Lecture 4: CNS Flashcards
What are the two main parts of the CNS
Brain and spinal cord
1) Are there only a few neurons in early nervous system development, or a lot?
2) What happens to those neurons?
3) Give an example
1) There is an abundance of neurons
2) Depending on environmental factors and stimulation these may be kept, enhanced, or eliminated
3) Eyes can become lazy, and when you cover a non-lazy eye, it forces the lazy eye to start working again
What are the 3 classes of neurons that make up the nervous system?
Afferent neurons
Efferent neurons
Interneurons
Describe the basic chain of neurons path
Sensory receptor picks up a signal. Afferent neuron sends signal to interneuron, which sends signal to efferent neuron, which affects the muscle
What makes up 90% of the cells in the CNS?
Glial cells
Name 4 functions of glial cells
1) Physically and metabolically support neurons
2) Maintain composition of extracellular environment
3) Modulate synaptic function
4) Also important in learning and memory
What cells maintain the composition of the extracellular environment of the CNS?
Glial cells
List the 4 types of glial cells. Which is most abundant?
1) Astrocytes: most abundant
2) Oligodendrocytes
3) Microglia
4) Ependymal cells
1) What are astrocytes shaped like?
2) Do they have a few functions, or many?
1) Star shaped (hence their name)
2) Many functions; the functions we talk about are only some
List 5 jobs of astrocytes and elaborate on them
Glue, nutrients, degrade, ions, clear:
1) Main glue (“glia”) of the CNS
-Hold neurons in their spatial orientation
2) Transferring nutrients to neurons, helping the brain repair injuries
3) Degrade neurotransmitters (to help stop a transmission)
4) Help maintain optimal ion conditions for neural excitability
5) Clearing toxic metabolic byproducts from the brain
1) What do oligodendrocytes do?
2) What are they shaped like?
1) Form insulative myelin around CNS axons
2) “Jelly roll”
What are the 2 jobs of microglia?
1) Immune cells of the CNS
2) Release nerve growth factor, helping CNS cells survive
1) What is unique about microglia?
2) What can happen if microglia are overactive?
1) Only CNS cell that can be infected by HIV, leading to AIDS-dementia
2) Will cause autoimmune damage in Alzheimer’s, MS, and other neurodegenerative diseases where nerves are damaged (causes demyelination)
1) What do ependymal cells do?
2) What is unique about them (2 things)
1) These cells form the lining of fluid-filled cavities of the CNS like ventricles
2) They’re ciliated (helps CSF flow) and can form into other glial cells after they’re injured
1) What cells are the main glue (“glia”) of the CNS?
2) What cells form insulative myelin around CNS axons?
3) What cells form the lining of fluid-filled cavities of the CNS like ventricles?
4) What is the only CNS cell that can be infected by HIV, and what does this lead to?
1) Astrocytes
2) Oligodendrocytes
3) Ependymal cells
4) Microglia; leads to AIDS-dementia
1) What cells are ciliated? Why?
2) What are the immune cells of the CNS?
3) What cells cause autoimmune damage in Alzheimer’s, MS, and other neurodegenerative diseases where nerves are damaged when they’re overactive?
1) Ependymal cells; to help CSF flow
2) Microglia
3) Microglia
1) Define neurogenesis. Where does it occur?
2) What causes it to happen?
3) What causes it to slow down?
1) Production of new neurons (in the hippocampus)
2) Increases with exercise
3) Declines with age and chronic stress
1) What misconception about neurogenesis was around until the 90s?
2) What do we believe now?
3) What is an intense area of modern medical research?
1) Until the 90s, it was believed that the adult brain doesn’t form new cells
2) That most brain regions don’t regenerate neurons, but that the hippocampus does
3) Stimulating neurogenesis
1) Do glial cells continue cell division? What about neurons?
2) Is CNS tissue durable or delicate? Can nerves be replaced?
1) Glial cells do, neurons don’t
2) CNS tissue is delicate, damaged nerves cells are not replaced (bc they don’t continue cell division)
What 4 things protect CNS tissue?
1) Cranium and vertebral column
2) Meninges
3) Cerebrospinal fluid
4) Blood-brain barrier (BBB)
What are the 3 layers of the meninges from outer to inner?
Outer: Dura Mater
Middle: Arachnoid Mater
Inner: Pia Mater
1) What does dura mater mean?
2) Describe this layer
3) What does this layer contain? What happens here?
1) “Tough mother”
2) Outermost layer; a tough, inelastic covering
3) Venous sinuses; blood from brain is returned to the heart and CSF reenters the blood
What happens in the venous sinuses of the dura mater? (2 things)
1) Blood from brain returned to the heart
2) CSF reenters the blood
1) What does arachnoid mater mean?
2) Describe this layer
3) What is its underlying space called? What is it filled with?
1) “Spiderlike mother”
2) Richly vascularized with cobweb appearance (arachnoid villi reabsorb CSF)
3) Subarachnoid space, filled with CSF
How is CSF reabsorbed from the subarachnoid space?
By villi
1) What does pia mater mean?
2) Describe this layer
3) Describe the location of this layer in relation to CNS structures
1) “Gentle mother”
2) Fragile, innermost layer; highly vascular
3) Closely adheres to CNS structures, every ridge and valley
1) What does CSF do?
2) Describe its density
3) Where is CSF found?
1) Surrounds and cushions the brain and spinal cord
2) Same density as the brain (brain floats/suspended in CSF)
3) Contained in subarachnoid space
1) Are CSF and IF the same?
2) What is the only thing that comes into contact with neurons and glial cells?
3) What is CSF important for?
1) No
2) Only interstitial fluid (IF) (not CSF or blood)
3) Material exchange to the brain
1) Describe the exchange of materials between CSF and interstitial fluid (IF)
2) Describe the exchange of materials between blood and IF
3) Describe the importance of IF
1) CSF and IF: materials exchanged freely
2) Blood and IF: limited exchange
3) IF is like the middle man between CSF and blood
1) What structure(s) produce CSF?
2) Where are the structure(s) that make CSF?
3) What are they made out of?
1) Choroid plexuses
2) Structures protruding from the ventricles
3) Pia mater
1) Where is CSF found?
2) What facilitates the flow of CSF?
3) What reabsorbs CSF? Where does it go?
1) Throughout the brain and central canal of the spinal cord
2) Ciliated ependymal cells
3) Reabsorbed by subarachnoid villi and ultimately reenters in dura mater
1) Is CSF balance a hardy process or is it delicate?
2) How much CSF do we have total? How often is the entire CSF volume replaced?
1) Delicate
2) Entire volume (125-150mL) replaced three times a day
1) What can removal of a few mLs of CSF cause? Give an example
2) What can cause CSF to accumulate? What can this lead to?
1) Can cause severe headaches (ex: spinal tap)
2) Obstruction (malformation, tumor); can lead to hydrocephalus and brain damage
What can lead to hydrocephalus and brain damage?
Accumulated CSF due to obstruction (malformation, tumor)
1) What does the blood brain barrier (BBB) do?
2) How are materials exchanged in the rest of the body?
1) Shields the brain from the blood
2) Between blood and IF only across capillary walls
1) In the body, when blood and IF exchange materials, what do they pass through?
2) Describe the flow of materials between the two
1) Single layer of endothelial cells
2) Materials flow almost freely around pores between endothelial cells
1) Describe the capillary wall cells of the brain
2) In the brain, when blood and IF exchange materials, what do they pass through?
3) True or false: Despite the BBB, the brain depends on a constant blood supply
1) Capillary wall cells have tight junctions; impermeable
2) Materials must go through the cells, not around
3) True
Why does the brain need a constant supply of blood? (2 reasons)
1) Cannot produce ATP without O2
2) Can (mostly) only use glucose for fuel production and cannot store any glucose (can also use liver ketones)
What can the brain use for fuel besides glucose?
Ketones produced by liver
1) The brain is ____% of the body’s weight
2) Receives _____% of the blood
3) Uses _____ of the O2 (brain damage after________ if not supplied)
4) Uses ______ of the glucose (brain damage after _________ if not supplied)
1) 2%
2) 15% of blood
3) 20% of the O2; 4-5 mins and brain damage starts
4) 50%; 10-15min before brain damage
1) What is the most common cause of brain damage?
2) What causes 80% of these?
1) Strokes / cerebrovascular accidents (CVAs)
2) A blood clot in a cerebral blood vessel
Describe what happens in regards to cell death during a CVA/ stroke
1) Affected area’s cells die by necrosis
2) Release glutamate which binds with nearby NMDA receptors
3) Which opens Ca+ channels and triggers apoptosis in nearby cells
How do most neurons die following a stroke?
More neurons die by apoptosis than by necrosis
The brain is about _____ pounds and has _[big number]____ neurons with a ___[bigger number]_________ synaptic connections
1) 2
2) 85 billion
3) quadrillion
What do the quadrillion synapses in the brain enable?
1) Subconsciousness
2) Emotions
3) Movement
4) Perception and proprioception
5) Cognition (thought, memory, awareness, judgment)
List the 5 parts of brain from bottom to top (least to most evolved)
1) Brain stem
2) Cerebellum
3) Forebrain
4) Diencephalon (hypothalamus + thalamus)
5) Cerebrum (basal nuclei and cerebral cortex)
What is the most evolved part of the brain, and what parts does it consist of?
1) Cerebrum
2) Basal nuclei and cerebral cortex
1) What is the oldest region of the brain?
2) What is it continuous with?
3) What does it control?
1) Brainstem
2) Continuous with spinal cord
3) Vegetative processes: breathing, circulation, digestion
What are the 3 parts of the brainstem?
Midbrain
Pons
Medulla
1) Name 3 vegetative processes
2) What is the medulla a part of?
3) What controls skilled motor tasks (like dancing)
1) Breathing, circulation, digestion
2) Brainstem
3) Cerebellum
Name 4 things the cerebellum controls
1) Maintains body position
2) Coordination of motor activity
3) Skilled motor tasks like dancing
4) Subconscious control
1) What does the hypothalamus do?
2) What does the thalamus do?
1) Hypothalamus: Homeostatic control
2) Sensory processing
1) What part of the brain is larger in advanced species?
2) What does this part of the brain look like in less advanced species? What does this cause?
1) Cerebrum
2) Less advanced mammals have smooth cortices; causes less area and less circuitry
1) What makes up 80% of the brain’s weight in humans?
2) What part of the brain controls sensory processing?
3) What controls voluntary movement?
1) Cerebrum
2) Thalamus
3) Cerebrum
What does the cerebrum control? (6 things)
1) Voluntary movement
2) Sensation
3) Thought
4) Language
5) Personality
6) Intelligence
1) What are Positron Emission Tomography (PET) scans?
2) What can they show?
1) Injection of small amounts of radioactive material which releases tiny bursts of energy that can be detected by PET equipment
2) Which parts of the brain “light up” with different tasks
What are the 4 lobes of the cerebral cortex? List what each does
1) Occipital lobes: Visual processing
2) Temporal lobes: Sound processing
3) Parietal lobes: Sensory processing
4) Frontal lobes: Voluntary movement, speech, & thought
1) What is the cerebrum divided into?
2) How are they connected?
1) 2 halves (left and right hemispheres)
2) By the corpus callosum
1) What part is an information superhighway in our brains?
2) How many neurons does it have?
1) Corpus callosum
2) It’s a band of 300 million neurons
What type of brain matter makes up the cortex?
Cortex is an outer shell of gray matter covering a core of white matter
1) What makes up the gray matter of the cortex? What can this be compared to?
2) What makes up the white matter of the cortex? Why is it white?
What can this be compared to?
1) Gray matter: cell bodies, dendrites, glial cells
-The computer
2) White matter: bundles of myelinated axons (white from lipid)
-The wires
1) True or false: The brain has complex interplay among regions
2) What is the corpus callosum?
1) True
2) A band of 300 million neurons that connects the two hemispheres of the cortex