Nervous Tissue Flashcards
Peripheral Glial cells?
- Schwann cells
- Satellite cells
Central Glial cells?
- oligodendrocytes
- astrocytes
- microglial cells
- ependymal cells
Role of interneurons?
fine tune other neurons (sensory, motor)
What is Nissl substance?
- large granules of rough ER with ribosomes for protein synthesis
- indicate neuron is active
Axon hillock?
- where action potential generates
- light stained area of neuron
- only one axon per neuron
Dendrites?
- vary greatly
- up to 200,000 per neuron
- become thinner with branching
- cytoplasm similar to perinuclear cytoplasm except golgi apparatus
Role of myelin?
- insulate axons
- cover ion channels to prevent from opening
- conducts faster signal
Nodes of Ranvier function?
- saltatory conduction
- signal jumps from node to node
- faster signal
What are the fastest axons in terms of diameter and myelination?
larger diameter and myelinated
Multiple sclerosis?
- demyelinating disease
- autoimmune
- BBB is compromised allowing WBCs to enter brain and attack proteins (MBP, PLP) that produce myelin in CNS
Guillain barre syndrome?
- demyelinating disease
- autoimmune
- immune system attacks myelin sheath in PNS
- paralyzed in severe cases
- starts with tingling and muscle weakness of extremities
Charcot marie tooth disease?
- inherited neuro disease
- mutation of protein in peripheral axons or myelin
- starts in lower leg
Progressive multifocal leucoencephalopathy?
-viral infection causes demyelination
Bipolar neurons?
- special senses
- vision, hearing, smell
Multipolar neurons?
- motor neurons
- interneurons (most neurons in body)
Pseudounipolar neurons?
- sensory neurons in ganglia
- DRG, cranial nerve ganglia
What is the resting membrane potential?
- 70mV
- K is high inside cells, Na high outside
What is the threshold potential?
- 55mV
- neurons are polarized to generate action potential
Steps to generation of action potential?
- Depolarization- Na channels open, influx of Na into cell, if reach threshold (-55mV) an action potential is generated, can reach +30mV
- Na channels shut at peak, K channels open
- Depolarization- K channels open, diffuse out of cell to bring the membrane potential back down
- Hyperpolarization- K continues to diffuse, cannot receive another stimulus (-90mV)
- ATPase pump actively transports Na back out and K back in (3 Na, 2 K) which restores the resting potential
Types of synapses?
- Axosomatic: axon on cell body
- Axodendritic: axon on dendrite
- Axoaxonic: axon on axon
- Dendrodendritic: dendrite on dendrite, new finding
Difference between electrical and chemical synapse?
- Electrical
- ion channels, gap junctions
- faster conduction
- bidirectional
- no cleft
- not common - Chemical
- more common
- have gain: one motor axon terminal can excite more than on skeletal muscle
- neurotransmitters in synaptic vesicles, released into cleft and bind to receptors on postsynaptic membrane
Process of chemical synapse?
- action potential arrives, releases calcium into presynaptic axon
- triggers release of ACh from vesicles
- receptors on postsynaptic membrane align to bind with ACh
- can be excitatory or inhibitory to depolarize or hyperpolarize the cell - Neurotransmitter is reuptaked into presynaptic neuron or degraded my enzymes in the cleft
Amino acid NTs?
- Glutamate
- Glycine
- GABA
Monoamine NTs?
- NE
- Epi
- Dopamine
- Serotonin
Acetylcholine?
- NT in all preganglionic neurons
- in parasympathetic postganglionic neurons
- neuromuscular junction
- sweat glands
Norepinephrine?
-most sympathetic postganglionic neurons exept sweat glands (ACh) and renal artery (dopamine)
Epinephrine?
-Adrenal medulla releases into blood (small amount of NE as well)
Are of spinal cord for sympathetic? parasympathetic?
- Sympathetic: IML (T1-L2)
- Parasympathetic: craniosacral (cranial nerves, S2-S4), ganglions near effector organs
Cholinergic receptors?
- Muscarinic: at target organs of parasympathetic innervation
- Nicotinic: autonomic ganglia, adrenal medulla, NMJ
Adrenergic receptors?
- alpha:
- alpha 1- vascular smooth muscle and sphincters
- alpha 2- nerve endings - Beta:
- beta 1- heart
- beta 2- vascular and nonvascular smooth muscle (selective or nonselective)
NT and receptors in parasympathetic innervation?
- preganglionic neuron is long, releases ACh at Nicotinic receptor
- postganglionic neuron is short to effector organ
- Muscarinic receptor, releases ACh
NT and receptors in sympathetic innervation to sweat glands?
- preganglionic neuron is short, release ACh at nicotinic receptor
- postganglionic neuron is long
- releases ACh at Muscarinic receptor in sweat glands
- Cholinergic drug causes sweating
NT and receptors in sympathetic innervation of cardiac and smooth muscle, gland cells, and nerve terminals?
- preganglionic neuron is short, releases ACh at Nicotinic receptor
- postganglionic neuron is long, releases NE at alpha or beta receptors
NT and receptors in sympathetic innervation of renal vascular smooth muscle?
- preganglionic neuron is short, releases ACh at Nicotinic receptors
- Postganglionic neuron is long, releases Dopamine at D1 receptors in kidney smooth muscle
NT and receptors in adrenal medulla?
- Neuron stimulates adrenal medulla with ACh at Nicotinic receptors
- Adrenal medulla releases 20% NE and 80% Epi
NT and receptors in somatic skeletal muscle?
- one motor nerve extends from spinal cord to skeletal muscle
- Releases ACh at Nicotinic receptors at effector muscle
Botulism (tetanus)?
interrupts presynaptic release of ACh
Lambert Eaton syndrome?
- interrupts presynaptic release of ACh
- disrupts voltage gated calcium channels
Myasthenia Gravis?
- block the postsynaptic receptors
- produce antibodies against Nicotinic receptors
- prevents ACh from binding to receptors
- fluctuating muscle weakness in eyes and face
Organophosphates insecticides and nerve gas?
- too much acetylcholine depolarize the postsynaptic receptors
- inactivate acetylcholinesterase so cannot breakdown ACh in cleft
- muscle tremor and death, paralysis
- cholinergic drugs same mechanism
White matter in CNS?
- inside area of brain, outside of spinal cord
- axons
- glial cells
- no cell bodies
Gray matter in CNS?
- outside of brain, inside of spinal cord
- cell bodies
- Neuropil (dendrites, axons, glial processes)
- glial cells
Cerebral cortex layers?
- Molecular layer
- External granular layer
- External pyramidal layer
- (1-3 inter hemispheric connection) - Internal Granule layer (afferent)
- Internal Pyramidal layer (afferent to basal ganglia)
- Multiform (fusiform) layer (efferent)
- White matter
Cerebellar cortex layers?
- Outer Molecular layer- barely any cell bodies
- Central Purkinje layer- big cells, protect dendritic tree
- Inner Granular layer- compact, small neurons, project axons to molecular layer
Astrocytes in CNS?
- fibrous and protoplasmic: glial fibrillary acidic protein
- maintain blood brain barrier
- move metabolites to and from neurons
- modulate neuronal survival and activity
Oligodendrocytes in CNS?
- produce myelin in CNS
- one oligodendrocyte can produce myelin for one to several neurons
Microglia in CNS?
- phagocytic cells
- when activated, retract processes and appear like macrophages
- involved in inflammation and repair, immune cell in brain
Ependymal cells in CNS?
- epithelium like cells lining ventricles of brain and central canal of spinal cord
- cilia and microvilli on apical surfaces
- Choroid plexus: produce CSF
- each ventricle has one plexus (4 total)
- capillaries are leaky to allow plasma to leak out and filter plasma
- tight junctions between cells
- no external basal lamina
CSF production and flow?
- CSF is produced in choroid plexus lining the 4 ventricles
- Flows from the 4th ventricle to subarachnoid space through median and lateral apertures
- small amount flows into central canal of spinal cord
- CSF can be reabsorbed by microvilli
Blood brain barrier anatomy?
- tight junctions of endothelial cells
- lack of fenestration
- basement membrane
- astrocyte end feet
- pericytes
Blood brain barrier function?
- filter and restrict passage of certain molecules (>500 daltons)
- maintain water and ion levels in CNS
- blood born immune cells cannot penetrate
Diseases involving blood brain barrier?
- Meningitis
- HIV encephalitis
- Rabies
- Alzheimers (late stage)
Nerve coatings?
- Epineurium: outer layer encloses several bundles of fascicles
- Perineurium: encloses fascicles
- Endoneurium: encloses individual axons
Peripheral glial cells?
- Schwann cells
- Satellite cells
Schwann cells?
- support myelinated and unmyelinated axons
- produce myelin to speed up conduction of nerve impulses
- clean up debris and guide regeneration
Satellite cells?
- electric insulation
- metabolic exchange
