Human Physiology, Vander Ch.6
Terms
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- Hypothalamus
- Brain region below thalamus; responsible for integration of many basic neural, endocrine, and behavioral functions, especially those concerned with regulation of internal environment
- Limbic system
- Interconnected brain structures in cerebrum; involved with emotions and learning
- Reticular formation
- (reticular activating center) – extensive neuron network extending through brainstem core; receives and integrates information from many afferent pathways and from other CNS regions.
- Cranial nerves
- One of 24 peripheral nerves (12 pairs) that join brainstem or forebrain with structures outside CNS
- Dorsal root
- Group of afferent nerve fibers that enters dorsal region of spinal cord
- Dorsal root ganglia
- Group of sensory nerve cell bodies that have axons projecting to the dorsal horn of the spinal cord.
- Ventral root
- One of two groups of efferent fibers that leave ventral side of spinal cord.
- Spinal nerve
- One of 86 peripheral nerves (43 pairs) that join spinal cord
- Central nervous system (CNS)
- Brain plus spinal cord
- Peripheral nervous system
- Nerve fibers extending from CNS.
- Neuron (Nerve cell)
- Cell in nervous system specialized to initiate, integrate, and conduct electrical signals
- Neurotransmitters
- Chemical messenger used by neurons to communicate with each other or with effectors
- Integrators (Integrating center)
- Cells that receive one or more signals and send out appropriate response
- Processes
- Long extension from neuron cell body
- Cell body (soma)
- In cells with long extensions, the part that contains the nucleus
- Dendrites
- Highly branched extension of neuron cell body; receives synaptic input from other neurons
- Axon
- Extension from neuron cell body; propagates action potentials away from cell body; also called a nerve fiber
- Nerve fiber
- axon of a neuron
- Initial segment (axon hillock)
- first portion of axon plus the part of the cell body where axon arises
- Collaterals
- Branch of a nerve axon
- Axon terminal
- End of axon; forms synaptic or neuroeffector junction with postjunctional cell
- Varicosities
- swollen region of axon; contains neurotransmitter-filled vesicles; analogous to presynaptic ending
- Myelin
- insulating material covering axons of many neurons; consists of layers of myelin-forming cell plasma membrane wrapped around axon
- Oligodendrocytes
- type of glial cell; responsible for myelin formation in CNS
- Schwann cells
- nonneural cell that forms myelin sheath in peripheral nervous system
- Nodes of Ranvier
- space between adjacent myelin-forming cells along myelinated axon where axonal plasma membrane is exposed to extracellular fluid
- Axon transport
- Process involving intracellular filaments by which materials are moved from one end of axon to other
- Afferent neurons
- Neuron that carries information from sensory receptors at its peripheral endings to CNS; cell body lies outside CNS.
- Efferent neurons
- neuron that carries information away from CNS
- Interneurons
- neuron whose cell body and axon lie entirely in CNS
- Sensory receptors
- a cell or portion of a cell that contains structures or chemical molecules sensitive to changes in an energy form in the outside world or internal environment; in response to activation by this energy, the sensory receptor initiates action potentials in that cell or an adjacent one.
- Nerves
- Group of many nerve fibers traveling together in peripheral nervous system.
- Synapse
- anatomically specialized junction between two neurons where electrical activity in one neuron influences excitability of second; see also chemical synapse, electrical synapse, excitatory synapse, inhibitory synapse
- Presynaptic neuron
- Neuron that conducts action potentials toward a synapse
- Postsynaptic neuron
- Neuron that conducts information away from a synapse
- Glial cells
- nonneuronal cell in CNS; helps regulate extracellular environment of CNS; also called neuroglia
- Astroglia
- a form of glial cell that regulates composition of extracellular fluid around neurons and forms the blood-brain barrier
- Microglia
- a type of glial cell that acts as a macrophage
- Stem cells
- cell that in adult body divides continuously and forms supply of cells for differentiation
- Growth cone
- tip of developing axon
- Neurotropic factors
- protein that stimulates growth and differentiation of some neurons.
- Electric potential (potential)
- voltage difference between two points; see also action potential, graded potential
- Potential difference (potential)
- A difference in charge between two points
- Current
- movement of electric charge; in biological systems, this is achieved by ion movement.
- Resistance (R)
- hindrance to movement through a particular substance, tube, or opening
- OhmÂ’s Law
- current (I) is directly proportional to voltage (E) and inversely proportional to resistance (R) such that I = E / R
- Resting membrane potential
- voltage difference between inside and outside of cell in absence of excitatory or inhibitory stimulation; also called resting potential
- Equilibrium potential
- voltage gradient across a membrane that is equal in force but opposite in direction to concentration force affecting a given ion species.
- Nernst equation
- calculation for electrochemical equilibrium across a membrane for any single ion
- Goldman equation
- calculation for electrochemical equilibrium when a membrane is permeable to more than one ion
- Leak potassium channels
- potassium channels that are open when a membrane is at rest
- Electrogenic pump
- active transport system that directly separates electrical charge, thereby producing a potential difference
- Depolarized
- to change membrane potential value toward zero so that cell interior becomes less negative than resting level
- Overshoot
- part of the action potential in which the membrane potential goes above zero.
- Repolarizing
- return transmembrane potential to its resting level
- Hyperpolarized
- to change membrane potential so cell interior becomes more negative than its resting state
- Graded potentials
- membrane potential change of variable amplitude and duration that is conducted decrementally; has no threshold or refractory period
- Summation
- increase in muscle tension or shortening in response to rapid, repetitive stimulation relative to single twitch
- Action potentials
- electrical signal propagated by nerve and muscle cells; an all-or-none depolarization of membrane polarity; has a threshold and refractory period and is conducted without decrement
- Excitable membranes
- membrane capable of producing action potentials
- Excitability
- ability to produce electric signals
- Threshold potential (threshold)
- membrane potential to which excitable membrane must be depolarized to initiate an action potential.
- Afterhyperpolarization
- decrease in membrane potential in neurons at the end of the action potential
- Positive feedback
- characteristic of control systems in which an initial disturbance sets off train of events that increases the disturbance even further; compare negative feedback
- Inactivation gate
- portion of the voltage-gated sodium or potassium channel that closes the channel
- Threshold stimuli
- stimulus capable of depolarizing membrane just to threshold
- Subthreshold potentials
- depolarization less than threshold potential
- Subthreshold stimuli
- stimulus capable of depolarizing membrane but not by enough to reach threshold
- All-or-none
- pertaining to event that occurs maximally or not at all
- Absolute refractory period
- time during which an excitable membrane cannot generate an action potential in response to any stimulus.
- Efferent division (PNS)
- Neurons in the peripheral nervous system that project out of the central nervous system.
- Relative refractory period
- time during which excitable membrane will produce action potential but only to a stimulus of greater strength than the usual threshold strength.
- Action potential propagation
- Every new action potential produces local currents of its own, which depolarize the region adjacent to it, producing yet another action potential at the next site, and so on to cause action potential propagation along the length of the membrane.
- Saltatory conduction
- propagation of action potentials along a myelinated axon such that the action potentials jump from one node of Ranvier in the myelin sheath to the next node
- Receptor potential
- graded potential that arises in afferent neuron ending, or a specialized cell intimately associated with it, in response to stimulation.
- Synaptic potential
- see postsynaptic potential -
- Pacemaker potential
- neurons that set rhythm of biological clocks independent of external cues; any nerve or muscle cell that has an inherent autorhythmicity and determines activity pattern of other cells
- Excitatory synapse
- synapse that, when activated, increases likelihood that postsynaptic neuron will undergo action potentials or increases frequency of existing action potentials.
- Inhibitory synapse
- synapse that, when activated, decreases likelihood that postsynaptic neuron will fire an action potential (or decrease frequency of existing action potentials)
- Convergence
- (neuronal) many presynaptic neurons synapsing upon one postsynaptic neuron; (of eyes) turning of eyes inward (that is, toward nose) to view near objects
- Divergence
- (neuronal) one presynaptic neuron synapsing upon many postsynaptic neurons; (of eyes) turning of eyes outward to view distant objects
- Electrical synapse
- synapse at which local currents resulting from electrical activity flow between two neurons through gap junctions joining them.
- Chemical synapse
- synapse at which neurotransmitters released by one neuron diffuse across an extracellular gap to influence a second neuron's activity
- Synaptic vesicles
- cellular structure that holds and releases neurotransmitter at the synapse
- Postsynaptic density
- area in the postsynaptic cell membrane that contains neurotransmitter receptors and structural proteins important for synapse function
- Synaptic cleft
- narrow extracellular space separating pre- and postsynaptic neurons at chemical synapse
- Cotransmitter
- chemical messenger released with a neurotransmitter from synapse or neuroeffector junction
- SNARE proteins
- proteins in the nerve terminal involved in moving synaptic vesicles to the nerve terminal for release of neurotransmitter into the synaptic cleft
- Synaptotagmin
- protein present in wall of synaptic vesicle that binds calcium and helps stimulate the process of exocytosis
- Synaptic delay
- length of time it takes for electrical changes to move from the presynaptic to the postsynaptic membrane
- Reuptake
- active process that recaptures excess secreted neurotransmitter back into the presynaptic cell; can be inhibited with drugs
- Excitatory postsynaptic potential (EPSP)
- depolarizing graded potential in postsynaptic neuron in response to activation of excitatory synapse
- Inhibitory postsynaptic potential (IPSP)
- hyperpolarizing graded potential that arises in postsynaptic neuron in response to activation of inhibitory synaptic endings upon it
- Temporal summation
- membrane potential produced as two or more inputs, occurring at different times, are added together; potential change is greater than that caused by single input
- Spatial summation
- adding together effects of simultaneous inputs to different places on a neuron to produce potential change greater than that caused by single input
- Axo-axonic synapse
- presynaptic synapse where an axon stimulates the presynaptic terminal of another axon
- Presynaptic inhibition
- inhibitory input to neurons through synapses at the nerve terminal
- Presynaptic facilitation
- excitatory input to neurons through synapses at the nerve terminal
- Autoreceptors
- receptors on a cell affected by a chemical messenger released from the same cell
- Receptor desensitization
- temporary inability of a receptor to respond to its ligand due to prior ligand binding
- Agonists
- chemical messenger that binds to receptor and triggers cell's response; often refers to drug that mimics action of chemical normally in the body
- Antagonists
- (drug) molecule that competes with another for a receptor and binds to the receptor but does not trigger the cell's response
- Neuromodulators
- chemical messenger that acts on neurons, usually by a second-messenger system, to alter response to a neurotransmitter
- Acetylcholine (Ach)
- a neurotransmitter released by pre- and post-ganglionic parasympathetic neurons, preganglionic sympathetic neurons, somatic neurons, and some CNS neurons
- Cholinergic
- pertaining to acetylcholine; a compound that acts like acetylcholine
- Acetylcholinesterase
- enzyme that breaks down acetylcholine into acetic acid and choline
- Nicotinic receptors
- acetylcholine receptor that responds to nicotine; primarily, receptors at motor end plate and on postganglionic autonomic neurons
- Muscarinic receptors
- acetylcholine receptor that responds to the mushroom poison muscarine; located on smooth muscle, cardiac muscle, some CNS neurons, and glands
- Biogenic amines
- one of family of neurotransmitters having basic formula R-NH2; includes dopamine, norepinephrine, epinephrine, serotonin, and histamine
- Dopamine
- biogenic amine (catecholamine) neurotransmitter and hormone; precursor of epinephrine and norepinephrine; see also prolactin-inhibiting hormone
- Norepinephrine (NE)
- biogenic amine (catecholamine) neurotransmitter released at most sympathetic postganglionic endings, from adrenal medulla, and in many CNS regions
- Epinephrine (E)
- amine hormone secreted by adrenal medulla and involved in regulation of organic metabolism; a biogenic amine (catecholamine) neurotransmitter; also called adrenaline
- Catecholamines
- dopamine, epinephrine, or norepinephrine, all of which have similar chemical structures
- L-dopa
- L-dihydroxyphenylalanine; precursor to dopamine formation
- Monoamine oxidase (MAO)
- enzyme that breaks down catecholamines in nerve terminal and synapse
- Adrenergic
- pertaining to norepinephrine or epinephrine; compound that acts like norepinephrine or epinephrine
- Noradrenergic
- referring to neurons that release norepinephrine as a neurotransmitter or membrane receptors that bind norepinephrine
- Alpha-adrenergic receptors
- one type of plasma-membrane receptor for epinephrine and norepinephrine; also called alpha adrenoceptor; compare beta-adrenergic receptor
- Beta-adrenergic receptors
- a type of plasma membrane receptor for epinephrine and norepinephrine; compare alpha-adrenergic receptor; also called beta adrenoceptor
- Metabotropic receptor
- membrane receptor in neurons that initiates formation of second messengers when bound with ligand
- Serotonin
- biogenic amine neurotransmitter; paracrine agent in blood platelets and digestive tract; also called 5-hydroxytryptamine, or 5-HT
- Excitatory amino acids
- amino acid that acts as an excitatory (depolarizing) neurotransmitter in the nervous system
- Glutamate
- anion formed from the amino acid glutamic acid; a major excitatory CNS neurotransmitter
- Aspartate
- an excitatory neurotransmitter in CNS; ionized form of the amino acid aspartic acid
- Ionotropic receptors
- membrane receptor in neurons that is an ion channel that is opened by binding of its ligand
- n-methyl-d-aspartate (NMDA)
- ionotropic glutamate receptor involved in learning and memory
- GABA (gamma-aminobutyric acid)
- major inhibitory neurotransmitter in CNS
- Glycine
- an amino acid; a neurotransmitter at some inhibitory synapses in CNS
- Neuropeptides
- family of more than 50 neurotransmitters composed of 2 or more amino acids; often also functions as chemical messenger in nonneural tissues
- Peptidergic
- neuron that releases peptides
- Endogenous opioids-beta-endorphin
- certain neuropeptides – endorphin, dynorphic, and enkephalin
- Dynorphins
- Certain neuropeptides, termed endogenous opioids-beta-endorphin, the dynorphins, and the enkephalins – have attracted much interest because their receptors are the sites of action of opiate drugs such as morphine and codeine.
- Enkephalins
- peptide neurotransmitter at some synapses activated by opiate drugs; an endogenous opioid
- Substance P
- neuropeptide neurotransmitter released by afferent neurons in pain pathway as well as other sites.
- Nitric oxide
- A gas that functions as intercellular messenger, including neurotransmitters; is endothelium-derived relaxing factor; destroys intracellular microbes.
- Carbon monoxide
- CO; gas that reacts with hemoglobin; decreases blood oxygen-carrying capacity and shifts oxygen-hemoglobin dissociation curve to the left; also acts as an intracellular messenger in neurons.
- adenosine triphosphate (ATP)
- major molecule that transfers energy from metabolism to cell functions during its breakdown to ADP and release of Pi
- Adenine
- one of the four bases making up DNA; also a breakdown product of ATP used as a neurotransmitter
- Pathway (tract)
- series of connected nerves that move a particular type of information from one part of the brain to another part
- Commissure
- Bundle of nerve fibers linking right and left halves of the brain.
- Cerebrum
- Part of the brain that, with diencephalons, forms the forebrain
- Diencephalons
- Core of anterior part of brain; lies beneath cerebral hemispheres and contains thalamus and hypothalamus.
- Brainstem
- brain subdivision consisting of medulla oblongata, pons, and midbrain and located between spinal cord and forebrain
- Cerebellum
- Brain subdivision lying behind forebrain and above brainstem; deals with muscle movement control.
- Forebrain
- Large, anterior brain subdivision consisting of right and left cerebral hemispheres (the cerebrum) and diencephalons.
- Midbrain
- The most rostral section of the brainstem.
- Pons
- large area of the brainstem containing many nerve axons
- Medulla oblongata
- Part of the brain stem closest to the spinal cord
- Cerebral ventricles
- One of four interconnected spaces in the brain; filled with cerebrospinal fluid.
- Cerebral hemispheres
- Either left or right half of the cerebral cortex
- Cerebral cortex
- Cellular layer covering the cerebrum
- Gray matter
- area of brain and spinal cord that appears gray in unstained specimens and consists mainly of cell bodies and unmyelinated portions of nerve fibers
- White matter
- Portion of CNS that appears white in unstained specimens and contains primarily myelinated nerve fibers
- Subcortical nuclei
- groups of cells in brain below the cerebral cortex
- Corpus callosum
- Wide band of nerve fibers connecting the two cerebral hemispheres; a brain commissure.
- Frontal lobe
- Region of anterior cerebral cortex where motor areas, BrocaÂ’s speech center, and some association cortex are located
- Parietal lobe
- Region of cerebral cortex containing sensory cortex and some association cortex.
- Occipital lobe
- Posterior region of cerebral cortex where primary visual cortex is located
- Temporal lobe
- Region of cerebral cortex where primary auditory cortex and WernickeÂ’s speech center are located.
- Pyramidal cells
- Large neuron with characteristic pyramid-shaped cell body and apical dendrite
- Basal nuclei (Basal ganglia)
- Nuclei deep in cerebral hemispheres that code and relay information associated with control of body movements; specifically, caudate nucleus, globus passidus, and putamen; also called basal ganglia
- Thalamus
- Subdivision of diencephalons; integrating center for sensory input on its way to cerebral cortex; also contains motor nuclei
- Afferent division (PNS)
- Neurons in the peripheral nervous system that project to the central nervous system
- Somatic nervous system
- Component of efferent division of peripheral nervous system; innervates skeletal muscle; compare autonomic nervous system.
- Autonomic nervous system
- Component of efferent division of peripheral nervous system that consists of sympathetic and parasympathetic subdivisions; innervates cardiac muscle, smooth muscle, and glands; compare somatic nervous system.
- Motor neurons
- Somatic efferent neuron, which innervates skeletal muscle.
- Enteric nervous system
- Neural network residing in and innervating walls of gastrointestinal tract.
- Autonomic ganglion
- Group of neuron cell bodies in the peripheral nervous system.
- Preganglionic
- Autonomic-nervous-system neuron or nerve fiber whose cell body lies in CNS and whose axon terminals lie in a ganglion; conducts action potentials from CNS to ganglion; compare postganglionic
- Postganglionic
- Autonomic-nervous-system neuron or nerve fiber whose cell body lies in a ganglion; conducts impulses away from ganglion toward periphery; compare preganglionic
- Sympathetic division
- Portion of autonomic nervous system whose preganglionic fibers leave CNS at thoracic and lumbar portions of spinal cord; compare parasympathetic division
- Parasympathetic division
- Portion of the autonomic nervous system whose preganglionic fibers leave CNS from brainstem and sacral portion of spinal cord; most of its postganglionic fibers release acetylcholine; compare sympathetic division.
- Sympathetic trunk
- One of paired chains of interconnected sympathetic ganglia that lie on either side of vertebral column.
- Adrenal medulla
- Endocrine gland that forms inner core of each adrenal gland; secretes amine hormones, mainly epinephrine, compare adrenal cortex
- Dual innervation
- Innervation of an organ or gland by both sympathetic and parasympathetic nerve fibers.
- Fight-or-flight response
- Activation of sympathetic nervous system during stress
- Rest-or-digest
- Homeostatic state characteristic of parasympathetic nervous system activation
- Meninges
- Protective membranes that cover brain and spinal cord
- Dura mater
- Thick, outermost membrane (meninges) covering the brain.
- Arachnoid
- The middle of three membranes (meninges) covering the brain.
- Pia mater
- Innermost of three membranes (meninges) covering the brain.
- Subarachnoid space
- Space between the arachnoid and pia mater meninges containing cerebrospinal fluid.
- Cerebrospinal fluid (CSF)
- Fluid that fills cerebral ventricles and the subarachnoid space surrounding brain and spinal cord
- Choroid plexus
- Highly vascular epithelial structure lining portions of cerebral ventricles; responsible for much of cerebrospinal fluid formation.
- Blood-brain barrier
- Group of anatomical barriers and transport systems in brain capillary endothelium that controls kinds of substances entering brain extracellular space from blood and their rates of entry.