Chapter 4 - The Nervous System

Question 1

What is the function of an Axon?

Answer 1

Transmits action potential from soma to synaptic knob.

Question 2

What is the function of the Axon Hillock?

Answer 2

Integrates excitatory and inhibitory signals from dendrites and fires action potentials if excitatory signals are strong.

Question 3

What is the function of Dendrites?

Answer 3

Receive signals and send to Soma.

Question 4

What is the function of the Myelin Sheath?

Answer 4

Acts as insulation around the axon and speeds conduction.

Question 5

What is the function of the Soma?

Answer 5

Cell body and contains the nucleus, ER, and ribosomes.

Question 6

What is the function of the Synaptic Bouton?

Answer 6

Lies at the end of the axon and releases neurotransmitters.

Question 7

What is a collection of cell bodies called in the CNS vs the PNS?

Answer 7

CNS: Nucleus
PNS: Ganglion

Question 8

Which two types of Glial cells, if not working, will make one susceptible to a CNS infection?

Answer 8

1. Astrocytes: Forms blood-brain barrier to protect from foreign pathogens.
2. Microglia: Ingests and breaks down waste products.

Disruption of either could cause infection.

Question 9

What are Ependyman Cells?

Answer 9

Line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber.

Question 10

What type of Glial Cell is being targeted in Guillain-Barre syndrome (GBS)?

Answer 10

Since GBS causes demyelination in the PNS, we can assume that Schwann cells are targeted for immune function.

Question 11

What occurs during the Absolute Refractory Period?

Answer 11

The cell is unable to fire an action potential regardless of the intensity of the stimulus.

Question 12

What occurs during the Relative Refractory Period?

Answer 12

The cell can fire an action potential only with a stimulus stronger than normal.

Question 13

What ion is primarily responsible for the fusion of neurotransmitter-containing vesicles with the nerve terminal membrane?

Answer 13

Calcium

Question 14

What are the 3 methods for stopping neurotransmitter action?

Answer 14

1. Enzyme degredation
2. Reuptake
3. Diffusion

Question 15

What entity maintains the resting membrane potential? What is the approximate voltage of the resting membrane potential?

Answer 15

Maintained by the Na+/K+ ATPase at approximately -70mV.

Question 16

What is Temporal Summation?

Answer 16

The integration of mutiple signals close to each other in time.

Question 17

What is Spatial Summation?

Answer 17

The integration of multiple signals close to each other in space.

Question 18

During the action potential which ion channel opens first and how is it regulated? What’s its effect on polarization of the cell?

Answer 18

The sodium channel opens first at threshold (around -50 mV). It is regulated by inactivation, which occurs around +35 mV. Inactivation can only be reversed by repolarizing the cell. The opening of the sodium channel causes depolarization.

Question 19

During the action potential which action potential opens second? Regulation and Effects on polariaztion?

Answer 19

The potassium channel opens second at approximatelty +35 mV. It is regulated by closing at low potentials (slightly below -70 mV). The opening of the potassium channel causes repolarization, and eventually, hyperpolarization.

Question 20

What parts of the Nervous System are in the CNS? PNS?

Answer 20

CNS: Brain and spinal cord.
PNS: Cranial, Spinal and Sensory nerves.

Question 21

What’s the difference between Afferent and Efferent neurons?

Answer 21

Afferent: (Sensory) neurons bring signals from the sensor to the CNS.
Efferent: (Motor) neurons bring signals from the CNS to an effector.

Question 22

What functions are accomplished by the Somatic Nervous System? What about Autonomic?

Answer 22

Somatic: Responsible for voluntary actions.
Autonomic: Responsible for involuntary processes.

Question 23

What are the effects of the Sympathetic NS? Parasympathetic?

Answer 23

Sympathetic: Fight-or-Flight
Parasympathetic: Rest-and-Digest

Question 24

What is the pathway of neural impulses in a Monosynaptic reflex? In a Polysynaptic reflex?

Answer 24

Monosynaptic: an afferent neuron fires directly onto an efferent neuron.
Polysynaptic: afferent neurons may fire directly onto efferent neurons, but interneurons are used as well. These interneurons fire onto other efferent (motor) neurons.