ch 12 (nervous tissue) Flashcards
what does the central nervous system (CNS) consist of?
the brain and spinal cord.
- the spinal cord is connected to the brain through the foramen magnum of the occipital bone
what does the peripheral nervous system (PNS) consist of?
it consists of all nervous tissue outside the CNS: some components include
- nerves
- ganglia
- enteric plexuses
- sensory receptors
nerve
is a bundle of axons located in the PNS.
ganglia
(= swelling or knot; singular is ganglion)
they are small masses of nervous tissue, consisting primarily of neuron cell bodies.
- <a>
- located in the PNS.</a>
how many cranial nerves emerge from the brain?
twelve pairs!
how many pairs of spinal nerves emerge from the spinal cord?
thirty-one pairs!
sensory receptor
refers to a structure of the nervous system that monitors changes in external and internal environments.
- examples: touch receptors; olfactory receptors; etc.
what are the 3 subdivisions of the peripheral nervous system - PNS?
1.) somatic nervous system (SNS)
2.) autonomic nervous system (ANS)
3.) enteric nervous system (ENS)
what does the somatic nervous system (SNS) consist of?
1.) sensory neurons that convey info to the CNS from somatic receptors in the head, body wall, limbs, and special senses.
2.) and motor neurons that conduct impulses from the CNS to skeletal muscles only.
nodes of Ranvier
gaps in the myelin sheath
neurolemma
outer nucleated cytoplasmic layer of a Schwann cell, which encloses the myelin sheath.
ONLY found around axons in the PNS.
myelin sheath
consists of up to 100 layers of Schwann cell membrane.
nucleus
is a cluster of neuronal cell bodies located in the CNS.
tract
is a bundle of axons that is located in the CNS.
- they interconnect neurons in the spinal cord & brain.
summation
the process by which graded potentials add together.
graded potential
small deviation from the resting membrane potential that makes the membrane more or less polarized.
when a membrane is hyperpolarized, it is…
…more negative inside.
when a membrane is polarized, it is…
…less negative inside.
action potential (AP) / impulse
sequence of quick events that decrease and reverse the membrane potential, and then restore it to its original resting state; it has two phases:
1.) depolarization
2.) repolaraization
what does endoneurium consist of?
collagen fibers, fibroblasts and macrophages.
what does the perineurium consist of?
thick CT, 15 layers of fibroblasts and collagen fibers.
what does epineurium consist of?
fibroblasts and thick collagen fibers.
rami = ?
= branches
what are the 5 plexuses?
cervical, brachial, lumbar, sacral, and coccygeal.
which are the thoracic nerves / intercostal nerves that do not belong to a plexus?
anterior rami of spinal nerves T2-T12.
cervical plexus:
C1-C4
some C5
- supplies skin and muscles of the head, neck, and superior shoulders and chest.
brachial plexus:
C5-C8
some of T1
explanation of the complexity of the brachial plexus!!
- anterior rami form roots.
- roots unite to form trunks (superior, middle, inferior trunks)
- trunks diverge into divisions (anterior & posterior)
- in axillae, divisions unite to form cords (lateral, medial & posterior cords)
- the branches form the principle nerves of the brachial plexus.
what are the 5 large terminal branches that arise from the brachial plexus?
1.) axillary nerve
2.) musculocutaneous nerve
3.) radial nerve
4.) median nerve
5.) ulnar nerve
axillary nerve
deltoid & teres minor muscles
musculocutaneous nerve
anterior arm muscles.
radial nerve
posterior aspect of arm and forearm.
median nerve
most muscles of anterior forearm and hand.
ulnar nerve
anteromedial muscles of forearm and most of hand.
