Nervous System Flashcards
Neuron
A nerve cell that is capable of conducting nerve impulses
Afferent neuron
A neuron that carries impulses from sensory receptors to the central nervous system; also called a sensory neuron
Interneuron
A local circuit neuron of the central nervous system that relays impulses between afferent (sensory) and efferent (motor) neurons
Efferent neuron
A neuron that carries impulses from the central nervous system to skeletal muscles; also known as a motor neuron
Dendrite
A projection of cytosol that carries signals toward the nerve cell body
Axon
An extension of cytosol that carries nerve signals away from the nerve cell body
Glial cell
A non-conducting cell that is important for the structural support and metabolism of nerve cells
Ex. Schwann cells
Myelin sheath
An insulated covering over the axon of nerve cell
node of Ranvier
A regularly occurring gap between sections of myelin sheath along the axon
Central nervous system (CNS)
The body’s coordinating centre for mechanical and chemical actions; made up of the brain and spinal cord
Peripheral nervous system (PNS)
All parts of the nervous system, excluding the brain and spinal cord; relays information between the CNS and other parts of the body
Ex. afferent and efferent system
Afferent system
The component of the PNS that receives input through receptors and transmits the input to the CNS
Ex. sensory receptors
Efferent system
The component of the PNS that varies signals away to the effectors (muscles and glands)
Ex. skeletal and smooth muscles, and glands
Somatic system
A subdivision of the efferent system (within the PNS); composed of efferent (motor) neurons that carry signals to skeletal muscles in response to external stimuli
Ex. communication with the skeletal muscles, and voluntary processes (some contractions like reflexes and shivers are involuntary)
Autonomic system
A subdivision of the efferent system (within the PNS); regulates the internal environment
Ex. communication with smooth muscles and glands and involuntary processes, such as digestion, secretion by sweat glands, circulation of blood, etc.
Sympathetic system
One of the two subdivision of the autonomic nervous system; increase energy consumption and prepares the body for action
Ex. dominates situations that involve stress, danger, etc., and increase heart rate, raise blood pressure by vasoconstriction, dilate pupils, etc.
Parasympathetic system
One of two subdivisions of the autonomic nervous system; stimulates body activities that acquire and conserve energy
Ex. dominate in quiet, low-stress situations, and reduce rapid heartbeat and elevated blood pressure, and digestion predominates
Neural circuit
The coordination of the receptor, afferent neuron, interneuron, efferent neuron, and effector in response to a stimulus
Reflex arc
A neural circuit that travels through the spinal cord but does not require the coordination of the brain; allows for reflex actions
Ex. withdrawal reflex when your finger touches a hot object
Synapse
A functional connection between neurons or between neurons and effectors
Ex. chemical or electrical synapses
Chemical synapse
A synapse in which a neurotransmitter moves from a presynaptic cell to a postsynaptic cell through the synaptic cleft
Neurotransmitter
A chemical that is released from vesicles into synapses to facilitate nerve signal transmission
Synaptic cleft
The tiny gap between presynaptic and postsynaptic cells in a chemical synapse, across which the neurotransmitter diffuses
Electrical synapse
A synapse in which the presynaptic cell makes direct contact with the postsynaptic cell, allowing current to flow via gap junctions between the cells
Membrane potential
The electrical potential of a membrane, which is caused by an imbalance of charges on either side of the membrane
Ion channel
A protein embedded in the plasma membrane that allows ions to pass through it
Resting potential
The voltage difference across a nerve cell membrane of an unstimulated neuron; usually negative
Ex. a typical neuron that isn’t conducting an impulse exhibits a steady resting potential of -70mV
Action potential
The voltage difference across a nerve cell membrane when the nerve is excited (more positive charge)
Threshold potential
The potential at which an action potential is generated by a neuron
Ex. about -50 to -55mV in a typical neuron
Refractory period
The period of time during which the threshold required for the generation of an action potential is much higher than normal
Meninges
Three layers of connective tissue that surround and protect the brain and spinal cord
Cerebrospinal fluid
Circulating fluid that surrounds the membranes of the brain and spinal cord; provides neural connection to the endocrine system
Grey matter
The tissue of the brain and spinal cord where the cell bodies and dendrites of neurons are located
White matter
The tissue of the brain and spinal cord, composed primarily of axons of neurons; in the spinal cord, it surrounds the grey matter
Medulla oblongata
The hindbrain region that connects the spinal cord to the cerebellum; important in autonomic nerve control
Cerebellum
The hindbrain region that is involved in muscle movement and balance
Pons
The brain region that transfers nerve signals between the cerebellum and the medulla
Cerebrum
The brain region that is involved in motor activities and sensory information; the largest and most developed region of the brain
Cerebral cortex
The outermost layer of the cerebral hemispheres
Thalamus
The brain region that interprets sensory input and signals the cerebrum
Blood-brain barrier
A barrier formed by tight junctions between endothelial cells in the capillaries in the brain that blocks the movement of most substances into the brain via the bloodstream
Spinal nerves
The 31 pairs of nerves within the somatic system that transmit motor, sensory, and autonomic signals between the spinal cord and the rest of the body
Ex. 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal
Cranial nerves
The 12 pairs of nerves with the parasympathetic division of the autonomic system, which emerge directly from the brain and serve the head, neck, and body trunk
Ex. optical, facial, etc.
