Neuroanat 6

Front 1

Consider the Following Questions ..

Back 1

Where is the cell body of a sensory neuron with connection to intrafusal muscle fibers in the biceps?
Describe the places in spinal cord this neuron will send collateral branches and terminals.
What does it mean that a receptor is a "transducer" and that it responds best to a "particular stimulus"? Describe some receptors for: a) muscle stretch; b) touch; c) pain.
Describe the somatotopic organization of the postcentral gyrus, and identify which part of the internal capsule contains these thalamic radiations.

Front 2

Because we are animals that can stand, c2 is rather
large and covers

Back 2

covers the back of our head and part of the top

Front 3

Retaining
the somatotopic pattern means

Back 3

means that even when the
bundle of axons enter the cns they still carry the info
they bring from the body

Front 4

Transducers

Back 4

i.e. change
energy form to action potentials.

Front 5

Rapidly adapting receptors

Back 5

hairs +Pacinian and Meissner

Front 6

Slowly adapting receptors

Back 6

Merkel + Ruffini

Front 7

Rapidly adapting receptors are those that upon stimulation

Back 7

they adapt for instance hair receptors if you
touch them you feel the stimulation, but if you leave
your hand in your hair you'll eventually stop feeling that
something is there

Front 8

Other receptors are slow
adapting meaning

Back 8

meaning they continue to respond so these
are good for sensing pressure a sense of maintained
touch..say holding an egg without breaking it.

Front 9

. If the slow
adapting receptors start to not respond adequately

Back 9

the rapid adapting kick in and tell you
to keep pressing the egg

Front 10

there are receptors in
certain spots as opposed to everywhere, so CNS tries to

Back 10

make its best approximation about where certain stimulus is coming from

Front 11

Receptor cells have collaterals that go for instance to more than one merkel cell and the distribution of the merkel cells will define

Back 11

the respond to that stimilus

Front 12

Muscle spindle primary ending fibers
Golgi tendon organs fiber

Back 12

1a
1b

Front 13

Meissner. Merkel, Pacinian fibers

Back 13

ABeta

Front 14

Axons to intrafusal fibers

Back 14

gamma

Front 15

Sharp pain. cold some touch

Back 15

delta (preganglionic autonomic)

Front 16

Slow pain. heat. itch, some touch

Back 16

C fibers (postganglionic autonomic)

Front 17

Sensory receptors provide localization of a stimulus, by virtue of

Back 17

Specificity: to a stimulus by virtue of its structure
Intensity : of stimulus information by the number of axons creates
Spatial discrimination: high or low receptor densities in different parts of the body

Front 18

Receptors may be rapidly adapting, thus being useful for recognizing

Back 18

edges, vibration, and direction of a moving stimulus on the skin. Examples are: Pacinian corpuscle, Meissner's corpuscle and peritrichial endings.

Front 19

Receptors may be slowly adapting, thus being useful to recognize

Back 19

sustained touch or stretching of the skin. Examples are: Merkel's disc and Ruffini end organs.

Front 20

Receptors in muscle, Proprioceptors, help you know

Back 20

"where you are in space". These signal the onset of muscle contraction, the degree of muscle shortening, and the stretch of muscle and tendon. Examples are: Muscle spindles and the Golgi tendon organs.

Front 21

The frequency of action potentials is a measure of

Back 21

the intensity of the stimulus.

Front 22

The axons with large diameter have

Back 22

Fastest conduction

Front 23

The primary afferent axon will carry the information about the sensory stimulus towards the central nervous system. This axon has a cell body, which is found in

Back 23

the dorsal root ganglion

Front 24

The peripheral process is the primary afferent axon in touch with the receptor, and the central process of this neuron forms

Back 24

the dorsal root, which enters the spinal cord.

Front 25

The secondary neuron quickly sends its axon to the other side of CNS, i.e.

Back 25

contralateral to the origin of the stimulus.

Front 26

The tertiary neuron, in thalamus, sends its axon to

Back 26

cerebral cortex: contralateral cortex analyzes the stimulus.

Front 27

The axon enters at the dorsal lateral fissure and joins the adjacent dorsal column. This system carries

Back 27

ine tactile, discriminatory sensations and position sense(proprioception).

Front 28

Subdivisions of the dorsal column are

Back 28

medial fasciculus gracilis, and a lateral fasciculus cuneatus

Front 29

Fasciculus gracilis carries information from below

Back 29

T6, i.e. principally lower extremity, and F. cuneatus carries information from above T6

Front 30

he dorsal column axons end by a synapse in

Back 30

nucleus gracilis, or nucleus cuneatus respectively, which are found in the medulla of the brain stem.

Front 31

The axons from neurons of n. gracilis and n. cuneatus cross to the contralateral side, through

Back 31

internal arcuate fibers to form the medial lemniscus

Front 32

The medial lemniscus continues to ascend in the brain stem, changing orientation in pons and midbrain while maintaining the

Back 32

somatotopic segregation, and ends in a thalamic nucleus called Ventral posterior lateral (VPL).

Front 33

Neurons of the VPL project to

Back 33

primary somatosensory cortex, in the postcentral gyrus of the parietal lobe. The homunculus is now oriented with the feet on the medial surface of the hemisphere (in paracentral lobule) and body, upper extremity and hand progressively represented down the side of the hemisphere on the postcentral gyrus.

Front 34

The primary afferent axon, upon entering the spinal cord, will have branches (collaterals) to share the sensory signal with

Back 34

local reflex and the cerebellum (works at unconscious level) by a synapse with spinal cord neurons, whose axons form spinocerebellar tracts.

Front 35

Muscle cells within the spindle are small and they are in
the spindle receptor meaning they are

Back 35

intrafusal (inside the fibers)

Front 36

The
spindle is suspended within the muscle to muscle cells.
It detects

Back 36

the length and change in length of the muscle

Front 37

When the muscle is contracted, the muscle cells
unloads the spindle receptor so sensory feeback is

Back 37

stopped (afferent)

Front 38

There is also a muscle
efferent that modifies how long the receptor is..so if we
want to stretch out our arm..there's a point in which the efferent will tell the spindle
efferent will tell the

Back 38

that it is reaching
the point in which it needs to stay in order for the
spindle to keep sending efferent info of the movement

Front 39

How does the Golgi Tendon work?

Back 39

The Golgi tendon organs which axons come down and
break up into fibers around the collagenous fibers of the
muscle. If the muscle is contracted the collagenous
fibers pull together creating pressure on the Golgi
tendon organs receptor and that will send signal about the tension of the muscle

Front 40

Receptive fields on the back are large
because

Back 40

we don't need a great level of detailed info in
the back, but the fingers have small receptive fields that
allowed for picking up more detailed info.

Front 41

Dorsal root ganglion cells send primary Afferents to the
receptors on the skin ( we can also say that what gets
to the receptor is

Back 41

is the peripheral process of dorsal root
ganglion cells) central process of the dorsal root
ganglion leads to the formation of the dorsal root on the
spinal cord where there are the longest dorsal roots and
ventral roots

Front 42

what happens to sensation if one dorsal root is destroyed?

Back 42

it would not greatly diminished sensations because primary afferents overlap in the periphery

Front 43

But if there's a slip disk and puts pressure
on the dorsal root, the pain can be

Back 43

very specific to that
area.

Front 44

The neurons of dorsal root ganglia with the smallest
receptive fields on the skin would be found at cervical

Back 44

upper extremity

Front 45

Medial division of a dorsal root is
Lateral division of a dorsal root is

Back 45

myelinated
unmyelinated or little myelin

Front 46

Some collateral go to deep parts of dorsal horn and
some have

Back 46

have a branch going to a specific motor neurons. This is basis for stretch reflex and it is a monosynaptic reflex

Front 47

Monosynaptic innervation is not used everywhere because

Back 47

polysynapses increase the flexibility of ways to modify a given response.

Front 48

Rising up in the dorsal column collaterals go to

Back 48

our conscious levels

Front 49

The dorsal columnmedial
lemniscus
system

Back 49

5. Somatotopy is retained
throughout the system
4. Ends with synapse in thalamus
2. Secondary neurons in
Dorsal column nuclei.
3. Axon of 2nd neuron crosses
Midline, forms medial lemniscus
1. Primary neurons in
Dorsal root ganglia

Front 50

Dorsal spinocerebellar tract:

Back 50

Arises from neurons in the nucleus dorsalis of Clarke and enters the ipsilateral cerebellum via the inferior cerebellar peduncle.

Front 51

Ventral spinocerebellar tract:

Back 51

Arises from border cells of spinal gray and the axons ascend partly crossed to enter the cerebellum via the superior cerebellar peduncle. Most of the crossed fibers are thought to recross once in the cerebellum.

Front 52

Cuneocerebellar tract:

Back 52

Arises from the external (accessory) cuneate nucleus and the axons enter the ipsilateral cerebellum through the inferior cerebellar peduncle.

Front 53

v but the main
sensory nucleis is similar to the dorsal column medial
limniscus in that relays

Back 53

it is relaying fine tactile info like from
the lips and gets that info and relays it to the trigeminal thalamic tract

Front 54

thalamic tract . The mesencephalic tract and nucleus of
v is a group of neuron that are supposed to be in the
trigeminal ganglis area but

Back 54

are displaced into cns so they're supposed to be peripheral but are displaced.

Front 55

Mesencephalic Tract and
Nucleus deals with stretch receptor in

Back 55

muscles of mastication

Front 56

Central procces of mesencephalic tract ends in

Back 56

in the
Motor nucleus of V, for a
monosynaptic stretch reflex

Front 57

A lesion of the left dorsal column in the spinal cord will
result in

Back 57

loss of propriocenption on the left below the
lession because the primary Afferent stays on the same
side and the deficit is always related to what part is
disconnected from the conscious levels.

Front 58

Axons carrying info for two point discrimination on the
lips will synapse in

Back 58

main trigeminal nucleus

Front 59

Mesencephalic receives info from the stretch receptors
of mastication and it transmits it to

Back 59

main trigeminal nucleus

Front 60

Pain is mostly transmitted to the

Back 60

spinal trigeminal nucleus

Front 61

Areas with greater
receptor density have

Back 61

larger cortical
fields.

Front 62

Afferents relaying info about the spinal cord end in

Back 62

Ventral Posterior lateral in thalamus then they go to internal capsule

Front 63

Afferents from face (trigeminal) end in

Back 63

Ventral Posterior medial in thalamus then they go to internal capsule

Front 64

A lesion of the medial lamniscus on the left side in the
upper medulla will result in

Back 64

loss of propriocenption on
the contralateral side of the body

Front 65

The sensory homunculus
on the postcentral gyrus had the Lower extremity
located in the distribution of which artery

Back 65

anterior cerebral artery

Front 66

The cerebellum acts upon motor function at an

Back 66

unconscious level.

Front 67

In spinal cord collaterals from the same axons that
contributed to dorsal column will synapse in nuclei
with neurons projecting to

Back 67

the cerebellum

Front 68

The cerebellum deals with sensory info from

Back 68

the same
Side of the body and influences motor output related to
the opposite side of the body

Front 69

Cerebral cortex
influences motor output on

Back 69

output on the contralateral side of the body

Front 70

To which part of cerebellum
do the spinal afferents connect?

Back 70

Vermis and Anterior lobe!

Front 71

Ventrospinaocerebral tract is thought of as not reflecting
specific sensory info but info that relays to

Back 71

motor
program that is coordinated to spinal cord.

Front 72

The trigeminal system conveys sensations for the face similar to

Back 72

the spinothalamic and the dorsal column - medial lemniscus systems.

Front 73

Ventral trigeminothalamic tract, contralateral to

Back 73

sensory origin and ends in VPM thalamus.

Front 74

Main Sensory Nucleus (Principal or Chief), relays

Back 74

discriminating tactile sensation of face

Front 75

Dorsal trigeminothalamic tract,

Back 75

ipsilateral and small

Front 76

jaw jerk reflex, tests

Back 76

afferent limb on V3 and synapse at trigeminal motor nucleus, and the efferent limb on V3

Front 77

Corneal reflex, tests

Back 77

afferent limb on V1 and synapse at facial motor nucleus, and the efferent limb of facial nerve.