Nervous System Flashcards
2 types of cells in nervous system
glia and neurons
4 types of CNS glia
astrocytes, microglia, ependymal cells, oligodendrocytes
function of astrocytes
- supply nutrients to neurons
- ensheath blood capillaries
- transmit information
function of microglia
- immune cells of CNS
- engulf microorganisms and debris
function of ependymal cells
- line fluid-filled spaces of brain and spinal cord
- have cilia to circulate CSF
function of oligodendrocytes
- support nerve fibres
- ensheath them with myelin
only type of PNS glia and function
- schwann cell - support peripheral nerve fibres - ensheath them with myelin
myelin sheath composition and function
- lipid wrapped around neuron - increases conduction velocity
input zone of neuron
- dendrites - receives chemical signal from other neurons
summation zone of neuron
- axon hillock - makes decision about whether to pass information on
conduction zone of neuron
- axon - carry electrical signals between brain areas, to and from spinal cord, or to and from peripheral sensory receptors
output zone of neuron
- axon terminals - contact with input zone of other neurons - release neurotransmitter
3 types of synapse
1) axodendritic 2) axosomatic 3) axoaxonic
multiple sclerosis cause and symptoms
- demyelination caused by autoimmunity or infection
- impaired nerve conduction
- weakness, uncoordination, visual and speech impairment
afferent
- information that goes into the brain (up spinal cord) - sensory
efferent
- information that comes out of brain (down spinal cord) - motor
nucleus
group of cell bodies in CNS
tract
bundle of axons in CNS
Grey matter
group of cell bodies in cerebral cortex
white matter
bundle of axons in cerebral cortex
ganglion
group of cell bodies in PNS
nerve
bundle of axons in PNS
somatic information
- stuff we are aware of and have control over
- voluntary muscle control (somatic efferent)
- sensory information we are aware of (somatic afferent e.g. vision)
Autonomic information
- stuff we are not aware of and have no control over
- involuntary muscle control (autonomic efferent e.g. heartbeat)
- sensory (visceral) information we don’t know about (autonomic afferent e.g. blood pressure)
6 features of somatic motor (efferent) pathway
- voluntary control - one neuron between CNS and effector - cell body in spinal cord - axon in spinal nerves (PNS) - neurotransmitter is ACh - effectors are skeletal muscle fibres always excitatory (EPSPs caused by ACh at NMJ)
motor unit
- one neuron and all the muscle fibres it innervates - one neuron => one muscle fibre or one neuron => several muscle fibres
5 features of autonomic motor (efferent) pathway
- involuntary control
- two neurons between CNS and effector (neuron 1 has cell body in CNS and axon in PNS, myelinated; neuron 2 has cell body and axon in PNS, unmyelinated)
- neurotransmitter at first synapse is ACh, 2nd is ACh or NE
- effectors are smooth muscle, cardiac muscle, glands, adipose tissue
- excitatory or inhibitory (EPSPs or IPSPs)
features of neuron 1 of autonomic motor pathway
- cell body in CNS
- axon extends outside CNS
- synapse in autonomic ganglion
- pre-ganglionic neuron
- neurotransmitter = ACh
- myelinated
features of neuron 2 of autonomic motor pathway
- cell body in PNS, autonomic ganglion
- axon extends to effector organ
- synapse in effector organ
- post-ganglionic neuron
- neurotransmitter = ACh or noradrenaline (norepinephrine)
- unmyelinated
subdivisions of autonomic nervous system
sympathetic and parasympathetic
5 features of sympathetic nervous system
- ACh at 1st synapse (cholinergic)
- NE at 2nd synapse (adrenergic)
- short pre-ganglionic neuron, long post-ganglionic neuron
- ganglia in sympathetic chain
- excitatory (EPSPs)
4 features of parasympathetic nervous system
- ACh at both synapses
- long pre-ganglionic neuron, very short post-ganglionic neuron
- ganglia in/near effector
- inhibitory (IPSPs)
ventral root
efferent (motor) information out of spinal cord
dorsal root
afferent (sensory) information into spinal cord and travels up
dorsal column
sensory info travels up spinal cord
ventral column
motor info travels down spinal cord
lateral column
info travels in both directions
external anatomy of spinal cord
- starts at foramen magnum (base of skull) - ends at 1st lumbar vertebrae - end is tapered cone called conus medularis - Filum terminale extends from conus medularis to end of spinal cavity - anchors spinal cord - within meningeal sack in spinal cavity within vertebrae
where does somatic motor info come out of spinal cord
in ventral horns of spinal cord
where does autonomic motor info come out of spinal cord
in lateral/ventrolateral horns of spinal cord
where are cell bodies of sensory neurons
in dorsal root ganglion
ventral ramus
communicates with sympathetic chain via two sympathetic rami
structure of peripheral nerve
1) axons - myelinated or unmyelinated 2) axons covered with endoneurium 3) Endoneurium-covered axons (nerve fibers) are bundled together to form a fascicle 4) Fascicles are covered with perineurium 5) Fascicles bundle with each other and with blood vessels to form a nerve 6) Nerves are covered by epineurium
Electrical information is transmitted by
Action potential (along the axon/conduction zone)
Chemical information is transmitted by
Neurotransmitter (released at terminals onto input zone of another neuron)
3 morphological types of neurons
1) multipolar; 2) bipolar; 3) unipolar
Synapse (2 features)
1) Place where two neurons communicate; 2) site of neurotransmitter (chemical signal) release
Pre-synaptic cell
Releases neurotransmitter from its output zone (sends signal)
Post-synaptic cell
Receives neurotransmitter signal at its input zone
Axo-dendritic synapse
Axon of pre-synaptic cell releases neurotransmitter from its output zone onto dendrite of post-synaptic cell - most common in CNS
Axo-somatic synapse
Axon of pre-synaptic cell releases neurotransmitter from its output zone onto cell body (also called soma) of post-synaptic cell
Axo-axonic
Axon of pre-synaptic cell releases neurotransmitter from its output zone onto axon terminal of post-synaptic cell
where do sympathetic pre-ganglionic neurons come from
thoracolumbar region of spinal cord (i.e. middle)
where do para-sympathetic pre-ganglionic neurons come from
craniosacral regions of spinal cord (i.e. top and bottom)
effects of sympathetic nervous system
- fight or flight - increased heart rate - constricted blood vessels to skin to increased blood flow to muscles - decreased gastric motility - decreased salivation - increased pupil size - increased sweating
effects of parasympathetic nervous system
- rest and digest - decreased heart rate - increased gastric motility - decreased pupil size - increased salivation
receptor at second synapse in sympathetic and parasympathetic nervous system
Sympathetic
- alpha- and beta-adrenergic (excitatory - depolarising)
Parasympathetic
- muscarinic cholinergic (excitatory or inhibitory - depolarising or hyperpolarising)
Receptor at first synapse in sympathetic and parasympathetic nervous system
- ionotropic so receptors contain an ion channel and it uses flow of ions to depolarise cell
- nicotinic cholinergic
- depolarising and excitatory
activation of adrenal gland
- innervated by preganglionic neuron (ACh)
- no postganglionic neuron
- can be considered specialised sympathetic ganglion
- releases adrenaline and NE into bloodstream as hormones
