Module 2: The Central Nervous System Flashcards
In general, what does the afferent division of the PNS do?
Carry sensory information from the periphery to the CNS
In general, what does the efferent division do?
Sends instructions back to the periphery from the CNS
Describe the structure and function of afferent neurons
- Found in the PNS
- Peripehral ending has a sensory receptor
Describe the structure and function of interneurons
- Found only in the CNS
- Make up 99% of neurons
- Are “connector” neurons that lie between afferent and efferent neurons
- Play a role in creating neural circuits for integrating responses to peripheral information
Play a role in higher brain functions
Describe the structure and function of efferent neurons
- Cell bodies lie within CNS where they receive presynaptic inputs
- The efferent axon lies mainly outside the CNS
Describe glial cells
- Do not initiate action potentials
- Use chemical signals to communicate with other glial cells and neurons
- Form the connective tissue of the brain
- Modulate some neuronal activities
- Plays a role in learning/memory
- Most numerous cells in CNS
What are the 3 meninges?
Dura mater, Arachnoid mater, pia mater
Describe the dura mater
- Outermost membrane
- Tough and durable
- Always in contact with skull bone except where they separate to create the dural sinsuses
What is the dural sinuses? What occurs in there?
- Space between the dura mater and skull bone. Venous blood from the brain drains into these sinuses to be returned to the heat. Cerebral spinal fluid also sometimes drain into here
Describe the arachnoid mater
- Middle meninges
- More delicate than dura mater
- Highly vascularized
What is the arachnoid granulation villi
Projection of the arachnoid mater through the dura and into the dual sinuses that allows transfer of cerebrospinal fluid from subarachnoid space to cross the villi into the blood of the sinuses
Describe the pia mater
- Intermost membrane
- Highly vascularized
- Tightly adhered to surface of brain and spinal cord
- In some areas, dips into brain to bring blood supply to the ependymal cells lining the ventricles
What are the functions of Cerebrospinal fluid (CSF)? Where is it located?
- Protects brain by acting as a shock-absorber
- Brain is suspended in it
- Located within the subarachnoid space (between arachnoid and pia mater)
- Aids in transfer of materials between blood and neuronal tissues
- Influences the composition of the brain’s interstitial fluids
- CSF is replaced more than 3x a day
The meninges cover and protect only the brain (T/F)?
False! They cover the spinal cord too
What is grey matter?
Neuronal cell bodies, short interneurons, and glial cells
- Also contain a central canal filled with CSF
What is a “horn”?
Grey matter. Each half of grey matter is separated into regions called ‘horns’
What is white matter?
Bundles of nerve fibres (axons)
- Each bundle is connected to a specific region of the brain to transmit info from the brain to the periphery/from the periphery to the brain
What does “ascending” and “descending” tracts refer to?
White matter
the __ horn contains cell bodies of efferent motor neurons
ventral
the __ horn contains cell bodies of autonomic efferent fibers
lateral
The cell bodies for afferent nerves located outside the spinal cord are called what?
Dorsal root ganglia
the dorsal root contains __ input
afferent
the ventral root contains ___ output
efferent
What are nerve fassicles?
Bundles of myelinated/unmyelinated axons in connective tissues and blood vessels
How many cervical nerves are there in the spine? Where do they emerge from?
- 8 pairs
- Emerge from neck
How many thoracic nerves are there? Where do they emerge from?
- 12 pairs
- Emerge from chest
How many lumbar nerves are there? Where do they emerge from?
- 5 pairs
- From abdomen
How many sacral nerves are there? Where do they emerge from?
- 5 pairs
- From pelvis
How many coccygeal nerves are there? Where do they emerge from?
- 1 pair
- From coccyx (tailbone)
What are the two principle functions of the spinal cord?
- Being the conduit for transmitting information between the brain and the periphery
- Integrating certain afferent inputs and efferent outputs that bypass the brain itself