Organization of the Human Nervous System

Question 1

What are the 3 types of Nerve Cells in the Nervous System?

Answer 1

• Sensory Neurons (or Afferent Neurons)
• Motor Neurons (or Efferent Neurons)
• Interneurons

Question 2

What is the main function of a Sensory Neuron?

Answer 2

AKA Afferent Neurons

Sensory Neurons transmit sensory information from receptors to the spinal cords and brain.

Mnemonic: Afferent neurons Ascend in the cord towards the brain.

Question 3

What is the main function of a Motor Neuron?

Answer 3

AKA Efferent Neuron

Motor Neurons transmit motor information from the brain and spinal cord to the muscles and glands.

Mnemonic: Efferent neurons Exit the cord on their way to the rest of the body.

Question 4

What is the main function of Interneurons?

Answer 4

Interneurons are found between sensory and motor neurons predominantly located in the brain and spinal cord.

Interneurons are often linked to reflexive behavior and are the most numerous of the three types of neurons; involved in the reflex arc.

Question 5

What is a reflex arc?

Answer 5

Reflex arc(s) is a neural pathway (or circuits) that controls reflex actions

Question 6

What are the two primary components of the Nervous System?

Answer 6

The Central Nervous System (CNS) and The Peripheral Nervous System (PNS)

Question 7

What parts of the Nervous System are in the Central Nervous System?

Answer 7

The Central Nervous System (CNS) is composed of the brain and spinal cord.

Question 8

What parts of the Nervous System are in the Peripheral Nervous System?

Answer 8

The Peripheral Nervous System (PNS) is composed of nerve tissue and fibers outside the brain and spinal cord which includes all 31 pairs of spinal nerves and the 12 pairs of cranial nerves.

The PNS connects the CNS to the rest of the body via CN I & II and can itself be subdivided into Somatic and Autonomic Nervous Systems.

Question 9

Are the Olfactory Nerve & Optic Nerve (Cranial Nerves I and II) part of the CNS or PNS?

Answer 9

The Olfactory and Optics nerves are structurally outgrowths of the Central Nervous System but are still considered components of the Peripheral Nervous System.

Question 10

What is the main function of the Somatic Nervous System?

Answer 10

The Somatic Nervous System is composed of sensory and motor neurons distributed throughout the skin, joints and muscles.

Here, the sensory neurons transmit information through afferent fibers and motor neurons, in contrast, travel along efferent fibers.

Question 11

What is the main function of the Autonomic Nervous System (ANS)?

Answer 11

The Autonomic Nervous System generally regulates heartbeat, respiration, digestion and glandular secretions. Additionally, the ANS helps regulate body temperature when it’s too hot (sweating) or too cold (piloerection).

Basically, the ANS manages the involuntary muscles (or automatic functions) associated with many internal organs and glands. The main takeaway is that the ANS functions are automatic, or independent of conscious control.

Notice: Autonomic is similar in spelling to Automatic

Question 12

What are the two subdivisions of the Autonomic Nervous System (ANS)?

Answer 12

The two subdivisions are The Sympathetic Nervous System and the Parasympathetic Nervous System.

Question 13

What type of relationship best describes the dynamic between the Sympathetic Nervous System and Parasympathetic Nervous System?

Answer 13

The relationship between these two branches is antagonistic, meaning they often act in opposition to one another.

i.e.: The Sympathetic Nervous System acts to accelerate heart rate and inhibit digestion, while the Parasympathetic Nervous System decelerates heart rate and increases digestion.

Question 14

What is the main role of the Parasympathetic Nervous System?

Answer 14

The main role of the Parasympathetic Nervous System is to conserve energy.

The Parasympathetic Nervous System is associated with resting and sleeping states.

Mnemonic: Parasympathetic is to “rest-and-digest”

Question 15

What are the functions of the Parasympathetic Nervous System?

Answer 15

1. ) Constrict Pupils (via CN III & VII)
2. ) Stimulate Flow of Saliva (via CN VII & IX)
3. ) Constrict Bronchi (via CN X [vagus])
4. ) Slows Heartbeat (via CN X [vagus])
5. ) Stimulates Peristalsis & Exocine Secretion [for digestion] (via CN X [vagus])
6. ) Stimulates Bile Release (via CN X [vagus])
7. ) Contracts Bladder (via CN X [vagus] & Pelvic Splanchnic Nerves)

Question 16

What is the main role of the Sympathetic Nervous System?

Answer 16

The main role of the Sympathetic Nervous System is to expend energy. The Sympathetic Nervous System is typically activated by stress which can include anything from mild stressors to emergencies that involve life-and-death situations.

The Sympathetic Nervous System is associated with rage and fear reactions.

Mnemonic: Sympathetic is to “fight-or-flight”

Question 17

What neurotransmitter is responsible for Parasympathetic responses in the body?

Answer 17

Acetylcholine

Question 18

What are the functions of the Sympathetic Nervous System?

Answer 18

1. ) Increases heart rate
2. ) Redistributes blood to muscles of locomotion
3. ) Increases blood glucose concentration
4. ) Relaxes the bronchi
5. ) Decreases digestion and peristalsis
6. ) Dilates the eyes to maximize light intake
7. ) Releases epinephrine into the bloodstream
8. ) Stimulates sweating or piloerection
9. ) Inhibits salivation
10. ) Inhibits bladder contraction
11. ) Stimulates orgasm