Nervous System Flashcards
(202 cards)
1
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Functions of the Nervous System
A
- Acts as the body’s communicating system and coordinates body activities
- Builds up a background of experience (memory) by recording and relating certain stimuli and responses. This is called learning.
2
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Properties of Neurons:
A
- Can live and function for a long time
- They do not divide- fail to go under mitosis after birth
- High metabolic rate- require abundant oxygen and glucose
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Constitues one of the cells of the nervous tissue and has the property of receiving and transmitting nervous impulse
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Neurons
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any of the filamentous bands of nervous tissue that connect parts of the nervous system with the other organs, conduct nervous impulses, and are made up of axons and dendrites together with protective and supportive structures
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Nerves
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Soma or cell body parts
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Nissl bodies, Golgi Apparatus, Microfilament/Neurotubules and Mitochondria
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discrete granular bodies of variable size that are seen in the soma and the dendrites, but not in the axon, and are composed of RNA and used for protein synthesis
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Nissl bodies
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important in packaging peptides and proteins (including neurotransmitters) into vesicles.
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Golgi Apparatus
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system of transport for materials within a neuron and may be used for structural support
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Microfilaments or Neurotubules
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small extensions from the cell body that receive information and carry the impulses toward the cell body
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dendrites
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long section, carries impulses away from the body
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axon
11
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Axon is made up of..
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Axon hillock, schwann cell, myeline sheath, nodes of ranvier, neurilemma and axon terminal
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the part of the axon where it emerges from the soma
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axon hillock
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forms the myeline sheath consisting of the inner spiral layers from which the protoplasm has been squeezed out
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schwann cell
14
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fat like layered insulation surrounding the axon interrupted at intervals called ________
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myelin sheath; node of ranvier
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gaps in the insulation
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nodes of ranvier
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sheath of schwann- the plasma membrane surrounding a schwann cell
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neurilemma
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contains neurotransmitters that are released to communicate with target neurons
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Axon terminal
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two processes extending from the cell body; axon and dendrite are on opposite sides
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bipolar neurons
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dendrite and axon emerging from one process
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unipolar cell
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have many processes that extend from the cell body. Each neuron has only one axon
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multipolar neurons
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provide structural integrity and functional support to the nerves
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neuroglia or glial cells
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Functions of the neuroglial
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- Forms Myeline sheath
- Protects neurons via phagocytosis
- Regulates the internal environment of neurons in the CNS
- Helps in the regeneration of the cell
23
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4 types of nerve fibers
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unmyelinated without neurilemma, unmyelinated with neurilemma, myelinated without neurilemma, myelinated with neurilemma
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3 classifications of neurons
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Sensory (afferent), motor (efferent), interneurons
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sends information from sensory receptors TOWARD the CNS
sensory (afferent) neurons
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sends information AWAY from the CNS to muscles or glands
motor (efferent) neurons
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send information BETWEEN sensory neurons and motor neurons. Most are located in the CNS
interneurons
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substance that transmits nerve impulses across a synapse
neurotransmitters
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Actions on other Neurons
Excitatory neurons, inhibitory neurons, modulatory neurons
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Excite their target; neurotransmitter is _____
excitatory neurons; Acetylcholine (ACH)
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Inhibit their target neurons; mostly interneurons; neurotransmitters are ______
inhibitory neurons; GABA and glycine
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evoke more complex effects; neurotransmitters are _________
modulatory neurons; Dopmaine, ACH, Serotonin etc.
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Excitatory neurons....
1. Increase membrane permeability
2. Increases chance for threshold to be achieved
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Inhibitory neurons...
1. Decrease membrane permeability
2. decrease chance for threshold to be achieved
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nerve endings which are specialized for receiving certain stimuli
receptors
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3 receptors
Exteroreceptor, Interoreceptor, Proprioceptor
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Receive sensations of touch, pain, temp., vision, and hearing from sources outside the body
Exteroreceptors
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Receive visual sensations such as hunger, thirst and visceral pain from sources arising inside the body
Interoreceptors
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located in muscles, tendons, and joints, which receive sensations of position, movement, deep pressure and balance
proprioceptors
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structures which carry out the motor activities
effectors
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two types of effectors
somatic and visceral
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effector located in skeletal muscles
somatic effectors
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effector located in smooth muscles, heart, and secretory glands
visceral effectors
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propagated disturbance along a nerve cell. Movement of ___________ along a nerve cell, and is conducted along the axon to its terminal
impulse; action potential
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Speed of an impulse is determined by...
1. diameter of the axon (greater = faster)
2. Myelinated neurons conduct faster than unmyelinated neurons
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Self regenerating wave of electrochemical activity that allows nerve cells to carry a signal over a distance
action potential
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Action potential is also known as ________. (The rapid rising and falling of the action potential form a sharp spike called the_______)
nerve impulses/spikes; spike potential
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Membrane potential in cells are determined by...
1. The concentration of ions on the inside and outside of the cell
2. The permeability of the cell membranes to those ions through specific ion channels
3. The activity of electrogenic pumps that maintain the ion concentrations across the membrane.
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Two ions that contribute to membrane potential
Sodium and Potassium
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How many ions of K and Na get pumped in a neuron?
3 Na to the outside; 2 K to the inside
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What is the reason why there is a higher concentration of sodium on the outside than the inside
Active transport mechanism named the Sodium-Potassium Pump
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That which can evoke or elicit action (response) in a muscle, nerve, or any other excitable tissue, or cause an augmenting action on any function or metabolic processes.
Stimuli
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Stimulus that is strong enough to achieve an action potential
Threshold stimulus
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The minimum intensity of a stimulus needed to achieve an action potential
Threshold intensity
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The potential (voltage) at which action potential is initiated. For excitable membrane, this is ________ than the resting membrane potential
Threshold potential; 15 mv less
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Mechanism of Action Potential
1. When at rest, the cell membrane of the neuron allows certain ions to pass through while preventing/restricting the movement of other ions.
2. The stimulus which could be electric, chemical, or mechanical causes the sodium gates/channels to open.
3. All the positively-charged sodiums rush in causing the membrane to be positive on the inside than the outside
4. The sodium channels briefly open then close
5. Potassium channels then open, and because there is more potassium inside the membrane than the outside, positively-charged potassium ions diffuse out.
6. As these positive potassium ions go out, the inside of the membrane once again becomes negative with respect to the outside and the resting membrane potential is restored.
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The membrane potential is less negative than the resting level
Depolarization
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Return of the membrane to its resting level
Repolarization
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The membrane potential is more negative than the resting level
Hyperpolarization
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Jumping of the impulse from one node of Ranvier to the next
Saltatory Conduction
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Junction between two communicating neurons
The Synapse
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Synaptic transmission
Dendrite -> cell body -> axon -> synapse -> dendrite -> cell body -> axon
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impulse travels from neuron to neuron
nerve pathway
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to complete the signal, a ______ is released at the gap to _______ the next neuron
neurotransmitter; signal
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Neuron approaching the synapse. It send ______________ signals to the postsynaptic neuron.
Presynaptic neuron; electrical or chemical
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Receives the signals from the presynaptic neuron and produces either an _________________ response
postsynaptic neuron; inhibitory or excitatory
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How is an impulse transmitted across a synaptic cleft?
1. Action potential reaches the axon terminal
2. Voltage gated Ca+2 channel opens -> influx of Ca+2
3. Ca signals the release of neurotransmitters
4. Neurotransmitters are released into the synaptic cleft and diffuse to post-synaptic terminals
5. Neurotranmitter binds to receptor in post-synaptic membrane
6. Causes Na+ channels to open if threshold potential is reached
7. An action potential is initiated
8. Neurotransmitter is broken down by specific enzymes in the synaptic cleft
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2 Main neurotransmitters
Acetycholine (Ach) and Noradrenaline
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-released by all motor neurons, activating skeletal muscles
-involved in parasympathetic nervous system (relaxing responses)
Acetycholine (Ach) (Cholinergic synapse)
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- involved in the sympathetic nervous system (fight or flight response)
Noradrenaline (Adrenergic synapse)
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What is under the CNS
Brain and spinal cord
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What is under the PNS
motor neurons and sensory neurons
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what is under motor neurons
somatic and autonomic nervous system
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what is under autonomic nervous system
sympathetic division and parasympathetic division
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receives and posses sensory information, initiates responses, stores memories, generates thoughts and emotions
brain
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conducts signals to and from the brain, controls reflex activities
spinal cord
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CNS to muscles and glands
motor neurons
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Sensory organs to CNS
sensory neurons
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Controls voluntary movements
somatic nervous system
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Controls involuntary movements
autonomic nervous system
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fight or flight response
sympathetic division
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rest or digest
parasympathetic division
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Considered the voluntary part of the nervous system
Central Nervous System
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Coverings:
3 Meninges (Dura Mater, Arachnoid, Pia Mater) - covers brain and spinal cord
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Hard mother - outer covering
Dura Mater
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3 sublayers of the Dura mater
Periosteum, Meningeal dura and venous sinuses
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superficial part or the inner covering of the bone
periosteum
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covers the brain
meningeal dura
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blood spaces enclosed between the periosteum and the meningeal dura
venous sinuses
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separated from the dura by the subdural space
arachnoid
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2 sublayers of the arachnoid
subarachnoid and trabeculae
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space under the arachnoid
subarachnoid
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branching delicate filament of the arachnoid
trabeculae
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innermost layer of the meninges; a delicate, transparent tissue which closely follows the contours of the brain
pia mater (tender mother)
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Spaces in the brain
ventricles; filled with CFS (cerebrospinal fluid)
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connected to each other by the interventicular foramen
2 lateral ventricles
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opens into the cerebral aqueduct
3rd ventricle
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with 3 openings, 1 median _________ and 2 lateral foramina, ____________
4th ventricle; foramen of magendie; foramen of luschka
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tiny blood capillaries located in the walls of the ventricles, forms the CSF. They are lined by ependymal cells.
Choroid plexus
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ultra filtrate of plasma that surrounds the brain and spinal cord
CSF Cerebrospinal Fluid
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Functions of the Cerebrospinal Fluid:
1. Acts as a cushion and shock absorber of the brain and spinal cord and make it buoyant.
2. Delivers nutrients to the brain and removes waste
3. Maintains the stability of the extra- and intra- cellular environment by creating the proper concentrations of the chemical needed for synaptic transmission.
4. To flow between the cranium and the spine and compensate for the changes in intracranial volume.
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Drainage of the CSF
Subarachnoid cisterns and Central Spinal Canal
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bathes the brain between the arachnoid and pia mater
subarachnoid cisterns
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bathes the spinal cord
central spinal canal
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abnormal collection of CSF within the ventricles causing raised intracranial pressure
Hydrocephalus
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A cylindrical mass of ____________ about ________. In length which occupies 2/3 of the vertebral canal.
spinal cord- nervous tissue; 40-45 cm
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a thin extension of the pia mater which anchors the spinal cord and attaches to the coccyx
filum terimnale
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Spinal Nerves: composed of __ segments each bearing one pair of spinal nerves-
___ cervical pairs
___ thoracic
___ lumbar
___ sacral
___ coccygeal
31; 8; 12; 5; 5; 1
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an opening between 2 vertebrae where the spinal nerve passes through
intervertebral foramen
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large bundle composed of roots of all the spinal nerves below the 1st lumbar pair
cauda equina
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contain afferent nerve cells
dorsal root ganglia
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contains efferent nerve fibers with cell bodies in the cord
ventral root
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dorsal and ventral branches formed the spinal nerve and distributed to the ventral and dorsal areas of the body
ramus
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where neural cell bodies, axon terminals, and dendrites, as well as all nerve synapses are found
gray matter (a type of brain tissue)
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gray matter is abundant where
cerebellum, cerebrum and brain stem
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seen in the brain and spinal cord and is composed of bundles of axons
white matter (a type of axon)
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White matter is coated with _______, a mixture of _________, that helps conduct nerve signals and protect the axons
myelin; proteins and lipids
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Nerve cell cluster or a group of nerve cell bodies located in the autonomic nervous system and sensory system.
Ganglion
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Functions of the Spinal Cord:
1. It serves as a reflex center
2. It serves as a pathway for conducting impulses wither to or from the brain and spinal cord
3. Keeps the condition inside the body constant by reacting to a change in the environment in a way that maintains homeostasis.
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involuntary reactions in response to a stimuli
reflexes
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______ carry the message from the stimulated receptors to the correct effectors.
Nerve cells (neurons)
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Reflex pathway
1. A sensory neuron carries the message from the receptor to the CNS
2. A motor neuron carries the message from the CNS to the effector
CALLED A REFLEX ARC
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bundles of nerve fibers carrying sensory impulses up the cord and into the brain which interpret them accordingly
ascending tracts
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conducts efferent or motor impulses to the skeletal muscles
descending tracts
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Spinal tracts
posterior tracts, spinothalamic tracts, corticospinal tracts
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convey information from the skin about pressure, touch, and pain. They also help us position our body and space, so we can move according to our surroundings
posterior tracts
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conveys information about the bodys temperature and level of pain
spinothalamic tracts
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sends signals from the brain to the spinal cord to the skeletal muscles for movement
corticospinal tracts
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a complicated network of nerve fibers from the anterior remus before they go directly to the skin or muscles
plexuses
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4 types of plexus
Cervical, brachial, lumbar and sacral
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supplies muscles and skin of the neck and posterior part of the scalp; anterior rami of the 1st four cervical nerves C1-4
cervical plexus
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C3, 4 & 5 - supplies motor fibers to the diaphragm, an important muscle for respiration
phrenic nerve
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supplies th eneck and shoulder muscles and the entire upper body extremity
brachial plexus
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Nerves under the brachial plexus
Musculocutaneuos nerve (biceps brachii)
Axilliary nerve (deltoid)
Median nerve (most flexors in the forearm)
Radial Nerve (most extensors of arm and forearm
Ulnar nerve (medial portion of the arm)
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T12 and 1st 4 lumbar spinal nerves L1,2,3 & 4
Lumbar plexus
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adductors of the hip
obturator nerve
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quadriceps group of muscles
femoral nerve
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complex network of nerves located in the abdomen, behind the stomach and at the level of L1
coeliac or solar plexus
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anterior ram of L4 &L5 and the 1st 3 sacral spines S1-3
sacral plexus
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longest and largest nerve in the PNS; innervates flexors of the knee and foot
sciatic nerve
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What is under the brain
forebrain, midbrain and hindbrain
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what is under the forebrain
telencephalon and diencephalon
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what is under the midbrain
mesencephalon
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what is under the hindbrain
metencephalon and mylencephalon
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what is under the mylencephalon
medulla
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contains the vital centers - heart activity, blood pressure, respiratory movements
-originates just above the ____ cervical spinal nerve
-Forms the floor of the ____ ventricle
-Contains cells of origins of the _____ cranial nerves
medulla; 1st; 4th; 9-12
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What is under the metencephalon
pons and cerebellum
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Lies ventral to the cerebellum; acts as a bridge between the medulla and the cerebral peduncles; consists of myelinated fiber tracts, both ascending and descending
-Contains cells of origin of the _____ cranial nerves
pons; 5-8
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second largest part of the brain
cerebellum
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the cerebellum as __ lateral hemispheres and a central portion (____)
2; vermis
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the cerebellum is separated from the cerebrum by a fold of.....
dura mater (tentorium cerebelli)
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the cerebellum is composed of
inner white matter (arbor vitae) and outer gray matter
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______ connect the cerebellum, with other parts pf the brain
penduncles
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Functions of the cerebellum
1. Fine coordination of the prime movers, synergists and antagonists in skeletal muscles
2. Plays an important role in the maintenance of balance and equilibrium since it receives afferent impulses from the ear
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involved in sleep, consciousness, vision, hearing and temperature regulation and motor functions
mesencephalon
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2 rope-like masses of white matter which pass through carrying impulses to and from the cerebrum
cerebral peduncles
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4 small rounded elevations
corpora quadrigemina (tectum)
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relay visual impulses
superior colliculi (hills)
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relay auditory impulses
inferior colliculi
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located between the cerebrum and midbrain
diencephalon
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All afferent impulses going to the cerebrum are relayed through cell bodies in here; plays a major role in regulating arousal, level os consciousness and levels of activity
- forms the lateral wall of the ___ ventricle
-composed of ___ lateral masses of _____
thalamus; 3rd; 2; gray matter
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anterior part of this area contains the _________, the crossing of the optic nerve
- forms the floor and part of the lateral walls of the ____ ventricle
hypothalamus; optic chiasma;3rd
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functions of the thalamus
1. Regulates the release of hormones by the pituitary gland
2. Controls body temperature by shivering and sweating
3. Involved in the expression of emotions
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largest part of the brain
telencephalon (cerebrum)
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divides the cerebrum into left ad right hemisphere
longitudinal fissure
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joind the hemisphere in the inferior surface
corpus callosum
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outer surface composed of a layer of grey matter with sulci and gyri
cerebral cortex
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outer surface composed of a layer of grey matter with sulci and gyri
cerebral cortex
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cerebral cortex- contains most of the brains neuronal cell bodies
gray matter
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cerebral cortex- long axon tracts
white matter
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connect cerebrum with lower parts of the nervous system
projection fibers
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connect neurons from different parts in the same hemisphere
association fibers
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cross from one hemisphere to the other
commisural fibers
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main functions of cerebral cortex
sensory mechanism and association functions, voluntary muscle movement and basal ganglia
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special senses
sensory mechanism
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learning, memory, judgement, emotional states
association functions
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occupies the anterior central gyrus in each hemisphere where each section of this area is specific for certain region of the body
primary motor area
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main motor pathways from both hemispheres down to the spinal cord
pyramidal tracts
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- do not pass through the pyramids of the medulla
- they synapse with motor cells in various parts of the brain below the cortex
- facilitates or inhibits the motor impulses from the primary motor area
extrapyramidal tracts
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scattered areas of grey matter embedded in white matter
basal ganglia
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functions of the basal ganglia
-control voluntary motor movements
-procedural learning
-routine behaviors or habits
- eye movements
-cognition and emotion
-inhibits excitation of muscles to prevent overreaction
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neurological conditions associated with basal ganglia dysfunction
tourette syndrome, movement disorders- parkinson's disease, huntington's disease, hemiballismus
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characterized by multiple physical tics and at least one vocal tic
tourette syndrome
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caused by a decrease or absence of dopamine which controls body movement and coordination
parkinsons disease
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uncoordinated, jerky body movements become more apparent, along with a decline in mental abilities and behavioral and psychiatric problems
huntingtons disease
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involuntary flinging motions of the extremity
hemiballismus
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collection of structures from the forebrain and the midbrain that lies on both sides of the thalamus, right under the cerebrum
limbic system
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function of limbic system
controls emotion, behaviour, motivation and long term memory
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controls involuntary responses
visceral motor system
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target organs of autonomic nervous system
glands that form secretion, organs that contain smooth muscles, cardiac muscles of the heart
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bodys emergency mechanism
fight or flight
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extension of the brain and is located in the bony orbits for protection
the eye
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located in the upper outer corner of each eyeball, secreting tears
lacrimal glands
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lacrimal glands functions
1. Keeps the surface moist
2. Washes away foreign particles
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outer coat composed of tough, white, fibrous connective tissue; does not contain blood vessels, but have sensory nerve endings for pain
sclera
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transparent layer on the anterior surface so that light can enter the eye. No blood vessels here are present
cornea
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middle coat, contains many blood vessels
choroid
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forms a circular area around the anterior portion and consists of smooth muscles
ciliary body
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extend to hold the lens of the eye in place
suspensory ligaments
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colored part of the eye
iris
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a groove or recess where the aqueous humor drains and enters the blood
canal of sclemm
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inner layer without a complete coat having no anterior portion; is continuous with the optic nerve
retina
