L10: Organization of the Nervous System / Spinal Reflex Connections

Question 1

division of the PNS that carries info from the sensory receptors in the skin, skeletal muscles and joints to the CNS; composed of sensory neurons

Answer 1

Afferent

Question 2

division of the PNS that transmits impuses from the CNS to the effector organs

Answer 2

efferent

Question 3

what are the two divisions of the efferent NS

Answer 3

Somatic NS: fibers of motor neurons that supply skeletal muscles
Autonomic NS: fibers that innervate smooth muscle,, cardiac and glands

Question 4

excitable cells that transmit electrical impulses, the functional units of the NS

Answer 4

Neurons

Question 5

cells that communicate w/ and support the neurons

Answer 5

neuroglia

Question 6

soma

Answer 6

cell body
contains nucleus and most organelles

Question 7

what does it mean for neurons to be amitotic

Answer 7

• they don’t divide to create more neurons
• they lack centrioles - an organelle needed for cell division

Question 8

outgrowths of neuronal processes from the soma

Answer 8

dendrites

Question 9

sites that receive inputs from other neurons; are the site of synapses

Answer 9

dendritic spines

Question 10

the axon is the primary _________ output

Answer 10

neuronal

Question 11

transport substances within the axon

Answer 11

microtubules

Question 12

synaptic terminals release ?

Answer 12

NTs

Question 13

more neurons or neuroglia?

Answer 13

neuroglia, 10x more than neurons

Question 14

do neuroglia initiate or conduct APs?

Answer 14

no

Question 15

5 major classes of neuroglia

Answer 15

CNS glia:
- astrocytes
- microglia
- ependymal cells
- oligodendrocytes
PNS glia:
- Schwann cells

Question 16

neurons have a well developed ______ and _______ since they are major biosynthetic centers for neuropeptides

Answer 16

Golgi apparatus & Rough ER

Question 17

most abundant of the neuroglia

Answer 17

astrocytes

Question 18

neuroglia that are the ‘immune system’ of the NS

Answer 18

microglia

Question 19

neuroglial cells that are capable of dividing and therefore are the source of all new neurons

Answer 19

Ependymal cells

Question 20

Both the ______ & ________ glial cells produce a protective sheath over the axons, allowing for increased speed of transmission of APs (myelination)

Answer 20

Oligodendrocytes (CNS) and Schwann cells (PNS)

Question 21

what glial cells make up the white matter

Answer 21

Oligodendrocytes & schwann cells

Question 22

3 fiber types that occur in the PNS

Answer 22

A, B, C
characterized based on how theri axons are myelinated (A being the ‘thickest’, C being the ‘thinnest’

Question 23

Aα fibers are the ______, Aδ are the _________ in diameter

Answer 23

alpha - largest in diameter (and fastest)
delta - smallest in diameter (slower)

Question 24

Aα fibers carry what information

Answer 24

muscle spindle and golgi tendon info

Question 25

Aβ fibers carry what info

Answer 25

musle spindle, touch and proprioception *mechanoreceptors of the skin*

Question 26

Aδ carry what info

Answer 26

pain and temperature - mechanical nociceptors

Question 27

C fibers are small and _______

Answer 27

non myelinated = slow

Question 28

C fibers cary info on..?

Answer 28

pain

Question 29

what things does each spinal nerve have?

Answer 29

* dorsal root (dorsal horn) * ventral root (ventral horn) * relay circuits * ganglia

Question 30

where do upper motor neurons originate | AKA Pyramidal tract

Answer 30

primary motor cortex

Question 31

what do UMNs control

Answer 31

skeletal muscle tone and consious skilled movements

Question 32

what are corticospinal nerves most important for (type of movement)

Answer 32

intentional movements

Question 33

where do **lateral corticospinal** nerves cross

Answer 33

at the medulla

Question 34

where **do ventral corticospinal** nerves cross?

Answer 34

at the level of termination in the spinal cord

Question 35

UMNs synapse at _____ in the spinal cord

Answer 35

Lower motor neurons

Question 36

axons of the lower motor neurons exit at the _____ and go on to the PNS

Answer 36

Ventral horns

Question 37

T/F: contralateral control of the skeletal muscle movements occurs in both the lateral and ventral corticospinal tracts

Answer 37

T

Question 38

both the lateral and ventral corticospinal tracts are involved in the _______ control of skeletal muscles

Answer 38

voluntary

Question 39

what is canine degenerative myelopathy

Answer 39

* damage to the spinal cord that causes the pathways b/w body and brain to get interrupted * progressive demyelination of the spinal cord * spastic paresis * exaggerated reflexes

Question 40

Canine degenerative myelopathy is characterized by _____motor neuron paralysis localized to the T3-L3 spinal segments

Answer 40

upper motor neuron

Question 41

when diagnosing DM, what is important to rule out

Answer 41

**spinal compression** which is when large diameter fibers lose function before small diameter fibers

Question 42

what is feline diabetic neuropathy

Answer 42

demyelination of distal axons associated w/ diabetes mellitus * plantigrade and palmigrade stance * can progress to tetraparesis where all 4 limbs are affected

Question 43

why is feline diabetic neuropathy also associated w/ sensory nerve disfunction

Answer 43

b/c sensory NS is part of the peripheral part of the body

Question 44

what are the 2 types of reflexes

Answer 44

* simple/basic: built in, unlearned * acquired/conditioned: result of practice or learning

Question 45

what are the 5 components of the neural pathway involved in reflex activity

Answer 45

* receptor * afferent pathway * integrating center * efferent pathway * effector

Question 46

what are golgi tendon organs

Answer 46

* proprioceptors (detect position of the body) * measure the tension in muscle

Question 47

what are muscle spindles

Answer 47

* proprioceptors * located within a muscle tissue parallel to muscle fibers * spindle consists of contractile ends and a non-contractile middle portion with sensory innervation

Question 48

the contractile ends of muscle spindles are innervated by what kind of motor neurons

Answer 48

γ (gamma)

Question 49

what is the non-contractile middle portion of a muscle spindle innervated by

Answer 49

type 1a and II afferent sensory fibers

Question 50

α-motor neurons innervate the ________skeletal muscle fibers

Answer 50

extrafusal

Question 51

what happens to cause a muscle to contract

Answer 51

motor impulse (afferent input) comes down spinal cord, excited extrafusal fibers another impulse causes intrafusal muscle spindle fibers to contract spindles are shortened but remain sensitive to stretch at all muscle lengths

Question 52

**group 1A afferent** sensory receptors innervate both **nuclear bag and nuclear chain fibers **and detect ?

Answer 52

the velocity of length change

Question 53

**Group 2 afferent** sensory receptors innervate **nuclear chain fibers**and detect?

Answer 53

the length of the muscle fiber

Question 54

when a muscle is stretched, both group ___ and ___ afferents are activated

Answer 54

1A and 2

Question 55

motor innervation includes _____ γ motorneurons that innervate nuclear____fibers and _______ γ motorneurons that inenrvate nuclear _____ fibers

Answer 55

static - chain dynamic - bag

Question 56

A-motor neurons activates ______fibers causing them to shorter at the same time, to keep tension in spindles constant, the γ motor neurons activate the _______ fibers, causing them to shorter

Answer 56

extrafusal intrafusal

Question 57

the monosynaptic stretch reflex (aka myotactic) is important in maintaining ______ and muscle tone

Answer 57

posture

Question 58

during the monosynaptic stretch reflex, the stretch is measured by?

Answer 58

muscle spindles (intrafusals) - length detectors

Question 59

activated muscle spindles activate the ____neuron of a stretched muscle

Answer 59

motor

Question 60

profective reflex in response to the stretch of muscles

Answer 60

Polysynaptic stretch reflex

Question 61

the polysnyaptic stretch reflex is composed of two or more synapses that allow for ______ innervation

Answer 61

reciprocal

Question 62

during the polysynaptic stretch reflex, extensors are activated while the opposing flexor muscle is ______

Answer 62

inhibited

Question 63

are polysynaptic reflexes faster or slower than monosynaptic reflexes

Answer 63

slower

Question 64

what reflex involves nociceptors (free nerve endings)

Answer 64

* flexor withdrawal reflex * ex: pulling hand away from flame * limb withdrawal occurs by the simultaneous activation and relaxation of opposing muscles

Question 65

what reflex allows weight to be shifted to the uninjured limb so you don't fall

Answer 65

the flexor withdrawal/crossed extensor reflex

Question 66

pathway in the spinal column responsible for touch, pressure vibration, 2 point discrimination and proprioception

Answer 66

dorsal lemniscus columns

Question 67

ascending pathway responsible for touch

Answer 67

ventral spinothalamic (crossed)

Question 68

ascending pathway responsible for pain and temp

Answer 68

lateral spinothalamic (crossed)

Question 69

what are the 3 ascending afferent pathways?

Answer 69

* lateral lemniscus columns * lateral spinothalamic * ventral spinothalamic

Question 70

when performing a noxious stimulus to test the crossed extensor reflex, what reaction would you expect to see if a patient had an upper motor neuron lesion?

Answer 70

exaggerated reflex due to a lack of control of the relex by UMNs and or a lack of awareness of the stimulus

Question 71

a segmental reflex transverses ____ or _____ segments or brain divisions

Answer 71

one or few

Question 72

an intersegmental reflex transverses several segments of the _______ or several brain divisons

Answer 72

spinal cord

Question 73

a long-loop intersegmental reflex transverses many segments of the ______ and or brain divisions; enters and exits the CNS at the same location

Answer 73

spinal cord

Question 74

proprioceptors carry info on ______ while nociceptors carry info on _______

Answer 74

movement pain

Question 75

free nerve endings in joint capsules and in the skin are what type of receptors

Answer 75

nociceptors (pain)

Question 76

what root/horn (dorsal or ventral) carries **afferent**

Answer 76

dorsal

Question 77

what root/horn (dorsal or ventral) carries **efferent**

Answer 77

Ventral

Question 78

why are C fibers the slowest

Answer 78

not myelinated

Question 79

a bunch of intrafusal muscles fibers is a ...

Answer 79

muscle spindle