Nerves

Question 1

What makes up 90% of the cental nervous system cells?

Answer 1

Glial cells

Question 2

What is the function of astrocytes?

Answer 2

Form the blood brain barrier and maintain homeostasis for the neurones.

Question 3

What is the role of oligodendrocytes?

Answer 3

Form the central nervous system nerves myelin sheath (in the periphery, they’re Schwann cells)

Question 4

What is the function of microglia?

Answer 4

They act as immune cells for the neural environment

Question 5

What do ependymal cells produce?

Answer 5

Cerebrospinal fluid

Question 6

How is a neuronal resting membrane potential maintained?

Answer 6

K+ is pumped into the cell and Na+ is pumped out in a 1:1 ratio. However, K+ leaky channels cause potassium to leave the cell, providing an electrochemical gradient.

Question 7

When is resting membrane potential equilibrium reached?

Answer 7

When the electrical gradient is equal to and opposite to the chemical concentration potential.

Question 8

Which equation is used to estimate the resting membrane potential voltage with one ion?

Answer 8

Nernst equation (see nerve cells and connections)

Question 9

Which equation is used to predict the equilibrium membrane potential generated by multiple ions?

Answer 9

Goldman-Hodgkin-Katz equation (see nerve cells and connections)

Question 10

What is an IPSP and when does it occur?

Answer 10

Inhibitory postsynaptic potentials occur when graded potentials are hyperpolarising

Question 11

What is an EPSP and when does it occur?

Answer 11

Excitatory postsynaptic membrane potentials occur when the graded potential is depolarising.

Question 12

What are Graded potentials?

Answer 12

A potential that is depolarising gradually up to the threshold. The strength of depolarisation directly depends on the strength of the stimulus.

Question 13

How does the strength of stimulus affect the graded potential?

Answer 13

A stronger signal results in more ion channels opening and thus a larger change in the difference of potential across the membrane.

Question 14

Why are graded potentials only locally acting?

Answer 14

As the potential has not reached the threshold, the graded potential decreases in current along the axon until it is picked up or faded.

Question 15

What is graded potential summation?

Answer 15

Summation is when two weak gradient potentials combine and summate to form a single larger potential.

Question 16

How are graded potentials generated?

Answer 16

Neurotransmitters bind to the postsynaptic membrane and either induce hyper or depolarisation. The amount of neurotransmitter directly influences the strength of potential.

Question 17

How does the decrementation of graded potentials influence the position of the synapse on the postsynaptic membrane?

Answer 17

As they only act locally, the closer to the cell body, the more likely the potential is to reach threshold in the soma and become an action potential

Question 18

What is temporal summation?

Answer 18

When two signals on the same postsynaptic membrane integrate and form a single stronger graded potential?

Question 19

What is spatial summation?

Answer 19

When two signals, that occur at a similar time, from different postsynaptic membranes integrate and form a single stronger graded potential.

Question 20

What is multi integration?

Answer 20

When excitatory and inhibitory graded potentials integrate and cancel out, or at a slight interval they produce a large non-threshold change in potential.

Question 21

What is an axo-axonic synapse?

Answer 21

When the postsynaptic membrane is on the axon.

Question 22

What is an axo-dendritic synapse?

Answer 22

When the postsynaptic membrane occurs at on the dendrite.

Question 23

What is an axo-somatic synapse?

Answer 23

When the postsynaptic membrane is on the cell soma.

Question 24

Why does myelination increase conductance velocity?

Answer 24

Increases membrane resistance, thus reducing membrane capacitance and the amount of current lost. Action potentials spread passively from node to node

Question 25

What is an ionotropic potential?

Answer 25

A fast EPSP, so called because its receptor directly opens ion channels in the synapse.

Question 26

What is a metabotropic potential?

Answer 26

A slow EPSP, so called because its receptor is only linked to ion channels as a result of g-protein second messengers.

Question 27

What is self inhibition?

Answer 27

When a neuron activates an interneurone that in inhibits the neurone it was stimulated by. It inhibits itself.

Question 28

What is a monosynaptic response?

Answer 28

When a sensory neurone directly activates a single motor neurone.

Question 29

What is a polysynaptic response?

Answer 29

When a series of interneurones lay between the sensory neurone and its motor neurone. These interneurones integrate converging inputs to either activate or inhibit the motor neurone.

Question 30

What is a muscle spindle?

Answer 30

A stretch receptor activated when a muscle is stretched

Question 31

What is the muscle spindle reflex?

Answer 31

When the receptor is activated, it send s signal via the CNA to the alpha motor neurone to contract the muscle. This means a muscle can change its contractile strength, but remain at a constant length. This is in response to changing levels of force.

Question 32

Where do extrafusal fibres lie?

Answer 32

Parallel to the spindle and form the majority of the muscle.

Question 33

Where do intrafusal fibres lie?

Answer 33

In series with spindles, form a smaller amount of the muscle with ypsilon innervation.

Question 34

Name a specific example of muscle spindle reflex.

Answer 34

Patellar tendon reflex.

Question 35

What is a golgi tension receptor organ?

Answer 35

A receptor that activates when a muscle is under so much tension it risks damage.

Question 36

What is the golgi tendon reflex?

Answer 36

When the muscle is under so much tension it risks damage, the receptor inhibits motorneurones of the muscle via a CNS pathway

Question 37

Name a specific example of golgi tendon reflex.

Answer 37

Clasp-knife reflex (as in the muscle quickly reduces resistance like a clasp-knife)

Question 38

What is the flexion & crossed extensor reflex?

Answer 38

When stepping on a painful stimulus, the nociceptors cause the limb in question to recoil (flexion) and extension of the opposite leg, to stop falling over.

Question 39

How does the flexion cross extensor initiate a response?

Answer 39

The nociceptor pathway inhibits the ipsilateral extensors and activates the ipsilateral flexors; the contralateral limb has its flexors inhibited and extensors activated. A fifth synapse sends the signal to the CNS

Question 40

Which cortical region is responsible for movement?

Answer 40

The primary motor cortex in the precentral gyrus.

Question 41

Name the main regions of the basal ganglia?

Answer 41

1) Putamen 2) Caudate 3) Globus Pallidus 4) Substantia nigra

Question 42

By which pathway do the basal ganglia regions communicate with each other?

Answer 42

Nigrostriatal | Striatonigral

Question 43

What is destroyed in parkinsons?

Answer 43

80% basal ganglia region pathways.

Question 44

What are overactive dopamine linked to and in which pathway is this?

Answer 44

Overactive dopamine is linked to schizophrenia and occurs in the nigrostriatal pathway.

Question 45

Which dopamine precursor is used in the treatment of parkinsonian illnesses?

Answer 45

L-Dopa

Question 46

What information does the cerebellum receive and what function does it perform?

Answer 46

It receives proprioceptive and vestibular information and is involved in the fine tuning of movements

Question 47

What functions is the basal ganglia involved with?

Answer 47

It is involved with producing volition for movement and initiating a movement, amongst other things.

Question 48

Where are locomtory rhytms generated?

Answer 48

Spinal cord.