1 - nerve impulses and synaptic transmissions

what are the 2 main parts of the nervous system?

1. central nervous system (CNS)

2. peripheral nervous system (PNS)

the CNS includes the _____ and ________

brain and spinal cord

where is the CNS located?

the CNS is located in the dorsal body cavity (back side of body)

what are the main roles of the CNS?

• process info (like a control center)

• interprets sensory signals (like pain, sound, etc.)

• send instructions to muscles/organs (motor output)

the PNS includes ___________

all nerves outside the CNS

what nerves is the PNS made of?

1. spinal nerves → which connect to the spinal cord

2. cranial nerves → which connect to the brain

what are the 2 major functions of the PNS?

1. carry signals between the body and CNS

2. help body react and function properly

what is known as the “gut brain”?

the enteric nervous system (ENS) is known as the “gut brain”

where is the ENS found?

the ENS is found in the walls of the gastrointestinal (GI) tract

what does the ENS control?

the ENS controls the digestive functions → like food movement and enzyme release

T or F: the ENS can work independently but also connects with CNS

TRUE

what are the 2 main functional divisions of the PNS?

1. sensory (afferent) division

2. motor (efferent) division

what does the sensory (afferent) division do?

the sensory (afferent) division carries info TO the CNS (brain and spinal cord)

what are the 2 main types of sensory fibres of the sensory division?

1. somatic sensory fibers

2. visceral sensory fibers

the somatic sensory fibers are from the ____, _____, and ____

from the skin, muscles, and joints

example: feeling pain or temperature

the visceral sensory fibers are from the _________

from the internal organs (stomach, heart, etc…)

example: feeling full after eating

what does the motor (efferent) division do?

the motor (efferent) division carries instructions FROM the CNS to body

where does the motor (efferent) division send signals to?

to the muscles and glands → which are the effectors

what are the 2 subdivisions of the motor (efferent) division?

1. somatic nervous system (SNS)

2. autonomic nervous system (ANS)

the somatic nervous system controls ______ movements

voluntary

example: moving your hand or walking

the autonomic nervous system controls ______ functions

involuntary

example: heartbeat, digestion, breathing

the nervous tissue consists of 2 principal cell types: ____ and ____

1. neuroglia (glial cells)

2. neurons (nerve cells)

what are neuroglia (glial cells)?

neuroglia are small cells that surround and wrap delicate neurons

what are neurons (nerve cells)?

neurons are excitable cells that transmit electrical signals

what are the 4 main types of neuroglia of the CNS?

1. astrocytes

2. microglial cells

3. ependymal cells

4. oligodendrocytes

T or F: neuroglia do not suport CNS neurons

FALSE; neuroglia DO support CNS neurons

what are the 2 main types of neuroglia of the PNS?

1. satellite cells

2. Schwann cells (neurolemmocytes)

T or F: astrocytes are the least common type of glial cells

FALSE; astrocytes are the MOST common type of glial cell

what are the 3 main things astrocytes attach to?

1. neurons

2. capillaries

3. synapses

T or F: astrocytes are star-shaped

TRUE

what are the 6 main functions of astrocytes?

1. support and hold neurons in place

2. help with nutrient exchange between blood and neurons

3. guide young neurons during brain development

4. keep chemical balance around neurons

5. respond to nerve signals and chemicals

6. help with processing info in brain

microglial cells are known as the _____ of the neuroglia cells

defenders

what is the physical description of microglial cells?

small cells with thorny branches

what is the function of microglial cells?

microglial cells constantly monitor neurons and move to injury sites when needed

microglial cells act like _____ cells because they eat _____ and clean up _____

microglial cells act like immune cells because they eat bacteria and clean up dead cells

what are ependymal cells known as?

ependymal cells are known as fluid movers

where are ependymal cells found?

ependymal cells line the brain and spinal cord cavities

what is the shape of ependymal cells?

• squamous (flat) or columnar (tall)

• may have cilia

what does the cilia on ependymal cells do?

the cilia on ependymal cells help circulate cerebrospinal fluid (CSF)

T or F: ependymal cells create a barrier between CSF and brain/spinal tissue

TRUE

oligodendrocytes are the ________ makers of the neuroglia cells

insulation makers

T or F: oligodendrocytes wrap around CNS nerve fibers

TRUE

what is the main function of oligodendrocytes?

the main function of oligodendrocytes is to make myelin sheaths (fatty layers)

what are myelin sheaths and what is their function?

myelin sheaths = fatty layers

function = help speed up nerve signals

T or F: satellite cells are supportive to the CNS

FALSE; satellite cells are supportive to the PNS

which type of neuroglia cell is known as the bodyguard cells?

satellite cells = bodyguards

satellite cells ____ neuron cell bodies in the PNS

surround

satellite cells in the PNS function like which neuroglia cell in the CNS?

satellite cells of the PNS function like astrocytes of the CNS

what are the 2 major functions of satellite cells?

1. support and protect neurons

2. regulate the environment around neurons (nutrients, ions, etc..)

what are Schwann cells of the PNS known as?

Schwann cells of the PNS are known as the myelin markers

Schwann cells (type of neuroglia) belong to which NS: CNS or PNS?

Schwann cells belong to the PNS

schwann cells wrap around ______ in the PNS

nerve fibers

the function of Schwann cells is to make ______

myelin sheath (insulation) → for faster signal transmission

Schwann cells of the PNS are like ________ of the CNS

oligodendrocytes

T or F: Schwann cells have a key role in repair because they regenerate damaged peripheral nerves

TRUE

neurons are the ________ of the nervous system

main building blocks

what is the job of neurons (nerve cells)?

neurons send and receive electrical signals (impulses)

T or F: neurons are very large and highly specialized

TRUE

T or F: neurons have a limited lifespan of about 10 years

FALSE; neurons can live a lifetime → they don’t usually die off

T or F: neurons are amitotic

TRUE

amitotic = do not divide → can’t easily replace themselves

T or F: neurons do not require lots of energy

FALSE; neurons require lots of energy

• need a constant supply of oxygen and glucose

• have a high metabolic rate

what are the 2 basics of a neuron’s structure?

1. cell body (soma)

   • contains nucleus and organelles

   • main centre for cell activity

2. processes (extensions that come out cell body)

   • dendrites (receive signals)

   • axon (sends signals)

what is resting membrane potential (RMP)?

RMP is the resting voltage across a neuron’s membrane

T or F: RMP is when the neuron is sending a signal

FALSE; RMP is when the neuron is NOT sending a signal

with RMP, the inside of a neuron is _____ compared to the outside

negative

what is the typical RMP?

~ -70 mV

why are neurons called excitable cells?

neurons are called excitable cells because they can change their membrane potential quickly

what does neurons being excitable cells allow them to do?

neurons being excitable cells allows them to send electrical signals (nerve impulses)

all cells have some membrane potential, but neurons use it to ______

communicate

what are the 2 main things that create the RMP?

1. differences in ion concentration

2. differences in membrane permeability

what is the ion concentration in the ECF (outside)?

more Na+ (sodium) and Cl- (chloride)

what is the ion concentration in the ISF (inside)?

more K+ (potassium) and negative proteins

uneven distribution of ion concentrations in RMP creates a __________

charge difference

in RMP, the neuron’s membrane is ____ permeable to ____ than Na+

more permeable to K+

• K+ leaks out of the cell easily

• Na+ can’t enter as easily

in RMP, the membrane being more permeable to K+ makes the inside _______

more negative

what mineral/chemical element plays the main role in setting up RMP?

K+ (potassium)

what are gated ion channels?

gated ion channels are special protein “doors” in the membranes (of neurons, excitable cells, muscle cells, etc…)

T or F: gated ion channels only open when triggered (by voltage, chemicals, etc.)

TRUE

when open, ions move based on what 2 major factors?

1. concentration gradient (high → low)

2. electrical charge (opposites attract)

gated ion channels are key for sending ________

nerve impulses

movement of ions = _______

changes in membrane potential

T or F: channels are ion specific

TRUE

what is the difference between chemically gated and voltage gated ion channels?

chemically gated ion channels: open in response to binding of appropriate NTM

voltage-gated ion channels: open in response to changes in membrane potential

generating RMP: diagram explanation (no question)

what is action potential (AP)?

action potential is a brief reversal of membrane potential with a change of voltage of ~100mV → from -70mV (resting) to +30mV (spike)

action potential is the main way _______ over long distances

neurons send signals

action potential occurs only in _________ (neurons and muscle cells)

excitable cells

where does action potential happen?

action potential happens on axons

T or F: action potential weakens as it travels

FALSE; action potential does not weaken as it travels

action potential is triggered by which type of gated channel?

voltage-gated channels

what are the 4 steps of generating an action potential?

1. resting state

2. depolarization (rising phase)

3. depolarization (falling phase)

4. hyper polarization (undershoot)

   

what is the membrane potential voltage for resting state in action potential?

-70mV

in resting state of AP, voltage-gated Na+ and K+ channels are: open or closed?

closed

T or F: only leak channels (small Na+/K+ flow) maintain resting potential

TRUE

in resting state of AP, are the Na+ channel activation and inactivation gates open or closed?

activation gates = closed

inactivation gates = open

in resting state of AP, K+ channels are: closed or open?

closed

what triggers membrane depolarization in AP?

local graded potential

• temporary change in membrane potential in a small, specific area of the neuron

• triggered by a stimulus (signal from another neuron or sensory input)

what gated channels in depolarization of AP open?

voltage-gated Na+ channels open

• Na+ rushes in

• type of positive feedback mechanism (more Na+ channels open)

what is the depolarization minimum threshold voltage?

~ -55mV

• once reached, all Na+ channels open → leads to large spike to +30mV

in the repolarization of AP, the Na+ channels: inactivate or activate?

inactivate → stop Na+ entry