Unit 5: The Central Nervous System (CNS) Flashcards
What are the components of the CNS?
The brain and spinal cord
What is the difference between afferent and efferent divisions?
Afferent divisions carry information to the CNS, where as efferent divisions carry information away from the CNS.
*Provide status reports on internal activities.
What are the 2 divisions of the efferent division?
Somatic Nervous System: Consists of fibres of motor neurons that supply skeletal muscle.
Autonomic Nervous System: Fibres that supply smooth muscle, cardiac muscle and glands.
What are the 2 divisions of the Autonomic Nervous System?
Sympathetic Nervous System & the Parasympathetic Nervous System
What are the three types of functional neurons?
Afferent neurons, interneurons and efferent neurons.
What are Afferent Neurons?
- Exist in the afferent pathway, and carry electrical impulses to the CNS.
- Receive information in the form of an action potential, picking up the action potential at the terminal end of a long, afferent fibre.
What are Efferent Neurons?
- Primarily in the PNS
- –>Influence their output on effector organs.
- Transfer information through a long, efferent fibre.
What are Interneurons?
99% of all neurons.
- These CONNECT afferent, efferent and interneurons to one another.
- Important for integrating peripheral responses.
What are 90% of cells in the body?
Glial cells (non-neuronal cells) *Communicate with other cells and help maintain homeostasis.
What are the 4 types of Glial cells?
-Astrocytes, Oligodendrocytes, Microglia, and Ependymal cells
What are Astrocytes?
-Hold neurons together (like glue) **
What are Oligodendrocytes?
-Form the insulative myelin sheath around axons of the CNS.
What are Microglia?
- Have phagocytic properties in the cell
- Immune cells of the CNS (Like WBC’s)
- Release Nerve Growth Factor, that helps other glial cells thrive.
- When trouble occurs in the cell, microglia retract their branches and become highly motile.
What are Ependymal Cells?
- Line internal cavities of the CNS
- Develops a narrow, hollow central canal.
- The ventricles of 4 chambers of the brain run through this narrow, hollow tube which runs to the middle of the spinal cord.
- ->Help form cerebralspinal fluid.
What are the 3 layers of the meninges?
The dura mater, the arachanoid matter and the pia mater.
What is the dura mater?
- Outer most layer of the meninges (has 2 layers)
- When these layers aren’t close together, blood flows through these blood-filled cavities called dural sinuses, or venous sinuses.
- Also allows for the entry of CSF.
What is the arachnoid matter?
- middle layer of the meninges
- ->cow-web like vascularized layer
- ->Subarachnoid layer exists below the archanoid layer, above the pia matter and this space is filled with cerebralspinal fluid.
What is the pia mater?
- Inner membrane of the meninges.
- Most fragile layer
- Highly vascular
- Closely adheres to the CNS structures
- Interacts with the ependymal cells lining the ventricles.
What is Cerebrospinal Fluid?
- Serves as a shock-absorbing fluid for the brain and spinal cord.
- Plays an important role in the exchange of materials between the neuronal cells and their interstitial fluid.
- Carry’s O2, glucose and other essential compounds to glial cells and neurons.
Where is Cerebrospinal Fluid formed?
Cauliflower like masses of pia mater called Choroid Plexuses.
What is the Blood-Brain Barrier? (BBB)
- Consists of epithelial cells
- Permissible exchange of materials from the blood into the brain capillaries and into interstitial fluid is very selective.
- Material ONLY passes through tight junctions. (materials don’t penetrate the plasma membrane)
- Anything large must be transported by blood-brain carriers to enter blood capillaries.
- Can limit drug treatment on the brain.
What are astrocytes role in the BBB?
- Signal blood capillary cells to Tight Junction.
- Participate in cross-cellular transport of material
What is the reason for a stroke?
–>Inadequate blood supply to the brain.
What is Cognition?
The act or process of “knowing”, including both awareness and judgement.
What are the 4 regions of the brain?
- The brain stem
- The cerebellum
- The Diencephalon (thalamus & hypothalamus)
- Cerebrum
What is the main function of the Brain Stem?
- Oldest evolutionary part of the brain.
- Continuous with the spinal cord.
- Has the midbrain, pons and medulla.
- ->Controls respiration, circulation and digestion.
What is the main function of the Cerebellum?
- Concerned with maintaining proper body position (proprioception), as well as subconscious coordination of motor activity.
- key role in learned motor tasks.
What is the main function of the Diencephalon?
- Thalamus is responsible for basic processing & relaying sensory information.
- Hypothalamus is responsible for homeostatic functions, as well as complex functions like sex drive and hunger.
What are the components of the Cerebrum?
- Largest portion of the brain
- Most highly developed in humans
- Outer layer called the cerebral cortex houses the basal nuclei.
- Walnut appearance*
What is the function of the cerebral cortex of the cerebrum?
- Key role in most sophisticated neural functions, including voluntary initiation of movement, sensory perception, conscious thought, language and personality traits.
- Is divided into 2 hemispheres: left and right
What connect the right and left hemispheres of the Brain?
The Corpus Callosum
What is Grey Matter?
-Densely packaged neuronal cells and their dendrites, as well as glial cells.
‘Computers of the CNS’
What is White Matter?
-Myelinated nerve fibres (axons)
Where does integration of neural input occur?
Is initiated at the grey matter, but is transmitted via the white matter. It is then sent from the white matter to higher areas of the brain for further processing.
What is the function of Stellate cells?
Responsible for sensory processing in the cortex
What is the function of Pyramidal cells?
Send fibres down the spinal cord from the cortex, and terminate on efferent motor neurons that supply skeletal muscle.
What are the 4 lobes of the cerebral cortex?
The Frontal lobe, the Occipital lobe, the Parietal lobe and the Temporal Lobe
What is the main function of the Occipital lobe?
- located posteriorally of head (back)
- Carries out initial processing of Visual input.
What is the main function of the Temporal lobe?
-Initially receives sound sensations
lateral- side
What is the main function of the Parietal lobe?
- top of head
- Responsible for receiving and processing sensory input
- Includes the Somatosensory complex, as receptors pick up somatosensory information (touch, pressure, heat, cold, and pain).
What is the function of the Somatosensory Cortex?
-Site of the parietal lobe for initial cortical processing of somesthetic and proprioceptive input.
What is the Sensory Homunculus?
–>A representation of the distribution of sensory input to the somatosensory cortex.
(different for regions of the body)
–>High devotion of sensory perception with the face, tongue, hands and genitalia.
What is the purpose of the Thalamus in somatosensory processing?
-Detects touch, pressure or pain, but it also localizes and MEASURES the source of intensity of the input.
What is the main function of the Frontal Lobe?
- Contains the Primary Motor Cortex, responsible for voluntary control of movement produced by skeletal muscles.
- -Motor cortex controls the opposite side of the hemisphere at which is lays. (left controls right)
What is the readiness potential?
-Occurs 750 msec before electrical activity is detectable by the motor cortex. This activates the motor cortex.
What areas of the brain are involved in voluntary decision making?
- Supplementary motor area
- The Premotor cortex
- Posterior Parietal cortex
* The Cerebellum also sends input to the motor areas of the cortex.
Describe the Supplementary Motor Area:
- Role in programming complex sequences of movement.
- Inner surface of both hemispheres of the primary motor cortex.
- Lesions result in poor performance of movements here.
Describe the Pre-Motor Cortex:
- In front of the primary motor cortex
- Important in orienting the body and arms towards a specific target.
- guided by posterior parietal cortex input
- Damage may result in a loss of motor skills.
What is Plasticity and why is the brain considered this?
- An ability to change or be functionally remodeled.
* Important in evolution
What hemisphere is responsible for language?
Left Hemisphere
What does Broca’s area govern?
- Speaking ability.
- -Located close to the motor areas of the cortex that control muscles for articulation
What is Wernicke’s area?
Concerned with language comprehension
*Receives input from the visual cortex of the occiptial lobe, auditory cortex of the temporal lobe, and somatosensory input for the ability to read braille.
What are the 3 Association areas?
- Involved in high brain functions
- Other half of the cerebral cortex, excluding the motor, sensory and language areas.
- -> Include the
1. Prefrontal Association Cortex
2. The Parietal- Temporal- Occipital Association Cortex
3. The Limbic Association Cortex
What is the main function of the Prefrontal Association Cortex?
Roles include:
- Planning for voluntary action
- Decision making
- **-Creativity and Brainstorming
- Personality Traits
- ->The brain temporarily stores and actively manipulates information used in reasoning and planning.
What is the main function of the Parietal- Temporal- Occipital Association Cortex?
- Pools and integrates somatic, auditory and visual sensations.
- Involved in the language pathway connecting Wernicke’s area to the visual and auditory cortices.
What is the main function of the Limbic Association Cortex?
- Bottom portion adjoining the temporal lobe.
- ->Area concerned with motivation and emotion.
- *Extensively involved in memory
Left Hemisphere characteristics:
- Excels in math, language and philosophy.
- Logical, analytical, sequential and verbal tasks.
- ->THINKERS
Right Hemisphere characteristics:
-Non-language skills
-Spatial perception, artistic and musical talents.
-Holistic thinkers (big picture)
CREATORS
How can extracellular current flow be detected in the brain?
- Using an electroencephalogram (EEG)
* Measure momentary, collective post synaptic potential activity in the brain. (EPSP’s and IPSP’s)
What are the three main uses of an electroencephalogram (EEG) ?
- Clinical tool in the diagnosis of cerebral dysfunction (EPILEPSY)
- Further use in the legal determination of brain death.
- Uses to monitor sleeping patterns.
Alpha waves vs. Beta waves EEG?
Alpha waves are tight knit and rapid (closed eyes)
Beta waves are more linear (open eyes)
What are the subcortical regions of the brain?
Include the basal nuclei, the thalamus and the hypothalamus.
What is the main function of the Basal Nuclei?
-Functions to control motor control, cognition, emotions and learning.
Important in:
1. Inhibiting muscle tone
2. Maintaining purposeful motor control only
3. Coordinates slow, sustained contractions.
Does the basal nuclei directly impact efferent motor neurons?
No, but modifies the pathways at which these neurons travel.
What causes Parkinson’s Disease?
- A deficiency in dopamine, a neurotransmitter of the basal nuclei.
- -> Causes useless and unwanted tremors.
Why is the Thalamus considered a “relay center” ?
- Integrates sensory input on it’s way to the cortex.
- Routes important signals to the correct areas of the somatosensory complex.
Areas of The Limbic System ?
- The cerebral cortex, the the basal nuclei, the thalamus and the hypothalamus.
- associated with emotions, basic survival and sociosexual behavioral patterns, motivation and learning.
What is learning?
Changes made based on experience.
What is Memory Trace?
-The neuronal change responsible for retention or storage of knowledge.
Define Consolidation?
The process of transferring and fixing short term memory traces and building them into long term memory stores.
Is there a memory center in the brain?
-No, there is only memory traces throughout the cortical and subcortical regions of the brain.
What part of the brain is responsible for the “how to” learned memories from repetitive training?
The cerebellum and cortical regions of the brain.
What is the purpose of the vestibulocerebellum of the cerebellum?
-Maintaining balance and controls eye movements.
What is the purpose of the spinocerebellum of the cerebellum?
-Enhances muscle tone and coordinated, skilled, voluntary movements.
What is the purpose of the cerbebrocerebellum of the cerebellum?
-Plays a role in planning and initiating voluntary activity
What region of the brain stores procedural memories?
-Cerebral region
What is the purpose of the brain stem?
–>Controls basic body functions such as breathing, swallowing, heart rate, blood pressure, consciousness, and whether one is awake or sleepy.
The 5 main functions of the Brain Stem?
- 12 cranial nerves arise from the brain stem.
- “Centers” control heart rate and blood vessel formation, respiration and other activites.
- Regulates muscle reflexes.
- Contains Reticular formation, which integrates all sensory synaptic information. Fibres called the reticular activating system controls the overall degree of cortical awareness.
- Governs sleep-wake cycle.
What is Slow-Wave sleep?
-EEG is slow waves…frequent movements.
What is Paridoxal Sleep (REM)
-EEG is that of an awake person.
3 Different Neuronal Systems make up the sleep-wake cycle.
- The arousal system - part of the RAS
- A slow-wave sleep center- neurons induce sleep
- A paradoxical sleep center - houses REM neurons
What is Narcolepsy?
- Unusual sleep disturbance during the day!
- ->People immediately fall into REM sleep.
Spinal Cord Recap.
- Extends from the brain stem.
- contains 31 pairs of spinal nerves
- Central canal of grey matter is surrounded with cerebrospinal fluid.
- The dorsal fin contains interneurons at which afferent neurons terminate.
- The ventral horn contains cell bodies of efferent motor neurons supplying skeletal muscles.
-The thick bundle of elongated nerve roots within the lower vertabrae canal
Cauda Equina
Where do spinal nerves connect within the spinal cord ?
- By a dorsal root (afferent fibres) which are neuronal clusters called dorsal root ganglion and a ventral root (efferent fibres)
- Join to form a spinal nerve.
What is a nerve?
A bundle of peripheral neuronal axons enclosed by a connective tissue covering and following the same pathway.
*Only contains axonal portions of many neurons.
What are tracts?
Bundles of axons in the CNS
What is a reflex?
A rapid, predictable and automatic response to changes in the environment that help maintain homeostasis.
2 types of reflexes: simple reflexes and acquired reflexes.
What is a Reflex Arc?
- The neural pathway involved in accomplishing reflex activity
- ->A receptor responds to stimulus, which produces an action potential relayed on an afferent neuron, which goes to the integrating center for processing. This information is passed onto the efferent pathway and onto the effector- muscle or gland.
The Withdrawal Effect
-Thermal Pain –> Afferent Pathway –> Integrating Center–> Efferent Pathway –> Move Hand
What is Reciprocal Innervation?
-The stimulation of the nerve supply to one muscle and simultaneously inhibiting nerves to its antagonistic muscle.
What is the Stretch Reflex?
- An afferent neuron originating at a stretch- detecting receptor terminates directly on an efferent neuron innervating skeletal muscle.
- ->Causes it to contract and counteract the stretch.
What does Cross Extensor Reflex ensure?
-The opposite limb will be in position to bear the weight of the body as the injured limb is withdrawn from a stimulus.
How are subconscious reactions different from reflex arcs?
Subconscious reactions are mediated by hormones.
