Nervous system Flashcards
Order of nervous system response.
- Stimulus presented to organism
- Assessment of stimulus
- Preparation of the response
- Communication to responding structures
- Response
What is hippocampal tri-synaptic circuit?
EC - DG - CA3 -CA1 -EC
Forms memories
Memory and learning explained?
Memories form through neural plasticity (ability of brain or neuron to adjust and respond to new situation or environment.
Long term memories stored in cerebral cortex.
Memory consolidation occurs during sleep.
Insect nervous system
Centralised brain and sense organs
Taste and smell receptors
Antennae
Simple compound eyes
Worms nervous system
Ventral nerve cord formed from fusion of two longitudinal cords in ladder system.
Ganglia in each segment and segmental mini-brains.
Ladder system?
Longitudinal nerve cords
Cephalisation of cerebral ganglia.
Squid nervous system
Collections of neurons in specialised ganglia.
Where are ventral nerve cord and dorsal spinal cords found.
Ventral - invertebrates
Dorsal - Vertebrates
What does spinal cord and brain develop from
Embryonic nerve cord
What is peripheral nervous system composed of?
Nerves and ganglia
Role of afferent and efferent neurons
a - transmit info to CNS
e - transmit info away from CNS
Role of motor system
carry signals to skeletal muscle and voluntary
Role of autonomic system
regulate smooth and cardiac muscles and involuntary.
Role of sympathetic division
Regulates arousal and energy generation (fight or flight)
Epinephrine and norepinephrine
Role of parasympathetic division
Promotes calming and rest and digest functions.
Acetylcholine
Role of enteric division
Controls digesting tract, pancreas and gallbladder
What is brain composed of
White matter - myelinated axons
Gray matter - neuron cell bodies, dendrites and unmyelinated axons
Ventricles
Cerebrospinal fluid (CSF)
Found in central canal of spinal cord and ventricles.
Provides brain with nutrients and removes wastes
roles
Produced by secretory epithelium of choroid plexus.
Shock absorbing - mechanical protection
Homeostatic function
Circulation
Structure of choroid plexus
Network of capillaries in walls of ventricles
Ventricular system
Lateral ventricles
Third ventricles
Fourth ventricles
Lateral connects to third (intraventricular foramina
Third to fourth (cerebral aqueduct)
Fourth to subarachnoid space ( Median aperture - Magendie) (Lateral aperture - Luschka)
Role of embryonic radial glia
forms tracks along which newly formed neurons migrate
Role of astrocytes
Induce cells lining capillaries in CNS to form tight junction, results in blood-brain barrier and restricts entry of most substances into brain
Phases of brain development
Neural plate induction
Neural proliferation
Migration + aggregation
Axon growth and synapse form
Cell death and synapse rearrangement
Induction of neural plate
2-3 weeks after conception
Patch of dorsal surface of embryo that will become nervous system
Development induced by chemical signals
Growth factors - stimulate neuron development
Neural proliferation
3 swelling at anterior end in human forming sections of brain (fore, mid, hind)
Occurs in ventricular zone
Migration
Only a soma and immature axon - undifferentiated at start of migration.
Differentiation starts as neurons migrate
Develop neurotransmitter making ability, AP.
Radial cells guide migration of neurons.
Aggregation
Cells that have done migrating align themselves with other cells forming structures (aggregation).
Axon growth
Axons and dendrites grow to mature size
They form synapse with other neurons
Growth cones and chemo-attractants key for this
Synaptogenesis
Formation of new synapses
Depends of presence of chemical cues from glial cells.
Cell death and synapse rearrangement
45-75% of neurons die after migration
Neurons die due to failure to compete for chemical provided by targets.
Role of neurotrophin
Promotes growth and survival
Guide axons
Stimulate synaptogenesis
Synaptic rearrangement
Release and uptake of neurotrophic factors
Neurons receiving insufficient factor die
Axonal processes compete for limited neurotrophic factor
What factors cause postnatal cerebral development
synaptogenesis
increased dendritic branches
myelination
Lateralization of cortical function
Two hemispheres make distinct contributions to brain functions
Work together by communicating through fibres of corpus callosum
Left hemisphere
more adept at language and logic
Right hemisphere
stronger at patterns, thinking and emotions
Lobes of the brain
Frontal
Parietal
Temporal
Occipital
