MEC322: Nervous System Flashcards
Which of the 11 body systems play the most important roles in maintaining homeostasis?
nervous system and endocrine system
What are the three basic functions of the nervous system?
detecting stimuli (sensory function); analyzing, integrating, and storing sensory information (integrative function); responding to integrative decisions (motor function).
What does CNS stand for?
Central nervous system
What does PNS stand for?
Peripheral nervous system
What is part of the CNS?
Brain
Spinal cord
What is part of the PNS?
Cranial nerves Spinal nerves Ganglia Enteric plexuses in small intestine Sensory receptors in skin
What are the two divisions of the peripheral nervous system?
Afferent- brings sensory info to CS
Efferent- carries motor commands from CNS to muscles glands etc
What are the subdivisions in the efferent division?
Somatic nervous system SNS
Automatic nervous system ANS
What does the SNS provide?
voluntary control over skeletal muscles
What does the ANS provide?
involuntary control of cardia and smooth muscle, and glands
What is a neuron cell?
cells specialised for nerve impulse conduction and provide most of the unique functions of the nervous system
e.g. sensing, thinking remembering, controlling muscle activity
What is a neuroglia cell?
they support, nourish and protect the neurons and maintain homeostasis in the interstitial fluid that bathes neurons
What are the three parts of a neuron?
Dendrites
Cell body
Single axon
What is the dendrite in a neuron?
main receiving or input region
What is the cell body in a neuron?
integration occurs here
What is the axon in a neuron?
output part
conducts nerve impulses towards another neuron, muscle fibre or gland cell
Structurally what are the three classifications of neuron?
multipolar, –|–o <
bipolar, -|-o– <
unipolar –o-|-
How are neurons classified functionally?
Sensory neurons
Motor neurons
Interneurons
What do sensory neurons do?
carry sensory info into the CNS
approx 10^6
What do motor neurons do?
carry info out of CNS to effectors (muscles and glands)
approx 500000
What do interneurons do?
located within the CNS between sensory and motor neurons
approx 20^9
How much of the CNS do the neuroglia make up?
half the volume of the CNS
What are the neuroglia in the CNS?
astrocytes, oligodendrocytes, microglia, and ependymal cells
What are the neuroglia in the PNS?
Schwann cells and satellite cells
What are myelin sheaths?
sleeves of fatty tissue that protect your nerve cells
Which two types of neuroglia produce myelin sheaths?
Oligodendrocytes myelinate axons in the CNS, and Schwann cells myelinate axons in the PNS.
What do astrocytes do?
Neuroglia cells in CNS
- Control the chemical environment of the brain
- Brace neurons and form barrier against capillaries
- Abundant, star-shaped cells
What do microglia do?
Neuroglia cells in CNS
- Spiderlike phagocytes
- Dispose of debris
What do ependymal cells do?
Neuroglia cells in CNS
- Line cavities of the brain and spinal cord
- Cilia assist with circulation of cerebrospinal fluid
What do oligodendrocytes do?
Neuroglia cells in CNS
- Wrap around nerve fibers in the central nervous system
- Produce myelin sheaths
What do Satellite cells do?
Neuroglia cells in PNS
Protect neuron cell bodies
What do Schwann cells do?
Neuroglia cells in PNS
Form myelin sheath in the peripheral nervous system
How to neurons communicate with one another?
nerve action potential AKA nerve impulses
What does generation of action potentials depend on?
the existence of a membrane potential and the presence of voltage-gated channels for Na+ and K+.
What is the resting membrane potential?
RMP= -70mV
inside of the neuron is 70 mV less than the outside
What causes the RMP?
an unequal distribution of ions on either side of the plasma membrane and a higher membrane permeability to K+ than to Na+. The level of K+ is higher inside and the level of Na+ is higher outside, a situation that is maintained by sodium–potassium pumps.
What happens during an action potential?
- voltage-gated Na+ and K+ channels open in sequence
- results in depolarisation ( the loss and then reversal of membrane polarisation)
- opening of voltage-gated k+ allows depolarisation and recovery of the membrane potential
What is the all-or-none principal?
if a stimulus is strong enough to generate an action potential, the impulse generated is of a constant size
Can another action potential be generated during the refractory period?
NO
What is nerve impulse conduction that occurs as a step-by-step process along an unmyelinated axon called?
continuous conduction
What is saltatory conduction?
a nerve impulse “leaps” from one node of Ranvier to the next along a myelinated axon.
What conducts impulses faster, large diameter axon or small diameter?
large
What conducts impulses faster, myelinated axons or unmyelinated axons ?
myelinated axons
What is a node of Ranvier?
a gap in the myelin sheath of a nerve, between adjacent Schwann cells.
How do neurons communicate with other neurons and effectors?
at synapses in a series of events known as synaptic transmission
What are the two types of synapses?
electrical and chemical
Describe an electrical synapse
nerve impulses are conducted between adjacent neurons via gap junctions.
This type of synapse is found in visceral smooth muscle, cardiac muscle and the brain.
Describe a chemical synapse
the presynaptic neurons release neurotransmitters which will bind to receptors on the plasma membrane of the postsynaptic neuron.
At a chemical synapse, there is only one-way nerve impulse conduction.
What does the excitatory neurotransmitter do?
depolarizes the postsynaptic neuron’s membrane, brings the membrane potential closer to threshold, and increases the chance that one or more action potentials will arise.
What does the inhibitory neurotransmitter do?
hyperpolarizes the membrane of the postsynaptic neuron, thereby inhibiting action potential generation.
What are the three ways a neurotransmitter can be removed?
diffusion, enzymatic destruction, and reuptake by neurons or neuroglia.
List some important neurotransmitters
acetylcholine, glutamate, aspartate, gamma aminobutyric acid (GABA), glycine, norepinephrine, dopamine, serotonin, neuropeptides, and nitric oxide.
What happens when we want to move?
, electrical signals cascade from the brain down the spinal cord to instruct our muscle to contract
