Ch 9 Intro To A&p

Front 1

What is the total number of cranial and spinal nerves in your body?

Back 1

The total number of cranial and spinal nerves in your body is

(12 pairs of Cranial nerves × 2) = 24

(31 pairs of spinal nerves × 2) = 62

Total = 86

Front 2

A nerve

Back 2

a bundle of hundreds to thousands of axons

plus associated connective tissue and blood vessels

that lie outside the brain and spinal cord.

Front 3

Ganglion

Back 3

a group of neuronal cell bodies lying outside the central nervous system (CNS)

Plural is ganglia

Front 4

Functions of the nervous system (3)

Back 4

Sensory function

Integrative function

Motor function

Front 5

Sensory function

Back 5

Sensory receptors detect internal stimuli, such as an increase in blood acidity, and external stimuli, such as a raindrop landing on your arm.

This sensory information is then carried into the brain and spinal cord through cranial and spinal nerves.

Front 6

Integrative function

Back 6

The nervous system integrates (processes) sensory information by analyzing and storing some of it and by making decisions for appropriate responses

An important integrative function is perception, the conscious awareness of sensory stimuli. Perception occurs in the brain.

Front 7

Motor function

Back 7

Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves.

Stimulation of the effectors causes muscles to contract and glands to secrete.

Front 8

The nervous system - two main subdivisions

Back 8

central nervous system (CNS), which consists of the brain and spinal cord

peripheral nervous system (PNS), which includes all nervous tissue outside the CNS

Front 9

Two type of Nervous tissue cells

Back 9

neurons (larger)
neuroglia (smaller and more numerous)

Neurons provide unique functions of the nervous system, such as sensing, thinking, remembering, controlling muscle activity, and regulating glandular secretions

Neuroglia support, nourish, and protect the neurons and maintain homeostasis in the interstitial fluid that bathes them.

Front 10

Neuron

Back 10

A nerve cell, consisting of
a cell body
dendrites
an axon

Front 11

Action potential

Back 11

An electrical signal that propagates along the
membrane of a neuron or muscle fiber (cell)

a rapid change in membrane potential that
involves a depolarization followed by a repolarization

Also called a
nerve action potential or nerve impulse as it relates to a neuron

a muscle action potential as it relates to a muscle fiber.

Front 12

Neuron Cell body

Back 12

The cell body contains a nucleus surrounded by cytoplasm that includes typical organelles such as rough endoplasmic reticulum, lysosomes, mitochondria, and a Golgi complex

Most cellular molecules needed for a neuron's operation are synthesized in the cell body

Front 13

Structure of a typical multipolar neuron

Back 13

Arrows indicate the direction of information flow:
dendrites >
cell body >
axon >
axon terminals >
synaptic end bulbs

Front 14

What roles do the axon and axon terminals play in the communication of one neuron with another?

Back 14

The axon conducts nerve impulses and transmits the message to another neuron or effector cell by releasing a neurotransmitter at its axon terminals

Front 15

Two kinds of processes (extensions) emerge from the cell body of most neurons

Back 15

multiple dendrites and a single axon

1st type - The cell body and the dendrites (= little trees) are the receiving or input parts of a neuron

2nd type - the axon, conducts nerve impulses toward another neuron, a muscle fiber, or a gland cell

The axon and axon collaterals end by dividing into many fine processes called axon terminals

Front 16

synapse

Back 16

The site where two neurons or a neuron and an effector cell can communicate is termed a synapse

The tips of most axon terminals swell into synaptic end bulbs

These bulb-shaped structures contain synaptic vesicles that store neurotransmitters

Front 17

Three types of neurons

Structural Classification

Back 17

Multipolar neurons

Bipolar neurons

Unipolar neurons

Front 18

Multipolar neurons

Back 18

usually have several dendrites and one axon

Most neuons in the brain and spinal cord are multipolar

Front 19

Bipolar neurons

Back 19

have one main dendrite and one axon

They are found in the retina of the eye, in the inner ear, and in the olfactory (olfact = to smell) area of the brain

Front 20

Unipolar neurons

Back 20

have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body

These neurons begin in the embryo as bipolar neurons.

During development, the dendrites and axon fuse together and become a single process

unipolar neurons function as sensory receptors that detect a sensory stimulus such as touch, pressure, pain, or thermal stimuli

Front 21

Functional Classification of neurons

Back 21

Functionally, neurons are classified according to the direction in which the nerve impulse (action potential) is conveyed with respect to the CNS.

Sensory or afferent neurons

Motor or efferent neurons

Interneurons or association neurons

Front 22

Sensory

Back 22

Neurons that carry sensory information from cranial and spinal nerves into the brain and spinal cord or from a lower to a higher level in the spinal cord and brain.

Also called afferent neurons

Front 23

Motor neurons

Back 23

Neurons that conduct impulses from the brain toward the spinal cord or out of the brain and spinal cord into cranial or spinal nerves to effectors that may be either muscles or glands

Also called efferent neurons

Front 24

Interneurons

Back 24

Neurons whose axons extend only for a short distance and contact nearby neurons in the brain, spinal cord, or a ganglion; they comprise the vast majority of neurons in the body.

Front 25

Neuroglia

Back 25

Cells of the nervous system that perform various supportive functions

Front 26

The neuroglia of the central nervous system

Back 26

astrocytes
oligodendrocytes
microglia
ependymal cells

Front 27

neuroglia of the peripheral nervous system

Back 27

Schwann cells
satellite cells

Front 28

Astrocytes

Back 28

Support neurons; protect neurons from harmful substances

help maintain proper chemical environment for generation of nerve impulses

assist with growth and migration of neurons during brain development

play a role in learning and memory

help form the blood–brain barrier

Front 29

Microglia

Back 29

Protect CNS cells from disease by engulfing invading microbes

migrate to areas of injured nerve tissue where they clear away debris of dead cells

Front 30

Oligodendrocytes

Back 30

Produce and maintain myelin sheath around several adjacent axons of CNS neurons.

Front 31

Ependymal cells

Back 31

Line ventricles of the brain (cavities filled with cerebrospinal fluid) and central canal of the spinal cord

form cerebrospinal fluid and assist in its circulation

Front 32

Schwann cells

Back 32

Produce and maintain myelin sheath around a single axon of a PNS neuron; participate in regeneration of PNS axons.

Front 33

Satellite cells

Back 33

Support neurons in PNS ganglia and regulate exchange of materials between neurons and interstitial fluid

Front 34

Myelin sheath

Back 34

Multilayered lipid and protein covering
formed by Schwann cells and oligodendrocytes
around axons of many peripheral and central nervous system neurons

Eventually, as many as 100 layers cover the axon

Gaps in the myelin sheath, called nodes of Ranvier appear at intervals along the axon

Axons with a myelin sheath are said to be myelinated
and those without it are said to be unmyelinated

Front 35

Contrast ganglion and nucleus

Back 35

ganglion (plural is ganglia) refers to a cluster of neuronal cell bodies located in the PNS.
As mentioned earlier, ganglia are closely associated with cranial and spinal nerves

a nucleus is a cluster of neuronal cell bodies located in the CNS

Front 36

Contrast nerve and tract

Back 36

a nerve is a bundle of axons that is located in the PNS
Cranial nerves connect the brain to the periphery, whereas spinal nerves connect the spinal cord to the periphery

A tract is a bundle of axons that is located in the CNS
Tracts interconnect neurons in the spinal cord and brain

Front 37

White matter

Back 37

White matter is composed primarily of myelinated axons

The whitish color of myelin gives white matter its name

Front 38

Gray matter

Back 38

The gray matter of the nervous system contains neuronal cell bodies, dendrites, unmyelinated axons, axon terminals, and neuroglia

It appears grayish because the cellular organelles impart a gray color and there is little or no myelin in these areas

Front 39

Central nervous system (CNS)

Back 39

That portion of the nervous system that consists of the brain and spinal cord

Front 40

Peripheral nervous system (PNS)

Back 40

The part of the nervous system that lies outside the central nervous system, consisting of nerves and ganglia.

Front 41

Central nervous system (CNS)

Back 41

That portion of the nervous system that consists of the brain and spinal cord

Front 42

Peripheral nervous system (PNS)

Back 42

The part of the nervous system that lies outside the
central nervous system, consisting of nerves and ganglia.

cranial nerves and their branches
spinal nerves and their branches
ganglia
sensory receptors

Front 43

PNS subdivided

Back 43

a somatic nervous system (SNS)

an autonomic nervous system (ANS)

an enteric nervous system (ENS)

Front 44

Which types of neurons carry input to the CNS and output from the CNS?

Back 44

Sensory (afferent) neurons carry input to the CNS

Motor (efferent) neurons carry output from the CNS.

Front 45

Somatic nervous system (SNS)

Back 45

The portion of the peripheral nervous system consisting of somatic sensory (afferent) neurons and somatic motor (efferent) neurons.

Front 46

Autonomic nervous system (ANS)

Back 46

Visceral sensory (afferent) and visceral motor (efferent) neurons.

Autonomic motor neurons
both sympathetic and parasympathetic
conduct nerve impulses from the central nervous system to smooth muscle, cardiac muscle, and glands

named because it was thought to be self-governing or spontaneous

Front 47

Enteric nervous system

Back 47

Brain of the gut

part of the nervous system that is embedded in the submucosa and muscularis of the gastrointestinal (GI) tract

governs motility and secretions of the GI tract

Front 48

Resting membrane potential

Back 48

The voltage difference between the inside and outside of a cell membrane when the cell is not responding to a stimulus

in many neurons and muscle fibers it is –70 to –90 mV, with the inside of the cell negative relative to the outside

Front 49

membrane potential

Back 49

, a difference in the amount of electrical charge on the inside of the plasma membrane as compared to the outside. The membrane potential is like voltage stored in a battery. A cell that has a membrane potential is said to be polarized

Front 50

Two types of ion channels

Back 50

Two types of ion channels are

leakage channels and gated channels (include Voltage-gated channels)

Front 51

Action Potential

Back 51

An electrical signal that propagates along the membrane of a neuron or muscle fiber (cell)

a rapid change in membrane potential that involves a depolarization followed by a repolarization

Also called a nerve action potential or nerve impulse

Front 52

Which channels are open -

During depolarization?

During repolarization?

Back 52

Voltage-gated sodium ions (Na+) channels are open during the depolarizing phase

voltage-gated potassium ions (K+) channels are open during the repolarizing phase of an action potential.

Front 53

polarized

Back 53

A cell that exhibits a membrane potential

typical value for resting membrane potential is -70 mV

Front 54

resting membrane potential

Back 54

an unequal distribution of ions on either side of the plasma membrane

a higher membrane permeability to potassium K+ than to sodium Na+.

The level of K+ is higher inside and the level of Na+ is higher outside

a situation that is maintained by sodium–potassium pumps

Front 55

excitability

Back 55

The ability of muscle fibers and neurons to respond to a stimulus and convert it into action potentials

Front 56

an action potential sequence

Back 56

voltage-gated Na+ and K+ channels open in sequence

voltage-gated sodium Na+ opens = depolarization
the loss and then reversal of membrane polarization

voltage-gated potasium K+ channels allows repolarization
recovery of the membrane potential to the resting level

Front 57

all-or-none principle

Back 57

if a stimulus is strong enough to generate an action potential, the impulse generated is of a constant size

Front 58

continuous conduction

Back 58

Nerve impulse conduction that occurs as a step-by-step process along an unmyelinated axon

Front 59

saltatory conduction

Back 59

a nerve impulse “leaps” from one node of Ranvier to the next along a myelinated axon

Front 60

impulse speed

Back 60

Axons with larger diameters conduct impulses faster than those with smaller diameters

myelinated axons conduct impulses faster than unmyelinated axons

Front 61

synaptic transmission

Back 61

series of events where Neurons communicate with other neurons and with effectors at synapses

Front 62

how a synapse functions

Back 62

a neurotransmitter is released from a presynaptic neuron into the synaptic cleft and then binds to receptors on the postsynaptic plasma membrane

Front 63

excitatory neurotransmitter

Back 63

depolarizes the postsynaptic neuron's membrane, brings the membrane potential closer to threshold, and increases the chance that one or more action potentials will arise

Front 64

inhibitory neurotransmitter

Back 64

hyperpolarizes the membrane of the postsynaptic neuron, thereby inhibiting action potential generation

Front 65

neurotransmitter is removed in three ways

Back 65

diffusion
enzymatic destruction
reuptake by neurons or neuroglia

Front 66

Important neurotransmitter

Back 66

acetylcholine
glutamate
aspartate
gamma amino butyric acid (GABA)
glycine
norepinephrine
dopamine
serotonin
neuropeptides
nitric oxide