nervous system Flashcards
neuron
functional unit of nervous system
neuron structure
consists of several dendrites, single branches axon, and cell body (soma)
- highly specialized
- cannot divide
- dependent on glucose
sensory (afferent)
receive initial stimulus from environment
association (interneuron)
receive input from sensory and sent to motor neurons -make up 99% of body’s neurons
motor (efferent)
from brain, stimulate target cells (effectors) to elicit response
dendrites
receive information to transfer to cell body
axon hillock
site of action potential gradient
axon
transfer impulses away from body
glial cells
capable of dividing
consist of:
1. oligodendrocytes
2. schwann cells
3. microgalia
4. ependymal cells
5. satellite cells
6. astrocytes
oligodendrocytes
produce myelin in the CNS
schwann cells
produce myelin in the PNS
microglia
CNS phagocytes
ependymal cells
circulate cerebrospinal fluid with cilia
satellite cells
support cells in PNS
astrocytes
physically support CNS neurons; maintain nutrient and mineral balance
myelin sheath
act as insulators
separated by Nodes of Ranvier
only vertebrates have myelinated axons
peripheral nervous system (PNS)
utilizes preganglionic and postganglionic axons, various neurotransmitters, and different receptors to act on the effector organs
somatic nervous system
- innervates skeletal muscle
- voluntary or involuntary movements
- uses ACH at neuromuscular junctions (synapse between motor neuron and skeletal muscle cell)
autonomic nervous system
sensory impulses from blood vessels, heart, chest organs, abdomen
sympathetic branch
- fight or flight
- increased blood pressure and heart rate, generation of energy
- inhibition of digestion, urination, and salivary secretion
parasympathetic branch
- rest and digest
- lowered heart rate
- increased digestion, relaxation, and sexual arousal
central nervous system
- contains brain, spinal cord, and interneurons
- the blood-brain barrier is a blockade of cells that prevents or slows the passage of drugs, ions, and pathogens into the CNS –> permeable to O2, CO2, glucose, and small non-polar molecules
Olfactory bulb (forebrain)
smell
thalamus
relay between spinal cord and cerebral cortex
hypothalamus
visceral functions
sleep, hunger, temperature regulation
basal ganglia
planning/learning
hippocampus
memory
Limbic system
hippocampus, amygdala, and hypothalamus
behavioral and emotional responses
diencephalon subdivision
thalamus, hypothalamus, pineal gland
pineal gland
regulates melatonin and circadium rhythm
cerebrum
contains cerebral cortex
- frontal lobe - attention
- parietal lobe - sensory
- temporal lobe - sound processing/interpretation
- occipital lobe - visual
midbrain
relay center for visual/auditory impulses
motor control
cerebellum
balance and coordination
brainstem
connects cerebrum to spinal cord
pons relay center (cortex + cerebellum)
medulla oblongata
medulla oblongata
controls heart rate and breathing
resting potential
-70mV with K+ higher inside the cell; Na+ higher outside
depolarization
- ion channel opens
- Na enters and depolarizes axon
- if the -50mV threshold is reached, an action potential will send Na+ down entire neuron
- inside becomes more positive
repolarization
- going back to resting potential
- ion channel open, K+ moves out, making inside more negative
hyperpolarization
- too much K+ is released
- membrane potential becomes even more negative than resting
refractory period
neuron unresponsive to new stimulus until the Na+/K+ pump returns ions to resting potential locations
Na+/K+ pump
- maintains resting potential of -70mV using ATP
- 3 Na+ out for every 2 K+ in
absolute refractory period
no additional stimuli can cause a result
relative refactory period
responds if stimulus is large enough
chemoreceptors
for taste, smell, blood chemistry
transmission across a synapse
- action potential reaches synaptic region
- activates voltage-gated channels for calcium to enter
- presynaptic neuron releases neurotransmitters from synaptic vessels to synaptic cleft
- NTs will bind to receptors on the postsynaptic neuron
- postsynaptic membrane is either excited or inhibited according to which NT binds
acetylcholine (ACh)
- binds to ACh receptors on post-synaptic membrane for nerve transmission
- secretion at neuromuscular junctions = contraction or relaxation of muscle (PNS)
- recycled back to presynaptic vesicle via acetylcholinesterase –> nerve signal terminated; postsynaptic neuron cannot depolarize
glutamate
most common CNS neurotransmitter in vertebrates; excitatory
GABA
found in brain; inhibitory
glycine
found in CNS outside brain; inhibitory
epinephrine and norepinephrine
act in sympathetic nervous system
bronchodilation and vasodilation to lungs and skeletal muscles
vasoconstriction to the digestive system and kidneys
if a nerve cell is stimulated below its threshold potential, what would happen
an action potential would NOT occur
