Nervous System Study Guide Flashcards
What are the two primary divisions of the nervous system?
The Central Nervous System (CNS) and the Peripheral Nervous System (PNS)
What primary areas do the two main divisions of the nervous system cover?
The CNS is the brain and spinal cord, the PNS is all other neural tissue
What are the further divisions of the PNS?
The PNS is divided into the Afferent and Efferent groups. The Efferent group is divided into the Somatic and Autonomic systems. The Autonomic system is divided into the Sympathetic and Parasympathetic systems.
What two categories is the PNS divided into?
The Afferent (sensory) and Efferent (effector) groups
What is the efferent division of the PNS divided into?
The somatic (voluntary) and autonomic (involuntary) divisions
What is the autonomic division of the PNS divided into?
It’s divided into the sympathetic (stimulating) and parasympathetic (calming) systems
What are the basic functions of the CNS?
To processes and coordinate
What are the functions of the CNS in-depth?
To process and coordinate: sensory data from inside and outside the body, motor commands that control activities of peripheral organs, and higher functions of the brain (like intelligence, memory, learning, and emotion)
What are the functions of the PNS?
To deliver sensory info to the CNS, and carry motor commands to the peripheral tissue systems
What does the afferent division of the PNS do?
It carries sensory info from the PNS sensory receptors to the CNS receptors
What does the efferent division of the PNS do?
It carries motor commands from the CNS, to the PNS, and then to the effectors (muscles and glands)
What is the function of the somatic nervous system (SNS)?
It controls skeletal muscle/ voluntary muscle contractions
What is the function of the automatic nervous system (ANS)?
It controls subconscious contractions/ contractions of smooth and cardiac muscle
What does the sympathetic division of the ANS do?
It has a stimulating effect
What does the parasympathetic division of the ANS do?
It has a relaxing effect
What are the two different cell types in the nervous system and their general functions?
Neurons and neuroglia. Neurons send and receive signals, and neuroglia support and protect the neurons.
What are the major organelles of a neuron cell (or lack thereof)
They have a nucleus, nucleolus, cytoplasm, mitochondria, RER, ribosomes (nissl bodies), cytoskeleton. No centrioles.
What is the size of the axon? What is its function?
It’s long and carries electrical signals (action potentials) to the target
Describe the axon hillock
It’s a thick section of the cell body and it attaches to the initial segment
What are the collaterals?
The branches of a single axon
What are the axon terminals?
Also called the synaptic terminals, they’re the tips of the axon
Describe bipolar neurons
They’re small, they have one dendrite and one axon, and they lead to the special sensory organs (sight, smell, etc)
Describe unipolar neurons
They’re very long axons, they’re fused to dendrites and an axon, the cell body is on one side, and they’re found in sensory neurons in the PNS
Describe multipolar neurons
They have very long axons, they have multiple dendrites and one axon, they’re common in the CNS, and they include all skeletal muscle motor neurons
Define synapse
The area where a neuron communicates with another cell
Define presynaptic cell
The neuron that sends the signal
Define postsynaptic cell
The cell that receives the signal
How does a synapse work?
Neurotransmitters are released at the presynaptic membrane into the synaptic cleft, and they affect receptors of the postsynaptic membrane
What are the types of neuroglial cells in the CNS?
Ependymal cells, astrocytes, microglia, and oligodendrocytes
What are the types of neuroglial cells in the PNS?
Satellite cells and Schwann cells
Where are ependymal cells located?
They form the epithelium called ependyma, and they line the central canal of the spinal cord and the ventricles of the brain
What do the ependymal cells do?
They secrete CSF (cerebrospinal fluid), they have cilia or microvilli that circulate the CSF, they monitor the CSF, and they contain stem cells for repair
What do astrocytes and satellite cells do?
They maintain the blood-brain barrier, they repair damaged neural tissue, and they guide neuron development.
What do microglia do?
They migrate through neural tissue and clean up cellular waste/debris/pathogens
What do oligodendrocytes do?
Their processes contract other neurons and they wrap around the axons to form the CNS myelin sheath (which speeds up action potentials and makes nerves appear white)
What do Schwann cells do?
They form the myelin sheath around peripheral axons
Define the electrochemical gradient
It’s the sum of chemical and electrical forces acting on the ion across a cell membrane
Define passive ion channels
Passive channels are leaky and always open, and their permeability changes with conditions.
Define active ion channels
Active channels are gated and open and close in response to stimuli.
What are the three types of gated channels?
Chemical, voltage, and mechanical
Describe chemically gated channels
They open when bound to chemicals, and are found on the neuron cell body + dendrites
Describe voltage gated channels
They open with electricity and are found on axons, the sarcolemma, and the heart
Describe mechanically gated channels
They respond to membrane distortion and are found in sensory receptors
What does the sodium potassium pump do?
It resets the membrane balance of ions and reestablishes the concentration gradient for each ion
How does the binding of neurotransmitters with receptors affect the movement of either sodium or potassium? What effect does this have on the membrane?
During hyperpolarization, potassium channels open and positive ions move out, causing the membrane to be more negative. The sodium potassium pump maintains and restores the resting potential and makes it more positive.
Define hyperpolarization
The negativity of the resting potential increases as a result of opening a potassium channel. Positive ions move out.
What are the two types of refractory periods?
Absolute and relative
What’s the relationship between axon diameter and the speed of transmission?
The bigger the axon’s diameter, the faster the speed
Describe continuous propagation
It happens in unmylinated axons, all parts of the membrane are depolarized, and the action potential travels in one direction
Describe salutatory propagation
It’s fast and doesn’t use much energy, it happens in myelinated axons, and the local current jumps from node to node
Define refractory period
The time in which the membrane won’t respond normally to additional stimuli
Describe an absolute refractory period
When sodium channels are open or inactivated and no action potential is possible
Describe a relative refractory period
The membrane potential is almost normal and a very large stimulus can initiate action potential
