Module 1: Nervous System Flashcards
Anatomy
Structure of the body
Physiology (2)
1) How the body parts function together
2) The physiology of the body depends on the anatomy of the body
Nervous system (3)
1) Receives information
2) Processes information
3) Sends out signals to muscles and glands to elicit an appropriate response
Nervous tissue (3)
1) Responsible for communication between cells of the body
2) Done by forming system of electrical impulses that communicate rapidly
3) Like the wiring of the body
Central nervous system (2)
1) Brain, protected by skull
2) Spinal cord, protected by vertebrae
Skull
Protects brain
Vertebrae
Protect spinal cord
Nuclei
Collections of cell bodies inside the CNS
Tracts
Collection of nerve axons in the CNS
Peripheral nervous system (2)
1) All nerves not in the brain or spinal cord
2) Includes cranial nerves and spinal nerves
Brainstem regions (3)
1) Midbrain
2) Pons
3) Medulla
Cranial nerves (2)
1) Project from brainstem
2) Innervate the face, head and neck
Spinal nerves (2)
1) Project from either side of the spinal cord
2) Spread out to innervate the trunk and extremities
Ganglia
Collection of cell bodies inside the PNS
Nerves
Collection of nerve axons in the peripheral nervous system
Two divisions of peripheral nervous system (2)
1) Sensory (afferent) division
2) Motor (efferent) division
SAME acronym (2)
1) Sensory = Afferent
2) Motor = Efferent
Afferent division (2)
1) Receives impulses from the sensory organs
2) PNS to CNS
Efferent division (2)
1) Relays signals or impulses from the CNS to muscles and glands
2) CNS to PNS
Efferent division subdivisions (2)
1) Somatic nervous system
2) Autonomic nervous system
Somatic system (2)
1) Conscious control
2) Controls movements of skeletal muscles, skin and joints
Autonomic nervous system
1) Involuntary control
2) Control glands and smooth muscles of internal organs
Autonomic system subdivions (2)
1) Sympathetic nervous system
2) Parasympathetic nervous system
Sympathetic nervous system
Prepares body for vigorous muscular activity, stress and emergencies
Parasympathetic system
Operates during normal situations, permits digestion and conserves energy
Nervous System graph
Neurons
Nerve cells that conduct electrical impulses and relay information throughout the body
Three basic parts of neuron (3)
1) Dendrites
2) Cell body
3) Axon (which end in axon terminals)
Unique features of neuron structure
Do neurons undergo mitosis (cell division)?
Can neurons be replaced?
How long can neurons survive without oxygen?
No, neurons can survive a person’s entire lifetime
Neurons cannot be replaced, which is why brain and spinal cord damage is so serious
Just minutes
Neuron cell body (3)
1) Receives information from dendrites
2) Synthesizes all nerve cell products
3) Sends information toward axon
Features of neuron cell body (4)
1) Large nucleus
2) Cytoplasm
3) Contain all normal organelles except centrioles (responsible for mitosis, no cell division)
4) Main function is to manufacture neurotransmitters
Dendrites (3) - IN
1) Receiving end of neuron
2) Numerous short extensions that emanate from cell body
2) Conduct nerve impulses TOWARD the cell body
Axon (5) - OUT
1) Conducts nerve impulses AWAY from the cell body to axon terminals
2) Composed of cell components but lack rough ER
3) Depend on neuron’s cell body to send necessary proteins down length of axon
4) Terminates in axon terminals
5) Vary in length
Axon terminals (2)
1) Store neurotransmitters inside secretory vesicles at end of axon terminals
2) When neurotransmitters released from axon terminal vesicles, they carry nerve impulse from one neuron to next
Neurotransmitters
Chemical messengers to communicate between neurons across a synapse
Synapse (2)
1) Minute, fluid-filled gap between two neurons (neurons do not physically touch each other)
2) Neurotransmitters sent from presynaptic neuron (in the sending axon terminal) to a postsynaptic neuron (receptors on the dendrite)
Neuron shape - Multipolar neurons (3)
1) Three or more extensions from cell body
2) One axon and many dendrites
3) Motor neurons (efferent)
Neuron shape - Bipolar neurons (2)
1) Central body with two extensions (dendrite and an axon)
2) Found in visual and olfactory systems
Neuron shape - Unipolar neurons (4)
1) One extension off cell body that branches into two branches
2) Branch 1: Central process to CNS
3) Branch 2: Peripheral process from sensory receptor
4) Typically sensory neurons in PNS
Sensory neuron (afferent) function (3)
1) Unipolar
2) Carry information from peripheral nervous system to CNS
3) Skin or internal organs to CNS
Interneurons (association neurons) function (3)
1) Found only in CNS
2) Typically multipolar
3) Transmit impulses within different parts of CNS
Motor neurons (efferent) function (2)
1) Multipolar neurons
2) Send messages from CNS to peripheral nervous system
Neuroglial cells
Support cells for neurons
PNS neuroglial cells - Schwann cells (3)
1) Composed of fatty myelin sheath
2) Protects and insulates nerve axon
3) Increases speed of nerve impulses
Nodes of Ranvier (Schwann Cells) (2)
1) Gaps between Schwann Cells
2) Enables saltatory conduction (jumping from one node to next - much faster)
Axonal regeneration
Process of axons regrowing after PNS nerve axon is injured or severed. Schwann cells grow ahead of axon to facilitate growth. Growth is slow.
CNS neuroglial cells - Ependymal cells (2)
1) Circulate cerebrospinal fluid (CSF)
2) Allow fluid exchange between brain, spinal cord and CSF
Cerebralspinal Fluid (CSF) (2)
1) Very specialized clear fluid only found in brain and spinal cord
2) Protect brain and spinal cord and allows brain to float so it doesn’t hit skull
Ventricle of brain
Spaces of brain where CSF is made
CNS neuroglial cells - Oligodendrocytes
Insulation for CNS axons
CNS neuroglial cells - Astrocytes (3)
1) Control chemical environment of neurons
2) Wrap around the blood capillaries
3) Blood brain barrier
a) Physical barrier
b) Allows passage of only certain substances into the CNS
CNS neuroglial cells - Microglial cells (2)
1) Protect the CNS
2) Phagocytosis
a) Dead cells
b) Pathogens
CNS Neuroglial cell picture
Action potential (3)
1) The conduction of electrical impulses by neurons
2) Caused by rapid change in polarity across the membrane
2) Nerve impulse is an electrochemical charge moving along an axon created by the movement of unequally distributed ions on either side of an axon’s plasma membrane.
Sodium-potassium pump (3)
1) Utilizes integral carrier protein to carry ions across plasma membrane
2) For every three Na+ ions pumped out, two K+ ions are pumped in
3) Must be kept in constant operation
Sodium and Potassium gates (4)
1) Enable action potentials
2) Special protein lined channels with gates in the membrane
3) Allow sodium or potassium to pass through
4) Gates are voltage activated and respond to changes in shape
Polarized membrane
At rest, one side of a membrane has a different charge than the other side
Resting potential (2)
1) Resting charge of an axon when not conducting an impulse
2) Equal to -70mV (charge on inside is less than outside)
Depolarization and re-polarization in action potential (2)
1) Depolarization - first membrane potential becomes more positive on inside
2) Re-polarization - return to normal, where inside of axon is negative again
Phases of action potential - electrical propagation (4)
1) Resting potential - sodium and potassium gates are closed. Voltage at -70mV
2) Depolarization - sodium gates open, sodium rushes into axon and voltage moves to zero and then +40mV (higher on inside of membrane)
3) Repolarization - sodium gates close, potassium gates open, allowing potassium to rush out of axon. Returns to negative voltage inside axon
4) Afterpolarization (also called hyperpolarization) - Potassium gates slowly close, voltage returns below -70mV and then returns to -70mV as resting state begins
Action potentials are self-propagating and all-or-nothing. Define (2)
1) Self-propagating - ion channels are prompted to open whenever membrane depolarizes in adjacent area. Signal has to move the entire length of the axon
2) All-or nothing - the action either occurs or not. Intensity of sensation is distinguished by NUMBER of neurons stimulated and FREQUENCY of stimulation of neurons
Electrochemical nature of nerve impulses (2)
1) Electrical - transmission of nerve impulse along axon
2) Chemical - Neurotransmitters transmit signal across synapse
Electrical transmission steps (4)
1) Electrical impulse reaches end of the axon at the axon terminal
2) Calcium ions rush inside cell
3) Causes vesicles filled with neurotransmitters to fuse with plasma membrane
4) Neurotransmitters are released and then bind to the dendrites of the receiving neuron
Synaptic inhibition (2)
1) Short existence of neutrotransmitters in the synapse
2) Prevention of continuous stimulation of postsynaptic neuron
Neurotransmitters - Norepinephrine and epinephrine (3)
1) Function as hormones and neurotransmitters
2) Produced in adrenal glands
3) Into general circulation
Neurotransmitters - dopamine (3)
1) Specialized brain neurotransmitter
2) Regulates emotional responses
3) Regulates muscle tone
Acetylcholine (3)
1) Found in neuromuscular junction (NMJ)
2) Motor neuron synapses on a muscle
3) Coordinates action between nervous and muscular system
Neuromuscular junction (NMJ) (5)
1) Nerve impulse via motor neuron reaches neuromuscular junction (NMJ) (action potential)
2) Acetylcholine released into NMJ and binds to muscle fiber
3) Causes sodium to enter sarcoplasm (cytoplasm of muscle cell) and stimulates sarcolemma
4) Sarcoplasmic reticulum causes calcium Ions to be released into muscle fiber
5) Myosin binds with actin and pulls actin closer together for muscle to contract
Reflexes (2)
1) Nearly instantaneous, automatic, and involuntary motor responses within nervous system
2) Can start from stimuli inside or outside body
Subconscious reflexes (2)
Reflexes that occur without conscious awareness like regulation of blood sugar
Other reflexes like eye blinking and shivering occur and there is awareness afterwards
Reflex arc
The neural pathway that a nerve impulse travels
Dorsal root of a nerve (afferent)
How sensory information travels INTO the spinal cord
Ventral root of a nerve (efferent)
How motor information travels OUT OF the spinal cord
Gray matter of the spinal cord (2)
1) Contains cell bodies of neurons
2) Where neurons synapse with other neurons (such as interneurons)
White matter of the spinal cord (2)
1) Contains axons of neurons
2) White matter surrounds gray matter in spine
Dorsal Root Ganglion (DRG)
Contains cell bodies of sensory neurons
Posterior horn
Where SENSORY neurons synapse on cells within the spinal cord in the gray matter
Anterior horn
Where motor neuron cell bodies are located
Spinal cord anatomy picture
Spinal nerve
Contains both sensory and motor neurons from the ventral and dorsal roots
Spinal reflexes (2)
Reflexes that occur faster than a conscious decision to move coming from the brain to avoid dangerous stimuli
Spinal reflexes involve fewer neurons and only travel to the spinal cord and back
Reflex arc steps (to avoid dangerous stimuli) (5)
1) The receptor at the end of a sensory neuron reacts to stimulus
2) The sensory (afferent) neuron conducts nerve impulses along an afferent pathway toward the CNS
3) The integration center consists of one or more synapses in the CNS
4) A motor (efferent) neuron conducts a nerve impulse along an efferent pathway from the integration center to an effector
5) An effector responds to the efferent impulses by contracting (a muscle) or secreting a product (a gland)
Stretch reflex
Special type of muscle reflex that protects muscles against increases in length that may tear or damage muscle fibers
Muscle spindles
Specialized muscle cells that are constantly monitoring the amount of stretch in a muscle
Patellar reflex (2)
1) Knee-jerk reflex that tests the stretch reflex of the quadriceps femoris muscle
2) Prevents overstretch on the quadriceps
Flexor withdrawal reflex (such as withdrawing from hot object) (3)
1) Excitatory interneurons send excitatory signals to motor neurons
2) Inhibitory interneurons send inhibitory signals that prevent muscular contraction
3) In case of hot object, excitatory interneurons sent to biceps muscle and inhibitory interneurons sent to triceps muscle to allow for quick elbow flexion
