Nervous Systems Flashcards
central nervous system
brain and spinal cord
Processes info received from our internal and external environment and activates appropriate responses
brain
a complex structure that receives and processes sensory stimuli from the body and coordinates responses, including voluntary movements, emotions and conscious thought.
spinal cord
dense bundle of nerve tissue that runs from the brainstem to the lower middle section of the spine
Two major functions:
- Receive sensory information from the body (via the PNS) and send to the brain for processing
- Receive motor information from the brain and send it to body (via the PNS), to control muscles, glands, organs
damage to the spinal cord
If the spinal cord is severed, the somatic nervous system below the point of severance becomes paralysed because the “bridge” between the CNS and the PNS can not be crossed
- Such damage has permanent consequences because the nerves in the spinal cord can not regenerate (grow back)
Peripheral Nervous System
the entire network of nerves located outside the CNS (autonomic and somatic).
- carries messages between the CNS and the muscles, organs and glands throughout the body.
somatic nervous system (def, sensory function and motor function)
carries sensory (afferent) info to the CNS and motor (efferent) info to the body
autonomic
is a sub-division of the peripheral nervous system that controls the body’s internal environment in an autonomous or self-regulated manner.
occurs without conscious/voluntary effort
E.g digestion, heart rate, respiration
sympathetic
Activates internal muscles, glands and organs to prepare the body to deal with vigorous activity or a stressful/threatening situation
Activated by a stressor or fear stimulus
- Enhances survival by producing an immediate response –“fight or flight”
parasympathetic nervous system
In times of minimal stress and in the absence of threat, helps to maintain the internal body environment in a steady, balanced state
Counterbalances the activities of the sympathetic system.
Restores the body to a state of calm (homeostasis)
enteric
A subdivision of the autonomic nervous system; it consists of nerve cells lining the gastrointestinal tract and controls the digestive system
conscious response
any response that requires awareness
The response will usually be a voluntary, ‘intentional’ reaction
E.g scratching an itch, throwing a ball etc
unconscious response
any response that does not require awareness
It is involuntary, unintentional, and automatic and we cannot ordinarily control its occurrence
E.g shivering, sneezing, spinal reflex
spinal reflex
An unconscious, involuntary and automatically occurring response to certain stimuli without any involvement of the brain
steps of spinal reflex
Eg: touching a sharp object
- sensory receptors respond to the stimulation
- send message that is carried by the sensory neurons to interneurons in the spinal cord
- interneurons in the spinal cord relay the message to motor neurons
- motor neurons carry the message along a motor pathway to the muscles causing a withdrawal reflex. The hand is moved away before pain is perceived
- While the spinal reflex occurs, sensory neurons are also carrying the message further up the spinal cord to the brain
- The message is received in the brain (the area that processes this type of sensory info) and pain is perceived
neurotransmitters
A chemical substance produced by neurons that carries messages to other neurons or cells within the nervous system, including; muscles, organs and glands. (Excitatory and Inhibitory)
excitatory neurotransmitter
increase the likelihood that the post-synaptic neuron will fire an action potential or neural impulse
E.g Glutamate
Inhibitory neurotransmitter
decrease the likelihood that the post-synaptic neuron will fire an action potential or neural impulse
E.g GABA
glutamate
the primary excitatory neurotransmitter in the nervous system and is associated with enhanced learning and memory
GABA
the primary inhibitory neurotransmitter
fine-tunes neurotransmission in the brain and maintains neurotransmission at an optimal, or ‘best possible’, level.
Associated with anxiety, specific phobias and Parkinson’s disease
Glutamate and learning
stimulates connections between neurons.
Glutamate is released when a neural pathway associated with an experience is activated or stimulated.
E.g: as you read and form a memory, glutamate will be released in the neural pathway associated with this concept in your brain.
Each time you retrieve this memory, this pathway will probably be strengthened and if you don’t this neural pathway will probably become weaker over time
agonist
mimic the effect of a neurotransmitter. E.g. a GABA agonist may make it MORE likely that GABA inhibits neurotransmission
antagonist
slow down the effects of a neurotransmitter. E.g.
a GABA antagonist will reduce its inhibitory effect
neuromodulator
a subclass of neurotransmitters that alter the strength of neural transmission, by increasing or decreasing the responsiveness of neurons to neurotransmitter signals.
E.g Dopamine and serotonin (can work together)
dopamine
a multifunctional neurotransmitter with both excitatory and inhibitory effects that is involved in many CNS functions such as pleasure, movement, attention, mood, cognition and motivation.
Dopamine is a neuromodulator because it reinforces the neural activity in regions of the brain associated with these functions
Dopamine and the reward pathway
The reward pathway refers to a group of structures in the brain that are activated by rewarding or reinforcing stimuli
Controls our responses to natural rewards e.g food, sex, social interactions, and an important determinant of motivation.
When we are exposed to these rewarding stimuli, the brain increases the release of dopamine along this reward pathway in the brain, which modulates the brain activity of the structures along it.
The more dopamine released within the reward centre, the more a stimulus is sensed as a reward
influence of dopamine - thirst
Dopamine release is coupled with the gulping motion and drinking behaviour (drinking is a learned behaviour)
influence of dopamine - hunger and eating
The consumption of food releases dopamine and gives us feelings of pleasure, therefore increasing our chances of eating food the next time we experience hunger
The brain receives signals from several hormones that indicate when food is needed or not. These signals modify dopamine output from the brain’s reward pathway, controlling our motivation for food
influence of dopamine - addiction
Whenever we see a reward worth chasing, our brain produces higher levels of dopamine, motivating us to complete the task, no matter how unhealthy or difficult the task might be.
Theory suggests that most addictions are caused by the brain’s inability to produce dopamine naturally without the behaviour or the substance that someone is addicted to
seratonin
an inhibitory neurotransmitter that also acts as a neuromodulator.
In the brain, it modulates virtually all human behavioural processes, (e.g. mood, perception, reward)
The serotonin pathway originates in the brainstem and extends to almost all areas of the cerebrum including the cerebral cortex
influence of serotonin - mood
- serotonin levels are high = mood improves
- However, there are a lot of other chemical processes happening in the body, so it is difficult to establish a cause-and-effect relationship.
balanced serotonin levels = calm, focused, happy and stable moods
influence of serotonin - sleep
- lower levels of serotonin = disruptive rhythm of being awake and asleep
- Research generally shows that if the brain lacks serotonin, a person will have a reduced pressure to sleep when required, thus increasing restlessness and wakefulness when they should be sleeping
influence of serotonin - aggression and impulsivity
- higher serotonin level = people waiting longer for rewards, thus reducing impulsivity.
- Research indicates that low levels of serotonin in the brain can affect communication between specific structures within the limbic system responsible for regulating emotions, increasing aggressive and violent behaviours
learning
involves the acquisition of new information, behaviour or abilities through experience.
For learning to have occurred, the new knowledge or skill must be retained in memory
Herbs rule
HERBS RULE = NEURONS THAT FIRE TOGETHER, WIRE TOGETHER
- When a neurotransmitter is repeatedly sent across the synaptic gap, pre and postsynaptic neurons are repeatedly activated at the same time
- This changes the structure of the synapse, strengthening the connection between these two neurons at the synapse
- When this connection is strengthened, they are more likely to fire together again, and their signals are more efficient in the future
long term potentiation
the long-lasting strengthening of synaptic connections, resulting in enhanced or more effective synaptic transmission
The effect of LTP is to improve the ability of two neurons to communicate with each other
long term depression
the opposite of LTP.
LTD is a long-lasting decrease in the strength of synaptic transmission
This results from lack of stimulation of pre and postsynaptic neurons, or prolonged low-level stimulation