Anatomy - NS overview, SC, Neurons, Flashcards
5 Primary Lobes & main function
- Frontal - M1, memory (immediate & STM), personality & emotion
- Parietal - sensory, speech (wernicke’s area)
- Occipital - vision
- Temporal - auditory & memory (facts & events/LTM)
- Limbic
Central Sulcus
divides the frontal & parietal lobe
Parietal-occiptal sulcus
divides parietal & occipital lobes
Lateral sulcus
divides the temporal & frontal lobe
Corpus callosum
main white fiber tracts that connect the R and L hemispheres
Cerebral aqueducts
CSF flow that helps cushion the brain
Falx cerebri and Tentorum cerebelli
Falx cerebri: dura mater projections that seperate the R/L hemispheres
Tentorum cerebelli: separates the occipital lobe from the cerebellum
Gyri vs. Sulci
Gyri - rounded elevations of the cerebral hemispheres
Sulci - grooves
Gray matter
cell bodies & terminal ends of axons that synapse w/ cell bodies that are not myelinated
–> located in horns of SC or outer part of cerebral cortex edge
White matter
myelinated axons
- -> surrounds the horns in the SC
- -> ALL axons travel through the internal capsule (which is why it is so detrimental if there is an injury here)
Four components of a Neuron
- functions
- Dendrite - finger like projections that RECEIVE information
- Axon - single projection from cell body that carries OUTPUT information to presynaptic terminal
- Presynaptic terminal - @ end of axon - it transmits info to other cells by RELEASING NT’s
- Soma - cell body - PRODUCES NT’s and other cellular functions
Bipolar vs. Multipolar neuron
-pseudounipolar - subclass
Groups of neurons classified by number of processes that directly arise from cell body
- Bipolar - two primary processes (dendritic root & axon)
- Pseudounipolar: subclass of bipolar - single projection that splits into two axons (peripheral and central)
* * Most sensory neurons are psuedounipolar - Multipolar - multiple dendrites, single axon
- MOST COMMON type
- motor neurons, interneurons, Purkinje cells
Membrane Channels in neurons (2)
+3 subgroups
- Leak channel - diffusion of ions from HIGH to LOW concentration - no energy required
- Gated channels - open in response to stimulus and closed when removed - energy required
- -> Ligand gated = open to due NT’s binding to receptor
- -> Modality gated = open due to SENSORY info
- -> Voltage gated = open due to ELECTRICAL potential
Resting Membrane Potentials of Neurons
- maintained by
-70 mV (no net flow of ions)
Maintained by: Na-K pump
3 Na OUT and 2 K IN - passive diffusion of these ions to keep at -70
Hyperpolarization vs. Depolarization
change in resting membrane potential
Hyperpolarization = inhibitory
- becomes more negative, lack of transmission or increased difficulty
Depolarization = excitatory
- less negative, transmission of info and NT released, can begin action potential
Local Potential
- what is it
- what produces it
- how is it summed
initial change in membrane potential that only spreads a short distance
–> produced by ligand (NT) or modality (SENSORY) gated channels
Can be excitatory (EPSP) or inhibitory (IPSP)
Can be summed spatially (multiple neurons create potentials at the same time) or temporally (same neuron stimulating over time) to reach threshold for AP
Action Potential
- what is it
- what happens
- RMP restored by?
larger change in membrane potential (threshold stimulus change in 15mV) that travels along length of axons
–> produced by voltage gated channels which causes release of NT
“all or none response”
Na channels open causing Na to rapidly flow into cell (depolarization - less negative) –> Na channels close –> K channels open (hyperpolarization - more negative - causing refractory period)
RMP restored by leak channels & Na-K pump
Neuronal Interactions
- convergence vs. divergence
Convergence - multiple inputs from several neurons terminating on a single neuron
Divergence - single neuron branching out and synapsing on multiple neurons
Glial Cells - function
provide structure to the brain
transmit information
neural development
repair following brain damage and clean up debris
Types of Glial cells (2)
- Macroglia
- Astrocytes: structure, absorb NT’s, blood brain barrier, recovery from injury
- Oligodendrycytes: produce myelin in CNS
- Schwann cells: produce myelin in PNS - Microglia
- phagocytes: clean up debris (TBI, stroke)
Neural Synaptic Transmission between pre and post synaptic terminals
- AP reaches pre-synaptic terminal
- Ca enters pre-synaptic terminal
- Vesicles move toward cleft to release
- Pre-syn terminal releases NT’s into cleft
- NT’s bind to receptors on post-synaptic terminal
- Ions enter post-synaptic terminal and AP is produced and info is transmitted
Neurotransmitters
- presynaptic influence
- receptors (direct vs. indirect)
Presynaptic faciliation - increased NT’s
“” inhibition = decreased NT’s released
NT’s must bind to a receptor to have an effect!
- DIRECT: ligand-gated channels (can produce local potentials)
- INDIRECT: G-protein - indirectly opens ion channels or causes a cascade of intracellular events through a second messenger
Acetylcholine
Important NT for muscle contraction in the PNS
Glutamate
primary excitatory NT in CNS
Glycine & GABA
GABA = gamma aminobutyric acid
primary inhibitory NT’s in CNS
Dopamine
releases noreepineprhine, serotonin, histamine
Peptides
important for pain perception and pain modulation
including Substance P, endorphins and enkephalins
Neural Stem cells
- what are they
- where are they found
- role
- where can you obtain them besides the brain?
undifferentiated precursors to both neurons and glial cells
Found in:
- subgranular zone of the hippocampus
- subventricular zone of the lateral ventricle wall
ROLE:
- healthy adult - form memories, learn new tasks
- injury/disease - treat ALS, MS, TBI, stroke
Umbilical cord & bone marrow
These are important b/c mature neurons CANNOT reproduce
Spinal Cord Anatomy Overview
- ends?
- special terms
Continuous w/ medulla (brainstem)
Ends @ L1-L2 IV space
filum terminale (connects the end of the cord to the coccyx)
Cauda equina - L2-S5 nerve roots @ end of SC
Spinal Nerves Overview
- how many
- exit?
- formed by?
31 pairs - 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
C1-C7 exit ABOVE corresponding vertebra
C8 and below exit BELOW corresponding vertebra
formed by dorsal and ventral root
Dorsal Horn
sensory information
- endings of peripheral sensory neurons, interneurons and cell bodies of tracts
Lateral Horn
preganglionic cell bodies of the SNS
Only located at T1-L2
Ventral Horn
motor information
- cell bodies of LMN (alpha motor neuron)
Dorsal column
sensory tracts, specifically discriminative touch and proprioception
Lateral column
sensory and motor tracts
Anterior column
Motor tracts - specifically postural regulation
Anterior white commisure
white fiber pathways that connect the L and R SC
