Lecture 1 Flashcards
What is the general function of our nervous system?
control, regulate, and communicate
What are the separate components of both the Central and Peripheral Nervous Systems?
Central - brain and spinal cord
Peripheral - somatic and autonomic nervous system
What are the main components of the neuron? For each component, what is its role in neuronal activity?
- dendrite - receive info
- soma - integration center
- axon hillock - transmit AP to axon
- axon - carry output signal
- terminal branches - filled with neurotransmitters to transmit signal when stimulated
What are the 3 types of neurons that can be found in the nervous system? In general, where can each be found within our CNS?
- multipolar - soma w/ singular axon, multiple dendrites, multiple terminal branches (CNS)
- bipolar - single dendrite and single axon arising from cell body (special sensory organs like eyes)
- (pseudo) unipolar - axon and dendrite arise from a single process coming out of the soma (PNS)
What is the main role of sensory/afferent neurons, and what types of afferent neurons are found in the nervous system?
- bring single up from PNS to CNS
- special sensory (vision, auditory, equilibrium, gustatory or taste)
- viscerosensory (unconscious transmission from internal organs)
- somatosensory (conscious transmission from skin, muscle, and joints)
What is the main role of motor/efferent neurons, and what types of afferent neurons are found in the nervous system?
- send signal from CNS to PNS
- somatomotor - (voluntary contractions)
- autonomic motor (involuntary contractions)
What is the function of interneurons/associative neurons?
local integration centers that connect sensory and motor neurons
Define a reflex and reflex arc. What types of reflexes can be found in the human body?
- reflex - unidirectional rapid, predictable, and involuntary response to a stimulus
- reflex arc - neural pathway that controls a reflex (sensory receptor - sensory neuron - interneuron - motor neuron - effector)
- types of reflexes - somatic (skeletal muscle) and autonomic (smooth muscle)
Explain the steps of the myotatic reflex, starting from the hit of the hammer to the leg kicking outwards
1) hammer hit which stretches sensory receptors in leg extensor muscle
2A) sensory neuron synapses with and excites motor neuron in spinal cord
2B) sensory neuron excites spinal interneuron
2C) interneuron synapse inhibits motor neuron to flexor muscles
3A) motor neuron conducts AP to synapses on extensor muscle, causing contraction
3B) flexor muscle relaxes b/c activity to motor neuron has been inhibited
4) leg extends
Explain the steps of the Flexor Withdrawal Reflex. When does this reflex come into play in function?
1) painful stimulus
2) sensory neuron activates multiple interneurons
3) Ipsilateral motor neurons to flexor excited
4) Ipsilateral flexor contracts
5) contralateral motor neurons to extensor excited
6) contralateral extensor contracts
Describe the function of astrocytes. What are their PNS equivalent?
- support cells
- repair damage, regulate communication between neurons, provide nutritional support, provide insulation to isolate electrical activity of adjacent neurons, regulate intercellular calcium which affect neurotransmitters
- PNS equivalent are satellite cells
Describe the function of ependymal cells. Where are they specifically found?
- form choroid plexus, facilitate CSF exchange, and produce CSF
- found in ventricle and central canal walls
Describe the function of microglia.
- primary defense system
- remove foreign bodies
- protect against infection
Describe the function of oligodendrocytes and Schwann cells. Where are they each located and what are the major differences between the two?
- create and maintain myelin in CNS (oligodendrocytes) and PNS (Schwann)
- oligodendrocytes can myelinate multiple axons in CNS while multiple Schwann cells are needed to myelinate one axon in PNS
What is the role of myelin? Describe its basic anatomical features.
- gives white matter its white appearance
- insulates axon for quick AP transmission
- mixture of proteins and phospholipids that wrap around axon
Define the Nodes of Ranvier. Where can they be found?
- open areas between myelin sheaths on axon
- enable regeneration of AP
Where can a synapse be found? What are its main components?
- point of contact between neurons and target organ
- main components: presynaptic nerve terminal, postsynaptic element, and synaptic cleft
Describe the differences between the different types of synapses that can be found in the human body. Which is most common?
- Axodendritic (most common) - axon terminal of presynaptic nerve communicating w/ dendrites of a postsynaptic nerve
- Axosomatic - axon terminals of a presynaptic to the cell body or soma of the postsynaptic
- Axoaxonic – axon to axon – act as mediators to other synapses
- Dendrodendritic – dendrite to dendrite (in vision and smell)
Describe the basic setup behind an electrical synapse. What are its main features?
- bi-directional
- tight junctions
- gap junctions (large diameter precisely aligned paired channels, pores, for access)
- fast communication
What are the pros of an electrical synapse? The cons?
pros - fast communication
cons - bi-directional and in the minority of synapsis
Describe the steps that take place during a chemical synapse. (11) How does a chemical synapse differ from electrical synapses?
1) transmitter is synthesized and then stored in vesicles
2) AP invades presynaptic terminal
3) Depolarization of presynaptic terminal causes opening of voltage gated Ca2+ channels
4) Influx of Ca2+ through channels
5) Ca2+ causes vesicles to fuse with presynaptic membrane
6) Transmitter is released into synaptic cleft via excytosis
7) transmitter binds to receptor molecules in postsynaptic membrane
8) opening or closing of postsynaptic channels
9) postsynaptic current causes excitatory or inhibitory potential that changes the excitability of the postsynaptic cell
10) removal of neurotransmitter by glial uptake or enzymatic degradation
11) retrieval of vesicular membrane from plasma membrane
- greater distance between neurons
- slower process
- receptor specific communication
What is the relevance of the resting membrane potential and how is it maintained? Where does it typically lie?
- helps hold neurons to negative charge
- maintained by Na-K pump and ion channels
- typically -70 mV
Describe how ionotropic and metabotropic receptors work. How do they differ?
ionotropic - ligand gated ion channels (neurotransmitter binds to channel and channels open)
metabotropic - g-protein coupled receptors (neurotransmitter binds, g-protein is activated, g-protein subunits or intracellular messengers modulate ion channels, and channel opens)
What are agonists, antagonists, inverse agonists, and neuromodulators?
- agonists - have same effect as neurotransmitter
- antagonists - block effect of neurotransmitter
- inverse agonists - bind to side of neurotransmitter and have exact opposite effect
- neuromodulators - bind to different site than neurotransmitter but affects the likelihood that the neurotransmitter will bind
List the steps involved in the propagation of an action potential, including what structures are involved.
1) resting membrane potential: voltage-gated Na+ channels are in resting state and K+ channels are closed
2) stimulus causes depolarization to threshold (-55 mV)
3) voltage-gated Na+ channel activation gates open
4) voltage-gated K+ channels are open; Na+ channels are inactivating
5) voltage-gated K+ channels are still open; Na+ channels are in the resting state
What membrane potential is required to achieve an action potential?
- 55 mV
Explain the All-or-None principle
AP is only generated once -55 mV threshold is reached, does not matter the strength of a stimulus
Define graded potentials. How do they differ from action potentials?
- smaller, local changes in polarity
- can be excitatory (depolarization) or inhibitory (hyperpolarization)
What is the difference between excitatory post synaptic potentials and inhibitory post synaptic potentials?
- excitatory - depolarization from increased Na+ in cell, increases likelihood of postsynaptic AP
- inhibitory - hyperpolarization from increased Cl- in cell, decreases likelihood of postsynaptic AP
How do the processes of temporal and spatial summation work?
- temporal - quick and rapid potentials that build on each other to reach threshold
- spatial - multiple neurons send their signal at the same time and they all fall on each other to reach threshold
How is an action potential propagated down a neuron’s axon?
1) resting membrane potential
2) axon hillock releases local depolarization from AP
3) AP propagates down axon
4) repolarization
keeps repeating itself down the axon
Explain the difference between continuous conduction and saltatory conduction
- continuous - unmyelinated, moves slower
- saltatory - myelinated, AP jumps from Nodes of Ranvier
