Chapter 13: Nervous System Flashcards
What are the 2 main divisions of the Nervous System?
- Central Nervous System
- Peripheral Nervous System
What structures are located in the Central Nervous System?
- brain
- spinal cord
What structures are located in the Peripheral Nervous System?
- nerves that come off of the CNS
- innervate rest of the body
What are the functions of the Nervous System?
- sensory
- Integrating
- motor
What is the Sensory function of the Nervous System?
Sense changes within or outside the body and sends it to the spinal cord and brain
What is the Integrating function of the Nervous System?
-brain and spinal cord receive, store and integrate the information to produce a response
What is the Motor Function of the Nervous System?
Instruction of the body to do something
What are Neurons?
- basic functional units of the Nervous System
- have a high requirement for Oxygen
- cant reproduce
- can regenerate, but cell body has to be intact
What are Neuroglia?
- glial cells, not neurons
- provide structural and functional support
- provides protection to neurons
What is the Soma/Perikaryon?
Central cell body
What are the 2 cell processes found in the Nervous System?
- dendrites
- axons
What are Dendrites?
- receive stimuli/impulses from other neurons and transmit information TO soma
- can be sensory receptors
- short and branched
What are Axons?
- conduct nerve impulses AWAY from soma, towards another neuron or an effector cell (muscle, gland)
- long,single process
What is Myelin?
Fatty/protein substance that covers axons
What is White Matter?
Nervous tissue containing myelinated axons
What is a Myelin Sheath?
Cell membrane of glial cells tightly wrapped around axon
Where are Oligodendrocytes located?
- brain
- spinal cord
Where are Schwann Cells located?
Nerves outside brain and spinal cord
What are Nodes of Ranvier?
- gaps in the myelin sheath between adjacent glial cells
- works with myelin sheaths to enhance the speed of conduction of nerve impulses along the axon
What is the PNS?
-extends outward from the central axis toward the periphery of the body
Where do Cranial Nerves originate?
Directly from the brain
Where do Spinal Nerves originate?
Spinal cord
What are Afferent Nerves?
- conduct impulses TOWARD CNS
- AKA: sensory nerves
- conduct sensations from sensory receptors in skin and other locations in the CNS
What are Efferent Nerves?
- conduct impulses AWAY from CNS
- AKA: motor nerves
- cause skeletal contraction/movement
What is the Somatic Nervous System?
- actions under CONSCIOUS or voluntary control
- motor nerves lead skeletal muscle and cause limb or body movement
- EX: turning your head when your name is called
What is the Autonomic Nervous System?
- motor nerves lead to smooth muscle, cardiac muscle and glands
- EX:slowing of the heart rate in response to an increased blood pressure
What is Sympathetic Division?
Fight or flight
What is Parasympathetic Division?
Feed or breed
What is the Resting Rate?
- when neuron is not stimulated
- still working to maintain a resting state (Na/K pump)
What is Resting Membrane Potential?
- difference in electrical charge across neuronal membrane
- due to differences in distribution of positive and negative charges from sodium, potassium, proteins and other charged ions on either side of the neuronal membrane
What is the Resting Membrane Potential number?
-70mV
What is the function of the Na/K pump?
Maintains a negatively charged resting membrane potential
What is the Na/K pump?
-Specialized molecules located in the neuron’s cell membrane that maintains cell resting state
What does the Na/K pump pump out of the neuron?
3(Na+)
What does the Na/K pump pump into the neuron?
2(K+)
What are the steps in Depolarization?
- neuron receives external stimulus
- Na+ channel opens on cell membrane
- Na+ flow into cell by passive diffusion
- down concentration gradient
- inside of neuron goes from NEGATIVE to POSITIVE due to inflow of Na+ ions
What is Action Potential?
Significant change in electrical charge
What are the steps in Repolarization?
- Na+ channels close
- K+ channels open
- K+ diffuses out of cell
- resting potential (charge) is restored
- cell is repolarized
What happens after Repolarization?
- Na+/K+ pump moves ions back to their original state
- resting state is restored
What is the “All or Nothing” principle?
Neuron depolarizes to its maximum strength or not at all
What is the Wave of Depolarization?
Strong stimuli cause numerous sodium channels to open
What is Conduction of the Action Principle?
Spreading wave of opening Na+ channels in sufficient numbers to allow sodium influx and depolarization
What is the Refractory Period?
- time period when sensitivity of neuron is reduced
- cell is still in depolarization/early repolarization
What is the Absolute Refractory Period?
- during Na+ influx and early K+ outflow
- no amount of stimulus can cause depolarization
What is the Relative Refractory Period?
- during end of repolarization period
- strong stimulus can cause depolarization
What is Saltatory Conduction?
-rapid means of conducting an action potential
Where is the only place that depolarization of myelinated axons can take place?
Nodes of Ranvier
What prevents sodium from entering the cell?
Myelin sheath
What are Local Anesthetics?
- work by blocking the propagation of the action potential
- blocks Na channels
- sodium can’t flow into the cell, so threshold is not achieved
- EX:lidocaine
What is a Synapse?
-junction between 2 neurons of a neuron and a target cell
What is a Synaptic Cleft?
-gap between adjacent neurons/effector cells
What is a Presynaptic Neuron?
- Neuron bringing the depolarization wave to the synapse
- releases neurotransmitter
What is the Postsynaptic Neuron?
Contains receptors for the neurotransmitter
Where does the axon of a Presynaptic neuron end?
- as a branched structure
- telodendron
What is a Terminal Bouton?
Slightly enlarged bulb at end of axon
What happens when the depolarization wave reaches the axon terminal?
Calcium channels open and cause vesicles to fuse with cellular membrane and release neurotransmitter into the synapse
Where do Neurotransmitters diffuse?
- Across synaptic cleft towards Postsynaptic membrane
- receptors on Postsynaptic membrane bind Neurotransmitters
- receptors are very specific for each neurotransmitter
What is Excitatory Neurotransmitters?
- Usually cause an influx of Na+
- Postsynaptic membrane moves towards threshold (more positive)
What are Inhibitory Neurotransmitters?
- move the charge of Postsynaptic cell farther away from threshold (more negative)
- may open K+ channels/Cl- channels
What is Acetylcholine?
Can be excitatory or inhibitory depending on location in the body
What are Catecholamines?
- can be excitatory or inhibitory depending on location
- epinephrine associated with fight or flight reactions
What is GABA?
Inhibitory transmitter in the brain
What is Glycine?
Inhibitory neurotransmitter in the spinal cord
What is Acetylcholinesterase?
- Found on Postsynaptic membrane
- breaks down acetylcholine
What is Monoamine Oxidase (MAO)?
Breaks down norepinephrine
What is Catechol-O-methyl Transferase (COMT)?
Breaks down norepinephrine that is not reabsorbed
What are the structures in the Central Nervous System?
- brain
- cerebrum
- cerebellum
- diencephalon
- brain stem
- spinal cord
What is the Cerebrum?
- gray matter
- white matter
- area of brain responsible for higher-order behaviors (learning, intelligence, awareness, etc…)
What is Gray Matter?
- cerebral cortex
- outer layer of brain
What is White Matter?
-fibers beneath cortex and corpus callosum (fibers that connect the 2 halves of the cerebral cortex)
What are Gyri (Gyrus)?
Folds (rises) in cerebral hemisphere
What are Sulci (Sulcus)?
- shallow grooves
- divides cerebral hemispheres into lobes
What are Fissures?
Deep grooves separating the Gyri
-longitudinal fissures: prominent groove that divides the cerebrum into right and left cerebral hemisphere
What is the Cerebellum?
- located just caudal to the cerebrum
- area responsible for coordinated movement, balance, posture and complex reflexes
What is Diencephalon?
-passageway between brain stem and cerebrum
What structures are associated with the Diencephalon?
- thalamus
- hypothalamus
- pituitary gland
What is the Brain Stem?
- Connection between brain and spinal cord
- area of brain responsible for basic (conscious, autonomic) functions of the body
What structures are associated with the Brain Stem?
- medulla oblongata
- pons
- midbrain
What functions of the body is the Brain Stem responsible for?
- heart rate
- breathing, coughing, sneezing
- blood pressure
Where do many of the Cranial Nerves originate from?
Brain stem
What is the Meninges?
-connective tissue layer that surrounds the brain and spinal cord
-contains blood vessels, fluid and fat
-supply nutrients and oxygen to the superficial tissues of the
brain and spinal cord
-provides some cushioning and distribution of nutrients for CNS
What are the 3 layers of the Meninges?
- dura mater
- arachnoid
- pia mater
What is the Dura Mater layer of the Meninges?
Tough, fibrous
What is the Arachnoid layer of the Meninges?
Delicate, spider-web like
What is the Pia Mater layer of the Meninges?
- very thin
- lies directly on surface of brain and spinal cord
What is Cerebrospinal Fluid?
- fluid between arachnoid and Pia mater and in canals and ventricles inside brain and central canal of spinal cord
- provides cushioning functions
- regulation of autonomic functions such as respiration and vomiting
What is the Blood Brain Barrier?
- separates the capillaries in the brain from the nervous tissue
- prevents many drugs,proteins,ions and other molecules from readily passing from blood into brain
What are Cranial Nerves?
12 nerve pairs in PNS that originate directly from brain
What are the parts of the Spinal Cord?
- medulla
- central canal
- cortex
- dorsal and ventral roots
What is the Medulla part of the Spinal Cord?
- central part of spinal cord
- composed of gray mater
- a lot of nerve processing occurs here
What is the Central Canal part of the spinal cord?
Center of medulla
What is the Cortex part of the spinal cord?
- outer part of spinal cord
- consists of white matter
- contains myelinated and unmyelinated nerve fibers
- surrounds gray matter
What are the Dorsal and Ventral Nerves?
Emerge as spinal nerves from between each pair of adjacent vertebrae
- dorsal:sensory
- ventral: motor
What is the function of the Autonomic Nervous System?
- controls autonomic functions at subconscious level
- sympathetic
- parasympathetic
What are they Sympathetic part of the Autonomic Nervous System?
- Nerves emerge from thoracic and lumbar vertebrae regions
- thoracolumbar system
What is the Parasympathetic part of the Autonomic Nervous System?
- nerves that emerge from the brain and sacrum
- cranial sacral
What are Adrenergic Neurons?
Neurons that release norepinephrine
What is a1?
- Adrenergic receptors
- cause vasoconstriction of skin,GI tract and kidney
What is B1?
- Adrenergic receptors
- increase heart rate and force of contraction
What is B2?
- Adrenergic receptors
- cause bronchodilation (relaxation)
What is the 1* neurotransmitter for the Sympathetic Nervous System?
Norepinephrine
What is the 1* neurotransmitter for the Parasympathetic Nervous System?
Acetylcholine
What are Cholinergic Neurons?
- release acetylcholine
- 2 types:
- Nicotinic receptors
- Muscarinic receptors
What are Somatic Reflexes?
Involve contraction of skeletal muscles
What are Autonomic Reflexes?
Regulates smooth muscle, cardiac muscle and endocrine glands
What are Contralateral Reflexes?
Starts on one side of the body and travels to the opposite side
What are Ipsilateral Reflexes?
Stimulus and response are on same side of the body
What are the 5 components of the Reflex Arc?
- sensory receptor: activated by stimulus
- sensory neuron:transports AP to gray mater of spinal cord or brain stem and synapses with other neurons
- interneuron:sensory info integrated with info from other sensory neurons
- motor neuron:response is sent out via motor neuron
- target organ:effector cell
What are Withdrawal Reflexes?
- “flexor reflex”
- several interneuron synapses
- results in:
- contraction of muscles
- inhibition of antagonist
