NeuroScience Quiz !

Acetylcholine

After Ach is released it binds with the postsynaptic Ach receptors to cause muscle depolarization The Ach then unbinds and is released into the synaptic cleft where it is hydrolyzed by acetylcholinesterase into acetate and choline The choline is taken back into the presynaptic membrane and recycled to form more Ach Action potentials generated in the motor nerve always release enough Ach to cause depolarization of the muscle

summation and action potentials

At any point in time, some areas of the nerve cell (dendrites, cell body) may be receiving IPSPs while others may be receiving EPSPs Whether an AP is generated at the axon hillock depends on the "summation" of all the IPSPs and EPSPs that are received by that cell at any given point in time

threshold stimulus

Nerve cells communicate with each other by affecting the RMP of adjacent nerve cterm-86ells causing excitation or inhibition of the adjacent cell

somites

differentiate into non-neural tissue such as muscle, bone, and ct.

L2

end of spinal cord

Nodes of Ranvier

facilitate conduction along myelinated nervesbecause action potentials are only generated at the Nodes, moving from node to node (jumping) which increases the speed of conduction

Prosencephalon

forebrain

Ependyma cells (CNS)

form a single layer of cells to line cavities of the CNS and form a barrier between CNS tissue and the cerebrospinal fluid (CSF). They have cilia which help promote the flow of the CSF, and may also aid in the production of CSF

Oligodendrocytes

form myelin in the CNS: just as the Schwann cells form the myelin in the peripheral nervous system, myelinate multiple axons rather than just a single axon like Schwann cells.

neurofibrils

form the cytoskeleton of a neuron and provide structure and nutrients

neural crest

formed by ectodermal cells and differentiates int a a number of different cell types

Notochord

forms the basis for the axial skeleton and persists as the nucleus pulpous

Serotonin

founds in pons and medulla and projects to other areas in the CNS. Modulates mood, emotion, sleep, appetite and pain. Action terminated by reuptake or metabolized by MAO.

exercise-associated muscle cramps

Repetitive muscle exercise results in local muscle fatigue, with an increase in muscle spindle output and a decreased output from the GTO. Some evidence shows cramping can be relieved by stretching the muscle or by electrically stimulating the tendon (GTO). Stretching the cramped muscle supposedly activates the GTO which inhibits the muscle to stop the cramp

Neural fold

fuses starting at lower cervical area and proceeds rostral and caudal. Open ends are neuropores that close about 24-26 days of gestation.

Endoderm

gastrointestinal tract and accessory organs, lungs

inferior colliculi

hearing

pia mater

helps form the blood Brian barrier along with astrocytes, capillary walls, and surface coving of neurons int the cns

Rhombencephalon

hindbrain

hyperpolarized

if it becomes more negative

Hypopolarized

if it becomes more positive

Axonontmesis

if the son is destroyed. Degeneration and regeneration usually take place since the neurilemma is not damaged. Leaves pathway for nerve to regenerate/find terminal organ.

Proprioceptors

in joints and muscles monitor changes in body position

extrafusal fibers

Striated muscle fibers , innervated by alpha motor neurons, shorten and lengthen the same as spindle muscle fibers

ventricular system

The CSF leaves the subarachnoid space through the arachnoid villi to enter the venous sinuses and then the general venous circulation

alpha motor neurons

The fibers that carry action potentials to cause skeletal muscle to contract are (can be excitatory and inhibitory)

nuclear bag

innervated by dynamic gamma fibers

nuclear chain

innervated by static gamma fibers

classification 1

interceptors, propioceptors, exteroceptors

Renshaw cells

interneuron that is activated when the alpha motor neuron is activated

Photoreceptors

involved in vision

primitive streak

is a structure that forms in the blastula during the early stages of avian, reptilian and mammalian embryonic development. It forms on the dorsal (back) face of the developing embryo, toward the caudal or posterior end. The presence of the primitive streak will establish bilateral symmetry, determine the site of gastrulation and initiate germ layer.

muscle spindle

is the primary receptor for length (static) and or length changes (dynamic) in muscle

corticospinal tract

moter and descending (efferent) pathways

mesoderm

muscles, bones, connective tissue, genitourinary tract

white matter

myelinated axons Anterior Funiculus Dorsal Funiculus Lateral Funiculus

Morton's Neuroma

nerve sprouts out in several different areas) involves a thickening of the tissue around one of the nerves leading to your toes. This can cause a sharp, burning pain in the ball of your foot. Your toes also may sting, burn or feel numb. Can also occur after amputation

neuroma

nerve tumor

ectoderm

nervous system and epidermis

potassium ions

primarily responsible for establishing the resting membrane potential (RMP) in the nerve cell !

precental gyrus

primary motor area

postcentral gyrus

primary sensory cortex

GABA

produces IPSPs or other inhibitory action; deactivation is by presynaptic reuptake - GABA agonists produce decreased CNS activity

pineal gland

produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles

primary vessicles

prosencephalon, mesencephalon, rhombencephalon develop at 4th week

Astrocytes

provide structural support, astrocytes have processes which surround blood vessels in the CNS which are selectively permeable and may thus function as part of the "blood-brain barrier"

A-delta free nerve endings

receptors for heat, cold, and pain

shunting

relieve pressure by removing csf

nociceptors

respond to pain and are primarily free nerve endings

Mechanoreceptors

respond to physical deformation, and include receptors for touch, muscle tension, and vestibular responses.

Thermoreceptors

respond to temperature changes

Neuroglia cells

astrocytes, oligodendrocytes, microglia, ependyma

middle temporal gyrus

audition

orthodromically

away from the cell body

trigger zone

axon hillock and initial segment

axon growth

axons grow about 1mm per day or 1 inch per month

dynamic stretching

contract a muscle and allow it to shorten or lengthen

static stretching

contract a muscle but does not allow it to change length

Wallerian degeneration

degeneration of the distal portion of the axon and myelin sheath. The nerve segment proximal to the site of injury degenerates back to the first node of Ranvier it encounters

Extroceptors

detect external stimuli

axon hillock

section of neuron which gives rise to the action potential

cunate and gracile tubercle

sensation (touch and pressure)

spinocerebellar tracts

sensory and ascending (afferent) pathways

tentorium cerebelli

separates the occipital lobes from the underlying cerebellum and upper structures of the brain stem

fall cerebri

separates the right and left hemispheres

arachnoid villi

sites where CSF diffuses (decreases) back into the bloodstream from the subarachnoid space

stretch reflex

spinal cord reflex, monosynaptic

Neural tube formation

starts with a neural plate composed of ectodermal tissue. The neural plate gradually folds into a neural groove and then further folding forms a neural fold on each side of the neural groove

all or none law

states that a stimulus must be threshold (ALL) or you will get no response (NONE) If you have a threshold stimulus, the action potential generated is always a constant voltage and velocity (40 to 60 m/sec; 50 m/sec = 112 mph). Electricity travels at 186,000 miles/sec or 669,600,000 mph

blood patch

sterile injecting a small amount of patients blood into the epidural space. usually will stop headache immediately. 1st is 70% and 2nd is 95% effective.

perineum

surrounds bundles of nerve fibers (fascicles)

Endoneurium

surrounds each nerve fiber

endomerium

surrounds individual nerve fibers

Epineurium

surrounds the nerve trunk

Prosencephalon

telencephalon and diencephalon

secondary vesicles

telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon. During the 5th week, the first and third vesicles change into two swellings so that there are now five secondary vesicles.

Neurotmesis

when both the axon and the neurolemma sheath are destroyed. Degeneration takes place, but regeneration is more difficult since the neurilemma sheath is destroyed.

L4-L5

where csf is drawn through a needle in the the subarachnoid space at. LUMBAR PUNCTURE. only peripheral nerves

Interceptors

which monitor changes in the body such as a change in blood pH

Acetylcholine

widely distributed in CNS, particularly cortical regions. Ach is an excitatory neurotransmitter in the CNS. Anticholingerics could affect both systems. (pnsand cns). is the transmitter substance for skeletal muscle depolarization.

action potential

§The Na+, rushing inward along with the intracellular K+, makes the inside of the cell positive, giving rise to the overshoot portion of the action potential. §The actual number of Na+ that move through the gates is small relative to the number of Na+ ions on the outside of the cell §Once the cell becomes positively charged inside by the Na+ inrush, the Na+ gates close aiding in the process of "repolarization".

refractory period

§The Na+-K+ pump re-establishes the exact resting membrane potential §From about 1/3 to 2/3 of repolarization, the nerve will respond to an above threshold stimulus, this is the relative refractory period- super stimulus will send signal again

resting membrane potential

-70mV

repolarization phase

1. A decreased inward conductance of Na+ 2. An increased outward conductance of K+ 3. The Na+-K+pump §Repolarization is almost entirely due to potassium outflow rather than the Na+-K+ pump (it's too slow) §The Na+-K+ pump re-establishes the exact resting membrane potential

Myelin

A layer of fatty tissue segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.

Excitatory Potential (EPSP)

A single stimulus arriving at a postsynaptic neuron does not produce an action potential in the postsynaptic neuron

gray matter

Anterior horn Posterior horn Lateral horn =neurons, cell bodies

Cerebellum

Balance and coordination

Microglia

are small cells found throughout the cns, and function as macrophages or scavenger cells

spina bifida occulta

Failure of the neuropores to close properly results in spina bifida which can include or exclude the spinal cord and meninges

spina bifida

Failure of the neuropores to close properly, which can include or exclude the spinal cord and meninges

cerebrospinal fluid

Fluid in the space between the meninges (subarachnoid space) that acts as a shock absorber that protects the central nervous system.

midbrain nerves

III and IV

medulla nerves

IX, X, XI, XII

papilledema

If the eye's blood vessels are blocked by increased CSF pressure this shows up on the back of eye by swelling (papilledema) in the area of the optic disk and is indicative of pathology such as hydrocephalus or tumor

inhibitory postsynaptic potential (IPSP)

If the incoming impulses are inhibitory then they will cause a transient, partial hyperpolarization

With nerve injury

Nissl substance becomes active to increasing protein synthesis in a process called chromatolysiswithin the nerve cell body

nerve regeneration

Schwann cells produce regeneration tube to direct regrowth of axon CNS neurons cannot regenerate. Regenerated axons have decreased internodal distances causing the nerve conduction velocity to be about 80% of the original

Golgi tendon organs

Sensory receptors that sense tension and are involved in reflexes that help maintain posture, innervated by myelinated Ib fibers

threshold stimulus

The minimal strength required to cause a contraction-- local response

Depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive. The concentration of extracellular Na+ determines the magnitude (i.e. voltage) of the action potential

unmyelinated nerves

Unmyelinated axons are embedded in a single layer of a Schwann cell but do not have a wrapping of the Schwann cell. Unmyelinated neurons do not have nodes

pons nerves

V, VI, VII, VIII

Ohm's Law

V=IR

lateral ventricles

Ventricles located in each cerebral hemisphere.

epidural hematoma

a collection of blood in the space between the skull and dura mater

two primary afferents for pain

a delta fibers and c fibers

neurons

a nerve cell; the basic building block of the nervous system

hydrocephalus

abnormal accumulation of fluid (CSF) in the brain. blockage of CSF circulation, increased production of CSF, or decreased absorption of CSF.

dopamine

abundant in the substantia nigra and involved in motor control.

Spina bifida with meningocele

an enlargement of the subarachnoid space and an accumulation of spinal fluid, no neural tissue

spina bifida with myelomeningocele

an enlargement of the subarachnoid space, but also includes neural tissue

Dendrites

are afferents conducting impulses towards the cell body that receive input from other nerve cells through synapses

Axons

are efferents conducting action potentials away from the cell body and towards an effector organ or structure such as muscle

Chemoreceptors

are involved in sensations such as taste, smell and changes in blood pH.

Fasiculi

bundles of muscle fibers gracile fasiculus (lower extremities), cunate fasiculus (upper extremest)

Normal pressure hydrocephalus

can develop in adults. problem with absorption of csf. OFTEN RESULTS IN GAIT INSTABILITY, URINARY INCONTINENCE AND DEMENTA

a delta fibers

carry sharp pain (lightly myelinated)

Norepinephrine

cell bodies found throughout the brainstem and project to other areas of the CNS. Activation of NE pathways increase alertness and increase blood pressure. Action terminated by reuptake or metabolized by MAO or COMT.

neuromeres

cellular condensations develop into nuclei

classification 2

chemoreceptors, photoreceptors, thermoreceptors, mechanoreceptors, nociceptors

Where is CSF produced?

choroid plexus

subdural hematoma

collection of blood under the dura mater

Nissl substance

combination of rough endoplasmic reticulum and free ribosomes responsible for the synthesis of proteins and other compounds important in nerve regeneration following a nerve injury

Synapse

compromised of a presynaptic membrane, a synaptic cleft, and a postsynaptic membrane

arachnoid mater

lies beneath the dura and above the Pia and arachnoid maters. surrounds the entire CNS and acts as a sac (i.e. subarachnoid space) within which is the cerebrospinal fluid

C fibers

long, dull pain (unmyelinated)

Neurapraxia

loss of conductivity only affecting myelin. recovery occurs in 10 days to 3 weeks often caused by prolonged pressure on a nerve. changes in sensation but doesn't permanently damage the nerve.

touch is mediated by

meissners corpuscles, merkels discs, free nerve endings

Rhombencephalon

metencephalon and myelencephalon

Mesencephalon

midbrain

neural tube

neural folds fused together. This closure proceeds until only the ends of the neurotube remain open. These open ends are termed the anterior and posterior neuropores. These neuropores normally close at about the 24th and 26th days, respectively. The neural tube eventually becomes the brain ventricles and the central canal of the spinal cord

Cytoskeleton

neurofibrils, microfilaments, microtubules

brain tissue

not sensitive to pain

intrafusal fibers

nuclear bag (fibers bunched together) and nuclear chain (linked and elongated)

spatial summation

occurs if a number of EPSPs arrive on different parts of the neuron at the same time- lots of different neurons bringing signals

temporal summation

occurs when the frequency of arriving EPSPs increases at a synapse

pressure mediated by

pacinian corpuscles, ruffians corpuscles, meisnners corpuscles, and merkels discs

Midbrain

part of the brainstem that passes through the tectorial notch and the foramen magnum of the skull

neuromuscular junction

point of contact between a motor neuron and a skeletal muscle cell

Ancephaly

the anterior neuropore failed to close, and the brain did not develop normally. This condition is usually not compatible with life

nerve conduction

the larger the axon diameter, the lower the threshold for excitation

intrafusal fibers

the muscle fibers found within a muscle spindle, innervated by gamma motor neurons

If there are enough EPSPs

the neuron will reach threshold and an AP will be generated at the trigger zone and travel down the axon

dura mater

thick, outermost layer of the meninges and adheres to the surrounding bony skeleton

Meninges

three protective membranes that surround the brain and spinal cord

antidromically

towards the cell body

angular gyrus

transforms visual representations into an auditory code

superior colliculus

vision

recepter physiology

§The Pacinian corpuscle has concentrically arranged layers of connective tissue which surround the sensory nerve ending (i.e. encapsulated) §The Pacinian corpuscle's sensory nerve is myelinated and contains nodes of Ranvier §The resting membrane potential is established across the nerve membrane by the relative concentrations of extracellular Na+ and intracellular K+ as in any nerve §When the Pacinian corpuscle is stimulated by a mechanical stimulus (i.e. pressure), the corpuscle is deformed and the deformation is transformed into an electrical impulse initiated by Na+ ion flow across the membrane

Spindle innervation

§The primary or annulospiral endings are sensory fibers which innervate both bag and chain fibers §These afferent endings wrap around the intrafusal fibers near the middle of the fiber §Primary afferents are sensitive to bothdynamic (phasic) and static (tonic) stretching of the intrafusal fibers, particularly the dynamic component §The primary afferents are large diameter myelinated fibers and are classified as Type Ia fibers

unmyelinated nerve conduction

§When an AP is generated it causes a small area of the nerve to depolarize, this creates a "relative" negative charge on the outside of the nerve (current sink) §Because of this "relative" negative charge area, positive charges are drawn from an adjacent area of the nerve to the area of negative charge in an effort to repolarize the depolarized area §As the adjacent area loses positive charges, it depolarizes §Through this mechanism one area of the nerve is repolarized as an adjacent area is depolarized. The action potential travels down the nerve generating a "new" action potential at each point

Calcium's role

§When an AP reaches the axon terminal, Ca++ diffuses through channels in the presynaptic membrane §Ca++ binds transmitter vesicles to the presynaptic membrane §The presynaptic membrane then opens upand the transmitter substance is released into the cleft §The vesicle becomes part of the presynaptic membrane and may be recycled to once again carry more transmitter substance

myelinated nerve conduction

§similar to unmyelinated conduction except that action potentials can only be generated at the Nodes of Ranvier §Action potential generation "jumps" from one node to the next §Because of this myelinated nerves conduct impulses about 50 times faster than unmyelinated nerves A new AP is generated at each node! Faster than unmyelinated