Final- NS fundamentals Flashcards
Sensory (afferent)
- Transmits impulses from sensory receptors toward CNS
- Somatic-impulses from skin, skeletal muscles (conscious)
- Visceral-impulses from visceral organs toward CNS (unconscious)
Motor (efferent)
- transmits impulses away from CNS to effector organs
- somatic-impulses from CNS to skeletal muscles (conscious)
- autonomic-impulses from CNS to smooth muscle, cardiac muscle and glands (unconscious)
Difference between nuclei and ganglia
Nuclei-cluster of cell bodies in the CNS
Ganglia-cluster of cell bodies in the PNS
Anterograde transport
- moves substances away from cell body
- ex: neurotransmitters
Retrograde transport
- moves substances towards cell bodies
- ex: vesicles, NT recycling
What is MS made of and what is its purpose
- made of lipids from Schwann cells (PNS) and oligodendrocytes (CNS)
- purpose is the insulate axons and make AP faster
Depolarization
Makes the cell membrane more positive
Hyper polarization
Making the cell slightly more positive back to the RMP which is -55
Repolarization
Makes the cell negative down to -70
How do action potentials self propagate
Positive Na+ ions at origin activate neighboring VG Na+ channels
Saltatory conduction
Only generated at Nodes of Ranvier
Diffusion of Na+ ions under myelinated nerve segments cause a fast propagation of the AP stimulus in those regions
How can AP be blocked
- Novacain
- cold and pressure
Chemical synapse characteristics
- release and receptor of chemical NT
- slower than electrical
Electrical synapse
- least common
- neurons joined by gap junctions
- fast communication
- allow synchronization of interconnected neurons
Steps of chemical synapse transmission
- AP arrives at axon terminal
- VC Ca channels open, Ca rushes in
- Ca entry causes synaptic vesicles to release NT by exocytosis
- NT binds receptor on post synaptic neuron
- NT fate
- stays in synapse
- taken up by transport proteins
- enzymatically degraded
- diffused away from synapse
EPSP
Brings the membrane close to the AP potential
IPSP
Brings the neuron away from the AP threshold
Opens K+ or Cl- channels
Temporal summation
One stimulus pushing the AP to its threshold
Spatial summation
Multiple stimuli pushing the AP to its threshold
ACh
- stimulates muscle to contract
- important in CNS for learning and memory
- develop Alzheimer’s if you have low levels
Serotonin
- inhibitory in CNS
- Calms anxiety, relieves depression, helps us sleep
- low levels means you’ll have anxiety and depression
Histamine
Involved in learning and memory
Stimulates wakefulness
Antihistamines-makes you sleepy
Dopamine
- stimulates pleasure centers
- stimulates attention, focus, motivation and drive
- elevated dopamine levels means you could have schizophrenia
- low levels of dopamine means you could have Parkinson’s
Norepinephrine
- ANS
- acts on cardiac, smooth muscle and glands
- increases heart rate, blood pressure and dilated pupils
- increases arousal and attention
GABA
- inhibitory NT
- reduces anxiety and stress
Endorphins
- block transmission of pain
- increases pleasure sensations
Enkaphalins
-released in pregnant women during labor
Astrocytes
- most abundant
- attach neurons to capillaries
- guide formation of synapses
- control chemical environment around neurons
Micro glial cells
- monitor health of neurons
- phagocytose invading microorganisms or dead/dying cells
Difference between CNS and PNS
CNS-Brain and spinal cord
PNS-All the neural structures outside the brain and spinal cord
