Chapter: 13 Spinal cord and spinal nerves Flashcards
List the 3 main functions of the spinal cord
- processes reflexes
- Integrates EPSPs and IPSPs
- Conducts sensory impulses to the brain and motor impulses to effectors
Reflex: in the spinal cord (what happens)
sensory input goes to the spinal cord and motor output comes right back out without having to go to the brain
What is the spinal cord protected by
- bone (vertebrae)
- connective tissue (meninges)
- fluid ( cerebrospinal fluid)
Which vertebra can you feel when you bend your neck down, the most prominent one
C7
What are the 3 meninges
- dura mater (outer/tough)
- arachnoid mater (middle/webby)
- pia mater (inner/soft)
Subdural hematoma would be where…
bleeding under the dura
Where does the spinal cord begin and end
begins at extension of medulla oblongata and terminates at level of L2
Spinal cord and Brain: gray+white matter
Spinal cord: gray matter on inside, white on outside
Brain: gray matter on outside and white on inside
What is the central canal in the spinal cord for
goes up to the brain to provide nutrients and csf
Characteristics of the spinal cord
- spinal ganglion: in the back
- posterior gray horn
- lateral gray horn
- anterior gray horn
- anterior root of spinal nerve: in front
- central canal
What is a lumbar puncture
a local anesthesia given, and a long hollow needle is inserted into the subarachnoid space to withdraw csf for diagnostic purposes, or to introduce abx, contrast media etc
Spinal nerves
spinal nerves connect the CNS to sensory receptors, muscles and glands and are part of the peripheral nervous system
How many PAIRS of spinal nerves are there
31:
8
12
5
5
1
How do spinal nerves attach
anterior and posterior roots attach a spinal nerve to a segment of the spinal cord
Epineurium
around the entire nerve
endoneurium
outside individual cell
perineurium
around each nerve fascicle
What happens to a nerve once it passes through its intervertebral foramen
spinal nerve divides into several branches known as rami
- present on anterior and posterior portion
What happens when the articular disc wears down in the vertebra
the intervertebral foramen shortens and starts to pinch a nerve
What are dermatomes
certain segments of the skin that are supplied by spinal nerves that carry somatic sensory nerve impulses to the brain
Phrenic nerve origin and function
origin is from C3, C4, C5 specifically C3.
- arises from cervical plexus
- supply motor fibers to the diaphram to allow for breathing
what does damage to a spinal cord above C3 level result in
respiratory arrest, inability to breathe
Where does the cervical plexus supply to
skin and muscles of the head, neck, superior portion of the shoulders, chest and diaphram
Where does brachial plexus supply to
the shoulders and upper limps
What does lesion of the median nerve lead to
carpal tunnel syndrome
Where does the median nerve originate from and its distribution
- C5 -T1
- flexors of forearm, muscles of middle finger
Where does the radial nerve originate from and its distribution
- C5 - T1
- triceps brachii, extensor muscles of forearm, thumb and index
Where does the ulnar nerve originate and its distribution
- C8-T1
- pinky, skin on medial side of hand
Where does the femoral nerve originate and its distribution
- L2-L4
- largest nerve arising from lumbar plexus, distributed to flexor muscles of hip joint and extensor muscles of knee joint, skin over anterior and medial aspect of thigh and medial side of leg and foot
Where does the obturator nerve originate and its distribution
- L2-L4
- Adductor muscles of hip joint, skin over medial aspect of thigh
Where does the sciatic nerve originate and its distribution
- L4-S3
- Actually two nerves- tibial and common fibular (bound together by common sheath of connective tissue); splits into its 2 divisions, usually at the knee.
As the sciatic nerve extends it branches to…
hamstring muscles and adductor magnus
Role of white and gray matter in the spinal cord
- white matter tracts conduct nerve impulses to and from the brain
- gray matter receives and integrates incoming and outgoing information to perform spinal reflexes
decussate
cross over
sensory tracts vs motor tracts in the spinal cord
sensory: starts w spin
motor: ends with spin
What is a reflex
a fast involuntary, unplanned response to a particular stimulus
What do reflexes help with
help to maintain homeostasis
Where are reflexes conducted
gray matter in the spinal cord
step by step: reflex
- sensory receptor: responds to a stimulus by producing a generator or receptor potential
- sensory neuron: axon conducts impulses from receptor to integrating center
- integrating center: one or more regions within CNS that relay impulses from sensory to motor neurons
- motor neuron: axon conducts impulses from integrating center to effector
- effector: muscle or gland that responds to motor impulses
reciprocal innervation
neural circuit simultaneously contracts one muscle and relaxes its antagonists
Stretch reflex
causes contraction of a muscle that has been stretched
Tendon reflex
causes relaxation of the muscle attached to the stimulated tendon
Flexor withdrawal reflex
causes withdrawal of a limb to avoid injury: moving foot away from lego piece
Crossed-extensor reflex
maintains balance during a withdrawal reflex
What do reflexes help to rule out
hematoma, or brain swelling
Shingles
an acute infection of the PNS caused by herpes zoster virus (also causes chickenpox)
- causes pain, discoloration of the skin and line of skin blisters
Shingles blisters do not cross
the midline
Amyotropic lateral sclerosis (ALS)
a progressive nervous system disease that affects nerve cells in the brain and spinal cord, causing loss of muscle control
Multiple sclerosis
demyelination of oligodendroglia
Spinal cord compression
the spinal cord may be compressed by bone, blood (hematomas), pus (abscesses), tumors (cancerous or not), or a ruptured or herniated disc
What does herniated disc do
it pinches the spinal nerve by shifting and growing closer to the nerve
Poliomyelitis (polio)
- caused by the poliovirus
- the virus spreads from person to person and can infect a persons spinal cord, causing paralysis
