CH. 12 study guide

Organs of the peripheral nervous system (PNS)

nerves (bundles of nerve fibers) wrapped in fibrous CT

• sensory division(sensory neurons) + motor division(motor neurons)

Nerve fiber =

axon

Organs of the central nervous system (CNS)

brain + spinal cord

The CNS is where ________ occurs

integration (where the brain and spinal cord analyze, interpret, and process sensory input)

In the PNS, the ________ branch transmits information about the _______ to the CNS and the ________ branch transmits “________” from the CNS, to the effectors

In the PNS, the sensory branch transmits information about the environment to the CNS and the motor branch transmits “commands” from the CNS, to the effectors

three given properties of neurons

1. Excitability(irritability)

2. Conductivity

3. Secretion

Property of Neuron - Excitability( _________ )

( irritability )

Neurons respond to stimuli much more dramatically than other cells

what begins the excitability response?

which property of neurons is this?

Ligand-gated channels in soma & dendrites receive neurotransmitters(NT)

excitability

Property of Neuron - Conductivity

the ability to propagate (repeat) action potentials over long distances towards other cells

What is the ability to propagate (repeat) action potentials over long distances towards other cells?

Conductivity

In conductivity, the “moving” action potential is called a _______ or ______

nerve signal or nerve impulse

Property of Neuron - Secretion

Release of NT from the axon terminus

Functional Classes of Neurons

_______(Receive) → ________(Process) → _____(Send command)

Sensory/Input (Receive) → Interneurons (Process) → Motor neurons(Send command)

1. Sensory ( _____ ) : detect _______

( afferent ) , stimuli

Sensory neurons take _____ to the ______ from a _________

info, CNS, receptor

what takes info to the CNS from a receptor?

sensory neurons

Interneurons ( _____ _____ ):

____% of body’s neurons

( association neuron )

90%

which neurons are only in the brain and spinal cord (CNS)?

Interneurons

Interneurons: Integrate ______: process, ______, retrieve ____, decide how to _____

information, store, info, react

Motor ( ______ ) neurons send _________ from _____ to ______

(efferent) commands, CNS, effectors

Effectors =

muscles and glands

which type of neuron send commands from CNS to effectors?

motor neurons / efferent neurons

2 branches of Peripheral nervous system:

1. Sensory division

2. Motor division

Sensory division

Branch that sends info from receptors or sensory organs → to the CNS about the internal & external environment

Which branch of the PNS sends info from receptors or sensory organs to → the CNS about the internal & external environment?

Sensory division

In which division/branch of the PNS does info travel through Sensory/Afferent neurons?

In sensory division

Motor division

branch that sends commands from the CNS to → the effectors, usually muscles and glands

Which division of the PNS sends commands from the CNS to → the effectors, usually muscles and glands?

Motor division

In which division/branch of the PNS does info travel through Motor/Efferent neurons (carry commands to Effectors) ?

Motor division

Motor division = PNS → _______ to → _________

CNS to → the effectors

Sensory division = PNS → __________ to → _______

receptors or sensory organs to → the CNS

Multipolar Neuron

# axon, # dendrite, _____ neurons

location:

1 axon, at least 2 dendrites,

Most common → motor neurons,

In spinal cord & brain - interneurons

which type of polar neuron is In spinal cord & brain - interneurons?

multipolar neuron

Unipolar neuron

# axon, # dendrite, _____ neurons

1 axon, 1 dendrite, Sensory neurons

Axonal Transport is important because supplies are in _____

soma

Anterograde: Away from the ______; towards the _____

“Walks” on microtubule “roads”

soma, axon

Anterograde: which motor protein carries organelles, membrane components, enzymes, cytoskeletal parts down the axon → carry supplies to the axon + axon terminus?

Kinesin motor protein

Anterograde “______” on microtubule “_____”

Walks, roads

Retrograde: Back towards the _____ → ______ must return to the soma where they can be processed & disposed of → ______ with digestive enzymes important in this

soma, wastes, lysosome

Retrograde: what must return to the soma where they can be processed & disposed of?

wastes

(Retrograde) Which type of protein carries material in the opposite direction?

Ex:

Dynein protein

Old synaptic vesicles

Retrograde: Transport system can be “_______” by . . .

can be “hijacked” by tetanus toxin, viruses (herpes simplex, rabies, polio)

4 neuroglia of the CNS (AMEO)

Ependymal cells, Microglia, Astrocytes, Oligodendrocytes

2 neuroglia of the PNS

Schwann Cells, Satellite Cells

Ependymal cells: _______ cells that line _______ _____ _____ 🧠

Produce ________ fluid ( ____ )

______ circulate CSF to _____ 🛀 the brain & spinal cord

Cuboidal, internal brain cavities

cerebrospinal, CSF

Cilia, bathe

Microglia: ______ cells in the (PNS or CNS?) that develop from _____

Complete brain “____-_____” several times a day

Immune, CNS, WBC

check-up

What does microglia develop from?

White blood cells

What do Phagocytes do in microglia?

“clean up” cell debris, microorganisms, etc

Which neuroglia of the CNS are More active with infection, trauma, stroke?

microglia

Astrocytes:

Abundant – More than ____% in some areas

_________ feet contact capillaries

90, Perivascular

Which neuroglia of the CNS are part of Blood-Brain Barrier?

Astrocytes

(Astrocytes) Blood-Brain Barrier/BBB

limits what can exit capillaries in the brain → protective

Astrocytes absorb _________ and ______ secreted by neurons

neurotransmitters, K+

Astrocytes allow neurons to return to _______ phase → neurons ____💀 when they don’t _____ enough

resting, die, rest

Oligodendrocytes: ________ in the CNS

Each oligo wraps its processes around ____ ______(axon) of several nearby ______

Occurs from # weeks in utero to adolescence

Myelination, nerve fibers, neurons

14

What do oligodendrocytes form?

the myelin sheath for neurons in the CNS

Schwann Cells: _______ in the PNS

Schwann cell wraps completely around 1 (portion of) nerve fiber → many Schwann cells are needed to myelinate 1 axon

Myelination,

which cells in the PNS make Cytoplasm squeeze outward?

schwann cells

Schwann Cells: Neurilemma

Outer coil of Schwann; contains nucleus & most cytoplasm

What is the Outer coil of Schwann; contains nucleus & most cytoplasm?

Neurilemma

Schwann Cells: Endoneurium

Inner-most layer of connective tissue that surrounds the Schwann cell and the axon → 1st wrapping of CT

What is the Inner-most layer of connective tissue that surrounds the Schwann cell and the axon → 1st wrapping of CT?

Endoneurium

Satellite cells

These surround the ______ (not axons) of PNS neurons

somas

Which cells of the PNS Electrically insulate the cell body?

Satellite cells

Which cells of the PNS Regulate chemicals near neuron?

Satellite cells

which glial cells myelinate in the CNS and which myelinate in the PNS?

Oligodendrocytes in the CNS, Schwann cells in the PNS

is myelin hydrophilic or hydrophobic?

myelin is a _________ membrane this _________ of the ______ speeds up the nerve signal

hydrophobic,

phospholipid, insulation, axons

Myelin

Insulating of axons (nerve fibers) which increases the speed of nerve impulses

How does Myelin work? white people like farmers

1. WRAP - They wrap their plasma membranes around an axon

2. PHOSPHOLIPID - The plasma membrane is mostly phospholipid and therefore hydrophobic

3. LEAKAGE - Hydrophobic membrane repels charged ions -> less leakage

4. FASTER - Less ion leakage -> faster propagation of action potential

Regeneration

with stem cells → return of functional tissue

What includes the return of functional tissue?

Regeneration . . . uses stem cells!

Fibrosis

without stem cells → non-functional scar tissue

What creates non-functional scar tissue?

Fibrosis . . . doesn’t use stem cells

Nerve Regeneration only occurs in the axons of the _____ *only if the ________ is intact & has _________

Nerve Regeneration only occurs in the axons of the PNS *only if the soma is intact & has endoneurium

Nerve Regeneration: ____ fiber

distal end of axon _____ w/o supplies from soma

_______ cells degenerate, unwrap.

_________ clean up

Cut fiber, dies, Schwann, Macrophages

Process of Regeneration

1. Soma swells, ER breaks up, nucleus moves off center, 

• distal axons degenerate

• schwann cells degenerate

2. Regeneration tube forms

• Muscle atrophies (shrink) from lack of use

• Tube is Schwann cells, basal lamina & endoneurium

• Schwann cells tind the muscle fiber

• Axon stump sends growth processes

3. Regeneration tube (Schwann cell) guides new axon back to its effector (muscle fiber)

• Other processes retract 

4. When completed:

• Soma goes back to original size & shape

• Re-innervated muscle fibers regrow → muscle regains function

• Not always successful

Process of Regeneration “SAMSGRR”

1. Soma Swells (and nucleus moves off-center)

2. Axon Degenerates (distal stump)

3. Muscle Atrophies

4. Schwann Cells Degenerate (then create tubes)

5. Growth Processes (Sprouting)

6. Regeneration Tube Guides the new axon

7. Regrowth & Recovery (Soma returns to normal)

Causes of Tay Sachs Disease

Recessive genetic disease (takes 2 alleles)

• Enzyme in lysosomes normally degrades a lipid, GM2 - enzyme is NOT functional

• GM2 builds up and becomes toxic

GM2 builds up in neurons

• Lysosome burst + neuron dies

• Disrupts nerve signals

• Destroys the nervous system

Tay Sachs Disease: what happens to GM2 when the cause is a Recessive genetic disease?

GM2 - enzyme is NOT functional

GM2 builds up and becomes toxic

Tay Sachs Disease: What happens when GM2 builds up in neurons?

• Lysosome burst + neuron dies

• Disrupts nerve signals

• Destroys the nervous system

Symptoms of Tay Sachs Disease:

Motor neuron dies → Loss of motor skills (crawling, etc)

Sensory neurons die → Vision and hearing loss (sensory)

Death by age 4yr

What are these symptoms of?

• Motor neuron dies → Loss of motor skills (crawling, etc)

• Sensory neurons die → Vision and hearing loss (sensory)

• Death by age 4yr

Tay Sachs Disease

Multiple Sclerosis is an ________ _______

Autoimmune disease: immune cells attack oligodendrocytes that myelinate the neurons of the brain & spinal cord (CNS)

what disease has immune cells attack oligodendrocytes that myelinate the neurons of the brain & spinal cord (CNS)?

autoimmune disease (multiple sclerosis)

Oligos degenerate and are replaced with hard scar tissue in __________

sclerosis

multiple sclerosis interferes with communication between _____ and ______ (body)

brain, PNS

Symptoms of Multiple Sclerosis

Bridge is broken 🌉, so it affects both:

Motor function: Weakness in limbs, one at a time

Sensory function: Numbness, loss of vision, one eye, shock sensation in the neck

What are these symtpoms of ?

Motor function: Weakness in limbs, one at a time

Sensory function: Numbness, loss of vision, one eye, shock sensation in the neck

Multiple Sclerosis

Presynaptic cell ______ NT (neurotransmitter)

releases

Postsynaptic ______ the NT (neurotransmitter)

receives

Axodendritic: Synapses on a ______ (~____%)

dendrite, 80

Axosomatic: Synapses on _____ (~ ____%)

soma, 20

Axoaxonic: Synapses on ______ of _______ neuron ( ____ )

axon, postsynaptic, rare

🐸 Loewi Experiment

The ________ component

• Stimulated ______ nerve to slow 1st heart down

• _______ fluid from 1st heart, put into 2nd heart

• 2nd heart ______ down: some chemical (___) was transferred

chemical, vagus, Removed, slowed, NT

Loewi Experiment: Frog #1 🐸

vagus nerve stimulated → heart rate reduced

Loewi Experiment: Frog #2 🐸🐸

took liquid from where they stimulated vagus nerve in frog #1 → vagus nerve not stimulated, but heart rate reduced

Neural Pathways

Galvani: ⚡️

Ramon y Cajal followed _______ thru tissue

Cells separated by gaps ( ______ )

electricity caused muscle contraction

neurons

(synapses)

Electrical Synapses are ______! (light switch = on or off) 💡

faster

In which synapse do Ions diffuse from one cell to next thru gap junctions?

electrical synapse

which synapse has some neurons, cardiac, single-unit smooth muscle?

electrical synapse