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nervous system Flashcards

1
Q

whats the difference between hydra and humans in cns or nerve net

A

hydra- nerve net
human-cns

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2
Q

whats the difference between the hyra and human is type of nerve cell present

A

hydra- one type of nerve cell
human- sensory, motor, relay

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3
Q

whats the difference between the hyra and human in length of process

A

hydra- short
human- long

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4
Q

whats the difference between the hyra and human in presence of myelin insulation

A

hydra- none
human- yes but myelinated and non myelinated present

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5
Q

whats the difference between the hyra and human in conduction speed

A

hydra- slow
human- fast

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6
Q

whats the difference between the hyra and human in direction of impulse from point of stimulation

A

hydra- both directions
human- one way

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7
Q

whats the difference between the hyra and human in no. of stimuli that can be detected by sensory recptors

A

hydra-limited
human- various dtimuli

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8
Q

whats the difference between the hyra and human in no. of effectors

A

hydra- small number
human- skeletal muscle/gland

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9
Q

what is a hydra

A

a multicellular, microscopic animal that lives in freshwater

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10
Q

What is a nerve net

A

Made of only one type of nerve cell with short extensions joined to each other and branching in a umber of different directions

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11
Q

Function of nervous system

A

Detects changes inside the body or in local environment
Neurones process and store information
Detects a stimulus and initiates a response

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12
Q

What are the parts of the human nervous system

A
  1. Central nervous system (CNS)- comprised of the brain and spinal cord- protected by the meninges (protective membrane)
    2.1. Peripheral nervous system (PNS)- comprised of somatic nervous system- nerve that originate in the brain or spinal cord- included sensory neurones and motor neurones
    2.2 the automatic nervous system- unconscious control of organs eg heart beat/digestion
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13
Q

What is the sensory neurone

A

Carries nerve impulses from receptor cells (in sense organs) to coordinator (eg CNS)

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14
Q

What is a relay neurone

A

Connector/intermediate neurones
Lie in the CNS and receive impulses from the sensory neurones and send impulse to motor neurones

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15
Q

What is the motor neurone

A

These carry impulses from the coordinator (CNS) to effector organs (muscles or glands)
Effector bring out response
Eg muscle contraction or hormone secretion

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16
Q

What parts are of the motor neurone

A

Dendrite
Axon
Schwann cells
Nodes of ranvier
Cell body

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17
Q

What is the dendrite function

A

The extensions which carry the impulse towards the cell body

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18
Q

What is the axon function

A

Long cytoplasmic extensions which transmit impulses away from the cell body

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19
Q

What is the Schwann cells function

A

Cells which surround neurones and insulate them

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20
Q

What is the myelin sheath function

A

Grow around the axons to form this multilayer fatty sheath
Act as an electrical insulator that speeds up transmission along the axon

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21
Q

What is the nodes of ranvier function

A

Areas along the axon where the myelin sheath is missing

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22
Q

What is the cell body function

A

Part of the neurone which contains the nucleus, RER, mitochondria and other cell organelles

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23
Q

What is a reflex

A

A rapid, involuntary response to a stimulus (doesn’t involve conscious/brain)

24
Q

What is the reflex arc

A

Pathway travelled by the nerve impulse during a reflex action

25
Basic reflex arc process
- arrival of stimulus and actioning a receptor - activation of sensory neurone - information processing in CNS - activation of motor neurone - response of effector
26
Process of reflex arc
- sensory neurones enter spinal cord via dorsal root - the integration centre involves one synapse (monosynaptic reflex) in grey matter of spinal cord - sensory neurone synapses with a relay neurone in the grey matter of spinal cord releases a neurotransmitter which generates an action potential in relay neurone
27
What is a nerve impulse
The movement of electrical impulse into and out of the axon membrane Based on sodium ions and potassium ions across the membrane
28
What 4 types of transit proteins do axon membranes contain
- a sodium ions/potassium ions pump which requires ATP - voltage-gated sodium channels - voltage- gated potassium channels - potassium channels (always open)
29
What is the resting potential
The potential difference between the inside and outside of membrane when a nerve impulse is not being conducted
30
Action potential- resting potential
At -70mv as 3 sodium ions leave through the na/k pump and 2 k ions enter using an ATP molecule to activate pump This results in a negative charge
31
What is action potential- depolarisation
The na voltage gate channel opens to allow na ions to rapidly enter axon to increase charge to +40mv
32
What is action potential- repolarisation
The high positive charge causes the k voltage gated channel to open. An outflux of k ions, overall reduce the charge of the axon Quick action so the amount of k ions to leave is large, reducing to -90mv
33
What is action potential- hyperpolarisation
The voltage gated k channels close and the na/k pump restarts and restores the resting potential. The membrane is now polarised again
34
What is the threshold stimulus
One that is great enough to cause depolarisation of the axon membrane and therefore start off an action potential in the neurone
35
What is the all or nothing law
If the intensity of the stimulus exceeds the threshold wavelength and cause depolarisation, the action potential generated is always the same size and strength and doesn’t vary with size or strength of stimulus above the threshold But the greater the stimulus above threshold values, the greater the frequency of the action potentials along the axon
36
What is the refraction period
After an action potential, the voltage-gated sodium channels are inactivated for a short time and cannot open to allow influx of sodium ions into the membrane
37
What does the refractory period prevent
- an action potential being generated in opposite direction - a second action potential being generated too close to the first- it limits the frequencies of action potentials along neurone
38
What are factors that affect the speed of nerve impulse
Myelination Diameter of axon Temperature
39
How does myelination affect the speed of the nerve impulse
It acts as an electrical insulator and stops ions moving in and out of axon
40
How does diameter of axon affect the speed of the nerve impulse
Te greater the diameter of axon, the lower the resistance to ion flow so the greater speed of transmission
41
How does temperature affect the speed of the nerve impulse
As temp increased to 40 degrees, speed of transmission increase because generation of impulse involves active transport and requires ATP from respiration Anything that speeds up respiration rate also speeds up transmission of nerve impulse
42
Process of synaptic transmission
1. Action potential has already happened 2. Ca voltage-gated channels open 3. Ca influx 4. The neurotransmitter vesicle fuses with the presynaptic membrane 5. Release of neurotransmitter into the cleft and diffuse 6. Neurotransmitter attaches to the ligand gated na channel 7. The ligand gate na channel opens, allowing an influx of na 8. This causes the post synaptic neurone to become more positive- returning action potential to resting state
43
What is acetylcholinesterase
An enzyme which hydrolyses acetylcholine in the synaptic cleft into choline and ethanoic acid These molecules diffuse back across the synaptic cleft and ATP is used to re-form neurotransmitter molecules and store them in vesicles
44
What’s the function of synapses
1. They transmit impulses between neurones. 2. They make sure that impulses pass in one direction only. This is because the vesicles containing the transmitter are only in the presynaptic neurone and the receptor molecules are only on the postsynaptic membrane. 3. They allow acclimatisation- after repeated stimulation, a synapse might run out of the neurotransmitter, i.e. the synapse is 'fatigued'. This allows them to filter out low level stimuli (unimportant) such as a bad smell or background noise. 4. They allow summation
45
What is temporal summation
A post synaptic neurone may only be stimulated if there are frequent action potentials in presynaptic membrane single presynapic nuerone releases nuerotransmitters repeatidly
46
What is spatial summation
A post synaptic neurone may only be stimulated if several pre synaptic neurones receive stimulation multiple neurones realease nuerotransimitters onto a single presynapic nuerone
47
What are excitatory drugs
Stimulus the nervous system by creating more action potentials
48
What are inhibitory drugs
Inhibit nervous system by reducing the number of action potentials produced
49
What happens if a drug is taken continuously
Synapses may adapt If drug blocks receptors, new receptor may be made to make up for old ones This means more of drug has to be taken for the same effect- tolerance to the drug
50
What is an agonist
A substance that binds to the receptor and activates it, like the normal neurotransmitter
51
What is an antagonist
A substance that binds to the receptor but doesn’t activate it, it blocks the normal transmitter
52
How do drugs effect the releases of neurotransmitter
- botulin toxin- prevents releases of neurotransmitter controlling voluntary muscles causing muscle weakness, paralysis and death - amphetamine- increases release of neurotransmitter, normally associated with stress, prodding high blood pressure, increasing HR and sweating/insomnia
53
How do drugs effect by blinding to receptor
- curare- blocks receptor on voluntary muscles, leading to flaccid paralysis and death - beta blockers- block receptors for noradrenaline, decrease HR and blood pressure, treats hypertension
54
How do drugs effect by removal of transmitter
- cocaine- slows down removal of noradrenaline causing high blood pressure, pupil dilation, constipation - anticholinesterases (eg sarin)- prevents metabolism neurotransmitter at voluntary muscles, causing spastic paralysis, death by suffocation
55
What are organophosphorus insecticides
Drug that blocks/inbits the enzyme acetlycholinesterase This prolongs the effects of acetylcholine which remains in the synaptic cleft and causes repeated depolarisation of post-synaptic neurone - results in repeated firing action potentials along post synaptic neurones If this occurs in neuromuscular unction, repeated contractions o the muscles will occur, results in depletion of ATP then paralysis and death
56
What are psychoactive drugs
Act on the CNS where they alter brain function, causing temporal changes in perception, mood, consciousness and behaviour
57
How salutatory propagation increases the rate of transmission of nerve impulse
Because the axon has a high resistance to the electrical impulse which makes the speed of conduction too slow, an alternative mechanism takes over Its called ‘salutatory conduction’ in which the electrical impulse jumps from one node of ranvier to the next while achieved required conduction velocity

biology- component 3 (5 decks)

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