Chapter 2: The nervous system Flashcards
central nervous system
a major division of the nervous system comprising the brain and spinal cord, which receives neural messages from and transmits neural messages to the peripheral nervous system
brain
brain is a complex organ contained within the skull that coordinates mental processes and behaviour and regulates bodily activity.
spinal cord
cable of nerve tissue that extends from the brain, connecting it to the peripheral nervous system.
peripheral nervous system
major division of the nervous system comprising every neuron in the body outside the central nervous system.
autonomic nervous system
is a division of the peripheral nervous system that regulates visceral muscles, organs, and glands, and transmits neural messages to the central nervous system about their activity.
visceral muscles, organs, and glands, which are muscles, organs, and glands not connected to the skeleton that are predominantly self-regulating and do not require conscious control.
somatic nervous system
is a division of the peripheral nervous system that transmits neural messages related to voluntary motor movement.
how does somatic nervous system coordinate movement
Sensory neural messages travel from sensory receptors, to the brain via afferent neural pathways in the somatic nervous system and the spinal cord.
The brain processes this sensory information, coordinating and initiating a conscious motor response.
Motor neural messages travel from the central nervous system to skeletal muscles, via efferent neural pathways in the somatic nervous system.
The skeletal muscles carry out the conscious motor response.
sympathetic nervous system
division of the autonomic nervous system that activates visceral muscles, organs, and glands, preparing the body to respond to a threat or stressor.
parasympathetic nervous system
is a division of the autonomic nervous system that maintains the optimal and balanced functioning
of visceral muscles, organs, and glands. This involves returning them to optimal and balanced functioning after experiencing heightened bodily arousal, as well as maintaining homeostasis.
neuron
a nerve cell that receives and transmits neural information
motor neuron
(also known as efferent neurons), which transmit neural messages about motor movement from the central nervous system to the peripheral nervous system.
sensory neuron
(also known as afferent neurons), which transmit neural messages about bodily sensations from the peripheral nervous system to the central nervous system.
interneurons
which transfer neural messages between sensory neurons and motor neurons. The central nervous system, including the brain and spinal cord, is made up of interneurons.
Conscious responses
deliberate and voluntary actions that are intentionally initiated by the brain and performed by the body.
How do conscious responses work?
1) The sensory stimulus comes into contact with sensory receptors.
2) sensory neural message is transmitted via afferent pathways in the somatic nervous system, and then the spinal cord, to the brain.
3) The brain processes this sensory information, coordinating and initiating a conscious motor response.
4) This motor neural message is transmitted via efferent pathways in the spinal cord, and then the somatic nervous system, to skeletal muscles.
5) The skeletal muscles carry out the conscious motor response to the sensory stimulus.
Unconscious respones
are automatic and involuntary actions that are performed by the body independently of the brain.
physiological responses of the autonomic system
sympathetic responses:
*Heart rate increases to increase blood flow
* Breathing rate increases and lung airways expand enabling high levels of physical activity.
* Pupils dilate to allow more light to enter the eyes, improving vision.
* The body releases more glucose to energise the body.
parasympathetic responses:
* Lung airways constrict, enabling a steady and regular breathing rate.
* Pupils constrict according to external light levels, allowing an appropriate amount of light to enter the eyes for adequate vision.
* The body releases less glucose to allow the body to rest and prevent the depletion of energy stores.
spinal reflex
which is an unconscious response to sensory stimuli that is initiated by interneurons in the spinal cord independently of the brain.
Path along which the neural signal is transmitted as part of the spinal reflex is called the reflex arc.
how does the spinal reflex happen
1) A harmful sensory stimulus is detected by sensory receptors, which transmit this sensory message via sensory neurons in the somatic nervous system to the spinal cord.
2) An interneuron in the spinal cord immediately relays this sensory neural signal to a motor neuron as, initiating an automatic and unconscious motor response.
3) The motor message is transmitted via motor neurons in the somatic nervous system to skeletal muscles, which carry out this unconscious motor response.
4) The sensory message continues to travel via afferent tracts in the spinal cord to the brain. Then, the brain independently registers the sensation that triggered the spinal reflex.
Neural Synapse
region that includes the axon terminals of the presynaptic neuron, the synaptic gap, and the dendrites of the postsynaptic neuron
presynaptic neuron
is the neuron that releases neurochemicals into the neural synapse.
postsynaptic neuron
is the neuron that receives neurochemicals from the neural synapse.
synaptic gap
is the space between the presynaptic neuron and the postsynaptic neuron.
synaptic transmission
is the chemical conveyance of neural information between two neurons across a neural synapse.
process of synaptic transmission
- Neurochemicals are produced in the axon terminals of the presynaptic neuron.
- Neurochemicals are released from the axon terminals of the presynaptic neuron into the
synaptic gap. - Neurochemicals bind to receptor sites on the dendrites of the postsynaptic neuron.
- Neurochemicals affect the postsynaptic neuron, either triggering or inhibiting a response.
lock and key
Each neurochemical has a distinct molecular structure that corresponds to a specific receptor site that matches its specific molecular structure.
‘key’ represents a neurochemical and the ‘lock’ represents the receptor site. A specific neurochemical can only bind to its corresponding receptor site to affect the postsynaptic neuron and ‘unlock’ a response.
Neurotransmitters
are chemical molecules that have an effect on one or two postsynaptic neurons, quick but short lasting effect
Glutamate + excitatory effects
is the main excitatory neurotransmitter in the nervous system. Increases the likelihood of the postsynaptic neuron firing an action potential.
Glutamate has an important role in learning and memory. Specifically, the excitatory effects of glutamate form and strengthen synaptic connections between neurons that are repeatedly activated during learning and represent memories of what has been learnt.
GABA + inhibitory effects
is the main inhibitory neurotransmitter in the nervous system. Decreases the likelihood of the postsynaptic neuron firing an action potential.
GABA has an important role in regulating postsynaptic activation in neural pathways, preventing the overexcitation of neurons. In this way, GABA reduces anxiety and prevents seizures, by inhibiting the uncontrolled firing of action potentials that contribute to anxiety.
neuromodulators
are chemical molecules that have an effect on multiple postsynaptic neurons.
released into multiple neural synapses and has a slow but long lasting effect
Dopamine
is a neuromodulator primarily responsible for voluntary motor movement, the experience of pleasure, and reward-based learning.
can have excitatory and inhibitory effects on the postsynaptic neuron.
Role in functioning dopamine
Dopamine has an important role in coordinating voluntary motor movement by transmitting neural information that enables smooth, coordinated muscle movement.
* Dopamine has an important role in reward-based learning and motivation.
Rewarding behaviours trigger the release of dopamine have a pleasurable consequence for the person and are therefore more likely to be repeated. In this way, dopamine can motivate the person to engage in rewarding behaviours to experience pleasure once again. Release of dopamine is associated with addiction.
Serotonin
neuromodulator primarily responsible for the regulation of mood and sleep.
inhibitory effects on the postsynaptic neuron.
role in functioning
Serotonin has an important role in mood regulation and stabilisation. Appropriate levels of serotonin in the brain enable a person to experience positive and stable moods, promoting wellbeing.
Low levels of serotonin in the brain are associated with mental disorders, including depression.
- Serotonin has an important role in regulating the sleep-wake cycle, influencing quality and quantity of sleep as well as feelings of wakefulness and alertness.
Synaptic Plasticity
is the ability of synaptic connections to change over time in response to activity or experience.
Sprouting
is the ability of dendrites or axons to develop new extensions or branches. This increases the reach of the neuron and enables the formation of new synaptic connections.
Pruning
elimination of synaptic connections that
are not adequately activated. When neural synapses are not used, they are removed or ‘pruned’. This is necessary to accommodate stronger and more essential synaptic connections, consequently enhancing the efficiency of brain functioning.
rerouting
ability of a neuron that is connected to a damaged neuron to create an alternative synaptic connection with an undamaged neuron.
The synaptic connection is reestablished via an alternative route, restoring brain functioning.
long term potentiation
long-lasting and experience-dependent strengthening of synaptic connections that are regularly coactivated.
LTP process
During learning and memory, the repeated coactivation of the presynaptic neuron and postsynaptic neuron, strengthens the synaptic connection between these neurons.
Structural changes include:
* increased number of receptor sites on the dendrites of the postsynaptic neuron.
* bushier dendrites on the postsynaptic neuron due to sprouting.
* increased number of synaptic connections between neurons due to sprouting.
LTP results in
increased strength of synaptic connections in a neural pathway increases the efficiency of synaptic transmission. In this way, when this specific neural pathway is activated once again, neural signals are transmitted more rapidly and efficiently.
long term depression
long-lasting and experience-dependent weakening of synaptic connections between neurons that are not regularly coactivated.
LTD process
neural pathway that has been previously established is no longer regularly activated, long-term depression weakens the synaptic connections in this neural pathway that is no longer necessary.
The weakening of a neural synapse involves the infrequent release of neurotransmitters into the synaptic gap and the low-intensity stimulation.
structural changes of LTD
- decreased number of receptor sites on the dendrites of the postsynaptic neuron.
- decreased number of dendrites on the postsynaptic neuron due to pruning.
- decreased number of synaptic connections between neurons due to pruning.
effect of LTD
less receptive to neural signals from presynaptic neurons and consequently less readily activated. This decreases the efficiency of synaptic transmission along the neural pathway.
enables the brain to accommodate more necessary memory traces regulating the number of synaptic connections in the brain.
