Neurobiology: Spinal Cord Anatomy, UMN/LMN, Proprioception, and Nociception

What is the primary function of the spinal cord?

To communicate with peripheral organs and connect with spinal nerves through afferent and efferent axons.

What are the two types of pathways in the spinal cord?

Ascending pathways (from spinal cord to brain) and descending pathways (from brain to spinal cord).

What anatomical feature of the spinal cord contains a bundle of nerve fibers after the cord has terminated?

Cauda equina.

What is the function of the filum terminale?

It is a terminal filament that anchors the spinal cord to the coccyx.

What are the three meningeal layers that protect the spinal cord?

Dura mater, arachnoid membrane, and pia mater.

What is the role of cerebrospinal fluid (CSF) in relation to the spinal cord?

CSF provides cushioning and support for the spinal cord.

What is the purpose of the denticulate ligament?

To anchor the spinal cord to the dura mater and maintain its position.

What are the two types of degenerative disk disease?

Type I (Extrusion) and Type II (Protrusion).

What characterizes Type I degenerative disk disease?

Nucleus pulposus extrusion leading to annulus fibrosus rupture.

What is discospondylitis?

Inflammation of the intervertebral disc caused by bacterial or fungal infection.

What is a common sign of degenerative myelopathy?

Progressive ataxia and paresis in older dogs.

What is equine motor neuron disease associated with?

Progressive weakness and atrophy in horses, often linked to Vitamin E deficiency.

What is the function of the dorsal horn in the spinal cord?

It receives sensory afferents.

What is the primary characteristic of the gray matter in the spinal cord?

It has a butterfly shape and contains high numbers of cell bodies and glia.

What is the role of the ventral horn in the spinal cord?

It contains alpha motor neurons that provide efferent output.

What is the function of the lateral funiculus?

It contains mixed tracts, both ascending and descending.

What does the term 'funiculus' refer to in spinal cord anatomy?

Groups of fiber tracts that run together within the same region of the spinal cord.

What is the significance of the central canal in the spinal cord?

It contains ependymal cells and cerebrospinal fluid.

What is the primary feature of the white matter in the spinal cord?

It consists of myelinated axons and contains fiber tracts.

What is the dorsal median sulcus?

A groove that divides the dorsal cord into right and left halves.

What is the ventral median fissure?

A groove that divides the ventral cord into right and left halves.

What is the primary cause of traumatic spinal cord injury?

Trauma from disc herniation or contusions due to accidents.

What is the typical age range for dogs affected by Type II degenerative disk disease?

Dogs aged 4-5 years.

What are the symptoms of spinal pain in discospondylitis?

Back pain, fever, and weight loss.

What is a neoplasm?

An uncontrolled, abnormal growth of cells or tissues in the body.

What is the anatomical landmark that indicates the intersection of dorsal roots?

Dorsolateral sulcus.

What is the primary function of the ventral funiculus?

It primarily contains descending tracts from the brain to the periphery.

What are the two types of motor neurons?

Upper motor neurons (UMNs) and lower motor neurons (LMNs)

Where are upper motor neurons located?

In the brain

What is the primary function of lower motor neurons?

To directly control muscle function

What regions of the spinal cord are enlarged?

Cervical and lumbar regions

What does the dorsal funiculus (DF) consist of?

A white matter bounded by the dorsal median and dorsolateral sulci

Where are lower motor neurons located?

In the spinal cord

What is the role of upper motor neurons in muscle function?

They modulate muscle function via lower motor neurons

What are the two systems of descending motor tracts?

Extrapyramidal system and pyramidal system

What is the function of the extrapyramidal system?

Involuntary control related to posture, balance, and gait

What is the function of the pyramidal system?

Voluntary control related to fine and skilled motor control

What is the significance of UMN lesions?

They result in loss of inhibition of muscles and can cause hyperreflexia

What are common signs of lower motor neuron lesions?

Hyporeflexia, muscle atrophy, and reduced muscle tone

What is the role of cerebrospinal fluid (CSF) in spinal cord protection?

It cushions the spinal cord, but it is not the only protective mechanism

What happens to reflexes in the case of lower motor neuron lesions?

Reflexes are diminished or absent

What is hyperreflexia?

An exaggerated reflex response due to loss of UMN inhibition

What clinical signs would indicate a lesion at the C1-C5 level?

UMN signs in both thoracic and pelvic limbs

What is the corticospinal tract important for?

Voluntary control of fine movements of limbs

What is the difference between ipsilateral and contralateral in terms of sensory signals?

Ipsilateral refers to the same side; contralateral refers to the opposite side

What are the signs of UMN disease?

Loss of voluntary movement, hyperreflexia, and muscle tone changes

What is the role of UMNs in maintaining posture?

They maintain tone in extensor muscles to support posture against gravity

What is myotatic hyperreflexia?

A reflex that can be induced by a lesion of the upper motor neurons

What are the effects of a lesion in the right half of the spinal cord from L4 to S2?

Signs of lower motor neuron damage in the pelvic limbs

What is the clinical significance of the corticobulbar tract?

It controls face, head, and neck movements

What is the primary role of the red nucleus in the extrapyramidal system?

To regulate involuntary movements related to posture and balance

What happens to muscle tone in lower motor neuron disease?

Muscle tone decreases, leading to hypotonia

What is the difference between voluntary and involuntary muscle control?

Voluntary control is conscious (pyramidal), while involuntary control is unconscious (extrapyramidal)

What is the result of UMN lesions on LMN function?

UMN lesions can lead to increased LMN activity and muscle atrophy

What are the types of sensory modalities discussed in the lecture?

Proprioception, nociception, exteroception, interoception

What is proprioception?

The sense of relative positions of body parts and joint movement.

What are the two types of proprioception?

Conscious and unconscious proprioception.

What is the role of muscle spindles?

They detect muscle stretch and provide information for coordination of posture and locomotion.

What is the function of Golgi tendon organs?

They sense tension in tendons and help regulate muscle contraction.

What are nociceptors responsible for?

They detect noxious stimuli and are involved in pain perception.

What is exteroception?

The sensory information from the immediate environment, including temperature, touch, pressure, and vibration.

What does interoception refer to?

The sensory information from internal viscera, such as digestion and breath.

What is the pathway of sensory signals from receptors to the brain?

First-order neurons transmit signals to the spinal cord, second-order neurons relay to the thalamus, and third-order neurons carry signals to the cortex.

What are the characteristics of A fibers?

A fibers are myelinated, large-diameter, and fast-conducting neurons.

What distinguishes C fibers from A fibers?

C fibers are unmyelinated, small-diameter, and slow-conducting neurons.

What is the significance of the dorsal horn in the spinal cord?

It is where sensory signals enter the spinal cord via the dorsal root.

How is proprioception tested during a neurological exam?

Through tests like hopping, wheelbarrow, and proprioceptive placing.

What does the knuckling test assess?

It tests proprioceptive deficits by observing the animal's ability to return its paw to normal position.

What does the hopping test evaluate?

It assesses balance and proprioception by observing the animal's ability to hop when weight is shifted.

What is the purpose of the hemiwalking test?

To assess strength, coordination, and proprioception by encouraging the animal to walk using limbs on one side.

What does kyphosis indicate in posture assessment?

A dorsal curvature of the spine.

What does lordosis indicate in posture assessment?

A ventral curvature of the spine.

What is the role of the cerebellum in proprioception?

It coordinates posture and locomotion based on unconscious proprioceptive input.

What is the function of the spinomedullary tract?

It transmits conscious proprioception signals from the spinal cord to the medulla.

What is the role of the spinocerebellar tract?

It transmits unconscious proprioception signals to the cerebellum.

What is the clinical significance of a lesion in the spinal cord?

It can lead to deficits in limb function, affecting both thoracic and pelvic limbs depending on the lesion location.

What does the term 'hyporeflexia' refer to?

A decrease in reflex responses, such as in the right pelvic limb in the context of spinal cord lesions.

What is the expected clinical presentation of a dog with a right spinal cord lesion from L4 to S2?

Normal reflexes in the right thoracic limbs and hyporeflexia in the right pelvic limb.

What is the difference between paresis and ataxia?

Paresis refers to weakness or partial loss of movement, while ataxia refers to lack of coordination.

What is the significance of sensory receptor thresholds?

It is the minimum level of stimulus intensity required to activate sensory receptors.

What is the primary role of proprioceptors?

To provide information about body position, motion, and equilibrium.

What does the extensor postural thrust reaction test assess?

It assesses motor or proprioceptive deficits by observing the animal's response when only pelvic limbs touch the ground.

What is the Wheelbarrow Reaction used to evaluate?

It assesses forelimb strength, coordination, and proprioception by lifting the hind limbs and observing the animal's movement.

What is the difference between visual and tactile placing?

In visual placing, the animal reaches out with limbs guided by sight; in tactile placing, limbs extend upon contact when the eyes are covered.

What is nociception?

The sensory process that detects noxious stimuli, which can be mechanical, thermal, or chemical threats.

What are the three types of pain?

Physiological pain, inflammatory pain, and neuropathic pain.

What is the role of the first-order neuron in the pain pathway?

It is a sensory afferent fiber with a receptor in the periphery that synapses in the dorsal horn of the spinal cord.

What is the function of C fibers in pain signaling?

They transmit dull, slow pain signals.

What is the Spinothalamic tract responsible for?

It carries pain and temperature sensations from the spinal cord to the thalamus.

What is the Gate Control Theory of Pain?

It explains how non-painful stimuli can inhibit pain signals, reducing the perception of pain.

What is the significance of the thalamus in pain perception?

It relays pain signals to the somatosensory cortex for localization and emotional processing of pain.

What is allodynia?

A condition where pain is caused by normally non-painful tactile stimulation.

What is hyperalgesia?

An enhanced sensitivity to pain, where a stimulus causes a greater pain response than normal.

What are common signs of pain in animals?

Change in behavior, continuous licking/grooming, gait changes, abnormal postures, and vocalizations.

What is the role of the cerebrum cortex in pain detection?

It is required for conscious pain perception and processing.

What is the difference between physiological pain and inflammatory pain?

Physiological pain is a natural protective response, while inflammatory pain occurs after tissue damage and subsides with healing.

What is neuropathic pain?

Pain that persists due to nerve damage, often chronic and difficult to treat.

What is the primary function of nociceptors?

To detect noxious stimuli and initiate pain signaling.

What is the role of the spinoreticular tract?

It transmits deep pain and visceral sensations, activating arousal and emotional responses.

What happens during a spinal cord reflex?

An automatic response occurs without conscious pain perception, indicating a reflexive action rather than voluntary movement.