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.