L10: Nervous System I

What is CNS made of?

Brain and spinal cord

What is PNS made of?

nerves and ganglia

What are ganglia?

Collections of neuron cell bodies in PNS

What are nerves?

Bundles of axons that carry info to and from the CNS

Afferent?

To CNS

Efferent?

Away from the CNS

What are lower centers?

Spinal cord and brainstem—control basic and essential functions

What are centers?

A functional region of CNS that helps coordinate an activity

What are higher centers?

Located mainly in cerebrum and cerebellum

What are the 2 divisions of PNS?

1. Somatic= voluntary

2. Autonomic= involuntary

What protects the spinal cord?

Vertebral column, meninges, CSF, and epidural fat

What are meninges?

3 connective tissue membranes that surround and protect brain and spinal cord

What are the 3 layers that form meninges (superficial to deep)?

1. Dura mater

2. Arachnid

3. Pia mater

   

How many pairs of spinal NERVES?

31

What is the division for spinal NERVES?

• 8 cervical

• 12 thoracic

• 5 lumbar

• 5 sacral

• 1 coccygeal

What are spinal enlargements?

Regions spinal cord is wider because they have increased # of neurons

Where are spinal enlargements?

Cervical and lumbar regions

What is cauda equina (horse’s tail)?

Bundle of lumbar, sacral, and coccygeal spinal nerves extending inferiorly from conus medullaris

What is the conus medullaris?

Tapered inferior end of spinal cord, usually around L1-L2 vertebral level

What is filum terminale?

Thin strand of pia mater extending inferiorly from conus medullaris

What is the fuction of filum terminale?

Helps anchor spinal cord

What are glial cells?

Non-neural support cells

What are 2 PNS glial cells?

1. Satellite cells

2. Schwann cells

Satellite cell functions?

• Surrounds neuron cells bodies in PNS ganglia

• Provides structural and metabolic support

• Regulates chemical environment

What do Schwann cells do?

Form myelin sheaths around nerve fibers

What are the 4 CNS glial cells?

1. Microglia

2. Ependymal cells

3. Oligodendrocytes

4. Astrocytes

What do microglia cells do?

Immune cells of CNS; they remove pathogens, damaged cells, debris through phagocytosis

What do ependymal cells do?

Lines brain ventricles and central canal of spinal cord; the cilia helps circulate CSF

What do astrocyte cells do?

• Regulate EC chemical environment

• Metabolic support to neurons

• Regulates synaptic activity

• Helps form blood-brain barrier

What do oligodendrocytes do?

They form myelin sheaths around nerve fibers

What are dendrites?

They receive signals from other cells and carry them towards cell body

What are cell bodies (somas)?

The metabolic and integrative center of neuron

What are axons?

They carry action potentials away from the cell body

What are nerve endings?

Send signals to other cells

What are the four neuron types (by structure)?

1. Multipolar

2. Psuedounipolar

3. Anaoxonic

4. Bipolar

What is the structure of a multipolar neuron?

One axon and many dendrites

What is the most common type of neuron?

Multipolar

How do multipolar neurons function?

Usually function as motor neurons (they are walking! so cute)

What is the structure of a psuedounipolar neuron?

Single process extends from cell body and bifurcates into peripheral and central branch

How do psuedounipolar neurons function?

Dorsal root ganglia—usually just general sensory neurons

What is the structure of an anaxonic neuron?

Many dendrites and no obvious axon

How do anaxonic neurons function?

Local interneurons—communicates strictly with nearby cells

What is the structure of a bipolar neuron?

One dendrite and one axon

What is the function of bipolar neurons?

Special sensory pathways—retina, inner ear, olfactory

What is a synapse?

Junction where a neuron communicates with another cell—neurotransmitters carry singal across small gap at synpase

What are the 3 parts of the synapse

1. Presynaptic axon terminal

2. Synaptic cleft

3. Postsynaptic membrane

What happens in the presynaptic axon terminal?

Synaptic vesicles are filled with neurotransmitters

What happens in the synaptic cleft?

Gap where neurotransmitter diffuses

What happens in the postsynaptic membrane?

Receptors bind neurotransmitter and produce a response

What is dopamine responsible for?

Movement, motivation, and reward-learning

What is serotonin responsible for?

Mood, sleep, appetite, and GI activity

What is norepinephrine responsible for?

Wakefulness and arousal in CNS

What is acetylcholine responsible for?

Skeletal muscle contraction, autonomic signaling, and attention/learning/memory

What neurotransmitters are monoamines (4)?

• Dopamine

• serotonin

• norepinephrine

• histamine

What neurotransmitters are amino acids (3)?

• Glutamate

• GABA

• Glycine

What is glutamate responsible for?

Major excitatory neurotransmitter—excite neurons to help action potentials

What is GABA responsible for?

Major inhibitory neurotransmitter—prevent over excitation of neurons

What is glycine responsible for?

Inhibitory neurotransmitter in spinal cord and brainstem

What neurotransmitter loss is associated with Alzheimer’s?

Acetylcholine

What neurotransmitter loss is associated with Parkinson’s?

Dopamine

What neurotransmitters are neuropeptides (3)?

• Endorphins

• Substance P

• Oxytocin

What are endorphins responsible for?

Pain modulation

What is substance P responsible for?

Pain signaling

What is oxytocin responsible for?

Childbirth, breastfeeding, social bonding, sexual arousal

What neurotransmitters are purines (2)?

• ATP

• Adenosine

What is ATP responsible for?

Acts as neurotransmitter

What is adenosine responsible for?

Decreases neural activity and promotes sleepiness

How is caffeine effective?

By blocking adenosine receptors

What is glycine important for?

Processing motor and sensory info

What is glutamate important for?

Synaptic plasticity, learning, and memory.

What is the point of the biosynthesis of catecholamine?

The enzymatic pathway that converts Tyrosine (amino acid) into important neurotransmitters

What is the biosynthesis of catecholamine?

Tyrosine —> Dopa —> Dopamine —> Norepinephrine —> Epinephrine

What are the two enzymes involved in catecholamine metabolism?

1. Catechol-O-methyltransferase

2. Monoamine oxidase

Where does action potential arrive?

Axon terminal

What enters axon terminal after potential arrives?

Voltage-gated calcium channels open and calcium enters axon terminal

What does calcium trigger?

Synaptic vesicles to fuse with presynaptic membrane and release neurotransmitter by exocytosis

Where do neurotransmitters diffuse?

Across synaptic cleft and binds to receptors on postsynaptic membrane

What is synaptic strength?

How effectively activity in one neuron produces a response in another neuron

What can increase synaptic strength?

Recent activity

What causes temporary info retention?

Recent activity