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Physiology > Lab 3 > Flashcards

Lab 3 Flashcards

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1
Q

What is a synapse?

A

A functional connection of the neuron with:
- another neuron
- sensory receptor
- effector cells (muscle or glandular cell)

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2
Q

What role does a synapse have?

A

its role is to transmit signals

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3
Q

What substance transfers impulses between cells in a synapse?

A

A substance that acts as a neurotransmitter (neurohormone) or by electrical impulse

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4
Q

What are the different types of synapses?

A

Group 1:
Neuro- (neuronal/muscular/glandular)

Group 2:
Chemical
Electrical

Group 3:
axono- (axonal (inhibitory) / Somatic / dendritic)
dendro- (dendric/somatic)
Somato-somatic

Group 4:
stimulatory / excitatory
inhibitory

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5
Q

What is Divergence (of traits)?

A

When one presynaptic neuron creates synaptic connection with many postsynaptic neurons

Analysis of transmitted information

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6
Q

What is convergence (of traits) ?

A

When many presynaptic neurons form synaptic connections with one neuron

Integration of the information transmitted

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7
Q

Draw excitatory synapse and explain

A

Positive ions enter the channel which leads to decrease in electronegativity of the interior

(due to Na + ions in the interior, it becomes positive)

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8
Q

Draw an inhibitory synapse and explain

A

Negative ions enter the channel, as a result we can see an increase in electronegativity of the interior

(it becomes negative due to the Cl- ions)

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9
Q

what can happen with inhibition in some nerve cells? what can it involve?

A

Inhibition can sometimes involve opening of k+ channels, resulting in positive k+ ion efflux and hyperpolarization

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10
Q

What is EPSP? (Excitatory postsynaptic potential)

A

Decrease in the negative intracellular potential after Na+ migrates across the postsynaptic membrane.

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11
Q

What is IPSP? (Postsynaptic inhibitory potential)

A

Increase in negative electric potential inside the cell and the polarization of the cell membrane after K+ ions escape and Cl- ions flow into the cell.

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12
Q

What do EPSP and IPSP serve as?

A

They serve as modifiers of the action potential generation frequency

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13
Q

What chemical synapse is this?

A

Insufficient excitation, refers to a situation where the level of stimulation (or excitatory input) is too low to trigger a response

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14
Q

What chemical synapse is this?

A

Temporal summation of excitation, Stimmuli are applied one after another raising membrane potential until it becomes the threshold stimulus

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15
Q

What chemical synapse is this?

A

Spatial summation of excitation, Subliminal stimuli act on the membrane simultaneously

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16
Q

What chemical synapse is this?

A

Excitation + inhibition refers to the combined effect of excitatory and inhibitory inputs on a cell, usually a neuron. Cells in the nervous system often receive a mix of excitatory signals (which increase the likelihood of firing) and inhibitory signals (which decrease that likelihood). The net effect determines whether the cell will respond or not.

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17
Q

What are the two types of inhibition in the CNS (Central Nervous System)?

A
  1. External inhibition (inhibitory synapses)
  2. Internal inhibition (reticular formation)
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18
Q

What happens during the Synaptic (external) inhibition?

A

There is simultaneous stimulation of the excitatory and inhibitory nerves in the center by the stimulus.

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19
Q

What does the Synaptic (external) inhibition do?

A

It prevents the excessive spread of the excitation,

And ensures the extinction of the reflex and enables coordinated muscle work

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20
Q

What does the Presynaptic (external) inhibition do?

A

It impaires the action potential running in the axon of the excitatory neuron

Leads to reduction in the amount of mediator released from the excitatory neuron terminal

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21
Q

What type of synapses are Presynaptic (external) inhibition and what mediates the synapses?

Study These Flashcards
A

Axono-axonal synapses

GABA is the mediator at these synapses

22
Q

What mediator is secreted at the end of the inhibitory interneuron in postsynaptic (external) inhibition?

23
Q

What does glycine do in the postsynaptic (external) inhibition?

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A

It activates Cl- channels after binding to the receptor. This leads to hyperpolarization of the postsynaptic membrane.

24
Q

What does the Postsynaptic (external) inhibition do and what type of synapses are these?

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A

It creates inhibitory postsynaptic potential (IPSP) on the postsynaptic membrane

Axono-somatic and axono-dendritic synapses

25
Feedback inhibition vs Reciprocal inhibition
Feedback inhibition - Axons of the motoneurons from collaterals (branches) that stimulate the inhibitory neurons. --> Inhibitory interneurons inhibit the neuron that stimulated them and other motorneurons Reciprocal inhibition - Axons of the sensoty fiber gives a branch to inhibitory interneurons and stimulates them. --> Due to external inhibition, antagonistic muscles (extensors) are relaxed when the only other group of muscles is stimulated (flexors)
26
What does the reticular system do? Where can it be found? And what are the parts of the brain stem?
It sends signals to various parts of the CNS It can be mainly found in the brain stem and the diencephalon (thalamus) Its parts are: - Medullary part - Pontine part - Midbrain part
27
Is the reticular system specific? And what does the reticular system of the thalamus do?
It's a non-specific system It inhibits impulses from the reticular system of the brainstem, gates information flowing to the cerebral cortex
28
What do the pathways leading into and out of the reticular system form?
They form: - Descending inhibitory reticular system (medullary) - Descending stimulating reticular system (pontine) - Ascending excitatory reticular system (ARAS)
29
Ascending activation system, what it does and what it affects.
- It plays a role in choosing the body's response to a stimulus. - It stimulates the subcortical centers - Affects the state of sleep and wakefulness --> Positive feedback excitation on the reticular system, cerebral cortex and peripheral system leads to the fatigue of these circuits --> The activity of the reticular system decreases, which leads to relaxation and sleep --> Destruction of the reticular system causes irreversible loss of consciousness
30
Descending inhibitory system, what does it cause and what is an example of this?
It causes generalized inhibition of the motorneurons in the spinal cord. An example of the stimulation of this system is animal hypnosis - akinesia
31
What is Strychnine?
It's an organic chemical compound, an alkaloid found in the seeds of the Strychnos nux-vomica, with strong toxic properties.
32
What does Strychnine get used for?
At low doses, it acts as a stimulant; it also sharpens the senses In rare instances it can be used as a medicine, because therapeutic doses are close to toxic doses (1-2 mg/kg) It was also formerly an ingredient of rodenticides
33
What is akinesia?
Akinesia is a specific, stereotypical, unconditional, independent of will reaction to a specific stimulus In short, animal hypnosis
34
How does akinesia work?
A stimulus activates a series of interneurons of the descending reticular system. Postsynaptic inhibitory potentials arise on the spinal motorneurons, this causes a deep general inhibition of skeletal muscles.
35
What happens in akinesia in the cerebral cortex?
It inhibits the limbic system responsible for emotions like fear Stimulates the control reflex center for mobility
36
What does inhibition of the motor cortex centers lead to?
To inhibitory signals from the cerebral cortex increasing the activity of the descending inhibitory reticular system and decrease the activity of descending activating reticular system
37
In what animals can we easily induce the akinesia reflex?
In animals with poorly developed cortex - Frog - Guinea pig - Rabbit - Chicken - Sometimes cat - Small ruminants
38
Adequate stimulus vs Nonadequate stimulus
Adequate stimulus (specific) - Receptor responds at the lowest excitability threshold while causing a specific sensory impression Nonadequate stimulus (not specific) - Not characteristic to a given receptor, but with sufficiently high intensity it can cause a specific sensory impression
39
What is a sensory receptor?
A structure that converts the energy of a stimulus into the energy of the nerve impulse They connect with the sensory fibers in the so-called sensory units
40
What is a sensory receptor characterized by?
- High excitability - Specificity - Adaptation
41
Morphologically a receptor may be?
1. Free, myelin-free peripheral terminal of a sensory neuron. E.g. Thermoreceptors 2. Specialized neuron, E.g. Retinal cones or rods, olfactory cells 3. A distinct receptor cell (sensory cell), E.g. the hair cell of the Corti organ
42
How do skin receptors and proprioreceptors respond/adapt to the decrease or disappearance of the generating potential?
Skin receptors - adapt well Proprioreceptors - do not adapt
43
What are Meissner bodies and Merckel discs? And where can we mainly find them?
Meissner bodies - The ends of thick myelin fibers surrounded by a capsule containing nerve fibers - found in large numbers in fingertips and on the lips Merckel discs - Consist of small disks of connective tissue mesh and connected with a thick myelinated fiber - Found mainly in fingertips
44
How do Meissner bodies and Merckel discs adapt?
Meissner bodies - adapt quickly (1-few seconds) Merckel discs - adapt slowly
45
What are Hair follicle basket receptors, sensory bodies and Pacini bodies? What do they do and how do they adapt?
Hair follicle basket receptors - The ends of thin myelin fibers around hair follicles - Detect hair movement as well as stimuli of low-intensity Sensory bodies - Bundles of exposed nerve fibers - Experience long-lasting and strong pressure - Adapt slowly Pacini bodies - Consist of a myelin-free nerve fiber ending surrounded by numerous connective tissue plaques - Signal the change of pressure - Adapt instantly (fractions of a second)
46
How much 1cm2 do the receptors cover? And what temperatures do thermoreceptors respond to?
Cold - 13-15/1cm2 - react to temperatures 10-40C Heat - 1-2/1cm2 - react to temperatures of 30-45C in the range of 20-40C, the receptors adapt that to so the perception of hot and cold disappears Pain receptors are also sensitive to temperature changes (damaging temps >45C)
47
What types of excitability can we find in skin sensory receptors? and what coverage do they have on the skin?
There are two types - Low excitability - High excitability They cover 50-200/1cm2 of skin
48
Where can we find skin sensory receptors and what do they inform us about?
We can find these in almost all tissues They inform us about damaging or potentially damaging mechanical, chemical or thermal stimuli
49
Activation of what is the source of initial pain and impression of chronic pain?
Aδ fibers is the source of initial pain (fast, precisely localized), while activation of C fibers gives the impression of chronic (poorly localized) pain.
50
What are the different types of sensory fibers in the skin?
- Aδ fibers (fast, myelin) pain (20%) pronounced, sharp, localized, cold, touch / pressure - C fibers (thin, myelin free) pain (80%) dull, diffuse, warm and cold - Aβ (rapid myelin) fibers touch / pressure
51
What are a few features of the chemical synapse?
- One-way conduction of information from pre- to postsynaptic cell, by chemicals (mediators, transmitters, neurotransmitters) - Sensitivity to hypoxia (a decrease in oxygen tension in the arteries) - Synaptic delay - the time it takes for an impulse to travel from pre- to postsynaptic cell (ca. 0,5 ms)

Physiology (3 decks)

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