ascending and descending pathways

SPINAL CORD

Continuous with the medulla oblongata

L1

Spinal Cord: Terminates at the lower border of

meninges, CSF

Spinal Cord: Surrounded by the same \___ wrapped with \___

31

Has \__ pairs of spinal nerves

motor

Anterior \= \___ \= dorsal; move

sensory

Posterior \= \___ \= ventral; feel

gray

The spinal cord's \___ matter is found in the medial part (butterfly shape) which changes shape depending on the level of the spine.

white

Spinal Cord is surrounded by ascending and descending \___ matter, depending on the pathway.

CSF

At some point in the spine, there is a duct where the \__ passes through.

posterior columns

Spinal Cord: \= sense of touch, vibration, fine touch

SENSORY TRACTS

Responsible for processing sensory information, It helps process physical phenomenon around us into a form we can organize and interpret to make sense of the world

receptors, neural pathways, thalamus, and sensory cortices

Sensory Tract Contains

special senses

Sensory Tracts: These are called \___ \___ because there are sensory organs assigned per sensation. For example, you have your eyes for the sense of sight, nose for smell, etc.

Receptors -\> First-order neuron -\> Spinal Cord/Brain Stem -\> Second-order Neuron -\> Thalamus -\> Third-Order Neuron -\> CORTEX

GENERAL ORGANIZATION OF ASCENDING TRACTS

First-order neuron (afferent neuron)

GENERAL ORGANIZATION: The first one that will receive the information from your receptors.

Spinal cord

GENERAL ORGANIZATION: If sensation is received from below the face.

Brainstem

GENERAL ORGANIZATION: If sensation is received from the face or oral sensations.

Second-order neuron (interneuron)

GENERAL ORGANIZATION: Interneuron serves as a bridge between the spinal cord or the brainstem and the thalamus

Thalamus (one or more thalamic nuclei)

GENERAL ORGANIZATION: Depending on the type of sensation, it will pass one or more thalamic nuclei, Since the anatomy of the thalamus is that it has a lot of small nuclei, each nuclei will receive a specific type of sensation or stimuli only

Third-order neuron

Connects the thalamus to a specific cortex, Depending on the type of sensation, it will go to a specific cortex where it will get processed

downwards

The reason why it is called the ascending pathway is because you start \____. \_____, meaning our sensory receptors because they are the ones receiving the stimuli.

afferent

towards the brain, sensory

efferent

pababa, motor

PRIMARY SENSORY AREAS

Endpoint of your ascending pathway or somewhere in the cortexl; Register sensory impulses from the periphery to the thalamus and upward to the cortex

BA 41, 42

PRIMARY SENSORY AREAS: Primary Auditory Cortex

BA 1, 2, 3

PRIMARY SENSORY AREAS: Primary Somatosensory Cortex

BA 17

PRIMARY SENSORY AREAS: Primary Visual Cortex

thalamus

PRIMARY SENSORY AREAS: The \___ has a lot of connections which makes it possible for it to be a relay system of the different pathways so that it helps organize things and sends them to the right part of the brain for further processing.

ASSOCIATION CORTICES

AKA secondary association areas, Margins for each area are said to be vague, Extension of the primary sensory receptor areas

Somatosensory

ASSOCIATION CORTICES: BA 5, 7

Auditory

ASSOCIATION CORTICES: BA 42, 22

Visual

ASSOCIATION CORTICES: BA 18, 19

gnosis

ASSOCIATION CORTICES: Main function: \___ \= knowing

agnosia

When you have a deficit in sensory association, the condition is called \___; lack of knowing or recognizing a specific sensory input

meaning and significance

ASSOCIATION CORTICES: Add \___ \__ \___ to the sensory input: When you see something, it's supposed to match your sensory input with any past experiences or own knowledge of certain objects of certain stimuli, and it taps into your memory from other areas & help blend it or obtain higher cortical sensory information (complex awareness of the object \= able to perceive the object better)

perception

ASSOCIATION CORTICES: Many kinds of \___: depths, distance, space, ... intuition (but to a certain extent only)

SENSORIMOTOR INTEGRATION: Process that allows execution of certain voluntary motor behavior in response to specific demands of environment

intentional motor response

Integrate sensory information from sensory system → \___ \___ \__ (behavior) carried out by motor system

Peripheral sensory feedback

crucial in execution of correct voluntary movement; Usually achieved by the sensory system; Multiple senses are involved like Visual, Audition, Proprioception (knowing where the body parts are), Somatosensation, sense of touch

wrong movement

without peripheral sensory feedback, you are having a higher chance of making a

behavior

Sensory information + motor responses \=

MOTOR SYSTEMS

system responsible for producing these observable responses/behaviors

MOTOR SYSTEMS

Elaborate network of multiple, hierarchically organized feedback loops allowing movement

Descending Control Systems, Spinal Cord Circuitry, Modulation Centers

MOTOR SYSTEMS: Components:

Descending Control Systems

MOTOR SYSTEMS: Components: Pyramidal motor system (voluntary movement), Extrapyramidal motor system (involuntary movements), Visceral motor system (visceral organs *stomach, etc.)

Pyramidal motor system

MOTOR SYSTEMS: Descending Control Systems: voluntary

Extrapyramidal motor system

MOTOR SYSTEMS: Descending Control Systems: involuntary

Visceral motor system

MOTOR SYSTEMS: Descending Control Systems: visceral organ

Modulation Centers

MOTOR SYSTEMS: Components: Basal ganglia & Cerebellum; feedback input to and from the brain

Descending Pathway

The first neurons that would receive the impulses

1st- order Neuron

Descending Pathway: Cell body in the cortex

2nd-order Neuron

Descending Pathway: Anterior gray column of the spinal cord, Especially if it goes down to your limbs; essentially they are in the brainstem

3rd- order Neuron

Descending Pathway: Anterior gray column (towards muscle), AKA lower motor neuron

reflexes

In some cases, the 1st-order neuron goes straight to the 3rd-order neuron, usually the function is for \___.

Lower motor neurons

Innervate skeletal muscles (directly connected); only way the brain can communicate with the muscles because they have direct synapse with the muscle as a result would be a muscle contraction/ movement

excitatory acetylcholine

Lower motor neurons: Release \___ \___ at neuromuscular junction that trigger action potential → muscle contraction

final common pathway

Lower motor neurons: Considered the "\___ \____ \___" because neural impulses from all tracts go through them

anterior horn

Lower motor neurons can be seen in the \___ \___ of the spinal cord which controls the limb and body movements

brain stem

Lower motor neurons can also be found in the \___ \___ where the nuclear nerves that control facial and head movements.

Alpha Motor Neurons

TYPES OF LMNs: Innervates the main fibers that cause muscle contraction (extrafusal fibers), Most abundant in our muscle

Extrafusal fibers

comprise the bulk of the muscle & form force generating structure; causes muscle contraction

Beta Motor Neurons

TYPES OF LMNs: Innervate both extrafusal and intrafusal fibers of muscle spindles, Very few amounts in our muscle

Gamma Motor Neurons

Supplies efferent innervation to the intrafusal fibers of muscle spindles, They also contain contractual elements.

Intrafusal fibers

TYPES OF LMNs: specific muscle fibers that are buried inside the muscle and they act as sensory receptors

motor neuron pool

Motor Unit: Each muscle is supplied by a cluster of lower motor neurons (\___ \____ \___)

1 muscle

Motor Unit: \___ \___\= lots of muscle fibers

1 muscle fiber

Motor Unit: \___ \___\= 1 LMN

1 LMN

Motor Unit: \___ \___\= lots of muscle fibers

1 LMN

Can say that the muscle fiber is kind of loyal to \__ \____ but the motor neuron is not loyal because it spreads out to other muscle fibers in the specific muscle.

1 LMN + muscle fibers

1 motor unit \=

motor neuron pool

All motor neurons innervate a certain muscle that is part of that \___ \___ __.

Anterior horn cell,Cranial nerve (if nasa brian stem), Peripheral axon and branches

Parts of a LMN

All muscle fiber/s (extrafusal)

these are the muscles that would comprise the power/movement/force generating structure of the muscle; Motor unit ratio*

muscle use

TYPES OF MOTOR UNITS/FIBERS: All skeletal muscles contain the three types (proportion depends on \___ \___)

1

BUT 1 motor unit \= \__ type of fiber

Slow twitch (Type I)

TYPES OF MOTOR UNITS/FIBERS: Slow, low force activities (standing)

Fast twitch, fast fatigue-resistant (Type IIA)

TYPES OF MOTOR UNITS/FIBERS: Fast, moderate force activities (jogging), midpoint of activities

Fast twitch, fast fatigable (Type IIB)

TYPES OF MOTOR UNITS/FIBERS: Very fast, activities that require a burst of large amounts of force (sprints), Cannot hold for long periods of time, fast fatigue

Fast twitch, fast fatigable (Type IIB)

very high force generated but ang bilis bumagsak ng force na yun overtime

Fast twitch, fast fatigue-resistant (Type IIA)

moderate force but medyo mabilis din siya ma-fatigue pero mas matagal mo siyang magagamit sa muscle

Slow twitch (Type I)

force is quite low but it is really sustained over time because ayaw natin mapagod for certain activities like maintaining your posture, walking, and even other smaller movements.

Henneman's Size Principle

MOTOR NEURON RECRUITMENT: Orderly recruitment based on size; Smallest to largest; Type I → type IIA → Type IIB; Motor units are recruited according to magnitude of force they can generate

minimize amount of fatigue, increase precision of movement

Main purpose: Henneman's Size Principle

higher-order muscles

Comparing the other types of movements we see in SP, most of the time, we do not really recruit other types of muscle. However, looking at it in the context of someone who has a disordered anatomy and physiology, they might need to recruit \___ \___ \___ in order to generate more force that they need in order to communicate or swallow.

Reflexes

Involuntary or subconscious response to a stimulus

Spinals, Bulbar, Midbrain, Cerebellar

Reflexes: types (acc. To level of representation); usually at what level they are processed

Segmental

Types (acc. To neuron recruited): local circuit neurons (knee jerk)

Intersegmental

Types (acc. To neuron recruited): different circuits (swallowing)

Recepto, Sensory neuron, Integration center, Motor neuron, Effector

PARTS of a REFLEX:

brain

in this pathway, not all reflexes go up to the \___

receptor

depending on the reflex, any \___ will allow you to receive the stimuli & it really processes in the spinal cord going back to the muscle

Muscle spindles

Serve as sensory receptors within striated muscles, Contain intrafusal fibers, Located parallel to extrafusal fibers, Provide afferent information regarding muscle stretch (length and rate)

Gamma motor neurons

Provide efferent innervation to intrafusal fibers (contractual fibers), Adjusts to gain (aka strength of the muscle for differentiation)

Gamma motor neurons: Gain

When EF are stretched, IF are stretched as well (to get better sensory information regarding the muscle's position or the muscle's force); If the IF does not stretch, there will be a lag on the information you will receive; IF needs to be attuned to the movement to your EF to keep up with the gain of the muscle

muscle spindle taut

Gamma motor neurons: Contracts not for movement but to keep the \___ \___ \___ → sensitive to stretch

MYOTATIC STRETCH REFLEX

Muscle response to stretching within the muscle

gain

When muscle is passively stretched → intrafusal fibers of the muscle spindle is also stretched to a certain degree (called \___)

Gamma motor neurons

then act to adjust the gain, thereby contracting/shortening the intrafusal fibers

sensitivity

MYOTATIC STRETCH REFLEX: Preserves the \___ of the muscle to unexpected stretches of the muscle

Sensory receptor (muscle spindle), Afferent neuron, Interneuron, Efferent neuron (AMN & GMN), Effector organ (EF muscle fibers)

Components of Gamma Motor Neurons