chapter 14 (spinal cord)

Dorsal Root:

(Is located in the back; carries afferent sensation from the PNS to the CNS)

Covered by meninges

(PAD) 1-Pia mater 2-Arachnoid mater 3-Dura mater -spinal meninges are continuous with brain meninges

:Gray mater

(Structure. Grey matter refers to unmyelinated parts of neurons ( only the aoxons are covered by myelin sheaths, but not the somas/neuron's bodies; therefore, the somas are unmyelinated) and interneurons. Is also the are where synapse is occurring.

:Central canal

(The central canal, also known as ependymal canal, is the cerebrospinal fluid-filled space that runs through the spinal cord.)

:Dorsal root ganglia

(The dorsal root ganglion contains the cell bodies and axon terminals of sensory neurons afferent that are synapsing with each other to carry that information that is coming from the environment to the Central Nervous System through the dorsal root.)

:Lateral horns

(The lateral horn of the spinal cord is the small lateral projection of grey matter located between the dorsal horn and ventral horn and contain the neuronal cell bodies of the sympathetic nervous system.)

:Ventral /anterior horns

(The ventral horns contains the cell bodies of motor neurons that send axons via the ventral roots of the spinal nerves.)

: White mater

(White matter is composed of bundles of myelinated axons. The axons connect various grey matter areas (the locations of nerve cell bodies) of the brain to each other and carry nerve impulses between neurons. NOT NEURON BODIES OR SYNAPSE occur here.)

:Posterior median sulcus

(a shallow vertical groove dividing the spinal cord throughout its whole length in the midline posteriorly.)

:anterior median fissure

(a vertical groove along the anterior(front) midline of the spinal cord that divides it into 2 symmetrical sides)

(what parts of spinal cord- nerve )are covered by meninges? Pia

(inner most)

:Ventral root

(is locate at front side of spinal cord; it carries effernt motor signals to the effector that can be skeletal muscle, smooth muscle, gland etc. At its distal end, the ventral root joins with the dorsal root to form a mixed spinal nerve.)

(what parts of spinal cord- nerve )are covered by meninges? Dura

(outer most)

: Dorsal /posterior horns

(posterior projections of the gray matter that contain primarily interneurons and the bodies of sensory neurons) are in charge of somatic and visceral sensory.

(what parts of spinal cord- nerve )are covered by meninges? Arachnoid

(semi outer)

ascending nerve tracts

- Are afferent (The ascending tracts refer to the neural pathways by which sensory information from the peripheral nerves is transmitted to the brain.)

what are reflexes?

- Are involuntary motor responses to specific stimuli (reflexes can be somatic visceral or special sensory; however somatic and visceral are the most common) (Ex: when you go to the doctor and he hit your knee with a hummer-like tool, and and your knee suddenly moves. that is a reflex)

spinal cord length and location

- Extends from the Magnum Foramen to Lumbar 1 -is 18 inches long

What is a nerve?

- Ia a bundle of neurons protected by layers of connective tissue. (- 3 layers of nerves are:) 1-Endoneurioum: it covers a single axon 2- perineurium: it covers the fascicle of neurons(bundle of neuron axons) 3-Epineurium: it covers the entire nerve

descending tracts

- are efferent (The descending tracts are the pathways by which motor signals are sent from the brain to lower motor neurones. The lower motor neurones then directly innervate muscles to produce movement, etc)

spinal nerves

- is made of 31 pairs: 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal ( to equal 62 nerves , since they are 31 pairs)

Ventral

- motor neurons (Carry efferent signals from CNS to PNS. They are responsible for all voluntary and involuntary movements.)

nerve plexus (4 terms)

-Is a network of nerves:(they are like regions that correlate with the areas where they are located) 1-cervical 2-Brachial 3-Lumbar 4-Sacral

What is a dermatomes?

-Is a sensory region that is monitored by a single spinal nerve segment. (ex: A dermatome is a region such as a thumb; therefore, when your thumb is feeling numbness, you already know which nerve or nerve segment is responsible for such sensation in that body part. in that way the doctor can check if that nerve has been pinched, moved, etc. )

Ipsilateral

-It remains on the same side (on the same side of the brain: for ex; if you see a heart, and your eye sends the signal to your brain and your brain's right side is in charge of shape, then the right side will know that is a heart shape. then send the signal to the part of the brain that is in charge of color, and that part of brain happens to be at the right side of the brain as well, that that means that the information did not go to the left side of the brain, so it was only ipsilateral)

Dorsal

-Sensory neurons (that carry afferent sensations from PNS to CNS.)

Lateral horns

-Visceral motor (Visceral efferent neurons are motor neurons that conduct impulses from CNS to PNS at smooth muscle, cardiac muscle, & glands. These neurons make up the Autonomic Nervous System. Some visceral efferent neurons begin in the brain; others in the spinal cord.)

Contralateral

-it crosses from right to left (of the brain) (this happens in the brain. EX: if you see the red light; your eye will send the signal to your brain. then in the brain the part in charged of color ( which can be in the right side of brain) will recognize it. then from there send the impulse to the left side of the brain( that can be in charge of knowing what red light mean) in this way the brain sent signals across the brain from left to right "contralaterally")

Posterior/dorsal horns

-somatic and visceral sensory (Posterior/Dorsal gray horn: posterior part of gray matter Function: contains sensory nuclei- somatic and visceral - receives information from skeletal muscles and skin (somatic) and visceral organs (visceral) and relays it to CNS.)

Anterior horns

-somatic motor (carry signals going from the CNS to PNS at body skeletal muscles)

can you map the nerves?

-yes, nerves are symmetrical and can be mapped.(map: means that you can know through dermatomes and homuculus what parts of the body are controlled by which nerve or nerve segment, )

Parts of the spinal cord-Axis (C2) cross section: (11 terms)

1-Posterior median sulcus 2-anterior median fissure 3-Central canal 4-Gray matter 5-white matter 6-Dorsal root ganglia 7-Dorsal root 8-Ventral Root 9-Dorsal/ posterior horns 10-Lateral horns 11- Ventral/ anterior horns

3 layers of a nerve:

1-endoneurium 2-perineurium 3-Epineurium

components (steps) of a reflex arc

1.Stimulus on receptor (in the body muscles) 2. activation of afferent neuron ( goes through dorsal root) 3. integration (make decision of what action to take and when it sends the signal to the efferent neuron, it also sends it to the brain via the Collateral to be used as memory for future references, like to not do it again , if it hurt you) 4. Activation of efferent neuron (ventral root ) 5. Response by effector.

3 layers of a nerve: Perineurium

It cover fascicles of neurons (around a fascicle)

Nuclei

are groups of neurons with similar function (mostly if you are referring to brain or spinal cord)

(optional) What is the meninges?

are the three membranes (the dura mater, arachnoid, and pia mater) that line the skull and vertebral canal and enclose the brain and spinal cord.

(optional) what is encased by meninges?

brain and spinal cord

3 layers of a nerve: Epineurium

covers the entire nerve

what are nerve tracts?

groups of neurons that go from CNS to PNS and vise versa.

3 layers of a nerve: Endoneurium

it covers the axon( of a neuron)