Physiology of Nervous System

Question 1

What is depolarization. what is it represented by

Answer 1

short positive changes in the membrane potential. represented by action potentials (nerve impulses) are generated in the cell body (axon hillock) and carried down the axon.

Question 2

What are the three overlapping functions of the nervous system

Answer 2

1. Sensory input
2. Integration
3. Motor output

Question 3

What is the sensory input part of the nervous system

Answer 3

uses its sensory receptors to monitor changes occurring both inside and outside the body. the info gathered is called the sensory input

Question 4

What is the integration part of the nervous system

Answer 4

the system processes and interprets sensory input and decides what should be done at each moment

Question 5

What is the motor output part of the nervous system

Answer 5

the nervous system activates effector organs (the muscles and glands) to cause a response called motor output

Question 6

What are the two main types of membrane ion channels

Answer 6

1. Leakage or nongated channels
2. Gated channels

Question 7

What are leakage or nongated channels

Answer 7

membrane ion channels that are always open.

Question 8

What are gated channels

Answer 8

membrane ion channels that open and close the channel in response to specific signals. There are three main types:
1. Chemically gated
2. Voltage gated
3. Mechanically gated

Question 9

What is a chemically gated channel

Answer 9

aka: ligand-gated channel. open when the appropriate chemical binds. (NT bings to membrane protein and opens the channel)

Question 10

What is a voltage-gated channel

Answer 10

open and close in response to changes in the membrane potential. No receptor

Question 11

What are mechanically gated channels

Answer 11

open in response to physical deformation of the receptor (as in sensory receptors for touch and pressure)

Question 12

What are the two things that generating a resting membrane potential depends on

Answer 12

1. differences in K+ and Na+ concentrations inside and outside cells
2. differences in permeability of the plasma membrane to these ions (3 K+ out, 2 Na+ in to maintain RMP)

Question 13

the term depolarization and hyperpolarization describe changes in…

Answer 13

membrane potentials relative to resting membrane potential

Question 14

Changes in membrane potential can produce two types of signals. what are they?

Answer 14

1. graded potentials and 2. action potentials

Question 15

What is depolarization

Answer 15

incoming signals operating over short distances that have variable (graded) strength

Question 16

What is an action potential

Answer 16

long-distance signals of axons that always have the same strength

Question 17

The resting membrane potential is approx ___mV in neurons

Answer 17

-70 (inside negative)

Question 18

What is depolarization? Explain how it works

Answer 18

a decrease in membrane potential.
The inside of the membrane becomes less negative (moves closer to zero) than the resting potential. For instance, a change in resting potential from −70mV to −65mV is a depolarization.

Question 19

What is hyperpolarization? Explain how it works

Answer 19

an increase in membrane potential
The inside of the membrane becomes more negative than the resting potential. A change from −70mV to −75mV is hyperpolarization. Reduces nerve impulses

Question 20

What does depolarization do

Answer 20

Increases the probability of producing nerve impulses

Question 21

What does hyperpolarization do

Answer 21

Decreases the probability of producing nerve impulses

Question 22

Graded potentials are _____-lived, localized changes in membrane potential, usually in _______ or the _______.

Answer 22

short lived, dendrites or cell-body

Question 23

Why are graded potentials called “graded”

Answer 23

because their magnitude varies directly with stimulus strength. The stronger the stimulus, the more the voltage changes and the farther the current flows.

Question 24

APs-voltage gated ion channels are _____, _____-distance signals within a neuron

Answer 24

brief and long-distance

Question 25

Where do action potentials occur

Answer 25

Occur only in muscle cells and axons of neurons (only found in the membranes of excitable tissues)

Question 26

How does the CNS tell the difference between a weak stimulus and a strong one

Answer 26

CNS tells difference between a weak stimulus and a strong one by frequency of impulses (the number of AP received per second) Higher frequency means stronger stimulus

Question 27

Rate of AP propagation depends on 2 factors:

Answer 27

1. Axon diameter Larger-diameter fibers have less resistance to local current flow, so have faster impulse conduction 2. Degree of myelination Two types of conduction depending on presence or absence of myelin

Question 28

What is continuous conduction of an impulse

Answer 28

slow conduction that occurs in nonmyelinated axons

Question 29

What is the saltatory conduction of an impulse

Answer 29

occurs only in myelinated axons and is about 30 times faster

Question 30

What are some conditions that occur when an impulse is saltatory instead of continuous

Answer 30

Myelin sheaths insulate and prevent leakage of charge Voltage-gated Na+ channels are located at myelin sheath gaps APs generated only at gaps Electrical signal appears to jump rapidly from gap to gap

Question 31

What are the three categories of Nerve fibers

Answer 31

Group A, Group B, Group C

Question 32

Describe Group A nerve fibers

Answer 32

Largest diameter Myelinated somatic sensory and motor fibers of skin, skeletal muscles, and joints Transmit at 150 m/s (~300 mph) (FASTEST)

Question 33

Describe group B nerve fibers

Answer 33

Intermediate diameter Lightly myelinated fibers Transmit at 15 m/s (~30 mph)

Question 34

Describe group C nerve fibers

Answer 34

Smallest diameter Unmyelinated Transmit at 1 m/s (~2 mph)

Question 35

B and C groups of nerve fibers include _______ motor and sensory fibers that serve _______

Answer 35

ANS visceral, serve visceral organs

Question 36

what is the presynaptic neuron

Answer 36

The neuron conducting impulses toward the synapse

Question 37

What is the post-synaptic neuron

Answer 37

the neuron transmitting the electrical signal away from the synapse

Question 38

Outside the central nervous system, the postsynaptic cell may be either another_______ or an _______

Answer 38

another neuron or an effector cell (a muscle cell or gland cell)

Question 39

What are the two most common synapses

Answer 39

1. Axodendritic synapses 2. Axosomatic synapses

Question 40

What are axodendritic synapses

Answer 40

Synapses between the axon endings of one neuron and the dendrites of other neurons.

Question 41

What are axosomatic synapses

Answer 41

Synapses between axon endings of one neuron and the cell body (soma) of another neuron.

Question 42

What are Axoaxonal synpases

Answer 42

synapses between axons

Question 43

what are Dendrodendritic synapses

Answer 43

synapses between dendrites

Question 44

What are Somatodendritic synapses

Answer 44

synapses between cell bodies and dendrites

Question 45

What are the two types of synapses

Answer 45

1. Electrical 2. Chemical (neuromuscular junction)

Question 46

Transmission of nerve impulses along an axon is an electrical or chemical event

Answer 46

electrical

Question 47

Explain the 6 steps involved in converting an electrical impulse to a chemical impulse at a synapse

Answer 47

1. Action Potential Arrives at axon terminal 2. Voltage-gated Ca2+channels open and Ca2+enters the axon terminal 3. Ca2+entry causes synaptic vesicles to release neurotransmitter by exocytosis 4. Neurotransmitter diffuses across the synaptic cleft and binds to specific receptors on the postsynaptic membrane. 5. Binding of neurotransmitter opens ion channels, creating graded potentials 6.Neurotransmitter effects are terminated

Question 48

What are the three ways the postsynaptic cleft is cleaned after NT release

Answer 48

1. Reuptake 2. Degradation 3. Diffusion

Question 49

What is reuptake

Answer 49

Reuptake by astrocytes or the presynaptic terminal, where the neurotransmitter is stored or destroyed by enzymes (as with the neurotransmitter norepinephrine)

Question 50

What is degradation of NT

Answer 50

Degradation by enzymes associated with the postsynaptic membrane or present in the synaptic cleft (as with acetylcholine

Question 51

What is diffusion of NT

Answer 51

Diffusion away from the synapse

Question 52

ACh is released by all neurons that stimulate________ and by many neurons of the autonomic nervous system. ACh-releasing neurons are also found in the _____

Answer 52

skeletal muscles. CNS

Question 53

The function of a neurotransmitter is determined by ____________

Answer 53

by the receptor to which it binds.

Question 54

If a IPSP was released, the result of K and Na would be...

Answer 54

Makes postsynaptic membrane more permeable to K+ or Cl– If K+ channels open, it moves out of cell If Cl– channels open, it moves into cell

Question 55

If an EPSP is released, the result of K and Na would be...

Answer 55

allows simultaneous flow of Na+ and K+ in opposite directions Na+ influx greater than K+ efflux,

Question 56

Explain No Summation

Answer 56

When two EPSPs are far apart in time, they do not influence each other. It's like if someone says "fire!" every so often—it doesn't really grab your attention because it's not frequent enough to cause concern.

Question 57

Explain Temporal Summation

Answer 57

When two EPSPs occur close together in time, they can add up (summate), potentially bringing the neuron to the threshold needed to fire an AP. It's like someone shouting "fire!" repeatedly in quick succession—you're more likely to respond immediately.

Question 58

Explain Spatial Summation

Answer 58

This happens when two EPSPs are generated at the same time but come from different locations on the neuron. If the combined depolarizations bring the neuron to threshold, an AP will fire. It’s similar to multiple people shouting "fire!" at the same moment, which gets your attention quickly.

Question 59

Explain Spatial Summation of EPSPs and IPSPs:

Answer 59

If an EPSP and an IPSP occur at the same time, they will counteract each other. This is akin to one person shouting "fire!" while another shouts "don't fire!" at the same time, causing confusion and no clear action.

Question 60

Explain a direct action NT

Answer 60

neurotransmitter binds directly to and opens ion channels Promotes rapid responses by altering membrane potential Examples: ACh and amino acids

Question 61

Explain an indirect action of NT

Answer 61

neurotransmitter acts through intracellular second messengers, usually G protein pathways Broader, longer-lasting effects similar to hormones Biogenic amines, neuropeptides, and dissolved gases

Question 62

What are the two main types of receptors involved in neurotransmission

Answer 62

channel-linked receptors and G protein–coupled receptors.

Question 63

What is the difference between channel-linked receptors and Gprotein receptors

Answer 63

Channel-linked receptors are responsible for fast synaptic transmission. When a neurotransmitter binds to these receptors, they change shape and open a channel directly, allowing specific ions to pass through quickly, which changes the membrane potential. G protein–coupled receptors (GPCRs) oversee slower synaptic responses. They don’t directly open ion channels. Instead, when a neurotransmitter binds to a GPCR, it activates a G protein inside the cell. This G protein can then trigger a series of events

Question 64

Describe the two types of zones within the simple neuronal pool

Answer 64

Discharge Zone: Neurons at the discharge zone are more likely to fire action potentials due to receiving more synapses. Facilitated Zone: Neurons at the facilitated zone receive fewer synapses and are less likely to fire but are "primed" and can be easily activated by additional stimuli.

Question 65

What are two types of neural processing pathways

Answer 65

1. Serial: signals travel along a straight, predetermined path, one neuron activating the next in a sequence. 2. Parallel: the input can travel along multiple pathways simultaneously. This allows different parts of the nervous system to deal with the same information at the same time, promoting complex responses and higher-level functions like memory and learning.

Question 66

What is an example of serial processing pathway

Answer 66

An example is the spinal reflex arc, where a specific stimulus causes a predictable response. Reflex arcs typically include: Receptor: Senses the stimulus. Sensory neuron: Transmits the signal to the CNS. CNS integration center: Processes the signal and forms a response. Motor neuron: Carries the response signal from the CNS. Effector: Acts in response to the signal (e.g., muscle or gland).

Question 67

What are circuits

Answer 67

The patterns of synaptic connections in neuronal pools, called circuits, determine the pool’s functional capabilities.

Question 68

What are the 4 types of circuits

Answer 68

Diverging, Converging, Reverberating, Parallel after-discharge

Question 69

What is a diverging circuit. Give an exam

Answer 69

One input, many outputs. An Amplifying circuit. Ex// a single neurons in the brain can activate 100 or more motor neurons in the spinal cord and thousands of skeletal muscle fibers

Question 70

What is a Converging circuit

Answer 70

Many inputs, one output. A concentrating circuit Ex//Different sensory stimuli can all elicit the same memory

Question 71

What is a reverberating circuit

Answer 71

Signal travels through a chain of neurons, each feeding back to previous neurons. An oscillating circuit that controls rhythmic activity. Ex// involved in breathing, sleep-wake cycle, and repetitive motor activities such as walking

Question 72

What is a parallel after-discharge circuit

Answer 72

signal stimulates neurons arranged in parallel arrays that eventually converge on a single output cell. Impulses reach output cell at different times, causing a burst of impulses called an "after-discharge" Ex// may be involved in exacting mental processes such as mathematical calculations