Exam 4 Flashcards
functions of the nervous system
sensory (impulse)
integrative (sorts info)
motor (response)
central nervous system
brain & spinal cord
peripheral nervous system
nerve cells & fibers outside the brain & spinal cord
afferent
brings information from the periphery to the central nervous system (part of PNS)
efferent
sends information from the central nervous system out to the periphery (part of PNS)
somatic
voluntary (efferent)
autonomic
involuntary (efferent)
sympathetic
fight or flight (autonomic)
parasympathetic
vegetative functions (autonomic)
enteric nervous system
the brain of the gut (previously considered part of the autonomic nervous system)
nerve
collection of nerve fibers in the PNS
tract
collection of nerve fibers in the CNS
gray matter
mostly neuron cell bodies
white matter
all fibers, mostly myelinated
nucleus
collection of nerve cell bodies in the CNS
ganglion
collection of nerve cell bodies in the PNS
stimulus
excites neuron
neurons
- the only cells that can carry the impulse
- large excitable cells that conduct the impulse
- little mitosis after birth
glial cells
(supportive)
PNS= Schwann cell & satellite cells in ganglia
CNS= oligodendrocytes, astrocytes, microglia, ependymal
schwann cell
makes myelin
oligodendrocytes
part of myelin
astrocytes
blood/brain barrier
microglia
phagocytic cells
ependymal
line vessel cavities & cerebral spine
nerve cell body
- contains lots of rough ER
- also contains nucleus, neurofibrils (intermediate filaments), microtubules & other organelles
- lipofuscin granules (yellow-brown pigment related to aging)
dendrite
- the nerve fiber(s) which carries the impulse to the cell body
- some cytoplasm
- often highly branched
- the afferent fiber
axon
- the nerve fiber(s) which carries the impulse away from the cell body to an effector
- only one per neuron
- the efferent fiber
types of neurons
structure -multipolar -bipolar -psuedounipolar/unipolar function -sensory= afferent -association/interneurons= integrative motor= efferent
myelinated nerve fibers
- myelin insulates axon; increases speed of AP conduction
- composed of plasma membranes of schwann cells (PNS) or oligodendrocytes (CNS)
- gaps= nodes of ranvier
- saltatory conduction= impulses jumps from gap to gap
unmyelinated nerve fibers
- processes aren’t as important
- slower conduction
- still have a schwann cell sheet
plasma membrane
- composed primarily of lipid (non-polar)
- non-polarized substances can get through the lipid bilayer
- special ion channels in the plasma membrane allow polarized substances (Na, K, Ca) to get across lipid bilayer
types of ion channels
leakage= random open/close ligand-gated= opens/closes i.r.t NTs, hormones, calcium, etc. (ex. neuromuscular junction) mechanical-gated= opens/closes i.r.t. pressure, vibration, etc. voltage-gated= opens/closes i.r.t. change in membrane potential
electrical gradient
different charge on either side of the membrane
chemical gradient
different concentrations of Na and K on either side of the membrane
electrochemical gradient
- outside= more positive (Na)
- inside= less positive (K)
- channels do not effect charge
sodium potassium pump
- effects electrochemical gradient
- for every 3 Na that get pumped out, only 2 K get pumped in
potential
difference between inside & outside the membrane
resting membrane potential
charge= -70mV
graded potential
- a small deviation from the membrane potential caused by a stimulus
- if it makes membrane depolarize a little, then membrane is more excitable
- if it makes the membrane more polarized, the membrane is less excitable (inhibited)
- are local and graded (not all-or-none)
- summation= added together
- often occur in sensory receptors
- can occur in dendrites/cell bodies (post-synaptic potential)
action potential
- nerve impulse
- a series of changes in the potential (voltage) of the membrane
- depolarization= membrane gets more +
- repolarization= membrane goes back to -
- refractory period= another AP cannot fire for awhile
- all-or-none
- can only go in one direction bc refractory period
depolarization
- Na rushes in (flood gates have been opened)
- K rushes out
- the membrane potential rises towards 0 and even gets positive
- eventually gets so positive inside that further influx of positive ions is repelled
repolarization
- the sodium potassium pump kicks in again
- Na is pumped out of the axon
- K is pumped into the axon
- not at equal rates bc pump
- a hyper-polarization phase may occur in which the membrane overshoots the membrane potential
refractory period
- absolute= no stimulus can provoke another AP (Na channels inactivated; resting)
- relative= an AP can be initiated only by a greater than normal stimulus
- larger the diameter of the axon, the shorter the absolute refractory period
- cardiac muscle has the shortest refractory period
self-propagating (AP)
- at the leading edge of an AP, sodium gates open, allowing sodium ions to flow into cell
- this flow of ions triggers more sodium gates to open, causing the AP to move
- at the trailing edge of an AP, potassium gates open, allowing positive ions to flow out, and restoring the resting potential of the neuron
- like the domino effect
axon hillock
very beginning of the axon (trigger zone)
continuous conduction
- relatively slow
- step-by-step depolarization and repolarization
- found in unmyelinated fibers
- takes more energy
saltatory conduction
- impulse jumps from node to node
- faster
- takes less energy bc fewer regions of the membrane undergo depolarization/repolarization and Na pump doesn’t have to work so hard
- in myelinated nerves
affects on speed of propagation
- presence of myelin (myelin=fast)
- diameter of axon (large=fast)
- temperature (cold=slows pain impulses)
A nerve fiber
- largest
- shortest refractory period
- myelinated
- large sensory & motor fibers
B nerve fiber
- middle diameter
- longer refractory period
- myelinated
- sensory from skin and viscera to CNS
- motor to some autonomics
C nerve fiber
- smallest
- longest refractory period
- unmyelinated
- heat, cold, pain, and some motor
signal transmission at the synapse
- usually axon of first neuron to dendrite of second neuron= axodendritic
- some axon-axon and some axon/cell body synapse
- two types: electrical (ex. cardiac muscle) & chemical (have to have NT)
electrical synapse
- impulse conducted directly between cells via gap junctions (no NT involved)
- faster than chemical synapse
- better synchronization (ex. cardiac muscle)
- doesn’t have a latent period bc no synapse
chemical synapse
presynaptic neuron releases NT which diffuses across the synaptic cleft and binds to the receptor on the postsynaptic neuron, which produces some postsynaptic potential
transmission of impulse
- nerve impulse arrives at presynaptic terminal
- the depolarization of the presynaptic axon opens voltage-gated Ca channels
- Ca ions flow into the cell
- at resting conditions, [Ca] greater outside of cell
- intracellular [Ca] triggers exocytosis of synaptic vesicles, which release NTs, which diffuse across synaptic cleft and bind to receptors on post-synaptic membrane
- NT/receptor complex opens ion channels and ions flow in
- if Na channels are opened, Na rushes in= depolarization
- if Cl channels are opened, Cl rushes in= hyperpolarization
if sum of postsynaptic potentials doesn’t reach threshold…
- membrane may be excited/more likely to fire (slightly depolarized)= EPSP
- membrane may be inhibited/less likely to fire (hyperpolarized)= IPSP
how synapse turns off…
- NT diffuses away from the synaptic cleft
- NT is degraded by enzymes
- NT is taken up by presynaptic site
- -SSRIs= seratonin specific reuptake inhibitors
ACh
- excitatory or inhibitory
- NMJ, some other PNS and CNS synapses
- inactivated by acetylcholinesterase
cholinergic
has ACh at synapse
adrenergic/noradrenergic
has epinephrine/norepinephrine at synapse
dopaminergic
has dopamine at synapse
amino acid NTs
glutamate
aspartate
glycine
GABA
biogenic amines
tyrosine L-Dopa dopamine norepinephrine epinephrine -all are based on tyrosine -nor=nitrogen w/o radical group
nitric oxide
- synthesized as needed
- lipid soluble
- immediate action
- highly reactive but short acting
- relaxes vascular smooth muscle
neuropeptides
(chains of amino acids)
endorphins
enkephalins
substance P (P=pain)
diverging neural circuit
from one neuron to many neurons (one impulse causes many things)
converging neural circuit
from many neurons to one neuron (multiple synapses to one cell body)
reverberating neural circuit
a series of coordinated impulses (ex. respiratory rhythm)
nerve tissue repair in PNS
if cell body remains intact, the peripheral nerves may repair (cell bodies in spinal cord)
nerve tissue repair in CNS
- some new neurons in the hippocampus
- problems with scar tissue after injury interfere with repair
repair of fibers in PNS
- 24-48 hrs post injury: Nissl bodies (RER) break up= chromatolysis
- 3-5 days post injury: distal to the injury axon swells, breaks into fragments, myelin deteriorates= Wallerian degeneration
- leftovers are phagocytized by macrophages, etc.
- if schwann cell tube is present, the regenerating axon will sprout
multiple sclerosis
- autoimmune
- demyelinating disease
- causes loss of coordination/senesation
epilepsy
abnormal electrical events
Guillain-Barre
ascending paralysis
neuropathy
- something wrong with the nerves
- tingling or small odd senesations
neuroblastoma
tumor of neuroblasts
rabies
- caused by a neurotropic virus
- goes to neurons
structures that protect the spinal cord (outer most to inner most)
bones (vertebral column) epidural space dura mater subdural space arachnoid mater subarachnoid space (CSF) pia mater
what holds spinal cord in place
denticulate ligaments (thickening of teh pia)
cervical englargement
C4-T1
upper extremities
lumbar enlargement
T9-T12
lower extremities
conus medullaris
L1/L2 interspace
where spinal cord ends
cauda equina
nerve roots w/o spinal cord
filum terminale
small string of tissue at the bottom of the spinal cord
lumbar puncture
- CSF in the subarachnoid space
- L2-L5 bc no spinal cord
segmentation of the spinal cord
C1-C8
T1-T12
L1-L5
S1-S5
spinothalamic tract
-ascending= sensory
-anterior and lateral:
contralateral (changes sides)
pain
temperature
itching
tickling
deep pressure
crude touch
-posterior:
proprioception
discriminative touch
2-point discrimination
light pressure
vibration
corticospinal tract
-descending= motor
pyramidal tracts
- precise voluntary movement of skeletal muscle
- lateral corticospinal tract
- anterior corticospinal tract
- corticobulbar tract (cranial nerves)
- carry motor impulses that originate from the cerebral cortex
extrapyramidal tracts
- rubrospinal
- tectospinal
- vestibulospinal
- coordinate movements w/ visual stimuli
- regulate muscle tone
- maintain contraction of postural muscles
- equilibrium
reflex
- a fast, involuntary, unplanned sequence of actions that occurs in response to a particular stimulus
- somatic= contraction of skeletal muscles
- autonomic= gastrocolic, pupils, etc.
5 components of a reflex
- sensory receptor (recepts info)
- sensory neuron
- integrating center (multisynaptic or monosynaptic; spinal cord of brain stem)
- motor neuron (response)
- effector (what happens; skeletal muscle, smooth muscle, cardiac muscle, glands)
stretch reflex
- receptor: muscle spindle, monitors stretch (ex. quadriceps in patellar reflex)
- sensory nerve: from receptor through posterior root
- integrating center: spinal cord, sensory neuron synapses w/
- motor neuron in the anterior gray horn
- motor axon travels out anterior root to PNS to muscle
- tests connections to spinal cord
- most simple reflex
- 2 neurons only
- ipsilateral
- doesn’t go up to brain
- ex. patellar reflex (L2-L4), achilles tendon (lumbosacral levels), biceps tendon
reciprocal innervation
if agonist muscle contracts, the antagonist muscle must relax
tendon reflex
- receptor: golgi tendon organ detects increased muscle tension
- nerve impulse carried through posterior root into posterior horn
- integrating center: spinal cord, inhibitory neuron synapses w/ a motor neuron, which is hyperpolarized (inhibited)
- effector muscle of that tendon relaxes and relieves excess tension
- tests muscle tension
- ex. dropping something heavy
flexor-crossed extensor reflex I
- receptor: pain receptors
- sensory neuron to spinal cord
- integrating center: spinal cord, various segments (intersegmental), multiple neurons
- motor neurons send impulses to
- neuromuscular junctions
- ex. pull foot back when step on lego
flexor-crossed extensor reflex II
- in spinal cord interneurons synapse w/ motor neurons on the opposite side of the spinal cord (contralateral)
- motor neurons carry nerve impulse to nerve ending
- effector: contraction of extensor muscles of the opposite side
- ex. other leg supports weight (muscles contract) after pull foot back when step on lego
structure of a peripheral nerve (outer most to inner most)
epineurium
perineurium
endoneurium
axon
distribution of spinal nerves
- dorsal ramus: supplies muscles and skin of back
- ventral ramus: extremities, lateral and ventral trunk (become a plexus)
- -ventral rami of T2-T12= intercostal nerves
- ramus communicantes: part of ANS
plexus
- network of nerve fibers
- ventral rami of spinal nerves branch and form nertworks
cervical plexus
C1-C4
- innervates skin, muscles of neck, head, shoulder region, diaphragm
- connects with XI & XII
phrenic nerve
C3, C4, C5
brachial plexus
C5-T1
- axillary nerve: deltoid, teres major
- musculocutaneous nerve: flexors of arm & forearm
- radial nerve: muscles of posterior arm & forearm (damage= wrist drop)
- median nerve: muscles of anterior forearm and palm thumb (damage= numbness, tingling pain in fingers, weak thumb movements, inability to pronate forearm)
- ulnar nerve: anteromedial muscles of forearm & fingers (damage= difficulty holding/picking up piece of paper; inability to flex & adduct the wrist)
- long thoracic nerve: serratus anteripr (damage= winged scapula)
lumbar plexus
L1-L4
- femoral nerve: flexors of thigh & extensors of the legs (quads, iliopsoas, sartorius); skin over anterior and medial aspect of thigh and medial side of leg and foot
- iliohypogastric
- ilioinguinal
- genitofemoral
- lateral cutaneous nerve of the thigh
- obturator nerve
sacral plexus
L4-S4
- buttocks, perineum, lower extremity
1. sciatic nerve: largest nerve - tibial nerve: posterior compartment muscles; medial & lateral plantar nerves
- common fibular/peroneal nerve: anterior compartment & lateral compartment of leg
- pudendal nerve= muscles of perineum, skin over external genitalia, vagina
- damage= foot drop
dermatome
-skin supplied by the dorsal root of a spinal nerve (sensory innervation from one level of spinal cord)
C3 (dermatome)
front & back of neck
C6 (dermatome)
thumb
C8 (dermatome)
ring and little fingers
T4 (dermatome)
nipples
T10 (dermatome)
umbilicus
L1 (dermatome)
inguinal
L3 (dermatome)
knee
L5 (dermatome)
anterior ankle and foot
S1 (dermatome)
heel
S5 (dermatome)
perianal
transection of spinal cord
- completely cut across (rare)
1. permanent loss of sensation in dermatomes distal to the injury
2. permanent loss of voluntary muscle contraction distal to the injury
polio
- neurotropic virus
- invades the nerves
- can cause paralysis
meningitis
inflammation of meninges
nerve block
anesthetic
epidural block
anesthetic only affecting perineal muscles
neuralgia
pain associated w/ nerves
neuritis
inflammation of the nerve
paresthesia
weird feelings (tingling, etc.)
shingles
follows dermasome
facts about the brain
- receives 20% of the cardiac output at rest
- relies on glucose alone as its energy source
- arterial supply= internal carotid arteries & basilar artery
- venous drainage via venous sinuses of the dura mater into the internal jugular veins
cerebrovascular supply
- carotid system
- vertebral basilar system
- all vessels get connected in circle of willis
- each branch off of circle of willis goes to a different part of the brain
venous drainage
all sinuses communicate w/ each other (organisms like infection can spread throughout)
blood brain barrier
- protects the brain
- astrocyte forms junctions w/ cells around capillaries
- doesn’t block most drugs
what separates parts of the brain?
dura goes between hemispheres, cerebrum, and cerebellum
function of cerebrospinal fluid
- shock absorption
- circulation
- chemical protection
production of cerebrospinal fluid
choroid plexuses in ventricular walls of brain
circulation of cerebrospinal fluid
lateral ventricles (cerebrum) > interventricular foramina > 3rd ventricle (diencephalon) > cerebral aqueduct (midbrain) > 4th ventricle (brain stem) > subarachnoid space & central canal *constantly circulating
reabsorption of cerebrospinal fluid
- into blood via arachnoid villi in superior sagittal sinus
- production MUST equal reabsorption
- normal volume= 125mL
hydroencephalis
- over production of CSF
- brain is squished which results from blockage in path
- can be relieved by a shunt (empties into abdomen)
parts of brain stem (going up)
- medulla (most inferior; connects w/ spinal cord)
- pons (cephalic to medulla; a bridge)
- midbrain (cephalic to pons)
white matter of medulla
motor:
-pyramids: carry info to pyramidal tracts (lateral corticospinal)
-pyramidal decussation: 90% of fibers cross
-where most strokes happen
sensory:
-ascending axons of the posterior column system
-these continue up toward the thalamus as the medial lemniscus
gray matter of medulla (nuclei)
- cardiovascular center
- respiratory center
- vomiting, coughing, sneezing, swallowing, hiccupping
- olivary nuclei: lateral to the pyramids (input from many areas, especially cerebellum)
- cranial nerve nuclei (VIII, XI, X, XI, XII)
pons
- lies above the medulla
- connected to the cerebellum
- conveys info about movement from cerebral hemispheres to the cerebellum
- vestibular nucleus (path of VIII)
- pneumotaxic area (breathing)
- apneustic center
- respiratory center
- V, VI, VII, VIII
midbrain
- connects pons to higher centers
- connects pons w/ diencephalon
- center for auditory and visual reflexes
- cerebral peduncles: motor (anterior)
- Tectum (posterior; made up of 4 bumbs in 2 pairs)
- -superior colliculi: visual reflexes
- -inferior colliculi: auditory reflexes
- substantia nigra: dopamine; only area in brain w/ pigment
- red nuclei
reticular activating system
- spans the brainstem and the diencephalon
- center for arousal & consciousness
- parts all over the brain
- keeps you awake
- w/o system= coma
white matter of cerebellum
arbor vitae
connections of the cerebellum
- superior cerebellar peduncle: to midbrain and thalamus
- middle cerebellar peduncle: to pons
- inferior cerebellar peduncle: to medulla
functions of the cerebellum
- coordination of voluntary movements
- motor learning
- cognitive functions
tests for cerebellum
- coordination test (ex. heel-to-toe)
- prediction test (fingertip to nose w/ closed eyes; heel to shin)
- balance equilibrium (stand w/ eyes closed)
- alcohol affects cerebellum
diencephelon
- thalamus= 80%
- 2 sides connected by the intermediate mass of the thalamus
- major relay center for sensations that project to the cortex (sensations come up posterior column to diencephelon; sorts out sensations)
- part of limbic system (memory/emotions)
- receives info from cerebellum
- relays info from CBLM and basal ganglia to primary motor cortex
- contributes to RAS & autonomic activities
- hypothalamus is other part
- supraoptic region (pituitary gland)
- mammillary bodies (smell)
functions of the hypothalamus
- center for ANS
- hormone production:
- oxytocin (labor)
- ADH (stimulates reabsorption of water in kidney)
- releasing factors (affect pituitary gland) - regulation of emotional/behavioral patterns: rage, aggression, pain, pleasure, etc.
- satiety center (fullness)
- thirst center (monitors [sodium] in blood)
- thermostat
- regulation of circadian rhythms
5 parts of the brain
telencephelon= cerebral cortex (I) diencephelon= thalamus hypothalamus (II) mesencephalon= midbrain (III, IV) metencephelon= pons, cerebellum (V, VI, VII, VIII) myelencephelon= medulla (VIII, XI, X, XI, XII)
cerebrum
- right & left hemispheres connected by corpus callosum (broad band of white matter)
- gray matter= superficial
- white matter= deep
- gyrus/gyri= folds of cortex
- sulcus/sulci= grooves between gyri
lateral sulcus
between frontal and temporal lobes (have 2)
central sulcus
between frontal and parietal loves (have 2)
white matter of the cerebrum
- association tracts: conduct impulses between gyri; same hemispheres
- commissural tracts: conduct impulses between hemispheres
- anterior commissure (spinal cord)
- posterior commissure (spinal cord)
- corpus callosum (biggest) - projection tracts: from one level of the brain to another (ascending & descending)
basal ganglia
- mostly gray matter
- nuclei
- stimulated when something goes wrong
- globus pallidus
- putamen & caudate= corpus striatum
- substantia nigra
functions of basal ganglia
- purposeful motor activity
- slow, sustained contractions
- inhibiting muscle tone
- ex. swinging arms while walking
dyskinesias (basal ganglia)
- when movements don’t work right
- chorea: big movements that don’t have control of (ex. Huntington’s)
- athetosis: smooth movements that can’t control (ex. cerebral palsy)
- hemiballismus: big uncontrolled movements on one side
- resting tumor: uncontrolled at rest, goes away when do something
concussion
usually sudden temporary loss of consciousness (no visible bruising)
contusion
bruising of brain; blood may enter subarachnoid space
laceration
tear; w/ bleeding in the brain & subarachnoid space (increased intracranial pressure)
reperfusion
when blood flow starts again after stopped (hard on tissues)
primary sensory cortex
- postcentral gyrus (parietal lobe)
- localizes sensations from posterior column system & spinothalamic tracts
primary visual cortex
- posterior occipital lobe
- tells patterns (color, shape, movement of visual stimuli) but no meaning
primary auditory cortex
- superior temporal lobe
- pitch, rhythm, loudness (physically describe sound)
association areas
where the primary impulses are translated into something meaningful
sensory- posterior to primary sensory cortex
visual- occipital lobe
auditory- temporal lobe
Wernicke’s Area
- interpretative speech (understanding)
- can interpret sounds into recognizable words
- temporal lobe
common integrative area
translated into something very meaningful (usually on left side)
primary motor cortex
precentral gyrus of frontal lobe
Broca’s Area
- expressive speech
- motor: coordination of laryngeal muscles, tongue, mouth, and breathing)
- premotor area of frontal lobe
- 97% of people= left hemisphere
frontal eye fields
- voluntary scanning movements of the eyes
- frontal lobe
electroencephalogram (EEG)
-summation of action & graded potentials recorded from specific areas of the brain
cranial nerve I
olfactory (sensory)
cranial nerve II
optic (sensory)
cranial nerve III
oculomotor (motor)
cranial nerve IV
trochlear (motor)
cranial nerve V
trigeminal (both)
cranial nerve VI
abducens (motor)
cranial nerve VII
facial (both)
cranial nerve VIII
auditory (sensory)
cranial nerve IX
glossopharyngeal (both)
cranial nerve X
vagus (both)
cranial nerve XI
spinal accessory (motor)
cranial nerve XII
hypoglossal (motor)
CVA (stroke)
- cerebrovascular accident
- 2 types:
1. clot blocks area leading to the brain (indicates symptoms)
2. hemorrhagic (blown aneurism)
TIA
transient (temporary) ischemic (lack of blood flow) attack
*mini stroke
Alzheimer’s Disease
tangles of TAU protein
agnosia
don’t know name/what it is (nostic=knowing)
apraxia
can’t figure out how to do something/can’t process it
aphasia
can think of words but can’t express them (associated w/ broca’s area)
encephalitis
inflammation/infection of the brain
