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