BIOL 1191 - Chapter 12: Nervous Tissue Flashcards
what does the nervous system do?
helps all parts of the body to communicate with each other; works with the endocrine system to regulate and maintain homeostasis
what does the nervous system use?
specialized cells, electrical and chemical means to detect and respond to internal and external changes in a cell’s environment
detection + Response = ?
integration; special cells can be excited to generate nerve impulses
what does the nervous system determine?
human perception, memory, behavior, and movement
what are the three functions of the nervous system?
sensory, integrative, and motor function
what is the nervous system sensory function?
sensory neurons (receptors) detect changes in the internal and external environment
what is the nervous system integrative function?
interneurons analyze incoming sensory information, store some information, make decisions regarding appropriate behaviours
what is the nervous system motor function?
motor neurons initiate appropriate responses to stimuli by activating effectors such as muscles and glands
what are the two main branches of the nervous system?
central and peripheral nervous system
what are the specific components of the PNS?
all nervous tissue outside of the CNS, cranial nerves (12 pairs), spinal nerves (31 pairs), and sensory receptors
what are sensory receptors?
found in the PNS, and is a structure in the nervous system that monitors changes in the external or internal environment
what divisions is the PNS divided into?
sensory (afferent) and motor (efferent) divisions
what is the sensory (afferent) division in the PNS?
provides CNS with sensory info about somatic senses (tactile, thermal, pain, proprioceptive) and special senses (smell, taste, vision, hearing, equilibrium).
what is the motor (efferent) division in the PNS?
converys output from the CNS to effectors (muscles and glands).
what is the motor (efferent) division further SUBDIVIDED into?
somatic and autonomic nervous system
what is the somatic nervous system
a subdivision of the motor division that relays outputs from the CNS to only skeletal muscles; voluntary
what is the autonomic nervous system?
a subdivision of the PNS’ motor division. Relays output to smooth muscle, cardiac muscle, and glands, and is involuntary
what are the branches of the autonomic nervous system?
sympathetic and parasympathetic typically innervate the same effectors, but have opposing actions. Enteric plexuses regulates the activity of the smooth muscles and glands of the digestive canal
what are neurons?
functional, electrically excitable cellular structures that generate nerve impulses (action potentials), and does NOT undergo mitotic division
what is neuroglia?
support, protect, and nourish neurons and maintain interstitial fluid, and can undergo mitotic cell division
what is a nerve made out of?
a nerve is a bundle of 100-100s of axons (plus connective tissues and blood vessels) OUTSIDE of the brain or spinal cord. Nerves are apart of the PNS
what are neurons?
the functional unit of the nervous system and connects all regions of the body to the body to the brain and spinal cord. They are electrically excitable and generate nerve impulses (action potentials) in response to a stimulus; transmits signals from one cell to another through APs
what are the parts of a neuron?
cell body (soma): nucleus, nissl bodies, ribosomes, neurofibrils, microtubules, mitchondrion
cell processes: dendrites, axons
what are dendrites?
short, branched, and unmyelinated processes of the neuron. Has neurofibrils and nissl bodies
what is the function of dendrites?
It is the receiving part of the neuron and conducts nerve impulses towards the cell body; makes contact with other cells and contains numerous receptor sites from binding chemical messengers from other cells
what are axons?
single, long processes that act as a trigger zone for action potentials in a neuron. Contains axoplasm (cytoplasm) and is surrounded by the axolemma (plasma membrane). End in fine processes called axon terminals with synaptic end bulbs that contain synaptic vesicles that store neurotransmitters
what is the function of axons?
conducts nerve impulses (APs) away from the cell body to other neurons, muscle, or gland cells
what is a nucleus?
a cluster of neuronal cell bodies in the CNS
what is a ganglion?
a cluster of neuronal cell bodies in the PNS
what are tracts?
bundles of axons in the CNS
what are nerves?
bundles of axons in the PNS
how is the structural classification of neurons determined by?
it is based on the number of processes extending from the cell body
what are the three structural classifications of a neuron
multipolar, bipolar, and unipolar neurons
what is a multipolar neuron?
several dendrites, but only one axon; all motor neurons and most CNS neurons (interneurons are multipolar)
what are bipolar neurons?
one dendrite and one axon; can be found in the retina of the eye, inner ear, olfactory area of the brain
what are pseudounipolar/unipolar neurons?
one fused dendrite and axon; dendrites act as sensory receptors for stimulus of somatic senses
what are the three functional classifications of neurons
sensory (afferent), motor (efferent), and interneurons
what are sensory (afferent) neurons?
forms nerve impulses in response to stimuli. sends impulse to the CNS through cranial and spinal nerves
what are motor (efferent) neurons?
sends commands from the CNS to muscles and glands (effectors) through spinal and cranial nerves
what are interneurons?
processes incoming sensory information and initiates motor response; connects sensory to motor neurons in the CNS
what is neuroglia?
makes up half the volume of the CNS, smaller than neurons and more numerous, undergoes mitotic cell division, and isn’t electrically excitable
what is the function of neuroglia?
support, protect, nourish neurons, and maintain interstitial fluid
which neuroglial cells are found in the CNS?
astrocytes, oligodendrocytes, microglial and ependymal cells
which neuroglial cells are found in the PNS?
schwann cells and satellite cells
what is the structure of astrocytes?
largest and most numerous neuroglial cells, star-shaped, and processes contact with other cells
protoplasmic astrocytes: short, branching processes
fibrous astrocytes: long unbranched processes
what are the functions of astrocytes?
provide structural support for neurons, processes help form the blood-brain barrier, regulate ion and neurotransmitter concentrations in the interstitial fluid, help in the formation of neural synapse (site of nerve impulse transmission) and regulate chemicals needed for neuron development in embryos
what are oligodendrocytes?
neuroglial cells, smaller than astrocytes and has fewer processes. It forms and maintains the myelin sheath around CNS axons; one oligodendrocytes can myelinate several CNS axons
what are microglial cells?
small neuroglial cells with slender processes. they are phagocytic cells, refine synapses during development using phagocytosis; the immune cells of the CNS
what are ependymal cells?
neuroglial cells with a cuboidal/columnar shape that contain microvilli and cilia. It is the epithelial membrane that lines ventricles of the brains and central canal of the spinal cord; produces cerebrospinal fluid and forms blood-csf barrier
what are satellite cells?
neuroglial cells that surround clusters of neuronal cell bodies in the PNS; provides support for neurons, and regulates the exchange of material between neuronal cell bodies and interstitial fluid
what are schwann cells?
enclose axons in the PNS, and has cytoplasm and nucleus
what is the function of the myelin sheath in the PNS?
it electrically insulates axons and increases the speed of nerve impulses (coordination)
what are the functions of schwann cells?
forms the myelin sheath around some axons, helps with axon regeneration. Gaps between myelin sheaths (nodes of Ranvier) occur along axon between schwann cells
what is the function of neurolemma in the PNS?
aids in regeneration of neuroglial cells
which neuroglial cells are schwann cells analogous to?
oligodendrocytes
what is white matter?
primarily myelinated axons
what is grey matter?
cell bodies, dendrites, neuroglia, unmyelinated axons, axon terminals, nissl bodies
how do neurons communicate?
they are electrically excitable, so they communicate with each other using electrical signals
how can nerve cells be excitable?
- the plasma membrane has a resting membrane potential
→ the cell is polarized (negatively charged) due to unequal distribution, or movement of ions across the cell membrane - the presence of specific types of ion channels
what are the two types of electrical signals neurons use?
graded potentials: short-distance communication
action potentials: long-distance communication
what are leak channels?
a type of ion channel that randomly opens and closes. There are more potassium (K+) channels than sodium (Na+) channels
what are ligand-gated channels?
an ion channel that opens and closes in response to a chemical (ligand) stimulus that binds to a receptor
→ neuromuscular junction
what are mechanically gated channels?
ion channels that opens or closes in response to mechanical stimulus
→ vibration or pressure
what are voltage gated channels?
an ion channel that opens in response to a change in membrane potential (voltage)
→ sarcoplasmic reticulum
what are the two types of action potential propagation
continuous conduction: step by step along the axon, unmyelinated, slower, and has an even distribution of gated channels
saltatory conduction: leap from gap-to-gap along the axon, myelinated, energy efficient, faster, uneven distribution of channels
what is a synapse?
the region where communication occurs between two neurons of between a neuron and an effector cell (muscle or glandular cell)
what is an electrical synapse?
and ionic current spread to the next cell through gap junctions
→ faster, capable of synchronizing groups of cells/neurons
→ common in visceral smooth muscle, cardiac muscle, and the developing
embryo
what is a chemical synapse?
the plasma membranes of cells do not touch and are separated by the synaptic cleft
→ one way information transfer from a presynaptic neuron to a postsynaptic cell
→ involves neurotransmitters and receptors
what is spatial summation?
neurotransmitters from several end bulbs onto one neuron
what is temporal summation?
neurotransmitters released from 2 or more firings of the same end bulb in rapid succession
what are the 2 types of electrical signals?
graded and action potentials
what are the 2 types of graded potentials?
hyperpolarizing and depolarizing graded potentials
Why does a stronger stimulus lead to a larger graded potential than a weaker stimulus?
a weaker stimulus will allow fewer ions to pass through, larger stimulus’ will do the opposite; it’s mainly determined on how many ions are present, and how long the ion channels will stay open
what does graded mean?
vary in amplitude depending on the strength of the stimulus
what is a synapse, and what are the 2 types of synapses?
the region where communication occurs between two neurons or between a neuron and an effector cell; electrical and chemical synapses
what is an electrical synapse?
an ionic current spread to the next cell through gap junctions; these synapses are faster, and capable of synchronizing groups of cells/neurons. common in smooth, cardiac muscle, and the developing embryo
what is a chemical synapse?
the plasma membranes of cells don’t touch and are separated by a synaptic cleft; it is a one way information transfer from a presynaptic neuron to a postsynaptic cell. involves neurotransmitters and receptors
