anatomy neurons and CNS quizlet

Action potentials are sent to slow the heart's rate of contraction. The axon sending these signals will most likely belong to which division of the nervous
system?

parasympathetic nervous system

What division of the nervous system is most specifically responsible for voluntary motor control?

somatic nervous system

It is important for newly developed neurons to form synapses with other neurons. Which cells are most responsible for guiding the formation of these particular junctions?

astrocytes

Which cell type helps determine capillary permeability in the CNS?

astrocytes

Which cell type is most associated with the production and flow of cerebrospinal fluid (CSF)?

Ependymal cells

Which neuron would activate to a muscle?

multipolar A

Which neuron is rare in the body and is found in the retina of the eye and the olfactory mucosa?

bipolar B

Which neuron is a sensory neuron found in a reflex arc?

Unipolar C

Which neuron is never myelinated?

b. bipolar

In a reflex arc, which neuron has its cell body inside the spinal cord?

multipolar A

Which neuron is common only in dorsal root ganglia of the spinal cord and sensory ganglia of cranial nerves?

C) Unipolar

Which of the following events would be directly affected if a neuron had a mutation that prevented the production of voltage-gated
Na+ channels?
graded hyperpolarization
depolarization leading to action potentials
graded depolarization
generating the resting membrane potential

depolarization leading to action potentials

Ions are unequally distributed across the plasma membrane of all cells. This ion distribution creates an electrical potential difference across the membrane. What is the name given to this potential difference?

resting membrane potential

What prevents the Na+ and K+ gradients from dissipating?

Na+ - K+ ATPase

The plasma membrane is much more permeable to K+ than to Na+. Why?

There are many more K+ leak channels than Na+ leak channels in the plasma membrane.

On average, the resting membrane potential is -70 mV. What does the sign and magnitude of this value tell you?

The inside surface of the plasma membrane is much more negatively charged than the outside surface.

Sodium and potassium ions can diffuse across the plasma membranes of all cells because of the presence of what type of channel?

leak channels

What is the role of calcium in synaptic activity?

Calcium influx into the synaptic terminal causes vesicle fusion.

Which part of the CNS sorts almost all sensory information ascending to the cerebral cortex?
hypothalamus
thalamus
pons
midbrain

thalamus

dorsal root ganglion

contains cell bodies of sensory neurons

afferent neurons

Nerve cells that carry impulses towards the central nervous system - Approaching

efferent neurons

Nerve cells that conduct impulses away from the central nervous system - Exit

Integration center (CNS)

processes information and directs motor output - brain/spinal cord

Peripheral Nervous System (PNS) divisions

two divisions:

1. sensory (afferent):
   somatic sends messages from skin and muscle to CNS and visceral sends organ impulses to CNS
2. motor (efferent) transmits impulse from CNS to organs muscles nd glands

motor (efferent) divisions

somatic and autonomic

Somatic Nervous System (SNS)

the part of the peripheral nervous system that controls voluntary movement of skeletal muscles

autonomic nervous system

the part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

sympathetic nervous system

the division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations

parasympathetic nervous system

the division of the autonomic nervous system that calms the body, conserving its energy

neuroglia

cells that support and protect neurons

neurons

a nerve cell; the basic building block of the nervous system, transmit electrical signals

4 CNS Neuroglia

astrocytes, oligodendrocytes, microglia, ependymal cells

2 PNS Neuroglia

Schwann cells and satellite cells

astrocyte

most abundant CNS neuroglia.
v branchy, associated with capillaries and helps exchange nutrients to neurons w capillaries

microglial cells

extremely small glial cells that remove cellular debris from injured or dead cells, repair injured neurons, phagocytosis

ependymal cells

line cavities of the brain and spinal cord, circulate cerebrospinal fluid, ciliated

oligodendrocytes

Type of glial cell in the CNS that wrap axons in a myelin sheath.

satellite cells

surround neuron cell bodies in PNS

Schwann cells

Supporting cells of the peripheral nervous system responsible for the formation of myelin.

T/F: all neurons have a cell body and at least one process

true

neuron cell body

contains nucleus. biosynthetic center of neuron

• in gray matter for CNS
• in clusters called ganglia for PNS

Dendrites

Branchlike parts of a neuron that are specialized to receive information.

what type of potential do dendrites use?

graded potentials

graded potential

a shift in the electrical charge in a tiny area of a neuron

axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

• conducting region of neuron

the neuron lacks which two cell organelles?

the Rough ER and Golgi apparatus

myelin sheath

a fatty tissue layer segmentally encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses hop from one node to the next

• protects, insulates, speeds up impulse

What forms myelin in PNS

Schwann cells when they wrap tightly around axon

nodes of ranvier

Gaps in the myelin sheath to which voltage-gated sodium channels are confined.

which marcromolecule is myelin mostly made of

lipid

T/F nonmyelinated fibers do not have schwaan cells because they dont have myelinated fibers

false, schwann cells can still be in nonmyelinated fibers, they just dont tightly wrap

white matter

Whitish nervous tissue of the CNS consisting of neurons and their myelin sheaths.

gray matter

Brain and spinal cord tissue that appears gray with the naked eye; consists mainly of neuronal cell bodies (nuclei) and lacks myelinated axons.

multipolar neurons

shape of a neuron that has multiple processes—the axon and two or more dendrites

bipolar neurons

A neuron that has only two projections (one axon/one dendrite) from the cell body

unipolar neuron

a neuron with one process extending from its cell body

sensory neurons

neurons that carry incoming information from the sensory receptors to the brain and spinal cord

• almost ALL are unipolar
• cell bodies in the ganglia in the pns are all sensory

motor neurons

neurons that carry outgoing information from the brain and spinal cord to the muscles and glands

• mostly multipolar
• cell bodies in CNS

interneurons

Central nervous system neurons that internally communicate and intervene between the sensory inputs and motor outputs

• mostly multipolar

membrane potential

The voltage across a cell's plasma membrane.

action potential

a neural impulse; a brief electrical charge that travels down an axon

Two types of ion channels

leakage and voltage gated

chemically gated channels

open with binding of a specific neurotransmitter

voltage gated channels

open and close in response to changes in membrane potential

mechanically gated channels

open and close in response to physical deformation of receptors

resting membrane potential

the electrical charge of a neuron when it is not active

• 70mV

when a membrane is at its resting membrane potential, it is called

polarized

describe the ionic composition of a resting membrane potential

• outside has lots of Na+
• inside has lots of K+

which diffuses out more: Na+ or K+? why does it matter?

K+ because it has more leakage channels. this means that the cell keeps losing internal positivity, making it more negative inside

what stabilizes the resting membrane potential?

sodium potassium pump, it maintains concentration gradient

when does the membrane potential change?

• Concentrations of ions across membrane change
• Membrane permeability to ions changes

changes in membrane potential produce which two types of signals?

graded potentials and action potentials

graded vs action potentials

Action: constant strength, brief, long distance. found in axons

Graded: Short distance, strength lessens over distance, variable strength. found in dendrites.

Depolarization

decreasing membrane potential when Na enters the cell, cell is more positive

• increases possibility of a nerve impulse

hyperpolarization

increase in membrane potential when it becomes more negative when K+ leaves cell.

• decreases possibility of nerve impulse

graded potentials can be either:

depolarizing or hyperpolarizing

action potential voltage

voltage changes by 100mV. goes to +30 mV

Types of Na+ gated channels

activation gates: closed at rest, but can open after depolarizing

inactivation gate: Open at rest, can be closed to prevent anymore Na+ leaving cell

K+ gated channels

these take longer to activate and don't seem to be fully open until membrane potential reaches about + 35 mv

Steps of generating an action potential

1. resting state: all gated Na+ and K+ channels are closed. leakage channels open
2. Depolarization: Na+ channels open
3. Repolarization: Na+ channels are inactivating, and K+ channels open
4. Hyperpolarization: some K+ channels remain open, and Na+ channels reset

threshold

the level of stimulation required to trigger a neural impulse
-50 mV

threshold voltage

-55mV

what opens at +30 mV

K+ channels, also action potential occurs

hyperpolarization voltage

-100 Mv

strong stimuli causes what type of action potentials

more frequent APs

rate of action potential speed depends on what?

1. axon diameter: larger is faster
2. degree of myelination:
   continuous conduction in unmyelinated axons is slow while saltatory conduction in myelinated axons is faster

which type of conduction is faster?

saltatory

Neurons are functionally connected by?

synapses

presynaptic neuron

conducts impulses toward the synapse, sending info

postsynaptic neuron

transmits impulses away from the synapse, receives info

What type of event is a transmission of nerve impulse from one neuron to another considered

chemical event

chemical events at the synapse

1) axon potential arrives at axon terminal of presynaptic neuron
2) causes voltage gated calcium channels to open and calcium enters the cells
3) calcium causes exocytosis of ntm into synaptic cleft
4) ntm diffuses across synapse
5) ntm binds to receptors on postsynaptic neuron
6) ion channels are opened, can be either excitatory or inhibitory. causes graded potential
7) reuptake, degredation or diffusion of leftover ntm

types of postsynaptic potentials

EPSP—excitatory postsynaptic potentials
IPSP—inhibitory postsynaptic potentials

EPSP (excitatory postsynaptic potential)

depolarizing graded potential in postsynaptic neuron in response to activation of excitatory synapse

• Na+ moves into cell and makes it less negative

IPSP (inhibitory postsynaptic potential)

synaptic potential that makes a postsynaptic neuron less likely to generate an action potential

• hyperpolarizing
• K+ moves out of the cell and it becomes more negative

T/F EPSP can generate action potential all by themselves

false

summation

when multiple synaptic inputs combine to influence the generation of AP in a neuron. It occurs when excitatory and inhibitory signals from multiple presynaptic neurons accumulate at the postsynaptic neuron.

two types of summation

temporal and spatial

temporal summation

One or more presynaptic neurons transmit impulses in rapid-fire order

spatial summation

Integration by a postsynaptic neuron of inputs (EPSPs and IPSPs) from multiple sources.