Nervous System Overview

Question 1

3 overlapping functions of the NS

Answer 1

1. Sensory receptors monitor changes inside and outside the body (stimulus and sensory input)
2. Processes and interprets sensory input (integration)
3. Dictates a response by activating effector organs (motor output response)

Question 2

Stimulus vs Sensory Input

Answer 2

Stimulus: changes detected inside of outside the body

Sensory input: information gathered by receptors

Question 3

CNS

Answer 3

Composed of brain and spinal cord
Integrating and command center
Nuclei present
Securely packing into cranium/intervertebral canal

Question 4

Nuclei

Answer 4

Clusters of neuronal cell bodies within the CNS

Question 5

PNS

Answer 5

Consists of nerves extending from brain and spinal cord (cranial and spinal nerves)
Peripheral neves link all regions of the body to CNS
Has ganglia

Question 6

Ganglia

Answer 6

Clusters of neuronal cell bodies in peripheral NS

Question 7

Gray matter

Answer 7

Gray coloured and surrounds hollow central cavities of the CNS
Forms H-shaped region in the spinal cord
Is composed primarily of neuronal cell bodies, dendrites, nonmyelinated axons
Surrounds white matter of CNS in cerebral cortex and cerebellum
Some gray tissue in the white matter (from embryonic development when they migrated there)

Question 8

White matter

Answer 8

Lies external to the gray matter of the CNS
Composed of myelinated axons
Consists of axons passing between specific regions of the CNS
White colour comes from the myelin sheaths around the axons

Question 9

Nervous tissue (and 2 major cell types)

Answer 9

Cells are densely packed and intertwined
Neurons: transmit electric signals
Support cells: neuroglia in CNS - nonexcitable, surround and wrap neurons

Question 10

Neurons

Answer 10

Basic structural unit of the NS

Specialized cells conduct electrical impulses along the PM

Question 11

Special characteristics of neurons (3)

Answer 11

Longevity: can live and function for a long time
Do not divide: fetal neurons lose their ability to undergo mitosis, neural stem cells are an exception
High metabolic rate: require abundant oxygen and glucose (die after a few minutes without them(

Question 12

Chromatophilic bodies

Answer 12

Nissl bodies
Clusters of rough ER and free ribosomes
Function to renew membranes of the neuron
Can be easily stained by basic dyes
Extend only into the basal part of dendrites and to the base of the axon hillock

Question 13

Dendrites

Answer 13

Extensively branching from the cell body
Transmit electrical signals toward the cell body
Function as receptive sites for receiving signals from other neurons

Question 14

Axons

Answer 14

Neuron usually only has one
Impulse generator and conductor
Transmits impulses away from the cell body
No chromatophilic bodies
No protein synthesis in the axon
Neurofilaments and microtubules provide strength and aid in transport of substances
Branches are infrequent

Question 15

Axonal transport

Answer 15

Movement of substances to and from the cell body

Question 16

Axon collaterals

Answer 16

Branches along the axon length

Rare

Question 17

Terminal arborization

Answer 17

Multiple branches of the axon at the end

End in knobs called terminal boutons

Question 18

Synapses

Answer 18

Sites where the neurons communicate
Most information passed through chemical messengers
Some info transmitted electrically through gap junctions

Question 19

Structural classification of neurons

1. Multipolar
2. Bipolar
3. Unipolar

Answer 19

1. Possess more than 2 processes (numerous dendrites and one axon)
2. Possess 2 processes (rare, found in eyes and olfactory)
3. Possess one short, single process (starts as bipolar during development, somatosensory)

Question 20

Motor (efferent) neurons

Answer 20

Carry impulses away from the CNS to effector organs
Most are multipolar
Cell bodies are in the CNS
Form junctions with effector cells

Question 21

Interneurons (association neurons)

Answer 21

Most are multipolar
Lie between motor and sensory neurons
Confined to the CNS

Question 22

Sensory (afferent) neurons

Answer 22

Transmit impulses towards the CNS
Virtually all are unipolar neurons
Cell bodies in ganglia
Short process divides into central process (into CNS) and peripheral process (to receptors)

Question 23

2 types of glial cells in PNS

Answer 23

Satellite cells

Schwann cells

Question 24

Astrocytes

Answer 24

Star shaped
Most abundant glial cells of the CNS
Regulate exchange of molecules between the circulatory system and NS contributing to the BBB
Regulate NT levels by uptake
Signal increased blood flow through capillaries in active regions of the brain
Control ionic environment around neurons

Question 25

Oligodendrocytes

Answer 25

Produce myelin sheaths around axons in the CNS Fewer branches than astrocytes Line up in small groups and wrap their cell processes around the thicker axons in the CNS Gaps between the myelin sheaths are the nodes of Ranvier

Question 26

Myelin sheath

Answer 26

Segmented structures that are composed of the lipoprotein myelin and surround the thicker axons of the body They form an insulating layer that prevents the leakage of electrical current from the axon, increase the speed of impulse conduction along the axon, and makes impulse propagation more energy-efficient

Question 27

Microglia

Answer 27

Defensive cells in the CNS Phagocytes - the migrate to, and engulf invading microorganisms and injured or dead neurons Do not originate in nervous tissue, like the other macrophages, they are derived from blood cells called monocytes during embryonic and fetal periods

Question 28

Ependymal cells

Answer 28

Form simple epithelium that line central cavity of the CNS Provide a fairly permeable layer between cerebrospinal fluid that fills the cavity and the tissue fluid that bathes the cells in the CNS Bear cilia that help circulate the cerebrospinal fluid

Question 29

Choroid plexus

Answer 29

Site of cerebrospinal fluid formation | Continuous with the ependyma projects into ventricles

Question 30

Schwann cells

Answer 30

Produce myelin sheaths around axons in the PNS | Unlike oligodendrocytes, each Schwann cell actually wraps around and forms the sheath, not just the processes that wrap

Question 31

Satellite cells

Answer 31

Surround neuron cell bodies in the ganglia

Question 32

Nerves

Answer 32

Cable like organs in the PNS Consist of numerous axons wrapped in connective tissue Most nerves contain myelinated and nonmyelinated sensory and motor axons Axon is surrounded by Schwann cells

Question 33

Endoneurium

Answer 33

Layer of delicate connective tissue surrounding the axon

Question 34

Perineurium

Answer 34

Connective tissue wrapping surrounding a nerve fasicle

Question 35

Nerve fasicles

Answer 35

Groups of axons bound into bundles

Question 36

Epineurium

Answer 36

Whole nerve is surrounded by tough fibrous sheath

Question 37

Location of cell bodies for 1. Motor neurons 2. Sensory neurons

Answer 37

1. In CNS | 2. Outside CNS