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what is the spinal cord? what does it do?
“information highway”cylinder of nervous tissue that connects the brain and the lower body
where (anatomically) is the spinal cord? how big is it?
spans from the brainstem at the foramen magnum, through the vertebral canal to the inferior margin of L1
45 cm long, 1.8cm thick & occupies ⅔ of vertebral canal
what does the spinal cord contain?
the neural routes
what are the 4 functions of the spinal cord?
- neural integration
what is conduction?
the nerve fiber bundles CONDUCT info up & down the cord, connecting the body to other parts of itself and to the brain
what is neural integration?
the spinal neurons receive input from many sources, integrate (aka combine) the information and perform some action/function
--they get info from different nerves, they combine this information from each nerve to figure out what is happening to the body and respond to it!
what is locomotion?
repetitive, coordinated contractions of several muscle groups of the limbs.
central pattern generators provides the basic motions by integrating (aka combining!) input from nerves.
examples of simple repetitive movements are WALKING!!! EATING!!!! you dont have to think about walking or the process of eating.
what are reflexes?
involuntary stereotyped responses to stimuli
---automatic responses to certain environmental stimuli for example fire... when you feel something hot like fire, you move away from it instantly without thinking.
how many PAIRS of spinal nerves are there? where do they pass through?
first pair passes between the skull and C1
the rest pass through intervertebral foramina
ONE pair of nerves in the spinal cord makes up a segment
anterior median fissure
a groove along the anterior midline of the spinal cord (a groove that basically goes right down the center from top to bottom)
deeper than posterior median sulcus
posterior median sulcus
a groove that goes down the midline of the spinal cord that's SHALLOW (this Sulcus = Shallow)
what are the regions of the spinal cord?
(same as the back :) )
in what two areas is the spinal cord a little bit thicker than everywhere else? what makes them so special?
- cervical enlargement
- --the nerves of the upper limbs come from here so it has to be thicker
- lumbar enlargement
- --the nerves of the Lower (L for lower and lumbar) and pelvic region come from here
inferior to the lumbar enlargement the cord tapers (goes from big to thinner)
means a horse's tail in latin
named that because it looks like one
a bundle of nerves that occupy the vertebral canal from L2 to S5
three fibrous connective tissue membranes that encloses the brain and spinal cord that protect them
---meningitis is the infection of this tissue and its so deadly because it's supposed to protect your brain and spinal cord
what are the 3 layers of the meninges from superficial (outside) to deep?
- Dura mater
- Arachnoid mater
- Pia mater
(Damn Angie's Pussy :P)
sheath is another word for a cover
its a loose fitting sleeve around the spinal cord formed by the dura matter
space between the dural sheath and the vertebral bones (epi= above.. above dural)
filled with blood vessels, adipose tissue & loose connective tissue
internal and butterfly shaped
contains little myelin, somas, dendrites and proximal parts of the axons of neurons
why is the gray matter important?
center of all neural integration (combination of all of the nerves signals) in the spinal cord
what does the core of the gray matter consist of?
2 posterior horns
2 anterior horns
2 lateral horns
one of each on each side
connects left and right sides of the gray matter
posterior dorsal root
carries sensory nerve fibers
posterior horns contain
sensory soma and interneurons
Posterior= Interneurons, Sensory Soma
(PISS, i know gross)
Anterior horns contain
the Large somas of the somatic motor neurons
(you got a LARGE Anterior ma ;) )
Lateral horns contain
autonomic- sympathetic motor neurons
visible from each side of T2 to L1
its external, surrounds the grey matter
contains a lot of myelin
composed of tracts
subdivisions of the columns that are made up of bundles of axons that carry signals from one part of the central nervous system to another
compose the white matter
the white matter is arranged in:
3 pairs called columns or funiculi
they are the posterior, lateral and anterior COLUMNS
(white matter has columns, grey has horns; same names)
ascending means to the top
carries SENSORY info up the spinal cord
descending means down
conducts MOTOR impulses down
crossing over of the tracts from one side of the body to the other
opposite sides of the body
same side of the body
sensory signals typically travel across how many neurons from their origin?
first order neurons
detects stimuli and transmits signals to the spinal cord or brain stem
second order neurons
continues from first order up to the gateway called the thalamus at the top of the brainstem
third order neurons
carries the signal from the thalamus to the sensory region of the cerebral cortex
carries signals from the midthoracic and lower parts of the bodies
composes from T6 down the entire posterior column
carries signals for vibration, visceral pain, deep and discriminative touch and proprioception from the lower limbs and trunk
nonvisual sense of the position and movements of the body
---eyes closed you know you're laying on the bed and you can pick up your phone without opening your eyes
joins the gracile fasciculus at the T6 level
carries the same signals from the T6 UP.
anterolateral system that carries signals for pain, temp, pressure, tickle, itch and light touches
here, the first order neurons go up to the posterior horn of the spinal cord
sensory signals arrive at the cerebral hemishphere
travels up the anterolateral system and carries pain signals from tissue injury
how do signals travel through the neurons in the spinoreticular tract?
first order neurons enter the posterior horn and immediately synapse to the second order neurons
decussate to the opposite anterolateral system, travel up the cord and end in the RETICULAR FORMATION (loosely organized core of grey matter) in the medullar and pons
third order go from pons to thallamus
fourth complete the path to the cerebral cortex