Chapter 5 Flashcards
What is a Ionotropic receptor
- Embedded membrane protein with two parts:
- A binding site for a neurotransmitter + A pore that regulates ion flow to directly and rapidly change membrane voltage
- Allows the movement of ions such as Na+
,K+, and Ca2+ across a membrane
What occurs when the Ionotropic receptor binds to the binding site?
When neurotransmitter attaches to binding site, the pore opens or closes, changing the flow of ions.
What is a Metabotropic receptor and what is its function?
- Embedded membrane protein with a binding site for a neurotransmitter but no pore
- Indirectly produces changes in nearby ion channels or in the cell’s metabolic activity
- Linked to a G protein that can affect other receptors or act with second messengers to affect other cellular processes
What is an Amplification Cascade?
- A single neurotransmitter binding to a metabotropic receptor can activate an escalating sequence of events. Proteins can
be activated or deactivated
Explain the role of receptor subtypes:
Each neurotransmitter may interact with a number of receptor subtypes specific to that neurotransmitter.
* Each subtype has slightly different properties, which
confer different activities.
Explain how the relationship between a neurotransmitter and a behaviour is not simply a cause and effect
A single neuron may use one transmitter at one synapse and a different transmitter at another synapse.
* Different transmitters may coexist in the same terminal or synapse (even in a single vesicle!!)
What is a cholinergic receptor? (motor neuron)
Neuron that uses acetylcholine (ACh) as its main neurotransmitter
* Excites skeletal muscles to cause contractions
What is a Nicotinic ACh receptor (nAChr)?
When ACh or nicotine binds to this receptor, its pore opens to permit ion flow, thus depolarizing the muscle fiber
*The nicotinic receptor pore
permits the simultaneous
efflux of K+ and influx of Na
What are the Dual Activating Systems of the Autonomic Nervous System (ANS)?
Parasympathetic and Autonomic Nervous System
Explain the function of the parasympathetic nervous system
calms the body down, producing an essentially opposite rest-and-digest
response.
* Digestive functions ramp up; heart rate ramps down.
Explain the function of the sympathetic nervous system
arouses the body for action,
producing the fight-or-flight response.
* Heart rate ramps up; digestive functions ramp down
Explain which neurotransmitter is responsible for controlling the parasympathetic and sympathetic nervous system and how this process occurs:
CNS neurons synapse with parasympathetic neurons that contain Ach and with sympathetic neurons that contain
norepinephrine.
* Cholinergic neurons in the CNS synapse with sympathetic NE neurons to prepare the body’s organs for fight or flight
* Cholinergic neurons in the CNS synapse with autonomic ACh neurons in the parasympathetic division to prepare the body’s organs to rest and digest
What is the role of norepinephrine in sympathetic arousal?
- During sympathetic arousal, norepinephrine turns up heart rate and turns down digestive functions
- NE receptors on the heart are excitatory, whereas NE receptors on the gut are inhibitory
What is the role of acetylcholine in sympathetic arousal?
- acetylcholine turns down heart rate and turns up digestive functions because its receptors on these organs are reversed
- On the heart, inhibitory
- On the gut, excitatory
Does the enteric nervous system need input from the CNS to function?
- ENS can act without input
from the CNS
Which classes of neurotransmitters are used by the enteric nervous system?
- Uses all four classes of
neurotransmitters—more
than 30 transmitters - Mainly serotonin and
dopamine
What conditions do sensory neurons detect in the gastrointestinal tract?
Detect mechanical and
chemical conditions in the
gastrointestinal system.
What are the four activating systems in the enteric nervous system?
Cholinergic, dopaminergic, noradrenergic, and serotonergic
* (one system for each small-molecule transmitter)
What is an activating system?
Neural pathways that coordinate brain activity through a single neurotransmitter
* Cell bodies lie in a nucleus in the brainstem, and their axons are distributed through a wide region of the brain.
What is the function of the Cholinergic activating system?
Normal waking behavior; is thought to function in attention and memory
What disease is the loss of Cholinergic neurons associated with?
Loss of cholinergic neurons is associated with Alzheimer disease.
What are the two pathways in the Dopaminergic activating system?
-Nigrostriatal pathways
-Mesolimbic pathways
What is the Nigrostriatal pathway responsible for?
Active in maintaining normal motor behavior (coordination)
What disease is the loss of dopamine associated with?
Loss of DA is related to muscle rigidity and dyskinesia in Parkinson disease
What is the function of the Mesolimbic pathways?
Dopamine release causes repetition of behaviors
* Most affected in addiction behaviors (food, drugs, etc.)
* Related to impulse control
What impact does an increase or decrease of dopamine have on our behaviour?
- Increases in DA activity may be related to schizophrenia.
- Decreases in DA activity may be related to deficits of attention.
What is the function of the Noradrenergic system?
Norepinephrine plays a role in learning by stimulating neurons to change structure
* may also facilitate normal development of the brain and organize movement
What effects can imbalances of norepinephrine have?
Imbalances associated with depression, mania
What is a decreased level of norepinephrine associated with?
- Decreased NE activity related to ADHD and hyperactivity
What is the function of the Serotonergic system?
- Plays a role in wakefulness and learning
What is an imbalance of serotonin associated with?
- Imbalances associated with depression,
schizophrenia, obsessive-compulsive disorder, sleep apnea, sudden infant death syndrome (SIDS)
What is learning?
- Relatively permanent change in behaviour that results from experience
What is neuroplasticity?
The nervous system’s potential for change, which enhances its ability to adapt. Required for learning and memory
What is the Hebb Synapse?
Cells that fire together wire together.
Who was Eric Kendal and what was his experiment?
Studied the synaptic basis of learning
using Aplysia. He used enduring changes
in simple defensive behaviours to study
underlying changes in the nervous system.
What is the habitual response?
- Learning behavior in which a response to a stimulus weakens with repeated presentations of the stimulus
eg: Gill withdrawal response in the marine snail Aplysia californica
What occurs at the level of the neurons for habituation to take place? What is the process?
As habituation develops, the excitatory postsynapticpotentials in the motor neuron become smaller.
* Motor neuron is receiving less neurotransmitter from the sensory neuron across the synapse.
* Habituation must take place in the axon terminal of the sensory neuron.
* Less activity from a habituated neuron relative to a nonhabituated one.
* As habituation takes place, Ca2+ influx decreases in response to voltage changes associated with an action potential.
* Reduced sensitivity of Ca2+ channels and
decreased release of neurotransmitter
What is the sensitization response?
- Learning behavior in which the response to a stimulus strengthens with repeated presentations because the stimulus is novel or stronger than normal
What occurs at the level of the neurons for sensitization to take place? What is the process?
- In response to an action potential on an axon of a sensory neuron, K+ channels are slow to open.
- K+ ions cannot repolarize the membrane quickly, so action potential lasts longer than normal.
- Prolongs the inflow of Ca2+, and more transmitter is released.
- Sensitization is the opposite of habituation at the molecular and behavioral levels.
- In sensitization, more Ca2+ influx results in more transmitter being released.
- In habituation, less Ca2+ influx results in less neurotransmitter being released.
What needs to happen for neural changes to result in permanent behavioural changes?
- Neural changes associated with learning must last long enough to account for a relatively permanent change in an organism’s behavior.
- Repeated stimulation produces habituation and sensitization that can persist for months
How does the number and size of sensory synapses change in well-trained, habituated, and sensitized Aplysia?
Habituation-less connections
Sensitization-more connections
