BIO Ch. 4 Nervous System

Question 1

What is the role of a neuron?

Answer 1

transmit electrical impulses to chemical signals

Question 2

What is contained in the soma?

Answer 2

the nucleus, ribosomes, and the ER

Question 3

What is the role of the dendrites?

Answer 3

receives incoming messages from other cells

Question 4

What is the role of the axon hillock?

Answer 4

integrate incoming signals, and initiate an action potential if the signal is excitatory

Question 5

What is the diff between a bundle of nerves in the PNS vs. the CNS?

Answer 5

neurons bundle together in the PNS to form a nerve which may be sensory, motor, or mixed, whereas in the CNS, nerves bundle together to form tracts that only carry one type of information

Question 6

What is the function of astrocytes?

Answer 6

nourish neurons and form the blood-brain barrier, which controls the transmission of solutes from the bloodstream into nervous tissue

Question 7

What is the function of ependymal cells?

Answer 7

they line the ventricles of the brain and produce cerebrospinal fluid which physically supports the brain and serves as a shock absorber

Question 8

What is the function of Oligodendrocytes?

Answer 8

produce myelin around axons in the CNS

Question 9

What is the function of microglia?

Answer 9

phagocytic cells that ingest and break down water products and Pathogens in the CNLS

Question 10

What is the function of Schwann cells?

Answer 10

produce myelin around axons in the PNS

Question 11

WHAT IS THE RESISTING MEMBRANE potential?

Answer 11

-70 mV

Question 12

What is the role of K+ leak channels?

Answer 12

a transmembrane channel that slowly leaks potassium facilitating the outward movement of potassium out of the cell

Question 13

What is the role of Na+ leak channels?

Answer 13

a transmembrane channel that slowly leaks sodium facilitating the outward movement of sodium out of the cell

Question 14

What is the role of Na+/K+ ATPase?

Answer 14

it pumps 2 potassium ions into the cell and 3 sodium ions out of the cells to maintain their respective gradients, maintaining the resting membrane potential

Question 15

What does an excitatory input cause?

Answer 15

it causes the cell to depolarize to the threshold voltage and voltage-gated sodium channels open. This raises the membrane potential from its resting potential thus making the neuron more likely to fire an action potential

Question 16

What does an inhibitory input cause?

Answer 16

it causes hyperpolarization, lowering the membrane potential from its resting potential and thus makes the neurons less likely to fire an action potential

Question 17

What is the diff b/w temporal and spatial summation?

Answer 17

temporal summation refers to the addition of multiple signals near each other in time, while spatial summation refers to the addition of multiple signals near each other in space

Question 18

What drives sodium into the cell and potassium out of the cell?

Answer 18

the strong electrochemical gradient

Question 19

What is the diff b/w the 2 refractory periods (hyperpolarized)?

Answer 19

During the absolute refractory period, no amount of stimulation can cause another action potential to occur. During the relative refractory period, there must be greater than normal stimulation to cause an action potential because the membrane is starting from a potential that is more negative than its resting value

Question 20

Describe action potential in a neuron.

Answer 20

a neuron starts at resting potential, around - 70 mV. At the resting potential, potassium is high inside the cell, while sodium is high outside the cell. Once the cell reaches the threshold, sodium channels open, and sodium floods inside the cell, depolarizing the cell. Then sodium channels are inactivated and the potassium channels open, causing potassium to flow out of the cell, ringing the potential to the negative range, repolarizing the cell, and overshooting the resting potential (hyperpolarization). The Na+/k+ ATPase then wors to restore the resting potential

Question 21

What determines the speed of the action potential?

Answer 21

it depends on the length and the cross-sectional area. An increased length of the axon results in higher resistance and slower conduction. greater cross-sectional areas allow for faster propagation due to decreased resistance

Question 22

What is the diff b/w chemical and electrical transmission?

Answer 22

within neurons, electricity is used to pass signals down the length of the axon. between neurons, chemicals/neurotransmitters are used to pass signals to subsequent neurons, or glands and muscles

Question 23

What are the 3 mechanisms by which neurotransmitters are removed from the synaptic cleft?

Answer 23

1. acetylcholine is broken down by acetylcholinesterase
2. neurotransmitters are brought back into the presynaptic neurons using reuptake carriers such as serotonin, dopamine, and norepinephrine
3. they can be diffused out of the synaptic cleft such as nitric oxide signaling molecule

Question 24

Describe action potential in neurotransmitters

Answer 24

neurotransmitters are stored in membrane-bound vesicles. when an action potential reaches the nerve terminal, voltage-gated calcium channels open, allowing calcium to flow into the cell. This increases the intracellular concentration of calcium, triggering the fusion of the membrane-bound vesicles with the cell membrane at the synapse, causing exocytosis of the neurotransmitters into the synaptic cleft. once released into the synapse, the neurotransmitter molecules diffuse across the cleft and bind to receptors (ligand-gated ion channels of G protein-coupled receptors) on the post-synaptic membrane, allowing the message to be passed from one neuron to the next

Question 25

What is the diff b/w afferent and efferent neurons?

Answer 25

afferent neurons transmit sensory information from receptors to the spinal cord and brain. efferent neurons transmit moto information from the brain in the spinal cord to the muscles and glands

Question 26

What is the diff b/w gray and white matter?

Answer 26

white matter consists of axons encased in a myelin sheath. gray matter consists of unmyelinated cell bodies and dendrites

Question 27

What is the diff in the placement of gray and white matter b/w the brain and the spinal cord?

Answer 27

in the brain, white matter lies deeper than gray matter, while in the spinal cord, white matter lies on the outside of the cord, and gray matter is deep within it.

Question 28

Where are the sensory neurons found in the spinal cord?

Answer 28

the sensory neurons bring information from the periphery and enter through cell bodies in the dorsal root ganglia

Question 29

Where are the motor neurons found in the spinal cord?

Answer 29

motor neurons exit the spinal cord ventrally into the ventral root ganglia

Question 30

What are the nerves of the PNS?

Answer 30

31 spinal nerves, and 10 cranial nerves excluding the optic and olfactory nerves

Question 31

What is the role of the ANS?

Answer 31

Automatic functions such as regulating heartbeat, respiration, digestion, temperature, and glandular secretion

Question 32

What is the role of the PNS?

Answer 32

It is associated with resting and sleeping states, and acts to reduce heart rate and constrict the bronchi, increases parastalsis and exocrine secretion

Question 33

What is the neurotransmitter responsible for the PNS response?

Answer 33

acetylcholine is released in the pre and postganglionic neurons

Question 34

Which nerve is responsible for the parasympathetic innervation of the thoracic and abdominal cavities?

Answer 34

vagus nerve/cranial nere X

Question 35

What is the neurotransmitter responsible for the SNS response?

Answer 35

In the preganglionic neurons, acetylcholine is released, while the postganglionic neurons release norepinephrine

Question 36

What are the 2 types of reflex arcs?

Answer 36

mono and polysynaptic

Question 37

What is an example of a monosynaptic reflex arc?

Answer 37

the knee-jerk reflex

Question 38

What is an example of a polysynaptic reflex arc?

Answer 38

withdrawal reflex

Question 39

What is the diff b/w electrical and chemical communication?

Answer 39

Electric communication occurs via ION exchange and the generation of membrane potential down the length of the axon. Chemical communication occurs via NEUROTRANSMITTERS released from the presynaptic cells and the binding of these neurotransmitters to the postsynaptic cell

Question 40

Where are neurotransmitters released?

Answer 40

in the nerve terminal/synaptic bouton

Question 41

What are the differences b/w the cell bodies of neurons in the PNS and CNS?

Answer 41

Cell bodies of neurons of the same type within a nerve cluster in the ganglia in the PNS. cell bodies of neurons within a tract cluster in nuclei in the CNS

Question 42

What is the diff b/w mono and polysynaptic reflect arcs?

Answer 42

mono - a sensory (afferent, presynaptic) neuron fires directly onto a motor (efferent, postsynaptic) neuron. in polysynaptic reflex, a sensory neuron may fire directly onto motorneurons, or through interneurons which then directly into the motor neuron

Question 43

What is saltatory conduction?

Answer 43

when action potential jumps from node to node

Question 44

What causes hyperpolarization?

Answer 44

it is caused by the excess potassium exiting the neuron

Question 45

How does anticonvulsant drugs work to treat seizures??

Answer 45

By increasing the threshold for action potential generation, making it more difficult for neurons to reach the level of depolarization required to initiate an action potential. By raising the threshold, these drugs can prevent excessive abnormal neuronal firing that leads to seizures