3: Anatomy of the Nervous System Flashcards
Central Nervous System (CNS)…
Division of the vertebrate nervous system that is inside skull and spine.
Peripheral Nervous System (PNS)…
Division of the vertebrate nervous system that is outside skull and spine.
CNS is made up of…
The brain and the spinal cord.
What two systems make up the PNS?
The somatic nervous system (SNS) and the autonomic nervous system (ANS).
SNS role and constituents…
- Interacts with external environment.
- Made up two types of nerves that carry sensory signals: afferent and efferent.
Afferent nerves…
Approaching CNS; carries sensory signals from muscles, eyes, ears etc. to the CNS.
Efferent nerves…
Exiting CNS; carries sensory signals away from CNS to muscles, ears, eyes, etc.
ANS role and constituents…
- Interacts with internal environment.
- Made up of afferent and efferent nerves.
- Also has 2 kinds of efferent nerves: sympathetic and parasympathetic nerves.
Sympathetic nerves…
- Motor nerves that project from CNS to lumbar (small of back) and thoric (chest) regions of spinal cord.
- Project onto neurons far away.
- Involved in excitatory signals, stimulate in fight-or-flight situations. Arousal.
- Every target organ receives opposing P & S signals.
Parasympathetic nerves…
- Motor nerves that project from CNS to sacral (lower back) region of spinal cord.
- Project onto neurons nearby.
- Involved in inhibitory signals, for energy conservation. Relaxation.
- Every target organ receives opposing P & S signals.
Cranial nerves…
- Exceptional nerves that project directly from brain rather than CNS.
- Include purely sensory nerves such as olfactory and optic nerves.
- Longest cranial nerves: vagus nerves (from gut).
- Functions are very specific, so damage is often directly diagnostic.
Meninges: role and 3 layers…
- 3 protective membranes that act as protectice casing for brain and spinal cord.
- Three layers: Dura mater (tough outer layer), arachnoid membrane (thin inner layer), arachnoid membrane (gap of blood vessels and CSF), and pia mater (fine innermost layer).
Cerebrospinal fluid (CSF) - what is its role and what does it fill?
Protective fluid which fills:
- Subarachnoid space
- Central canal of spinal cord
- Cerebral ventricles of brain
- These are interconnected, forming a reservoir
What is the role of choroid plexuses?
These produce CSF.
Hydrocephalus…
- ‘Water head’
- Excess of CSF due to blockage (i.e. a tumour) near the cerebral aqueduct.
- Treating by draining fluid and removing blockage.
Blood-brain barrier…
- A structure of cerebral blood vessels that blocks the entry of toxic substances from blood into the brain.
- Structured so that blood vessels are tightly packed, preventing most large molecules (exception of glucose) into brain.
Two main cell types in the CNS…
Neurons and glial cells.
Neurons - external: Cell membrane…
Semipermeable membrane that encloses the neuron.
Neurons - external: Dendrites…
Short branches attached to cell body involved in interneural synaptic reception.
Neurons - external: Axon hillock…
Cone-shaped area located between the axon and the cell body.
Neurons - external: Cell Body…
A.K.A ‘soma’; metabolic centre of neuron.
Neurons - external: Axon…
Long connection stemming from cell body.
Neurons - external: Nodes of Ranvier…
Little gaps in between myelin sections.
Neurons - external: Buttons…
On ends of axon branches, release chemicals into the synapses.
Neurons - external: Synapses…
The gaps between adjacent neurons, whereby the chemical signals are transmitted.
Neurons - internal: Endoplasmic reticulum…
- Rough and smooth folded membranes inside cell body.
- The rough folds contain ribosomes, and are involved in the synthesis of proteins.
- The smooth folds don’t contain ribosomes, and are involved in synthesis of fats.
Neurons - internal: Cytoplasm…
Clear internal fluid of cell.
Neurons - internal: Golgi complex…
Connected body of membranes involved in packaging of molecules in vesicles.
Neurons - internal: Nucleus…
Sphere containing DNA-structure.
Neurons - internal: Mitochondria…
Sites of oxygen-consuming energy release.
Neurons - internal: Microtubules…
Involved in rapid transport of substances throughout neurons.
Neurons - internal: Synaptic vesicles…
Little balls that are packed with neurotransmitter molecules ready for release near synapses.
Neural cell membrane…
A lipid bilayer embedded with signal and channel proteins.
Projection-based classes of neurons…
- Multipolar
- Unipolar
- Bipolar
- Interneurons
Nuclei…
Clusters of cell bodies within the CNS.
Ganglia…
Clusters of cell bodies within the PNS.
Tracts…
Bundles of axons within the CNS.
Nerves…
Bundles of axons within the PNS.
Glial cells: Oligodendrocytes…
Glial cells with extensions that enable contact with some neurons in the CNS.
Similar function to Schwann cells.
Schwann cells…
Glial cells with extensions that enable contact with some neurons in the PNS.
Similar function to oligodendrocytes, but only Schwann cells have a role in axonal regeneration/regrowth.
Glial cells: Microglia…
Involved in triggering inflammatory responses as response to injury or disease.
Glial cells: Astrocytes…
- Have a lot of recently discovered roles in brain.
- Play a role in allowing and blocking passage of chemicals from blood into CNS.
Golgi stain…
A staining process in which silver chromate stains individual neurons, showing a stenciled structure.
Nissl stain…
Specifically stains layers containing high number of cell bodies, using cresyl violet. Useful for estimating number of neurons in an area and nature of inner structures.
Electron microscopy…
Used to look at intricacies of neuronal structure. Electron micrographs are used for observing finer details of individual neurons.
But harder to pick out individual neurons because of level of detail.
Types of neuroanatomical tracing techniques…
- Anterograde
- Retrograde
- Traces are injected and absorbed by terminal buttons which then transport these chemicals along axons.
Anterograde tracing tehcniques…
Used to trace axonal paths AWAY from cell bodies in particular area.
Retrograde tracing techniques…
Used to trace axonal paths TOWARDS a particular area.
Spinal cord basically consists of two substances…
Inner core of grey matter, and an outer core of white matter.
Grey matter core…
Consists of unmyelinated interneurons.
White matter surround…
Consists of myelinated axons.
Grey matter has a set of arms…
2 dorsal horns, and 2 ventral horns.
Dorsal root ganglia…
Joins the axons of all spinal nerves that are unipolar, afferent, and sensory.
Ventral root ganglia…
Joins the axons of all spinal nerves that are multipolar, efferent, and motor.
Inverse descent and alphabetical order: Five swellings of the brain…
Telencephalon, diencephalon, mesencephalon, and metencephalon, myelencephalon.
The forebrain contains…
The telencephalon and the diencephalon
The midbrain contains…
The mesencephalon.
The hindbrain contains…
The metencephalon and the myelencephalon.
Myelencephalon…
- Contains reticular formation, which is involved in arousal and attention, but also basic behaviours like sleep and respiratory reflexes.
The metencephalon: Cars Rushing Past
Contains the cerebellum, reticular formation, and pons.
The mesencephalon: Topsy Turvy
Two divisions: Tectum and tegmentum.
Tectum: See Inside…
Contains:
- Inferior colliculi: posterior, auditory function.
- Superior colliculi: anterior, visual function.
Tegmentum: Thrashing Rivers, Cursed Seas, Ruined Ponds.
Contains:
- Reticular formation
- Periaqueductal grey - surrounds cerebral aqueduct, connects 3rd and 4th ventricles. Role in analgesic effects.
- Substantia nigra
- Cerebral aqueduct
- Red nucleus
Diencephalon: Time Passes, but Man Holds On
Contains thalamus, pituitary gland, hypothalamus, and optic chiasm.
Thalamus…
- Two-lobed structure joined by massa intermedia.
- Contains important sensory relay nuclei, such as:
Lateral geniculate, medial geniculate, and ventral posterior nuclei.
Hypothalamus…
- Role in 4 Fs of motivated behaviour.
- Effects are generated by regulation of pituitary gland hormonal release.
Telencephalon: Golden Leaves Fall, Crumbling Beneath Crushing Footsteps.
Contains:
- Cerebral Cortex
- Major gyri
- Major fissures
- Limbic System
- 4 lobes
- Basal ganglia
- Corpus callosum
Major fissures…
Central, lateral, and longitudinal.
Major gyri…
Precentral, postcentral, and superior temporal.
Occipital lobes…
Visual analysis.
Parietal lobes…
Sensation analysis (e.g. touch).
Temporal lobes…
- Superior temporal gyrus: language and hearing.
- Inferior temporal cortex: Complex visual patterns.
Frontal lobes…
- Precentral gyrus and adjacent frontal cortex: motor function.
- Frontal cortex: complex cognitive functions.
90% of the human brain is…
Neocortex.
I - VI layers of cells which differ in density, thickness, and ratio of pyramidal to stellate cells.
2 main types of cortical neurons…
Pyramidal and stellate cells.
Pyramidal cells…
- Pyramid-shaped.
- Large, multipolar neurons with long axons.
Stellate cells…
- Star-shaped.
- Small interneurons.
Columnar organisation…
Refers to vertical organisation of cells (and therefore flow of information).
Hippocampus…
- Is not part of neocortical area.
Limbic System: Master Sings And Creates Fine Hats
- Regulation of 4Fs. Contains: - Mammillary bodies - Septum - Amygdala - Cingulate Cortex - Fornix - Hippocampus
Basal Ganglia: Almond Cake, Please Stay Great
Contains:
- Amygdala
- Caudate
- Putamen
- Striatum
- Globus Pilladus
Nucleus accumbens…
- Another part of basal ganglia.
- Thought to have role in rewarding effects of addictive drugs and other reinforcers.
