Nervous System Flashcards
Three Functions of the Nervous System
Receives sensory input (internal and external) - PNS -> CNS
Processes and integrates information
Generates motor output
Two Major Components
Central Nervous System
Peripheral Nervous System
Central Nervous system consists of…
Brain and spinal cord
Neurons
Cells that transmit nerve impulses
Neuroglia (Glial Cells)
Support and nourish neurons; more numerous than neurons in brain
Two types of Neuroglia
Schwann cells
Oligodendrocytes
Schwann Cells
Form myelin sheath (insulators) of neurons in peripheral nervous system, leaving gaps called nodes of Ranvier
Oligodendrocytes
Form myelin sheath in central nervous system - “white matter”
Nervous Tissue
Located in the nerves, and conducts nerve impulses
Myelin Sheath
A lipid covering on long axons that acts to increase the speed of nerve impulse conduction, insulation, and regeneration in the peripheral nervous system
Nodes of Ranvier
Gaps between myelination on the axons
Saltatory Conduction
Conduction of the nerve impulse from node to node (don’t have to open so many ion channels)
Multiple Sclerosis
Disease in which the myelin sheath is attacked by the immune system, causing malfunctioning of the nervous system and muscle weakness or paralysis
Three types of neurons
Sensory
Interneuron
Motor
Sensory Neuron
Transports nerve signals from sensory receptors to central nervous system
Receptor
Special structures that detect changes in the environment
Interneuron
Lie within central nervous system; composite input from sensory neurons and other interneurons, then communicate with motor neurons
Motor
Transport impulses from central nervous system to effector
Effector
Carry out responses to environmental changes
Dendrite
Many short extensions that carry impulses to a cell body
Cell body
Main cell where organelles and nuclei reside
Axon (nerve fiber)
Single, long extension that carries impulses away from the cell body (exception - sensory neuron)
Synapse
Small gap between the sending neuron (pre-synaptic membrane) and the receiving neuron (post-synaptic membrane)
How do signals get from sensory neurons to the brain and then to the right neurons to get muscles to move?
Sensor -> Afferent Pathway -> integration -> Efferent Pathway -> Motor
Nerve Impulses
Convey information in nervous system, i.e., action potential, via electrochemical signals
Resting Potential
Axon is NOT conducting a nerve impulse
State of a cell during resting potential
Inside of the cell has a negative charge, with more positive ions outside the membrane. There is more Na+ outside the cell than inside, but more K+ inside than outside (along with large anions - )
Action Potential
Rapid change in the axon membrane that allows a nerve impulse to occur
What occurs during the action potential stage?
Sodium gates open, letting Na+ in, and depolarization occurs - the interior of the axon loses negative charge and becomes positively charged (from -70 mV to 40 mV).
What occurs during the repolarization stage?
Action potential ends, and repolarization occurs - K+ moves out. But, Na+ and K+ are in the wrong place, so the sodium-potassium pump restores resting potential - actively pumps 3 Na+ out for every 2 K+ in.
When a nerve impulse reaches the end of the axon, it causes the release of what?
A neurotransmitter
Inhibitory Synapse
Promotes decrease in action potential
Excitatory Synapse
Promotes increase in action potential
How many known neurotransmitters?
Over 100
What does the response a neurotransmitter triggers depend on?
The receptor to which it attaches
Acetylcholine
Muscle stimulation/inhibition, memory formation, learning
Norepinephrine
Smooth muscle function, dreaming, waking, mood
Dopamine
Sense of reward/pleasure
Serotonin
Thermoregulation, sleeping, emotions, perception
The Central Nervous System is protected by what?
Bones, meninges, and cerebral spinal fluid
Meninges
Protective membranes that wrap around CNS
Cerebral Spinal Fluid
Space between meninges is filled with this fluid that cushions and protects the CNS
Spinal cord and brain consist of:
Gray matter
White matter
Ventricles
Gray matter
Neuron cell bodies, dendrites, and unmyelinated axons
White Matter
Bundles of axons with myelin sheafs
Ventricles
Spaces filled with cerebrospinal fluid (central canal of spinal cord)
What does the cerebrospinal fluid do?
Circulates slowly in the ventricles, supplies nutrients and removes wastes, and cushions the CNS by circulating in meninges.
Occipital Lobe
Controls the visual processing abilities
Central Sulcus
Divides the frontal and parietal lobes
Sulcus
“Valley” in the brain
Gyrus
“Ridge” in the brain
What does the central sulcus house?
The primary motor and somatosensory area.
Longitudinal fissure
Divides cerebrum into left and right hemispheres
Left hemisphere controls…
Language skills, math, and other logical and analytical abilities (as well as the right side of the body)
Right hemisphere controls…
Spatial skills, face and pattern recognition, and nonverbal thinking (as well as the left side of the body)
Three ways in which we study to brain
Injuries
Mapping
Imaging
What does brain mapping do?
Allows us to link a brain location to a specific function of the brain
Wernicke’s Area
Located in the left temporal posterior section, it helps us understand written and spoken words
Broca’s Area
Located in the left frontal section, it helps us speak and write
Short-term memory
Begins in prefrontal area, and precedes long-term memory
Long-term memory
Stored in the association areas of the cerebral cortex, and accessed by the hippocampus and relayed to the prefrontal area. Short term memories are integrated into existing knowledge (long term memory) via the hippocampus.
PNS - Somatic System - Functions
Voluntary - serves the skin, skeletal muscles, and tendons
Involuntary - knee-jerk reflex
PNS Autonomic
Regulates the activity of involuntary muscles (smooth and cardiac), and can be divided into parasympathetic and sympathetic sections
Most drug abusers take drugs that affect which neurotransmitter?
Dopamine. They artificially affect this reward circuit to the point they ignore basic physical needs in favor of the drug.
Sympathetic part of the PNS
Fight or Flight
Parasympathetic part of the PNS
Rest and Digest
