lecture 5 behavior from the perspective of bioelectricity

Question 1

what is a reflex

Answer 1

a reaction in response to a stimulus not requiring conscious awareness

Question 2

what to reflex exams reveal

Answer 2

general nervous system disorders and problems with particular parts of the nervous system

Question 3

what is the latency between time of stimulus and reaction in the paterllar tendon reflex

Answer 3

20 milliseconds

Question 4

is reflex latency faster or slower in tall people

Answer 4

slower; the distance the signal travels is longer

Question 5

steps in myotatic reflex

Answer 5

1) stimulus 2) transduction 3) frequency encoding 4) sensory motor synapse 5) motor neuron action potential 6) muscle fiber activation

Question 6

what is the stimulus step in the myotatic reflex

Answer 6

tapping patellar tendon causes quadricep muscle to stretch

Question 7

what is the transduction step

Answer 7

converting mechanical stimulus into electrical signal

Question 8

what is the transduction apparatus

Answer 8

a muscle spindle whos fibers are wrapped by a sensory axon called the 1a axon

Question 9

what does the stretching of the spindle muscle fibers to

Answer 9

causes stretching of sensory axons, opening up na+ channels

Question 10

what is a receptor potential

Answer 10

depolarization of 1a axon (na+ channels opening) in response to stretch of muscle fibers

Question 11

what is frequency encoding

Answer 11

converting receptor potential amplitude into the frequency of action potentials

Question 12

what is an action potential

Answer 12

large, rapid, stereotyped change in membrane potential

Question 13

when is the only time an action potential can be elicited

Answer 13

when a receptor potential brings the membrane potential above a threshold value

Question 14

what is the same and different across all action potentials

Answer 14

their size and shape is invariant but their frequency can vary widely

Question 15

the stronger the receptor potential… (the more depolarization due to strong and long stimulus)

Answer 15

the greater the frequency of the action potentials (amount per second)

Question 16

where does receptor potential occur

Answer 16

locally in 1a axon

Question 17

difference between receptor and action potentials

Answer 17

action potentials, once started (reach threshold), dont stop but receptor potentials can die out

Question 18

where do the action potentials with the 1a axon start and end

Answer 18

begin in 1a axon and propagate via peripheral nerve to dorsal root ganglion, then from dsg to spinal cord

Question 19

where is the dorsal root ganglion and what is its function

Answer 19

cluster of neurons in dorsal root of spinal nerve, carries sensory information to spinal cord and enters posterior of spinal cord

Question 20

what happens with sensory motor synapses after frequency encoding

Answer 20

action potential from 1a axon drives the axon terminal to release neurotransmitters at synaptic junction

Question 21

what do neurotransmitters do once released (for myotatic reflex)

Answer 21

bind to receptors on motor neuron dendrite causing synaptic potential in motor neuron

Question 22

what is similar between synaptic potential and receptor potential

Answer 22

decrease in amplitude (and power) with distance

Question 23

what causes motor neuron action potential

Answer 23

once synaptic potentials build on top of each other and pass the threshold to trigger action potential

Question 24

what is an epsp and what does it do

Answer 24

excitatory post synaptic potential, allows sequential synaptic potentials to piggyback on top of each other and cross threshold to elicit action potential

Question 25

what happens after motor neuron action potential is triggered

Answer 25

muscle fiber activates (via neuromuscular junction, synapse between neuron and muscle) motor signal is sent through motor neuron axon terminal to muscle fiber

Question 26

what happens when muscle fiber reaches threshold

Answer 26

triggers action potential that causes muscle fiber to contract which counters stretch induced from stimulus

Question 27

what is strength of muscle contraction related to

Answer 27

number and frequency of motor axons activated

Question 28

what is bells palsy

Answer 28

weakness of muscle supplied by facial nerve

Question 29

where is the soma of the 1a axon

Answer 29

in the dorsal root ganglion

Question 30

Frequency coding

Answer 30

since action potentials are unitary in size and duration, the strength of the signal is determined by the frequency of the action potentials. A stronger signal increases the frequency of action potentials (i.e. number of action potentials per second)

Question 31

Action potential

Answer 31

an actively propagated impulse that conveys information across long distances. Action potentials are considered unitary or “all or none”. Meaning that the size and duration of each action potential remains constant. Details will be covered in later lectures.

Question 32

Graded potential

Answer 32

an electric signal that changes the membrane potential in a continuous manner (oppose to unitary, or “all or none” manner) typically in a small region of a neuron. Graded potentials can differ in size, shape, or duration, depending on the stimulus and response properties of the responding neuron. Graded potentials are commonly found at sensory receptors and synapses

Question 33

Stimulus

Answer 33

an extrinsic or intrinsic signal that causes a response. In sensory systems, the nature of the stimulus is specific to the sensory modality and the type of sensory receptors activated

Question 34

Signal transduction

Answer 34

converting one kind of signal or stimulus into another type (e.g. mechanical stimulus to electrical signal or electrical signal to chemical signal)

Question 35

Signal transduction

Answer 35

converting one kind of signal or stimulus into another type (e.g. mechanical stimulus to electrical signal or electrical signal to chemical signal)

Question 36

Excitatory neuron

Answer 36

a neuron, that when active and fires action potentials, increases the probability that the neurons it connects to via synapses will also fire an action potential.

Question 37

Inhibitory (often an interneuron)

Answer 37

a neuron, that when active (fires action potentials), decreases the probability that the neurons it connects to via synapses will fire an action potential. Many inhibitory neurons do not send their axons very far, making local connections and are referred to as interneurons

Question 38

Motor neuron

Answer 38

type of efferent neuron (a cell that carries information away the brain to the periphery) that synapses onto skeletal muscle fibers

Question 39

Sensory neuron

Answer 39

type of afferent neuron (a cell that carries sensory information toward the brain from the periphery).

Question 40

List the components of behavior

Question 41

Describe the anatomical organization and electrical signaling that give rise to the knee jerk reflex circuit

Question 42

Explain how amplitude coding and frequency coding is used in the myotatic stretch reflex

Question 43

Explain the differences between a local potential and a propagated potential