[Biology] Ch.4: The Nervous System Flashcards
What are neurons
Specialized cells capable of transmitting electrical impulses and then translating those electrical impulses to chemical signals
What is the difference between the functions of dendrites and the axon hillock
Dendrites receive messages from other cells while the axon hillock integrates incoming messages from other cells
Signals arriving from dendrites can be either [ 1 ] or [ 2 ]; the axon hillock [ 3 ] these signals
1) excitatory 2) inhibitory 3) sums
What determines whether or not the axon hillock will initiate an action potential
If the signals summed from the dendrites are excitatory enough
Why are most mammalian nerve fibers insulated by myelin
To prevent signal loss or crossing of signals
What is the relationship between myelin and the speed of conduction in the axon
It increases the speed of conduction
Compare and contrast oligodendrocytes and Schwann cells
Both are cells that produce myelin but oligodendrocytes in the central nervous system and Schwann cells in the peripheral
What do neurons use neurotransmitters for
To transmit information between neurons
What are the three different kinds of neurons
Sensory, motor, or mixed
The cell bodies of neurons of the same type are clustered together into [ 1 ]
Ganglia
Glial cells play both [ 1 ] and [ 2 ] roles
1) structural 2) supportive
What’s the difference between astrocytes and ependymal cells
Astrocytes nourish neurons and form the blood-brain barrier while ependymal cells line the ventricles of the brain and produce cerebrospinal fluid
What are microglia
Phagocytic cells that ingest and break down pathogens in the central nervous system
True or False: actin potentials are all-or-nothing messages
True
What is membrane potential
An electrical potential difference (voltage) between the inside of the neuron and the extracellular space
Resting potential is about [ 1 ] mV and the inside of the neuron is [ 2 ] relative to the outside
1) -70 2) negative
At rest concentration of [ 1 ] is high and [ 2 ] is low inside the neuron
1) K+ 2) Na+
At rest the concentration [ 1 ] is high and [ 2 ] is low outside the neuron
1) Na+ 2) K+
What does Na+/K+ ATPase important for in the neuron
Restoring the K+ and Na+ gradient after action potentials have been fired
Excitatory input causes [ 1 ] and thus makes the neuron [ 2 ] likely to fire an action potential
1) depolarization (raises the membrane potential from its resting potential) 2) more
Inhibitory input causes [ 1 ] and thus makes the neuron [ 2 ] likely to fire an action potential
1) hyperpolarization (lowering the membrane potential from its resting potential) 2) less
What is the threshold value
The range where an action potential will be triggered (-55 to -40 mV)
What is the difference between temporal and spatial summation
- Temporal = multiple signals are integrated during a relatively short period of time
- Spatial = additive effects based on the number and location of incoming signals
Compare the effect of inhibitory signals firing directly on the soma vs. excitatory signals firing on the dendrites of neurons
Inhibitory signals firing directly on the soma will cause more profound hyperpolarization of the axon hillock than the depolarization caused by a few excitatory signals firing on the dendrites of a neuron
Describe the events on the membrane potential vs. time graph
- Influx of Na+ causing an increase in in membrane potential
- Membrane crosses threshold and action potential is initiated
- Efflux of K+ causing a decrease in membrane potential below threshold
- Hyperpolarization of the membrane
- Na+/K+ pump returns membrane potential to resting
When the cell is brought back to threshold voltage-gated [ 1 ] channels open in response to [ 2 ] and permit the passage of [ 3 ] ions
1) sodium 2) depolarization of the membrane 3) sodium
When and what are the three states of sodium channels
- Closed (before the cell reaches threshold and after inactivation has been reversed)
- Open (from threshold to approximately +35 mV)
- Inactive (from approximately +35mV to the resting potential)
Once [ 1 ] has depolarized the cell there is an electrochemical gradient favoring the efflux of [ 2 ] from the neuron
1) sodium 2) potassium
What is repolarization
When positively charged potassium cations are driven out of the cell and there is a restoration of the negative membrane potential
What is the benefit of hyperpolarization
It makes the neuron refractory to further action potentials
What is the difference between absolute refractory and relative refractory periods
- Absolute = no amount of stimulation can cause another action potential
- Relative = there needs to be greater than normal stimulation to cause an action potential
What is the consequence of a refractory period
Information can only flow in one direction
What affects resistance in an axon potential (describe effect on conduction speed)
- Increased length of the axon = higher resistance and slower conduction
- Greater cross-sectional area = faster propagation and decreased resistance
Does the increased intensity of a stimulus result in an increased potential difference of an action potential
No. It leads to an increased frequency of firing
What is an effector
A neuron that signals to a gland or muscle rather than another neuron
Where are neurotransmitters stored prior to release
In membrane-bound vesicles in the nerve terminal
What happens at the synaptic knob when the action potential reaches the nerve terminal
Voltage gated calcium channels open allowing calcium to flow into the cell (after calcium flows into the cell calcium triggers fusion of membrane-bound vesicles with the cell membrane and causing exocytosis of the neurotransmitter)
What are the three ways neurotransmitters are cleared out of synaptic cleft
- Broken down by enzymatic reactions
- Brought back into the presynaptic neuron
- Diffusion out of the synaptic cleft
What’s the difference between sensory (afferent), motor (efferent), and interneurons
- Sensory = transmit sensory information from receptors to the spinal cord and brain
- Motor = transmit motor information from the brain and spinal cord to the muscles and glands
- Interneurons = found between other neurons; often linked to reflexive behavior
Recite the mnemonic to remember the difference between afferent and efferent neurons
- Afferent neurons ascend in the spinal cord towards the brain/ afferent neurons are affected by the outside world
- Efferent neurons exit the spinal cord on their way to the rest of the body/ efferent neurons have an effect on the environment
What is the difference between white and grey matter in the brain
- White matter = axons encased in myelin sheaths
- Grey matter = unmyelinated cell bodies and dendrites
What are the four divisions of the spinal cord
Cervical, thoracic, lumbar, and sacral
Where are white and grey matter located in the spinal cord
White matter on the outside of the cord and grey matter deep within
The somatic nervous system consists of [ 1 ] and [ 2 ] neurons throughout the skin, joints, and muscles
1) sensory 2) motor
What all does the autonomic nervous system help regulate
Heartbeat, respiration, digestion, and glandular secretions
What is the main role of the parasympathetic nervous system
To conserve energy
Which neurotransmitter is associated with the parasympathetic responses in the body and released by pre and post ganglionic neurons
Acetylcholine
What is the vagus nerve responsible for
Much of the parasympathetic inner action of the thoracic and abdominal cavity
The sympathetic nervous system is activated by [ 1 ] and is closely associated with [ 2 ] and [ 3 ] reactions
1) stress 2) rage 3) fear
What is the mnemonic for for the sympathetic and parasympathetic nervous system
- Sympathetic = fight or flight
- Parasympathetic = rest and digest
What is the difference between a mono synaptic reflex arc and a poly synaptic reflex arc
- Monosynaptic = there’s a single synapse between sensory neurons that receive the stimulus and the motor neuron that responds to it
- Polysynaptic = there is at least one interneuron between the sensory and motor neurons in a reflex arc
