Neural tissues Flashcards
The purpose of the NS is communication. Be more specific about the purpose of the CNS and the PNS
CNS (derived from ectoderm)
Info processing including reflexes and behaviour
PNS
Sensory detection and motor activation
How does the magnitude of neurons in the brain compare to those of the enteric nervous system?
Brain: 10^11 neurons, 10^14 synapses 1.5kg
ENS: 10^8 neurons (> spinal cord)
Define nucleus, afferent neuron, efferent neuron and ganglion
Nucleus- a group of neurons.
Central nuclei- big neurons/ Eccentric nuclei- small neurons
Afferent neuron- transmit sensory info to brain/spinal cord e.g dorsal root ganglion
Efferent neuron- motor neurons transmitting info from brain to effector organ
Ganglion- group of cell bodies outside CNS
What is Broadmann area?
State that of the primary motor and visual cortex
SYSTEM FOR NAMING CORTICAL AREAS. 1-52
Boundaries determined by cellular architecture
Each has a particular set of inputs/outputs, often has a function
4= Primary motor cortex 17= Primary visual cortex
What is a process?
What is a CNS neuron?
Outline the structure of a CNS neuron
Outgrowth from cell body of neuron e.g. dendrites, axons
Nucleus within cell body and extends 1+ processes
(from input to output)
Dendrites, axon hillock, axon, axon collaterals, myelin sheath, nodes of ranvier, axon terminals (synaptic boutons)
What is myelin?
Made of many layers of cell membrane
Electrically insulates and increases diameter–> increases conduction velocity
Neurons can be classified as multipolar, bipolar, pseudo-unipolar and unipolar. Define and give an example for each.
Multipolar have 1 axon but have several dendrites e.g. Purkinje cell
Bipolar neurons have two processes extending from the cell body e.g. Least numerous sensory neurons-retinal cells, olfactory epithelium cells, pyramidal cell
Pseudo-unipolar cells (example: dorsal root ganglion cells). These cells have 2 axons rather than an axon and dendrite. One axon extends centrally toward the spinal cord, the other axon extends toward the skin or muscle./ 1 axon, 1 dendrite
Synaptic transmission is unidirectional
State the length of the synaptic cleft
Define divergent and convergent in terms of synaptic transmission
Define an interneuron/motor neuron
Approx 30nm
Divergent- a single neuron sends output signal to many neurons e.g. skin
Convergent- multiple inputs influence a single neuron e.g. retina
Neither motor or sensory. They PROCESS signals. Occur only in CNS
Generally speaking, what are glia?
Non-neuronal cells in the CNS Supportive and protective function No AP's Do not form synapses Able to divide ** . most common source of tumours of NS Form myelin sheaths Many more glial cells to neurons
Consider glial pathology. Describe a glioma
Largest group of primary tumours derived from glial cells
Usually malignant
Grow rapidly
Difficult to remove surgically, usually intracranial
Consider glial pathology. Describe a neuroblastoma
Most common in children
Extracranial
Survival varies and survivors usually develop neurological disorders later
Derived from neural crest cells from SNS
Increased catecholamine levels (adrenaline) due to SNS involvement
Describe a microglial cell
CNS
Looks like a crab
Mesodermal origin- develop from monocytes
Functions:
1. immune cells- protect neurons from disease
2. migate to injury sites
3. engulf microbes/debris
Describe an oligodendrocyte
CNS
Looks like an armed cell with large nuclus
Production/maintenance of myelin sheath in CNS
1 oligodendrocyte myelinates multiple axons from different neurons
Describe a schwann cell
PNS Production/maintenace of myelin sheath, only in PNS regeneration 1 axon: schwann cell Wrapping creates multiple lipid bilayer Surrounded by collagen fibres
Describe a satellite cell
PNS
Supports neurons, regulate exchange of materials between neurons and interstitial fluid
Perform analogous role in PNS to astrocytes in CNS
