IC1 Anatomy Flashcards
CNS includes:
- Brain
- Spinal cord
Brain is located in ______, protected by ____________
Brain is located in cranial cavity, protected by skull and meninges
Spinal is located in ______, protected by ____________
Spinal cord is located in the vertebral column
Protected by meninges and surrounded by cerebrospinal fluid
*Three layers of meninges:
- Pia mater
- Arachnoid
- Dura mater
Forebrain includes:
- Cerebrum / Cerebral cortex
- Diencephalon (epithalamus, thalamus, subthalamus, hypothalamus)
Hindbrain includes:
- Pons
- Medulla oblongata
- Cerebellum
Brainstem includes:
- Midbrain
- Pons
- Medulla oblongata
Midbrain contains:
- Colliculus (integrates visual, auditory, and somatosensory spatial information to initiate orienting movements of the eyes and head toward salient objects in space)
- Dopamine cells, serotonin cells
*Damage to the midbrain causes movement disorder and failure to derive pleasure
What is the largest part of the brain?
Cerebrum
- consists of two cerebral hemispheres
The two hemispheres of the cerebrum are separated by ________ and held together by _________
Separated by longitudinal fissure
Held together by large band of fibers called corpus callosum
*Corpus callosum connect homotropic areas of one hemisphere with the other, to allow left and right hemispheres to communicate
What is the cerebral cortex?
Cerebral cortex is a layer of grey matter on the surface of the hemispheres
Grey matter VS White matter
Grey matter - consists of cell bodies, neurons, glia
White matter - consists of axons
Gyri VS Sulci
Gyri: coiled surface structures
Sulci: grooves
Describe the separation of the frontal, parietal, temporal, and occipital lobes
Central sulcus separates the frontal and parietal lobes
Lateral sulcus/fissure separates the temporal lobe from the frontal/parietal lobes
Parieto-occipital sulcus separates the parietal and occipital lobes
Functions of the frontal, parietal, temporal, and occipital lobes
Frontal:
- cognition, decision making, movement (motor)
Parietal:
- taste, smell, somatosensory (touch, pain, temp, proprioception)
Temporal:
- Formation of memory, hearing
Occipital:
- Vision
Hypothalamus position
Hypothalamus forms the lower part of the lateral wall and floor of the third ventricle
(above the midbrain and below the thalamus)
What are the cranial nerves in the midbrain?
Cranial nerves III, IV
Midbrain has nuclei associated with:
III, IV, V
Visual and auditory pathways (optic chiasm)
What are the fiber tracts in the midbrain?
Ascending and descending fibers
Pons is located in the _________
Located in the hindbrain, inferior to the midbrain
Cranial nerves in the pons
V, VI, VII, VIII
Pons has nuclei associated with:
V, VI, VII, VIII
What fiber tracts in the pons
ascending and descending fibers
What is the most inferior portion of the brain?
Medulla oblongata
Cranial nerves in the medulla oblongata
IX, X, XI, XII
Medulla oblongata has nuclei associated with:
V, IX, X, XI, XII
Cardiovascular and respiratory function (e.g., heartbeat, breathing)
What fiber tracts in the medulla oblongata
ascending and descending fibers
Where is the cerebellum located?
What does it consist of?
Posterior to the pons and medulla oblongata, connected to the brainstem posteriorly
Consists of a midline portion (vermis) and is divided into two cerebellar hemispheres (connected by the brainstem)
Involved with coordinated motor control
How is the spinal cord connected to the brain?
Foramen magnum
- passage of the CNS through the skull
Terminal end of the spinal cord is called:
Conus medullaris
- Typically occurs at the L1 vertebral level in the average adult
What are the type of cells in the CNS
- Neurons
- Glial cells (many diff types) - include oligodendrocytes, astrocytes, microglia
Function of neurons
- Generate/conduct impulses and are excitable
Function of glial cells
- Support and protect neurons
- Non-conducting
- 10 times the number of neurons
Structure of a neuron:
- Cell body (Soma) - also known as perikaryon
- Axon (conduct impulses away from soma)
- Dendrites (conduct impulse towards soma)
(IC2) Axons
- Axon hillock (contains trigger zone) - part of cell body
- Initial segment of axon - proximal part of the axon
- Axonal branch or collaterals
- Presynaptic axon terminal
(IC2) Types of neurons
- Multipolar: single axon, one or more dendritic branches
- Unipolar, pseudounipolar, bipolar
[Neuron]
- What does the cell body / soma contain?
- Nucleus
- Golgi complex
- Mitochondria
- Cytoplasmic organelles
- Cytoskeletal elements
- Inclusions
- RER (nissl body - clumps of RER), SER
[Neuron]
Axon structure
- Long, slender processes that arise from the axon hillock in the cell body
- Branch at the distal terminal end, axon collaterals
*Axon hillock contains the trigger zone
[Neuron]
Axonal cytoplasm (axoplasm) lacks ________
Implications
Lacks ribosomes, RER, and golgi apparatus
Therefore, unable to synthesize new proteins or degrade old ones
Material transported back and forth between cell body and the axon terminus
[Neuron]
What are the two types of transports between the neuron and its axon terminus?
- Anterograde transport
- away from cell body to axon terminal
- Retrograde transport
- away from axon to cell body (Return to cell body)
[Neuron]
Fast component vs slow component
Fast component (50-400mm/day) transports cytoplasmic proteins and macromolecules that are required for metabolic and synaptic activity (e.g., metabolites, synaptic vesicles, glucose)
Slow component (1-4mm/day) transports cytoskeletal components
[Neuron]
Dendrite structure
Components
Relatively short, and highly branched
Contain all the cytoplasmic components found in the cell body, except the Golgi apparatus
They still have ribosomes and RER, hence don’t require protein transport from cell body
[Neuron]
Postsynaptic target for excitatory synapse is the dendrite.
Excitatory synapses are formed on top of the ________
Dendritic spines
What is the presynaptic membrane?
A thickened region in the plasmalemma of the presynaptic axon terminal, that contains Ca2+ channels
What is the synaptic cleft?
20-40nm wide space separating the presynaptic and postsynaptic membranes across which a neurotransmitter diffuses
What is the postsynaptic membrane?
A thickened region in the plasmalemma of the receiving dendrite, containing neurotransmitter receptors
[Glial cells in the CNS]
Structure of astrocytes
25%
Structure:
- Largest in size
- Expanded end-feet (pedicles) that terminate on capillaries or on the pia mater
[Glial cells in the CNS]
Types of astrocytes
Fibrous astrocytes
- Primarily in white matter
- Long, spindly processes with few branches
- Branched onto vessels to form BBB
Protoplasmic astrocytes
- Located in gray matter
- Thick, lightly branched processes
- Closely apposed to neuron cell bodies
- Branched onto neuron cell bodies for structural support
[Glial cells in the CNS]
Functions of astrocytes
- Regulate the composition of the intercellular environment and the entry of substances into it (what goes in and out of neurons)
- Blood-brain barrier, mediate exchange of nutrients and metabolites between blood and neurons
- Metabolize neurotransmitters - regulates glutamate homeostasis (e.g., glutamate glutamine shuttle)
- Structural support to neurons, specifically synapses (astrocytic process holds pre and post synapses together, prevent cleft from becoming too wide)
- Scar formation
- Secretion of nerve growth factors
- Water transport
- Excess transport - cerebral edema
Astrocytes have their own membrane potential
[Glial cells in the CNS]
Explain what is meant by tripartite synapse of astrocytes
Tripartite Synapse
- Involve axon, astrocytic process, dendritic spine
- Bidirectional communication between astrocytes and neurons
[Glial cells in the CNS]
Structure and function of oligodendrocytes
60-80%
Predominant type of neuroglial cell in the white matter
- Produce myelin sheath around myelinated fibers in the white matter (one oligodendrocyte => myelin sheath for multiple axons)
In the gray matter,
- Oligodendrocytes are closely associated with neuron cell bodies, functioning as satellite cells (structural support to neurons)
[Glial cells in the CNS]
Oligodendrocytes cell marker:
CNPase
[Glial cells in the CNS]
Oligodendrocytes express _________
Nogo-A
- myelin associated neurite-outgrowth inhibitor - inhibits axonal regeneration following injury and ischemia in the CNS
[Glial cells in the CNS]
Function of microglia
5-10%
Small phagocytic cells that enlarge and become mobile after injury to the CNS
- Brain macrophages (monocyte origin), phagocytosis
- Secretion of proinflammatory cytokines (TNF-a and IL 1B), chemokines
- Antigen presentation function (MCHII antigen)
- Immunocompetent cells of the CNS
*Implicated in alzheimer’s disease, parkinson disease, cerebral ischemia (stroke)
PNS includes:
12 pairs of cranial nerves
31 pairs of spinal nerves
- 8 pairs cervical spinal nerves
- 12 thoracic spinal nerves
- 5 lumbar spinal nerves
- 5 sacral spinal nerves
- 1 coccygeal nerve
PNS is composed of:
- Neuron processes and cell bodies located outside the CNS
- Neuroglial cells (Schwann cells and Satellite cells)
- Nerve endings (afferent, efferent)
Peripheral nerve structure:
- Fascicles/bundles of nerve fibers (axons) that are surrounded by myelin sheaths or Schwann cells
- Multiple fascicles make a nerve
- Consist three connective tissue elements: epineurium, perineurium, endoneurium
[PNS]
Epineurium
Connective tissue surrounding the entire nerve (ensheaths all the fasicles)
[PNS]
Perineurium
Layer of dense connective tissue around each fascicle of nerve fibers
[PNS]
Endoneurium
Thin, reticular layer that surrounds each individual nerve fiber (axon) and contains Schwann cells
[PNS]
Function of Schwann cells
- Schwann cells form the myelin sheath around myelinated axons
- Individual Schwann cells myelinate portions of only one single axon (VS oligodendrocytes - branched, myelinate several axons)
[PNS]
Structure of peripheral ganglion
- Ganglia are encapsulated collections of neuron cell bodies, located outside the CNS
- Contain satellite cells (for structural support) and connective tissue elements along with neurons
- Nerve fibers
E.g., dorsal root ganglion - conduct impulses from cutaneous receptors and proprioceptors to the brain and spinal cord
[PNS]
Satellite cells (amphicytes)
Satellite cells form a capsule of cells around neuron cell bodies located in the peripheral ganglia
Provide structural support
