Neuronal Coordination Flashcards
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
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
3
Q
What are electrical responses made via?
A
Neurones
4
Q
What are chemical responses made via?
A
Hormones
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
6
Q
Define ‘homeostasis’
A
Maintenance of a constant internal environment
7
Q
How does cell signalling work?
A
A cell releasing a chemical which has an effect on another cell called a target cell
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
9
Q
What are stimulus?
A
Changes in internal and external environments that a nervous system detects
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
11
Q
What are the 3 main parts of a neurone?
A
Cell body
Dendrons
Axons
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
13
Q
What are neurotransmitters?
A
Chemicals used to pass signals from one neurone to the next
14
Q
What are dendrons?
A
Short extensions from the cell body which are responsible for transmitting electrical impulses towards the cell body
15
Q
What is the role of axons?
A
Singular, elongated nerve fibres that transmit impulses away from cell body
16
Q
What is the structure of an axon?
A
A cylindrical fibre with a narrow region of cytoplasm surrounded by plasma membrane
17
Q
What are the 3 main types of neruone?
A
Sensory neurone
Motor neurone
Relay neurone
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
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
20
Q
What are relay neurones?
A
Neurones that transmit signals between neurones
21
Q
What is the structure of relay neurones?
A
Short axons and short dendrons
22
Q
What are motor neurones?
A
Neurones that transmit impulses from a motor/sensory neurone to an effector.
23
Q
What is the structure of a motor neurone?
A
A long axon and many short dendrites
24
Q
What is the typical pathway an electrical impulse follows?
A
Receptor Sensory neurone Relay neurone Motor neurone Effector cell
25
How do myelin sheaths form?
Schwann cells produce layers of membrane which lay down a double phospholipid bilayer every time they grow. This creates a myelin sheath.
26
What is the role of myelinated sheaths?
Insulating layer
| Conduct electrical impulses at a much faster speed
27
What is the node of Ranvier?
Small gap(1-3mm) between adjacent Schwann cells
28
How do electrical impulses travel on myelinated neurones?
Electrical impulse 'jumps' from one node to the next
| Faster
29
How do electrical impulses travel on unmyelinated neruones?
Transmits continuously along nerve fibre
30
What is the role of a sensory receptor?
Convert a stimulus they detect into a nerve impulse
31
Explain process from sensory receptor to the effector
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
32
What are the two main features of a sensory receptor?
Specific to a single type of stimulus
| Act as a tranducer
33
What is a tranducer?
Something that converts a stimulus into a nerve impulse
34
What is the name of a nervous impulse produced by a sensory receptor?
Generator potential
35
What do Pacinian corpuscles detect?
Mechanical pressure
36
Where are Pacinian corpuscles located?
Deep within skin
Fingers and soles of feet
Joints to know which joints are changing direction
37
Explain the structure of a Pacinian corpuscle
End of sensory neurone within the centre of corpuscle
| Surrounded by layers of connective tissue with viscous gel between
38
What specific structure is present in the Pacinian corpuscle? What is its role?
Sodium ion channel
| Responsible for transporting sodium ions across the membrane
39
What is present in the neurone ending of a Pacinian corpsucle?
A stretch mediated sodium channel
40
Give one specific feature of a stretch mediated sodium channel
When the channel changes shape it also changes in permeability to sodium
41
Explain how a Pacinian corpuscle converts mechanical pressure into a nervous impulse
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
42
What are the two stages that an axon membrane switches between?
Resting potential
| Action potential
43
Explain the difference in charge between the inside and outside of a membrane when a neurone is in resting potential
Outside of membrane more positively charged than the inside of the membrane
44
What word is used to describe a membrane in resting state? Why?
Polarised
| Potential difference across it
45
What is the potential difference across a membrane during resting potential?
-70mV
46
Explain the movement of sodium and potassium ions across axon
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
47
What is an electrochemical gradient?
Concentration gradient of ions
48
Explain the events that result in creation of action potential
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
49
What is the potential difference of a membrane during action potential?
+40mV
50
Define depolarisation
The change in potential difference from negative to positive
51
When does depolarisation occur?
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
52
Give an example of positive feedback within action potential
Change in charge following opening of sodium voltage-gated channels causes more sodium channels to open
More sodium ions diffuse into axon
53
What occurs within the axon once +40mV has been reached?
Voltage gated sodium channels shut
Voltage gated potassium channels open
Membrane more permeable to potassium ions
54
How does repolarisation occur?
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
55
What is hyperpolarisation?
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
56
What is a nerve impulse?
An action potential that starts at one end of the neurone and is propagated along the axon to the other end of the neurone
57
How does a wave of depolarisation occur?
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
58
What is the refractory period?
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
59
What is the importance of the refractory period?
Prevents propagaiton of an action potential backwards along an axon
Prevents overlap- ensures they are unidirectional
60
What is saltatory conduction?
Sodium ions passing through long circuits from one Node of Ranvier to another in a 'jumping' motion
61
Why is saltatory conduction more efficient?
Faster
Less channels have to open
Repolarisation uses ATP so doing this less reduces use of ATP
62
What are three factors which affect speed at which action potential travels?
Axon diameter
Temperature
Myelination
63
How does axon diameter affect speed at which action potential travels?
Bigger the axon diameter= faster impulse
| Less resistance to flow of ions in cytoplasm
64
How does temperature affect speed at which action potential travels?
Higher temperature=faster
Ions diffuse faster
Only to 40 as protein channels denature
65
What is the all or nothing principle?
The nerve impulse has to reach the threshold value to initiate an action potential
66
What affect does size of stimulus have on action potentials?
Increases frequency of action potential but not size
67
What is a synapse?
The junction between two neurones or a neurone and an effector
68
What is the synaptic cleft?
The gap which separates the axon of one neurone from the dendrite to the next neurone
69
What is the presynaptic neurone?
The neurone along which the impulse has arrived
70
What is the postsynaptic neurone?
Neurone that receives the neurotransmitter
71
What is the synaptic knob?
The swollen end of the presynaptic neurone
72
What are the key features of the synaptic knob?
Mitochondria and large amounts of endoplasmic reticulum to enable it to manufacture neurotransmitters
73
What is the role of the presynaptic vesicle?
Vesicles fuse with eh presynaptic membrane and release contents into the synaptic cleft
74
What are the neurotransmitter receptors?
Receptor molecules which the neurotransmitter binds to in the postsynaptic membrane
75
What are the two types of neurotransmitter?
Excitatory and inhibitory
76
How do excitatory neurones work?
Neurotransmitters result in depolarisation of the postsynaptic neurone. Active potential occurs if threshold is reached
77
Give an example of an excitatory neurone
Acetlycholine
78
How do inhibitory neurones work?
Neurotransmitters result in the hyperpolarisation of the postsynaptic membrane. Prevents an action potential being triggered.
79
Give an example of an inhibitory neurone
GABA
80
Explain the process of synaptic transmission
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
How are neurotransmitters released from the postsynaptic neurone?
Removed via enzymes
| Some enzymes release neurotransmitter from receptor
82
Why is it important that neurotransmitters are released once they have been used?
To ensure that the stimulus is not maintained and another stimulus can arrive
83
What is a cholinergic synapse?
Any synapse that uses the neurotransmitter acetlycholine
84
What is acetylcholine broken down into?
Choline and ethanoic acid (acetyl)
85
Explain the process of acetyl choline being broken down
Acetylcholinesterase hydrolyses acetylcholine into choline and ethanoic acid
Products taken back to presynaptic knob where they can be reformed
86
What are the 3 main roles of a synapse?
Unidirectional
Allow a single stimulus to cause a number of simultaneous responses
Many stimuli can produce one response
87
Define summation
The building up of a specific neurotransmitter to sufficiently reach the threshold which will trigger an action potential
88
What are the two types of summation?
Spatial
| Temporal
89
Explain how spatial summation occurs
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
Explain how a temporal summation occurs
Single presynaptic neurone releases neurotransmitter as a result of an action potential occurring frequently
91
What 2 structural systems is the Mammalian nervous system organised into?
Central nervous system
| Peripheral nervous system
92
What is in the central nervous system?
Brain
| Spinal cord
93
What is in the peripheral nervous system?
Neurones that connect CNS to the rest of the body
| sensory and motor
94
What 2 functional systems is the nervous system organised into?
Somatic nervous system
| Autonomic nervous system
95
What is the somatic nervous system?
A system under conscious control for voluntary actions
96
Where does the somatic nervous system carry impulses to?
The body muscle's
97
What is the autonomic nervous system?
A system that works constantly that is under subconscious control
98
Where does the autonomic system carry impulses to?
Glands, smooth muscle and cardiac muscles
99
What is the autonomic system subdivided into?
Sympathetic and parasympathetic
100
What is the difference between the sympathetic and parasympathetic systems?
Sympathetic is involved with an increase
| Parasympathetic is involved with a decrease
101
What two structures protect the skull?
The brain and the mengines
102
What are the names of the 5 main areas of the brain?
```
Cerebrum
Cerebellum
Medulla oblongata
Hypothalamus
Pituitary gland
```
103
What does the cerebrum control? Give 4 examples
Controls voluntary actions
| Eg. learning, memory, personality and conscious thought
104
What does the cerebellum control? Give 3 examples
Controls unconscious function
| Eg. posture, balance and non-voluntary movement
105
What does the medulla control?
Used in autonomic control
| Eg, heart rate and breathing rate
106
What does the hypothalamus control?
Regulatory centre for temperature and water balance
107
What is the role of the pituitary gland?
Stores and releases hormones that regulate many body functions
108
What are the 3 ways that brains are imaged?
Autopsies
MRI
CT scan
109
How are active areas of the brain identified during an MRI?
Increased blood flow in the area
110
How does the cerebrum process information?
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
Why is important that the cerebrum has a large surface area?
Increases capacity for complex activity
112
Where do the most sophisticated processes occur?
Frontal and prefrontal lobe of the cerebral cortex
113
Explain the substructures of cerebrum
Two hemispheres called cerebral hemispheres
| Outer layer of cerebral hemispheres called a cerebral cortex
114
What occurs at the base of the brain?
Impulses from each side of the body cross over so left hemisphere receives impulses from the right side of the body
115
What is the size of the sensory area in cerebrum proportional to?
The relative number of receptor cells present in the part of the body
116
What is the size of the motor area in cerebrum proportional to?
Relative number of motor endings
117
Which region controls movement in the cerebrum?
Primary motor cortex located at back of the frontal lobe
118
How does the cerebellum process information?
Receives information from organs of balance and from muscles and tendons, relays information to cerebral cortex which is involved with motor control
119
What are the two centres present in the hypothalamus?
Parasympathetic and sympathetic nervous system
120
What are the three main functions of the hypothalomus?
Controlling complex patterns of behaviour
Monitoring composition of blood plasma
Producing hormones
121
Where is the pituitary gland located?
Found at base of hypothalamus
122
What are the two sections of pituitary gland?
Anterior pituitary
| Posterior pituitary
123
What does the anterior pituitary gland do?
Produces 6 hormones including FSH
124
What does the posterior pituitary gland do?
Stores and releases hormones produced by hypothalamus such as ADH
125
What is reflex action?
A response to a situation without conscious thoughT
126
Define a reflux
An involuntary response to a sensory stimulus
127
What is the reflex arc?
Pathway of neurones involved in a reflex action
128
What is the order of neurones in a reflex response? What does each one do?
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
What is the spinal cord?
A column of nervous tissues running up the back surrounded by the spine for protection
130
What type of reflex is the knee-jerk reflex?
A spinal reflex
131
What type of reflex is a blinking reflex?
A cranial reflex
132
Why are reflexes important?
Avoid body being harmed or the severity of the damage
133
Which 3 ways do reflexes increase chances of survival?
Involuntary
Innate
Fast
134
What are the three types of muscle in the body?
Skeletal
Cardiac
Involuntary
135
What is the role of skeletal muscle and where are they found?
Responsible for movement
| For example biceps and triceps
136
What type of muscle is cardiac muscle?
Myogenic muscle which means they contract without nervous stimuli
137
Where is cardiac muscle found?
Heart
138
Give 2 examples where involuntary muscle is found
Walls of hollow organs such as stomach and bladder
| Walls of blood vessels and digestive tract
139
Explain the fibre appearance in the three types of muscle
Skeletal- striated, tubular and multinucleated
Cardiac- specialised striated, branched, unnucleated
Involuntary- non-striated, spindle shaped, unnucleated
140
Explain how each of the three types of muscles are controlled
Skeletal- conscious/voluntary
Cardiac- involuntary
Involuntary- involuntary
141
Explain the arrangement of muscles within the three different types of muscle
Skeletal- regularly arranged so muscle contracts in one direction
Cardiac- cells branch and interconnect resulting in simultaneous contraction
Involuntary- no regular arrangement
142
Explain the contraction speed for each of the three different types of muscles
Skeletal- rapid
Cardiac- intermediate
Involuntary-slow
143
Explain the length of contraction for each of the three different muscle types
Skeletal- short
Cardiac- intermediate
Involuntary- contracted for relatively long time
144
What are bundles of muscle fibres enclosed in?
A plasma membrane called a sarcolemma
145
What is the shared cytoplasm within a muscle cell called?
Sarcoplasm
146
What is the shared cytoplasm within a muscle cell called?
Sarcoplasm
147
What are T tubules made up of and why are they important?
Parts of the sarcolemma folded inwards
| Spread electrical impulse throughout sarcoplasm
148
What is the name of the specialised endoplasmic reticulum in the muscle cell? What is its role?
Sarcoplasmic Reticulum
| Contains calcium ions required for muscle contraction
149
What are myofibrils?
Long cylindrical organelles made of protein which are specialised for contraction
150
How are myofibrils arranged?
Lined up in parallel
151
What two protein filaments make up myofibrils?
Actin
| Myosin
152
Describe the structure of actin
Two polypeptide strands twisted around each other
| Thinner filament
153
Describe the basic structure of myosin
Long rod shaped fibres with bulbous heads that project to one side
154
Why do myofibrils have a striped appearance?
Alternating bands of light and dark
155
How do light bands form?
Areas where actin and myosin do not overlap
156
What is the alternative name for light bands?
I bands
157
How do dark bands form?
Presence of thick myosin filaments, edges particularly dark due to overlap with actin
158
What is the alternative name for dark bands?
A bands
159
What is the sarcomere?
Distance between two Z lines
160
What happens to a sarcomere when a muscle contracts?
Shortens
161
What is the Z line?
The line found at the centre of each light band
162
What is the H zone?
The area in the centre of each dark band where only myosin filaments are present
163
What happens during contraction of a muscle?
Myosin filaments pull actin filaments towards the centre of the sarcomere
164
What is the result of muscle contraction on the bands/zones?
Light band decreases in size
The Z zones become closer together reducing the length of the sarcomere
H zone becomes narrower
165
Explain how changes in the sarcomere cause bone movement
Simultaneous contraction of sarcomeres cause the contraction of myofibrils and muscle fibres
Causes enough force on the bone to cause movement
166
Describe the structure of a myosin filament
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
What is the structure of actin?
Actin have binding sites for myosin
168
What are the binding site for myosin blocked by?
Tropomyosin which is held in place by troponin
169
What happens between actin and myosin when a muscle is in resting state?
Nothing
The myosin binding site is blocked
Can't bind to myosin so there is no movement
Can't slide over each other
170
What is a neuromuscular junction?
Where a motor neurone and a skeletal muscle meet
171
Describe the process of events that occurs when an action potential reaches a neuromuscular junction
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
Explain the interaction of myosin and actin during muscle contraction
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
What are the three ways that ATP is generated?
Aerobic respiration
Anaerobic respiration
Creatine phosphate
174
Where is most of the ATP in muscle cells produced from?
Regenerated from ADP using oxidative phosphorylation
