Intro & Basics Flashcards
Neurons
Primary processors of neural signals
What do Neuroglia support?
Support the electrical and chemical functions of neurons
Vascular endothelium
Provides for the supply of blood to brain tissue
Fundamental unit of function in the CNS
Neurons
3 zones of functional microanatomy of neurons
Input zone: Dendrites, Cell Body
Conducting Zone: Axon
Output Zone: Synapses, Axon Terminal
Dendrite
A neuronal process arising from the nerve cell body that receives synaptic input.
Morphology of the dendrite gives some insight into…
The functional properties of those cells and the class of neuron
Example: the absence of dendritic spines (smoothness) is evidence of an inhibitory effect on the cells that they make synaptic connections to.
Axon
The neuronal process that carries the action potential from the nerve cell body to a target.
electrical synapses
Synapses that transmit information via the direct flow of electrical current at gap junctions.
chemical synapses
Synapses that transmit information via the secretion of chemical signals (neurotransmitters).
gray matter refers to
any accumulation of cell bodies and neuropil in the brain and spinal cord (e.g., nuclei or cortices)
What is white matter
refers to areas of the central nervous system (CNS) that are mainly made up of myelinated axons
Give 4 examples of different classes of neurons
Cortical pyramidal cell
Retinal bipolar cell
Cerebellar Purkinje cells
Retinal Ganglion cells
Afferent
A neuron or axon that conducts action potentials from the periphery toward the central nervous system (coming in to CNS)
Efferent
A neuron or axon that conducts information away from the central nervous system toward the periphery
Interneuron
AKA: local circuit neuron.
Technically, a neuron in the pathway between primary sensory and primary effector neurons;
more generally, a neuron whose relatively short axons branch locally to innervate other neurons.
Brainstem is comprised of
Midbrain
Pons
Medulla
diencephalon
(location)
(Comprises)
Portion of the brain that lies just rostral to the midbrain; comprises the thalamus and hypothalamus
Rostral
Anterior, or “headward.”
anterior
Toward the front;
sometimes used as a synonym for rostral, and sometimes as a synonym for ventral.
caudal
Posterior, or “tailward.”
Posterior
Toward the back;
sometimes used as a synonym for caudal or dorsal.
Neuroglia provides these functions for the brain:
- Support the metabolic and signaling functions of neurons
- Participates in neuron circuit formation and synaptic plasticity
- Make myelin (axonal insulation)
- Contribute to formation of blood-brain barrier
- Participate in inflammatory response in injured neural tissue
- Contribute to the formation of scar tissue in damaged brain and spinal cord
Types of glial cells
Astrocyte
Oligodendrocyte
Microglial Cells
Astrocyte
(Found in)
(Assists with)
(Contributes to)
Found
+in gray matter
Assists with
+ionic balance of extracellular fluids,
+Take-up and process neurotransmitters from synaptic clefts
+formation of new synapses and circuits
Contributes to
+formation of blood-brain barrier and brain-ependymal barrier
+scar formation in necrotic neural tissue following injury
Oligodendrocyte
(Found in)
(Present)
(Subject to)
- Found in white matter and form myelin
- Present antigens that influence the outgrowth of axons in developing and recovering brain
- Subject to immunological attack in diseases of the CNS (e.g., multiple sclerosis)
Myelin
- Insulate axons by with layers of membrane that wrap around axon segments
- Decreases “leakiness” of the membrane, making the current more efficient
Nodes of Ranvier
Gaps between myelin segments that allow for the economical concentration of ion channels and ion pumps that are necessary for electrical signaling in axons.
Microglial cells
what are they and what are they derived from?
- Special type of mononuclear phagocyte that resides in the CNS
- Derived from hematopoietic precursor cells that migrate into the brain during development
Phagocyte
A type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles
Haematopoiesis
The formation of blood cellular components
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells.
Microglial cells exist in two forms
Amoeboid (activated state) and ramified (dormant state)
Activated microglia secrete…
Cytokines (signaling molecules) that modulate local inflammatory responses
Glial stem cells
Subset of astrocytes located near the ventricles
May give rise to more stem cells, mature astrocytes or oligodendrocytes, or mature neurons
Blood-brain barrier
Specialized permeability barrier between capillary endothelium and extracellular space in neural tissue
Blood-brain barrier is formed by
Tight junctions between capillary endothelial cells and surrounded by astrocytic foot processes
Blood-brain barrier excludes
Large water soluble molecules from freely diffusing into the central nervous system as well as certain pathological microbes and toxic compounds that might otherwise enter the brain
Superior (dorsal)
Top part
Inferior (Ventral)
Lower part
cephalic flexure with regard to direction
Brainstem runs off at a 120 degree angle relative to the plain of the forebrain. Below this point of flexure positional terms are applied a different way
Neuron classification by shape
Unipolar-have one process that includes both the axon and dendrite.
Bipolar-have two processes, the axon and a dendrite.
Multipolar cells-more than two processes, the axon and two or more dendrites.
Unipolar cells in humans
True unipolar cells are only found in invertebrate animals, so the unipolar cells in humans are more appropriately called “pseudo-unipolar” cells. Invertebrate unipolar cells do not have dendrites. Human unipolar cells have an axon that emerges from the cell body, but it splits so that the axon can extend along a very long distance.
Bipolar cells are found in…
in the olfactory epithelium (where smell stimuli are sensed), and as part of the retina.
Bipolar cells are not very common.
In the peripheral nervous system, the cells that elaborate myelin are called
Schwann cells
Neuropil
the region between nerve cell bodies where most synaptic connectivity occurs.
neural circuits
Organization of neurons working together to provide the foundation of sensation, perception and behavior.
A simple example of a neural circuit is the ensemble of cells that subserves the
myotatic spinal reflex (the “knee-jerk” reflex
two basic approaches to measuring the electrical activity of a nerve cell
extracellular recording (also referred to as single-unit recording),
intracellular recording
Extracellular recordings primarily detect
action potentials
action potential
The electrical signal conducted along axons (or muscle fibers) by which information is conveyed from one place to another in the nervous system.
Intracellular recordings can detect
smaller, graded potential changes that trigger action potentials,
These graded triggering potentials can arise at either sensory receptors or synapses and are called receptor potentials or synaptic potentials, respectively
The central nervous system comprises the
Brain and spinal cord
The peripheral nervous system (PNS) includes the
sensory neurons that link sensory receptors on the body surface or deeper within it with relevant processing circuits in the central nervous system
Systems of he peripheral nervous system
Autonomic (Visceral) Nervous System
Somatic Nervous system
Peripheral axons are gathered into bundles called_____;
nerves
Those nerve cell bodies that reside in the peripheral nervous system are located in _____
Ganglia
In the central nervous system, nerve cells are arranged in two different ways.
Nuclei: local accumulations of neurons having roughly similar connections and functions
Cortex (cortices): sheet-like arrays of nerve cells
autonomic nervous system
(consists of)
(concerned with)
Consists of sympathetic and parasympathetic divisions.
concerned with the regulation of smooth muscle, cardiac muscle, and glands
parasympathetic nervous system ganglia are found…
within the organs they innervate.
Sympathetic nervous system ganglia lie along or in front of the ________ and send their axons to _______
vertebral column;
a variety of peripheral targets
enteric system
made up of small ganglia as well as individual neurons scattered throughout the wall of the gut.
7 parts of the CNS
- spinal cord,
- medulla,
- pons,
- cerebellum,
- midbrain,
- diencephalon,
- cerebral hemispheres
Ventricles
fluid-filled spaces
What structures surround the 4th ventricle?
Medulla and pons
encloses the 3rd and lateral ventricles
diencephalon and cerebral hemispheres
What are the three types of brainstem motor nuclei and what do they project to?
somatic motor nuclei: project to striated muscles
branchial motor nuclei: project to muscles derived from embryonic structures
visceral motor nuclei: project to peripheral ganglia that innervate smooth muscle or glandular targets
Explain how the myotatic reflex functions
knee-jerk response
Hammer tap stretches tendonstretches sensory receptors in leg extensor muscleSensory neuron excites motor neuron in the spinal cord and spinal interneuron which inhibits motor neuron to flexor muscles Motor neuron conducts action potential to synapses on extensor muscle fibers, causing contraction (Flexor muscle relaxes because it was inhibited)Leg Extends
Axons in the central nervous system are gathered into
Tracts
Tracts that cross the midline of the brain are referred to as
Commissures
Neurons of the enteric system influence _____ and _____
gastric motility; secretion.
