A/P Unit 2 Flashcards
What are the 3 classifications of neuron fibers?
Types A, B and C
Describe the differences between the 3 types of neuron fibers?
A is myelinated, B is lightly myelinated, C is non-myelinated. Type A is the largest, C is the smallest.
What are the 4 sub categories of type A fibers?
A-Alpha fibers - The largest, fastest and myelinated
A-Beta fibers - A little smaller than A-alpha
A-Gamma fibers - smaller than A-beta
A-Delta - smallest myelinated neurons
What type of neurons connect to skeletal muscles?
A-Alpha
What type of fibers are generally pain fibers? What makes up the smaller percentage?
A-Delta as the primary, C-fibers as the smaller percentage
What are the advantages of myelinazation?
Faster signal conductance, lower metabolic demands, greater ability to survive times of ischemia
What are the maintenance cells in the CNS? The PNS?
CNS - Oligodendrocytes
PNS - Schwann cells
What is the part of the neuron that functions as the “brakes.” What binds to it to elicit this response?
The axon hillock, and usually GABA
Why does alcohol withdrawal cause seizures?
Because alcohol functions as a neuronal suppressant. Because the body as adapted to this, it no longer makes much GABA. Without GABA, if alcohol is abruptly taken away, there is nothing to suppress neuronal excitability and the whole system can go haywire (seizures).
Describe Excitatory and Inhibitory post-synaptic potential
Most dendrite connections are excitatory connections, so another neuron is communicating with the receiving one to try and create an AP. If enough are communicating, they can cause depolarization. Inhibitory are the opposite; when they communicate, they are trying to repolarize or make the neuron more negative.
What type of neuron is a decision making neuron?
Multi-polar
How does a decision making neuron make a decision?
It makes decisions based on the charge difference created by neurons sending messages to the decision making neuron.
What is pre-synaptic potential?
This is when a neurotransmitter released by the communicating neuron (not the decision maker) comes back to the communicating neuron and binds to stop further neurotransmitter release
What is post-synaptic potential?
Classic neuronal communication; the communicator is sending a message through the synapse to the decision making neuron.
What would make a neuron more + and -?
More + (or less -) open Na or Ca channels, close K channels.
More - (less +) open Cl or K channels, close Na channels
What are the 4 types of glial cells?
Astrocytes, ependymal cells, oligodendrocytes, microglia
What do astrocytes do?
Star like appearance, goal is to maintain constant conditions in the nervous system. Can buffer CSF. End feet support the BBB.
Why does a drop in Na increase ICP?
Because the BBB is mostly impermeable to salt, so a difference in concentration gradient can drive water into the brain.
What do Oligodendrocytes/Schwann cells do?
Maintain the myelin of the CNS/PNS
What do ependymal cells do? Where are they located?
Produce CSF, and using cilia act as a secondary circulatory system (pump) to send CSF throughout the CNS system. They hang out in the 3rd/4th ventricles and the lateral ventricles.
What do microglia do?
They act as scavengers of the CNS, break things down, almost function as a mini-immune system
Where do most brain cancers originate from?
Glial cells, because of their ability to reproduce themselves. Neurons (for the most part) in the CNS can’t regenerate/make copies of themselves.
What are the basic neuron types?
Multi-polar, Pseudo-unipolar and Bipolar
Describe a multi-polar neuron, pseudo-unipolar and bipolar neuron
Multi-polar - Numerous dendrites, 1 myelinated axon. Decision making neuron.
Pseudo-unipolar - Long axon with soma off to the side. Typical setup for sensory neurons. Generally occur in a cluster (ganglia in the PNS, nuclei in the CNS)
Bipolar - one single axon, one dendrite. Reserved for special sense such as retina and photoreceptors
Describe the term “somatic”
Things we are aware of, sensations such as pain or pressure. This is also allows us to use our skeletal muscle to move.
What type of nerve ending do pain receptors have?
Free nerve endings
Describe how Pacinian and Meissner’s corpuscles work
Imagine a circle, when pressure is applied it flattens out. When flattened out, the sodium channels are “pulled wider” to allow Na to rush in. This increases the rate of AP firing and tells the CNS that pressure is occurring at this site.
Describe how baroreceptors work
Similarly to pressure sensors, if pressure increases/decreases in the Aorta or carotid, this will increase/decrease the firing rate of APs to let the CNS know about the change in pressure. If pressure remains high/low, over a 48 hour period the the baroreceptors can become adapted to this change, and make it the new baseline.
What type of nerve ending exhibits reverse adaptation? Describe reverse adaptation?
Free nerve endings. If you experience pain, and keep experiencing it, you will become more sensitive to it, or sensitize.
Describe how tactile hairs work
Think a cats whiskers. Sensors are wrapped around it that respond to an external stimulus, such as whiskers rubbing against a door, or a fly landing on my arm.
Describe how the golgi tendon apparatus works
Located in the tendons of muscles. Tells the CNS if the tendons are under strain, if strain is high, it will protect the tendon by relaxing the muscles around the tendon.
Describe how the muscle spindle stretch sensor works
Fibers are wound around skeletal muscle that are distorted when muscle contracts. This distortion creates APs to confirm to the CNS that the muscles are doing what they have been ordered to do. Simplified; it sense the tension in the muscles.
What is rostral and caudal?
Think bird, beak and feather (directionality). The forward and front is the beak (rostral) and the lower and to the rear is caudal.
What is the telencephalon?
The out part of the brain, the cerebral cortex.
What is the diencephalon?
The deep inner structures of the brain, mainly the thalami (thalamus, hypothalamus, epithalamus).
What do the thalami help control?
Body temp, infection control
What is the mesencephalon?
The midbrain, or top of the brainstem
What are the component parts of the brainstem?
Midbrain, pons, medulla oblongata (in order).
Where does higher order thinking occur?
Cerebral cortex
Where do automatic functions occur in the brain?
The diencephalon and brain stem
What are the 4 lobes?
Frontal, parietal, occipital, and temporal
What is the primary function of the frontal lobe?
Conscious thinking, personality, decision making
Where is the location of the motor cortex?
Back of the frontal lobe in front of the cerebral sulcus
What is the primary function of the parietal lobe?
This is where sensations/sensory information is processed.
What separates the frontal and parietal lobes?
The central sulcus, this is a major landmark of the brain
What is the primary function of the occipital lobe?
Processing visual input, thinking about what we see. No good anatomical marker to differentiate the parietal from occipital lobes.
What is the primary function of the temporal lobe?
Handles auditory sensation, some limbic function as well (limbic is dealing with emotions)
What is the landmark that separates the temporal and occipital lobes?
The temporo-lateral fissure. Also called the temporal fissure.
What separates the brain hemispheres?
The longitudinal fissure
What allows the hemispheres to communicate with each other?
The corpus callosum
Describe the location of the olfactory bulbs
One for each hemisphere, runs on the inferior side of the frontal lobe. Neurons extend out from here, one for each nostril
What is the other name for the pituitary gland? Describe its location and constituent parts.
The hypophysis, and inferior part of the brain, near the back of the frontal lobe. Made of the anterior and posterior glands (hypophysis and neurohypophysis)
Describe the location of the optic nerves
Start next to the anterior mesencephalon (brain stem) and in front of the hypophysis.
Where does vision get routed back to the occipital lobe?
The optic chiasm, which is very close to the origin of the optic nerves, and curls around the hypophysis
Describe the anatomical location of the cerebellum
Tail end at the bottom, meaning the caudal position.
What is the anatomical location of the motor cortex? And its basic function?
Pre-central gyrus, and to send efferent signals to the skeletal muscle
What function does the post-central gyrus perform?
It is the sensory portion of the parietal lobe
Describe Broca’s location and function
Frontal lobe, and is involved with word formation and thought processing about speech
Describe Wernicke’s location and function
Language comprehension and temporal lobe
What is the pre-central gyrus? The post-central gyrus?
The motor cortex (frontal lobe location) and sensory processing (parietal lobe)
Describe the limbic system location and function
In the temporal lobe, and governs response to pain, general emotions, depression
Where are the cell bodies concentrated in the spinal cord?
The grey matter
Where are reflexes housed in the spinal cord?
Grey matter
Describe the 3d traveling orientation of information going through the spinal cord
It comes in the horizontal plane to the ventral/dorsal horns, and the vertical plane via the spinal columns
Basic function of the grey matter
Decision making
Basic function of white matter
Signal transduction (transferring information)
Describe the 2 major spine landmarks
The anterior median fissure (front) and the posterior median fissure (back)
What is the meeting point for the left/right sides of the column for white and grey matter (in that order)?
The anterior white commissure, and the lamina ten (lamina X)
What is the small opening in the lamina X? What is its function?
The central canal, it is lined with ciliated cells to help push/pump CSF down the cord
Describe how to identify the horns
First identify the anterior median fissure. Generally, the larger horns will be the ventral horns, and closer to the fissure, then then horns above them (and generally smaller) will be the dorsal horns
Describe the lateral horns
Small arrowhead shaped projections halfway between the ventral and dorsal horns. Not always present.
Describe the direction the horns send information
The ventral horns are taking messages from the CNS to the periphery, making it an efferent pathway. The dorsal horns are taking information from the periphery and sending it to the CNS (this could just be the spinal cord or the brain), making it an afferent pathway.
Describe the short version of the type of information handled by each of the horns
Sensory information is handled by in the back by the dorsal horns, motor information in the front by the ventral horns
What would occur with ischemia to the anterior spinal cord?
This would affect the ventral horns, so motor movement. Maybe even paralysis
What would occur with ischemia to the posterior spinal cord?
This would affect the dorsal horns, so sensory deficiences
What are the small superficial arteries in the spinal cord called?
Coronal arteries
Describe basic location of the 3 main spinal cord arteries
1 in the anterior median fissure, 2 on the back adjacent to the posterior median fissure
What is the name of the blood vessels that go into the spinal cord?
Sulcal arteries/veins
Describe the major veins of the spinal cord
The anterior spinal vein runs in the anterior median fissure, the other runs in the posterior median fissure
Describe the progression of nerve fibers coming in/out of the spinal cord
Rootlet -> root -> nerve -> ganglion
What type of information would posterior rootlets be handling?
Sensory information going to the dorsal horns
What type of information would anterior rootlets be handling?
Motor information coming from the ventral horns going out to the muscle
Where do the sympathetic ganglion go?
They run parallel to the cord/spine
Where are the ascending spinal columns/tracts? Where is this information going?
The posterior spine (in between the dorsal horns) and the antero-lateral cord (the left/right sides of the outer cord) and is information going up to the brain
What type of information ascends in the posterior column?
Basic senses
What type of information ascends the antero-lateral columns?
Pain
Where are the descending columns located?
In between the ventral/dorsal horns, slightly above where you could potentially find the lateral horns and more medial than the lateral ascending columns, and the anterior spine
Describe C-spinal nerve location, number and nomenclature
8 pairs, 16 total. C1 nerve comes out on top of its own vertebrae, C2 - 8 come out just below the prior vertebrae. So, nerve C2 comes out on the bottom of C1, this continues for nerves C2 - 8. IMPORTANT there are 7 cervical vertebrae, C1 nerve is on top of C1 vertebrae, C2 nerve comes out from the bottom of the C1 vertebrae.
Describe T-spinal nerve location, number and nomenclature
12 pairs, 24 total. They come out from the bottom of their respective vertebrae. So the T1 nerve comes out from the bottom of the T1 vertebrae, this continues through T12.
Describe L-spinal nerve location, number and nomenclature
5 pairs, 10 total. The same as T-spine nomenclature, the L1 nerves come out from the bottom of the L1 vertebrae. This continues through L5.
Describe the spinal curvature from top to bottom
C spine is cervical lordosis (front curve), T-spine is kyphosis (back curve) L-spine is lordosis, sacral is kyphosis
What is abnormal side-side bending of the spine called?
Scoliosis
What is unusual forward curvature of the spine called?
Pathological kyphosis
What is unusual backward curvature of the spine called?
Pathological lordosis
What are the connection points for the vertebrae called?
The superior/inferior articular processes
What is the joint of the articular processes called?
A facet joint
Describe the basic structure of a vertebrae
A large vertebral body, an arch on the posterior side made of the pedicle (short portion) and the lamina (longer portion). The transverse processes extend laterally, the spinous process projects posteriorly, with superior and inferior articular processes extending up/down from the meeting point of the pedicle and lamina.
Where would spinal nerves exit the vertebrae?
Via the intervertebral foramen
Where would you inject steroids to help back pain?
As close to the facet joint as possible
What are the distinguishing characteristics of a cervical vertebrae?
A large vertebral foramen, bifid spinous process, holes in the transverse foramen for veins/arteries, a hollowing out above the pedicle for the nerves to leave, a large vertebral foramen, and a small vertebral body.
Where do the vertebral arteries/veins enter?
C6 transverse foramen
What arteries provide blood to the brain?
The L/R carotids and the L/R vertebral arteries
What is the name of the top 2 cervical vertebrae?
The atlas (C1) and Axis (C2)
What is unique to C1?
Anterior/posterior tubercles (instead of a body/spinous process), a facet for the dens and very large superior articular facets
What is unique to C2?
The dens, a flat superior articular facet, large spinous process, the first appearance of a bifid spinous process and the first vertebral body.
What does the dens do?
Provides structural support, and the ability to move the neck side to side
What allows the neck to bend up/down?
The connection between the occipital condyles and the atlas
What is the big hole at the base of the skull?
Foramen magnum
What connects the atlas and the occipital bone?
The atlantooccipital ligament
What gave the name for C1?
Atlas, the god who supported the weight of the world on his shoudlers
Describe the occurrence rate for bifid spinous processes in the general population
Vast majority have one for C2 - C5, 50% have one in C6, 0.3% of the population have one in C7
Describe the general trend of the vertebral foramen
Starts large at the top, and gets smaller as you go down because the cord gets progressively smaller
What are the ligaments that run the length of the spine? Which is the largest?
The anterior/posterior longitudinal ligaments, the anterior is the larger