neuro Test 2 Flashcards
Cauda equina
in subarachnoid space in lumbar and sacrum
Naming nerve roots
Run over the named vertebra until C7- where nerve runs under and is called C8 nerve root
Definition of a neurotransmitter- 4 points
- Synthesized by a neuron
- Accumulates in presynaptic terminals from which release occurs
- When released, produces same response as when exogenous source is applied
- Is removed from the synaptic cleft
4 categories of neurotransmitter
- Acetylcholine (Ach)
- Biogenic Amines
- Amino Acids
- Peptides
Acetylcholine (Ach)
major neurotransmitter of parasympathetic nervous system, both pre and post ganglionic.
also for sympathetic preganglionic neurons
used at neuromuscular junctions
in nuclei of the brain for learning, spatial and recognition memory. (Die in Alzheimers disease)
Biogenic amines
contain an NH2 group. norepinephrine, serotonin and dopamine.
Norepiniephrine
type of biogenic amine
neurotransmitter of postganglionic sympathetic neurons.
in CNS- localized to locus ceruleus in brain stem. function to modulate central sensory nuclei, activation of cerebral cortex, sympathetic preganglionic cell bodies in thoracic spine and paradoxical sleep
Serotonin
type of biogenic amine
works with norepinephrine and others for cyclical sleep patterns
Associated with Raphe nucleus- projects to large areas of CNS- cortical activation and modulation of many brain centers
Dopamine
type of biogenic amine
associated with Parkinsons (substantia nigra to the basal ganglia) and schizophrenia
associated with small nuclei in CNS that project to larger areas.- motor, cognitive, psychological well being.
Amino acids
Four common transmitters: Glutamate and Aspartate are excitatory (cause depolarizations). GABA and Glycine and inhibitory (inhibit depolarizations).
associated with memory formations, long term changes, neuroplasticity
Peptides
strings of amino acids linked by peptide bonds
modulatory in function. often work with other neurotransmitters- stored in synaptic vesicles with other neurotransmitters and released together.
have effects that are slower to develop, so can influence the postsynaptic cells response to next input
Stage 1: Release of Neurontransmitters
cell is depolarized by Na and K+ leaving cell. this causes the inflow of Ca2+. releases neurotransmitters
Stage 2: processing in the synaptic cleft
3 different mechanisms
- Neurotransmitters can be metabolized in the synaptic cleft by enzymes. Mostly Ach and peptides. Important- myasthenia gravis
- Neurotransmitters removed by an uptake protein. Mostly are amino acids and biogenic amines. Clinically- cocaine, MPTP, Parkinsons disease and dopamine, antidepressants- serotonin and norepiniephrine
- Removed by glial cells. major form for amino acids. excitatory amino acids can be toxic to the brain
Stage 3: Effect on postsynaptic cell
there must be a receptor for the neurotransmitter to bind to- two major categories of receptors
- Ligand gated ion channels-has a binding site for a particular neurotransmitter, when bound the ion channel will open. Nicotinic Ach is a good example of ligand gated
- G-coupled protein receptors- have a binding site for a particular transmitter. causes a cascade in the cell which can change the polarization of the membrane. Muscarinic Ach
Parasynaptic communication
neurotransmitters have to travel out of the synapse so find cells with proper receptors
do not have an immediate effect, used to enhance of attenuate other neurotransmitters
ex- enkephalin- runners high
Steps of sensory processing
- Transduction- form of physical energy stimulates receptors and creates action potentials
- Propagation of action potentials to the spinal cord or brainstem.
- Generation of a perception
Pacinian corpuscle
has a central, single nerve axon, that when deformed by pressure on the skin sends action potentials. the greater the force, the higher frequency of action potentials
Rapid adapting
Pacinian corpuscle and meissner’s corpuscle
only respond when filament is applied or removed
Slow adapting
Merkel cells and Ruffini endings
respong constantly to pressure
Hair follicles
free nerve endings that wrap around hair cells. rapid adaptors
Receptors responsible for 2 point discrimination
- Pacinian corpuscles and Ruffini endings have larger receptive fields
- Merkel and Meissners have small receptive fields
Vibration
Transduced by pacinian corpuscle. rapid adapting
Shape best by
Ruffini and Merkel
Movement of object across skin
Pacinian and Meissners
Texture of an object
Merkels
Mechanism of position sense
Muscle spindles
Cells of the muscle spindle
- Nuclear bag cells- type 1A neurons- annulospiral also innervate nuc chains. fast adapting
- Nuclear chain cells- have 1A and II fast and slower adapting. can tell a change in muscle length and what the new muscle length is.
Intrafusal fibers
gamma fusimotor nerves innervate it. so that it is always taught and able to respond to stretch.
Joint receptor- 4 types
found in peri-Articular tissues of synovial joints. used near end range of joint
- resemble ruffini, slow to adapt and easy to stimulate. in superficial layers of PROXIMAL joints, more active at end range
- Resemble Pacinian corpuscle, found in deeper layers of distal joints at end range.
- Found in ligaments of synovial joints except for spine. Hard to stimulate and slowly adapting.
Golgi tendon organ
transduce info about muscle tension. located at musculotendonous junctions.
innervated by type Ib nerve fibers
Pain receptors/free nerve endings
respond to tissue damage
use ion channels instead of deformation of a membrane around nerve
hyperalgesia- histamine and prostaglandin help in transduction process- blocked by NSAIDS
sensitization- second messenger induced phosphorylation- produces a larger response
mechanical- ENaC- sharp dull test
chemical- TRPV1-admits sodium and calcium ions in response to noxious heat, low pH, and certain chemicals ex. capsacin
thermal 5C- TRPV1,V2- ion flow in response to only heat.
Hot/cold receptors
1mm diameter areas on skin respond to either hot or cold.
linearly responsive to temperature but have a ceiling.
Cold- TRPM8, A1
Warm- TRVP3, 4
Deep tendon reflex
sensory nerves from muscle spindle are stimulated when strike to the tendon increases the length of the muscle.
type 1a nerve fibers convey action potentials to the spinal cord and synapse on motor neurons that innervate the same muscle that was tapped. both neurons involved have large diameter so happens quickly.
Tactile info entering spinal cord- 4 options
- Ascend without synapse
- Enter, synapse on dorsal horn and ascend dorsal columns
- Enter spinal cord, synapse on motor neurons
- Enter spinal cord, synapse on other neurons
Tactile sense from the body
Axons from the dorsal columns project to medulla where synapse on nucleus gracilis/cuneatus. cross in the mid medulla on internal arcuate fibers- decussation of the medial lemniscus. ascend on opposite side to ventral posterior lateral nucleus, then posterior limb of internal capsule to primary somatosensory cortex.
Nociceptive specific and wide range neurons- Lamina
Lamina I,V,VII,VIII
Pain senses from body
A delta or C fibers carrying pain info approach dorsal roots and central axons bifurcate to ascend/descend 1-3 spinal levels before entering the dorsal horn (dorsolateral fasciculus or Lisauer’s tract). use excitatory amino acids(glut/asp) and peptides as co-transmitters (substance P). synapse on nociceptive specific or wide dynamic range neurons in the dorsal horn lamina I,V,VII,VIII.
also could synapse on interneurons in lamina II.
Inter neurons in dorsal horn
live in lamina II of dorsal horn.
also called substantia gelatinosa
A delta or C fibers can synapse on them, then they synapse on other neurons in the dorsal horn
help to modulate the flow of pain and temperature info through the dorsal horn
3 components of anterolateral system
- Spinothalamic- perception and localization of pain
- Spinomesencephalic/hypothalamic- affective, emotional and autonomic response to pain
- Spinoreticular- arousing quality of pain
Spinothalamic
perception and localization of pain
from Lamina I and V to thalamus
crosses on anterior white commisure to ascend anterolateral system on opposite side, through posterior limb of internal capsule
Synapse on ventral posterior lateral nucleus and posterior nuclei of thalamus. then to primary somatosensory cortex