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Module 5.1/5.3 Communication And Homeostasis/ Neuronal Communication > Neuronal Communication > Flashcards

Neuronal Communication Flashcards

1
Q

What is a stimulus

A

A change in the environment

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2
Q

Name and describe the two types of stimuli

A
  • external environment stimuli= seasonal temperature change or the appearance of a prey or predator
  • internal environment stimuli= a drop in body temperature or blood sugar
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3
Q

Give 4 examples of stimuli

A
  • light
  • water
  • change in temperature
  • predators
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4
Q

Explain the events after a change in stimulus is detected

A

Stimulus —> Receptor —> Comminucation system —> Effector —> Response

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5
Q

What are examples of communication systems

A
  • CNS
  • Hormones
  • Sensory, relay or motor neurons
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6
Q

What are features of a good communication system

A
  • covers the whole body
  • enable cells to communicate with each other
  • enable a specific response
  • enable rapid communication
  • enable both short-term and long term responses
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7
Q

What is Homeostasis

A

Maintenance of constancy of the internal environment (tissue fluid)

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8
Q

What type of feedback do most homeostatic mechanisms involve

A

Negative feedback

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9
Q

What is negative feedback

A

An automatic response to a stimulus to counteract a change

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10
Q

Describe the mechanism a negative feedback loop would take

A

1) change in stimulus away from optimum
2) receptor detects change
3) communication system informs the effector
4) effector reacts to reverse the change
5) returns to optimum conditions
6) back to optimum conditions

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11
Q

What is positive feedback

A

An acceleration to a response
-> it is normally harmful but can be good

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12
Q

Describe the mechanism of a positive feedback loop

A

1) change away from optimum condition
2) receptors detect the change
3) communication systems informs the effector
4) effector reacts to increase change
5) change away from optimum is maintained

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13
Q

What is an example of harmful positive feedback

A
  • breathing pure oxygen under pressure raises respiratory rate in tissue
  • which then produces more CO2, raising the heart and breathing rate
  • then sending more O2 which further raises respiratory rates producing more CO2 leading to hyperventilation
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14
Q

What is an example of useful positive feedback

A

during birth:
- dilation of the cervix stimulates the anterior pituitary gland to secrete the hormone oxytocin
-oxytocin stimulates increased urine concentration which stretches the cervix more, triggering more oxytocin release

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15
Q

Name the 11 parts of the skin

A

1) Hair
2) Melanocytes
3) Sebaceous gland
4) Epidermis
5) Sweat gland
6) Blood vessels
7) Hair follicle
8) Hair erector muscle
9) Dermis
10) Pacinian corpuscle
11) Subcutaneous tissue

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16
Q

Define a receptor

A

A cell or group of cells that detect a change from the stimulus

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17
Q

Define an effector

A

Muscles and glands that produce a specific response to a detected stimulus

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18
Q

What is the system of regulating temperature called

A

Thermoregulation

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19
Q

Why do we need to control our body temperature

A
  • all metabolic reactions are enzyme- catalysed
  • at low temperatures = molecules have less kinetic energy, so there are slower and less frequent collisions so the rate or reaction drops
  • at high temperature = the enzymes lose their tertiary structure as hydrogen bonds are broken and become less efficient and eventually become denatured
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20
Q

Why is maintaining core body temperature important

A
  • as this is where most vital organs can operate
  • allows enzymes to work at their optimum rate
  • peripheral temp may be allowed to vary in extreme conditions, but significant changes in core temp is dangerous
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21
Q

What is the body’s core temperature

A

Around 36.5 - 37.5 degrees celsius

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22
Q

What is peripheral temperature

A

The temperature of the skin or the body’s surface level

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23
Q

Define hyperthermia

A

When the body’s temperature is too high

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24
Q

What part of the body is most affected by hyperthermia

A
  • the brain
  • cell membrane (damaged)
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25
Q

Define hypothermia

A

When the body’s temperature is too low

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26
Q

What part of the body is most affected by hypothermia

A
  • the kidneys
  • blood circulatory system
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27
Q

Define endotherms

A

Animals that can control their own body temperature

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28
Q

Define ectotherms

A

Animals that cannot control their own body temperature

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29
Q

How do endotherms control their body temperature

A
  • by balancing heat gain against heat loss
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30
Q

What are the main sources of heat gain for ectotherms

A

The environment, they generate comparatively little heat inside their bodies

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31
Q

What are the main sources of heat gain for endotherms

A

Their own internal metabolism

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32
Q

What are the behavioural responses to thermoregulation in ectotherms

A

WARM UP:
- basking in the sun
- orientation towards heat (sunbathing)
- extend body parts
- pressing bodies against the ground
-contracting muscles/ vibrating wings

COOL DOWN:
- seek shade
- orientation away from heat
- press against cool ground
- minimise movements

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33
Q

What are the physiological responses to thermoregulation in ectotherms

A
  • dark colours
  • alert heart rate
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34
Q

What are the advantages of being an ectotherms

A
  • don’t use up their energy to keep warm. THEREFORE:
  • less of their food is used in respiration
  • more of their energy can be used for growth
  • they need to find less food
  • they can survive for longer periods of time without food
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35
Q

What are the disadvantages of being an ectotherm

A
  • less active in cooler temperatures
  • therefore more at risk of predators
  • cannot take advantage of available food if cold
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36
Q

What are examples of ectotherms

A
  • reptiles
  • fish
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37
Q

What are examples of endotherms

A
  • Humans (and other mammals)
  • Birds
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38
Q

How do endotherms generate most of their body heat

A

Internally via respiration of food molecules

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39
Q

How do endotherms regulate their temperature

A

By controlling how quickly they lose it

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40
Q

What are the advantages of being an endotherm

A
  • constant body temperature regardless of external environment
  • activity possible in cooler temperatures
  • able to inhabit cooler parts of the world
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41
Q

What are the disadvantages of being an endotherm

A
  • more food is required
  • significant part of energy intake used to maintain body temperature
  • less energy from food can be used for growth
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42
Q

How is temperature controlled in the body

A
  • it is monitored by the body’s “thermostat” the thermoregulatory centre in the hypothalamus
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43
Q

what in the skin does the hypothalamus use to control heat

A

1) Sweat glands in skin
2) hair on skin
3) capillaries near skin surface

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44
Q

Describe what would happen to the sweat glands when it is too hot

A
  • They would secrete sweat
  • the water has a specific heat capacity, therefore heat escapes the body and is converted into evaporation of sweat
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45
Q

Describe what happens to the sweat glands when it is too cold

A

They become inactive

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46
Q

What happens to the hairs on the skin when it is too hot

A
  • they relax so the hair is flat against the skin
  • so the air can freely circulate over the skin, cooling it down
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47
Q

Describe what happens to the hairs on the skin when it is too cold

A
  • they contract ( with help from the hair erector muscle) so the hairs stand
  • this traps air over the skin which acts as a layer of insulation
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48
Q

Describe what happens to the blood capillaries under the surface of the skin when it is hot

A
  • vasodilation of capillaires
  • which increases the surface area
  • so heat from the blood is transferred out of the body and through the skin more efficiently
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49
Q

What happens to the blood capillaries under the surface of the skin when it is cold

A
  • vasoconstriction of the capillaries
  • reducing heat loss through the skin
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50
Q

What is a physiological control for the skin when it is too hot

A
  • sweat is secreted from the sweat glands onto the skin surface
  • hairs and feathers lie flat to allow for air to circulate freely over the skin
  • vasodilation
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51
Q

What is the physiological control for the skin when it is too cold

A
  • less sweat secreted
  • hairs and feather contract to trap air and act as an insulating layer
  • vasoconstriction of capillaries so less heat is lost
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52
Q

What is the physiological control for the gaseous exchange systems when it is too hot

A
  • pant, increasing evaporation of water from the surface of the lungs and airways
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53
Q

What is the physiological control for the gaseous exchange systems when it is too cold

A
  • less panting, so less heat is lost
54
Q

What is the physiological control for the liver when it is too hot

A
  • less respiration takes place, so less heat is released
55
Q

What is the physiological control for the liver when it is too cold

A
  • increased respiration in the liver cells, more energy from food is converted into heat
56
Q

What is the physiological control for the skeletal muscles when it is too hot

A
  • fewer contractions, so less heat is released
57
Q

What is the physiological control for the skeletal muscles when it is too cold

A
  • Shivering (spontaneous muscle contraction), which releases heat
58
Q

What is the physiological control for blood vessels when it is too hot

A
  • vasodilation, so that more heat can be lost
59
Q

What is the physiological control for blood vessels when it is too cold

A
  • vasoconstriction, so that blood is not cooled too much- but this can lead to frostbite in extreme conditions
60
Q

What are the behavioural mechanism to maintain temperature when it is too hot

A
  • hide away from the sun in the shade or a burrow
  • orientate body away from the sun to reduce surface area exposed to the sun
  • remain inactive and spread limbs out to enable greater heat loss
  • wet skin to use evaporation to help cool the body
    ( cats lick themselves and elephants spray water over their bodies)
61
Q

What are the behavioural mechanisms to maintain a temperature when it is too cold

A
  • lie in the sun
  • orientation body towards the sun to increase surface area exposed
  • move about to generate heat in the muscle, or in extreme conditions roll into a ball shape to reduce surface area and heat loss
  • remain dry
62
Q

What are sensory receptors

A

Specialised cells that can detect changes in our surroundings

63
Q

What are energy transducers

A

Something that converts one form of energy into another form of energy

64
Q

Why can sensory receptors be described as energy transducers

A

Because they ‘convert’ the energy contained in the stimulus into another form of energy, specifically into some sort of membrane potential

65
Q

Describe the stimulus, sensory receptor and energy change when there is a change in light intensity

A

Stimulus: change in light intensity
Sensory receptor: rods and cones in retina of eye
Energy change: light to electrical

66
Q

Describe the stimulus, sensory receptor and energy change when there is a change in temperature

A

Stimulus: change in temperature
Sensory receptor: heat receptors in skin and hypothalamus
Energy change: thermal to electrical

67
Q

Describe the stimulus, sensory receptor and energy change when there is chemicals in food

A

Stimulus: chemicals in food
Sensory receptor: chemical receptors on tongue
Energy change: chemical to electrical

68
Q

Describe the stimulus, sensory receptor and energy change when there is a change in sound

A

Stimulus: change in sound
Sensory receptor: vibration receptors in ear cochlea
Energy change: kinetic (sound wave) to electrical

69
Q

Where are pacinian corpuscles found in

A

Mostly found in dermis of skin

70
Q

What is the pacinian corpuscle described as

A

-A pressure receptor
-The largest skin receptor

71
Q

What does the pacinian corpuscle consist of

A

-concentric rings surrounding a nerve ending

72
Q

What causes the rings to apply pressure on the sensory nerve fibre

A

A pressure stimulus like a tap

73
Q

What detects change in pressure in the pacinian corpuscle

A

The nerve fibres

74
Q

What happens as the pressure on the pacinian corpuscle becomes greater

A

The greater the frequency of the nerve impulse along the neurone

75
Q

Describe what happens when pressure is applied to the pacinian corpuscle

A

1) the detect the mechanical stimuli
2)the concentric rings (lamellae) are deformed and press on the sensory nerve endings
3) causes deformation of stretch- mediated sodium channels in the sensory neurone’s cell membrane
4) the sodium ion channels open and sodium ions diffuse into the cell
5) creating a generator potential
6) if the generator potential reaches the threshold and action potential is triggered

76
Q

What are the three types of neurones

A

1) sensory neurone
2) motor neurone
3) relay neurone

77
Q

Describe the characteristics of sensory neurones

A

-long dendron
-short axon
-impulse travels towards the cell body
-cell body in the middle
-cell body and dendrites are outside the spinal cord

78
Q

What is the function of sensory neurones

A

Carry the action potential from sensory receptor to the CNS

79
Q

Describe the characteristics of relay neurones

A

-many short dendrites
-short axon
-entirely within the spinal cord

80
Q

Describe the function of relay neurones

A

Interconnect the sensory neurone with appropriate motor neurone

81
Q

Describe the characteristics of motor neurones

A

-cell body and dendrites are within the spinal cord
-long axon
-short dendrites
-axon is outside the spinal cord

82
Q

Describe the function of motor neurones

A

Carries the action potential from the CNS to effectors (muscle or gland)

83
Q

What are features of all 3 neurones

A

-cell body containing nucleus, mitochondria and ribosomes
-nodes of ranvier (sensory and motor)
-axon
-myelin sheath made of schwann cells (sensory and motor)
-receptor (sensory)
-denrodn (sensory)
-dendrites
-muscle fibres (motor)

84
Q

What are nodes of ranvier

A

Gaps in the myelin sheath
-action potential jumps from one node to the next

85
Q

What is the jumping of impulses from one node to the next called

A

Saltatory conduction

86
Q

What does the myelin sheath do

A

Speeds up the rate of electrical impulses

87
Q

What fraction of neurones are myelinated

A

A third (1/3)

88
Q

Which neurones are described as non-myelinated neurones

A

Peripheral neurones in the CNS

89
Q

What fraction of neurones in the body and non-myelinated

A

Two thirds (2/3)

90
Q

What are the advantages of myelination

A

-can transmit action potentials more quickly compared to non-myelinated neurons (travels at 100-120 m/s)
-carry neurones from sensory receptors, to the CNS and from CNS to effectors
-carry signals over long distances
-enables rapid response to a stimulus

91
Q

What is it called when neurones are not transmitting an action potential

A

Resting potential

92
Q

What channels are used in action potential

A

Sodium channels
Potassium channels

93
Q

How many potassium ions are pumped out for every 3 sodium ions

A

2

94
Q

Describe what the membrane looks like when the cell is in resting potential

A

-sodium voltage-gated channels are kept closed
-some potassium ion channels are open, so the plasma membrane is more permeable to potassium ions than sodium ions
-potassium diffuses out of the cell
-interior of the cell is at a negative potential compared to the outside
-cell membrane is polarised

95
Q

What is the potential difference across the cell membrane at resting potential

A

-60mV

96
Q

Describe the cell at resting potential

A

-more k+ channels are open than Na+ channels
-greater concentration of sodium ions outside the cell
-greater concentration of potassium ions in the cell than on the outside

97
Q

What is resting potential

A

-when a neurone is not sending a signal
-polarised (negatively charges inside compared to the outside)

98
Q

How is resting potential maintained

A

-sodium-potassium pump pumps 3 Na+ out and 2 K+ in
-k+ leak back out because K+ channels are open
-Na+ cannot get back in because Na+ gates are closed
-also more proteins are in the axon making it more negative
-more Cl- is pumped into the axon via the chlorine pumps making inside the axon more negative

99
Q

Describe action potentials

A

1) a stimulus is detected and causes Na+ ion channels to open allowing some Na+ ions to come into the axon
2) If the amount of Na+ ions coming in passes the threshold (-50mV) it causes the Na+ voltage-gated channels to open
3) this causes more Na+ ions to move into the axon making inside the axon depolarised (more positive)
4) the action potential then reaches +40mV
5) the Na+ ion channels then close and the K+ ion channels open allowing K+ to move out the axon
6) this causes the inside of the axon to be repolarised (as it is becoming negative again)
7) then there is hyperpolariastaion where the voltage is (-70 to -80mV) this happens because the K+ ion channels are slow to close causing more K+ ions to leave the axon
8) then the axon goes back to resting potential
9) there cannot be an immediate new action potential generated due to the refractory period which is when the Na+ ion channels are closed

100
Q

Why do we have the refractory period

A

-to allows for the sodium and potassium pump to restore ions to their correct places
-allows the neurone to recover and ensures the action potential is only transmitted in one direction

101
Q

What is the model which states that a neurone must overcome threshold potential to undergo action potential

A

All or nothing principle

102
Q

Define a synapse

A

-a junction between two or more neurones

103
Q

Define a synaptic cleft

A

-a gap between the two neurones (approx. 20nm wide)

104
Q

Action potential cannot cross the synapse so how is the message continued

A

By the diffusion of neurotransmitters

105
Q

What are synapses that use acetylcholine (neurotransmitter) called

A

Cholinergic synapses

106
Q

Describe the transmission across a synapse

A

1) an action potential arrives at the synaptic bulb
2) the voltages gated calcium ion channels open
3) calcium ions diffuse into the synaptic bulb
4) the calcium ions cause the synaptic vesicles to move and fuse with the pre-synaptic membrane
5) acetylcholine is released by exocytosis
6) acetylcholine molecules diffuse across the cleft
7) acetylcholine molecules bind to the receptor sites on the sodium ion channels in the post- synaptic membrane
8) the sodium ion channels open
9) sodium ions diffuse across the post-synaptic membrane into the post-synaptic neurone
10) a generator potential/ excitatory post-synaptic potential (EPSP) is created
11) if sufficient generator potentials combine then the potential across the post-synaptic membrane reaches the threshold potential
12) a new action potential is created in the post-synaptic neurone
13) once an action potential is achieved it will pass down the post- synaptic neurone
14) acetylcholinesterase (enzyme) breaks down acetylcholine into ethanoic acid and choline
15) ethanoic acid and choline are recombined using ATP
16) acetylcholine re-enters the pre-synaptic bulb via the reuptake channel

107
Q

Why do we have synapses

A

-act as one-way valves

108
Q

Define summation

A

-where the effects of neurones can be ‘added up’ to decide whether or not impulses are triggered in the other side

109
Q

What are the two types of summation

A

1) temporal summation
2) spatial summation

110
Q

Describe temporal summation

A

-a series of action potentials from the same pre-synaptic neurone

111
Q

Describe spatial summation

A

-action potentials from different pre-synaptic neurones contribute to action potentials in post synaptic neurone

112
Q

Define excitatory post-synaptic potential

A

-a post-synaptic potential that makes the post-synaptic neuron more likely to fire an action potential

113
Q

Define inhibitory post-synaptic potential

A

-reduce the effect of summation and prevent AP

114
Q

How do synapses filter out unwanted low-level signals

A

-by not creating a new action potential if threshold isn’t met

115
Q

Fill in the blanks:
After repeated _______, a synapse may run out of _____ containing the neurotransmitter. The synapse is said to be ______ and the organism has become _______.

A

1) stimulation
2) vesicles
3) fatigued
4) habituated

116
Q

Give an example of habituation

A

Getting used to a smell or a background noise

117
Q

What are the ways in which drugs could affect a synapse

A

1) mimic the neurotransmitter
2) enhance the neurotransmitter
3) block the neurotransmitter
4) stop reuptake
5) block calcium channels

118
Q

Describe the affect of a drug when it MIMICS a neurotransmitter

A

-nicotine binds to the receptors on the post-synaptic membrane of the nicotine cholinergic synapse and as it has the same shape (mimics) acetylcholine it causes the sodium channels to open and remain open

119
Q

What is the mimicking of a neurotransmitter also called

A

-an agonistic affect

120
Q

Describe the BLOCKING effect of drugs

A

-when a drug binds to the receptors on the post-synaptic membrane and stops the neurotransmitter from binding to the receptor
E.g. prolonged exposure to nicotine blocks acetylcholine from binding to the receptors

121
Q

What is the BLOCKING effect also called

A

-an antagonistic effect

122
Q

Describe the enhancing of drugs

A

-the drug may bind to the receptors on the post-synaptic neurone and cause a bigger effect (bigger action potential) than the neurotransmitter would have created

123
Q

Describe how drugs can block the calcium channels and the affects of this

A

-drugs could bind to the calcium channels and block it so no calcium is able to pass through the channel and so the vesicles containing acetylcholine cannot be moved to the membrane and so cannot bind to the membrane and acetylcholine cannot be released to the synaptic cleft

124
Q

Describe how blocking reuptake channel works

A

-it stops the acetylcholine from being able to pass through the channel and be put back into the vesicles ready for the next action potential

125
Q

What hormones do nicotine stimulate

A

-adrenaline
-endorphin

126
Q

What is a neuromuscular junction

A

the site at which a neurone connects with muscle tissue

127
Q

Define differential membrane permeability

A

-the fact that membranes allow some ions to pass across a membrane more easily than others

128
Q

How do the neurones allow for unidirectionality

A

-the action potential is only coming from one direction
-the vesicles containing acetylcholine are only in the pre-synaptic neurone
-the receptors are only found on the post-synaptic neurone

129
Q

Define a electrochemical gradient

A

-a difference in charge across a membrane

130
Q

Define action potential

A

-peak of positive charge present in a neuron

131
Q

What is the thickness of a neuron’s main extension called

A

-axon diameter

Module 5.1/5.3 Communication And Homeostasis/ Neuronal Communication (1 decks)

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