Brain Function Part 1 Flashcards
How can a neuron be described?
Building block of the nervous system
What are neurons?
Chemical and electrical information and communication cell
Variable size and structure throughout the nervous system
What are the cellular constituents of neurons and their function?
Microtubules: transportation
Neurofibrils: structural support
Nissl substances: protein synthesis
Will neurons continue to divide?
Some neurons, such as olfactory neurons, will continue to divide
However, others die if they are not needed
What happens if a neuron cell dies?
Cannot be replaced
What are the components of the neuron?
Cell body (soma)
Dendrites
Axons
What are the key features of the cell body (soma)?
Located mainly in the CNS
Nuclei: densely packed cell bodies in the CNS (white matter contains nuclei)
Ganglia and plexuses: group of cell bodies in the PNS
What are the key features of the dendrites?
Receptive portion of the neuron- sends impulses to the cell body
Dendritic zone: receptive portion of the neuron that receives a stimulus and continues further conduction
What are the key features of the axons?
Carry nerve impulses away from cell body
Axon hillock: cone-shaped, organelle-free area where the axon leaves the cell body
What is significant about the axon hillock?
First part of the axon hillock is the area of lowest threshold for stimulation; therefore, action potentials begin here
Why is myelin important for the axon?
Segmented layer of lipid material
Insulating material
Myelin sheath (entire membrane) on axon
Formed and maintained by the Schwann cells
Why are nodes of Ranvier important for axons?
Regular interruptions of the myelin sheath, speeds up transmission of impulses
What is the neurilemma?
Schwann sheath
How can neurons be structurally classified, and what are the names of the classifications?
Structurally classified on the basis of the number of processes extending from the cell body
Can be classified as:
Multipolar (most common)
Bipolar
Unipolar/Pseudounipolar
Anaxonic
What are multipolar neurons and what is an example of one?
Neurons with one axon and two or more dendrites
Motor neurons
What are bipolar neurons and what are examples of them?
Neurons with one axon and one dendrite
Comprise the sensory neurons of the retina, the olfactory epithelium and the inner ear
What are unipolar/pseudounipolar neurons and what are examples of them?
Each have a single process that bifurcates close to the perikaryon, with the longer branch extending to a peripheral ending and the other toward the CNS
Includes all other sensory neurons that aren’t bipolar neurons
What are anaxonic neurons and what are their functions?
Many dendrites but no true axon
Do not produce action potentials, but do regulate electrical charges of adjacent CNS neurons
How do the motor pathway and sensory pathway interact?
Brain will act on stimuli from sensory pathway and send impulses via motor pathway
What are the classifications of neurons based on function?
Sensory neurons
Associational or interneurons
Motor neurons
What is the function of sensory neurons?
Transmit impulses from peripheral sensory receptors to the CNS
Are transmitted via an afferent pathway (Afferent=Arrive)
What are common types of sensory neurons?
Associational or interneurons (transmit impulses from neuron to neuron/CNS)
What is the function of motor neurons?
Transmit impulses from CNS to effector organs (i.e., skeletal muscle or organs)
How are impulses transmitted via motor neurons?
Transmitted via an efferent pathway (Efferent= Exit)
How are motor neurons and neuromuscular junctions linked together?
In skeletal muscle the end processes of an axon form the specialised structure (neuromuscular junction)
Which information is correct regarding associational neurons?
Associational neurons
1. Carry impulses between two distinct processes arising from the cell body
2. Carry impulses from peripheral receptors to the CNS
3. Transmit impulses to an effector organ
4. Transmit impulses from neuron to neuron
ANSWER: 4
These interneurons are multipolar and are involved in cognitive function
1. Bipolar neurons have two distinct processes arising from the cell body and are found in the retina of the eye. These neurons connect the rods and cone cells of the retina.
2. Sensory neurons carry impulses from peripheral receptors to the CNS
3. Motor neurons transmit impulses to an effector organ
What does the term neuroglia mean?
Nerve glue
How many more times numerous are neuroglia compared to neurons?
5-10 times more numerous
What is the main function of the neuroglia?
Supports the neurons of the CNS
What are the neuroglia of the CNS and what are their function?
Astrocytes: Fill the spaces between neurons and surround the blood vessels in the CNS
Oligodendroglia (oligodendrocytes): Deposit myelin within the CNS
Microglia: Remove debris in the CNS
Ependymal cells: Line the cerebrospinal fluid (CSF)–filled cavities of the CNS
What is the importance of astrocytes in the CNS?
Fill spaces between neurons and surrounds the blood vessels
Included in the formation and maintenance of the blood-brain barrier
What is the significance of the blood-brain barrier?
Acts selectively-regulates what passes in the brain and what doesn’t
Need to think if nerve tissue is damaged due to blood-brain barrier breach
What is the importance of oligodendroglia (oligodendrocytes) in the CNS?
Wrap around CNS nerve fibres to form myelin
Deposit myelin within CNS
What is the importance of microglia (microglial cells) in the CNS?
Act like macrophages and remove debris from the CNS
What is the importance of cerebrospinal fluid (CSF)?
“Washes the brain”
What is the importance of ependymal cell in the CNS?
Line the CSF-filled cavities of the CNS
Form sheets
What is the brain protected by in the skull?
The brain is connected to the skull but is protected by the meninges
What are Schwann cells also known as and what are their function?
Also known as neurolemmocytes
Are glial cells that wrap around and cover axons in the PNS
Form and maintain the myelin sheath
What does the term myelinated mean?
Myelin layer is tightly wrapped many times around the axon, forming nodes of Ranvier
Why are nodes of Ranvier useful?
Increase the velocity of conduction
What types of motions does the autonomic nervous system control?
Involuntary, e.g., heart rate, blood pressure, etc.
What can the autonomic nervous system be split into?
The sympathetic nervous system, and the parasympathetic nervous system
What types of motion does the somatic nervous system control?
Voluntary, e.g., muscle movement
What does the central nervous system consist of?
Brain and the spinal cord
What does the peripheral nervous system consist of?
Everything outside of the CNS
Cranial nerves and spinal nerves
What are the pathways associated with the PNS?
Afferent (ascending; sensory to spinal column)
Efferent (descending; innervate effector organs)
What can the peripheral nervous system be split into and what are their functions?
Somatic nervous system:
Motor and sensory pathways regulate voluntary motor control of skeletal muscle
Autonomic nervous system (ANS)
Motor and sensory pathways regulate the body’s internal environment through the involuntary control of organ systems
What can the autonomic nervous system be divided into?
The sympathetic and parasympathetic nervous system
What is significant about all ANS divisions?
They all have acetylcholine –> different neurotransmitters
What type of movement are smooth muscles associated with?
Involuntary
