20. Nervous system

Question 1

What is the main function of the nervous system?

Answer 1

Coordinates sensory and motor functions by transmitting signals around the body.

Question 2

What is a neuron?

Answer 2

Consists of dendrites, axon, and soma; cannot divide.

Question 3

What are sensory (afferent) neurons?

Answer 3

Receive initial stimulus from environment.

Question 4

What are association (interneurons)?

Answer 4

Receive input from sensory neurons and send to motor neurons; make up 99% of body’s neurons.

Question 5

What are motor (efferent) neurons?

Answer 5

Stimulate target cells (effectors) to elicit a response.

Question 6

What do dendrites do?

Answer 6

Receive information to transfer to cell body.

Question 7

What is the axon hillock?

Answer 7

Site of action potential generation.

Question 8

What does an axon do?

Answer 8

Transfers impulses away from cell body.

Question 9

What are glial cells?

Answer 9

Supporting cells capable of dividing.

Question 10

What do oligodendrocytes do?

Answer 10

Produce myelin in CNS.

Question 11

What do Schwann cells do?

Answer 11

Produce myelin in PNS.

Question 12

What do microglia do?

Answer 12

Act as CNS phagocytes.

Question 13

What do ependymal cells do?

Answer 13

Circulate cerebrospinal fluid with cilia.

Question 14

What do satellite cells do?

Answer 14

Support cells in PNS.

Question 15

What do astrocytes do?

Answer 15

Support CNS neurons; maintain nutrient/mineral balance.

Question 16

What does the CNS include?

Answer 16

Brain, spinal cord, interneurons.

Question 17

What does the blood-brain barrier do?

Answer 17

Blocks passage of drugs, ions, pathogens; permeable to O2, CO2, glucose, small non-polar molecules.

Question 18

What does the PNS do?

Answer 18

Uses pre/postganglionic axons, neurotransmitters, and receptors to act on target organs.

Question 19

What does the somatic nervous system control?

Answer 19

Innervates skeletal muscle; voluntary or involuntary movements; uses ACh at neuromuscular junctions.

Question 20

What is the forebrain?

Answer 20

Largest brain part; includes olfactory bulb, thalamus, hypothalamus, basal ganglia, hippocampus.

Question 21

What is the limbic system?

Answer 21

Hippocampus, amygdala, hypothalamus; controls behavior and emotion.

Question 22

What does the diencephalon include?

Answer 22

Thalamus, hypothalamus, pineal gland.

Question 23

What are the cerebrum lobes?

Answer 23

Frontal: thought; Parietal: sensory; Temporal: sound; Occipital: vision.

Question 24

What is the midbrain?

Answer 24

Relay center for visual/auditory impulses; motor control.

Question 25

What is the hindbrain?

Answer 25

Cerebellum (balance), brainstem (midbrain, medulla oblongata, pons); medulla controls breathing, heart rate, GI activity.

Question 26

What does the sympathetic branch do?

Answer 26

Fight or flight: ↑ BP, HR, ejaculation, energy; inhibits digestion, urination, salivation.

Question 27

What does the parasympathetic branch do?

Answer 27

Rest and digest: ↓ HR; ↑ digestion, relaxation, sexual arousal.

Question 28

What increases action potential propagation speed?

Answer 28

Larger axon diameter & myelination.

Question 29

What is the resting potential?

Answer 29

-70 mV; K+ inside, Na+ outside.

Question 30

What happens in depolarization?

Answer 30

Na+ enters; if threshold (-50 mV) is reached, action potential fires.

Question 31

What happens in repolarization?

Answer 31

K+ exits to restore polarization.

Question 32

What is hyperpolarization?

Answer 32

Excess K+ leaves neuron before channels close.

Question 33

What is the refractory period?

Answer 33

Neuron is unresponsive until Na+/K+ pump restores ions.

Question 34

What do mechanoreceptors do?

Answer 34

Sense touch.

Question 35

What do thermoreceptors do?

Answer 35

Sense temperature.

Question 36

What do nociceptors do?

Answer 36

Sense pain.

Question 37

What do electromagnetic receptors do?

Answer 37

Sense light.

Question 38

What do chemoreceptors do?

Answer 38

Sense taste, smell, blood chemistry.

Question 39

What does the Na+/K+ pump do?

Answer 39

Maintains -70 mV; 3 Na+ out, 2 K+ in; uses ATP.

Question 40

What is acetylcholine (ACh)?

Answer 40

Neurotransmitter; binds post-synaptic receptors; involved in muscle contraction/relaxation; broken down by acetylcholinesterase.

Question 41

What are amino acid neurotransmitters?

Answer 41

Glutamate: excitatory; GABA & glycine: inhibitory.

Question 42

What are gas neurotransmitters?

Answer 42

NO; synthesized/released on demand.

Question 43

What are amino acid-derived neurotransmitters?

Answer 43

Epinephrine/norepinephrine: sympathetic system; E: bronchodilation, vasodilation in lungs/muscles; vasoconstriction to digestion/kidneys.

Question 44

How does transmission across a synapse occur?

Answer 44

AP opens Ca2+ channels; Ca2+ enters; NTs released to cleft; NTs bind post-synaptic receptors.