Nervous System Flashcards
Nervous v. Endocrine: Anatomic Arrangement
Nervous: “Wired” system. Specific structural arrangement between neurons and their target cells. Structural continuity.
Endocrine: “Wireless” system. Endocrine cells widely dispersed and not structurally related to one another or their target cells.
________________ respond when body deviates from set-point: (1) and (2)
Homeostatic control systems:
1) Nervous system
2) Endocrine System
Nervous v. Endocrine: Type of Chemical messenger.
Nervous: Neurotransmitters released into synaptic cleft.
Endocrine: Hormoens are released into the blood.
Nervous v. Endocrine: Distance of action of chemical messenger
Nervous: Very short distance – diffuses across synaptic cleft.
Endocrine: Long distance. Carried by blood.
Nervous v. Endocrine: Means of specificity of action on target cell.
Nervous: Dependent upon close anatomic relationship between nerve cells and their target cells.
Endocrine: Dependent upon specificity of target cell binding and responsiveness to a particular hormone.
Nervous v. Endocrine: Speed of response.
Nervous: Rapid. Milliseconds!
Endocrine: Slow. Minutes to days or longer.
Nervous v. Endocrine: Duration of response.
Nervous: Rapid. Milliseconds!
Endocrine: Long - minutes to days or longer.
Nervous v. Endocrine: Major functions
Nervous: Coordinates rapid, precise movements
Endocrine: Controls activities that require long duration, not speed.
What are the two major branches of the nervous system?
1) CNS (brain and spinal cord)
3) Peripheral nervous system
Membrane potential
- Definition
- Important players (4)
Voltage difference across the membrane.
- More Na+ outside, More K+ inside.
- Inside of cell is negative because of lots of Proteins and amino acids (Which are negative) trapped inside.
Potential
- Definition
- Two determining factors
A difference in charge across an area, described in units of voltage (milivolts)
- Basis for membrane potential is determined by the CONCENTRATION GRADIENT and ELECTRICAL GRADIENT.
What is the chemical gradient?
The concentration gradient. High to low.
Equilibrium potential
- Definition
- Depends on two factors
The voltage where an ion’s electrical gradient balances its chemical gradient.
Depends on ion’s VALENCE and CONCENTRATION GRADIENT.
What is VALANCE
An ion’s magnitude of charge
What is CONCENTRATION GRADIENT?
The difference across membrane - difference of what?
What is the valence & equilibrium potential of…
Na+
K+
** What is resting potential?
Na+
- Valence =1
- Equilibrium potential = +60mV
K+
- Valence = 1
- Equilibrium potential = -90mV
Resting potential = 70
Cell is a ________ charged environment because of the ________.
Negatively, amino acids and proteins trapped inside.
Potassium’s (1) gradient is pointing (2).
Potassium’s (3) gradient is pointing (4).
1) Concentration
2) Outside the cell
3) Electrical
4) Inside the cell
Sodium’s (1) gradient is pointing (2).
Sodium’s (3) gradient is pointing (4).
1) Concentration
2) Inside the cell.
3) Electrical
4) Outside the cell.
In theory, if a cell is perfectly permeable to an ion (and there is only one ion), then membrane potential will equal that ion’s equilibrium potential. IN REALITY, there are several ions present in human cells, therefore, a particular cell’s membrane potential will depend on: (1) and (2)
1) The ions present and their individual equilibrium potentials
2) The relative permeability of the membrane to each ion
Excitable cell
- Definition
- Two examples
- A cell that experiences large fluctuations in membrane potential
- Neuronal cells, muscle cells
What are the three main events in an action potential?
1) Depolarization: Cell becomes more positive
2) Repolarization: Cell becomes more negative
3) Hyperpolarizatoin: Cell becomes even more negative than resting potential before returning to its resting potential
What is the average activation voltage of sodium channels?
What is the average activation voltage of potassium channels?
Sodium channels: -50mV
Potassium channels: +30mV
What is the function of hyperpolarization?
- Ensures that all of the N+ gates are capable of resetting.
Seven steps of an action potential
1) Triggering event depolarizes the cell
2) Activation gate opens
3) Depolarization as Na+ enters the cell
4) Inactivation gate swings closed at +30mV
5) Repolarization due to K+ flowing out
6) Hyperpolarization ensures all Na+ gates reset
7) RESTING POTENTIAL RESTORED.
What type of cell activates an action potential?
NEURONAL CELLS
What is a synapse? What are the two types?
- Connection between neuronal cells
- Chemical: Neurotransmitter carries signal from pre-synaptic cell to post-syanptic cell.
- Electrical (gap junctions): Allow for the direct spread of the action potential from pre-synaptic cell to post-synaptic cell.
A (1) neurotransmitter causes (2) of a post-synaptic cell, while
a (3) neurotransmitter causes (4) of a post-synaptic cell.
1) Positive
2) Stimulation
3) Negative
4) Inhibition
Name and define the three categories of neurotransmitters.
- Amino acids: Very efficient system, as amino acids are also used for protein building, etc.
- Monamines: Derived from a single amino acid that’s been modified chemically.
- Catecholamines: Derived from Tyrosine.
Neuroactive peptides
- Modify response of a post-synaptic cell / target’s response
- Not proper neurotransmitters, but instead are peptides that are often co-released with neurotransmitters.
What are electrical synapses?
“Gap junctions.”
Allow for the direct spread of the action potential from pre-synaptic cell to post-synaptic cell.
Name the three most common Amino Acid Neurotransmitters, and what they basically do.
1) Glutamic acid (Glutamate)
- Stimulatory
- Ubiquitous in CNS
2) GABA = Aminobutyric Acid
- Most common Inhibitory
3) Glycine
- Other most common Inhibitory in CNS
Name the three most common Amino Acid Neurotransmitters, and whether they are excitatory or inhibitory.
1) Glutamic acid (Glutamate)
- Stimulatory
- Ubiquitous in CNS
2) GABA = Aminobutyric Acid
- Most common Inhibitory
3) Glycine
- Other most common Inhibitory in CNS
Name three examples of neuroactive peptides.
- Somatastatin
- Oxytocin
- Endorphins
What are four targets of the ANS?
- Smooth muscle
- Cardiac muscle
- Endocrine glands
- Exocrine glands
Two arms of the efferent divison of the PNS (and what they generally do)
1) Parasympathetic Nervous System: “Rest and Digest”
2) Sympathetic Nervous System: “Fight or flight”
What is the ANS?
Portion of the nervous system that controls most visceral function.
Sympathetic v. Parasympathetic NS:
LOCATION OF PREGANGLIONIC CELL BODIES
SNS: Lateral horn of spinal cord (T1-T3)
PNS:
- Midbrain, medulla (CN III, VII, IX, X)
- Lateral horn of spinal cord @T12-L1, exiting at teh vertebral canal at S2-4.
Sympathetic v. Parasympathetic NS:
LOCATION OF POSTGANGLIONIC CELL BODIES
SNS:
- Paravertebral ganglia
= sympathetic chain ganglion
- Prevertebral ganglia
= celiac ganglia
= hypogastric plexus
PNS:
- In scattered plexi close to taret organ
- CN III, VII, IX, X
Sympathetic v. Parasympathetic NS:
Length of preganglionic fibers
SNS: Relatively short
PNS: Relatively long
Sympathetic v. Parasympathetic NS:
Length of postganglionic fibers
SNS: Relatively long
PNS: Relatively short
