Exam 2: Neuroscience Flashcards
What is the nervous system?
A complex organ with an intricate network of excitable cells
What is are the mechanism of the nervous system?
- CNS (brain and spinal)
- PNS (spinal and cranial nerves)
How many neurons are in the brain?
10^11
What is the difference between the CNS and PNS?
CNS: integration and command center
PNS: carries message to and from spinal and brain
What is the cell body?
Nucleus of a neuron
What are dendrites?
The receptive region of the neuron transmitting pulse to the cell body
What is an axon?
Transmits impulse away from the cell body
Where is action potential first developed?
Axon hilcock
What are presynaptic terminals?
Contains neurotransmitters and releases them down to the synapse and next neuron
What is a bundle of axons called?
Nerves
What are sensory (affernt) neurons?
Brings info to the nervous system using sensory receptors in the periphery
What neurons are associated with afferent neurons?
- Visual
- Olfactory
- Audio
- Tast
- Chemeorecptors
- Touch
- Muscle spindles
Where are sensory signals transmitted to?
Cerebral cortex
What are motor neurons?
Carries info from CNS to periphery
What do motor neurons control?
Skeletal muscles and external sensory organs
What type of neurons have voluntary control?
Motor (efferent)
What is the autonomic nervous system?
Efferent pathways from CNS that innnervate cardiac and smooth muscles and glands
Is the ANS voluntary or involuntary?
Involuntary
What are the divisions of the ANS?
- Sympathetic NS
- Parasympathetic NS
- Enteric NS
What are the neurons associated with the ANS?
- Preganglionic neurans
- Postganglionic neurons
What is difference between pre and post ganglionic neurons?
Pre: Cell bodies that are in the CNS and axons synapse in the autonomic ganglia
Post: Cell bodies in the autonomic ganglia synapse with effector organs
What controls blood vessels?
Sympathetic tone
What are the types of glial cells?
- Astrocytes
- Oligodendrocytes
- Schwann cells
- Microglia
What are astrocytes?
Star-shaped cells that envelop the cappillaries of the BBB supporting the netabolic functions of neurons
What are oligodendrocytes?
Produce myelin in the CNS
What are Schwann cells?
Produce myelin in the PNS
What is microglia?
Undergo phagocytosis to destroy cellular debris, activates from inflammation or injury
How was the blood brain barrier discovered?
Dye was injected in the blood all organs were stained but the brain
What is the blood brain barrier composed of?
Capillary endothelial cells are linked by tight junctions form the BBB
How is the BBB anchors to the brain?
Astrocytes
What is the purpose of the BBB?
- Limits permeability of most molecules
- Membrane transports move glucose to brain
- Protects organ from hormones, chemicals, and harmful substances
What is the unstimulated neuronal resting potential?
-70mV
What is the purpose of an electrical gradient in a neuron membrane?
Develops by one side having a positive or negative charge and the other has the opposing charge
What is the purpose of a chemical gradient in a neuron membrane?
Develops when there are more of 1 ion than the other side
What is an electrochemical gradient?
The sum of electrical and chemical forces across the cell membrane
How is membrane potential generated?
Imbalances of charges across a membrane
How is the resting potential created?
When there is an uneven distribution of K+, Cl-, and Na+
What happens when we generate ionic concentration across the lipid bilayer?
Cell membranes are able to store potential energy in the form of an electrical gradient
Where is Na+ and K+ located in regards to the cell?
Na+ is found on the outside, K+ is on the inside
What is an ionic gradient?
Movement of solutes against their concentration gradient requiring ATP
What is the purpose of active transport within a cell membrane?
Equires ATP to moke ions against their concentration gradient as Na+ leaks in and K+ leaks out
What is the function of Na+/K+ ATPase?
Enzyme that uses energy pump 3 Na+ out and 2 K+ into cell
How much ATP does the sodium-potassium pump use?
30% of the cell’s ATP
What are the electrical components of intercellular fluid?
- Low Na+
What are the electrical components of extracellular fluid?
- Low K+
- High Na+
- High Cl-
What happens if Na+ and Ca++ channels open?
Depolorize the cell
What happens if K+ and Cl- channels open?
Hyperpolarization
What is the function of ion channels?
Allows ions to to flow with their concentration gradient
When would ion channels switch between open and close?
Changes in the membrane potential will stimulate voltage-gated or sensitive channels
What is an excitable membrane?
Membranes containing voltage-sensitive ion channels
What controls a channels?
Size and charges of amino acids lining the channel
What controls a voltage-gated channel?
Controlled by the electrical state of the cell
What controls a chemically-gated channels?
Controlled by messenger molecules or ligands
What are open channel (pores)?
Gates that are open most of the time
What are mechanically-gated channels?
Controlled by physical state of cell (temperature, preasure, stretch) associated with sensory neurons
What creates the post synaptic potential?
Change in the resting potential caused by the activation of a gated channel
What are the types of postsynaptic potential?
- Exicatory
- Inhibitory
What is an excitatory (EPSP)?
When the membrane depolarizes causing an movement of Na and Ca making it easier to fire an action potential
What is an inhibitory (IPSP)?
Membrane hyperpolarizes causing a movement of K and Cl making it harder to fire and action potential
What is the difference between temporal and spatial summation?
T: How often or close a potential is given
S: How many differnt potentials are fired at together
Describe the net summation of EPSPs and IPSPs?
Is reflected in trigger zone of the axon hillock
What is the purpose of hitting a threshold potential?
Producing a significnant changein membrane potential will initiate the neuron
What occurs during additive summation?
- 3 neurons fire but each is bellow the graded potential
- At the trigger zone potentials are added together
- Thereshold is achieved and action potential is generated
What occurs during inhibitory summation?
- Having inhibitory and exicitory neurons fire at the same time
- No action potential is generated because signal at trigger zone is too weak
What occurs during an action potential for either depolarization or repolarization?
Proceeds down the axon the postynaptic terminal
What happens when a presynaptic terminal has been depolarizaed?
Ca++ mediated, synaptic vescicle fuse with membrane releasing neurotransmitters to stimulate or inhibit postsynaptic neurons
Where are signaling molecules after the axon?
Traveling down the synaptic cleft to bind to receptors on the postsynaptic neuron
What is a neuronal action potential?
Transmembrane electrical current governed by ionic fluxes through membrane
What happens to channels at the resting state?
Both Na+ and K+ channels are closed
What are the types of Na+ voltage-gated channels?
- Activation gates
- Inactivation gates
What is the difference between activation and inactivation gates?
A: Closed at resting
I: open at resting
What events occur during the depolarization phase?
- Once neuron threshold potential is achieve, action pontential is fired and Na+ channel activation gates open causing an rapid infflux of Na+ into the cell
- Na+ permeability increases
- K+ channels are still closed
What is threshold potential?
The critical level of depolarization required to fire an action potential
What events occur during the repolarization phase?
- Na+ inactivation channels close
- Voltage sensitive K+ gated channels open
- K+ restores resting potential
What events occur during the hyperpolarization phase
K+ channels close slowly
Why is hyperpolarization important?
- Neuron is insensitive to stimulus slowing down the firing of a neuron (relative refractory period)
- Prevents nerve impulse from going backwards
- Move action potential down the membrane
What is the critical difference between K+ and Na+ channels?
K+ channel close slowly
What is the mechanism of action for phenytoin?
Blocks Na+ channels by closing the inactivation gates
What is the mechanism of action for lidocaine?
Blocks action potential by blocking Na+ channels in sensory axons (no pain)
What occurs during unidirectional propagation?
- Generation of action potential at the axon hillock
- Action poential propagates in one direction because of (relative refactory period), hyperpolariation, and inactivated Na+ channels
- First segment returns to resting state and can fire another action potention
What is the myelin sheath?
Insulates neurons and forms nodes of ranvier made of lipids and protein
What is conduction velocity?
Speed of action potential
What factors affect conduction velocity?
- Diameter of axon
- Presense or absense of myelin
What is saltatory conduction?
Current travels inside the axon so the action potential jumps from node to node inscreading conduction velocity
What is multiple sclerosis?
Autoimmune disease of the CNS demylination in the brain, optic, and spine slowing down nerve conduction
