Chapter 5

Question 1

what is a receptor potential?

Answer 1

local change in membrane potential that resembles the EPSP

Question 2

what is sensory transduction?

Answer 2

conversion of environmental stimuli into action potentials that are transmitted to the brain

Question 3

why are sensory information separate and distinct?

Answer 3

AP for each sense are carried on separate nerve tracts
- labeled lines: brain recognizes senses as distinct because their AP travel along separate nerve tracts

Question 4

what are skin sensations?

Answer 4

pressure, vibration, tickle, pins & needles, smoothness/ wetness all form touch

Question 5

what is a skin receptor that is an example of sensory transduction?

Answer 5

Pacinian corpuscle -> sense texture
- stimuli stretching its membrane -> opens Na+ channels -> creates graded generator potential -> if potential exceeds threshold, fires AP

Question 6

what are the different receptors in the skin?

Answer 6

Pacinian corpuscle: texture sensitivity
Meissner’s corpuscles: touch (changes)
Merkel’s discs: touch (edges)
Ruffini corpuscles: skin stretch
Free nerve endings: pain, heat, and cold

Question 7

how is intensity of a stimulus measured?

Answer 7

1. number and frequency of AP
2. number of activated sensory receptors

Question 8

what are the three key organizational principles that help sensory neurons tell the brain the location of a stimulus?

Answer 8

1. labeled lines
2. somatosensory map (body surface divided into discrete bands)
3. receptive fields (area within which the presence of a stimulus will alter a sensory neuron firing rate)

Question 9

what is sensory adaptation?

Answer 9

progressive decrease in receptor response to sustained stimulation
- avoid overload and remain vigilant for critical events

Question 10

how does sensory adaptation occur?

Answer 10

phasic receptors display adaptation (most of touch receptors) while tonic receptors show little or no adaptation (pain receptors)

Question 11

what are limited senses?

Answer 11

the sensory organs and pathways convey only limited (or distorted) information to brain
- brain receives highly filtered representation of external world
- stimuli critical for survival are strongly emphasized at expense of less important stimuli

Question 12

how can sensory information be suppressed?

Answer 12

1. removing the stimulus
2. central modulation of sensory information (brain actively suppresses some sensory inputs and amplifies others)
   - reciprocal neural connections descend from brain to synapse on lower sensory levels where they can inhibit activity in ascending sensory axons

Question 13

how does the thalamus control sensory information?

Answer 13

information about each sensory modality sent to separate division of thalamus
- cortex directs thalamus to emphasize some sensory information and suppress other information

Question 14

what is the difference between primary sensory cortex and non primary sensory cortex?

Answer 14

primary sensory cortex (one exists for each modality)
non primary sensory cortex (receives direct projections from primary sensory cortex area for that modality)

Question 15

what are association areas of the brain?

Answer 15

association areas in the brain process inputs from different modalities allowing information from different modalities to interact
- polymodal neurons process input from different sensory neurons

Question 16

what are the benefits of pain?

Answer 16

1. withdraw from its source
2. engage in recuperative actions
3. warn others and elicit care from others

Question 17

how do nociceptors activate?

Answer 17

peripheral receptors on free nerve endings that respond to painful stimuli
- when tissues injured, affected cells release chemicals (serotonin, histamine, and various enzymes and peptides- substance P) that activate nociceptors

Question 18

how does pain get transmitted to the brain?

Answer 18

1. damaged or injured cells release substance that excite free nerve endings that function as pain receptors or nociceptors
2. produce action potential that send signals to spinal cord
3. pain fibers release glutamate and substance P to signal brain about pain

Question 19

what is substance P?

Answer 19

peptide transmitter involved in pain transmission
- promotes inflammation around injured tissue

Question 20

how do you activate local pain response?

Answer 20

pain information is also transmitted to local blood vessels and mast cells
- engage in mechanism that helps heal damaged tissue and prevent further damage
1. blood vessels activated by substance P direct more blood to damaged cells
2. mast cels also activated by substance P release chemicals that produce inflammation response

Question 21

what is the peripheral mechanism of pain?

Answer 21

1. damaged or injured cells release chemicals that excite free nerve ending that function as pain receptors or nociceptors
2. painful information then transmitted to spinal cord as well as blood vessels and mast cells
3. blood vessels activated by substance P direct more blood to damaged cells
4. mast cells activated by substance P release chemicals produce inflammatory response

Question 22

what are the two types of fibers that transmit pain to CNS from spinal cord?

Answer 22

1. A delta fibers: large myelinated axons that register pain quickly (allows for quick responses that prevent further damage)
2. C fibers: small unmyelinated axons that conduct more slowly, producing lasting pain

Question 23

how do the different fibers detect painful temperature changes?

Answer 23

A delta fibers detect very high temperatures via TRPM3 receptors that need a quick response -> does not respond to capsaicin
C fibers detect via TRPV1 receptors -> bind to capsaicin

Question 24

what is the anterolateral system?

Answer 24

transmits the sensations of pain and temperature to brain via A delta and C fibers
- projection distinct from somatosensory system -> glutamate and substance P released to boost pain signals and remodel neurons

Question 25

how is pain interpreted in CNS?

Answer 25

pain information is modulated by periaqueductal gray area -> pain information then sent to many different thalamic and cortical regions -> most conscious feelings of pain associated with cingulate cortex

Question 26

how does the somatosensory cortex relate to pain perception?

Answer 26

pain information transmitted from thalamus to somatosensory cortex -> brain activity in somatosensory cortex correlates to how much discomfort each person report - information about painful stimulus transmitted to cingulate cortex and other

Question 27

what does the cingulate cortex do?

Answer 27

activity in the cingulate cortex also correlates to how much discomfort each person reports - different subregions in cingulate cortex seems to mediate emotional pain vs. sensory aspects of pain - become active when we empathize with a loved one experiencing pain

Question 28

what is neuropathic pain?

Answer 28

pain that persists long after the injury that started it has healed - ex: phantom limb pain

Question 29

what are the three ways to reduce pain?

Answer 29

pharmacological, psychogenic, and stimulation - all produce analgesia (absence of or reduction of pain)

Question 30

what is the problem with chronic pain?

Answer 30

prefrontal cortex shrinks faster than normal

Question 31

what is the hierarchy of movement control?

Answer 31

1. primary and non primary motor cortex create motor plans 2. basal ganglia and cerebellum provide adjustments to motor plans 3. brainstem and spinal cord send motor commands to body

Question 32

what are antagonist vs synergists?

Answer 32

antagonists: when one muscle group contracts, it stretches the other group (biceps and triceps) synergists: muscles that act together to move a limb (triceps)

Question 33

how does the CNS monitor rapid coordinated movements?

Answer 33

1. state of muscle (are they contracted or lengthened) 2. the positions of the limbs (where limbs are located in space without looking) - accomplishes this via specialized receptors called proprioceptors (proprioception is collection of information about body movements and positions)

Question 34

what are the two kinds of proprioceptors?

Answer 34

1. muscle spindle (muscle receptor that lies parallel to muscle and signals to CNS when muscle is lengthened or stretched 2. Golgi tendon organs (type of receptor found within tendons that send impulses to CNS when muscle contracts or tightens)

Question 35

what are the steps for a stretch reflex?

Answer 35

1. weight dropped into hand stretches biceps muscles 2. stretch excites muscle spindles -> send AP to spinal cord (sensory neuron) 3. stretch signal from biceps activates motor nerves to stimulate biceps motor neurons -> contraction 4. stretch signal from bicep stimulates interneurons that inhibit motor nerves to antagonistic triceps motor neurons -> triceps to relax - reflex generates compensatory movement that bring back to intended position

Question 36

what are the two pathways that the brain controls body muscles?

Answer 36

1. pyramidal motor system (corticospinal) -> include neurons within cerebral cortex and their axons that form pyramidal tract 2. extrapyramidal motor system -> include basal ganglia, cerebellum, and some closely related brainstem structures

Question 37

what is the pyramidal motor system?

Answer 37

primary and non primary motor cortex create motor plans that are sent to body via spinal cord to execute movement - neurons within primary form pyramidal motor system -> axons pass through pyramid of medulla

Question 38

what is an unique fact about M1?

Answer 38

M1 cells change firing rate according to direction of movement

Question 39

what are the two parts of the non-primary motor cortex?

Answer 39

two main regions: 1. supplementary motor area (SMA) 2. premotor cortex - located in frontal lobe and are implicated in planning and initiation of voluntary motor movements

Question 40

what is the SMA important for?

Answer 40

initiation of preplanned movement sequences - generates readiness potential which occurs before conscious awareness that a movement will be made - receives input from basal ganglia and modulates activity of primary motor cortex

Question 41

what does the premotor cortex do?

Answer 41

involved in selection of appropriate motor plans for voluntary movements

Question 42

what are mirror neurons?

Answer 42

subarea of premotor cortex that fire when performing an action and watching another person make that same action - important in understanding of other individuals' actions

Question 43

where are the parietal mirror neurons?

Answer 43

inferior parietal lobule, anterior intraparietal sulcus (aIPS), and ventral premotor cortex make up primary mirror neuron circuit - inferior parietal lobule (reaching behavior controlled by vision -> Doral stream of visual association cortex contributes spatial information to parietal reaching region) - anterior intraparietal sulcus (involved in controlling hand and finger movements involved in grasping objects)

Question 44

what does the basal ganglia do?

Answer 44

1. inhibits unwanted movements 2. facilitates initiation of desired movements - output is tonically inhibitory -> always preventing movement - movement inhibition and facilitation achieved by direct, indirect, and hyperdirect pathways

Question 45

what are the movement disorders of basal ganglia?

Answer 45

- parkinson's disease (caused by progressive loss of dopaminergic cells in substantia nigra that project to basal ganglia that results in slowed movements, tremors, rigid posture, and reduced facial) - Huntington's disease (progressive damage to basal ganglia that results in excessive movement)

Question 46

what does the cerebellum do?

Answer 46

receives input from sensory sources - key for rapid motor adaption - helps fine-tune skilled movements - especially the kinds or rapid, repeated movements that become automatic

Question 47

what are symptoms of damage to cerebellum?

Answer 47

1. abnormal gait and posture especially ataxia (loss of coordination) of the legs 2. decomposition of movements describes gestures that are broken into segments instead of executed smoothly