Module 2: The Central Nervous System Flashcards
In general, what does the afferent division of the PNS do?
Carry sensory information from the periphery to the CNS
In general, what does the efferent division do?
Sends instructions back to the periphery from the CNS
Describe the structure and function of afferent neurons
- Found in the PNS
- Peripehral ending has a sensory receptor
Describe the structure and function of interneurons
- Found only in the CNS
- Make up 99% of neurons
- Are “connector” neurons that lie between afferent and efferent neurons
- Play a role in creating neural circuits for integrating responses to peripheral information
Play a role in higher brain functions
Describe the structure and function of efferent neurons
- Cell bodies lie within CNS where they receive presynaptic inputs
- The efferent axon lies mainly outside the CNS
Describe glial cells
- Do not initiate action potentials
- Use chemical signals to communicate with other glial cells and neurons
- Form the connective tissue of the brain
- Modulate some neuronal activities
- Plays a role in learning/memory
- Most numerous cells in CNS
What are the 3 meninges?
Dura mater, Arachnoid mater, pia mater
Describe the dura mater
- Outermost membrane
- Tough and durable
- Always in contact with skull bone except where they separate to create the dural sinsuses
What is the dural sinuses? What occurs in there?
- Space between the dura mater and skull bone. Venous blood from the brain drains into these sinuses to be returned to the heat. Cerebral spinal fluid also sometimes drain into here
Describe the arachnoid mater
- Middle meninges
- More delicate than dura mater
- Highly vascularized
What is the arachnoid granulation villi
Projection of the arachnoid mater through the dura and into the dual sinuses that allows transfer of cerebrospinal fluid from subarachnoid space to cross the villi into the blood of the sinuses
Describe the pia mater
- Intermost membrane
- Highly vascularized
- Tightly adhered to surface of brain and spinal cord
- In some areas, dips into brain to bring blood supply to the ependymal cells lining the ventricles
What are the functions of Cerebrospinal fluid (CSF)? Where is it located?
- Protects brain by acting as a shock-absorber
- Brain is suspended in it
- Located within the subarachnoid space (between arachnoid and pia mater)
- Aids in transfer of materials between blood and neuronal tissues
- Influences the composition of the brain’s interstitial fluids
- CSF is replaced more than 3x a day
The meninges cover and protect only the brain (T/F)?
False! They cover the spinal cord too
What is grey matter?
Neuronal cell bodies, short interneurons, and glial cells
- Also contain a central canal filled with CSF
What is a “horn”?
Grey matter. Each half of grey matter is separated into regions called ‘horns’
What is white matter?
Bundles of nerve fibres (axons)
- Each bundle is connected to a specific region of the brain to transmit info from the brain to the periphery/from the periphery to the brain
What does “ascending” and “descending” tracts refer to?
White matter
the __ horn contains cell bodies of efferent motor neurons
ventral
the __ horn contains cell bodies of autonomic efferent fibers
lateral
The cell bodies for afferent nerves located outside the spinal cord are called what?
Dorsal root ganglia
the dorsal root contains __ input
afferent
the ventral root contains ___ output
efferent
What are nerve fassicles?
Bundles of myelinated/unmyelinated axons in connective tissues and blood vessels
How many cervical nerves are there in the spine? Where do they emerge from?
- 8 pairs
- Emerge from neck
How many thoracic nerves are there? Where do they emerge from?
- 12 pairs
- Emerge from chest
How many lumbar nerves are there? Where do they emerge from?
- 5 pairs
- From abdomen
How many sacral nerves are there? Where do they emerge from?
- 5 pairs
- From pelvis
How many coccygeal nerves are there? Where do they emerge from?
- 1 pair
- From coccyx (tailbone)
What are the two principle functions of the spinal cord?
- Being the conduit for transmitting information between the brain and the periphery
- Integrating certain afferent inputs and efferent outputs that bypass the brain itself
What are the 5 components to the reflex arc?
- Receptors in skin
- Afferent neuron
- Interneuron
- Efferent neuron
- Effector
What is a simple reflex?
Reflexes that are generally integrated in the spinal cord/brainstem
What is an acquired reflex?
A reflex processed in higher brain centres
What is the oldest and least specialized portion of the brain?
The brainstem
What is the newest and most specialized portion of the brain
The cerebrum
What structures does the brain stem consist of?
- The midbrain, pons, and medulla oblongota
Why is the brainstem so vital in terms of neuronal communication?
All neuronal communication passes through the brainstem. Most neurons have synapses within it and then are moved for further processing. It is the link between the spinal cord and higher brain centres
The brain stem assists in/ functions in/controls:
- Hearing
- Eye movement
- Facial sensations
- Taste
- Swallowing
- Movements of face/neck/tongue
- Vegetative functions of cardiovascular, respiratory and digestive functions
- Muscle reflexes involved in posture and equilibrium
- Reticular information
- Sleep
The diencephalon consists of what structures?
- Thalamus
- Hypothalamus
- Epithalamus
- Subthalamus
Where are the thalamus and hypothalamus located?
-Upper end of brainstem
What are the functions of the thalamus and hypothalamus? (4)
- Relays sensory information between brain regions
- Controls many autonomic functions
- Connects the nervous and endocrine system
- Controls emotion in conjunction with limbic system
Describe the function and location of the thalamus
- Located deep within the brain
- An integrating centre for sensory input
- Can amplify/increase importance for signals of specific interest
Describe the function of the hypothalamus
- An integration center for homeostatic functions
- Link between autonomic nervous system and endocrine system
Roles of hypothalamus (8)
- Controls production and secretion of pituitary hormones
- Plays a role in sleep/wake cycle
- Acts as an autonomic nervous system coordinating centre
- Controls uterine contraction and milk ejection
- Controls fluid intake
- Influences urine output and thirst
- Involved in emotion and behaviour
- Controls body temperature
Describe the structure of the cerebral cortex
- Composed of grey matter
- Divided into left and right hemispheres
- Consists of 6 layers
What are the left and right hemispheres connected by?
The corpus callosum
What are the 4 lobes of the cerebral cortex?
- Frontal lobe
- Parietal lobe
- Occipital lobe
- Temporal lobe
What is the function and location of the frontal lobe?
- Responsible for voluntary motor activity, speech, and elaboration of thought
- Located at front of head
What is the function and location of the parietal lobe?
- Responsible for receiving and processing sensory input
- Located between frontal and occipital lobes
What is the function and location of the occipital lobe?
- Responsible for initial processing of vision input
- Located at back of head
What is the function and location of the temporal lobe?
- Involved in vision and hearing
- Located on sides of head
What is the somatosensory cortex?
- Receives physical sensations
- Somatosensory cortex receives input from sensory information that occurred on opposite side of body
Where is the primary motor cortex found?
In the frontal lobes
What separates the somatosensory cortex and primary motor cortex?
The central sulcus
Describe the function and location of the cerebellum
- Involved in integration of motor control and sensory perception
- Contributes to muscle tone, coordination, and precision of movement
- Located underneath and posterior to the cerebrum
What 3 parts make up the cerebellum?
- The vestibulocerebellum
- The cerebrocerebellum
- The spinocerebellum
What is the function of the vestibulocerebellum?
Important for balance, spatial orientation, and control of eye movement
What is the function of the cerebrocerebellum?
Receives all input form cerebral cortex
important in planning of voluntary movement and evaluation of sensory information
What is the function of the spinocerebellum?
Regulates skilled, voluntary movements
Receives proprioceptive input to allow continuous fine-tuning of movement
What is the function and location of the basal ganglia?
- Consists of grey matter located within cerebral white matter
- Associated with motor, cognition, emotions and learning
- Connected to many other brain regions
- Linked to hypothalamus and thalamus (can even exert an inhibitory effect on the thalamus)
What are the 4 structures of the basal ganglia?
- Caudate nucleus
- Putamen
- Globus palllidus
- Claustrum
What motor control related functions does the basal ganglia have?
- Can inhibit muscle tone throughout the body, allowing precise changes
- Can permit purposeful motor activity while suppressing unwanted movements
- Helps monitor and coordinate contractions, like those relating to posture
What structures make up the limbic system?
Lobes of the cerebral cortex, basal ganglia, hypothalamus and thalamus
What is the function of the limbic system?
Associated with emotions, behaviour, motivation, and learning
Describe positive punishment
The addition of something to decrease behaviour
Describe negative punishment
The removal of something to decrease behaviour
Describe positive reinforcement
The addition of something to increase behaviour
Describe negative reinforcement
The removal of something to increase behaviour
Describe short term memory
- Available from 30 seconds - multiple days
- Majority of these memories will be forgotten and pushed out of brain to make room for more memories
Describe long term memory
- Available for years
- Memories of information/skills that are used often are rapidly accessible
- Less frequently accessed long term memories are slower to recall, but can be accessed more quickly. through sensory connections
What role does the hippocampus play in memory
- Involved in short term memory storage
- Important for consolidation and the initial storage of long-term memories
- Important to declarative memories
What are declarative memories?
“what” memories
people, places, facts, etc
What role does the cerebellum play in memory?
- Important role in procedural memories
- Memories here can be recalled without conscious effort
What are procedural memories?
“how to” memories
motor skills
What role does the prefrontal cortex play in memory?
Important for the complex reasoning skills associated with working memory
Responsible for the executive functions involving integration of information for planning, juggling priorities, problem solving, and organizing activities
What is habituation? How does it affect the neurons involved?
- A decreases responsiveness to repetitive presentations of an indifferent stimulus that neither rewards nor punishes
- Depresses synaptic activity of the neurons involved
What is sensitization? How does it affect the neurons involved?
- Increases responsiveness to mild stimuli that occurs following a strong stimuli
- Enhances synaptic activity
