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Human Systems > Nervous system > Flashcards

Nervous system Flashcards

1
Q

Where do chemical synapses occur

A

Between neurons and neurons, neurons and muscle cells, neurons and gland cells

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2
Q

What are the events at a chemical synapse

A

AP depolarises presynaptic ending​

Influx of Ca 2+ into presynaptic ending​

Vesicles migrate towards plasma membrane​

Release of transmitter into cleft (exocytosis)​

Transmitter (Tx) diffuses in cleft​

Tx binds to receptors on post-synaptic cell​

changes in post-synaptic cell

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3
Q

How can the transmitter become inactivated

A

-Reuptake into presynaptic cell
-Enzymic destruction

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4
Q

Name 3 amino acid derivative transmitters

A

-Acetylcholine
-Dopamine
-Gamma Amino Butyric Acid (GABA)

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5
Q

Name 3 peptide transmitters

A

-Enkephalins
-Endorphins
-Substance P

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6
Q

What defines the function/response of a transmitter

A

The nature of the receptors and the 2nd messengers in the post synaptic cell

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7
Q

What is an excitatory synapse

A

One with increased activity where the cell becomes depolarised (increases possibility of an action potential occuring)

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8
Q

When a cell is hyperpolarised which synapse occurs

A

Inhibitory - decreased activity (decreases the probability of an action potential occurring)

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9
Q

What occurs at an excitatory synapse

A

Transmitter causes depolarisation​
Excitatory post-synaptic potential (EPSP)​
Brings Membrane Potential nearer to firing threshold​

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10
Q

Steps which occur at an inhibitory synapse

A

Transmitter causes hyperpolarisation​
Inhibitory post-synaptic potential (IPSP)​
Takes Membrane Potential further from firing threshold​

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11
Q

Why is summation needed

A

Postsynaptic potentials are very small​
Single ones have little effect on the MP of the post-synaptic cell​
Necessary for EPSPs to add together

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12
Q

Can EPSPs and IPSPs summate

A

Yes but they will tend to cancel each other out

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13
Q

What is convergence

A

Each neuron receives many inputs from other cells

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14
Q

What is divergence

A

Each neuron synapses with many other cells

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15
Q

What is a neuromuscular junction

A

A synapse between a motor nerve and a muscle fibre
Also referred to as ‘motor end plate’
The area of ‘contact’ is greater than in a nerve-nerve synapse
The transmitter is acetylcholine

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16
Q

List the events at a neuromuscular junction

A

-AP depolarises motor nerve ending​
-Influx of Ca 2+ into nerve ending​
-Vesicles migrate towards plasma membrane​
-Release of ACh into cleft (exocytosis)​
-ACh diffuses in cleft​
-ACh binds to receptors on post-synaptic cell​
-Action potential in muscle cell  contraction​
-Transmitter (ACh) broken down by acetyl cholinesterase​
-Choline & acetate taken up by neuron ​

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17
Q

How may drugs enhance or suppress the synapse

A

By affecting:
-synthesis/storage of Tx
-the release of Tx
-action of Tx on receptor
-the second messenger system
-inactivation of Tx

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18
Q

What is ‘Botox’ used for

A

Botox (botulinum toxin) is used to paralyse facial muscles to remove wrinkles​

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19
Q

How does Botox work

A

It prevents the release of transmitter from motor nerves

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20
Q

What are neurons

A

-nerve cells present in the nervous system which are specialised for communication
-connect with each other and with other ‘excitable’ cells, e.g. muscles, glands

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21
Q

List some types of neurones

A

Purkinje cell (cerebellum)​

Spinal interneuron​

Sensory neuron (dorsal root)​

Pyramidal cell (cerebral cortex)​

Motor neuron (spinal cord)​

Bipolar cell (retina)​

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22
Q

What is a resting membrane potential

A

A potential difference that exists across the membrane of all cells

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23
Q

What is the range of the resting membrane potential

A

It is in the range 20 – 90mV, with the inside (Intercellular fluid) negative with respect to the outside (Extracellular fluid)​

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24
Q

What is voltage

A

The measure of energy potential

25
Q

Concentrations of ions in the ECF and ICF

A

ECF(mM)​ ICF(mM)​

Na+​ 145​ 15​

K+ 4​ 150​

Cl–​ 110​ 10​

26
Q

Are the concentrations of Ions within the fluids random

A

No, they are due to another variable such are conc gradients and ion channels

27
Q

Why does the resting membrane potential occur

A

Due to separation of the charges on either side of the membrane

28
Q

What determines the RMP

A

-diffusion of K+ from cell interior through K+ channels​

-the sodium potassium pump also contributes by moving unequal amounts of Na & K ​
(3 Na+ out / 2 K+ in)​

29
Q

What is hyperpolarisation

A

A current moving the MP further from ‘0’

30
Q

What does a depolarising current do

A

moves the MP nearer to ‘0’

31
Q

How can the MP be altered

A

By applying an electric current to the cell (a stimulus)

32
Q

What is an action potential

A

A large change in the MP of a neuron resulting in the polarisation being reversed
All or nothing event triggered by a raise in MP to -55mv (threshold)

33
Q

Process of an action potential

A

-A stimulus is applied, depolarisation occurs and the MP moves towards 0
-MP reaches -55mv causing the voltage gated Na+ channels to open which causes a rapid increase in the speed of depolarisation towards 0
-The Na+ diffuse into the membrane from high conc to low conc reversing the polarity (depolarisation)
-Once the MP reaches about +35mv the Na+ channels shut and K+ voltage gated channels open.
-As the K+ leave the cell from high conc to low conc outside the MP becomes more negative
-After a small overshoot (hyperpolarisation) the MP returns to the RMP (repolarisation)

34
Q

How do local anaesthetics work

A

They stop nerve conduction by blocking the Na+ channels

35
Q

What is the refractory period

A

The period of in inexcitability when the neuron cannot generate another AP until the first one has ended due to the inactivation of voltage gated Na+ channels

36
Q

Propagation of an impulse

A

Action potentials travel along an axon as waves of depolarisation as an AP in one section of the axon depolarises adjacent resting parts.

37
Q

How can the speed of an action potential be increased

A

-Larger axon diameters
-myelinated sheath

38
Q

What is myelination

A

A fatty layer formed by wrapping the membranes of ‘glial’ cells round the axon in turn insulating the axon to improve the overall conduction

39
Q

What is saltatory conduction

A

The AP jumps from each node of ranvier (breaks in the myelin sheath which can conduct) to another speeding up the rate at which an impulse travels along an axon.

40
Q

What effect does black widow spider venom have on synapses

A

The venom interferes with calcium ion channels in nerve cells, which causes them to release neurotransmitters uncontrollably and fire abnormally. This leads to muscle twitching, seizing, necrosis, and pain

41
Q

How does curare alter synapses

A

Curare is a competitive inhibitor of acetylcholine (ACh), the transmitter released at the presynaptic terminal. It binds directly to nicotinic receptors on the postsynaptic membrane of the neuromuscular junction, which prevents the binding of ACh and depolarization of the motor endplate, leading to muscle paralysis.

42
Q

What are the functions of the nervous system

A

Communication​

Regulating internal events​

Organising behaviour (external)​

Information storage (memory)​

Sensations, perceptions, emotions​

43
Q

Which cells are involved in the nervous system

A

Neurons (nerve cells)​

Glia (glial cells)​

44
Q

What is the function of the glia cells in the nervous system

A

More numerous than neurons​

Supportive, nutritive role​

Myelin formation​
-Schwann cells (PNS)​
-Oligodendrocytes (CNS)​

45
Q

Types of glia cells

A

Astrocytes: involved in nutrient supply to neurons in CNS​

Microglia: defence role, phagocytic​ (protection)

Ependymal cells: involved in production of cerebrospinal fluid (CSF)​ (possess cilia)

Oligodendrocytes: neuronal support & myelin formation in CNS​ (can wrap more than one neuron

Schwann cells: neuronal support & myelin formation in PNS​

46
Q

What are neurons

A

-Excitable cells​
-Generation and transmission of signals​
-Synaptic processing: memory, etc​
-Various types, structure related to function

47
Q

Where are the spinal nerves

A

Emerge along length of spinal cord​

48
Q

How many pairs of spinal nerves do we have

A

31 pairs

49
Q

What are the classification of the spinal nerves

A

8 cervical nerves​
12 thoracic nerves​
5 lumbar nerves​
5 sacral nerves​
1 coccygeal nerve​

50
Q

Structure/function of spinal nerves

A

-Each spinal nerve contains many sensory and motor axons​
-The axons supply structures in a well-defined part of the body​
-For the sensory neurons, these regions the body surface are called dermatomes​
-The motor axons supply blocks of muscle called myotomes​
-These are very useful clinically​

51
Q

What are nerve plexuses

A

These peripheral nerves supply particular regions of the body​

Axons in spinal nerves form various peripheral nerves​

52
Q

How many pairs of cranial nerves do we possess

A

12 pairs

53
Q

What is the function of cranial nerves

A

Connected to the brain, especially the brainstem​

Provide sensory and motor nerve supply to head and neck structures​

Vagus nerve (CN10) is distributed to trunk​ (relevant for whole body system)

Some (CN 3, 7, 9, 10) contain autonomic nerve fibres​

54
Q

Function of peripheral nerves (bundle of axons)

A

Carry information to and from the CNS
Afferent
Efferent

55
Q

Function of Afferent (sensory) nerves

A

Carry information to the CNS​

Afferent signals in somatic nerves are associated with sensations/perceptions​

Afferent signals from internal organs (‘viscera’) do not usually give rise to sensations​

56
Q

Function of Efferent (motor) neurons

A

Carry information away from the CNS​

Cause actions: muscle contractions, etc​

‘somatic’ efferents control voluntary muscle​

‘visceral’ efferents constitute the autonomic nervous system​

the ANS controls smooth and cardiac muscle and some glands​

57
Q

Are axons a living feature

A

Majority of axons are non living, protected by connective tissue layer

58
Q

Differentiation of nerve axons

A

A - myelinated (much thicker axons, faster response)
C - unmyelinated (very thin diameter)

Human Systems (34 decks)

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