Chapter 1 Flashcards
Rostral means…
Rostral means toward the head end of the
body (toward the rostrum)
rostrum - a bodily part or process suggesting a bird’s bill: as
a : the beak, snout, or proboscis of any of various insects or arachnids
b : the often spinelike anterior median prolongation of the carapace of a crustacean (as a crayfish or lobster)
Caudal means…
caudal means toward the opposite end of the body
toward the tail
Dorsal means…
Toward the back
Ventral means…
toward the belly
In most animals, rostral-caudal corresponds to…
anterior-posterior
In the upright human anterior-posterior corresponds to…
being in the regions below the head, anterior-posterior corresponds to ventral-dorsal
We are moving LATERALLY, if…
If we move away from the midline
We are moving MEDIALLY, if…
if we move toward the midline
A transverse or frontal or coronal section is…
A cross section, cut at approximately right angles to the long axis of the brain
A parasagittal or sagittal section is…
A section cut parallel to the midline (as if the animal had walked forward into a whirling vertical saw blade)
A midsagittal section…
divides the brain exactly in half, and the left and right sides are fairly symmetric
A horizontal section is…
cut in a plane more or less at right angles to the other two
Oblique Sections…
a diagonal cross section attained by slicing, actually or through imaging techniques, the body or any part of the body or anatomic structure, in any plane that does not parallel the longitudinal axis or intersect it at a right angle, that is, that is neither longitudinal (vertical) nor transverse (horizontal).
Name major distinct subdivisions of the central
nervous system…
a. Endbrain (telencephalon)
b. ‘Tweenbrain (diencephalon)
a + b = Forebrain (prosencephalon)
c. Midbrain (mesencephalon)
d. Hindbrain (rhombencephalon)
e. Spinal cord
The Hindbrain is also known as…
The rhombencephalon
because of the rhombus shape you can see when looking at it from above
Encephalon means…
“ in the head ” in Greek
The Midbrain is also known as…
mesencephalon
Etymology: Gk, mesos, middle, enkephalos, brain
The forebrain (prosencephalon) includes:
a. Endbrain (telencephalon)
b. ‘Tweenbrain (diencephalon)
The Endbrain is also known as….
telencephalon
The ‘Tweenbrain is also known as…
diencephalon
The forebrain is also known as …
prosencephalon
From what kind of tissue develops the CNS?
It develops from the surface layer of the early embryo, the primitive ectoderm, the same layer that gives rise to the skin. So it is an ectodermal tissue.
What kind of tissues make up the muscles and skeleton?
the mesodermal tissues
What kind of tissues make up the internal organs?
the endodermal tissues
What is ectoderm?
The surface layer of the early embryo of a bilaterally symmetric animal, including the chordates. It forms the epidermis, the nervous system, and pigment cells. It also forms tooth enamel, the lining of the mouth, nostrils and anus, the sweat glands, hair and nails.
Primitive cellular mechanisms present in one-celled organisms and retained in the evolution of neurons:
- Irritability and conduction
- Specializations of membrane for irritability
- Movement
- Secretion
- Parallel channels of information flow; integrative activity
- Endogenous activity
Protozoa is:
a phylum or grouping of phyla which comprises the single-celled microscopic animals, which include amoebas, flagellates, ciliates, sporozoans, and many other forms. They are now usually treated as a number of phyla belonging to the kingdom Protista.
organisms of the Protozoa group.
During which stage only is movement(primitive cellular mechanism) characteristic of neurons?
During early developmental stages of the cells.
Mesoderm is…
The middle layer of the early embryo of a bilaterally symmetric animal. In chordates, it forms the notochord, the bones of the skeleton, muscle, connective and a few other tissues.
Endoderm
The innermost layer of the early embryo. It forms the linings of the two main tubes of the body—the digestive tract (alimentary canal) except for the mouth and anus, and the respiratory tract. Tissues derived from these two systems are also endodermal, including the thymus . thyroid and parathyroid glands, and parts of the auditory system.
Endogenous activity
Activity generated from within, without an external stimulus.
Metazoan animals…
any of a group (Metazoa) that comprises all animals having the body composed of cells differentiated into tissues and organs and usually a digestive cavity lined with specialized cells
Sponges…
Sponges are animals of the phylum Porifera (/pɒˈrɪfərə/; meaning “pore bearer”). They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. Sponges have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes.
Cnidarian…
any invertebrate animal, as a hydra, jellyfish, sea anemone, or coral, considered as belonging to the phylum Cnidaria, characterized by the specialized stinging structures in the tentacles surrounding the mouth; a coelenterate.
A clump of cells is called…
Ganglion
What is a root?
a bundle of nerve fibers, or axons, attached to the spinal cord
Dorsal root
One of two branches of each spinal nerve attached to the spinal cord. The dorsal branch—the dorsal root—contains axons of primary sensory neurons that synapse in the CNS on secondary sensory neurons. The peripheral axons of dorsal roots extend to receptors in the periphery (skin, joints, muscle, visceral organs). (The ventral root in vertebrates contains axons from motor neurons that extend to muscles, plus axons from the lateral horn to autonomic ganglia.)
What part of neuron forms its receptive portion?
Dendrites
Conductive portion of the cell is…
Axon
Synapse is named by who?
By the English physiologist Charles Scott Sherrington
from a Greek word meaning “ a joining together or touching ”
Telodendria is…
The axonal end branches
Where are the synaptic endings located?
On the telodendria, at tiny enlargements (end buttons, or boutons, from the French name boutons termineaux )
The transmissive portion of the neuron…
The telodendria
The three functional portions
of the cell:
receptive, conductive, and transmissive
Motor Neuron definition…
A CNS neuron with an axon that synapses with muscle or gland cells. Any CNS neuron with an axon that goes out of the CNS. If the axon connects with peripheral autonomic ganglion cells, it is called a preganglionic motor neuron.
The shape of the dorsal root ganglion cell of mammals is known as a…
pseudounipolar shape(is not found in all animals)
The depolarization in the dendrites and cell body is…
The depolarization in the dendrites and cell body is graded — greater with greater stimulation — and this effect diminishes with distance from the point of stimulation. We can say that the change is conducted, very rapidly, away from the site of stimulation in a decremental fashion. The farther from the point of stimulation, the smaller the change is.
Action potentials are conducted in what fashion?
Action potentials are conducted in a nondecremental fashion. Once a threshold level of depolarization is
reached, an action potential is triggered. Once triggered, the spike travels down the axon without diminution.
Evolution of what made action potential possible?
the evolution of voltage-gated ion channels
Even in which animal are action potentials found?
in jellyfish
Jellyfish are in which phylum and subphylum?
Phylum: Cnidaria
Subphylum: Medusozoa
Name major parts and activities of neurons
• Cell body (soma) and its branches (dendrites)
Membrane potential
The cell ’ s irritability: membrane depolarization when stimulated ( excitation )
Graded spread (conduction) of membrane potential change away from the point of stimulation
• Axon and its end arborization (telodendria) with synaptic contacts on other neurons or on muscle or gland cells
The axonal membrane is specialized for conduction of action potentials .
Action potentials are conducted in a nondecremental fashion.
Action potentials are found even in jellyfish. This specialization depended on the evolution of voltage-gated ion channels.
Many action potentials would cause so much sodium and potassium to move across the membrane that it would lose its polarization. What mechanism prevents that?
Sodium-potassium pump.(special proteins)
What does Sodium-potassium pump do?
An active pumping mechanism is constantly moving sodium ions out of the cell and bringing potassium ions (K + ) in. Three sodium ions are moved out when two potassium ions are moved in.
When artificially triggered somewhere in the middle of axon, spike or action potential travels in what direction?
It will travel in both directions.
This is what occurs when you strike your “ funny bone ” in the
elbow. The mechanical stimulation of the ulnar nerve triggers action potentials in many axons whose dendritic regions are in the hand and forearm, hence you feel a burning sensation in those regions although they were not actually stimulated.
Jawed vertebrates are all vertebrates except…
Hagfishes and lampreys
In jawed vertebrates Myelin sheath develops on all axons, except…
The smallest axons
Myelin is formed by which cells?
The membranes of glial cells (oligodendrocytes in the CNS and Schwann cells in the peripheral nervous system [PNS]).
(basically consists of proteins and phospholipids)
What does myelin do? and how does action potential spread in myelinated axons?
It blocks the flow of ions across the membrane except
at periodically placed nodes where it is absent. The result is a great increase in speed of the action potential, as the depolarization spreads decrementally very rapidly from one
node to another, triggering an action potential at each node. Thus, an action potential jumps from one node to the next, so the conduction is saltatory (jumping).
Does every single-celled organism move?
yes
Movement of single-celled creatures requires…
energy transfer to contractile proteins
How do amoebas move?
by control of cytoplasmic flow
How does paramecia move?
by the moving of cilia that protrude from the cell membrane.
Cilium - 1) წამწამი 2) შოლტი
What is called to the specialized contractile cells, which multicellular organisms have evolved in order to locomote or produce contractions for other purposes?
the muscle cells
What is actin and what does it do?
Growing neurons contain an abundance of contractile proteins, especially actin, in order to extend their long processes and to migrate during development
In the CNS which cells move, even in maturity?
the glial cells
the muscle cells, which accomplish this(contraction) by the interaction of two proteins…
actin and myosin
From what do actin and myosin obtain energy?
adenosine triphosphate (ATP) molecules
In the early years of twentieth century they thought that neural transmission was…
purely electrical in nature
Who demonstrated empirically that neural transmission is chemical?
Otto Loewi(won Nobel Prize)
Which neurotransmitter is released from the acceleretor nerve(heart) and what did Loewi call it in German?
noradrenaline, Acceleransstoff
Which neurotransmitter is released from the decelerator nerve(heart, branch of Vagus Nerve) and what did Loewi call it in German?
acetylcholine, Vagusstoff
Does electrical transmission also occur between neurons?
yes, but the contacts between cells where this happens are much less common than the sites of chemical transmission.
Different neurotransmitter and receptor combinations cause different effects on the
postsynaptic membrane: A small depolarization is called…
an excitatory postsynaptic potential (EPSP) because it moves the membrane closer to the threshold for triggering an action potential (at the beginning of the neuron ’ s axon, the axon hillock).
Different neurotransmitter and receptor combinations cause different effects on the
postsynaptic membrane: A small
hyperpolarization is called…
an inhibitory postsynaptic potential (IPSP) because it moves
the membrane away from the threshold
It has been discovered that a variety of peptides are also secreted along with the neurotransmitter
at many synapses. These peptides are called..
neuromodulators
Difference between electrical and chemical synapses…(physical)
Electrical synapses have no synaptic vesicles, and the synaptic cleft is much narrower
In which animals can electrical synapses be already identified?
in sponges
With which microscope can we see synapse?
with electron microscope(not with light microscope)
Gap junction is:
A junction between two cells that is characterized by close apposition of cell membranes with molecular channels that allow free passage of ions and other small molecules between cells. Electrical activity in the membrane of one cell influences the other cell without any special neurotransmitters or receptor molecules. In evolution, gap junctions constitute electrical synapses that appeared earlier than chemical synapses
What is called to axon’s enlarged ending?
the end buttons, or boutons from the French
Can a single bouton form only one synapse?
No. A single bouton can form a number of different synapses
What is Dendritic spine?
A dendritic spine (or spine) is a small membranous protrusion from a neuron’s dendrite that typically receives input from a single axon at the synapse. Dendritic spines serve as a storage site for synaptic strength and help transmit electrical signals to the neuron’s cell body. Most spines have a bulbous head (the spine head), and a thin neck that connects the head of the spine to the shaft(ღერო) of the dendrite. The dendrites of a single neuron can contain hundreds to thousands of spines. In addition to spines providing an anatomical substrate for memory storage and synaptic transmission, they may also serve to increase the number of possible contacts between neurons.
Types of synapses:
a) Axo-somatic
b) Axo-dendritic (to dendritic shaft or dendritic spine)
c) Axo-axonal
d) Reciprocal synapses
presynaptic inhibition
and facilitation
e) Serial synapses
gating mechanisms
f) Dendro-dendritic,
g)dendro-axonal synapses
Functional correlates of axo-axonal contacts(?):
If activity at an axonal ending causes a depolarization of another axon ’ s ending, then any action potential arriving at
that second axon ’ s ending will be reduced in size (because of the reduced membrane potential). The consequence is a reduced release of neurotransmitter, so the effect is called presynaptic inhibition . Similarly, an axo-axonal contact can cause presynaptic facilitation if it causes hyperpolarization.
Presynaptic facilitation…(and Inhibition)(?)
Increased excitatory effects of a synaptic terminal that occurs when the terminal receives axo-axonal synapses that when activated cause hyperpolarization of the membrane of the terminal. When a hyperpolarized terminal is depolarized by the arrival of an action potential, a greater amount of neurotransmitter is released—hence it’s effects are facilitated.
Cell Body is also known as…
Soma
Exocytosis is…
The process, when a cell releases a chemical into the surrounding intercellular fluid, as at a synapse.
Cells take up substances from the surrounding fluid. What is called to this process? and When does it occur?
Endocytosis
Endocytosis occurs around synaptic endings when the membrane of an axon takes up a neurotransmitter it has just released (called reuptake) or it takes up the breakdown products of the neurotransmitter if the neurotransmitter has been broken down by enzymatic action. Substances taken up at an axonal ending — not only neurotransmitters but other substances as well — are often transported up the axon to the cell body.
Which enzyme breaks down acetylcholine and therefore halts its action?
acetylcholinesterase
What is a retrograde transport?
The process of moving opposite to the direction of information flow in the axon. Retrograde transport is an active process involving the protein dynein.
Anterograde transport…
Anterograde transport is another form of intracellular transport of molecules and organelles. This movement involves the protein kinesin. It is used by the neuron to move molecules from the site of synthesis in the cell body to the endings of its axon.
In which animals does endogenous activity occur?
Endogenous activity occurs in all animals including Protozoa and Cnidaria.
Endogenous activity in contrast with reflexes….
is generated without any external stimulus
