AnP Chapter 11 CNS (LO7) Flashcards
(197 cards)
1
Q
nervous system overview
A
constantly receives signals about changes within the body as well the external environment
Processes info and decides what action is needed
Sends electrical and chemical signals to the cells telling them how to respond
consisting of the brain, spinal cord and nerves
most complex body system
2
Q
Endocrine system
A
employs chemical messengers (hormones) to communicate with cells
3
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Nervous system
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uses electrical signals to transmit messages at lighting speed
4
Q
3 essential roles of the nervous system and how they work
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- Sensing
Nervous system uses sense organs and nerve endings to detect changes both inside and outside
2.Integrating
Nervous system processes info received, relate it to past experiences, determines appropriate response
3.Responding
Nervous system issues commands to muscles and glands to initiate changes based on it’s info
5
Q
Two main divisions of the nervous system
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central nervous system (CNS) and peripheral nervous system (PNS)
6
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Central nervous system
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consists of the brain and spinal cord
7
Q
Peripheral nervous system
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consists of the vast network of nerves throughout the body
8
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Neurobiology
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study of the nervous system
9
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Subdivisions of peripheral nervous system
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Sensory (afferent) division
Motor (efferent) division
10
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Sensory (afferent) division:
A
carries signals from nerve endings to CNS
11
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Sensory (afferent) subdivisions
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Somatic sensory
Visceral sensory
12
Q
Somatic sensory
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carries signals from bones, skin, joints and muscles
13
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Visceral sensory
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carries signals from viscera of heart, lungs, stomach and bladder
14
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Motor (efferent) division:
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transmits impulses from the CNS out to the peripheral organs to cause an effect or action
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Motor (efferent) subdivisions
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Somatic motor
Autonomic motor
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Somatic motor
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allows voluntary movements of skeletal muscles
17
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Autonomic motor
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provides ‘automatic’ activities such as control of blood pressure and heart rate
18
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Sympathetic division
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arouses the body for action
19
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Parasympathetic division
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has a calming effect
20
Q
2 types of cells a make up the nervous system
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neurons (impulse conducting cells)
neuroglia (protect neurons)
21
Q
neuralgia
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also called glial cells
Supportive cells of nervous system
Bind neurons together
Perform various functions that enhance performance
50 glial cells per neuron
22
Q
5 types of glial cells
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Neuroglial of CNS : Oligodendrocyte Ependyma Microglia Astrocytes
Neurons of PNS:
Schwann cells
23
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Oligodendrocytes
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form myelin sheath in the brain and spinal cord; speed signal conduction
24
Q
Ependymal cells
A
line spinal cord and cavities of the brain; some secrete cerebrospinal fluid, whereas other have cilia that aid fluid circulation
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Microglia
perform phagocytosis, engulfing microorganisms and cellular debris
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Astrocytes
extend through brain tissue, nourish neurons; help form blood-brain barrier; attach neurons to blood vessels; provide structural support
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Schwann cells
form myelin sheath around nerves in PNS; form neurilemma
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Glial cell tumours
highly malignant grows rapidly; most adult brain tumors consist of
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Blood-brain barrier
semipermeable membrane that exists throughout the brain that protects the brain of foreign substances
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NEURONS
Nerve cells that handle the nervous system’s role of communication
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3 classes of neurons
Sensory (afferent)
Interneurons
Motor (efferent) neurons
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Sensory (afferent) neurons
Detect stimuli (touch, pressure, heat, cold or chemicals) and transmits about the stimuli to CNS
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Interneurons
Found only in CNS
Connect incoming sensory pathways with outgoing motor pathways
Receives, process and stores info
Make each of us unique in how we think, feel and act
About 90% of body’s neurons
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Motor (efferent) neurons
Rely messages from brain to muscle or gland cells
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how do neurone vary
Vary greatly in shape and size
Vary according to type, number and length of projections
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Multipolar neurons
Have one axon and multiple dendrites
Most common type of neuron and includes most neurons of brain and spinal cord
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Bipolar neuron
Have two processes: an axon and a dendrite with cell body in between the two processes
Can be found in the retina of the eye and olfactory nerve in nose
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Unipolar neurons
Have once process: an axon that extends from the cell body before branching into T shape
Mostly in sensory nerves of PNS
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NEURON STRUCTURE
3 basic parts: body and two extensions ( axon and dendrite)
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Cell body (soma)
is the control center of the neuron and contains the nucleus
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Dendrites
receives signals from other neurons and conduct the info to the cell body
Some neurons only have one dendrite some have thousands
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Axon
carries nerve signals away from the cell body
Nerve cells only have one axon
Longer than dendrites can range from a few millimeters to a meter
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Myelin sheath
encases axons; acts to insulate the axon
Consists mostly of lipid
In PNS schwann cells form myelin sheath
In CNS oligodendrocytes form myelin sheath
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Nodes of Ranvier
evenly spaced gaps in myelin sheath
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Synaptic knob
the end of the axon branch
Vesicles containing a Neurotransmitter are found within
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MYELIN
Helps speed impulse conduction
Not all nerve fibers are myelinated
Unmyelinated nerve fibers perform functions in which speed isn’t essential ex stimulating stomach acid
Myelinated nerve fibers perform functions where speed is important ex stimulating skeletal muscles
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Myelin in PNS
Formed when schwann cells wrap themselves around axon
Lays multiple layers of cell membrane, myelin sheath formed inside these layers
Nucleus and cytoplasm of schwann cells are located in the outermost layer
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Neurilemma
outer layer of schwann cell
Essential for an injured nerve to regenerate
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Myelin in CNS
Formed by one oligodendrocyte creating myelin sheath for several axons
Nucleus of cell located away from myelin sheath
Outward projections from cell wrap around nearby axons meaning no neurilemma
No neurilemma means CNS neurons cant regenerate ex paralysis from a severed spinal cord is permanent
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Nerves in PNS can regenerate or not regenerate?
can regenerate as long as the soma and neurilemma are intact
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Nerves in CNS can regenerate or not regenerate?
cannot regenerate because lacks neurilemma
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Axon Hillock
area where the cell body and axon join
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Axon Collateral
side branches off of the axon, usually at right angles of the axon
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Axon Terminals
the end of the axon and axon collateral processes, just before the portion where the neurotransmistters are released
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Synaptic End Bulbs
bulb-shaped structures at the end of axon terminals, contain synaptic vesicles
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Axolemma
plasma membrane surrounding the axon
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IMPUSLE CONDUCTION
Nerves must initiate and transmit signals at lightning speed to relay messages to organs and tissue
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Signal transmission
occurs through electrical current which results from flow of charged particles from one point to another
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Membrane potential
when ions with opposite charges are separated by a membrane the potential exists for them to move toward one another
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Polarized
a membrane that exhibits membrane potential an excess of positive ions on one side and an excess of negative ions on the other side
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define Resting potential
state of being inactive and polarized, the neuron is resting but it has the potential to react if a stimulus comes along
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how does Resting potential work
When a neuron is not conducting an electrical signal its interior has a negative electrical charge whereas the charge on the outside is positive
Outside of cell rich with sodium ions inside potassium ions
Interior of cell contains large negatively charged proteins and nucleic acids giving cells interior overall negative charge
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how does Depolarization work
Stimulus (chemicals, heat or mechanical pressure) causes sodium ions to enter the cells
Addition of positive ions changes interior from negative to positive
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define depolarization
membrane becomes more positive
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define Action potential
neuron has become active as it conducts an impulse along the axon
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how does action potential work
If depolarization is strong enough adjacent channels open allowing even more sodium ions to flood cells interior
Action potential continues down the axon as one segment stimulates the segment next to it
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how does Repolarization work
Influx of Na+ opens channels to allow K+ to flow out cell
Once k+ has left cell Na+ channels shut to prevent more Na+ from flowing to cell
This repolarizes the cells, interior has negative charge exterior has positive charge
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how does Refectory period work
Membrane polarized but Na+ and K+ are on wrong sides and neuron won’t respond to a new stimulus
Sodium potassium pump works to return Na+ to the outside and K+ to inside
When this is complete nerve is polarized and in resting potential until it receives another stimulus
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what happens if stimulus doesn't;t reach threshold
Action potential is all or nothing
when stimulus reaches a threshold and depolarizes the neuron it fires at it’s maximum voltage
if it doesn’t reach threshold the neuron doesn’t fire at all
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Impulse conduction in Myelinated Fibers
Nerve impulses move through unmyelinated fibers
Thick layer of myelin encasing the axons blocks the free movement of ions across cell membrane
Ion exchange can only occur at the nodes of Ranvier
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How a Nerve Impulse Travels Down a Myelinated Fiber
Action potential created at nodes of Ranvier by electrical changes
Current flows under myelin sheath to next node and triggers another action potential
Process continues down the axon
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Saltatory conduction
Impulses “leap” from node to node because action potentials on occur at the nodes
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Synapse
space between the junction of two neurons in a neutral pathway
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Electrical synapses
(between cardiac muscle cells and certain types of smooth tissue cells)
adjacent neurons touch allowing action potential to pass from one neuron to next
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Chemical synapses
more common
the two neurons don’t touch instead a neurotransmitter (chemical) bridges a gap (synaptic cleft) to carry the message from the presynaptic neuron (first neuron) to the postsynaptic neuron
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5 steps of how synapses work
1. When an action potential reaches a synaptic knob the membrane depolarizes
- -this causes ion channels to open which allows calcium ions to enter the cell
2. The infusion of calcium causes the vesicle to fuse with the plasma membrane and then release their store of a neurotransmitter into the synapse
3. Once release the neurotransmitter binds to receptors on the postsynaptic membrane
- -Each new transmitter has a specific receptor
4. The specific neurotransmitter determines whether the impulse continues called excitation or whether it is stopped called inhabitation
- -If the neurotransmitter is excitatory Na+ channels open the membrane becomes depolarized and the impulse continues
- --If the impulse in the inhibitory K+ channels open and the impulse stops
5. The receptors and then release the neurotransmitter after which is reabsorbed by the synaptic knobs and recycled or destroyed by enzymes
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More than ---- different neurotransmitters in the body
100
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Small molecule neurotransmitters
trigger rapid synaptic actions
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Neuropeptides
modulate slower ongoing synaptic functions
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common neurotransmitters
acetylcholine,
epinephrine/norepinephrine, serotonin,
dopamine
histamine
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Threshold point
The critical level needed to open the sodium (Na+) channels and cause an action potential to follow
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Absolute refractory period
The period of time during which the cell cannot respond again, no matter how strong the stimulus
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Relative refractory period
The period of time during which a cell can only be made to respond with a suprathreshold stimulus
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The spinal cord
is the information passageway that relays messages from the brain to the rest of the body
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Nerves in the cervical region of the spinal cord innervate the...
chest, head, neck, shoulders, arms, hands and diaphragm
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Nerves from the thoracic region extend to the...
intercostal muscles of the rib cage, the abdominal muscles, and the back muscles
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The lumbar spine nerves innervate the...
lower abdominal wall and parts of the thighs and legs
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Nerves from the sacral region extend to the...
thighs, buttocks, skin and legs and feet, and anal and genital regions
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the spinal cord extends from the base of the brain until about the ---------
L1-2
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Cauda equina
a bundle of nerve roots extending from the end of the spinal cord
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Structure of the Spinal Cord
The spinal cord sits inside a protective, boney tunnel created by the stacked vertebrae
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Gray matter nervous tissue
contains mostly cell bodies of motor neurons and interneurons
appears gray because of its lack of myelin
H shaped mass divided into two sets of horns:
Posterior horns and ventral horns
forms the surface of brain
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White matter nervous tissue
contains bundles of axons called tracts
Appears white because of its abundance of myelin
found under cortex
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Tracts
bundles of axons that carry impulses from one part of the nervous system to another
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Epidural space
a small space that lies between the outer covering of the spinal cord and the vertebrae
It contains a cushioning layer of fat as well as blood vessels and connective tissue
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Central canal
an opening that carry cerebrospinal fluid through the spinal cord
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Spinal nerves travel through...
gaps between the vertebrae and attached to the spinal cord by two roots: the dorsal and ventral roots
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Dorsal nerve root
contains fibres that carry sensory information into the spinal cord
It enters the dorsal horn of the spinal cord
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Ganglion
knot like structure of cell bodies of the dorsal neurons clustered
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Spinal nerve
a single nerve resulting from the fusion of the dorsal and ventral roots
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Mixed nerve
a nerve that contains both sensory and motor fibers meaning it can transmit impulses in two directions
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Ventral nerve roots
exit from the ventral horn to carry motor information out of the spinal cord
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Meninges
three layers of fibrous connective tissue that protects the spinal cord
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3 types of meninges
Pia mater
Subarachnoid space
Arachnoid mate
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Pia mater
is the innermost layer
Transparent membrane that clings to the outer surface of the brain and spinal cord
It contains blood vessels
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Subarachnoid space
lies between the arachnoid mater and the pia mater
Filled with cerebrospinal fluid
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Arachnoid mater
a delicate layer resembling a cobweb
lies between the dura mater and the pia mater
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Spinal Tracts
bundles of axons within the white matter of the spinal cord that serve as a route of communication to and from the brain
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The brain is divided into four major regions
the cerebrum,
the diencephalon,
the cerebellum
the brainstem
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The cerebrum
is the largest portion of the brain
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Gyri
sick ridges on the cerebrum
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Sulci
divide the gyri
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Fissure
deep sulci
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Longitudinal fissure
a deep groove divides the cerebrum into right and left cerebral hemispheres
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Corpus callosum
ethic bundle of nerves that runs along the bottom of the fissure and serves to connect the two hemispheres
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The diencephalon
it’s between the cerebrum in the midbrain
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Cerebellum
the second largest region of the brain
It contains more neurons than the rest of the brain combined
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The brainstem
makes up the rest of the brain consists of three structures:
Midbrain, pons and medulla oblongata
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Cortex
Covers the cerebrum and cerebellum
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Nuclei
patches of grey matter throughout the white matter
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Meninges of the Brain
cover the outside surface of the brain offering protection
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The Dura mater
consists of two layers-
periosteal layer- outer layer is attached to the inner surface of the school
meningeal layer: inner layer forms the outer covering of the brain and continues as the Dura matter of the spinal cord
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The arachnoid mater
is the middle layer
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The pia mater
clings tightly to the surface of the brain
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Dural sinuses
the Dura mater separates to create these spaces which collect blood that has passed through the brain and is on its way back to the heart
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Subdural space
separates the Dura from the arachnoid Mater
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A subarachnoid space
separates the arachnoid mater the pia mater
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Falx cerebri
dips into the longitudinal fissure two separate the right and left hemispheres
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Tentorium cerebella
extends over the top of the cerebellum operating it from the cerebrum
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brain Ventricles
four chambers in the brain
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Lateral ventricles
2 arch to the cerebral hemispheres one in the right and one on the left
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Third ventricle
connects to each of the lateral ventricles
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Fourth ventricle
narrows to form the central canal which extends through the spinal cord
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Cerebrospinal Fluid
A clear colourless fluid that fills a ventricle and central canal
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Choroid plexus:
network of blood vessels lining the floor or wall of each ventricle
forms the cerebrospinal fluid
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The division of the brain starting at the bottom
brain stem,
cerebellum,
diencephalon
cerebrum
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The brain stem consist of
midbrain, pons, and medulla oblongata
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The midbrain
contains tracks that relays sensory and motor impulses
It also contains centers for auditory and visual reflexes
contains clusters of neurons integral to muscle control
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The Pons
contains tracks that convey signals to and from different parts of the brain
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cranial nerves that arise from the Pons
V (trigeminal),
VI (abducens),
VII (facial)
VII (vestibulochlear)
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The medulla oblongata
attaches the brain to the spinal cord
contains nuclei that perform functions vital to human life
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The cardiac center
which regulates heart rate
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The Vasomotor center
Controls blood vessel diameter which affects blood pressure
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Two respiratory centers
regulate breathing
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Medulla houses...
reflect centers for coughing, sneezing, swallowing and vomiting
Several cranial nerves either begin or end in the medulla
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Cerebellum
About the size of a fist
House this morning rounds and the rest of the brain combined
Connected to the cerebral cortex by approximately 40000,000 neurons
It receives and processes messages from all over the brain
Plays a key role in motor functions, sensory, cognitive and emotional functions
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cerebellum functions
Joins forces with the cerebral cortex to monitor body movements and send messages crucial for balance, coordination, and posture
Stores information necessary for muscle groups to work together to perform smooth, efficient and coordinated movements
Evaluate sensory input, such as touch, spatial perception and sound
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Diencephalon
It’s a region deep inside the brain consisting of several structures with the chief on speaking the thalamus and hypothalamus
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Thalamus
Shaped like two eggs sitting side-by-side
Resides on the top of the brain stem
Acts as a gateway for nearly every sensory impulses travelling to the cerebral cortex
Processes and filters these impulses transmitting some but not all to the cerebral cortex
It relays messages regarding certain complex movements
is involved in memory and emotion
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hypothalamus
Influences nearly every organ in the body
Plays a key role in numerous functions:
--Controls the autonomic nervous system which is responsible for such vital functions as heart rate and blood pressure
--Contains centres responsible for hunger, thirst and temperature regulation
--Controls pituitary gland which is called the master gland because of its influence on most endocrine glands
--Is involved in multiple emotional responses including fear anger pleasure and aggression
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Reticular formation
a set of interconnected nuclei scattered throughout the brain stem
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Reticular activating system
charge with maintaining a state of wakefulness and alertness it receives sensory input from the eyes and ears
Filters of insignificant signals and sends impulses to the cerebral cortex
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Cerebrum
the largest and most obvious portion of the brain
Ability to think, remember, feel, used judgement and move
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Sulci (grooves)
divide the cerebrum into five distinct lobes
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Frontal lobe
Central sulcus forms the posterior boundary
Governs voluntary movements, memory, emotion, social judgment, decision-making, reasoning and aggression
The site for certain aspects of one’s personality
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Parietal lobe
Central sulcus forms the anterior boundary
Concerned with receiving and interpreting bodily sensations
Governs proprioception
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proprioception
the awareness of ones body and body parts in relation to each other
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Occipital lobe
Concerned with analyzing and interpreting visual information
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Insula
hidden behind the lateral sulcus
Plays a role in many different functions, including perception of pain, basic emotions, addiction, motor control, self-awareness and cognitive functioning
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Temporal lobe
Braided from the Parietal lobe by the lateral sulcus
Governs hearing, smell, learning, memory, emotional behaviour and visual recognition
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Parietal lobe lesion
it’s function in this part of the brain causes people to ignore objects on the opposite side of the body even their own arm and leg
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Temporal lobe lesion
an injury here can impair the ability to identify familiar objects
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Frontal lobe lesion
a lesion or injury here can result in severe personality disorder and cost socially inappropriate behaviour
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Occipital lobe lesion
damage here can result in blindness or other vision disturbances, hallucinations and difficulty reading and writing
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Insula lesion
damage can trigger difficulties with sensory perception, language difficulties, emotional imbalances and addiction
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White matter in the cerebrum
the bulk of the cerebrum
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Corpus callosum
a bridge that most of the tracks pass from one hemisphere to the other
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Cerebral cortex
surface of the cerebrum; a thin layer of gray matter
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Basal nuclei (basal ganglia)
Masses of gray matter that lie deep within the cerebrum and play a role in the control of movement
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The limbic system
Sometimes called the emotional brain
The seat of emotional learning
Formed by a complete set of structures that circle the corpus callosum in Thalamus
It links area of the lower brainstem with areas in the cerebral cortex associated with higher mental functions
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Two key structures of the limbic system
hippocampus and amygdala
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Hippocampus
charged with converting short-term memory into long-term memory
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Amygdala
two almond shaped masses of neurons on either side of the thalamus
Concerned with emotions such as anger, jealousy, and fear
Stores and can recall emotions from past
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Primary somatic motor area of cerebral cortex
is the pre-central Gyrus
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Motor association area
determine which movements are required to perform a specific task then sends appropriate signals to precentral gyrus
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Precentral gyrus
send impulses through motor tracts in the brainstem and spinal cord which it travels to the Skelton muscles and movement occurs
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Sensory nerve fibres of the cerebral cortex
transmit signals of the spinal cord to the thalamus which forward some to post central gyrus
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Postcentral gyrus
the primary somatic sensory area of brain
It receives impulses of heat, cold in touch from receptors all over the body
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Somatic sensory association area
adjacent to Po central Geyer’s this area allows us to pinpoint the location of pain, identify texture, and be aware of how limbs are positioned
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Primary visual cortex
written words
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Angular gyrus
translates to written words in a form that can be spoken
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Wernicke’s area
housed in the left temporal lobe formulate the words into phrases that comply with learn to grammical rules
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Broca’s area
located in left frontal lobe
Plans the muscle movement required of lyrics, tongue, cheeks and lips to form the words
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Primary motor
cortex sends impulses to the muscles necessary to produce the word
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functions of cerebral cortex
motor functions
sensory functions
language
memory
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Cerebral Lateralization
The left hemisphere is more analytical side it
Right hemisphere is more connected with creativity and spiritual ability
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left hemisphere
Motor control of right side of body
Sequential processing
Language
Analytical thought
Logical
Concrete
Science and math
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right hemisphere
Motor control of left side of body
Simultaneous processing
Big picture
Creativity
Emotion
Imagination
Art and music
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sleep NI stage
drowsy
easily arroused
2-5%
190
sleep N2 stage
light sleep
loss of environmental awareness
breathing and heart rate regular
45-55%
191
Sleep N3 stage
Deep
So relax, heart rate slows down and blood pressure drops
Blood supply to muscles increases allowing for tissue growth and repair
Growth hormones are released
12-23%
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Stage REM sleep
Dreaming occurred
Eyes move rapidly back-and-forth
First occurs 90 minutes into sleep cycle
Last 10 mins to 1 hour
20-25%
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olfactory association area
interprets the sense of smell
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primary gustatory complex
how does the interpretation of sensation and taste
195
visual association area interprets the information acquired through the primary visual cortex
Allows us to recognize familiar objects
196
Auditory association area
Gives us the ability to recognize familiar sounds including a persons voice or the name of a piece of music
197
Primary auditory complex
responsible for hearing
