A&P 1 Exam 4

Neurons

initiate and conduct impulses

Neuroglia cells

facilitate the communication function of neurons and support/protect them

Dendrites

receive signals from other cells

Cell body

organizes and keeps the cell functional

Axon hillock

where impulses are generated in the neuron (part of the axon)

Node of Ranvier

allows fast diffusion of ions

the gaps between myelin sheaths on the axon of the PNS

Schwann cell

produces the myelin sheath in the PNS

What is inside the cell body?

Nissl bodies (Rough ER)

What do Nissl bodies do?

make neurotransmitters

Nucleus

controls the entire neuron

Axon

transfers signals to other cells and organs

Myelin sheath

increases the speed and protection of the signal, a fatty sheet that protects the axon

When does most myelination occur?

before birth

When do we reach adult like levels of myelination?

by 3 years old

Axon terminal

forms junctions with other cells

What is the only part of a neuron that can initiate and conduct impulses?

the axon

What are neurotransmitters?

the chemical message sent to other neurons or cells

What is the function of neuroglia cells?

support and protection of neurons

Do neuroglia generate impulses?

no

What are the neuroglia cells of the central nervous system?

astrocytes

ependymal cells

oligodendrocytes

microglia

Astrocytes

hold the neuron and capillaries anchored in the CNS (forming blood/brain barrier), assist in regulating/processing of information by neurons

What absorbs excess potassium ions and neurotransmitters to protect the whole brain?

astrocytes

Ependymal cells

line the spinal cord and ventricles of the brain and is involved in producing cerebrospinal fluid

Oligodendrocytes

responsible for myelination of CNS axons

Microglia

brain’s immune cells, remove dead cells and pathogens via phagocytosis

Large amounts of migroglia indicate what?

brain infection

What are the neuroglial cells of the peripheral nervous system?

satellite cells and Schwann cells

Satellite cells

surround neuron cell BODIES in ganglia

regulate neurotransmitter levels

absorb toxins to protect neuron cell bodies

Schwann cells

myelinate neurons in the PNS

maintain and regenerate neurons after injury

fatty cells that are rolled around axons

increase the transmission rate

Resting membrane potential

the difference in electrical potential across the plasma membrane when the cell is not stimulated or when the cell is in a state of relaxation

Membrane potential

the difference in voltage between the inside and outside of the cell

What causes a membrane potential?

the ions inside and outside of the cytoplasm

Typically, is the inside of the cell more negatively or positively charged?

negative

Typically, is the outside of the cell more negatively or positively charged?

positive

What is the resting membrane potential of a neuron?

-70mV

What is the resting membrane potential for non-excitable cells?

between -5 and -10mV

When is an impulse created?

when the membrane potential changes from the resting membrane potential

How do ions move across the plasma membrane?

channels and gates

Repolarization

returning to the resting membrane potential (becoming more negative)

What elements are used to cause depolarization?

Na+ is the most common, Ca+ and K+

Hyperpolarization

moving farther away from the resting membrane potential (becoming more negative)

What does hyperpolarization do?

inhibits actions

What factors influence whether the RMP is generated?

the phospholipid bilayer

ions movement across plasma membranes

proteins in the cytoplasm

How does the phospholipid bilayer affect the RMP?

allows fat soluble molecules to diffuse but not ions

What ways can ions move across a plasma membrane?

membrane protein channels

gated channels

transport proteins

unequal diffusion of Na+ and K+

How do proteins in the cytoplasm affect the RMP?

negatively charged proteins inside the PM are not outside the PM

Membrane protein channels

specific to a substance

embedded in the phospholipid bilayer and allow water soluble molecules and ions to cross

What are the types of gated channels?

ligand gated and voltage gated

Leak channels

always open to allow facilitated diffusion of ions

What are the most common leak channels?

K+ channels

Ligand (chemical) gated channels

involve ligands that bind to a specific receptor (usually NT in the nervous system)

Voltage gated channels

open only in response to voltage changes across the PM and when one side is negative and the other positive

Transport proteins/carrier molecules

proteins in PM that move ions and other substances

Name a type of transport protein

Na K Pump

Na+K+ Pump

embedded in the PM, Na+ goes OUT and K+ goes IN

How many Na+ ions are moved out of the cell with a Na+K+ Pump?

3

How many K+ ions are moved into the cell with a Na+K+ Pump?

2

What function do proteins in the cytoplasm have?

they are negatively charged to increase the difference in polarity of inside vs outside the cell

What are the functions of the nervous system?

maintain homeostasis, communicate, and coordinate the body

How does the nervous system communicate?

impulses and neurotransmitters

Central nervous system

brain and spinal cord

Peripheral nervous system

cranial nerves

spinal nerves

receptors

What does the peripheral nervous system do?

carries info between body and CNS and vice versa

Interneurons

found only in the CNS, relay incoming signals

What is the function of the CNS?

process/integrate information and then decide on response

What are the neurons of the PNS?

sensory neurons and motor neurons

Sensory/afferent neurons

takes information towards the CNS

What are the 2 types of sensory neurons?

visceral and somatic

Visceral sensory

sensory information from visceral organs TO CNS

Somatic sensory

sensory info from skeletal system, skin, muscles, hoings, and senses TO CNS

Motor/efferent neurons

carry info FROM CNS to body for response/reaction

Types of efferent neurons

somatic motor and autonomic motor

Somatic motor nervous system

sends motor info to skeletal muscles, voluntary

Autonomic motor nervous system

sends motor info to the heart, smooth muscles, and glands

involuntary

What is the process that oligodendrocytes use to myelinate the CNS?

each flat extension of the oligodendrocyte wraps around an axon segment creating the myelin sheath

Can an oligodendrocyte wrap around more than one axon?

yes

Can a Schwann cell wrap around more than one axon?

no

Neurilemma

outermost layer of the myelin sheath of the PNS, where the nucleus/cytoplasm/organelles get squeezed into during the “wrapping” process

Is this a CNS or PNS neuron?

CNS

Is this a CNS or PNS neuron?

PNS

Multiple sclerosis

an autoimmune disorder that attacks oligodendrocytes (CNS)

females are affected more

typically onset at age 15 to 50

EARLY DIAGNOSIS is key to prognosis

What are the symptoms of multiple sclerosis?

muscle weakness starting in the face then progressing

sensory difficulties

cognitive impairment

balance disorders

exacerbations/remissions

not always fatal

Scleroses

plaques in the brain that show up on MRIs as white spots in the brain, myelin sheaths are replaced with hardened scar tissue

What are the treatments for multiple sclerosis?

immune suppressing drugs

corticosteroids to reduce nerve inflammation

plasmapheresis

What are the risk factors for multiple sclerosis?

being female

running in the family

being from somewhere far away from the equator

smoking

Axonal transport

how substances move along the axon

How do we do axonal transport?

microtubules that run the length of axon and carrier molecules that move along microtubules

Anterograde axon transport

carries neurotransmitters, enzymes, organelles, etc, FROM neuron cell body TO axon terminal

Retrograde axonal transport

carries items FROM axon TO cell body

How do viruses stay latent in the body for so long?

they used retrograde axonal transport and stay in the nerve cell body, when the body is stressed it could be released like a neurotransmitter

Shingles

the chicken pox virus from childhood travels into the nervous system via axonal transport and stays dormant until released

Symptoms of shingles

painful rash, headache, fatigue, dizziness, sensitivity to light, tingling

How long can shingle symptoms last?

years

How are neurons classified?

structure and function

Unipolar neuron

a single elongated process with the cell body located off to the side

found in all sensory neurons except for nose and eyes

distal myelinated parts are the dendrites

Bipolar neuron

two processes separated by the cell body, found in eyes and nose ONLY

Multipolar neuron

have more than two processes, a single axon, and multiple dendrites

the most common type of neuron

What is the shape of the neuron on the left?

multipolar

What is the shape of the middle neuron?

bipolar

What is the shape of the neuron on the right?

unipolar