A&P Test 4 (Nervous System) Flashcards
cervical enlargement
due to nerves exiting the spinal cord and going to the arms
lumbar enlargement
due to nerves exiting the spinal cord and going to the legs
How many pairs of nerves are there?
31 total pairs
medullary cone
region where spinal cord tapers off
cauda equina
looks like horse hair
terminal filum
connective tissue that covers the spinal cord and holds it taught.
Meninges
dura mater, arachnoid mater, pia mater
dura mater
outer most layer, tough. Has epidural space - the space between the brain and the skull
arachnoid mater
middle layer, thin. have arachnoid traebeculi and granulations. Follows the contours of the brain very closely.
pia mater
inner mod flayer, attached to the nerve tissues
3 functions of the spinal cord
conduction, locomotion, and reflexes
spinal cord conduction
bundles of fibers (axons) pass info up and down
spinal cord locomotion
repetitive, coordinated actions of muscle groups
spinal cord reflexes
involuntary, stereotyped responses to stimuli (always the exact same)
S.C. ventral horn
larger than dorsal horn and where motor info exits
S.C. dorsal horn
smaller than ventral horn and where sensory info enters
S.C. white matter
full of myelinated axons
S.C. gray matter
has cell bodies and glial cells (NO AXONS)
S.C. nissl bodies
rough part of neuron w/ ribosomes (makes it dark)
S.C. central canal
hole down middle of the spinal cord, lined with ependygal cells
Spinal Tracts
Ascending (sensory info moving up) and Descending (motor info moving down)
decussations
an area where axons cross over (in medulla oblongata) particullary in the medulla pyramid where thousands cross. This is why the L side of our body is controlled by the R side of our brain
Contralatteral
nerves enter spinal cord and immediately cross over
ipsilateral
nerve stays on the same side of the body until it reaches the medulla.
Nomenclature of Spinal Tracts
1st part is origin, 2nd part is destination
CNS Ascending Pathway 1
involves deep touch, vibrations, limb movements, and positioning (propriorecption). The fascicles gracilius and cutaeneous carry the signals from legs and arms/neck (decussation in 2nd order of medulla)
CNS Ascending Pathway 2
spinothalymic tract; pain, pressure, temp, light touch, tickle, and itch (decussation in spinal cord)
Afferent Peripheral NS
sensory divisions, carries signals from receptors to the CNS (somatic = skin, muscles, bones, and joints) and (visceral = organs)
Efferent Peripheral NS
motor division carries signals from the CNS to the effectors
somatic = skeletal muscles) and (visceral = cardiac, smooth and glands
mixed nerves in PNS
carry sensory info up and motor info down (very common)
3 layers of the PNS
epineurium (outer most, covers whole nerve), perineurium (middle, covers axon cluster), and endonerium (inner, covers individual axons)
Ganglia in the Peripheral NS
cluster of neuron cell bodies, sensory nerves go up thru dorsal root ganglia (no synapsing), autonomic ganglia contains the synapse and pre ganglionic fibers
Spinal Nerve Plexus
areas where lots of nerves cross and mix up
phrenic SNP
cervical plexus in diaphragm (C1-C5)
median SNP
center of palm, gives us carpal tunnel (C6-T1)
ulnar PNS
funny bone, shakes pinky and ring finger (C6-T1)
radial PNS
controls radial forearm muscles (C6-T1)
femoral PNS
BIG, supplies leg with blood (L1-L4)
sciatic PNS
largest nerve in the body (L4-S4)
pudendal
goes to reproductive organs (L4-S4)
dermatone
area ok skin that sends sensory info to the spinal cord, the edges of a dermatome overlap up to 50%
reflexes
quick, involuntary stereotyped reactions of glands/muscles. (it is an autonomic response to sensory info)
Functions of Reflexes
stimulation of receptors, afferent fibers carry signals to spinal cord, interneurons integrate the info, efferent fibers carry impulses to effectors
Stages of the Reflex Arc
central canal lined by epyendimal, white matter is myelinated axons moving up and down, info into dorsal and out of ventral, all synapses occur in the gray matter (tons of neurons)
The stretch reflex
when a muscle is stretched, it contracts and maintains in increased tone (helps with posture)
reciprocal inhibition
prevents muscles from working against each other
muscle spindles
sense organs that monitor length of the skeletal muscles. highly modified muscle cells. instead of lots of myofibrils, only a few that send all of the signals
Steps of the Patellar tendon reflex
muscle stretches, muscle spindle stimulated, afferent neuron is excited, afferent neuron stimulates motor neuron to extensor,extensor muscles contract, afferent neuron sends inhibitory signals, interneuron inhibits motor neuron and flexor
withdrawl reflex
step on something sharp, afferent signal goes in, synapse to motor neuron and causes you to lift your leg, hamstring fires and quad relaxes
autonomic nervous system
efferent (motor) fibers only, operates w/o conscious instruction, supplies cardiac and smooth muscles/glands
sympathetic division of autonomic NS
tends to arouse (release NE)
parasympathetic division of autonomic NS
tends to calm (releases ACe)
visceral reflexes
receptors detect stimuli to stretch
barorecpetors
detect blood pressure, CN IX sends signals to medulla and CN X sends signals to the heart
Autonomic NS and its 2 neurons
send from CNS to to effectors thru 2 neurons: presynaptic and postsynaptic. It modifies the effector instead of causing something to happen
presynaptic neurons
cell body in brain or spinal cord
postsynaptic neurons
cell bodies in peripheral ganglion
Sympathetic nervous system
the origin of presynaptic neurons in the gray matter of the thoracic and lumbar spines (T1-L2)
sympathetic chain ganglion
pathways of preganglionic fibers, enters the ganglion and synapse then travels to higher and lower ganglia for synapsing. Doesn’t synapse in chain, but reaches the collateral ganglia.
adrenal glands
sits on top of the kidneys and has 2 components: cortex and medulla
cortex of the adrenal gland
secretes steroids and hormones
medulla of adrenal gland
modifies sympathetic ganglion (85% epinephrine, 15% norepinephrine) secretes chemicals into neurotransmitters which get into our blood and spread out every where.
7 responses to increased sympathetic activity
heightened mental alterness, increased metabolic rate, reduced digestive and urinary function, energy reserves activated, increased reparatory rate, increased heart rate and B.P. and sweat glands activated
origins of Parasympathetic N.S.
pons and medulla oblongata (C.N. nuclei), sacral spinal cord (S2-S4)
Pathways of Parasympathetic N.S.
CN III (cardiac), CN VII (pulmonary), CN IX (esophagael), CN X (abdominal aeortic)
Responses of Parasympathetic N.S.
decreased: metabolic rate, heart rate, and B.P.
increased: salivary and digestive glands, motility and blood flow.
urination and defecation stimulation
2 types of Neurotransmitters
cholinergic: secretes ACh; adrenergic: secretes NE (neropinephrine)
Receptor Pharmacology
specific receptors can be blocked or stimulated by specific drugs; Alpha and Beta blockers: control B.P. and heart rate; Albuterol: beta stimulate (inhalers); Atropine: muscarinic blockers (contraction and dilation of eyes)
Dual Innervation
2 divisions work against each other, one arises and the other calms. Cooperation effects when both work together (saliva) PNS = serous cell secretion, SNS = mucous cell secretion
things w/o dual innervation
adrenal medulla, arrestor pili, sweat glands, blood vessels (sympathetic only)
Brain
weighs 3-3.5 pounds, major parts are brain stem, cerebrum, and cerebellum. cerebrum is 83% of brain volume, cerebellum is 50% of neurons
meninges of dura mater
outer periosteal layer, inner meningeal layer, dural venous sinuses, dural hemorrhages
outer periosteal layer
next to the brain (near bone)
inner meningeal layer
closer to arachnoid (near brain)
dural venous sinuses
spots where periosteal and inner meningeals are not connected (biggest sinus is the saggital sinus that splits the brain in half
dural hemorrhages
epidural (broken arteries in periosteal causes bleeding and puts pressure on skull) subdural (lower pressure and fluid moves to arachnoid)
arachnoid maer
little strands sink down and attach to the pia mater (traebeculi) it also holds our cerebrospinal fluid and follows the brain very closelsy
Ventricles
lateral ventricles, thrid ventricle, cerebral aqueduct, fourth ventricle, central canal. All are lined with ependymal cells and contain CSF
cerebrospinal fluid
clear fluid fills the ventricles and canals in subarachnoid space.
choroid plexus
region in ventricles where CSF is created, blood comes in, crosses pia mater thru chord epithelium
3 functions of cerebrospinal fluid
buoyancy: helps the brain float so it doesn’t squish; protection: helps prevent concussions by dampening the blow; chemical stability: constantly changing environment with ions in and out. Escapes through the fourth ventricle into subarachnoid space and is then moved by granulations into dura venous sinuses
endotheleum
subsquamous lining thats permeable to lipid soluble materials (alcohols, oxygen, carbon dioxide, caffine, nicotene, and anesthetics)
medulla oblongata
cardiac center (clusters of neurons that regulate heart rate) and vasomotor center (regulates blood vessel contraction and dilation). Has axons that go up and down and is the reflex center for sneezing, coughing, swallowing, vomitting, sweating, and movements of the head and tongue
pons
similar to medulla but controls respiratory and bridges to cerebellum
cerebellum
white mater on inside called arbor vitae (tree of life), and sits onto of 4th ventricle
cerebellum input
controls vision, audio, balance, reticular, and motor info
cerebellum output
goes to brain and then splits into medulla or pons
functions of cerebellum
smoothes muscle contractions, maintains muscle tone/posture. coordinates different joints and aides in motor skills, eye movements. (Gives us muscle memory)
midbrain
oculomotor nucleus, substantia nigra, cerebral peduncles, tegmentum
oculomotor nucleus
CRN III - eye movments
substantia nigra
sends inhibitory signals to basal nuclei and thalamus (runs out of dopamine)
cerebral peduncles
holds corticospinal tract
tegmentum
connects to cerebellum and helps control movements
superior colliculi
contains neuron cell bodies so we can see out of the corner of our eyes, if something moves its due to synapse of superior colliculi
inferior colliculi
turn your head when you hear something due to synapse of inferior colliculi
Reticular Formation
clusters of gray matter, regulates balance and posture, includes cardiac and vasomotor centers, analgesic (pain) pathways, regulates sleep, conscious attention, and fatigue
thalamus
oval masses of gray matter; almost all sensory matter goes here first, its a relay station and is interconnected to limbic system (emotion and memory)
hypothalamus
looted on walls and floor of the third ventricle, FUNCTIONS: hormone secretion, autonomic N.S. control, thermoregulation, food and water intake, sleep and circadian rhythms, memory, and emotional behavior
epithalamus
(pineal gland) helps secrete melatonin, no output, helps fish recognize day/season and helps us with circadian
cerebrum
big parts of brains (all of the lobes)
frontal lobe
voluntary motor functions (planning, mood, smell, social judgements)
parietal lobe
areas for sensory reception and integration of sensory info
occipital lobe
visual center of brain
temporal lobe
areas of hearing, smell, learning, memory, emotions
insula
emotionally relevant context for sensory info, desires and cravings
tracts of cerebral white matter
cerebral cortex, projection tracts, association tracts, and commisural tracts
cerebral cortex
gray matter all around outside (cell bodies and glial cells).
white matter is full of axons (unmyelinated) axons take 1 of 3 tracts
projections tracts
allow info to go up and down within the brain
association tracts
allows info to go from lobe to lobe within the same hemisphere of the brain
commisural tracts
allows info to go from left side to right side of the brain
basal nuclei
clusters of cell bodies in cerebrum white matter that helps control muscle movements. receives input from substantial nigra and motor cortex, involved in motor controls and inhibits tremors
limbic system
loops of cortical structures surrounding the deep brain
things that limbic system affects
amygdala (emotions), hippocampus (memory), fornix, and cingulate gyrus
somesthetic sensation
precentral - frontal lobe
postcentral - parietal lobe
both help with muscle control
homunculus
area of cortex dedicated to sensations of various body parts and is proportional to how sensitive each body part is
somesthetic association
(parietal) position of limbs, location of touch or pain, shape, weight, and texture
visual association
(occipital) identify the things we see
auditory association
(temporal) remember names of songs, recognize people by their voices
