Nervous System Flashcards
what do nerves do?
allow us to sense out environment - sensory and special senses
allow us to respond appropriately to the environment
reflex functions
what are the two anatomical subdivisions?
central nervous system and peripheral nervous system
what does the central nervous system include?
brain, spinal cord, central controller
what does the peripheral nervous system include?
all the other nerve tissue not within the CNS, spinal nerves, cranial nerves, autonomic nerves, wiring
what is a collection of nerve bodies called in the PNS and CNS?
PNS - ganglion
CNS - nucleus
what does the myelin sheath do?
increase the speed of conduction along the axon of a nerve
what is the function of an axon?
to conduct information away from the cell body
what is the myelin sheath produced by?
PNS = Schwann cells CNS = oligodendrocytes
which direction is the action potential for motor and sensory?
motor (efferent) = towards the body wall, body cavity or organ
sensory (afferent) = towards the brain
what is a single nerve fibre called?
an axon
what the six modalities an axon can conduct?
somatic sensory function somatic motor function special sensory function visceral afferent function sympathetic function parasympathetic function
what are the four lobes of each cerebral hemisphere?
named according to the cranial bone they lie deep to: frontal, parietal, occipital or temporal
what are the two things the cerebral consists of
sulci and gyri
how many cranial nerves are there?
12 pairs
what are the three cranial fossa?
anterior cranial fossa, middle cranial fossa and posterior cranial fossa
when does the spinal cord pass through in the cranium?
foremen magnum
what is the spinal cord protected by?
vertebral canal
what are the four segment of the spinal cord?
cervical, thoracic, lumbar and sacral/coccygeal
what are the two enlargements of the spinal cord?
cervical and lumbosacral
in what way does the spinal cord connect to the spinal nerves?
bilaterally
how many spinal nerves are there?
31, 8 cervical, 13 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
where does the spinal cord end?
at L1/L2 (conus medullaris)
how many vertebrae are there?
33, 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4 coccygeal
how do sensory axons reach the horn of the spinal cord?
sensory axons pass from the spinal nerve into the posterior root then into the posterior rootlets and then in the posterior form
how to motor axons reach the spinal nerve?
motor axons pass from the anterior form of the spinal cord into the anterior rootlets then into the anterior root into the spinal nerve
what do spinal nerves supply?
the soma (body wall)
where are spinal nerves located?
intervertebral foramina
from the intervertebral foramina where do spinal nerves connect?
the spinal cord via roots and rootlets or structures of the soma via rami
how many spinal nerves is each segment of the body supplied with?
a single pair
what are dermatomes?
area of skin supplied by both the anterior and posterior rami of a spinal nerve
what are the four nerve plexuses and what do they supply?
cervical plexus C1-C4 anterior rami, posterior scalp, neck wall and diaphragm
brachial plexus C5-T1 anterior rami, upper limb
lumbar plexus L1-L4 anterior rami, lower limb
sacral plexus L5-S4 anterior rami, lower limb, gluteal region and perineum
what does the soma include?
head and neck walls, chest walls, back, the diaphragm, abdominal wall, pelvic wall and limbs
what are the structure of the somatic nervous system?
skin, fascia, skeletal muscle, skeleton, internal lining of body cavities
what is somatic sensation?
sensation felt by the body wall (soma)
what sensations are felt by the soma?
coarse touch, fine touch, vibration, proprioception, temperature, pain, thermoreceptors sense temperature, nociceptors sense pain, mechanoreceptors sense the others
what is pain felt by the cell wall (soma) described as?
sharp and stabbing pain, well localised
where do somatic motor axons go once they cross over the brain stem?
descend to the anterior horn
from the anterior horn where are action potentials of somatic motor axons conducted?
within the anterior rootlets, then anterior roots, then into spinal nerves
what are spinal reflexes?
extremely rapid involuntary response that misses out pathway to the brain
what does the autonomic nervous system include:
viscera e.g. heart, lungs
glands
smooth and cardiac muscle
external lining of organs
where can the autonomic nervous systems be found?
internal organs in body cavities, body wall organs, sweat glands, arrestor smooth muscle, arterioles
what are organ sensory nerves called?
visceral afferent
what are some sensations from the organs to CNS?
touch, temperature, pain (ischaemic, colicky)
what is pain felt in the organs described?
dull, achey, nauseating, poorly localised
what are motor neurons?
respond to changes in the internal environment, they have a dual motor control , many internal organs have a sympathetic and parasympathetic nerve supply
what is the sympathetic division of the ANS?
supplies all the internal organs, body wall organs, arterioles, flight or fight response
what happens in the flight or fight response of the sympathetic nervous system?
pupils dilate, heart rate increases, bronchioles dilate in lungs, motility in GI tract is reduced
liver releases glucose into the blood, adrenal grands release adrenaline/noradrenaline
what is the sympathetic outflow?
passes down the spinal cord, exists spinal cord with T1-L2 spinal nerves, travel to sympathetic chains running the length of the vertebral column, pass into all spinal nerves (anterior and posterior rami, to supply body wall structures), with arteries travel to all head and neck organs and skin, via splanchnic nerves to reach organs
what is the parasympathetic division of ANS?
often supplies same internal organs as sympathetic division, does not supply body wall organs or arterioles, rest and digest (return to homeostasis, compliments/opposes the sympathetic system)
what happens during rest and digest of the parasympathetic nervous system?
all parasympathetic axons leave the ins via the cranial nerves III,VII,IX & X and via sacral spinal nerves, internal organs (parasympathetic ganglia in head to lacrimal gland and salivary glands. vagus nerve supplies organs of the neck, chest and abdomen
sacral spinal nerves carry parasympathetic axons to the handout, pelvis and perineum
