Physiology, Neurophysiology 2

Front 1

What is the function of acetylcholinesterase?

Back 1

The enzyme acetylcholinesterase converts acetylcholine into the inactive metabolites choline and acetate. This enzyme is abundant in the synaptic cleft, and its role in rapidly clearing free acetylcholine from the synapse is essential for proper muscle function.

Front 2

EPSPs are graded, what does that mean?

Back 2

They have an additive effect. When multiple EPSPs occur on a single patch of postsynaptic membrane, their combined effect is the sum of the individual EPSPs. Larger EPSPs result in greater membrane depolarization and thus increase the likelihood that the postsynaptic cell reaches the threshold for firing an action potential.

Front 3

Describe electrical synapse.

Back 3

An electrical synapse is a mechanical and electrically conductive link between two abutting neurons that is formed at a narrow gap between the pre- and postsynaptic neurons known as a gap junction.Compared to chemical synapses, electrical synapses conduct nerve impulses faster, but unlike chemical synapses they do not have gain (the signal in the postsynaptic neuron is the same or smaller than that of the originating neuron).

Front 4

What is a connexon?

Back 4

In biology, a connexon is an assembly of six proteins called connexins that can be a part of a gap junction channel between the cytoplasm of two adjacent cells. They can be opened or closed, which is regulated by intracellular signalling (phosphorylation).

Front 5

What is a neurotransmitter?

Back 5

Neurotransmitters are endogenous chemicals which transmit signals from a neuron to a target cell across a synapse.

Front 6

What is an inhibitory postsynaptic potential (IPSP)?

Back 6

IPSP is a graded hyperpolarisation that moves the membrane potential further from the threshold for firing an action potential.

Front 7

What is the ionotropic transmembrane receptor for glutamate that mediates fast synaptic transmission in the central nervous system (CNS).

Back 7

The ionotropic glutamate receptor (AMPA-type).

Front 8

Name receptors for synaptic excitation and inhibition.

Back 8

Synaptic excitation: the ionotropic Glutamate receptor.
Synaptic inhibition: GABAa receptor.

Front 9

Name which receptor is:
- the major central inhibitory receptor type;
- is a ligand-gated ion channel composed of 5 subunits;
- is permeable to Cl- and HCO3- ions.

Back 9

GABAa receptor.

Front 10

Which receptor is:
-one of the most abundant central receptors;
- is a ligand-gated ion channel composed of 4 subunits;
- is permeable to Na, K, and sometimes Ca ions.

Back 10

Ionotropic glutamate receptor (AMPA-type).

Front 11

IPSP and EPSP are unable to do what in comparison to AP?

Back 11

To travel along the axons.

Front 12

What do sensory receptors respond to?

Back 12

Light, heat, mechanical, chemical, etc.

Front 13

What type of neurones are sensory receptors?

Back 13

Sensory receptors are either specialised endings of afferent neurons or separate cells that signal to the afferent neurone.

Front 14

Sensory receptors are transducers. What does that mean?

Back 14

Sensory receptors convert one form of energy (e.g. heat, pressure, chemical) into another form, e.g. electrical energy or depolarisation.

Front 15

The depolarisation occurring at the sensory terminal is called ... .

Back 15

Receptor potential (RP)

Front 16

Is the depolarisation occurring at the sensory terminal propagating or non-propagating?

Back 16

Non-propagated, it is confined to terminal, it is graded.

Front 17

What relationship is there between the number of action potentials generated by a pressure-sensitive sensory afferent neurone and stimulus intensity?

Back 17

Directly proportional.

Front 18

What is the mechanisms that prevents sensory information overload?

Back 18

Adaptation to stimuli of receptors.

Front 19

There are slow adaptations to the stimuli and fast, and there are stimuli that receptors are not able to adapt to. What are they?

Back 19

Pain receptors are nonadapting receptors.

Front 20

What function do sensory receptors in internal organs have?

Back 20

They are essential for homeostasis and also alert the body in case of some anomaly.

Front 21

How is intensity of the stimulus encoded?

Back 21

By the frequency of action potentials.

Front 22

What is the name of information sent to the CNS from the sensory receptors?

Back 22

Afferent information.

Front 23

What is the reason for referred pain?

Back 23

In the CNS it is usual that several afferent neurones contact the same postsynaptic cell. This is convergence.

Front 24

Label the axis and fill in blanks about which channels close or open in a specific moment.

Back 24

Front 25

Label.

Back 25

Front 26

What is threshold stimulus?

Back 26

The minimum stimulus needed to achieve an action potential is called the threshold stimulus. The threshold stimulus causes the membrane potential to become less negative (because a stimulus, no matter how small, causes a few sodium channels to open and allows some positively-charged sodium ions to diffuse in).

Front 27

What is a propagation of the AP?

Back 27

It is repeating of AP down the axon.

Front 28

Name three types of neurone.

Back 28

Multipolar, unipolar, bipolar.

Front 29

What is multipolar neurone?

Back 29

Multipolar neurons are so-named because they have many (multi-) processes that extend from the cell body: lots of dendrites plus a single axon. Functionally, these neurons are either motor (conducting impulses that will cause activity such as the contraction of muscles) or association (conducting impulses and permitting 'communication' between neurons within the central nervous system).

Front 30

What is unipolar neurone?

Back 30

Unipolar neurons have but one process from the cell body. However, that single, very short, process splits into longer processes (a dendrite plus an axon). Unipolar neurons are sensory neurons - conducting impulses into the central nervous system.

Front 31

What is bipolar neurone?

Back 31

Bipolar neurons have two processes - one axon & one dendrite. These neurons are also sensory. For example, biopolar neurons can be found in the retina of the eye.

Front 32

Name subdivisions of ANS - autonomic nervous system.

Back 32

Sympathetic, parasympathetic, enteric.

Front 33

What is the difference between preganglionic fibre lengths of sympathetic and parasympathetic NS?

Back 33

In Sympathetic NS preganglionic fibres are shorter than in parasympathetic NS.

Front 34

What are the major transmitters in the autonomic synapses?

Back 34

Noradrenaline (NA) and acetylcholine (ACh).

Front 35

In which part of the ANS neurotransmitter noradrenaline is used?

Back 35

In the synapses of sympathetic NS between the postganglionic fibre and effector organ.

Front 36

Describe alpha receptors.

Back 36

Alpha receptors are located postsynaptically at sympathetic neuroeffector junctions of many organs. In general, alpha receptors mediate excitation or increased activity of the effector cells. Vascular smooth muscle is an important site of alpha receptors. SNS activity maintains vascular tone, and thus blood pressure, by maintaining a tone of neurotransmitter on vascular alpha receptors.

Front 37

Describe beta receptors.

Back 37

Beta receptors are also located postsynaptically at sympathetic neuroeffector junctions of many organs. In general, beta receptors mediate relaxation or decreased activity of the effector cells. Thus, blood vessels dilate and uterine smooth muscle relaxes in response to activation of beta receptors. Heart muscle is an important exception to this rule. Activation of beta adrenoceptors in heart increases the automaticity and contractility of all parts of the heart.

Front 38

Describe adrenergic receptors (α and β).

Back 38

The adrenergic receptors (or adrenoceptors) are a class of metabotropic G protein-coupled receptors that are targets of the catecholamines, especially noradrenaline (norepinephrine) and adrenaline (epinephrine). Many cells possess these receptors, and the binding of an agonist will generally cause a sympathetic (or sympathomimetic) response (e.g. the fight-or-flight response). For instance, the heart rate will increase and the pupils will dilate, energy will be mobilized, and blood flow diverted from other non-essential organs to skeletal muscle.

Front 39

Shortly, what selected action
of agonist do alpha and beta receptors have?

Back 39

α - Smooth muscle contraction and neurotransmitter inhibition & Cardiac muscle relaxation;
β - Smooth muscle relaxation, Heart muscle contraction, Enhance lipolysis.

Front 40

Name some of the effects of SNS.

Back 40

- Increase in heart rate, increase force of contraction;
- Pupil dilatation;
- Glycogenolysis (release of glucose from the storage form) and gluconeogenesis (new glucose made) - Increase in blood glucose.

Front 41

When does the parasympathetic NS dominate?

Back 41

During sleep and rest.

Front 42

Name some of the effects of parasympathetic nervous system.

Back 42

- Eye pupil constriction (accommodation for near objects);
- Motility of stomach and intestine increases;
- Trachea and bronchi constriction;
- Decrease in heart rate and force of contraction.

Front 43

How is sensory transduction mediated?

Back 43

Through opening or closing specific ion channels.

Front 44

What are nociceptors activated by?

Back 44

By extremes of pressure, temperature, or noxious chemicals.

Front 45

Name five types of sensory receptors.

Back 45

Mechanoreceptors
Thermoreceptors
Nociceptors
Photoreceptors
Chemoreceptors

Front 46

In sensory transduction what is called receptor potential?

Back 46

It is the change in membrane potential, which increases or decreases the likelihood that action potentials will occur.

Front 47

What is the number of neurons in the efferent part in somatic NS and autonomic NS?

Back 47

Somatic - 1, autonomic - 2.

Front 48

Name target tissues for somatic and autonomic NS?

Back 48

Somatic - only skeletal muscle;
Autonomic - smooth and cardiac muscle, some endocrine and exocrine glands, some adipose tissue.

Front 49

Fill in the table.

Back 49

Front 50

Label.

Back 50

Front 51

What is the number of neurons in the efferent part in somatic NS and autonomic NS?

Back 51

Somatic - 1, autonomic - 2.

Front 52

Name target tissues for somatic and autonomic NS?

Back 52

Somatic - only skeletal muscle;
Autonomic - smooth and cardiac muscle, some endocrine and exocrine glands, some adipose tissue.

Front 53

Label.

Back 53

Front 54

What is the purpose of Enteric NS?

Back 54

Regulates work of the GI tract.

Front 55

What do motor neurones of the ENS control?

Back 55

- Contraction of the GI tract smooth muscle which push food through the GI tract;
- Secretion of the GI tract organs;
- Activity of the GI tract endocrine cells, which secrete hormones.