Nervous System Pt.1/ CH 7

Question 1

What is the nervous system made up of?

Answer 1

made up of organs and structures that are composed of nervous tissues

Question 2

What are the major functions of the nervous system?

Answer 2

1. receiving external and internal stimuli (things that can trigger a response or reaction in an organism)
2. transmitting electrochemical signals (action potentials)
3. Integrating (combination/brought together) these electrochemical signals
4. coordinating body functions

Question 3

What are the nervous systems divisions for?

Answer 3

to categorize and understand the nervous system in different ways

Question 4

What are the two different kinds of nervous system divisions?

Answer 4

1. anatomical divisions
2. functional division

Question 5

Anatomical Division

Answer 5

1. Central Nervous System (CNS): consists of brain and spinal cord
2. Peripheral Nervous System: includes all the nervous tissue outside the brain and spinal cord

Question 6

Functional Division

Answer 6

1. Somatic Nervous System: innervates voluntary movements and innervates organs that we can consciously control, like the skeletal muscles
2. Autonomic Nervous System: innervates involuntary functions and innervates organs you can’t consciously control, like the heart and digestive system
   - Parasympathetic: associated with the “rest and digest” response, promoting relaxation and digestion
   - Sympathetic: associated with the “fight or flight” response, preparing the body for intense physical activity or dealing with stress

Question 7

What are neurons?

Answer 7

• functional unit of the nervous system
• responsible for synthesizing and transmitting electrochemical signals

Question 8

What are the different parts of neurons?

Answer 8

• dendrites: receiving signals/stimuli from other neurons or sensory receptors
• soma: (cell body) carries out general cellular functions
• axon hillock: where the action potential is generated
• axon: transmits action potentials to other neurons or target cells
• axon terminals: transmit and amplify action potentials to communication with other neurons or muscles

Question 9

morphological classification of neurons

Answer 9

• neurons can be classified based on the # of cellular projections they have:
  1. Pseudounipolar neurons: have a short, singular projection
  2. Bipolar neurons: have 2 projections (dendrite and axon)
  3. Multipolar neurons: have multiple dendrites and a single axon
  4. Anaxonic neurons: have multiple projections, but no distinct axon

Question 10

Functional classification of neurons

Answer 10

Sensory (afferent) neurons: specialized to detect & respond to different types of sensory information (touch, smell, temperature)
Motor (efferent) neurons: relay motor signals from the central nervous system (CNS) to effectors, such as muscles or glands
- motor neurons can be further divided into somatic and autonomic neurons
- autonomic neurons are responsible for regulating involuntary bodily functions and can be further divided into parasympathetic and sympathetic divisions
Interneurons: responsible for integration within the nervous system. play a role in:
- regulating motor activity in response to sensory signals
- establishing complex networks that facilitate higher processing function like thought and memory
- interneurons are morphologically diverse, meaning they come in different shapes and forms

Question 11

What do glial cells do?

Answer 11

fulfill various supporting roles in the nervous system, both in the central nervous system (CNS) and the peripheral nervous system (PNS)

Question 12

What are the different kinds of glial cells and their functions ?

Answer 12

1. Astrocytes: regulated the content of extracellular fluid and provide support to CNS neurons
2. Satellite cells: control the content of extracellular fluid and support PNS neurons
3. Ependymal cells: line the ventricles of the brain and the central canal of the spinal cord
4. Microglia: play a role in immunity as phagocytes, helping to protect the nervous system
5. Oligodendrocytes: produce the myelin sheath in the CNS, which helps with conduction of nerve impulses
6. Schwann Cells: produce the myelin sheath in the PNS, also assisting with the conduction of nerve impulses

Question 13

What roles do astrocytes have in the nervous system?

Answer 13

Protective and Regulatory roles in the nervous system

Question 14

What is the astrocytes protective role in the nervous system?

Answer 14

1. help form the blood-brain barrier, which protects the brain from harmful substances
2. aid in the formation and maintenance of synapses (the connections between neurons)
3. contribute to neurogenesis (the generation of new neurons)

Question 15

What is the astrocytes regulation role in the nervous system?

Answer 15

1. regulate the balance of excitatory and inhibitory action potentials by converting the neurotransmitter glutamate to glutamine
2. control the concentration of neurotransmitters, potassium ions (K+), and the calcium (Ca2+)
3. metabolize glucose into lactic acid and lactate to provide energy for neurons

Question 16

What is myelin?

Answer 16

a substance that supports the conductivity of signals on the nervous system

Question 17

How does myelin support the conductivity of signals on the NS?

Answer 17

it does this by maintaining the membrane potential in specific segments of the axon
- saxons can either be myelinated or unmyelinated, and the diameter of the axon is what differentiates them

Question 18

What is nodes of randvier?

Answer 18

the unmyelinated portions of the axon that play a role in inducing changes in the membrane potential

Question 19

In the peripheral nervous system, myelination is carried out by what?

Answer 19

schwann cells

Question 20

Myelination in the PNS by Schwann cells:

Answer 20

1. Neurilemma: layer of schwann cells that covers both myelinated and unmyelinated axons in the PNS
2. myelin sheath: an insulating layer, that’s formed by multiple layers of the Schwann cell plasma membrane
   - multiple schwann cells work together to cover or “envelop” different segments of the axon

Question 21

In the central nervous system, myelination is carried out by what?

Answer 21

carried out by oligodendrocytes cells (oligodendrocytes form myelin sheath)

Question 22

Myelination in the CNS by Oligodendrocytes cells:

Answer 22

1. myelin sheath: an insulating layer made up of multiple layers of their plasma membrane
2. one oligodendrocytes can myelinate multiple axons, unlike in the peripheral nervous system where each schwann cell myelinates a single axon

Question 23

What is gray matter?

Answer 23

in CNS, unmyelinated soma and dendrites make up the gray matter

Question 24

What is white matter?

Answer 24

myelinated axons form the white matter

Question 25

What is transmembrane potentials?

Answer 25

refer to the difference in the concentration of charged molecules across a membrane

Question 26

What is the resting membrane potential?

Answer 26

typically around -70mV, indicating a negative charge inside the cell compared to the outside

Question 27

What does the Voltage determine?

Answer 27

determines the magnitude of this difference across the membrane

Question 28

What are ways the membrane permeability can affect the membrane potential?

Answer 28

1. Depolarization: there is a surge of positive ions, which can lead to a change in the membrane potential 2. Repolarization: occurs when positive ions are released, bringing the membrane potential back to its resting state (negative) 3. Hyperpolarization: involves a surge of negative ions, further increasing the difference in charge across the membrane

Question 29

What is membrane permeability?

Answer 29

- How easily substances, such as ions, can pass through the cell membrane - they send signals by changing the voltage across their cell membranes

Question 30

How is membrane permeability achieved?

Answer 30

through the regulation of the influx (entry) and efflux (exit) of sodium ions (Na+) and potassium ions (K+) through specialized channels called voltage-gated ion channels

Question 31

What are transmembrane potentials?

Answer 31

are all about the voltage across a neuron's cell membrane

Question 32

What are the different kinds of transmembrane potentials?

Answer 32

1. Depolarization: this is when sodium ions (Na+) rush into the neuron, making the inside less negative and closer to zero millivolts (mV). the cell is getting ready to fire off a signal. 2. Overshoot: if the Na+ keeps coming in, the inside of the cell gets even more positive, going past zero mV 3. Repolarization: now, potassium ions (K+) start to leave the cell, which makes the inside less positive and moves the voltage back down towards the resting state of around -70mV 4. Hyperpolarization: sometimes, too much K+ leaves the cell, making the inside even more negative than the resting potential of -70mV. Its like the cell is overshooting on its way back to rest

Question 33

What's the first propagation of action potentials?

Answer 33

1. resting membrane potential: this is the initial state of the cell membrane, where the inside is negatively charged compared to the outside

Question 34

What's the second propagation of action potentials?

Answer 34

2. when an inital signal reaches the membrane, it causes depolarization, which means the inside of the cell becomes less negative and more positive

Question 35

What's the third propagation of action potentials?

Answer 35

3. as a result of depolarization, voltage-gates sodium (Na+) channels open first, allowing sodium ions to enter the cell. the further contributions to depolarization and helps propagate the action potential along the cell membrane

Question 36

What's the fourth propagation of action potentials?

Answer 36

4. after the sodium channels open and sodium ions enter the cell, the next step is the opening of voltage-gated potassium (K+) channels. this allows potassium ions to leave the cell, leading to repolarization

Question 37

What's the fifth propagation of action potentials?

Answer 37

5. as potassium ions leave the cell, the inside becomes more negative (less positive) and moves closer to the resting membrane potential (RMP) of around -70mV

Question 38

What's the sixth propagation of action potentials?

Answer 38

6. this brings the cell back to its original state, completing the action potential

Question 39

What's the seventh propagation of action potentials?

Answer 39

7. when an action potential occurs in one section of a neuron, the sodium ions (Na+) from that region will diffuse to the next region and start an action potential there. this allows the action potential to propagate along the entire length of the neuron

Question 40

What's the eighth propagation of action potentials?

Answer 40

8. the concept of "all-or-none" means that if the axon hillock, which is the initial part of the neuron, reaches a threshold of -55mV, the action potential will always spread down the entire axon to the terminal