1/26: Nervous System Overview & Action Potentials Flashcards
What is one of the two major control systems of the body mediating systemic homeostatic processes?
Nervous system
What does the nervous system do?
- Muscle contraction
- Integration of blood oxygen, carbon dioxide, and pH levels via respiratory activity
- Regulation of volumes and pressures in the circulation via cardiovascular and urinary function
- Digestive system motility and secretion
What does the NS work along with to maintain systemic homeostasis?
Endocrine system
What system is a quick fix to homeostatic disturbances?
NS
What system is a slower long-term maintenance?
ES
What is the functional unit in the NS?
Neurons
What are neuroglia?
Support cells for neurons
The NS uses a combination of ______ and ________ signals to communicate information around the body
Chemical; electrical
What are receptors in the NS?
- Special sensory receptors (sensations of smell, taste, vision, balance, and hearing)
- Visceral sensory receptors (monitor internal organs, including those of cardiovascular, respiratory, digestive, urinary, and reproductive systems)
- Somatic sensory receptors (monitor skeletal muscles, joints, skin surface; provide position sense and touch, pressure, pain, and temperature sensations)
What makes up the afferent division of the NS?
Central nervous system (brain and spinal cord)
What makes up the efferent division of the NS?
Peripheral nervous system
What can the peripheral NS be further divided into?
Somatic and autonomic nervous system
What can autonomic be further divided into?
Parasympathetic and sympathetic divisions
What does the somatic nervous system control?
Skeletal muscle
What does the parasympathetic and sympethetic division control?
- smooth muscle
- cardiac muscle
- glands
What are the two types of effector responses in the NS?
- Local
- Systemic
What are the three main parts of a neuron?
- Dendrites (info enters)
- Cell body
- Axon (info exits)
What is the function of the axon hillock?
First portion of the axon
What are Nissl bodies?
In the cell body (clusters of ribosomes) produce protein and causes cell body to appear gray
Many neurons have axons that are ________
Myelinated
________ are formed by neuroglia cells
Internodes
What are oligodendrocytes?
Form myelin for axons in CNS
What are schwann cells?
Form myelin for axons in PNS
Inernodes are separated by small segments of axon not covered in myelin which is known as ________
Nodes of ranvier
What is the function of the myelin covering?
Speed up the rate of nerve impulse conduction (saltatory conduction)
What are bipolar neurons?
Central cell body with dendrites on one side and axon on the other
What is a pseudounipolar neuron?
Dendrites are continuous with axon
Cell body is pushed to one side
What is a multipolar neuron?
Multiple dendrites attached to the cell body
What are the three types of neurons?
- Sensory neurons
- Motor nuerons
- Interneurons
What are the structure of sensory neurons?
Pseudounipolar neurons, bipolar
What is the relation of sensory neurons with the PNS?
Afferent division of PNS
Dendrites/cell body in PNS
What is the relation of sensory neurons to the CNS?
Carry sensory information from reflex receptor to CNS
Axons typically myelinated and extend into CNS
What is the structure of motor neurons?
Multipolar neurons
What is the relation of motor neurons with the PNS?
Efferent PNS
Axons typically myelinated, extend into PNS and synapse with effectors
What is the relation of motor neurons with the CNS?
Carry moto commands from CNS to EFFECTORS
Dendrites/cell body in CNS
What is the structure of interneurons?
Multipolar, anaxonic
Where are interneurons found?
Only in the CNS
What is the function of interneurons?
Carry information from one neuron to another
Integration
Are interneurons myelinated?
May or may not be
What are the two types of electrical signals in neurons?
- Action potentials
- Graded potentials
What is the strength and size of an action potential?
Always the same (depolarization followed by repolarization) with no change in strength or size as they travel along the membane
Is an action potential all or none?
Yes
What are action potentials triggerd by?
At axon hillock when threshold potential is reached (Vm at which AP triggered; typically around -50mV)
Where does an action potential propogate?
Along cell membrane of axon from axon hillock toward axon terminal
What is the speed of an action potential?
Relatively fast changes in membrane potential
What is a graded potential?
Small changes in membrane potential of variable strength/amplitude
Where do graded potential travel?
A short distance along membrane and lose strength as they travel
What is the duration of graded potentials compared to action potentials?
Longer than APs
What are examples of graded potentials?
EPSPs and IPSPs
Receptor potentials, end plate potentials
What are EPSPs?
Excitatory postsynaptic potentials (depolarizations); moves Vm towards threshold potential; increases likelihood of AP
What are IPSPs?
Inhibitory postsynaptic potentials (hyperpolarizations); moves Vm away from threshold; decreases likelihood of AP
What are receptor potentials?
Reflex receptors; excitatory
What are end plate potentials?
Skeletal muscles; excitatory
What is depolarization?
Vm becomes more positive (less negative) (EPSPs)
*1 on the chart
What is repolarization?
Vm returns to resting value
*2 on the chart
What is hyperpolarization?
Vm becomes more negative than resting (IPSPs)
Which ion channels if opened, cause an EPSP?
Increase Na+ in, increase Ca+ in
Which ion channels if opened cause an IPSP?
Increase K+ out, increase Cl- in
What is happening at A, B, and C?
A. Resting membrane potential
B. EPSP depolarizes membrane
C. EPSP reaches threshold and causes voltage-gated Na+ channel to open - transition from graded potential to action potential (axon hillock)
What is happening at D and E?
D. Depolarization; Na+ moves into the cell through open voltage gated Na+ channe;s
(activated via positive feedback)
E. VG Na+ channels close and slow voltage-gated K+ channels open
What is happening at F, G, H, and A?
F. repolarization; K+ moves outside of the cell through open VG K+ channels
G. Hyperpolarization; VG K+ channels still open
H. Voltage gated K+ channels close
A. Resting membrane potential
What are the two gates that facilitate the Na+ channel?
- Activation gate
- Inactivation gate
What is the activation gate?
Closed at resting Vm, quickly opens at threshold depolarization
What is the inactivation gate?
Open at resting Vm, slowly closes at threshold depolarization
What is resting mV for the voltage-gated Na+ channel?
-70mV
What is mV for the voltage-gated Na+ channel when activated?
-55mV to 35mV
What is mV for the voltage-gated Na+ channel when inactivated?
+35mV to -70mV
What is the voltage gated K+ channel?
Single voltage gate begins to open at threshold, but is slow– delayed by the same time as the VG Na+ channel’s inactivation gate
What is resting mV for the voltage gated K+ channel?
-70mV
What is slow activation mV for the voltage gated K+ channel?
+35mV to -70mV
Activation of Na+ channels occurs via a ________ feedback loop
Positive
*once the inactivation gate is closed the positive feedback loop stops
