Lecture 6: Nervous System 5 and 6

Question 1

A synapse may be either excitatory or inhibitory depending on

Answer 1

Permeability changes induced in the post synaptic neuron by the combination of neurotransmitter with receptor sites

Question 2

Excitatory synapse

Answer 2

Opening of Na channels within the postsynaptic membrane-leads to an increase in permeability to these ions
A large number of Na enters the cell, causing a net movement of positive ions into the cell, which results in a small depolarization of the postsynaptic neuron

Question 3

The postsynaptic change in an excitatory synapse is called

Answer 3

An excitatory postsynaptic potential (EPSP)

Question 4

EPSP brings the membrane potential closer to

Answer 4

• threshold

- firing an action potential

Question 5

Excitatory neurotransmitters include (4)

Answer 5

acetylcholine
norepinephrine
epinephrine
glutamate

Question 6

Inhibitory synapse

Answer 6

Neurotransmitter-receptor combo causes an increase in permeability of postsynaptic membrane to K or Cl, resulting in ion movement into the cell and a small hyperpolarization of the postsynaptic membrane

Question 7

Postsynaptic change in an inhibitory synapse

Answer 7

inhibitory postsynaptic potential

Question 8

ISPS takes the membrane potential away from

Answer 8

• threshold

- farther from firing an action potential

Question 9

Two types of inhibitory neurotransmitters

Answer 9

acetylcholine

glycine

Question 10

What is the mechanism responsible for integration of EPSPs, IPSPs, or a combo of the two in a postsynaptic neuron

Answer 10

summation

Question 11

The postsynaptic neuron can be brought to threshold in one of two ways

Answer 11

Temporal summation

Spatial summation

Question 12

Temporal summation

Answer 12

The summing of several EPSP’s occurring very close together in time because of successive firing of single presynaptic neuron

Question 13

Spatial summation

Answer 13

Summation of EPSPs originating simultaneously from several different presynaptic inputs

Question 14

Not all info received by a postsynaptic neuron is

Answer 14

passed along

Question 15

When will information be passed along?

Answer 15

Only if an excitatory presynaptic signal is reinforced by other supporting signals

Question 16

Interacting of postsynaptic potentials provide a way for one set of signals to

Answer 16

offset another set (IPSPs negating EPSPs)

Question 17

Neurotransmitter

Answer 17

chemical compound released by one neuron to affect the membrane potential of postsynaptic cell

Question 18

Neuromodulator

Answer 18

A chemical that adjusts the sensitivities of another cell to specific neurotransmitters

Question 19

Presynaptic inhibition

Answer 19

The amount of neurotransmitter released from the presynaptic terminal decreases

Question 20

Presynaptic facilitation

Answer 20

The amount of neurotransmitter released from the presynaptic terminal increases

Question 21

Axoaxonic synapse

Answer 21

• The axon of one neuron synapses with the presynaptic terminal of another
• When action potential reaches the presynaptic terminal, neuromodulators released in the axoaxonic synapse can alter the amount of neurotransmitter released from the presynaptic terminal
• Does not initiate an action potential in the presynaptic terminal

Question 22

Example of presynaptic inhibition (tetanus)

Answer 22

• Tetanus toxin prevents the release of the inhibitory neurotransmitter, gamma amino butyric acid (GABA) from inhibitory presynaptic inputs terminating on neurons that supply skeletal muscle
• Unchecked excitatory inputs to these neurons result in uncontrolled muscle spasms

Question 23

Example of presynaptic inhibition (pain prevention)

Answer 23

Enkephalins and endorphins in the CNS produces presynaptic inhibition of neurons transmitting pain sensation. They bind to opiate receptors and terminate pain signals by inhibiting the release of substance P from pre-synaptic neurons

Question 24

Presynaptic facilitation example

Answer 24

A pre-synaptic neuron releases glutamate, which binds to glutamate receptors on the postsynaptic membrane and stimulates the postsynaptic neuron to produce nitric oxide, which diffuses out of the postsynaptic neuron, crosses the synaptic cleft, diffuses into the presynaptic neuron and stimulates the release of additional glutamate from the presynaptic neuron

Question 25

Reflexes

Answer 25

rapid, automatic responses to stimuli

Question 26

How do reflexes preserve homeostasis

Answer 26

by making rapid adjustments in the function of organs or organ systems

Question 27

The response shows little variability because

Answer 27

activation of a particular reflex usually produces the same motor response

Question 28

What body functions are controlled through reflexes

Answer 28

movement of respiration and digestion

Question 29

The basic functional unit of the nervous system

Answer 29

The reflex arc

Question 30

Reflex arc

Answer 30

The smallest, simplest portion capable of receiving a stimulus and yielding a response

Question 31

Two types of reflex

Answer 31

Neural | Endocrine

Question 32

Neural reflex

Answer 32

- Sensory fibers deliver info to the CNS and motor fibers carry motor commands to the peripheral effectors - Can be spinal or cranial

Question 33

Endocrine reflex

Answer 33

A stimulus triggers the production of a hormone whose activities lead to a reduction in the magnitude of the stimulus

Question 34

Two types of neural reflex

Answer 34

Spinal and cranial

Question 35

Spinal neural reflex

Answer 35

Spinal cord serves as the integrating center

Question 36

5 steps of a reflex arc

Answer 36

1. Arrival of a stimulus and activation of a receptor 2. Activation of a sensory neuron 3. Information processing in the CNS 4. Activation of a motor neuron 5. Response by an effector

Question 37

Negative feedback

Answer 37

corrective mechanism that opposes or negates a variation from normal limits

Question 38

Reflexes can be classified according to (4)

Answer 38

1. Development 2. Processing site 3. Motor response 4. Complexity of circuit

Question 39

What is the simplest arc

Answer 39

monosynaptic arc

Question 40

Monosynaptic arc

Answer 40

A sensory neuron synapses directly on a motor neuron, which itself serves as the processing center

Question 41

Polysynaptic arc

Answer 41

One or more interneurons synapse with the sensory and motor neurons Can produce more complicated responses because the interneurons can control several groups

Question 42

5 Steps of the Stretch reflex mechanism

Answer 42

1. Stretch muscle stimulates muscle spindle 2. Propagation of action potentials along sensory neurons to the spinal cord 3. Information processing at the motor neuron 4. Activation of motor neurons 5. Contraction of muscle

Question 43

Stretch reflex maintains a _____ _____ ______ length at rest

Answer 43

normal skeletal muscle

Question 44

Is the stretch reflex mono or polysynaptic reflex?

Answer 44

Monosynaptic

Question 45

The stretch reflex provides

Answer 45

autonomic regulation of skeletal muscle length

Question 46

In the stretch reflex, what is the stimulus

Answer 46

increasing muscle length, which activates a sensory neuron which triggers the response

Question 47

In the stretch reflex, what is the response?

Answer 47

Contraction of the stretched muscle, which counteracts the stimulus

Question 48

In the stretch reflex, action potentials traveling towards and away from the spinal cord are conducted along

Answer 48

large myelinated Type A Fibers