Central Nervous System

neuron

nerve cells
long-lived - a lifetime or more
amitotic - most cannot divide
extremely high metabolism (glucose and O2)

neuroglial cells

do not carry an impuls
scaffolding, insulation and support of neurons
half the total brain mass

internodes

regions between the nodes of Ranvier
underneath the cells
underneath the myelin

nodes of Ranvier

unmyelinated regions
regularly spaced
increase the speed of impulse conduction as impulse will jump from node to node
channels

myelin

lipid produced by Schwann cells
protects and electrically insulates some axons
increases speed of neural impulse conduction

synaptic end bulb

in the axonal terminals
bulbs at the end of the axon that links to dendrites of another nerve or cell

axonal terminals

specialized area to send signal to next neuron

axon

conducting component
carries signals away from cell body, one per neuron, can be extremely long or short, branch into axonal terminals

axon hillock

region just outside cell body where signals from dendrites are summed - if enough stimulus is received, an impulse is conducted down the axon

dendrites

receptive regions (receptors)
sends signals to cell body
hundreds per cell body
graded stimuli and threshold

nissl bodies

rough ER
makes proteins

cell body (soma)

biosynthetic center
contains the usual organells and highly functional ER

structure of a neuron

cell body or soma
nissl bodies
dendrites
axon hillock
axon
axonal terminals
synaptic end bulb

ganglia

clusters of neuron cell bodies within the PNS

nuclei

clusters of neuron cell bodies within the CNS

tracts

bundles of neurons in the CNS

nerves

parallel bundles of neurons in the PNS

gyrus/gyri

elevated ridges

sulci

shallow grooves

fissure

deep groves

IPSP

inhibitory post-synapse potential
if there is reduced permeability to Na+ ions or increased permeability of K+ ions, the membrane potential becomes more negative and further from threshold making it less likely that a new action potential will occur

EPSP

excitatory post-synapse potential
if positive ions flow into nerve cell, it moves the membrane towards threshold making it easier to set off a new action potential

absolute refractory period

the period from the opening of the Na+ gate to the closing of the Na+ gate
no new action potentials can be started
nothing can change it

relative refractory period

when K+ gates open & repolarization is occurring
a second action potential can be initiated but only by a stronger than normal stimulus

saltatory conduction

occurs in myelinated axons
impulses jump from one node of Ranvier to the next
allows for faster, more energy efficient transmission
speed of transmission in a large myelinated neuron may reach 100 m/s

synaptic potentiation

repeated use of a synaptic pathway, causes buildup of Ca+ supplies in the region - results in release of more neurotransmitters and easier action potential generation
plays a role in learning and efficiency

coma

not just deep sleep
oxygen usage drops
signal doesn't get through RAS (reticular activating system)
doesn't activate

contusion

bruising of the brain leading to permanent damage

concussion

alteration in brain function due to a blow to the head, can lead to a buildup of tau proteins

structure of neurons

mutlipolar - 3 or more processes, 1 axon, lots of dendrites
bipolar - 2 processes, 1 dendrite, 1 axon
unipolar - single process, cell body placed in center of axon instead of near dendrites

neurons and their functions

sensory neurons - afferent, carry signal TO the CNS
interneuron - within the CNS, creates an association between stimulus and response
motor neurons - efferent, carries OUT response of CNS

motor neurons

efferent, carries OUT response of CNS

interneuron

within the CNS, creates an association between stimulus and response

sensory neurons

afferent, carry signal TO the CNS

bipolar neuron

2 processes
1 dendrite
1 axon

multipolar neuron

3 or more processes
1 axon
lots of dendrites

unipolar neuron

single process
cell body placed in center of axon instead of near dendrites

CNS neuroglial cells

oligodendrites
astrocytes
ependymal cells
microglia

oligodendrites

produce myelin, insulate thick CNS neuron fibers

astrocytes

most abundant and versatile
supports neurons and anchors them to capillaries
control capillary permeability, helping to deliver nutrient to neurons
guide development of young neurons
recycle neurotransmitters, mop up K+
can also influence brain functioning & information processing

ependymal cells

line central cavities of brain and spinal cord
form barrier between CNS and central cavities
produces, filters, and circulates CSF

microglia

protect against invasion
immune system is blocked out of CNS - the immune cells of the CNS

membrane ion channels

chemically-gated
voltage-gated
mechanically-gated

chemically-gated channels

opened by binding of a molecule with a receptor

voltage-gated channels

opened when nearby membrane depolarizes

mechanically-gated channels

physical deformation, used by many receptors (hair receptors), manipulation

surface of cerebral hemispheres

gyrus/gyri - elevated ridges
sulci - shallow grooves
fissure - deep groves

frontal lobe

personality
emotions
intelligence
attention
concentration
judgment
body movement
problem solving
speech (speak and write)

parietal lobe

sense of touch (pain, temp, etc.)
distinguishing size, shape, and color
spatial perception/discrimination
visual perception (recognition)

temporal lobe

understanding language
memory
hearing
sequencing
organization

occipital lobe

vision

lobes of the brain

frontal lobe
parietal lobe
temporal lobe
occipital lobe
insula (pyschology)

major wave patterns seen on an EEG

alpha
beta
theta
delta

alpha

8-13 Hz
indicates calm, awake state

beta

14-30 Hz
awake, concentrating or "working" on something

theta

4-7 Hz
common in children, abnormal in adults, can appear when concentrating

delta

4 or less Hz
high amplitude, seen when asleep, sign of brain damage in awake adults (signifies dampening of the RAS or under anesthesia)

types of neurotransmitters

acetylcholine
biogenic amines
amino acids
neuropeptides
purines

acetylcholine

excitatory to skeletal muscles
inhibitory to others

biogenic amines

indolamines - serotonin, histamine
catecholamines - epinephrine, norepinephrine, dopamine

amino acids

excitatory - glutamate
inhibitory - glycine, GABA

neuropeptides

inkephalins, endorphins

purines

excitatory - ATP
inhibitory - adenosine

types of neural integration

serial processing
parallel processing
divergence
convergence
reverberating series
parallel after discharge

serial processing

one neuron stimulates the next, etc. (predictable reflex)

parallel processing

circuits branch

divergence
convergence
reverberating series
parallel after discharge

divergence

one incoming fiber triggers increasing number of neurons down the circuit

convergence

lots of neurons converge to create a strong stimulation or inhibition

reverberating series

fires down a line of neurons but 1 will loop back and refire an earlier neuron
controls rhythmic activity (breathing)

parallel after discharge

cognitive, higher order processes

major fissures in the brain

longtitudinal fissure
transverse fissure
central sulcus
precentral sulcus
postcentral sulcus
lateral sulcus
parieto-occipital sulcus

conduction velocities of neurons (speed)

Group A fibers - large diameter, thickly myelinated, very fast, 150 m/s (300 mph)
Group B fibers - smaller diameter, lightly myelinated, intermediate speed, 100 m/s (30 mph)
Group C fibers - smaller diameter, unmyelinated, very slow, 1 m/s (2 mph or less)

Group A fibers

large diameter, thickly myelinated, very fast, 150 m/s (300 mph)

Group B fibers

smaller diameter, lightly myelinated, intermediate speed, 100 m/s (30 mph)

Group C fibers

smaller diameter, unmyelinated, very slow, 1 m/s (2 mph or less)

Collections of nerve cell bodies outside the central nervous system are called \______________.

ganglia

Meningitis can be caused by infection of the central nervous system by bacteria. Which cells would be most responsible for removing the infection?

microglia

A stimulus traveling toward a synapse appears to open calcium ion channels at the presynaptic end, which in turn promotes fusion of synaptic vesicles to the axonal membrane.

True

An inhibitory postsynaptic potential (IPSP) is associated with \_________________.

hyperpolarization

Nerve impulses leading to the brain carry information about cool temperatures on the skin. The nerve fibers sending these signals will most likely belong to which division of the nervous system?

sensory (afferent) division

Which of the following is not a chemical class of neurotransmitters?

nucleic acid

Schwann cells are functionally similar to \_____________.

oligodendrocytes

These cells in the CNS have cilia that move in order to circulate cerebrospinal fluid.

ependymal cells

Which of the following describes the nervous system integrative function?

analyzes sensory information, stores information, makes decisions

Which of the following is not a function of astrocytes?

provide the defense for the CNS

During depolarization, the inside of the neuron's membrane becomes less negative.

True

Which of the choices below describes the ANS?

motor fibers that conduct nerve impulses from the CNS to smooth muscle, cardiac muscle and glands

A neuron that has as its primary function the job of connecting other neurons is called a(an) \__________________.

interneuron

What does the central nervous system use to determine the strength of a stimulus?

frequency of action potentials

The period after an initial stimulus when a neuron is not sensitive to another stimulus is the \______________.

absolute refractory period

The term central nervous system refers to the \______________.

brain and spinal cord

Axon diameter and degree of myelination determine nerve impulse conduction velocity.

True

Immediately after an action potential has peaked, which of the following channels will open?

voltage-gated potassium channels

A second nerve impulse cannot be generated until \_________________.

the membrane potential has been reestablished

Which of the following correctly describes a graded potential?

it can have amplitudes of various sizes

Nerve impulses are sent to slow the heart's rate of contraction. The nerve fibers sending these signal will most likely belong to which division of the nervous system?
sensory (afferent) division
somatic nervous system
sympathetic division
parasympathetic division

parasympathetic division

Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle?
cholinesterase
acetylcholine
norepinephrine
gamma animobutyric acid

acetylcholine

In myelinated axons the voltage-regulated sodium channels are concentrated at the nodes of Ranvier.

True

An action potential is regarded as an example of a positive feedback. Which of the following examples below best illustrates the positive feedback aspect of an action potential?
A threshold stimulus will cause the opening of voltage gated sodium ion channels that will cause further depolarizing stimulus. This stimulus will open still more voltage gated sodium ion channels.

Potassium permeability is about 25 times greater than sodium ions.

The sodium potassium pump consistently moves ions along as ATP is available, and regardless of membrane potential changes.

Voltage gated potassium ion channels open slowly and remain open long enough to cause hyperpolarization.

A threshold stimulus will cause the opening of voltage gated sodium ion channels that will cause further depolarizing stimulus. This stimulus will open still more voltage gated sodium ion channels.

Which of the following is FALSE or INCORRECT?
An excitatory postsynaptic potential occurs if the excitatory effect is greater than the inhibitory effect but less than threshold.

A nerve impulse occurs if the excitatory and inhibitory effects are equal.

An inhibitory postsynaptic potential occurs if the inhibitory effect is greater than the excitatory, causing hyperpolarization of the membrane.

A nerve impulse occurs if the excitatory and inhibitory effects are equal.