conduction system

Question 1

how does the sensory signal enter the cord?

Answer 1

Almost entirely through the sensory posterior dorsal roots –> dorsal root ganglia

Question 2

what happens to the signal once it enter the spinal cord?

Answer 2

Two separate destination:

1- One branch of the sensory nerve terminates almost immediately in the gray matter of the cord and elicits LOCAL CORD SEGMENT REFLEX

2- Another branch transmits signal to higher levels of nervous system to higher level in the cord itself or to the brain stem or even cerebral cortex

Question 3

what is the function of relay stations in the spinal cord?

Answer 3

Screening and filtering processes

Question 4

where is the spinal motor neurons located ?

Answer 4

anterior/ventral horns of the grey matter

Question 5

what do the ventral/anterior horns give raise to?

Answer 5

Neve fibers that leaves the spinal cord then directly innervate the skeletal muscles

Question 6

what are the types of motor nerve fibers?

Answer 6

alpha motor

Gamma motor

all part of the A group

Question 7

what is a muscle spindle ?

Answer 7

encapsulated muscle fibers distributed throughout the belly of the muscle

Question 8

what is the function of muscle spindles?

Answer 8

information about the length and rate change of the muscle

Question 9

what is golgi tendon organs?

Answer 9

organs found in the muscle tendon

Question 10

what is the function of golgi tendon organs?

Answer 10

Information about tension/ force or the rate of change of tension/force

Question 11

what is the composition of muscle spindle ?

Answer 11

3-12 tiny intra-fusal fibers that are surrounded by

LARGE extrafusal fibers

Question 12

what are the types of intrafusal fibers?

Answer 12

nuclear bag–> 1-3 in each spindle

Nuclear chain –> 3-9 in each spindle

Question 13

Which one of the intra-fusal fiber is the primary ending ?

Answer 13

Nuclear bag –> annulo spiral ending

Question 14

which one of the intra-fusal fibers is the secondary ending ?

Answer 14

nuclear chain–> flower spray ending

Question 15

which SENSORY afferent nerve fiber is dominant in the nuclear bag?

Answer 15

1A –> SUBDIVISION OF THE ALPHA GROUP FROM GROUP A

thick myelinated fibers which rapidly conduct 120 m/sec

Question 16

which SENSORY afferent nerve fiber is dominant in the nuclear chain ?

Answer 16

type II —> beta group of the A group

Less in diameter

Question 17

what is the function of 1a in the nuclear bag? ( primary ending)

Answer 17

Dynamic response

they provide information about the speed of movement and allow for quick corrective movements

( dynamic –> mean visible movement )

Question 18

what is the function of type 2 fibers ( beta subdivision of group A ) in the nuclear chain ( secondary nerve ending )?

Answer 18

Sense mainly static changes in muscle length

like muscle tone

Question 19

So which ones is secondary and which one is primary and which is more dominant in each spindle ?

Answer 19

Primary –> type 1a –> DOMINANT IN BAG –> dynamic

Secondary —> type 2 ( beta ) —> dominant in chain –> static

Question 20

if type 1a fibers ( subdisivion of alpha group ) is in the muscle spindle primary ending then whats the function of 1b?

Answer 20

Golgi tendon organ reflex

Question 21

what are type 3 fibers? and its function?

Answer 21

they are delta fibers ( subdivision of A )

pain and ocld receptors ; some otuch receptors

Question 22

what is a type 4 fibers and its function?

Answer 22

type C nerve fibers

dorsal root –> pain temp and other receptors

Question 23

what does the alpha MOTOR neurons innervate?

Answer 23

Extrafusal fibers

they give rise to large type A alpha motor nerve fibers averaging 14 micrometers in diameter

the sensory alpha neurons (1a ) is sensory not motor

Question 24

what is the function of alpha motor neuron?

Answer 24

stimulation of a single alpha nerve fibers excites from three to several hundreds skeletal muscle fibers which are collectively called the motor unit

Question 25

what is the motor innervation of the INTRAFUSAL MUSCLES?

Answer 25

Gamma motor neurons averaging 5 micrometers in diameters they are subdivision of A group

Question 26

which type of gamma motor neurons innervate the nuclear bag inside the intrafusal muscle?

Answer 26

Dynamic GAMMA motor neurons

Question 27

which type of gamma motor neurons innervate the nuclear chain inside the intrafusal muscle?

Answer 27

STATIC GAMMA MOTOR NEURONS

Question 28

how does muscle spindle operate in reflexes?

Answer 28

1- stretching of the muscle activates the muscle spindle ( by hitting the tendon ) 2- since we stretched it ( its dynamic ) so the nuclear bag in the spindle will increase AP from alpha 1a fibers 3- these info reaches the spinal cord 4- it will lead to increased efferent output through ALPHA MOTOR neurons ( NOT SENSORY ) that are attached to the extra fusal fibers and it will cause contraction 5- the contraction will bring the muscle back to its normal length and then the firing rate of the 1a will decrease

Question 29

what are the components of a reflex?

Answer 29

reflx immediates invovulntary and instantaneous movement in response to a stimulus Components of a reflex arc : Stimulus Sensory receptor sensory afferent neurons ( like 1a and type 2 ) CNS integration Efferent motor neurons ( like alpha motor neuron ) effector --> targe tissue Response --> movement

Question 30

what are the developed reflex?

Answer 30

reflexed learned by development : innate ones --> genetrically or developmentally determined Acquired reflexed --> Learned

Question 31

what are reflexes by processing sites?

Answer 31

Spinal reflexes --> processed in the spinal cord Cranial reflexes -> processed in the brain

Question 32

what are reflexes classified as a response?

Answer 32

Somatic reflexes --> control skeletal muscle contraction, include superficial and stretch reflexes Visceral autonomic reflexes --> control actions of smooth and cardiac muscles, glands

Question 33

what are reflexes classified by complexisity of circuit ?

Answer 33

MONO SYNPATIC --> one synapses Polysynaptic --> Multiple synapses ( 2-hundreds )

Question 34

describe monosynpatic reflexes?

Answer 34

simple reflexes 1- sensory neuron ( afferent ) directly synapse into motor/somatic neurons ( Efferent )) NO INTERNEURONS

Question 35

how is the outcome of a monosynaptic reflex determined ?

Answer 35

The outcome of this reflex depends on summation of the impulses at the cell body of the efferent neurons --> TEMPORAL SUMMATION

Question 36

how does the integration of monosynaptic reflex determiend?

Answer 36

integration process simply involved summation from one source like stretch reflex

Question 37

what do polysynaptic reflexes have?

Answer 37

ONE INTERNEURON OR MORE

Question 38

Describe the stretch reflex process ?

Answer 38

when a skeletal muscles with intact nerve supply is stretched it contacts The sense organ is the muscle spindle The impusles originating in the spindle are conducted in the spinal cord by fast sensory fibers that pass directly to the motor neurons which supply the same muscle STRETCH REFLEXES ARE THE BEST KNOWN STUDIED MONOSYNAPTIC REFLEXES

Question 39

Whats the neurotransmitter at the central synapse of a stretch reflex?

Answer 39

Glutamate

Question 40

describe static stretch reflex?

Answer 40

When the stretch is fixed or maintained --> static phases ( no change in length ) The primary and secondary (MAINLY ) ending that supply the nuclear chain fibers are stimulated ( type 2/beta ) The secondary ending are slowly adapting and continue to discharge so long as the stretch is maintained Slow prolonged stretch of a muscle continuous muscles contraction which is maintained so long as the muscle is kept stretch EXAMPLE --> MUSCLE TONE

Question 41

whats an example of polysynpatic reflexes?

Answer 41

withdrawal/flexor reflex and corssed extensor reflex polysynaptic reflex paths branch in complex fashion the number of synpases in each pf their branches is variable

Question 42

describe golgi tendon reflex?

Answer 42

The harder a muscle is stretched the stronger is the reflex contraction too much contraction can activate inverse stretch reflex --> to prevent injury and over stretching

Question 43

what are the sensors for the the anti over stretching reflex?

Answer 43

Golgi tendon organ

Question 44

what happens when they are stimulated?

Answer 44

Increased rate of firing of the afferent axons of golgi tendon organs stimulates inhibitory interneurons which inhibit alpha motor neurons of the muscles ( Extrafusal )

Question 45

what is the nerve fiber for the golgi tendon reflex?

Answer 45

1b --> subdivision of alpha subdivision of group A