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Neuronal Communication Flashcards

1
Q

What is a stimulus

A

A change in the environment
It can be internal (drop in body temp or blood sugar) or external (seasonal temperature change)

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2
Q

What is the stimulus - response loop

A

Stimulus > receptor > communication system > Effector > response

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3
Q

What makes a good communication system

A

-rapid response
-specific response
-covers whole body
-enables cells to communicate with each other

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4
Q

Give the differences between a neuronal and hormonal response

A

Hormonal
-endocrine
-hormones
-long term
-glands
-ADH

Neuronal
-neurones
-short term
-electrical impulse
-synapses
-short term

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5
Q

What is homeostasis

A

The maintenance of the constant internal environment

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6
Q

What is the negative feedback loop

A

Automatic response
-body at optimum condition
-changes away from optimum
-receptor detects change
-communication system informs effector
-effector reacts to reverse change
-body returns to optimum conditions

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7
Q

What is the positive feedback loop

A

It accelerates response
-at optimum condition
-receptor detects change
-communication system informs effector
-effector reacts to INCREASE change

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8
Q

What is one harmful positive feedback mechanism

A

-Breathing pure O2 under pressure raises respiratory rate in tissue
- this produces more CO2 raising heart and breathe rate
-this sends more O2 which further raises respiratory rate producing more CO2 leading to hyperventilation

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9
Q

What is one beneficial positive feedback mechanism

A

During childbirth
-dilation of cervix stimulates anterior pituitary gland to secrete hormone oxytocin
-this stimulates increased uterine contractions which stretches cervix more
-triggers more release of oxytocin

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10
Q

Why control body temperature

A

-all metabolic reactions are enzyme catalysed
-at low temperatures molecules have less Ke and so collisions are less frequent and reaction rate falls
-at high temperatures lots of collisions so enzymes lose tertiary structure and become denatured
-so it’s to keep the body temperature constant to function at their optimum rate

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11
Q

What is core temperature

A

The internal temperature of an organism (36-37.5’ in mammals)

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12
Q

Why is core temperature important

A

Because it is where most vital organs operate
Significant changes in core temperature is dangerous

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13
Q

What is peripheral temperature

A

Body’s surface temperature that can be allowed to vary in extreme conditions

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14
Q

How do animals control their body temperature

A

By balancing heat gain against heat loss

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15
Q

What is an ectotherm

A

Source of gained heat is the environment
They generate little inside their bodies

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16
Q

How does an ectotherm gain heat (behavioural responses)

A

-By basking in the sun - this is radiation
-By pressing against hot surfaces- conduction
-Contracts muscles or wings
-Turns towards sun

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17
Q

How does an ectotherm gain heat (physiological response)

A

-dark colours- absorbs sunlight
-alters heart rate- make it beat faster to increase temperature

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18
Q

How does an ectotherm cool down?

A

-seeks shade
-by convection standing away from ground lose heat currents from air
-wallowing in mud - loses heat by evaporation of water from surface of skin

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19
Q

Give advantages of ectotherm

A

-Less of their food used in respiration
-More used in growth
-Can survive long periods without food
-Do not use up energy to keep warm

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20
Q

Give disadvantages of an ectotherm

A

-less active in cooler temperatures
-cannot take advantage of food if available
-More risk of predators as can’t move in cold

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21
Q

What is an endotherm

A

main source of heat is internal -their own metabolism

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22
Q

How is temperature controlled in mammals

A

By the thermoregulatory centre in the hypothalamus

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23
Q

What does the skin do if an endotherm is too hot

A

-Sweat gland secretes fluid on surface of skin which cools them down
-hairs lie flat to reduce insulation and increase heat loss
-Vasodilation of arterioles as they’re close to surface of skin so increased heat loss

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24
Q

What does the gas exchange system do if it’s too hot

A

-some animals pant increasing evaporation of water from surface of lungs and airways

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25
What does liver do when it’s too hot for an endotherm
Less respiration takes place so less heat released
26
What does the skeletal muscles do if it’s too hot in an endotherm
Fewer contractions
27
What does the skin do if it’s too cold for an endotherm
-Less sweat secreted -Hairs and feathers erect to trapair -Vasoconstriction - blood directed away from skin surface
28
What does the gas exchange system do if it’s too cold for an endotherm
Less panting so less evaporation of heat
29
What does the liver do if it’s too cold for an endotherm
-increased respiration More energy from food turned into heat
30
What does the skeletal muscles do if it’s too cold for an endotherm
-more contractions releasing heat
31
Give advantages of an endotherm
-Constant body temperature regardless of external environment -activation possible in cooler temperature -able to inhabit cooler parts of the world
32
Disadvantages of endotherm
-more food required -less energy from food can be used for growth -significant part of energy used to maintain body temperature
33
What are sensory receptors
Specialised cells that detects change in our surroundings
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35
What is an transducer
Convert energy into electrical energy
36
What is pacinian corpuscle
A pressure receptor - found in dermis of skin -Largest skin receptor
37
How does the pacinian corpuscle carry out its function
-consists of concentric rings surrounding a nerve ending -pressure causes the rings to apply pressure on the sensory nerve fibre -nerve fibre detectsbchange in pressure -the greater the pressure the greater the frequency of nerve impulse along the neurone
38
What is the basic structure of neurones
-long - can transmit impulse over long distances -cell surface has gated ion channels -cell body that contains nucleus, mitochondria and ribosomes
39
Describe the sensory neurone
-Long dendron -Short axon -AP from sensory receptor to CNS (direction of impulse is towards cell body)
40
Describe the relay neurone
-connects sensory and motor neurone -many short dendrites -short axon -within CNS
41
describe the motor neurone
-long axon -carries AP from CNS to effectors -cell body within CNS (Direction of impulse away from cell)
42
What is Myelinated neurones
Layer of myelin sheath on neutron Gaps in the sheath are Rhodes of ranvier the AP jumps from one node to the next
43
What is non myelinated neurones
They don’t have myelinated Still associated with Schwann cells Several neurones wrapped in one loose Schwann cell AP moves along in a wave
44
What is an advantage of myelinated neurones
-transmit AP more quickly -carries signals over long distances -enables rapid response to stimulus
45
what is the process of your body detecting pain when touching a pin
-When you touch a pin it exerts a mechanical pressure on your skin -Pacinian corpuscle detects the pressure changes -Sodium ion channel widens and sodium ions diffuse in membrane -Membrane is depolarised -AP is created -AP is transmitted along neurones to CNS
46
why do you see bright light when you rub your eyes
-sensory receptors only detects one type of stimulus -Rubbing the eyes stimulates the cells in the eys - Brain doesn’t recognise the stimulus is different -So perceives the pressure as light
47
What is the resting potential
-the negative internal electrical potential (-60mv is the typical)
48
How is the resting potential achieved
Polarised- negatively charged inside than outside so have a higher concentration of NA+ ions outside the cell so there is a steep concentration gradient across the cell membrane
49
how is the resting potential maintained
-3 Na+ ions out and 2 K+ ions in
50
How is a nerve impulse generated
-sodium ion channels open -sodium diffuses into the cell -membrane depolarises (less negative thsn outside) -positive feedback causes nearby sodium ion channels to open and sodium diffuses in -potential difference reaches x+40 -sodium ions channel close and potassium channels open -potassium diffuses out making inside of cell more negative (repolarisation) -The potential difference overshoots as excess of K+ leaves making I drop below 70 resting level (hyperpolarisation) -the original potential is restored
51
what is the refractory period and what does it do
-after an AP soodium and potassium ionsare in the wrong place -So potassium-sodium pumps must restore the ions in the right place an action potential cannot happen during this
52
What is the all or nothing law
-AP only occurs if the stimulus causes enough sodium ions to meter the cell to reach the threshold level
53
Why does the AP only happen at the nodes of ranvier
Because ions cannot diffuse through the myelinated neurones- only the gaps (nodes of ranvier )
54
What is a synapse
- a junction between 2 neurones -the gap between 2 neurones is called the synaptic cleft
55
how does an AP cross the synapse
by the diffusion of a chemical called neurotransmitter
56
what is the synapses called that use acetylcholine
Cholinergic synapse
57
How is transmission across the synapse done
-an action potential arrives at the synaptic bulb -voltage gated calcium channels open -calcium diffuses into synaptic bulb -they cause the synaptic vesicles to fuse with the pre synaptic membrane -acetylcholine is released by exocytosis -it diffuses across the cleft -it binds to the receptors on the post synaptic membrane -sodium ion channels open -the sodium ions diffuse across the post synaptic membrane into the post synaptic neurone -a generator potential is created -a new AP is created in the post synaptic neurone
58
what is acetylcholinesterase
-the enzyme that breaks down acetylcholine into Ethanoic acid and choline -it recombines suing ATP
59
Why do we need synapses
-they act as a one way valve -one side has vesicles amd the other can only respond to the transmitter -therefore impulses travel only one way across a synapse
60
What is summation
Where several neurones meet and their effects can be added up to decide whether impulses are triggered or not
61
What is excitatory post synaptic potential
Not enough to cause an action potential
62
What is temporal summation
Series of AP’s from one pre synaptic neurone
63
What is spatial summation
AP’s from different pre synaptic neurones that contribute to AP in post synaptic neurone
64
What is inhibitory post synaptic potential
Reduces the effect of summation and prevents AP
65
Synapses can filter out..
Unwanted lows level signals
66
what happens after repeated stimulation
-synapse runs out of vesicles contain in the neurotransmitter -synapse is fatigued and the organism has become habituated (Habituated = getting used to a smell or noise in the background)
67
How does nicotine affect synaptic transmission
-it mimics the effect of acetylcholine at some cholinergic synapses -it binds to the receptors on the postsynaptic membrane of nicotinic cholinergic synapses, causing sodium channels to remain open -small does of nicotine acts as a stimulant -prolonged exposure blocks the effect of acetylcholine -nicotine also stimulates adrenaline and endorphin release
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Biology (12 decks)

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