PT 5416 EXAM 1

Neural tube formation

Neuron/cells develop from the dorsal ectoderm and form a neural plate; neural plate sinks down to form neural groove; epidermis covers it and spreads out, creating a neural tube

First neurons produced

Produced in neural tube 4-20 weeks in; create synaptic connects amongst each other

Apoptosis

Programmed cell death

Rostral end of neural tube

Creates the brain; remainder becomes the spinal cord

Lumen of the neural tube

becomes the ventricular system of the brain and the central canal of the spinal cord

Primary stage of brain development (Weeks 0-3)

From rostral to caudal:

Prosencephalon

Mesencephalon

Rhombencephalon

Prosencephalon

Most rostral portion of the brain in the primary stage of development; becomes the forebrain

Mesencephalon

Middle portion of the brain in the primary stage of development; becomes the midbrain

Rhombencephalon

Most caudal portion of the brain in the primary stage of development; becomes the hindbrain

Secondary stage of brain development

From rostral to caudal:

Telencephalon

diencephalon

mesencephalon

metencephalon

myelencephalon

Telencephalon

Part of the prosencephalon in the secondary stage of development; becomes cerebral hemispheres

Diencephalon

Part of the prosencephalon in the secondary stage of development; becomes the thalamus, epithalamus, hypothalamus, and subthalamus

Metencephalon

Part of the rhombencephalon in the secondary stage of development; becomes the pons and cerebellum

Myelencephalon

Part of the rhombencephalon in the secondary stage of development; becomes the medulla oblongata

Spina bifida

Neural tube defect where the caudal portion of the neural tube fails to develop/close properly; affects spinal cord and vertebral bones and can be caused by lack of folic acid during development

Spina bifida occulta

small gap in spine; mildest variation of defect

Meningocele

Meninges protrude through but spinal cord is still inside, sac fills with CSF; moderate variation of this defect

Myelomeningocele

Meninges and spinal cord both protrude through, sac fills with CSF; most severe variation of this defect

Ancephaly

Neural tube defect where the fold does not fuse at the rostral end and the brain does not fully develop; missing forebrain, cranial vault, and scalp; 1 in 1000 and fatal

Nervous system

Detects changes, makes decisions, stimulates muscles and glands to respond, and maintains homeostasis

Central nervous sytem

Major division of the nervous system containing the brain and spinal cord

Peripheral nervous sytem

Major division of the nervous system containing cranial and spinal nerves

Neurons

React to changes and send nerve impulses for communication

Neuroglia (glial cells)

Surround, support, and nourish neurons; help maintain the BBB

Astrocytes

Glial cell type in the CNS connecting neurons to blood vessels; exchanges nutrients and growth factors

Oligodendrocytes

Glial cell type in the CNS; creates myelin and provides structural support

Microglia

Glial cell type in the CNS; responds to immunological signals and clears toxic material; structural support

Ependymal cells

Glial cell type in the CNS; creates CSF and lines central canal of spinal cord and brain ventricles

Schwann cells

Glial cell type in the PNS; act as insulators encasing axons in myelin sheath

Soma/cell body

Central part of neuron containing the nucleus, cytoplasm, organelles, neurofilaments, and enzymes; responsible for protein transport and maintaining critical cell function

Dendrites

Branchlike parts of a neuron that are specialized to receive information from other neurons; increases cell surface

Axons

Transmits impulses and releases neurotransmitters to other neuron or effector; 1 per neuron

Multipolar neurons

A neuron with many processes; most common type + most neurons of CNS

Bipolar neurons

A neuron with two processes; eyes, ears, nose

Unipolar neurons

A neuron with one process; cell bodies are in ganglia; sensory neurons

Sensory neuron

Brings in information afferently towards CNS; unipolar

Interneuron

Links neurons together; multipolar

Motor neuron

Brings in information efferently away from CNS; multipolar

Convergence

one neuron receives input from several neurons

Divergence

one neuron sends impulses to several neurons

Presynaptic

referring to the region of a synapse that releases neurotransmitter

Postsynaptic

referring to the region of a synapse that receives and responds to neurotransmitter

Synaptic cleft

The narrow gap that separates the presynaptic neuron from the postsynaptic cell.

Multiple sclerosis (MS)

Autoimmune response that attacks CNS myelin sheath; scars develop to stop nerve impulses

Impulse conduction

Transmission of electrical signals along neurons.

Excitatory response

Brings membrane potential to threshold, increasing the likelihood of generating action potential

Inhibitory response

Moves membrane potential farther from threshold, decreasing likelihood of generation action potential

Membrane potential needed for action potential fire

-55mV

Resting membrane potential of a neuron

-70mV

Neurotransmitters

Chemical messengers that neurons use to transmit signals across a synapse to target cells; >100

Neuroscience

a relatively new science concerned with the development, chemistry, structure, function, and pathology of the nervous system; started in the 1800s

Nucleus/ganglion

a large number of cell bodies grouped together

Cortex

The outer layer of the brain of both the cerebrum and cerebellum; composed of gray matter; "frosting on a cake"

Peduncle

A large bundle of axons that physically connects one structure to another

Commissure

A group of axons travelling together to cross a midline

Tract

A bundle of axons having a common origin, destination, and function

Pathway

A route through which information travels, usually involving connections among multiple neurons

Lamina

A thin layer of white matter spreading nuclei or sub-nuclei in gray matter

Mesial

An inner surface formed by the apposition of two structures; in the nervous system, most commonly used along the midline where left/right parts of the brain touch

White matter

Area containing a lot of axons; inner portion of brain, outer portion of spinal cord

Gray matter

Area with a lot of cell bodies; outer portion of brain, inner portion of spinal cord

Spinal cord

An elongated structure that joins the medulla at its rostral end and spreads until the lumbar column of the spine; home of hard-wired reflexes, main voluntary neurons for movement

Motor cortex

an area at the rear of the frontal lobes that controls voluntary movements

PET scan (positron emission tomography)

Used to assess blood flow, oxygen or glucose metabolism, or receptor location

CT scan (computed tomography)

Used to investigate suspected strokes or increased intracranial pressure

BOLD MRI ( blood-oxygen-level-dependent magnetic resonance imaging)

Average brain activation during a complex finger-tapping task in a group of healthy subjects

DTI Scan

Measures the movement of water and generates an image of tracts that connect parts of the nervous system

Functional MRI (fMRI)

Used for information about changes in blood flow that occur in a second or less

TMS stimulation

Stimulates brain activity without opening the skull

Signs

Objected abnormalities detected on examination; What you can see

Symptoms

Subjective experiences resulting from the disorder; What patients report but doctor cannot see

Negative manifestations

Loss of function; can reflect damage to neurons, glial cells, or myelin; i.e. loss of memory or weakness of eye muscles

Positive abnormalities

inappropriate excitation, e.g. seizures, spasticity

Syndromes

A constellation of signs and symptoms frequently associated with each other; suggests a common origin

Modular organization of brain and spinal cord

Makes it straightforward to diagnose neurological disorders on the basis of history and neuro examination

Focal pathology

Causes signs and symptoms based on a single,

geographically continuous lesion;

i.e. Stroke - ischemia of a select territory

Multifocal pathology

Damage to the nervous system at multiple separate sites

Diffuse process/Diffuse dysfunction of the nervous system

Produced by toxins and metabolic abnormalities, causing dysfunction throughout the nervous system, as in alcohol intoxication

Rostral

Closest to head

Caudal

Toward the tail

Rostrocaudal Localization

Placement of lesion within the head-to-tail axis of the nervous system; clinician must identify affected nuclei, fiber tracts, and consider involved structures

Transverse localization

Placement of lesion within the cross-sectional view of the brain and spinal cord

Brainstem

Connects brain to spinal cord and regulates vital functions; midbrain, pons, and medulla (1 in. each)

Midbrain

Most rostral part of the brainstem; bundles of fibers connecting lower brain stem/spinal cord with higher brain centers

Cerebral aqueduct

a narrow tube interconnecting the third and fourth ventricles of the brain to allow CSF to flow through

Cerebral peduncles

Connects brainstem to cerebral hemispheres

Corpora quadrigema/Tectum

Reflex centers involving vision and hearing; 4 colliculi

Superior colliculi

Reflex movements of eyes, head, neck in response to visual stimuli

Inferior colliculi

Reflex movements of eyes, head, neck in response to auditory stimuli

Structures found only in superior colliculus

Red nucleus and substantia nigra

Substantia nigra

Major dopamine center; Reward, learning, and voluntary movement; neuron contains neuromelanin thought to be the byproduct if dopamine production

Parkinson's disease

Degeneration of melanin-containing cells; lighter color means less neuromelanin

Tegmentum

Site of reticular formation; contains most of brainstem nuclei

Red nucleus

Large nucleus only visible at level of superior colliculus; major role in movement coordination

Rubrospinal tract

Major role in coordination and tone; stimulates flexors, inhibits extensors

Lesion above red nucleus

Decorticate; flexed arms, extended legs

Lesion below red nucleus

decerebrate; arms extended

Pons

Relays nerve impulses between the cerebrum and cerebellum; helps regulate breathing with medulla

Vestibulospinal tract

Facilitates extensor activity, inhibits flexor activity to maintain balance

Pontine nuclei

Scattered gray matter in ventral pons; interspersed among descending corticospinal fibers; motor tracts to cerebellum via motor cortex