Organization of CNS (Glendinning) Flashcards
- Describe the basic divisions of the CNS. Identify the cortex, brainstem, thalamus, and spinal cord.
Spinal Cord:
- Extends from foramen magnum to L1
- Cervical (C1-C8)
- Thoracic (T1-T12)
- Lumbar (L1-L5)
- Sacral (S1-S5)
- Coccygeal (Co1)
3 major features of the spinal cord
Identify the sensory and motor regions of the spinal cord.
Spinal cord circuits
3 major features:
- Long and short pathways
- Spinal nerves
- Grey matter
Dorsal root - sensory input/afferents
Ventral root - motor output/efferents
Spinal cord circuits:
- Reflex circuits - feedback inhibition or negative feedback (i.e. stretch reflex)
- Basic motor circuits - postural and locomotor outputs
- Sensory processing
2 major features of brainstem
Identify the 3 major areas of the brainstem.
2 major features: exiting (entering) cranial nerves and long pathways
Midbrain
Pons
Medulla oblongata
Explain the general function and list the cranial nerves associated with each region of the brainstem.
Ventral surface of brainstem:
- Most of the cranial nerves exit the ventral surface
- Corticospinal tract (major descending pathway)
MEDULLA: IX, X, XI, XII (cardiac, pulmonary) - receives info from: - Taste structures - Skin of head, heart, and lungs - Major blood vessels - Digestive system
Several nuclei (grey matter):
- Regulates body homeostasis: HR, Respiration, vasomotor tone, gastric secretions
- Related reflexes: vomiting, coughing, sneezing, swallowing, gagging
If medulla is compressed (herniations through foramen magnum) -> fatal outcome
PONS (big bridge to cerebellum): V, VI, VII, VIII (5-8) Several nuclei: - Balance - Localizing sound - Coordinating eye movements - Facial expression
Related reflexes: eye movements, jaw jerks
Large pathway into the cerebellum
MIDBRAIN (mesencephalon)
III, IV (involved with extra ocular control)
Several nuclei:
- Control orienting to sound, visual reflexes, motor control
Projections to the cortex:
- Substantia nigra, ventral tegmental area source of dopamine projections to cortical areas (movement and “reward”)
Habit formation pathways originate in midbrain
Define the reticular formation and describe its location in the brainstem.
Nuclei and neuronal circuits
- have net-like appearance
- run through core of brainstem
- many nuclei are the origin of projections to the cortex or spinal cord
Example: Caudal reticular formation includes centers that control:
- Respiratory rhythms
- BP
- Digestion
- Reflexes: facial expressions, gag, yawn, swallowing, vomiting
- All medulla
The more rostral portion modulates forebrain activity
Explain the significance of the “reticular activating system.”
Rostral projections from PONS and MIDBRAIN (pontomesencephalic)
Project directly to cortex or through thalamus to control ATTENTION, AROUSAL, SLEEP, WAKEFULNESS
Includes several neurotransmitters systems
if affected, ppl will end up in coma
Identify the thalamus and describe its general function.
What makes up the diencephalon?
Projections to the cortex = THALAMOCORTICAL RADIATIONS
Major relay station for all inputs to the cortex
examples: sensory (except olfactory), motor (e.g., cerebellum), reticular formation, limbic system
Thalamus, hypothalamus, epithalamus, sub thalamus = DIENCEPHALON
Identify the two major structures that comprise the cerebral hemispheres.
CORTEX and BASAL GANGLIA (collection of gray matter in the cerebrum - chooses and initiates motor patterns and behaviors - generates habits)
List and describe the function of each of the 6 layers of the cortex (outer surface: grey matter)
I: Molecular: synaptic contacts from other layers
II: Small pyramidal: corticocortical (PREFRONTAL ASSOCIATION CORTEX)
III: Medium pyramidal: corticocortical (PREFRONTAL ASSOCIATION CORTEX)
IV: Granular: SENSORY inputs from thalamus
V: Large pyramidal: MOTOR outputs to CNS
VI: Polymorphic: outputs to thalamus
Identify the 5 lobes of the cortex and explain the general functions located within each lobe.
Frontal: planning, organizing, controlling behavior
Parietal: sensory perception of self and world
Occipital: visual processing
Temporal: Auditory (superior), visual (middle), and memory (medial) processing
Limbic: emotional processing and memory consolidation
Explain the concept of somatotopy, retinotopy, tonotopy in primary cortices.
Primary cortices are topographically organized - sensory “fields” are represented in orderly manner within primary cortex
Somatotopy - arrangement of primary somatosensory and motor cortices
Retinotopy - arrangement in primary visual cortex
Tonotopy - arrangement in primary auditory cortex
These representations are examples of LOCALIZATION of function
Locate the regions of the cortex occupied by the limbic system.
Includes medial regions of cortex, with hippocampal formation and amygdala
Involved in processing of Long-Term memory and emotional memory –> Allocortex - 3 layers
Identify the cerebellum and describe its general function:
motor control and learning, posture, orientation, balance
3-layered cortex
enables FEEDFORWARD control (anticipate movement)
Damage to cerebellum causes ATAXIA (disordered movement)
Where is the ASSOCIATION CORTEX located and what does it do?
Located in primary auditory cortex (in Sylvian fissure)
Carries out higher-order processing (e.g., perceptions, judgments, organization, calculations, language)
