0910 - gerak (08) dr zainuri_motorneuron

8/22/2019 0910 - GERAK (08) Dr Zainuri_Motorneuron

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SOMATOMOTOR

SYSTEM

Zainuri Sabta N

Dep. Anatomi FK UII


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Sel pada

jaringan

saraf

Neuron


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Organization of the

Nervous System

2 big initial divisions:

1. Central Nervous System

The brain + the spinal cord

The center of integration and

control

2. Peripheral Nervous System

The nervous system outside ofthe brain and spinal cord

Consists of:

31 Spinal nerves

Carry info to and from thespinal cord

12 Cranial nerves

Carry info to and from thebrain

Cerebrum


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Peripheral nervous

system


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Dorsal column

Lateral

column

Ventral column

& White Matter

GRAY

MATTER

(substantia

grisea)

WHITE MATTER

(substantia alba)


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Wheres the

insula?

Whats this

called?Whats the name of this

region


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Cerebral Cortex

3 types of functional areas:1. Motor Control voluntary

motor functions

2. Sensory Allow for conscious

recognition of stimuli3. Association Integration


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Cortical Motor Areas

Primary motor cortex

Brocas Area

Premotor cortex

Frontal Eye

Field

1. Primary Motor

Cortex

2. Premotor Cortex3. Brocas Area

4. Frontal Eye Field


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Sistem Motoris

1. Located in the precentral gyrus of each cerebral hemisphere.

2. Contains large neurons (pyramidal cells) which project to SC

neurons which eventually synapse on skeletal muscles

Allowing for voluntary motor control.

These pathways are known as the corticospinal tracts or

pyramidal tracts.

Substantia

grisea

Substantia

alba


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Primary (Somatic)

Motor Cortex

Somatotopy

The entire body is representedspatially in the primary motorcortex, i.e., in one region we haveneurons controlling handmovements and in another regionleg movements, etc.

Neurons controlling movement ofdifferent body regions do not

intermingle. What does it mean to say that

motor innervation iscontralateral?

Lets look at the motor

homunculus.


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Somatotopik


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Motor Cortex

Functions and properties of premotor cortex, motor cortex, and supplementary motorarea

The premotor cortex codes object position with respect to arm, independent of

fixation point and hand configuration

Primary motor cortex is sensitive to forces needed to perform a reaching movement

Like the somatosensory cortex, the motor cortex has a somatotopic map

The motor map can change after amputation, a result of loss of strength of

inhibitory interneurons connecting two areas in the motor cortex

Following amputation, the size of the motor region bordering amputated region

enlarges; phantom limb pain may be a result of size imbalance between the two

hemispheres

Following a lesion of a motor region, forced use of damaged region (constrained

motion rehabilitation) helps restore some motor function

Some primary motor cortex neurons respond to direction of muscle forces, thus

primary motor cortex is responsible for determining required muscle activity to

generate desired movement

Supplementary motor area (SMA) is responsible for memory-guided movements

whereas premotor cortex is responsible for visually-guided movements


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CORTICOSPINAL TRACT Origin at premotor cortex, motor cortex (M1),

somatosensory cortex (S1) Axons run through pyramids (medulla) and 90%

cross in lower medulla to form lateral

corticospinal tract and 10% remain ipsolateral

mostly going to ventral corticospinal tract

Split-brain patients (surgical separation of corpus

callosum)

Distribution of CST fibers provides good control of

contralateral arm/hand, but poor control of

ipsolateral and little control of ipso. Hand

Language center is on left hemisphere, can only

vocally identify items perceived by right side of

body (thus left arm is an alien arm)

Conduction speed in CST increases early in life

due to myelination but remains relatively

constant afterwards despite growth/lengthening

of pathway


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Attachment of skeletal muscle

Tendons

aponeuroses

fascia

origin insertion


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Penampang

otot


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Innervation of Skeletal Muscle

Terdiri dari satu atu lebih nervus

Satuan persarafan otot mengandung:

1. -motor axon (mensarafi otot extrafusal)

2. -motor axon (mensarafi otot intrafusal)

3. autonomic efferents

4. 2A aferen dari muscle spindle

5. 2B aferen dari organ tendon Golgi


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Motor Units

- A functional unit formed by a motoneuron and all

the muscle fibers that it innervates

- Accounts for simultaneous contraction of a

number of fibers within a muscle

- Size: small in muscles for precision tasks

large in postural muscles


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Gradation of muscle contraction

Strategy:

- Increase the impulse frequency of motoneuron

- Increase the number of motor unit recruited


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Motor unit


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Neuromuscular

junction


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PROPRIOCEPTIVE SENSATIONS

(PROPRIOCEPTION)

An awareness of the activities of muscles,tendons, and joints and of equilibrium is

provided by the proprioceptive, or kinesthetic

sense

(It informs us of: - the degree to which the muscles arecontracted

-the amount of tension created in the tendons

-the change of position of a joint

-the orientation of the head relative to the ground and in

response to movements (equilibrium)


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1. Enables us to recognize thelocation and rate of movement of

one body part in relation to others

2. Allows us to estimate weight anddetermine the muscular work

necessary to perform a task

3. We can judge the position andmovements of our eyes when we

walk, type or dress in the dark


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PROPRIOCEPTORS

Proprioceptors: receptors located in skeletal muscles, tendons in and

around synovial joints, and in the ear

1. Muscle spindles*: delicate proprioceptive receptors interspersed

among skeletal muscle fibers and oriented parallel to the fibers.

* consist of 3 10 specialized muscle fibers: intrafusal fibers

(partially enclosed in a connective tissue capsule that is filled with

lymph)

(in the central region of of each intrafusal fiber (represents the

sensory receptor area for a spindle: central receptors): few or no

actin and myosin contractile proteins (a) nuclear bag fibers, (b)

nuclear chain fibers)

The spindles are surrounded by skeletal muscle fibers of the musclecalled extrafusal fibers


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The central receptor area (cannot contract lacks of

myofilaments) contains two types of nerve fibers: (a)

Type Iafiber, innervates the exact center of theintrafusal fibers.

The branches of type Ia fiber: primary (anulospiral)

endings wrap around the center of the intrafusal fibers

(when the central part of the spindle is stretched

the primary endings are stimulated and send

impulses to the spinal cord)

(b) Type II fibers(their branches: secondary (flowerspray) endings which are also stimulated when the

central part of the spindle is stretched impulses to the

spinal cord


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The ends of the intrafusal fibers contain actin and myosin

myofilaments (contractile portions of the fibers)

(The ends of the fibers contract stimulated by gamma efferentneurons small motor neurons located in the anterior grayhorn of

the spinal cord)

EXTRAFUSAL FIBERS:

-Innervated by large motor neurons: alpha efferent neurons

(located in the anterior gray horn of the spinal cord, near gamma

efferent neurons)

THE MUSCLE SPINDLES:

- Stimulated in response to both sudden and maintained stretch onthe central areas of the intrafusal fibers

- monitor changes in the length of muscle contraction

PROPRIOCEPTORS


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PROPRIOCEPTORS

Flower spray

(1)

(2)

(3)

(4) Articular capsule


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b. Golgi tendon organ

a. Muscle spindle


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1. THE MUSCLE SPINDLES:

-Are stimulated in response to both sudden and maintained

stretch on the central areas of the intrafusal fibers

- Monitor changes in the length of a skeletal muscle by

responding to the rate and degree of change in length This

info. is relayed to the CNS: to assist in the coordination and

efficiency of muscle contraction

2. TENDON ORGANS (Golgi tendon organs)

-Proprioceptive receptors found at the junction of a tendon with

a muscle

-Help protect tendons and their associate muscles from

damage resulting from exessive tension


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Muscle Spindle Reflex


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Golgi Tendon Reflex


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Reflex Arcs

A reflex is a rapid,predictable motor responseto a stimulus. Unlearnedand involuntary.

Example?

Components of a reflex arc:

Receptorsite of stimulus

Sensory neurontransmitsafferent info to CNS

Integration center1 ormore interneurons

Motor neurontransmitsefferent signals to effector

Effector muscle or gland

0910 - gerak (08) dr zainuri_motorneuron

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