Sensory and Motor Mechanisms

Question 1

What are sensations and what are they triggered by?

Answer 1

They are triggered by sensory stimuli and travel to the brain as action potentials (APs) via sensory pathways.

Question 2

What is perception?

Answer 2

Perception is the ability to discriminate various aspects of stimulus and is the meaningful interpretation of sensory data.

Question 3

What is the difference between sensation and perception?

Answer 3

Sensation is the data and perception is the interpretation of that data.

Question 4

What is the MAIN function of the nervous system?

Answer 4

Rapid communication and information processing.

Question 5

What is sensory input?

Answer 5

The external and internal information received by the CNS (central nervous system) from sensory receptors.

Question 6

What is integration in the CNS?

Answer 6

In the CNS, integration is the interpretation of the input and it is the association of the input with different body responses.

Question 7

What is the motor output?

Answer 7

Motor output are the signals from the integration centres in the CNS to effector cells.

Question 8

What are the two types of neurons?

Answer 8

Afferent and efferent neurons

Question 9

What is the function of afferent neurons?

Answer 9

Afferent neruons send signals from the peripheral nervous system (PNS) to the central nervous system (CNS) (basically sensory system to integration)

Question 10

What is the function of efferent neurons?

Answer 10

Efferent neurons send signals from the CNS to the PNS (motor output, effector cells).

Question 11

Does shape affect receptor type?

Answer 11

Yes

Question 12

One problem with sensory systems is the conversion of stimulus energy into a neuronal system. What are the three ways the body can answer this problem?

Answer 12

Transduction, amplification or transmission.

Question 13

What are the two ways transduction in the sensory system can occur?

Answer 13

1) Stimulus hits sensory receptors which leads to a change in the receptor membrane. 2) Permeability of the receptor membrane leads to receptor potential

Question 14

What is receptor potential?

Answer 14

A graded change in membrane potenial.

Question 15

What is amplification?

Answer 15

The increase of exposure to something. For example: the activation of a cascade (series of reactions, like a domino effect) or sensory adaptation.

Question 16

What is sensory adaptiation?

Answer 16

Continued exposure/stimulation leads to decreased responsiveness. Don’t want to overload our receptors if the signal is not dangerous since the body has limited resources so sensory adaptation stops the body from paying attention to unnecessary stimulus.

Question 17

What are the two cases in which transmission occurs when stimulus comes into contact with a sensory receptor?

Answer 17

1) If the receptor is a sensory neuron, then it will conduct APs to the CNS (it is a sensation, sensory input). 2) If the receptor is not a sensory neuron, then it will generate APs to send the signal to the CNS

Question 18

Another problem with sensory systems is the encoding of information regarding stimulus. What are the four ways the body can answer this problem?

Answer 18

1) Type of stimulus; what type of activated receptor is it? 2) Intensity: what is the number of activated receptors and the frequency of APs? 3) Location: where are the activated receptors? What about the timing? 4) Duration: what is the pattern of APs being sent to the CNS?

Question 19

Sensory receptor(s) is activated and gentle pressure is applied. What is the frequency of APs?

Answer 19

There will be a low frequency of APs per receptor.

Question 20

Sensory receptor(s) is activated and more pressure is applied. What is the frequency of APs?

Answer 20

There will be a high frequency of APs per receptor.

Question 21

What does stimulus strength depend on?

Answer 21

AP frequency. An increase in stimulus will increase AP frequency.

Question 22

What are the five types of receptor types?

Answer 22

Chemoreceptors, mechanoreceptors, thermoreceptors, nociceptors, electromagnetic recetors.

Question 23

What are chemoreceptors responsible for?

Answer 23

Chemical stimulus; taste, smell.

Question 24

What are mechanoreceptors responsible for?

Answer 24

Vibration and pressure; touch, sound.

Question 25

What are thermoreceptors responsible for?

Answer 25

Temperature; heat, burns

Question 26

What are nociceptors responsible for?

Answer 26

Tissue damage; NOT pain = pain is perception.

Question 27

What are electromagnetic receptors responsible for?

Answer 27

Visual stimulus; sight, light

Question 28

Another problem with sensory systems is the interpretation of information (perception). What are the four ways the body can answer this problem?

Answer 28

1) Processing and integrating sensory information starts and pathways and heads to the brain. 2) There is a hierarchy and parallel way to processing the information. 3) Different parts of the brain process different information. 4) The incorporation of information from different modalities in higher association centres.

Question 29

What are neuropeptides and their function?

Answer 29

They are short chains of amino acids that include substance P and endorphins that affect our perception of pain.

Question 30

What is the function of opiates (a type of neurotransmitter)

Answer 30

Bind to same receptor as endorphins, painkillers.

Question 31

Gases (NO/CO) are neurotransmitters, what is their function?

Answer 31

They are regulators in the PNS. They are synthesized on demand and are not stored in cytoplasmic vesicles.

Question 32

Where are synapses located?

Answer 32

Mostly on dendrites.

Question 33

Describe the process of transferring neurotransmitters across neurons.

Answer 33

The presynaptic neuron synthesizes and packages neurotransmitters in synaptic vesicles in the synaptic terminal. AP causes the activation of Ca 2+ channels required to trigger vesicle fusion. They then diffuse across the synaptic cleft and are received by the post synaptic cell.

Question 34

How does direct synaptic transmission occur?

Answer 34

It involves binding neurotransmitters to ligand-gated ion channels in the postsynaptic cell.

Question 35

How are post synaptic potentials (PSPs) generated?

Answer 35

The binding of neurotransmitters causes ion channels to open which generates these PSPs.

Question 36

What are the two categories of PSPs?

Answer 36

Excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs)

Question 37

What is the function of excitatory postsynaptic potentials (EPSPs)?

Answer 37

They cause depolarizations that bring the membrane potential to the threshold.

Question 38

What is the function of inhibitory postsynaptic potentials (IPSPs)?

Answer 38

They cause hyperpolarizations that bring the membrane potential further from the threshold.

Question 39

How are ligand-gated receptors triggered?

Answer 39

A single neurotransmitter can bind to more than a dozen different receptors to trigger this activation; neurotransmitters can excite postsynaptic cells expressing one receptor and inhibit postsynaptic cells from expressing different receptors.

Question 40

What is the function of ionotropic receptors?

Answer 40

They gate ion flow.

Question 41

What is the function of metabotropic receptors?

Answer 41

They are G-protein coupled receptors. Binding to a metabotropic receptor activates a signal transduction pathway in postsynaptic cells involving second messengers.

Question 42

Second messengers vs ligand-gated ion channels

Answer 42

Second messengers have a slower onset but they last longer compared to the ligand-gated ion channels.

Question 43

How do neurotransmitters return to the presynaptic neuron?

Answer 43

After diffusing across the presynaptic neuron and landing on the receptor, enzymatic hydrolysis occurs that breaks down the neurotransmitters to be recaptured by transport channels into the presynaptic neuron.

Question 44

What are the two types of synapses that neurons communicate by?

Answer 44

Chemical &/or electrical synapses. They can be separate and mixed together.

Question 45

How do electrical synapses relay information between neurons?

Answer 45

An electrical current flows from one neuron to another via gap junctions.

Question 46

How do chemical synapses relay information between neurons?

Answer 46

Neurotransmitters carry information between neurons.

Question 47

What is temporal summation, and what is its main function?

Answer 47

Since a single EPSP is too small to trigger an AP in a postsynaptic cell, temporal summation is the effect that occurs when 2 EPSPs are produced in rapid succession to reach the threshold and generate an AP. EPSPs are driven by excitatory receptors with equilibrium potentials around 0mV.

Question 48

What type of receptors are IPSPs driven by and what is their equilibrium potential range?

Answer 48

They are driven by inhibitory receptors with equilibrium potentials ranging from -60 to -90 mV.

Question 49

What is spatial summation?

Answer 49

Spatial summation occurs when EPSPs are produced nearly simultaneously by different synapses on the same postsynapse and add together.

Question 50

What happens when EPSPs in spatial and temporal summation are added together?

Answer 50

They can trigger an AP.

Question 51

What happens when EPSPs and IPSPs are added together?

Answer 51

They can counter the effect that EPSPs produce.

Question 52

What determines whether the axon hillock will reach the threshold to generate an AP?

Answer 52

This summed effect of EPSPs and IPSPs.