Section 1 Flashcards
What does the CNS consist of?
The brain and the spinal cord
What are the complex functions that neurons within the CNS perform?
- Subconscious neuronal regulation of your internal environment
- Emotions
- Voluntary control of movement
- Perception
- Higher cognitive functions such as learning and memory
How do the CNS and the PNS work together?
The afferent division of the PNS carries sensory information from the periphery to the CNS where it is processed.
The CNS can then send necessary instructions back to the periphery through the efferent division.
What can the efferent division of the PNS be divided into?
The somatic and autonomic nervous systems
What are the three functional classifications of neuronal cells? (AFFERENT VS INTER VS EFFERENT NEURONS)
Afferent neurons:
- Mostly in PNS
- Different structure than the other neuronal cells
- Send info to CNS
- Responding to a stimuli, the receptor generates an action potential
- it is transmitted down the afferent fibre to the nerve cell body
- then transmitted down the shorter central axon which ends in spinal cord
- Cell body lacks dendrites
Interneurons:
- Most common type (99%)
- All in CNS
- “connector neurons” (connect afferent and efferent)
- These connections, known as neural circuits, are crucial for making sense of information from the world around us (peripheral information)
- Help with learning and decisions (not fully understood role)
Efferent neurons:
- Cell bodies lie within the CNS where they receive converging presynaptic inputs (inputs from different sources coming together).
- When these integrated inputs (combined information) initiate an action potential, it travels down the efferent fiber to the effector organ (the part of the body that needs to do something).
- The efferent fiber mainly lies outside the CNS
What are glial cells?
- Non-neuronal cells in the CNS and PNS
- They do not initiate or propagate action potentials
- They use chemical signals to communicate between other glial cells and neurons
- They form the connective tissue of the brain and they help support it
- They also maintain homeostatic control of the extracellular environment around the neurons
- They have been shown to modulate some neuronal activities and play a role in learning and memory
What are examples of glial cells in the body?
Macroglia (oligodendrocytes, ependymal cells, astrocytes) and microglia
What are oligodendrocytes?
Non neuronal (glial) cells in the CNS.
- form myelin sheaths that surround some neuronal axons in the CNS
- they allow for faster neuronal signalling
- the short extensions of these cells can myelinate multiple segments of an axon of the same neuron or of multiple neurons
What are Schwann cells?
Non neuronal (glial) cells in the PNS.
- myelin-producing
- allow for faster neuronal signalling
- one Schwann cell can only myelinate one segment of an axon of a single neuron
What are ependymal cells?
Non neuronal (glial) cells in the CNS.
- line the ventricles of the brain and central canal of the spinal cord (which are connected)
- they are ciliated
- they produce cerebrospinal fluid (CSF) which circulates through the ventricular system and around the brain
- the cilia function to help keep the CSF flowing through the ventricles and the central canal
What are astrocytes?
Holding Neurons in Place: They form the primary connective tissue, making sure neurons stay where they should be in the brain and spinal cord.
Making the Brain’s Shield: They help create a protective barrier around blood vessels in the brain. This barrier, called the blood-brain barrier, keeps harmful stuff out of the brain.
Fixing Brain and Spinal Cord Injuries: When there’s damage in the brain or spinal cord, astrocytes help with the healing process.
Stopping Neuron Chatter: They help calm down the chatter between neurons by taking away extra signaling chemicals (neurotransmitters).
Building and Changing Connections: Astrocytes help neurons talk to each other better by building connections between them (synapses) and adjusting how they communicate (synaptic transmission).
Keeping Things Balanced: They manage the levels of potassium (K+) around neurons. If there’s too much K+, it can make neurons more excitable, so astrocytes keep it in check.
What are microglia?
- Non-neuronal cells that are a type of immune cell found within the CNS.
- They are a bit like the brain’s own immune system, found exclusively in the brain and spinal cord (CNS).
- They have two modes of operation: restful (inactive) and alert (active).
In their resting state, microglia provide support to brain cells by producing nerve growth factors and other substances that help neurons and other brain cells thrive.
However, when microglia detect trouble, such as signs of inflammation, plaques, cell damage, or other issues, they become activated and rush to the affected area. There, they can perform several critical tasks:
- Engage in phagocytosis, which is like gobbling up foreign particles (similar to garbage collection).
- Help dampen inflammation, acting as firefighters in the brain.
- Sometimes, they release cytotoxic (harmful) chemicals, which can inadvertently harm healthy brain cells.
It’s essential to note that, due to the protective blood-brain barrier, new microglia can’t enter the CNS from outside. So, during times of need, activated microglia can multiply to replenish their numbers.
Nevertheless, when they become overly active, they might unintentionally harm healthy brain cells, potentially contributing to conditions like stroke, multiple sclerosis, or dementia.
True or false: Non-neuronal cells are also called glial cells.
True.
What is the word “glia” Greek for?
Glue
___________ produce the myelin sheath that surrounds axons in the CNS.
Oligodendrocytes
