Unit 2: Introduction to the Nervous System Flashcards
Nervous System
(controls everything, manages all other systems, every body part has its own nerves)
What is it?
-The network of nerve cells and fibers which transmits nerve pulses (messages) between parts of the body.
Sensory Information
any information about the external environment carried from sensory organs (retina in the eye, cochlea in the ear etc, senses) or the internal (body temp, water levels) to the brain (CNS) by somatic NS=Peripheral NS
Motor Information
Any information about how to respond to (stimuli) external environment carried from brain (CNS) to internal organs (heart or lungs, or muscles for movement)
Central Nervous System (CNS)
-The CNS is composed of the brain and spinal cord.
-It processes sensory information to activate appropriate actions.
-This process occurs extremely rapidly and continuously.
- if question is abt any judgment of sensory info, must be CNS
Brain’s function in CNS
Constantly receives and processes information and co-ordinates a response.
Spinal cord function in CNS
Spinal cord connects the brain to the rest of the body.
functions:
- it sends info. from sensory neurons in various parts of the body to the brain.
- it relays motor commands back to muscles and organs via motor neurons (from brain to PNS)
What could happen if spinal cord is damaged?
- loss of sensation (touch, temp, etc.) because sensory info can’t flow from sensory organs to brain
- loss of motor control (movement)
Peripheral Nervous System (PNS)
The PNS is connected to the spinal cord and consists of all nerves outside the CNS.
-It carries sensory information from the body to the CNS, and motor information from the CNS to the body/ bodily organs
- peripheral means outside - of CNS
Two divisions of PNS:
Somatic nervous system and Autonomic nervous system
Somatic Nervous System
-The Somatic NS transmits sensory information to the CNS from sensory organs and carries out its motor commands.
-Then conveys motor information from CNS to voluntary skeletal muscles for voluntary muscle movements.
Sympathetic Nervous System
- readies the body for the flight or fight response when it exposed to threats, stimulus or stressors (doesn’t necessarily mean stress) e.g a sound or person
-throws off homeostasis
2 divisions of nervous system
- central nervous system
- Peripheral NS
Both work together
Autonomic Nervous System
-is responsible for automatic/ involuntary responses
-carries info between the CNS and internal bodily structures (organs) that carry out basic life processes e.g heart rate and breathing
Divisions of Autonomic Nervous System
- Sympathetic
- Parasympathetic
Parasympathetic nervous system
-supports more mundane, or routine activities, that maintain the body’s store of energy (e.g, regulating blood sugar levels, secreting saliva)
- maintains homeostasis= brings everything back to normal
-when a threat has passed the parasympathetic NS resumes control from the sympathetic NS
Sympathetic responses
- during high levels of threat part 1
-dilates pupils of the eyes allow for more light to enter the eyes and improve sight when needed e.g under threat
-heart rate increases to energise the body for activity by increasing delivery of O2 and glucose to voluntary skeletal muscles
-bladder relaxes=pee your pants to allow for more essential bodily functions during activity
Sympathetic responses
- during high levels of threat part 2
-lung airways relax and expand to allow for increased oxygenation required for more intense activity
-digestion is inhibited to allow for more essential bodily functions needed during activity
-adrenal glands secrete stress hormones to energise the body
Parasympathetic responses
-during rest and inactivity
part 1
-constricts pupils of the eyes according to the light levels required to see optimally
-heart beats at a rate best for optimal functioning during inactivity by directing blood flow evenly around the body as skeletal muscles don’t need increased blood flow at rest.
-lung airways constrict for ideal breathing rate at rest
Parasympathetic responses
-during rest and inactivity
part 2
-digestion operates to allow for regular eating
-bladder constricts and is controlled
-adrenal glands don’t secrete stress hormones to allow the body to rest
-body reduces release of glucose so it doesn’t deplete the body of energy.
sensory/afferent neurons
-transmit info from sensory cells in the body(called receptors), PNS to the brain, CNS (either directly or through the spinal cord), takes the afferent pathway
-in the PNS
interneurons
-function= organises and integrates sensory info in the brain, then initiates and coordinates motor responses. Provide link between sensory and motor neurons
-in the CNS
motor/efferent neurons
-transmits commands from the interneurons to the effector glands, organs and muscles of the body, from CNS to body
-takes efferent pathway
-in the PNS
synaptic knobs or terminal buttons
contain vesicles which hold neurotransmitters involved in moving signals to adjacent cells, transmit chemical info to other neurons
synapse or synaptic gap
-the space between neurons where transmission occurs
-where neurons meet but never physically touch
Electrochemical communication
neurons communicate using electrochemical energy
-electrical=within the neuron-electrical impulse is transmitted along the neuron
-chemical= between neurons- takes place in the synapse when a neurotransmitter are sent from the axon terminals of the presynaptic neuron, to the dendrites of the post synaptic neuron.
-electrical signal stimulates the chemical
Glial cells
main function= provide the structural framework that enable a network of neurons to remain connected
other functions=
-supply nutrients and 02 to neurons so they can function
-destroy and remove dead neurons
-soak up excess neurotransmitters at the synapse that can clog the communication between neurons
-block the entrance of toxic barriers to the brain
Communication between neurons
relies on an action potential
Neurotransmitters- 3 Key steps of chemical communication?
- Synaptic vesicles store neurotransmitters within the nerve cell, inside the axon terminals
- When an action potential reaches the axon terminals of a presynaptic neuron, the synaptic vesicles release neurotransmitters into the synapse.
- These neurotransmitters bind to the receptor sites on the dendrites of the post synaptic neuron and alter its action.
The cerebral cortex, function
-is the largest part of the brain
function= receiving and processing sensory information, initiating motor responses.
- plays a key role in memory, attention, perception, cognition, awareness, thought, language and consciousness
What is meant by “complementary molecular structure”
-This means that the distinct molecular structure of the neurotransmitters being matched by the receptor site means that the receptor site will only respond to specific neurotransmitters and ignore others
- not the same shape but complementary
Detailed flow chart of Neural communication
Dendrites receive neurotransmitters from a previous neuron which stimulates an action potential> the signal pass through the cell body which collects the message> axon generates an action potential> the neural impulse reaches the axon terminals of the presynaptic neuron> then it reaches the terminal buttons which causes the vesicles to release the neurotransmitters into the synaptic gap> the neurotransmitters diffuse across the synapse> the neurotransmitters (key) then bind to receptor sites (lock) on the dendrites of the postsynaptic neuron> the neurotransmitters then make the post synaptic neuron have a excitatory effect= stimulates/activate post synaptic neuron, increasing the likelihood of firing an action potential e.g glutamate OR an inhibitory effect= suppress/slow down post synaptic neuron, decreasing the likelihood of firing an action potential e.g GABA
Contralateral organisation
Right hemisphere receives sensory info from the LHS of the body and controls movements on LHS of the body. The opposite is true of the left hemisphere
Glutamate
-an excitatory neurotransmitter
function and location
-found in the hippocampus and outer layers of the cerebral cortex
-associated with= cognition, learning ( when practicing a new skill Glutamate is release by neurons in brain= reinforces neural pathway and retain what you have learned), memory, behaviour, movement, sensation
-When combined with the receptor site NMDA, it is associated with LTP
What is LTP?
Long term synaptic strength following high frequency stimulation of synapse
Too much Glutamate?
-abnormal neural development (inappropriate neural connections forming e.g additional reflexes, sensation etc)
-neurodegenerative diseases- neuronal damage or death e.g motor neuron disease
GABA (gamma amino butyric acid)
- an inhibitory neurotransmitter
- function and location
-found extensively through the whole nervous system
-reverses the effects of excitatory neurotransmitters e.g reduces stress b/c low levels of GABA are associated with high anxiety levels and GABA is used to treat anxiety
-ends fight or flight response
-alcohol can decrease GABA activity
Neural transmission requires a balance between Glutamate and GABA b/c ?
-overstimulation of neurons can lead to nerve damage
-if there are only excitatory neurotransmitters there would be no flexibility in responses of post synaptic neuron ( they would only be able to fire an action potential in response to inputs
cerebral hemispheres
two divisions of the cerebral cortex
- a longitudinal fissure seperates these two hemispheres
gyri
the elevation points of the brain
sulci
the folds or groove that seperate gyri
Specialized functions of Left Hemisphere
-verbal functions: aspects associated with language, writing, speaking, reading
-analytical functions: logical reasoning, critical evaluation
-non-verbal: sensory and motor functions from the RHS of body ( if damaged= sensation of RHS=lost
-if Left hemisphere=damaged= no communication
Specialised Functions of the Right Hemisphere:
- Non verbal functions:
- Spatial and visual thinking e.g. jigsaws, map reading, recognizing faces, appreciating art and music, creativity and fantasy
- Recognition of emotions relating to facial expressions.
- Sensory and motor functions of LHS of body ( if right is damaged= sensation of LHS=lost)
-no language capacity b/c no Broca’s area, can’t perform verbal functions on its own
corpus callosum
- Bridge of nerve tissue that connects the two cerebral hemispheres
- allows for communication between the two hemispheres
the 4 divisions of lobes
Frontal lobe
Occipital lobe
Parietal lobe
Temporal lobe
Primary motor cortex of Frontal lobe, function and how is it organised
- controls voluntary bodily movement of skeletal muscles, controls simple motor skills
- organised contra-laterally
-Areas of specialisation are organised so that parts higher on the body are controlled e.g lips by the lower parts of PMC and vice versa
Broca’s area
- Broca’s area is a region in the frontal lobe of the left hemisphere
Broca’s area is linked to:
* Producing speech articulate speech
* coordinates muscles responsible for clear speech (e.g tongue, mouth, vocal cords)
* Capacity to use words other than simple nouns and verbs
* Capacity to at add suffixes to words
* Capacity to produce written language
Primary auditory cortex of temporal lobe
- sound processing and higher level auditory processing (recognising aspects of sound which are specific to speech)
-verbal sound are mainly processed in Left Hemisphere
-non -verbal (e.g music) are mainly processed in right hemisphere
Wernicke’s area
- Wernicke’s area (Temporal lobe) →
Involved in the comprehension of speech (i.e., making sense of verbal communication).
what is Broca’s Aphasia
(non-fluent aphasia)
the damage to Broca’s area and characterized by non-fluent speech, language comprehension is normal, person is aware of their problems
what is Wernicke’s Aphasia
(fluent aphasia)
-results in deficits in the comprehension of language
-severe= complete absence of understanding language (verbal, written or sign)
-speech is fluent but it may not make sense to listeners and patients don’t understand what they are saying=meaningless speech or jargon aphasia
- patients= unaware of problems, can’t function independently
Function of Nervous System
-It receives and processes sensory information from the environment and transmits motor information around the body, that, in turn, determines our reaction to environment stimuli.
Damage to primary auditory cortex?
e.g stroke= might cause deficits in ability to detect changes in pitch, localize sound in space or understand speech
What is aphasia?
is an impairment in language production or comprehension brought by neurological damage
Association areas of temporal lobe
-memory= linked to hippocampus= essential for converting short term memories to long term, linking emotions to memory, determining appropriate emotional responses to memory
-face and object recognition
Damage to temporal lobe?
-lead to amnesia= inability to recognise someone as a person they know or a place
Other functions of frontal lobe/ executive functions
-planning, personality, judgement, decision making, thinking, feeling, behaving, impulse control
-it is the end point for most sensory info that is processed by other lobes, coordinates functions of other lobes
homunculus?
-is a visual representation of what the body would look if there was a 1:1 ratio of cortical area to body parts
Parietal lobe, Primary Somatosensory cortex (primary cortical area), function?
function of primary ss cortex= receives and processes information from skin and body, enabling perception of bodily sensations,
-other function of parietal lobe=
visual attention, spatial reasoning (e.g interpreting maps), locating objects
How is primary Somatosensory cortex organised?
-Contralaterally
-separated from motor cortex in frontal lobe by the central sulcus
-parts higher on the body e.g lips are controlled by the lower parts of PMC and vice versa
Homunculus and somatosensory cortex
body parts that are have more sensory receptors/ more sensitive to sensory stimuli e.g the lips will receive more areas of the cortex than others compared to those that are less sensitive e.g neck
