Spinal tracts + Motor pathways Flashcards
Name the 2 neurons involved in the motor pathways and their function
UMN: upper moto neurons
LMN: lower motor neurons
These neurons are involved in transmitting signals from the brain to the muscles, they are involved in voluntary control in the corticospinal tract as well as fine motor movement
Describe the location, pathway and synaptic site of UMN in the in the corticospinal tract (pyramidal)
Location: UMN cell body is found in the frontal lobe, the axons travel through the internal capsule & descend through the brainstem.
Path: In lateral corticospinal most axons cross as medullary pyramids then descend to lateral region of spinal cord.
In the anterior corticospinal axons do not cross the medullary pyramids. UMNS cross over the spinal cord & synapse with LMN
Synaptic site: UMN’s & LMN synapse at the dorsal horn of the SC or in the motor nuclei in the cranial nerves
Describe the location, pathway and synaptic site of LMN in the corticospinal tract
(pyramidal)
Location: found in the anterior horn in the SC or in motor nuclei in cranial nerves
Path: LMN exit via ventral root/cranial nerves, the axons travel directly to the skeletal muscle
Synaptic site: LMN directly innervate skeletal muscles, triggering muscle contraction leading to voluntary movement
What is the role of the brainstem pathway?
This pathway is involved in involuntary movements & reflexes, e.g., coordination, balance & posture
Describe the location, pathway and synaptic site of UMN in the brainstem pathway (extrapyramidal)
Location: found in the brainstem (red nucleus & vestibular nuclei)
pathway: Axons of UMN travel down the brainstem motor tracts e.g., reticulospinal tract, some UMN may cross over and some may remain ipsilateral
synaptic site: Axons of the UMN synapse with the LMNS in the anterior horn of the spinal cord or the cranial nerves
Describe the location, pathway and synaptic site of LMN in the brainstem pathway (extrapyramidal)
Location: Located in motor nuclei of cranial nerves (head + neck), also found in the anterior horn of SC
Pathway: Axons travel through cranial/ventral nerves to innervate muscles
Synaptic site: LMNS control muscle contraction, influencing invountary movements e.g., posture
What happens if the UMNS & LMNS become damaged?
UMN: damage to the UMNs leads to spastic paralysis (strokes, MS & cerebral palsy) the muscles remain strong but stiff & difficult to move voluntarily.
LMNs: damage to LMNs results in flaccid paralysis & muscle weakness, as well as absent reflexes. The muscles are unable to contract and become wasted. (Polio, spinal cord injury)
Define the tectospinal tract
(extrapyramidal tract)
involved in head + neck movements in response to visual or auditory stimuli. Orient the head & neck towards stimuli.
It provides coordination & reflexive movements
Define the reticulospinal tract
(extrapyramidal)
Regulates posture, automatic movements & muscle tone. motor commands are sent to adjust the postural position & initiate voluntary movement.
Involved in walking (gait), breathing etc
Define the vestibulospinal tract
(extrapyramidal)
Needed for balance and postural control, it helps maintain upright position, response to gravity and keeps the head stable as the body moves. it carries relevant information to the head and body, it adjusts motor activity for relevant responses
Define the rubrospinal tract
(extrapyramidal)
Involved in fine motor control and movement, it allows flexion and extension of muscles. It uses motor control to control upper limbs, adjust muscle tone and coordinate reflexive movements
Describe the corticospinal tract
Vital for coordinated and skilled movements using voluntary control. Mostly in limbs & face. It allows a precise response to be given to stimuli
It uses fine motor control, which involves precise, intricate movements, especially in the hands, fingers, and facial muscles. Movements like writing, typing, or playing the piano are largely governed by the corticospinal pathway. It allows for dexterity in the fingers, which is necessary for tasks that require small, controlled movements.
Define the function and importance of the sensory pathway
It is needed to carry sensory information to the brain, conscious sensations reach the cerebral cortex, subconscious sensations do not
Function: To sense stimuli via receptors in skin, muscle & organs, allowing us to understand and respond to our environment and detect changes
Importance: helps us detect danger, changes in our environment and enable protective mechanisms. It allows us to remain balanced, good posture, coordination and spatial awareness. It allows us to interact with our environment through our senses e.g., taste, smell. It facilitates communication and learning from our environment.
Describe the stages in the generic sensory pathway
- Stimulus Detection: Sensory receptors detect specific stimuli (e.g., touch, temperature, pain).
- First-order Neuron: The receptor generates an electrical signal that travels through the sensory neuron to the spinal cord or brainstem.
- Relay in the Spinal Cord/Brainstem: The signal is relayed to a second-order neuron in the spinal cord or brainstem, often crossing over to the opposite side.
- Thalamus: The signal is sent to the thalamus, which processes and filters the information.
- Cerebral Cortex: The thalamus relays the information to the appropriate cortical area (e.g., somatosensory cortex), where the brain perceives and interprets the sensory input.
Describe the role of the spinothalamic tract
A major sensory pathway in the nervous system that transmits information about pain, temperature, and crude touch from the body to the brain. It is part of the ascending sensory pathways that convey sensory information to higher centers in the brain for perception and response.
Describe the stages in the spinothalamic tract
- 1st neuron detects a stimulus e.g., pain through receptors, neuron’s cell body is in dorsal root ganglion, axon enters SC via dorsal root
- 1st and 2nd neuron synapse at dorsal horn, 2nd neuron crosses over and ascends the spinothalamic tract up to brain
- 2nd & 3rd neuron synapse in the thalamus, 3rd neuron relays signal from the thalamus to correct area in SSC, 3rd neuron projects from thalamus to SSC where the brain processes & perceives stimuli e.g., pain, temp & touch
Describe causes and effects of damage to the spinothalamic tract
Damage to the spinothalamic pathway can result in a range of sensory deficits, primarily affecting pain, temperature, and crude touch sensations.
causes: SC injury as trauma to the spinal cord can sever or damage the spinothalamic tract, leading to loss of sensory function., stroke in the brainstem or thalamus can interrupt the pathway, affecting sensation., MS
effects:
- Loss of Pain Sensation (Analgesia): Damage to the spinothalamic tract can result in an inability to feel pain on the contralateral side (opposite side) of the body from the site of injury or lesion.
- Loss of Temperature Sensation (Thermal Analgesia): Affected individuals may lose the ability to sense hot or cold sensations, again typically on the opposite side of the body.
- Increased Sensitivity to Pain (Hyperalgesia): Sometimes, damage to sensory pathways can cause heightened sensitivity to pain in areas that are still functional.
Describe and explain the role & importance of the dorsal column pathway
DCP needed to transmit stimuli regarding fine touch, vibration and body position to the thalamus/SSC
This pathway allows the brain to perceive detailed and localized sensations from the body.
Describe the stages in the dorsal column pathway
- 1st neuron detects stimuli e.g., fine touch, receptors in skin/muscles sends signal along axon to dorsal root ganglion
- 1st order neurons enter dorsal column & travel up to the brainstem (NO SYNAPSING)
- at the medulla the 1st & 2nd neurons synapse in gracile nucleus, 2nd neurons cross over in the medulla & form a bundle of neurons (medial lemniscus) that ascend to the thalamus
- 2nd & 3rd neurons synapse in VLPN of thalamus, 3rd neurons project from thalamus to somatosensory cortex
- Info is processed at SSC allowing the brain to respond to sensory input e.g., texture, shapes
Describe the causes and effects of damage to the dorsal column pathway
Damages the body’s ability to sense body position
Cause: trauma e.g., spinal cord injuries
MS(degradation of myelin)
Tumors or Infections: Growths or infections in the spinal cord can compress or damage the dorsal columns.
effects:
- loss of proprioception, leads to difficulty with balance, coordination, posture
- Loss of Fine Touch Sensation: Patients may lose the ability to feel fine touch, such as distinguishing textures or identifying objects by touch alone.
Ataxia: A lack of coordination or balance, often due to the loss of proprioception, can lead to unsteady walking or trouble with tasks requiring fine motor control.
Compare the similarities and differences between the spinothalamic and dorsal column pathway
Both 1st order neurons travel in the dorsal root ganglion.
STP 1st neurons involved in temp/pain found in skin
DCP 1st neuron involved in pressure changes, found in muscles/tendons
2nd neuron in STP is found in dorsal horn, in DCP found in medulla
3rd neuron or STP & DCP are in thalamus
Define the function and importance of proprioceptors (Kinaesthetic receptors)
They are needed to provide info about the body’s position, movement & muscle tension, found in muscles/tendons, relay information to the brain
- enable spatial awareness
- enable balance & coordination
- enables motor control e.g., walking, allowing smooth movement
Define unencapsulated nerve endings and give 3 examples
A sensory nerve that has no connective tissue capsule, more exposed, involved with temperature, light touch & pain
examples: tactile discs, hair receptors & free nerve endings
Describe the form and function of free nerve endings, tactile discs and hair receptors
Fn: found in epithelium/connective tissue e.g., eye/epidermis
small thread-like that branch out to detect environmental changes
involved in pain, temperature and light touch sensations
tactile discs: found in the stratum basale of the epidermis, involved in touch, allows texture and shapes to be perceived, flat disc shapes that interact with Merkel cells, their flat form makes them very sensitive to pressure changes
hair receptors: found around the hair follicle, involved in hair movement, detects if hair is bent/moved, alerts us if things contact our skin, coiled/spiralled shape that wraps around hair follicle base
Define encapsulated nerve endings and give at least 3 examples
A nerve type surrounded by a connective tissue capsule which enhances sensitivity of receptor and provides protection to nerve fibers. They have the ability to adapt and respond quickly to stimuli e.g., pressure changes
examples: lamellated corpuscles, tactile corpuscles, muscle spindles, golgi tendon organs, Ruffini corpuscles & krause end bulbs
Describe the form and function of tactile corpuscles, Krause end bulbs & lamellated corpuscles
Tactile corpuscles- e.g., Meissners, found in dermal papilla (lips & fingertips) detect light touch & vibrations, responds to low Hz & rapid changes in texture
Structure: ovoid shape, consists of flattened cells in a capsule surrounding a nerve ending
Krause end bulbs: found in mucus membranes (eyes & genital) detect cold and light touch
structure: oval shape, bulbous, has nerve endings
Lamellated corpuscles- e.g., Pacinian, found in breasts/dermis/genitals, detect deep pressure, tickles & stretch, sensitive to high Hz
Structure: oval shape, multilayered, has a central nerve surrounded via connective tissue layers
Describe the form and function of Ruffini corpuscles, muscle spindles & Golgi tendon organs
Ruffini-found in dermis/joints, involved in skin stretch & joint movement, help detect sustained pressure changes.
Structure: elongated spindle shape, a central nerve surrounded by a capsule
Muscle spindles: Found in tendons, involved in detecting muscle stretch
Structure: muscle fibers surrounded via capsule, parallel to other muscle fibers, sensitive to changes in muscle length
Golgi organ tendons: found in tendons, detects tension, sensitive to muscle tension/force
structure: spindle-shaped, fibers woven through connective tissue layers, shape enables changes to be monitored to help prevent muscle injury, signals brain to reduce tension
Describe the need for a rombergs test, the method and interpretation of results
A test used to assess a person’s balance & proprioception to help identify neurological conditions
Method:
1. person stands upright with feet together, arms by sides
2. Person told to open their eyes for 20/30s to observe baseline stability
3. Person is asked to close their eyes for 20/30s in standing position, any swaying or imbalance is noted
PR: If a person sways or loses balance, suggests there is a problem with sensory input, indicates damage to dorsal column pathway
NR: no swaying, suggests that their sensory pathways are functioning well, does not indicate damage to the DCP
Describe the function and importance of the spinocerebellar pathway
To carry information regarding the body’s position (proprioception) to the cerebellum. To coordinate smooth voluntary movement, balance & posture
- helps maintain an upright postition
- helps improve motor skills over time
- helps coordinate fine motor control for smooth movement
Describe the stages in the spinocerebellar pathway
- 1st order neuron detects a stimulus in muscles, joint or tendon, information is relayed in neurons at SC
- Information enters spinal cord and ascends spinocerebellar pathway, 2nd neurons transmits the signal towards the cerebellum
- Information is processed in the cerebellum to coordinate motor control, balance etc
- The cerebellum uses the sensory data to fine-tune and adjust motor commands sent to the muscles, helping with smooth and coordinated movement
Describe the causes and effects of damage to the spinocerebellar pathway
Damage to the SCP can affect coordination & balance.
causes: trauma e.g., SC injury, Ataxia (degenerative disease), stroke & MS (demyelination of neurons)
Effects: Ataxia: One of the most common effects is ataxia, which involves a lack of coordination of voluntary movements. Muscle weakness and hypotonia: Reduced or altered signals to muscles can lead to weakness and decreased muscle tone.
Compare the spinothalamic, spinocerebellar and dorsal column pathway
Spinothalamic: carries information about temperature, pain & touch, 2nd neuron crosses at SC, projects to somatosensory cortex, damage causes loss of function on OPP side
Spinocerebellar: Carries information about involuntary proprioception. No 2nd neuron cross over, does not project to SSC, damage causes loss of function on OPP side
Dorsal column: carries info about vibrations, fine touch and voluntary proprioception. 2nd neuron crosses at medulla, projects to SSC, damage causes loss of function on SAME side
Describe the dorsal spinocerebellar tract
- primary neurons in muscles, tendons & joints detect stimuli about body’s position, send signals to dorsal root ganglia along axon
- 2nd neurons synapse woth 1st neurons in nucleus doralis
- From there 2nd neurons ascend up SCP, ascend ipsilaterally to the cerebellum reaching cerebellar cortex
Describe the ventral spinocerebellar tract
- 1st neurons receive stimuli and transmit them to the spinal cord
- The secondary neurons synapse in the grey matter of the spinal cord
- in the VSCT 2nd neurons cross over to the opposite side of the SC,
- Project upwards to the cerebellum where motor coordination is influenced based on incoming stimuli
