Neuro Quiz #1

What structures make up the CNS?

What structures make up the CNS?

Brain and spinal cord

What structures make up the PNS?

Cranial and Spinal Nerves

Cerebral Hemispheres

Right and Left Hemisphere

Corpus Callosum

A thick bundle of nerve fibers ;connects the two hemispheres of the brain, ensures that both sides of the brain can locate and send signals to each other.

Spinal Nerves

31 pairs; 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal

Cranial Nerves

12 pairs; I-Olfactory, II-Optic, III- Oculomotor, IV- Trochlear, V- Trigeminal, VI- Abducens, VII- Facial, VIII- Vestibulocochlear, IX- Glossopharyngeal, X- Vagus, XI- Spinal Accessory, XII- Hypoglossal.

Corticobulbar tracts

Mostly bilateral innervation from the cortex (upper face) and unilateral innervation (below the eyes). Because cranial nerves V, VII, IX, X, XI receive mostly bilateral innervation.

Corticospinal tracts

Leads to spinal nerves, mostly originates in the motor strip.

90% cross at medulla oblongata (pyramidal decussation) Lateral corticospinal tract- contralateral innervation _ L brain controls R hand. Skeletal muscle controls of more distal muscles like the hands (especially delicate skilled movements of hands (some forearms and toes)

10% (anterior corticospinal tract) cross below medulla – cervical level – control axial & girdle muscles of the trunk

Gray Matter

the darker tissue of the brain and spinal cord, consisting mainly of nerve cell bodies and branching dendrites.

White Matter

the paler tissue of the brain and spinal cord, consisting mainly of nerve fibers with their myelin sheaths.

Lower Motor Neuron

Responsible for transmitting the signal from the upper motor neuron to the effector muscle to perform a movement.

Motor Unit

A motor neuron and all of its associated muscle fibers are the basic functional units of skeletal muscle.

The process of neural transmission

1. A nerve impulse travels

2. Voltage-gated Ca+ channels open

3. Increased concentration of Ca+

4. Neurotransmitters diffuse across the synaptic cleft

5. Binding of neurotransmitters

6. Large Depolarization

Contralateral sensorimotor control

the arrangement whereby the motor cortex of each cerebral hemisphere is mainly responsible for control of movements of the contralateral (opposite) side of the body.

CNS anatomical symmetry

Both sides of the CNS anatomy is symmetrical.

Unilateral functional differences

The hemispheres have equal potential to develop language and other skills until age two

Cerebellum

Muscle synergy, coordination and smoothness in time and space, muscle tone, movement range, movement strength, equilibrium, compares efferent to afferent signals, important for motor learning and error control device.

Thalamus

Superior to brainstem. Considered subcortical. Is formed as the brainstem branches upward. Paired and oval-shaped bodies. Channels all sensory information (except olfaction) to cerebral cortex. Integrates sensorimotor information; with basal ganglia and cerebellar input, signals are sent via the Thalamus to the motor and pre-motor areas. Regulates cortically mediated speech, language, and cognitive functions.

Midbrain

Above the pons. Superior cerebellar peduncle-connecting brain centers with the cerebellum. Motor fibers leave cerebellum after analysis (go to thalamus and motor cortex.) Contains nuclei for many cranial nerves, contains ascending and descending fibers, contains 4 colliculi -2 superior and 2 inferior, these mediate auditory and visual information including reflexes- so the system is not overloaded with too much stimuli.

Medulla

-The first location where the spinal cord meets the brain. Lowest part of the brainstem.

-Contains ascending and descending pathways, contains cell bodies of many cranial nerves.

- Inferior cerebellar peduncles connect medulla to the cerebellum. Mostly sensorimotor signals from body are sent to cerebellum here. Pyramidal tract (direct activation pathway) passes through the medulla. Major pathway connecting brain and muscle. Include corticobulbar tracts (leading to cranial nerves) and corticospinal tracts (leading to spinal nerves) Major landmark of the medulla are the pyramids (pyramidal decussation.)

Basal ganglia

Plays a large role in automatic movement and motor learning. Modulates cortical movement commands; regulates muscle tone, adjusts associated movements (arm swing, facial expression), suppresses extraneous movements, facilitates wanted/voluntary movements, and deals with mood and personality. Motor relay and integrating system, most motor pathways run through here.

Hypothalamus

Lies just below the thalamus. Regulates sensations and emotional behavior (temperature, sexual behavior, sleep-wake cycles, emotional expression.) It has connection to higher level CNS function as well as to the ANS.

Pons

Above the medulla; looks like a bulge in the brainstem. Middle cerebellar peduncles- connect pons with cerebellum. Signals from motor cortex sent to cerebellum here. Contains nuclei for many cranial nerves, contains ascending and descending fibers, contains descending corticospinal fibers (pyramidal tract).

Pyramidal decussation

The crossover of the corticospinal tract at the level of the medulla.

Wernicke’s area

language comprehension and auditory processing

Broca’s area

language production

Primary motor cortex

pre-central gyrus- main motor area

Primary sensory cortex

post-central gyrus- main sensory area,

Primary auditory cortex

On heschl’s gyrus- medial surface of superior temporal gyrus

Primary visual cortex

Most posterior occipital gyrus- main visual processing area

What are the functions of the Frontal Lobe

Motor planning and cognition

What are the functions of the Parietal Lobe

Dealing with processing sensory information

What are the functions of the Temporal Lobe

Auditory language formulation, and cognition.

What are the functions of the Occipital Lobe

Visual processing

Afferent vs Efferent

Afferent is when a neuron that transmits information to the CNS from the periphery; sensory. Whereas Efferent is when a neuron that transmits information away from CNS toward the periphery; motor.

A cortical lesion to the motor cortex results in

Generally minor effects to jaw movement, velopharyngeal, laryngeal, and breathing functions for speech.

Ascending (Sensory) Spinal Cord Tracts

-Pain and temperature

-General Diffuse Touch

Touch, proprioception, kinesthesia

Pain and temperature

(cross at level input to spinal cord) Damage to one side of the spinal cord will lead to loss of pain and temperature sensation below the injured spot, contralateral

General Diffuse Touch

(cross at level input to spinal cord) Travels to brain via lateral fasciculus (anterior spinothalamic tract- near pain pathway). Damage to one side of the spinal cord will lead to loss of diffuse touch sensation below the injured spot contralateral to injury side.

Touch, proprioception, kinesthesia

(crosses in the brainstem) Includes pressure, vibration , and muscle and tendon stretch sensations, knowledge of spatial position of body parts, and awareness of limb movement

Dendrites

Multiple extensions or processes from the cell body. These extensions collect and transmit electrical impulses toward the cell body.

Cell Body

Surrounded by a membrane through which nutrients enter and wastes can be shed

Axon

an extension from the cell body that transmits impulses away from the cell bod

Myelin

Fatty coating on the axon- speeds neural transmission

Axon Terminals

The bulbous endings of the axons

What happens to the motor and sensory functions if half of the spinal cord is cut?

Loss of motor abilities (paralysis) below level of damage on the ipsilateral side. Loss of discriminative touch, proprioception, and kinesthesia below level of damage on the ipsilateral side. Loss of pain and temperature sensation below level of damage on the contralateral side. Loss of g general touch sensation below level of damage on the contralateral side.

What happens to the motor and sensory functions if the spinal cord is cut completely?

Loss of motor abilities on both sides below the level of damage. And Loss of all sensation on both sides below level of damage.

Gyrus

Ridge

Sulcus

Depression

Fissure

Deep depression

Longitudinal Fissure

Serperates the 2 hemispheres

Central Fissure

AKA Central Sulcus or Fissure of Rolando; serperates the frontal part of each hemisphere from the remainder.

Lateral Fissure

AKA Lateral sulcus or Sylvian Fissure; Separates the temporal lobe from the rest of the hemisphere (like the thumb on the mitten.)

Parieto-occipital fissure

Imaginary line that separates occipital lobe from the rest- anatomical referent= occipital notch.

Function of Circle of Willis?

It serves as a safety valve, allows blood flow to continue to reach the brain even if there is a problem with blood flow from one of the major arteries supplying blood to the brain.

Temporal Gyri

Wernicke’s area is the posterior superior temporal gyrus- associated with language understanding and comprehension; auditory processing and memory.

Supramarginal Gyrus

Curves around end of lateral sulcus; important for writing- symbolic integration; body imaging, math & language, phonological processing.

Angular Gyrus

Curves around end of superior temporal gyrus- integration of visual lateral, reading & writing. Important for reading , word finding, L/R orientation, arithmetic , complex syntax and writing.

What are the three cerebral arteries and what areas of brain do they supply?

Anterior Cerebral Artery (ACA): superior and medial cortex surface, frontal pole.

Middle Cerebral Artery (MCA): Lateral surface of the brain; most commonly affected by CVA

Posterior Cerebral Artery (PCA): Posterior brain, occipital pole.

Thrombus

A blood clot on wall of artery

Transient Ischemic Attack (TIA)

A “little stroke” due to a temporary disruption of blood circulation to the brain where symptoms dissipate within minutes/hours. Sometimes precedes a thrombotic stroke. Last <24hr, symptoms do not truly resolve, results vary based on location of damage.

Embolus

A blood clot that breaks free from a thrombus and enters the blood stream; travels within arteries until it gets a constriction of a turn where it lodges, disrupting blood flow. MCA is most common site for embolic strokes, typically happens suddenly with little to no warning.

Arteriovenous Malformation

Congenital tangled mass of arteries and veins in the brain. Grows like a tumor. Can sometimes hemorrhage. Can cause increased intracranial pressure- diffuse effects.

What is the striatum?

Refers to caudate and putamen

What is a dermatome?

An area of skin in which sensory nerves derive from a single spinal nerve root.

What do the 4 colliculi (superior and inferior) in the midbrain do?

They mediate auditory and visual information including reflexes - so the system is not overloaded with too much stimulus.

What does the indirect Activation Pathway do?

helps to prevent unwanted muscle contractions from competing with voluntary movements.

Organization of the spinal cord (ventral vs dorsal horn)

Lowest level of the CNS. Extends from base of skull to lower back, 1cm in diameter, protected by the vertebrae, gray matter inside, white matter outside. Posterior (dorsal) horns and anterior (ventral) horns.

Which horn receives sensory information?

Dorsal (posterior) horns

Which horn sends motor information?

Ventral (anterior) horns