Lecture 2 Flashcards
Your mental experiences depend on what?
Activity of a huge number of separate but interconnected cells.
What kinds of cells comprise the human nervous system?
Neurons
Glia
The human brain contains approximately how many neurons?
86 billion individual neurons
What are the structures of an animal cell?
Membrane Nucleus Mitochondria Ribosomes Endoplasmic Reticulum
What structre seperates the inside of the cell from the outside environment?
Membrane
What structure contains the chromosomes?
Nucleus
What structure performs metabolic activities and provides energe that the cells require?
Mitochondrion
What are the sites at which the cell synthesizes new protein molecules?
Ribosomes
What structure is a network of thin tubes that transports newly synthesized proteins to their location?
Endoplasmic Reticulum (ER)
How are neuron cells different from other cells in the body?
They have a distinctive shape
What type of neuron has it’s soma in the spinal cord?
Motor Neuron
What type of neuron recives excitation from other neurons?
Motor Neuron
What type of neuron conducts impulses along its axon to a muscle or gland?
Motor Neuron
What type of neuron is specialized at one end to be highly sensitive to a particular type of stimulation?
Sensory Neuron
What are the components of all neurons?
Dendrites
Soma/Cell body
Axon
Presynaptic Terminals
What are branching fibers that have a surface that is lined with synaptic receptors responsible for bringing information into the neuron?
Dendrites
What is the function of dedritic spines?
Increase surface area of dendrite
The greater the surface area of the dendrite, the more what it receives?
Information
Where is the nucleus, mitochondria and ribosomes contained?
Cell Body/Soma
What is the responsibility of the cell body/soma?
Metabolic work in the neuron
The cell body/soma is covered with what?
Synapses on it’s surface
What is an axon?
Thin fiber of a neuron
What does an axon do?
Transmits nerve impulses toward other neurons, organs or muscle.
Axons may have what?
Myelin Sheath
What is a myelin sheath?
Insulating material around axons
What is the nodes of ranvier?
Interruptions in the myelin sheaths
What are presynaptic terminals?
End points of an axon that release chemicals to communicate with other neurons
What axon brings information INTO structure?
Affferent Axon
What axon carries information AWAY from a structure?
Efferent Axon
What are the types of neuorns whose dendrites and axons are completely contained within a single structure?
Interneurons or Intrinsic Neurons
Neurons vary in what?
Size
Shape
Function
The shape of a neuron determines what?
Connection with other neurons and it contribution to the nervous system.
The function of a neurons is related to what?
Shape of the neuron
What type of cell helps synchronize the activity of the axon by wrapping around the presynaptic terminal and taking up chemicals that are released by the axon?
Astrocytes
Astrocytes are responsible for what?
Dilating blood vessels to bring more nutrients into brain areas with heightened activity
What type of cell removes waste material, viruses, and fungi from the brain?
Microglia
What else do microglia do?
Removes dead, dying or damaged neurons
Where are oligodendrocytes found?
Brain
Spinal Cord
Where are schwann cells found?
Peripheral nervous system
What is the function of oligodendrocytes and schwann cells?
Build myelin sheath that surrounds and insulates certain vertebrae axons
What guides the migration of neurons and the growth of their axons and dendrites during embryonic development
Radial Glia
When embryonic development finishes, what do radial glia differentiate into?
Neurons and a smaller number differentiate into astrocytes and oligodendrocytes.
What is a mechanism that surrounds the brain and blocks most chemicals from entering?
Blood brain barrier
What destroys damaged or infected cells throughout the body?
Immune System
Because neurons in the brain generally don’t regenerate, it’s vitally important for the BBB to block what?
Incoming viruses, bacteria, or harmful material from entering the brain.
What is the protein mediated process that expends energt to pump chemicals from the blood into the brain?
Active transport
What are brought into the brain via active transport?
Glucose
Certain Hormones
Amino Acids
Few Vitamins
The BBB is essential to health but can pose difficulty in allowing what to pass the barrier?
Chemicals like chemotherapy for brain cancer
What type of neurons depends almost entirely on glucose?
Vertebrate Neurons
What is one of the few nutrients that can pass through the BBB?
Sugar
Neurons needs a steady supply of what?
Oxygen
20% of all oxygen consumed by the body is used by what?
Brain
What vitamin does the body need to use glucose?
Thiamine
Prolong thiamine deficiency leads to what?
Death of neuron-Korsakoff’s Syndrome
Korsakoff’s syndrome is a result of what?
Alcoholism
Korsakoff’s syndrome is marked by what?
Severe memory impairment
What is the electrical message that is transmitted down the axon of a neuron?
Nerve Impulse
The nerve impulse doesn’t travel directly down the axon but does what?
It’s regenerated at points along the axon so it’s not weakened.
What is the speed of a nerve impulse?
Less than 1 meter/second to 100 meters/second
A touch on the should reaches the brain more quickly that what?
Touch on foot
Messages in a neuron develp from disturbances of what?
Resting Potential
At rest, the membrane maintains an electrical gradient known as what?
Polarization
What is polarization?
Difference in electrical charge inside and outside of the cell
The inside of the membrane is what?
Slightly negative compared to the outside (-70mV)
The resting potential of a neuron refers to what?
State of neuron prior to sending nerve impulse.
The membrane is what, allowing some chemicals to pass more freely than others?
Selectively permeable
What passes through channels in the membrane?
Sodium (Na+)
Potassium (K+)
Chloride (Cl-)
When the membrane is resting what do the channels do?
Sodium channels closed (Na+ can’t pass)
Potassium channels partially closed (K+ passes)
What is a protein complex that continually pumps 3 sodium ions out of the cells while drawing 2 potassium ions into the cell?
Sodium-Potassium Pump
The sodium potassium pump helps to do what?
Maintain electrical gradient
Sodium potassium pump uses what?
Active transport (requiring ATP)
The electrical gradient and concentration gradient do what?
Work to pull sodium ions into the cell
The electrical gradient tends to pull what into cells
Potassium Ions
Potassium ions leak out of the electrical gradient carrying what?
Positive charge (K+)
The resting potential remains stable until what?
Neuron is stimulated
What increases the polarization or the difference between the electrical charge of two places
Hyperpolarization
What decreases the polarization toward zero?
Depolarization
What is a level above which any stimulation produces a massive depolarization?
Threshold of excitation
What is a rapid depolarization of the neuron?
Action Potential
The action potential threshold varies from what
One neuron to another but is consistent for each neuron.
Stimulation of the neuron past the threshold of excitation triggers what?
Nerve impulse or action potential
Action potentials back propagate into what?
Cell body and dendrites
Dendrites become more susceptible to structural changes that’s responsible for what?
Learning
What is the law that states that the amplitude and velocity of an action potential are independent of the intensity of the stimulus that initiated it?
All or None Law
Action potentials are equal in what?
Intensity and speed within a given neuron
At the start of action potential, what are mostly outside the neuron?
Sodium Ions
At the start of an action potential what are mostly inside?
Potassium ions
When the membrane depolarizes, what open?
Sodium and potassium channels in the membrane
At the peak of the action potential what happens?
Sodium channels close
Membrane channels permeability depend upon what?
Voltage difference across membrane
When sodium channels are opened, what comes in?
Positively charged sodium ions and nerve impulse occurs.
After an action potential occurs, what happens?
Sodium channels are closed
The neuron is returned to it’s resting state how?
Opening potassium channels
Potassium ions flow out due to what?
Concentration gradient and they take their positive charge with them.
The sodium potassium pump later restores what?
Original distribution of ions.
The process of restoring the sodium-potassium pump to its original distribution takes what?
Time
An unusally rapid series of action potentials can lead to what?
Buildup of sodium within the axon
The buildup of sodium in the axon can be what?
Toxic to a cell , but only in rare instances such as stroke and after use of certain drugs.
Local anestheic drigs block what?
Sodium channel and prevent action potentials from occuring (I.e. novacaine)
After an action potential, a neuron has what?
Refractory period
A refractory period occurs when?
When the neuron resists the production of another action potential.
What is the first part of the period in which the membrane cannot produce an action potential?
Absolute refratory period
What is the second part in which it takes a stronger than usual stimulus to trigger an action potential?
Relative refractory period
In a neuron, the action potenatial begins where?
Action Hilock (Swelling where axon exits soma)
What is the transmission of the action potential down the axon?
Propagation of the action potential
What is interrupted by short unmyelinated sections of nodes of Ranvier?
Myelin Sheath
What is an insulating material composed of fats and proteins?
Myelin
At each node of Ranvier, the action potential is regenerated by what?
Chain of positively charged ions pushed along by the previous segment.
The jumping of the action potential from node to node does what?
Provides rapid conduction of impulses
Conserves energy for the cell
What is the disease in which myelin sheath is destroyed and is associated with poor muscle coordination and visual impairments
Multiple Sclerosis
What has short axons that exchange information with only close neighbors and don’t produce action potentials?
Local Neurons
When local neurons are stimulated, they produce graded potentials that vary in what?
Magnitude and don’t follow the all or none law.
Local neurons do what in proportion to the stimulation?
Depolarize or hyperpolarize
Why are local neurons difficult to study?
They are really small.
