Chapter 12

Question 1

CNS

a) components
b) number of neurons
c) functions

Answer 1

a) brain and spinal cord
b) 85 billion neurons in brain, 100 billion neurons in the spinal cord
c) processes sensory information and sends signals for muscles to contract or glands to secrete.

Question 2

Somatic division of the PNS is composed of what 2 types of neurons?

Answer 2

1) sensory neurons to the CNS from the head, body, and limbs and from receptors of the special sense of visions, hearing, taste, and smell
2) motor neurons that conduct impulses from the CNS to skeletal muscle only (voluntary)

Question 3

Autonomic division of the PNS is composed of what 2 types of neurons?

Answer 3

1) sensory neurons to the CNS from receptors such as the stomach, heart, and lungs
2) motor neurons from the CNS to smooth muscle, cardiac muscle, and glands (involuntary)

Question 4

PNS

Answer 4

All nervous tissue outside the CNS: ganglia, enteric plexuses, receptors.

Question 5

Ganglion

Answer 5

Small masses of nervous tissue outside the CNS but closely associated with the brain and spinal nerves

Question 6

Enteric plexuses

Answer 6

Networks of neutrons located in the walls of the organs of the gastrointestinal tract which help regulate the digestive system.

Question 7

ENS

Answer 7

The brain of the gut.

100 million neurons.

Involuntary - propels food through the GI tract

Secretes hormones.

Question 8

Sympathetic division of the autonomic system

Answer 8

Fight or flight

Question 9

Parasympathetic division of the autonomic system

Answer 9

Rest and digest

Question 10

What is contained in the cell body of a neuron?

Answer 10

Nucleus, cytoplasm, organelles

Question 11

Nissl bodies

Answer 11

Clusters of rough ER - site of ribosomes for protein synthesis - NO protein synthesis in the axon

Question 12

Dendrite

Answer 12

Nerve finer that emerges from the cell body. Act as the receiver or input portion of a neuron. Multiple and branched.

Question 13

Axon

Answer 13

Single nerve finer that acts as the output portion towards another neuron, muscle cell, or gland. Contains mitochondria but no rough ER, therefore no protein synthesis

Question 14

Axon hillock

Answer 14

Where the axon joins the cell body

Question 15

Initial segment

Answer 15

Their portion of the axon closest to the axon hillock

Question 16

Trigger zone

Answer 16

Where nerve impulses arise (between the axon hillock and the initial segment).

Question 17

Synapse

Answer 17

The site of communication between 2 neurons or a neuron and an effector (muscle or gland)

Question 18

Multipolar: structure and common locations

Answer 18

Several dendrites, single axon. Brain, spinal cord, motor neurons

Question 19

Bipolar: structure and common locations

Answer 19

Single dendrite, single axon. Eyes, ears, nose

Question 20

Unipolar: structure and common locations

Answer 20

Dendrites and axon fused together. Sensory receptors for touch, heat, pain

Question 21

Sensory neurons

Answer 21

Unipolar. Afferent pathways

Question 22

Motor neurons

Answer 22

Multipolar. Efferent pathways

Question 23

Interneurons

Answer 23

Mainly in the CNS. Afferent and efferent pathways. Multipolar

Question 24

2 types of nerve cells

Answer 24

1. neuron

2. neuroglia

Question 25

4 types of neuroglia in the CNS

Answer 25

1. astrocyte
2. ogliodendrocyte
3. microglia
4. ependymal

Question 26

Astrocyte

Answer 26

Neuroglia of the CNS

Largest and most numerous

Support, growth, protection, chemical balance

Question 27

Ogliodendrocyte

Answer 27

Neuroglia of the CNS

Smaller than astrocyte with fewer processes.

Forms and maintains myelin sheath (lipid/protein coating that insulates and increases speed)

Question 28

Microglia

Answer 28

Neuroglia of the CNS

Acts as phagocytes, removes debris and repairs damage

Question 29

Ependymal

Answer 29

Neuroglia of the CNS

Columnar, cuboidal cells that live in the ventricles of the brain and spinal cord that monitor and circulate cerebrospinal fluid.

Question 30

2 types of neuroglia in the PNS

Answer 30

1. Schwann cell

2. satellite cell

Question 31

Schwann cell

Answer 31

Neuroglia of the PNS

Forms myelin sheath

Participates in axon regeneration

Question 32

Satellite cell

Answer 32

Free floating neuroglia of the PNS

Provides structure and support

Question 33

Nucleus vs ganglion

Answer 33

Both are clusters of neuronal cell bodies. Nucleus is in the CNS, ganglia in the PNS

Question 34

Nerve vs tract

Answer 34

Bundles of axons. Tract in the CNS, nerve in the PNS

Question 35

Myelin

Answer 35

White in colour. Electrically insulates, and increases speed. Myelin increases through maturity.

Question 36

Nodes of ranvier

Answer 36

Gaps in the myelin sheath.

Question 37

Neurolemma

Answer 37

The outer covering of the schwann cell which encloses the myelin sheath. Only in the PNS.

Question 38

White matter

Answer 38

Primarily composed of myelin. Surrounds grey matter in the spinal cord BUT is surrounded by grey matter in the brain

Question 39

Grey matter

Answer 39

Unmyelinated portions of tissue: cell bodies, dendrites, neuroglia.

Question 40

Graded potential

Answer 40

Communication between electrically excitable cells used in short distances

Question 41

Action potential

Answer 41

Communication between electrically editable cells used in long distances

Question 42

Leak channel

Answer 42

Randomly alternates between open and closed. Located in nearly all cells: dendrites, cell bodies, axons

Question 43

Current

Answer 43

The flow of ions exchanges via ion channels