Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIO 235 Midterm 2 > Chapter 12: Nervous Tissue > Flashcards

Chapter 12: Nervous Tissue Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

What are the two main subdivisions of the nervous system?

A

CNS - consists of brain and spinal cord

Peripheral nervous system (SNS, ANS, ENS) - consists of all nervous tissue outside the CNS (nerves, ganglia, enteric plexuses, sensory receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Define nerve

A

Bundle of hundreds-thousands axons plus associated connective tissue and blood cells (PNS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How many cranial and spinal nerves are there?

A

12 pairs of cranial nerves energy from the brain and 31 pairs of spinal nerves emerge from the spinal cord

Each nerve follows a defined path and serves a specific regions of the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define ganglion

A

Ganglia are small masses of nervous tissue, consisting primarily of neuron cell bodes (PNS)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define enteric plexuses

A

Extensive networks of neurones located in the walls of organs of the GI tract. The neurons within them help regulate the digestive system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define sensory receptors

A

Monitors changes in the external or internal environment (touch, olfactory, photoreceptors, etc.)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the subdivisions of the PNS?

A

Somatic nervous system (SNS) consists of

  1. sensory neurons that convey info to SNS from somatic receptors for special senses
  2. motor neurons that conduct impulses from CNS to skeletal muscles only (voluntary)

Automatic nervous system (ANS) consists of

  1. sensory neurons that convey info to SNS from automatic receptors mainly in visceral organs
  2. motor neurons that conduct nerve impulses from CNS to smooth & cardiac muscle, and glands (involuntary) - consists of 2 subdivisions (SD & PSD)

Enteric nervous system (ENS) is the ‘brain of the gut’ (involuntary)
- monitor changes in GI tract as well as stretching of its walls. governing contractions of smooth muscles, secretions, and activities of CI endocrine cells (hormones)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the subdivisions of the motor part of the automatic nervous system?

A

Sympathetic - fight or flight

Parasympathetic - rest and digest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the 3 basic functions of the nervous system?

A

Sensory function - detect internal stimuli and inform the brain and spinal cord

Integrative function - processes sensory info and makes decisions for appropriate responses

Motor function - elicited appropriate motor responses by activating effectors through cranial and spinal nerves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does a neuronal cell body contain?

A
  • Nucleus surrounded by cytoplasm that includes typical cellular organelles
  • Nissil bodies - free ribosomes and prominent clusters of rough ER
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the structure of a dendrite?

A

Usually short, tapering, and highly branched

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define axon hillock

A

A cone shaped elevation of the cell body where the axon meets

The part of the axon closet to the axon hillock is the initial segment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define trigger zone

A

The junction of the axon hillock and initial segment where nerve impulses arise and from which they travel from

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Protein synthesis occurs in an axon

True or false

A

False - there is no rough ER present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define axon collaterals

A

Side branches from the axon, typically occur at a right angle which end by dividing into many fine processes called axon terminals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Define varicosities

A

A variation of axon terminals (other than synaptic end bulbs) that are a strong of swollen lumps

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are slow and fast axonal transport?

A

These are transport systems that carry material from the cell body the the axon thermals and back

Slow - moves materals about 1-5 mm per day (unidirectional towards axon terminal), supplying new axoplasm (cytoplasm) to developing or regenerating axons and replenishes axoplasm in growing and mature axons

Fast - moves materials 200-400mm per day, using proteins that function as motors to move materials along the surfaces of microtubules of the cytoskeleton (bi-directional), supplying organelles/synaptic vesicles, and taking vesicles to be recycled

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the 3 structural classifications of neurons?

A

Multipolar neuron - have several dendrites and one axon - most common in the brain and spinal cord and motor neurons

Bipolar neurons - one main dendrite and one axon - found in the eye, inner ear, and olfactory area

Unipolar neuron - dendrites and one axon that are fused together to form a continuous process that emerges from the cell body, the begin as bipolar neurons in the embryo and fuse to become a single process functioning as sensory receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the 3 functional classifications of neuronal cells?

A

Sensory (afferent) - either contain sensory receptors at distal ends or are located just after sensory receptors that carries informaition into the CNS (usually unipolar)

Motor (efferent) - convey AP away from CNS to effectors in the PNS through cranial or spinal nerves (usually multipolar)

Interneurons - mainly located within SNS between sensory and motor neurons the process incoming sensory info and elicit a motor response (usually multipolar)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Define neuroglia

A

Make up ~1/2 the volume of CNS that actively participate in the activities of nervous tissue

Smaller than neurons and do not generate or propagate AP and they can multiply and divide

They fill spaces where neurons were in times of injury

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

List the 2 types of neuroglia located in the PNS

A

Schawann cells

Satellite cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

List the 4 types of neuroglia located in the CNS

A

Astrocytes
Oligodendrocytes
Microglia
Ependymal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe astrocytes and their function

A

Star shaped cells that are the largest and most numerous type of neuroglia

Makes contact with blood capillaries, neurons and pie matter, functioning to:

  • support neurons with microfilaments
  • wrap capillaries to isolate them from harmful substances and secretes chemicals to create a BBB
  • secrete chemicals that regulate growth, migration, and interconnection in embryos
  • maintain appropriate environment for nerve impulses
  • play a role in learning/memory by influencing formation of neural synapses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe oligodendrocytes and their function

A

resemble astrocytes but are smaller and fewer processes

Processes are responsible for forming and motioning the metering sheath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe microglia and their function

A

Small cells with slender processes that give off numerous spine-like projections which function as phagocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe ependymal cells and their function

A

Cuboidal to columnar cells arranges in a single layer that passes microvilli and cilia, lining the ventricles and central canal if spinal cord

process, monitors, and assist in circulation of CSF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe schwann cells and their function

A

encircle PNS axons forming the myelin sheath

also participate in axon regeneration, which is more easily accomplished in the PNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Describe satellite cells and their function

A

flat cells surround cell bodies of neurons of PNS ganglia , providing structural supporting regulates the exchanges of materials between neuronal cell bodies and ISF

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How is the myelin sheath formed in the PNS?

A

Each schwann cell wraps about 1mm of a single axons length by spiring 100 times around the axon to create the myelin sheath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Define neurlemma

A

The outer nucleated cytoplasmic layer of the schwann cell, which encloses the myeline sheath

When injured, the neurolemma aids in regeneration by forming a regeneration tube that guides and stimulates growth of the axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Define nodes of Ranvier

A

Gaps in the myelin sheath

Found in both PNS and CNS (just fewer)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

How is the myelin sheath formed in the CNS?

A

oligodendrocytes put forth about 15 broad, flat processes that spiral around CNS axons, forming a sheath

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Axons in the CNS display little regrowth after injury

True or False

A

True - thought to be due in part to the absence of a neurolemma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

A childs myelination is the same from childhood to adulthood

true or false

A

False - myelination increases as we age

35
Q

What is the difference between a ganglion and a nucleus?

A

Ganglion - cluster of neuronal cell bodies in PNS

Nucleus - cluster of neuronal cell bodies in CNS

36
Q

What is the differences between a tract and a nerve?

A

Tract - bundle of axons located in CNS

Nerve - bundle of axons located in PNS

37
Q

White vs. Gray matter

A

White matter is composed of primarily myelinated axons

Gray matter contains neuronal cell bodies, dendrites, unmyelinated tons, axon terminal, and neuroglia

In the spinal cord, white matter surrounds of inner core of gray patter that looks like and H

38
Q

Graded potentials vs. action potentials

A

Graded potentials are used for short-distance communication only
ex. develops in a sensory receptors in the fingers

Action potentials allow for communication over long distances
ex.travels along axon into the CNS and causes release of NT at a synapse with an interneuron

39
Q

muscle AP vs nerve AP

A

Muscle AP is an AP in a muscle fiber

Nerve AP occurs in a neuron (nerve cell)

40
Q

Define membrane potential

A

Electrical potential differences across the membrane

In excitable cells, this voltage is termed the resting membrane potential

The flow of ions along the membrane due to the potential is termed current

41
Q

Define electrochemical gradient

A

When ion channels are open, they allow specific ions to move across the membrane down their electrochemical gradient - a concentration (chemical) difference plus an electrical difference

42
Q

Define leak channels

A

Gates of leak channels randomly alternate between open and closed positions

43
Q

Define ligand-gated channel

A

Gates open and close in response to binding of a ligand (chemical) stimulus

44
Q

Define mechanically-gated channels

A

Gates open or closes in response to mechanical stimulation in the form of vibration, touch, pressure, or tissue stretching

45
Q

Define voltage-gated channel

A

Gate opens in response to a change in membrane potential

These participate in the generation of action potentials in the axons of all types of neurons

46
Q

Define polarized cell

A

A cell that exhibits a membrane potential

47
Q

What are the 3 factors that contribute to the resting membrane potential

A

Resting potential - equal negative ions along the inner membrane as there is positive ions along the outer membrane

  1. Unequal distributions of ions in ECF and cytosol - since the membrane has more K+ leak channels than Na+ leak channels, K+ ions leave the cell faster than the Na+ ions enter the cell, making the inner more negative and the outer more positive
  2. Inability of most anions to leave cell - trapped anions cannot follow K+ out of the cell as they are attached to nondiffusable molecules such as ATP
  3. Electrogenic nature of the Na+-K+ ATPases - expels 3 Na+ ions for every 2+ ions imported contributing to the negativity f the resting potential
48
Q

Define graded potential

A

Small deviation from the resting membrane potential that makes the membrane either more polarized (inside more neg) or less polarized (inside less neg)

When the response makes the membrane more polarized it is termed hyper polarizing graded potential

When the response makes the membrane less polarized it is termed depolarizing graded potential

49
Q

When do graded potentials occur?

A

When a stimulus causes mechanically-gated or ligand-gated channels to open or close in an excitable cells membrane

they mainly occur in the dendrites and cell body of a neuron as this is where these channels are abundant

50
Q

Define decremental conduction

A

Graded potentials die out as the stream along the membrane as the charges are lost across the membrane through leak channels

51
Q

Define summation

A

Graded potentials add together, become stronger and lasting longer

The result is a larger depolarizing graded potential

52
Q

What is the neuronal threshold?

A

An action potential occurs in the membrane of a neuron when depolarization reached approx -55mV

53
Q

Define:

Subthreshold stimulus
Threshold stimulus
Suprathreshold stimulus

A

Subthreshold stimulus: a weak depolarization that cannot bring the membrane potential to threshold

Threshold stimulus: a stimulus that is just strong enough to depolarize the membrane to threshold

Suprathreshold stimulus: a stimulus that is strong enough to depolarize the membrane above threshold

54
Q

Describe the all-or-none principle

A

Once threshold is reached an action potential is generated

The stimulus does influence the amplitude of the AP, but if it is depolarized above threshold, it will fire more frequently

55
Q

Describe the following stages in an action potential:

Resting phase
Depolarizing phase
Repolarizing phase
After hyperpolarizing phase

A

Resting - All Na+ and K+ channels are closed and there is small buildup of negative charges along the inside of the cell and positive charges along the outside of the cell

Depolarizing - membrane potential reaches threshold, Na+ channels open, moving into the neuron, creating a positive charge inside the cell causing the membrane to depolarize

Repolarizing - Na+ channels close and K+ channels open and membrane begins to depolarize as K+ ions leave the neurone and negative charges buildup along inside the cell

After hyper polarizing - As K+ ion channels remain one and the membrane potential become even more negative (-90 mV) then at rest. The ion channels then close and membrane potential returns to resting of -70mV

56
Q

What is a refractory period? Differentiate between absolute and relative refractory periods

A

Refractory period - cell cannot generate another AP in response to a normal threshold stimulus

Absolute - Even strong stimuli cannot initiate an AP as the Na+ channels are inactivated and cannot reopen before returning to the resting states

Relative - a second AP can be initiated by a larger than normal stimulus as K+ channels are still open but Na+ channels have reached their resting state

57
Q

Define propagation

A

APs keep their strength as it spreads along the membrane

58
Q

Define continious and saltatory conduction

A

Continuous: step-by step depolarization and depolarization of each adjacent segment of the plasma membrane (occurs in unmyelinated axons and muscle fibres)

Saltatory: special mode of AP propagation that occurs along myelinated axons, because of the uneven distribution of voltage-gated channels (jumping from nodes of ranvier)

59
Q

What 3 major factors affect the speed of propagation?

A
  1. amount of myelination - APs propagate more rapidly in myelinated axons
  2. Axon diameter - larger diameter axons propagate APs faster due to large surface area
  3. Temperature - warmer axons propagate faster
60
Q

Differentiate between the following nerve fibers:

A fibers
B fibers
C fibers

A

A fibers: largest diameter, myelinated, have a brief absolute refractory period

B fibers: myelinated, exhibit saltatory conduction, have a somewhat larger absolute refractory period than A fibers

C fibers: smalled diameter, unmyelinated, have the longest absolute refractory period

61
Q

How can your sensory systems detect stimuli of differing intensities if all nerve impulses are the same size?

A

Frequency of action potentials - the greater intensity of stimuli, the more frequent the APS

Total recruited neurons - the greater intensity of stimuli, the more sensory neurons activated

62
Q

Compare graded potentials and action potentials on the following characteristics:

Origin 
Channels 
Conduction 
Amplitude 
Duration 
Polarity 
Refractory period
A

Origin: GP (dendrites/cell body) AP (trigger zones)

Channels: GP (ligand or mechanically gates) AP (voltage for Na+ and K+)

Conduction: GP (decremental, short distance) AP (propagate, long distance)

Amplitude: GP (1-50 mV depending on stimulus) AP (all or none ~100mV)

Duration: GP (longer) AP (shorter)

Polarity: GP (hyper polarizing or depolarizing) AP (depolarizing, followed by re-polarizing, and then resting phase)

Refractory period: GP (not present, summation can occur), AP (present, summation cannot occur)

63
Q

Define axodendritic and axoaxonic synapses

A 
Axodendritic = from axon to dendrite 
Axoaxonic = from axon to axon
64
Q

How are APs conducted at electrical synapses?

A

APS conduct directly between the plasma membranes of adjacent neurons through structures called gap junctions, which act as tunnels to connect the cytosol of the two cells directly

This allows for faster communication and synchronization of a group of neurons/muscle fibres

65
Q

How are APs conducted at chemical synapses?

A

Membranes of pre- and post-synaptic neurones in a chemical synapse are separated by a synaptic cleft

The presynaptic nuron releases NTs that diffuses and binds to the post synaptic neuron, creating a postsynaptic potential (graded potential)

It turns an electrical signal into a chemical signal that is received by postsynaptic neuron and turned back into an electrical signal

66
Q

Define synaptic delay

A

The time requires for processes at a chemical signal is about 0.5msec and is the reason chemical synapses are slower than electrical synapses

67
Q

Describe how a typical chemical synapse transmits a signal (7 steps)

A
  1. AP arrives an synaptic end bulb of presynaptic axon
  2. Depolarizing phase of AP causes an influx of Ca2+ ions
  3. Increased Ca2+ in the neuron triggers exocytosis of synaptic vesicles
  4. Nts diffuse across cleft and bind with postsynaptic receptors
  5. Binding opens the channels and allows particular ions to flow across membrane
  6. Ion influx changes the voltage acrsss the membrane, termed postsynaptic potential (either depolarizing/EPSP or hyperpolarizing/IPSP)
  7. Depolarizing postsynaptic potential can trigger an AP when it reached threshold
68
Q

Describe the two types of neurotransmitter receptors

A

Ionotropic - contains NT binding site and an ion channel (ligand-gated channel); in absence of the NT the channel is closed (mostly excitatory)

Metabotropic - contains NT binding site but lacks ion channel but is coupled to a separate ion channel called a G protein; when a NT binds, the G protein opens (or closes) the channel or indirectly activates second messenger which opens or closes it (mostly inhibitory)

69
Q

How can NTs be removed from the synaptic cleft?

A

Diffusion - diffuse away where it can no longer exert an effect

Enzymatic degradation

Uptake - NT taken back into presynaptic cell (reuptake), or transported into neighbouring neuroglia (uptake)

70
Q

Distinguish between spatial and temporal summation

A

Spatial - summation of postsynaptic potentials in response to stimuli that occur at different locations in the membrane of a postsynaptic cell at the same time

Temporal - summation of postsynaptic potentials in response to stimuli that occur in the same locations in the membrane of a postsynaptic cell at different times

71
Q

Define neursecretory cells

A

certain neurons in the brain that also secrete hormones

72
Q

Define acetylcholine NT

A

small molecule NT released by many PNS neurons and by some CNS neurons

Excitatory when minded with ionotropic receptors but inhibitory when in it binds to metabotropic receptors

73
Q

Describe the functions of the following amino acids:

Glutamate
GABA & glycine

A

Glutamate (excitatory) - most excitatory neurons in CNS and 1/2 in PNS communicate via glutamate; binds to ionotropic to cause influx of Na+ causing a EPSP

GABA & glycine (inhibitory) - GABA is found only in the CNS; binding at ionotropic receptors opens Cl- channels

74
Q

Describe the functions of the following biogenic amines:

norepinephrine
epinephrine
dopamine
serotonin

A

NE - arousal, dreaming, and regulating mood; serves also as a hormone

epinephrine - also serves as a hormone

dopamine - emotions, addictions, and pleasurable experiences; regulates skeletal muscle tone and some aspects of movement

serotonin - concentrated in raphe nucleus and involved in perception, temp regulation, control of mood, appetite, and induction of sleep

75
Q

Define catecholamines

A

Have an amino group and a catechol ring composed of 6 carbons and 2 adjacent hydroxyl groups

They are synthesizes from the amino acid tyrosine and inactivation occurs via reuptake where they are recycled or destroyed

Ex. DA, NE, Epi

75
Q

Define catecholamines

A

Have an amino group and a catechol ring composed of 6 carbons and 2 adjacent hydroxyl groups

They are synthesizes from the amino acid tyrosine and inactivation occurs via reuptake where they are recycled or destroyed

Ex. DA, NE, Epi

76
Q

Describe the function of nitric oxide and carbon monoxide

A

NO - an important excitatory NT in brian, spinal cord, adrenal garden, & neves to penis; formed on demand & acts immediately & briefly as it is a highly reactive free radical

CO - excitatory Nt produced in brain; formed on demand as needed; might protect against excess neuronal activity

77
Q

Describe the the following neuropeptides:

Enkephalins
Endorphins

A

Enkephalins - inhibit pain impulses by suppressing release of substance p

Endorphins - inhibit pain by blocking release of substance P

Both may have role in memory and learning, body temp control, sexual activity and mental illness

  • use the same receptors as opioids
  • substance P is released by neurons that transmit pain related input from peripheral pain receptors
78
Q

Describe the various types of neural circuits in the nervous system:

Simple series circuit
Diverging circuit
Converging circuit
Reverberating circuit
Parallel after-discharge circuit
A

A circuit is a functional group of neurons that process specific types of information

Simple series - a single presynaptic neuron stimulates a single postsynaptic neuron, and so on

Diverging circuit - a single presynaptic neuron stimulates several post synaptic neurones at the same time

Converging circuit - several presynaptic neurons stimulates one postsynaptic neuron

Reverberating circuit - incoming impulse stimulates the 1st neuron, which stimulate the 2nd, which stimulates the 3rd, and so on. Branches from later neurons synapse with earlier one sending impulses back through the circuit again and again

Parallel after-discharge circuit - a single presynaptic neuron stimulates a group of neurons, each which synapses with a common postsynaptic cell

79
Q

Describe plasticity and neurogenesis

A

Plasticity is the capability to change based on experience which can include sprouting of new dendrites, protein synthesis, changes in synaptic connections

Regeneration is the capability to replicate or repair themselves

*Despite plasticity, in the CNS little or no repair of damage to neurons occur

80
Q

Define neurogenesis

A

The birth of new neurons for undifferentiated stem cells

There are neurogenesis is some areas of the brain (hippocampus) but not present in other regions and the spinal cod due to:

  • inhibitory influences from neuroglia
  • absence of growth-stimulating cues that were present during fetal development
81
Q

What is the role of the neurolemma in regeneration?

A

Axons and dendrites that are associated with a neurolemma in the PNS may undergo repair if the cell body is intact, the Schwann cells are functional, and scar tissue formation does not occur too rapidly.

Chromatoylsis: 24-48 hrs after injury the Nissil bodies break up into granular masses

Wallerian degeneration: 3-5 days after the part of the axon distal to the damaged region becomes swollen and breaks up into fragments; the myelin sheath also deteriorates, however, the neurolemma remains

The Schwann cells on either side multiple and grow toward each other forming a regeneration tube across the injured area

82
Q

Briefly outline the following disorders:

Multiple sclerosis (MS) 
Epilepsy
A

MS - a progressive destruction of myelin sheaths surrounding neurons in the CNS which slows and then short-circuits propagation of nerve impulses

Epilepsy - short, recurrent attacks of motor, sensory, or psychological malfunction, initiated by abnormal, synchronous electrical discharges from millions of neurons in the brain, perhaps from abnormal reverberating circuits

BIO 235 Midterm 2 (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions