converts mechanical pressure into a nervous impulse

A

Pressure applied to a Pacinian corpuscle, meaning it changes shape.
Membrane surrounding neurones stretch
Membrane stretches, sodium channels present widen
Sodium ions diffuse into neurone
Influx of positive sodium ion changes potential of membrane causing it to become depolarised
Generator potential created
Generator potential creates an action potential that passes along sensory neurone
Action potential passed to central nervous system

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42
Q

What are the two stages that an axon membrane switches between?

A

Resting potential

Action potential

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43
Q

Explain the difference in charge between the inside and outside of a membrane when a neurone is in resting potential

A

Outside of membrane more positively charged than the inside of the membrane

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44
Q

What word is used to describe a membrane in resting state? Why?

A

Polarised

Potential difference across it

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45
Q

What is the potential difference across a membrane during resting potential?

A

-70mV

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46
Q

Explain the movement of sodium and potassium ions across axon

A

3 sodium ions are actively transported out of the axon, while 2 potassium ions are actively transported into the axon.
Occurs via a sodium potassium pump

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47
Q

What is an electrochemical gradient?

A

Concentration gradient of ions

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48
Q

Explain the events that result in creation of action potential

A

3 sodium ions actively transported out, 2 potassium ions actively transported in
More sodium ions on the outside, more potassium ions on the inside
Sodium ions move back in, and potassium out via the electrochemical gradient
Gated sodium ion channels shut limiting movement of sodium ions
Gated potassium ion channels open, so potassium diffuses out
More positively charged ions outside the axon
Creates resting potential, with inside negative relative to outside

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49
Q

What is the potential difference of a membrane during action potential?

A

+40mV

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50
Q

Define depolarisation

A

The change in potential difference from negative to positive

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51
Q

When does depolarisation occur?

A

Energy of stimulus causes some sodium voltage-gated channels to open
Membrane more permeable to sodium ions
Sodium ions diffuse into axon down electrochemical gradient
Inside less negative- depolarised

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52
Q

Give an example of positive feedback within action potential

A

Change in charge following opening of sodium voltage-gated channels causes more sodium channels to open
More sodium ions diffuse into axon

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53
Q

What occurs within the axon once +40mV has been reached?

A

Voltage gated sodium channels shut
Voltage gated potassium channels open
Membrane more permeable to potassium ions

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54
Q

How does repolarisation occur?

A

Once the membrane has reached +40mV and it becomes more permeable to potassium ions, they diffuse out via electrochemical gradient which causes outside to become more negative than inside

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55
Q

What is hyperpolarisation?

A

Excessive numbers of potassium ions diffuse out of the axon resulting in the inside of the axon becoming more negative than in the normal resting state

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56
Q

What is a nerve impulse?

A

An action potential that starts at one end of the neurone and is propagated along the axon to the other end of the neurone

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57
Q

How does a wave of depolarisation occur?

A

Initial stimulus causes a change in the sensory receptor which triggers an action potential within sensory receptor
This is the first region of axon to be depolarised
Sodium ions follow down electrochemical gradient which initiates depolarisation in the next section

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58
Q

What is the refractory period?

A

Short period of time where the axon cannot be excited again and the voltage gated sodium ion channels remain closed, preventing movement of sodium ions into axon

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59
Q

What is the importance of the refractory period?

A

Prevents propagaiton of an action potential backwards along an axon
Prevents overlap- ensures they are unidirectional

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60
Q

What is saltatory conduction?

A

Sodium ions passing through long circuits from one Node of Ranvier to another in a ‘jumping’ motion

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61
Q

Why is saltatory conduction more efficient?

A

Faster
Less channels have to open
Repolarisation uses ATP so doing this less reduces use of ATP

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62
Q

What are three factors which affect speed at which action potential travels?

A

Axon diameter
Temperature
Myelination

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63
Q

How does axon diameter affect speed at which action potential travels?

A

Bigger the axon diameter= faster impulse

Less resistance to flow of ions in cytoplasm

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64
Q

How does temperature affect speed at which action potential travels?

A

Higher temperature=faster
Ions diffuse faster
Only to 40 as protein channels denature

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65
Q

What is the all or nothing principle?

A

The nerve impulse has to reach the threshold value to initiate an action potential

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66
Q

What affect does size of stimulus have on action potentials?

A

Increases frequency of action potential but not size

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67
Q

What is a synapse?

A

The junction between two neurones or a neurone and an effector

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68
Q

What is the synaptic cleft?

A

The gap which separates the axon of one neurone from the dendrite to the next neurone

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69
Q

What is the presynaptic neurone?

A

The neurone along which the impulse has arrived

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70
Q

What is the postsynaptic neurone?

A

Neurone that receives the neurotransmitter

71
Q

What is the synaptic knob?

A

The swollen end of the presynaptic neurone

72
Q

What are the key features of the synaptic knob?

A

Mitochondria and large amounts of endoplasmic reticulum to enable it to manufacture neurotransmitters

73
Q

What is the role of the presynaptic vesicle?

A

Vesicles fuse with eh presynaptic membrane and release contents into the synaptic cleft

74
Q

What are the neurotransmitter receptors?

A

Receptor molecules which the neurotransmitter binds to in the postsynaptic membrane

75
Q

What are the two types of neurotransmitter?

A

Excitatory and inhibitory

76
Q

How do excitatory neurones work?

A

Neurotransmitters result in depolarisation of the postsynaptic neurone. Active potential occurs if threshold is reached

77
Q

Give an example of an excitatory neurone

A

Acetlycholine

78
Q

How do inhibitory neurones work?

A

Neurotransmitters result in the hyperpolarisation of the postsynaptic membrane. Prevents an action potential being triggered.

79
Q

Give an example of an inhibitory neurone

A

GABA

80
Q

Explain the process of synaptic transmission

A

Action potential reaches end of presynaptic neurone
Depolarisation causes the calcium voltage gated channels to open
Calcium ions diffuse into presynaptic knob
Causes synaptic vesicles to fuse with the presynaptic membrane. Neurotransmitter released into synaptic cleft by exocytosis
Neurotransmitter diffuses across synaptic cleft and binds with its specific receptor molecule on the postsynaptic membrane
Sodium ion channels open
Sodium diffuses into postsynaptic neurone
Triggers an action potential and impulse is propagated along the postsynaptic neurone

81
Q

How are neurotransmitters released from the postsynaptic neurone?

A

Removed via enzymes

Some enzymes release neurotransmitter from receptor

82
Q

Why is it important that neurotransmitters are released once they have been used?

A

To ensure that the stimulus is not maintained and another stimulus can arrive

83
Q

What is a cholinergic synapse?

A

Any synapse that uses the neurotransmitter acetlycholine

84
Q

What is acetylcholine broken down into?

A

Choline and ethanoic acid (acetyl)

85
Q

Explain the process of acetyl choline being broken down

A

Acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid
Products taken back to presynaptic knob where they can be reformed

86
Q

What are the 3 main roles of a synapse?

A

Unidirectional
Allow a single stimulus to cause a number of simultaneous responses
Many stimuli can produce one response

87
Q

Define summation

A

The building up of a specific neurotransmitter to sufficiently reach the threshold which will trigger an action potential

88
Q

What are the two types of summation?

A

Spatial

Temporal

89
Q

Explain how spatial summation occurs

A

Number of presynaptic neurones connect to one postsynaptic neurone. Each releases neurotransmitter which builds up to a high enough level to trigger an action potential

90
Q

Explain how a temporal summation occurs

A

Single presynaptic neurone releases neurotransmitter as a result of an action potential occurring frequently

91
Q

What 2 structural systems is the Mammalian nervous system organised into?

A

Central nervous system

Peripheral nervous system

92
Q

What is in the central nervous system?

A

Brain

Spinal cord

93
Q

What is in the peripheral nervous system?

A

Neurones that connect CNS to the rest of the body

sensory and motor

94
Q

What 2 functional systems is the nervous system organised into?

A

Somatic nervous system

Autonomic nervous system

95
Q

What is the somatic nervous system?

A

A system under conscious control for voluntary actions

96
Q

Where does the somatic nervous system carry impulses to?

A

The body muscle’s

97
Q

What is the autonomic nervous system?

A

A system that works constantly that is under subconscious control

98
Q

Where does the autonomic system carry impulses to?

A

Glands, smooth muscle and cardiac muscles

99
Q

What is the autonomic system subdivided into?

A

Sympathetic and parasympathetic

100
Q

What is the difference between the sympathetic and parasympathetic systems?

A

Sympathetic is involved with an increase

Parasympathetic is involved with a decrease

101
Q

What two structures protect the skull?

A

The brain and the mengines

102
Q

What are the names of the 5 main areas of the brain?

A 
Cerebrum 
Cerebellum
Medulla oblongata
Hypothalamus
Pituitary gland
103
Q

What does the cerebrum control? Give 4 examples

A

Controls voluntary actions

Eg. learning, memory, personality and conscious thought

104
Q

What does the cerebellum control? Give 3 examples

A

Controls unconscious function

Eg. posture, balance and non-voluntary movement

105
Q

What does the medulla control?

A

Used in autonomic control

Eg, heart rate and breathing rate

106
Q

What does the hypothalamus control?

A

Regulatory centre for temperature and water balance

107
Q

What is the role of the pituitary gland?

A

Stores and releases hormones that regulate many body functions

108
Q

What are the 3 ways that brains are imaged?

A

Autopsies
MRI
CT scan

109
Q

How are active areas of the brain identified during an MRI?

A

Increased blood flow in the area

110
Q

How does the cerebrum process information?

A

Cerebrum receives sensory information, interprets it with respect to information stored from previous experiences, and then sends impulses along motor neurone to effectors with a suitable response

111
Q

Why is important that the cerebrum has a large surface area?

A

Increases capacity for complex activity

112
Q

Where do the most sophisticated processes occur?

A

Frontal and prefrontal lobe of the cerebral cortex

113
Q

Explain the substructures of cerebrum

A

Two hemispheres called cerebral hemispheres

Outer layer of cerebral hemispheres called a cerebral cortex

114
Q

What occurs at the base of the brain?

A

Impulses from each side of the body cross over so left hemisphere receives impulses from the right side of the body

115
Q

What is the size of the sensory area in cerebrum proportional to?

A

The relative number of receptor cells present in the part of the body

116
Q

What is the size of the motor area in cerebrum proportional to?

A

Relative number of motor endings

117
Q

Which region controls movement in the cerebrum?

A

Primary motor cortex located at back of the frontal lobe

118
Q

How does the cerebellum process information?

A

Receives information from organs of balance and from muscles and tendons, relays information to cerebral cortex which is involved with motor control

119
Q

What are the two centres present in the hypothalamus?

A

Parasympathetic and sympathetic nervous system

120
Q

What are the three main functions of the hypothalomus?

A

Controlling complex patterns of behaviour
Monitoring composition of blood plasma
Producing hormones

121
Q

Where is the pituitary gland located?

A

Found at base of hypothalamus

122
Q

What are the two sections of pituitary gland?

A

Anterior pituitary

Posterior pituitary

123
Q

What does the anterior pituitary gland do?

A

Produces 6 hormones including FSH

124
Q

What does the posterior pituitary gland do?

A

Stores and releases hormones produced by hypothalamus such as ADH

125
Q

What is reflex action?

A

A response to a situation without conscious thoughT

126
Q

Define a reflux

A

An involuntary response to a sensory stimulus

127
Q

What is the reflex arc?

A

Pathway of neurones involved in a reflex action

128
Q

What is the order of neurones in a reflex response? What does each one do?

A

Receptor- detects stimulus and creates action potential in sensory neurone
Sensory neurone- carries impulse to spinal cord
Relay neurone- connects sensory neurone with motor neurone via CNS
Motor neurone- carries response to effector

129
Q

What is the spinal cord?

A

A column of nervous tissues running up the back surrounded by the spine for protection

130
Q

What type of reflex is the knee-jerk reflex?

A

A spinal reflex

131
Q

What type of reflex is a blinking reflex?

A

A cranial reflex

132
Q

Why are reflexes important?

A

Avoid body being harmed or the severity of the damage

133
Q

Which 3 ways do reflexes increase chances of survival?

A

Involuntary
Innate
Fast

134
Q

What are the three types of muscle in the body?

A

Skeletal
Cardiac
Involuntary

135
Q

What is the role of skeletal muscle and where are they found?

A

Responsible for movement

For example biceps and triceps

136
Q

What type of muscle is cardiac muscle?

A

Myogenic muscle which means they contract without nervous stimuli

137
Q

Where is cardiac muscle found?

A

Heart

138
Q

Give 2 examples where involuntary muscle is found

A

Walls of hollow organs such as stomach and bladder

Walls of blood vessels and digestive tract

139
Q

Explain the fibre appearance in the three types of muscle

A

Skeletal- striated, tubular and multinucleated
Cardiac- specialised striated, branched, unnucleated
Involuntary- non-striated, spindle shaped, unnucleated

140
Q

Explain how each of the three types of muscles are controlled

A

Skeletal- conscious/voluntary
Cardiac- involuntary
Involuntary- involuntary

141
Q

Explain the arrangement of muscles within the three different types of muscle

A

Skeletal- regularly arranged so muscle contracts in one direction
Cardiac- cells branch and interconnect resulting in simultaneous contraction
Involuntary- no regular arrangement

142
Q

Explain the contraction speed for each of the three different types of muscles

A

Skeletal- rapid
Cardiac- intermediate
Involuntary-slow

143
Q

Explain the length of contraction for each of the three different muscle types

A

Skeletal- short
Cardiac- intermediate
Involuntary- contracted for relatively long time

144
Q

What are bundles of muscle fibres enclosed in?

A

A plasma membrane called a sarcolemma

145
Q

What is the shared cytoplasm within a muscle cell called?

A

Sarcoplasm

146
Q

What is the shared cytoplasm within a muscle cell called?

A

Sarcoplasm

147
Q

What are T tubules made up of and why are they important?

A

Parts of the sarcolemma folded inwards

Spread electrical impulse throughout sarcoplasm

148
Q

What is the name of the specialised endoplasmic reticulum in the muscle cell? What is its role?

A

Sarcoplasmic Reticulum

Contains calcium ions required for muscle contraction

149
Q

What are myofibrils?

A

Long cylindrical organelles made of protein which are specialised for contraction

150
Q

How are myofibrils arranged?

A

Lined up in parallel

151
Q

What two protein filaments make up myofibrils?

A

Actin

Myosin

152
Q

Describe the structure of actin

A

Two polypeptide strands twisted around each other

Thinner filament

153
Q

Describe the basic structure of myosin

A

Long rod shaped fibres with bulbous heads that project to one side

154
Q

Why do myofibrils have a striped appearance?

A

Alternating bands of light and dark

155
Q

How do light bands form?

A

Areas where actin and myosin do not overlap

156
Q

What is the alternative name for light bands?

A

I bands

157
Q

How do dark bands form?

A

Presence of thick myosin filaments, edges particularly dark due to overlap with actin

158
Q

What is the alternative name for dark bands?

A

A bands

159
Q

What is the sarcomere?

A

Distance between two Z lines

160
Q

What happens to a sarcomere when a muscle contracts?

A

Shortens

161
Q

What is the Z line?

A

The line found at the centre of each light band

162
Q

What is the H zone?

A

The area in the centre of each dark band where only myosin filaments are present

163
Q

What happens during contraction of a muscle?

A

Myosin filaments pull actin filaments towards the centre of the sarcomere

164
Q

What is the result of muscle contraction on the bands/zones?

A

Light band decreases in size
The Z zones become closer together reducing the length of the sarcomere
H zone becomes narrower

165
Q

Explain how changes in the sarcomere cause bone movement

A

Simultaneous contraction of sarcomeres cause the contraction of myofibrils and muscle fibres
Causes enough force on the bone to cause movement

166
Q

Describe the structure of a myosin filament

A

Tails arranged aligned to create myosin filament
Globular heads present which are hinged so can move back and forward
Binding site for actin and ATP

167
Q

What is the structure of actin?

A

Actin have binding sites for myosin

168
Q

What are the binding site for myosin blocked by?

A

Tropomyosin which is held in place by troponin

169
Q

What happens between actin and myosin when a muscle is in resting state?

A

Nothing
The myosin binding site is blocked
Can’t bind to myosin so there is no movement
Can’t slide over each other

170
Q

What is a neuromuscular junction?

A

Where a motor neurone and a skeletal muscle meet

171
Q

Describe the process of events that occurs when an action potential reaches a neuromuscular junction

A

Stimulates calcium ion channels to open
Calcium ions diffuse into synaptic knob
Synaptic vesicles fuse with presynaptic membrane
Acetyl choline is released into synaptic cleft by exocytosis and diffuses across synapse
Acetylcholine binds to sarcolemma which opens the sodium ion channels and causes depolarisation
Acetylcholine is broken down by acetylcholinesterase which prevents the muscle being over stimulated

172
Q

Explain the interaction of myosin and actin during muscle contraction

A

1) Tropomyosin molecule prevents myosin head from attaching to the binding site on the actin molecule
2) Calcium ions released from endoplasmic reticulum cause tropomyosin molecule to pull away from the binding site on the actin molecule
3) Myosin head now attaches to binding site on actin filament
4) Head of myosin changes angle, moving the actin filament. ADP is released.
5) ATP molecule fixes to myosin head, causing it to detach from actin filament
6) Hydrolysis of ATP to ADP by myosin provides energy for myosin head to resume its normal position
7) Head of myosin reattaches to a binding site further along the actin filament and cycle is repeated

173
Q

What are the three ways that ATP is generated?

A

Aerobic respiration
Anaerobic respiration
Creatine phosphate

174
Q

Where is most of the ATP in muscle cells produced from?

A

Regenerated from ADP using oxidative phosphorylation

Biology OCR A A level (17 decks)

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