CNS-I Flashcards
Astrocytes
o Acts as metabolic buffers and detoxifiers within the brain
o Modulate how neurons communicate
Oligodendrocytes
o Produce a fatty substance called myelin which is wrapped around axons as layer of insulation (increases conduction)
Ependymal cells
o Line the spinal cord and ventricles of the brain
o involved in producing CSF
Microglia
o Resident macrophages (involved in neuro-inflammation)
Sensory information enters the CNS through peripheral nerves and is conducted immediately to:
o The spinal cord at all levels o Medulla, pons and mesencephalon o The cerebellum o The thalamus o Areas of the cerebral cortex
The most important role of the nervous system is to
control the various bodily activities
The nervous system controls various bodily activities through three mechanisms
o Contraction of skeletal muscles through out the body
o Contraction of smooth muscles in the internal organs
o Secretion of active chemical substances by both exocrine and endocrine glands
Muscle glands are known as the
effectors
What sends signals to control the Spinal cord level ?
what responses does the spinal cord level produce?
o The upper levels of the nervous system send signals to the control centers of the cord
→ Movement, reflexes -like when you touch a hot stove
Lower Brain or Subcortical Level function??
Its composed of?
o Subconscious activities of the body are controlled in the lower areas of the brain
→ The medulla, pons, hypothalamus, thalamus, cerebellum, and basal ganglia
Higher Brain or Cortical Level
o Without the cerebral cortex, the functions of the lower brain’s centers are not often accurate
o The cerebral cortex cannot function by itself
Ascending Reticular Activating System (ARAS)
o In the brainstem from the medulla to the diencephalon
o Relays innervation from the environment stimuli to the thalamus and then to the cerebral cortex (midbrain?)
Functions of the cerebral cortex
o Thinking, learning, and remembering
Functions of the Thalamus
o Interprets certain sensory messages such as those of pain, temperature, and pressure
Functions of the Hypothalamus
Controls various homeostatic functions – body temp, respiration, and heartbeat
Functions of the Cerebellum
Contributes to muscle tone, posture, and balance
Functions of the Brain Stem
o Regulates heartbeat and breathing
→ This is why its instant death if your brainstem is injured
o Plays a role in consciousness
CSF production
o By the choroid plexus of each ventricle
→ choroid composed of Ependymal cells
CSF functions
o Acting as a cushion or “shock absorber”
o Deliver nutrients to the brain and removing waste
o Flow between the cranium and spine, compensate for changes in intracranial blood volume
Blood-brain barrier (BBB):
A series of high-resistance, tight junctions between endothelial cells as well as astrocytes with processes on capillary walls → charged big molecules can’t cross
Blood-CSF barrier:
Formed by tight junctions between choroid epithelial cells
Both the BBB and the blood-CSF barrier
o Endothelial cells and astrocytes that make up the BBB and cells forming the blood-CSF barrier can produce cytokines
o Astrocytes can act as antigen-presenting cells that curb the immunologic response to CNS infections
• Wallerian degeneration in PNS (spinal nerves are part of the CNS)
o Occurs in the axon distal to the site of a cut
A. Normal nerve innervating skeletal muscle
B. The nerve has been transected and Wallerian degeneration has begun (corresponding atrophy in the muscle)
C. Proximal nerve terminals send sprouts toward the Schwann cells
D. Some of the sprouts make it into tubes and re-innervate the muscle
• Wallerian degeneration in CNS
o Damage occurs to Spinal cord axons
o Macrophages (purple) enter to clear the debris and astrocytes begin to enlarge and proliferate
o A glial scar is formed blocking axonal growth