Organization of the Nervous System Flashcards
what are the two divisions of the peripheral NS
autonomic (communicates with internal organs and glands
somatic (communicates with sense organs and voluntary muscles)
what are the two divisions of the somatic NS
sensory (afferent) - sensory input
motor (efferent) - motor output
what are the two divisions of the autonomic NS
sympathetic
parasympathetic
what is the peripheral NS composed of
peripheral, cranial and spinal nerves that carry information to and from the CNS
what are the 7 basic parts of the CNS
spinal cord, medulla, pons
midbrain, cerebellum, diencephalon
cerebral hemispheres
what three structures make up the brainstem
medulla, pons and midbrain
what two structures make up the diencephalon
thalamus (relay station that sends info where it needs to go) and hypothalamus
what two structures make up the forebrain
cerebral hemispheres and diencephalon
as you go from the brainstem to the cerebral hemispheres how does the information that is carried change
it gets more specific
- damage to the brainstem is often fatal because it’s involved in basic survival functions
- stroke higher up causes more specific impairments
what are the two-way conduction pathways the spinal cord provides
motor control to body from brain (descending)
sensory perception from body (ascending)
what two types of innervation is the spinal cord involved in
sensory and motor
what is the function of the brainstem
relays information from the spinal cord to the cerebrum and cerebellum
regulates vital functions (breathing, consciousness, control of body temp)
- has many tracts that run through it
what key functions does the reticular formation serve and what three brain structures does the reticular formation span
pain, visceral function, posture, sleep/wakefulness
muscle tone, eye movements, behavioural arousal
spans the pons, medulla and midbrain
- the reticular formation has strong connections to multiple areas
what is the basic functional unit and what are the two types of circuits it forms
the neuron
relay circuits (convey information from one spot to another)
reflex circuits (in the spinal cord and allow quick responses)
- stress has an impact on our reflex circuits (reflexes become amplified when stressed)
compare and contrast neurons and supporting cells
neurons are specialized for electrical signalling over distances
supporting cells are not capable of signalling but instead support the function of the neurons (outnumber neurons 3:1)
neurons and glial cells differ in structure, chemistry and function
why is there variability in how neurons are structured
important for different functions, adaptability and efficiency
there is diversity among nerve cells but how are they similar
their basic structure (cell bodies are the same as other cells in the body)
how are cell bodies specialized for communication
overall morphology (different features of cell bodies allowing for specialization)
structural and functional details of synaptic contacts (number of dendrites changes in different neurons)
specialization of membranes for electrical signalling
the number of inputs a neuron receives depends on what
the number of dendrites there are
- wide range of number of dendrites (1-100,000)
what is the fundamental purpose of the nerve cell
to integrate information from other neurons
what do dendrites play a role in and what do they determine
synaptic plasticity (neurons that consistently fire together have stronger connections)
determine when cells fire and the frequency of firing
how many extensions does a unipolar neuron have and what is it an example of
one extension from the cell body
an interneuron
how many extensions does a bipolar neuron have and what is it an example of
two
sensory neuron
what is a multipolar neuron an example of
a motor neuron
what is the purpose of the axon and in what ways do axons vary
integrate information at axon hillock and conduct a signal down the axon
variability in diameter, length, presence of myelin
- myelin and diameter play a role in conduction speed
where does plasticity occur
at the synapse of the axon terminal
changes in the structure or number of receptors in post synaptic terminal changes the response
what are the functions of neuroglial cells and what do they lack compared to neurons
maintain ionic milieu of nerve cells (uptake of K to allow signalling to continue)
modulate rate of signal propagation
control uptake of NTs
provide a foundation for development
aid in recovery from neural injury (eat up dead cell and debris)
lack axons and dendrites
- neuroglial cells are susceptible to cancers
name the types of neuroglial cells in the peripheral NS (2) and central NS (4)
peripheral: satellite cells, Schwann cells
central: oligodendrocytes, astrocytes, microglia, ependymal cells
what are the functions of satellite cells and Schwann cells
satellite: support and regeneration
Schwann: form myelin sheath in the peripheral NS
what are the functions of oligodendrocytes, astrocytes, microglia and ependymal cells
oligodendrocytes: form myelin in the CNS
astrocytes: play a role in the blood brain barrier
microglia: regeneration and recovery by removing debris
ependymal: line fluid filled areas (ventricles and spinal cord) to maintain balance of chemicals in CSF
how can brain injury affect glial cell activity
increases in the number and activity which can be good or bad
overactivity can cause formation of plaques and scars which can prevent signalling from occurring
describe the characteristics of an oligodendrocyte and Schwann cell (location, # of processes, nodes of ranvier distance)
oligodendrocyte: found in the CNS, multiple processes and coils around several axons, widely spaces node of ranvier resulting in faster conduction
Schwann: found in PNS, associated with one nerve only, nodes of ranvier close together resulting in slower conduction
what is MS, what are the symptoms of it, and which areas are most affected
a chronic inflammatory demyelinating disease of the CNS causing nerves to fatigue rapidly
paralysis and intention tremor, scanning speech, nystagmus
optic nerves, periventricular white matter, spinal cord, cerebral peduncles
in MS, the demyelinated areas become filled with what and what does this cause
filled with astrocytes causing proliferation of neuroglial tissue which leads to the development of plaque/scars which hinder/prevent conduction
list the differences in the CNS and PNS with regards to
1. where cell bodies are found
2. how axons travel
3. which cells provide myelination
CNS: (1) in nuclei, (2) travel as tracts, (3) oligodendrocytes
PNS: (1) in ganglia, (2) travel in bundles called nerves, (3) Schwann cells
what is gray matter
what is white matter
regions of the brain and spinal cord that contain nerve cell bodies
myelinated axons
what are neuropils
dendrites and terminal branches of axons surrounding neuron cell bodies
T or F: neurons function in isolation
F, groups of neurons form the foundation for sensation, perception and movement
what do interneurons do
connect afferent and efferent neurons in the spine
modulate response of large circuits
allowing information to travel up to the brain
explain the functional neural circuit (stepping on tack example)
how can descending information change this response
information comes in centrally and synapses on an interneuron which then synapses onto a motor neuron to cause a withdrawal response
initial reaction to stepping on something may cause a reflexive response but descending information can augment that response
give an example of an interruption to a neural circuit and explain how it happens
disc herniation
pressure on the nerve root from bulging disc interrupts signalling causing pain and weakness
