Neuroscience- 1 Flashcards
Basic bio review
The human nervous system comprises two kinds of cells
Neurons
Glia
The human brain contains approximately \_\_\_\_\_\_\_\_ individual neurons. \_\_\_\_ in cerebral cortex. \_\_\_\_ in cerebellum. \_\_\_\_spina cord.
- 100 billion
- 12-15 billion
- 70 billion
- 1 billion
Santiago Ramón y Cajal
In the late 1800s, the Spanish investigator Santiago Ramon y Cajal (1852-1934) was the first to demonstrate that the individual cells comprising the nervous system remained separate
àHe showed that they did not merge into each other (as previously believed)
The Structures of an Animal Cell
– Membrane – Nucleus – Mitochondria – Ribosomes – Endoplasmic reticulum
Membrane
separates the inside of the cell from the outside environment
Nucleus
contains the chromosomes (DNA)
Mitochondrion
performs metabolic activities and
provides energy
that the cells require
-requires fuel & oxygen to function
Ribosomes
sites at which the cell synthesizes new protein molecules
Endoplasmic reticulum
network of thin tubes that transports newly synthesized proteins to their
location
*-ribosomes may be attached to ER
Components of Most Neurons
- Dendrites
- Soma (cell body)
- Axon
- Presynaptic terminals
Dendrites- 3 points
Branching fibers with a surface lined with synaptic receptors: responsible for bringing information into the neuron
• Some also contain dendritic spines that further branch out and increase the surface area of the dendrite
The greater the surface area of the dendrite, the more information it can receive
Cell Body/Soma- 3 points
.Contains the nucleus, mitochondria, and ribosomes
• Responsible for most of the metabolic work of the neuron (energy production)
• Covered with receptors (synapses) on its surface (in
many
neurons)
Axons- 3 points
-Thin fiber(s) of a neuron responsible for transmitting nerve impulses to other neurons, organs, or muscles.
• May have a myelin sheath, an insulating material that contains interruptions in the sheath known as nodes of Ranvier
• Presynaptic terminals (at the end points of an axon) release chemicals (neurotransmitter (NT))
to communicate with other neurons
Types of Signaling- 3
Affervent, Effervent, Interneurons or intrinsic
Interneurons or intrinsic
neurons are those whose dendrites and axons are completely contained within a single structure
Affervent
SENSORY- conducting or conducted inward or toward something (for nerves, the central nervous system; for blood vessels, the organ supplied).
Effervent
MOTOR-conducted or conducting outward or away from something (for nerves, the central nervous system; for blood vessels, the organ supplied).
“efferent neurons carry impulses outwards to the effector organs”
Variations Among Neurons
The function is closely related to the shape
of a neuron
– Example: Purkinje cells of the cerebellum branch extremely widely within a single plane
The Blood-Brain Barrier (BBB)
• Surrounds the brain and blocks most chemicals from entering
– The immune system destroys damaged or infected cells throughout the body
(cells can regenerate)
– Because neurons in the brain
generally do not regenerate, it is vitally important for the BBB to block incoming viruses, bacteria, or other harmful material from entering
Active Transport
The protein-mediated process that expends energy to pump chemicals from the blood into the brain
– Glucose, certain hormones, amino acids, and a few vitamins are brought into the brain via active transport
Astrocytes - 5 points
Type of Glia - Branches surround axon terminals • Absorbs released NTs • Temporarilyinhibits connected axons • Ceasesinhibition • Axons respond again in synchrony
Microglia- 2 points
– Remove waste material, viruses, and fungi from the brain (immune response)
– Account for 10-15% of all cells found within the brain (20% of glial cells)
Oligodendrocytes- 2 points
-in the brain and spinal cord) and Schwann cells (in the periphery of the body)
– build the myelin sheath that surrounds and insulates certain vertebrate
axons
Radial glia- 2 points
– Guide the migration of neurons and the growth of their axons and dendrites during embryonic development
– When embryonic development finishes, most radial glia differentiate into neurons and a smaller number differentiate into astrocytes and oligodendrocytes
Ependymal Cell
Secretes cerebrospinal (CSF)
Nourishment of Vertebrate Neurons- 2 points
• Vertebrate neurons depend almost entirely on glucose
= A sugar that is one of the few nutrients that can pass through the BBB
• Neurons need a steady supply of oxygen
– 20% of all oxygen consumed by the body is used by the brain
Thiamine
The body needs a vitamin, thiamine, to use glucose.
Thiamine deficiency
Prolonged thiamine deficiency leads to death of neurons as seen in Korsakoff’s syndrome, a result of chronic alcoholism and/or poor diet
– Korsakoff’s syndrome is marked by severe memory impairment
Organization of the Nervous System
Central nervous system (CNS)
the brain and the spinal cord
Organization of the Nervous System
Peripheral nervous system (PNS)
connects the brain and spinal cord to the rest of the body
– Somatic nervous system: consists of axons conveying messages from the sense organs to the CNS and from the CNS to the muscles & glands.
– Autonomic nervous system: neurons
© CengagetLheaarnintg c20o16 ntrol the heart, intestines, and other organs
The Spinal Cord
CNS
The part of the CNS found within the spinal column
-Communicates with the sense organs and muscles, except those of the head.
Bell Magendie law- 4 points
The part of the CNS found within the spinal column
– Communicates with the sense organs and muscles, except those of the head.
– Entering axons = dorsal roots: carry sensory information from organs
– Exiting ventral roots carry motor information to muscles and glands
Spinal cord - Consists of two types of matter
Grey and white
Gray matter
located in the center of the spinal cord and is densely packed with cell bodies and dendrites
White matter
in the periphery, composed mostly of myelinated axons
that carry information from the gray matter to the brain or other areas of the spinal cord
PNS: The Autonomic Nervous System
Sends and receives messages to regulate the automatic behaviours of the body (heart rate, blood pressure, respiration, digestion, etc.)
• Divided into 2 subsystems:
– The sympathetic nervous system
– The parasympathetic nervous system
The Sympathetic Nervous System- 4 points
• “Fight or Flight” response system • A network of nerves that prepares the organs for rigorous activity – Increases heart rate, blood pressure, respiration, etc. – Composed of ganglia on the left and right of the spinal cord
The Parasympathetic Nervous System- 4 points
• Facilitates vegetative, nonemergency responses
– Decreases functions increased by the sympathetic nervous system
– Composed of long preganglion axons extending from the
spinal cord and short postganglionic fibers that
attach to the organs themselves
– Dominant during our relaxed states
