AnP Chapter 11 CNS (LO7) Flashcards
nervous system overview
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
Endocrine system
employs chemical messengers (hormones) to communicate with cells
Nervous system
uses electrical signals to transmit messages at lighting speed
3 essential roles of the nervous system and how they work
- 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
Two main divisions of the nervous system
central nervous system (CNS) and peripheral nervous system (PNS)
Central nervous system
consists of the brain and spinal cord
Peripheral nervous system
consists of the vast network of nerves throughout the body
Neurobiology
study of the nervous system
Subdivisions of peripheral nervous system
Sensory (afferent) division
Motor (efferent) division
Sensory (afferent) division:
carries signals from nerve endings to CNS
Sensory (afferent) subdivisions
Somatic sensory
Visceral sensory
Somatic sensory
carries signals from bones, skin, joints and muscles
Visceral sensory
carries signals from viscera of heart, lungs, stomach and bladder
Motor (efferent) division:
transmits impulses from the CNS out to the peripheral organs to cause an effect or action
Motor (efferent) subdivisions
Somatic motor
Autonomic motor
Somatic motor
allows voluntary movements of skeletal muscles
Autonomic motor
provides ‘automatic’ activities such as control of blood pressure and heart rate
Sympathetic division
arouses the body for action
Parasympathetic division
has a calming effect
2 types of cells a make up the nervous system
neurons (impulse conducting cells)
neuroglia (protect neurons)
neuralgia
also called glial cells
Supportive cells of nervous system
Bind neurons together
Perform various functions that enhance performance
50 glial cells per neuron
5 types of glial cells
Neuroglial of CNS : Oligodendrocyte Ependyma Microglia Astrocytes
Neurons of PNS:
Schwann cells
Oligodendrocytes
form myelin sheath in the brain and spinal cord; speed signal conduction
Ependymal cells
line spinal cord and cavities of the brain; some secrete cerebrospinal fluid, whereas other have cilia that aid fluid circulation
Microglia
perform phagocytosis, engulfing microorganisms and cellular debris
Astrocytes
extend through brain tissue, nourish neurons; help form blood-brain barrier; attach neurons to blood vessels; provide structural support
Schwann cells
form myelin sheath around nerves in PNS; form neurilemma
Glial cell tumours
highly malignant grows rapidly; most adult brain tumors consist of
Blood-brain barrier
semipermeable membrane that exists throughout the brain that protects the brain of foreign substances
NEURONS
Nerve cells that handle the nervous system’s role of communication
3 classes of neurons
Sensory (afferent)
Interneurons
Motor (efferent) neurons
Sensory (afferent) neurons
Detect stimuli (touch, pressure, heat, cold or chemicals) and transmits about the stimuli to CNS
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
Motor (efferent) neurons
Rely messages from brain to muscle or gland cells
how do neurone vary
Vary greatly in shape and size
Vary according to type, number and length of projections
Multipolar neurons
Have one axon and multiple dendrites
Most common type of neuron and includes most neurons of brain and spinal cord
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
Unipolar neurons
Have once process: an axon that extends from the cell body before branching into T shape
Mostly in sensory nerves of PNS
NEURON STRUCTURE
3 basic parts: body and two extensions ( axon and dendrite)
Cell body (soma)
is the control center of the neuron and contains the nucleus
Dendrites
receives signals from other neurons and conduct the info to the cell body
Some neurons only have one dendrite some have thousands
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
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
Nodes of Ranvier
evenly spaced gaps in myelin sheath
Synaptic knob
the end of the axon branch
Vesicles containing a Neurotransmitter are found within
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
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
Neurilemma
outer layer of schwann cell
Essential for an injured nerve to regenerate
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
Nerves in PNS can regenerate or not regenerate?
can regenerate as long as the soma and neurilemma are intact
Nerves in CNS can regenerate or not regenerate?
cannot regenerate because lacks neurilemma
Axon Hillock
area where the cell body and axon join
Axon Collateral
side branches off of the axon, usually at right angles of the axon
Axon Terminals
the end of the axon and axon collateral processes, just before the portion where the neurotransmistters are released
Synaptic End Bulbs
bulb-shaped structures at the end of axon terminals, contain synaptic vesicles
Axolemma
plasma membrane surrounding the axon
IMPUSLE CONDUCTION
Nerves must initiate and transmit signals at lightning speed to relay messages to organs and tissue
Signal transmission
occurs through electrical current which results from flow of charged particles from one point to another
Membrane potential
when ions with opposite charges are separated by a membrane the potential exists for them to move toward one another
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
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
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
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
define depolarization
membrane becomes more positive
define Action potential
neuron has become active as it conducts an impulse along the axon
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
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
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
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
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
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
Saltatory conduction
Impulses “leap” from node to node because action potentials on occur at the nodes
Synapse
space between the junction of two neurons in a neutral pathway
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
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
5 steps of how synapses work
- 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 - The infusion of calcium causes the vesicle to fuse with the plasma membrane and then release their store of a neurotransmitter into the synapse
- Once release the neurotransmitter binds to receptors on the postsynaptic membrane
- -Each new transmitter has a specific receptor - 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 - The receptors and then release the neurotransmitter after which is reabsorbed by the synaptic knobs and recycled or destroyed by enzymes
More than —- different neurotransmitters in the body
100
Small molecule neurotransmitters
trigger rapid synaptic actions
Neuropeptides
modulate slower ongoing synaptic functions
common neurotransmitters
acetylcholine,
epinephrine/norepinephrine, serotonin,
dopamine
histamine
Threshold point
The critical level needed to open the sodium (Na+) channels and cause an action potential to follow
Absolute refractory period
The period of time during which the cell cannot respond again, no matter how strong the stimulus
Relative refractory period
The period of time during which a cell can only be made to respond with a suprathreshold stimulus
The spinal cord
is the information passageway that relays messages from the brain to the rest of the body
Nerves in the cervical region of the spinal cord innervate the…
chest, head, neck, shoulders, arms, hands and diaphragm
Nerves from the thoracic region extend to the…
intercostal muscles of the rib cage, the abdominal muscles, and the back muscles
The lumbar spine nerves innervate the…
lower abdominal wall and parts of the thighs and legs
Nerves from the sacral region extend to the…
thighs, buttocks, skin and legs and feet, and anal and genital regions
the spinal cord extends from the base of the brain until about the ———
L1-2
Cauda equina
a bundle of nerve roots extending from the end of the spinal cord
Structure of the Spinal Cord
The spinal cord sits inside a protective, boney tunnel created by the stacked vertebrae
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
White matter nervous tissue
contains bundles of axons called tracts
Appears white because of its abundance of myelin
found under cortex
Tracts
bundles of axons that carry impulses from one part of the nervous system to another
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
Central canal
an opening that carry cerebrospinal fluid through the spinal cord
Spinal nerves travel through…
gaps between the vertebrae and attached to the spinal cord by two roots: the dorsal and ventral roots
Dorsal nerve root
contains fibres that carry sensory information into the spinal cord
It enters the dorsal horn of the spinal cord
Ganglion
knot like structure of cell bodies of the dorsal neurons clustered
Spinal nerve
a single nerve resulting from the fusion of the dorsal and ventral roots
Mixed nerve
a nerve that contains both sensory and motor fibers meaning it can transmit impulses in two directions
Ventral nerve roots
exit from the ventral horn to carry motor information out of the spinal cord
Meninges
three layers of fibrous connective tissue that protects the spinal cord
3 types of meninges
Pia mater
Subarachnoid space
Arachnoid mate
Pia mater
is the innermost layer
Transparent membrane that clings to the outer surface of the brain and spinal cord
It contains blood vessels
Subarachnoid space
lies between the arachnoid mater and the pia mater
Filled with cerebrospinal fluid
Arachnoid mater
a delicate layer resembling a cobweb
lies between the dura mater and the pia mater
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
The brain is divided into four major regions
the cerebrum,
the diencephalon,
the cerebellum
the brainstem
The cerebrum
is the largest portion of the brain
Gyri
sick ridges on the cerebrum
Sulci
divide the gyri
Fissure
deep sulci
Longitudinal fissure
a deep groove divides the cerebrum into right and left cerebral hemispheres
Corpus callosum
ethic bundle of nerves that runs along the bottom of the fissure and serves to connect the two hemispheres
The diencephalon
it’s between the cerebrum in the midbrain
Cerebellum
the second largest region of the brain
It contains more neurons than the rest of the brain combined
The brainstem
makes up the rest of the brain consists of three structures:
Midbrain, pons and medulla oblongata
Cortex
Covers the cerebrum and cerebellum
Nuclei
patches of grey matter throughout the white matter
Meninges of the Brain
cover the outside surface of the brain offering protection
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
The arachnoid mater
is the middle layer
The pia mater
clings tightly to the surface of the brain
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
Subdural space
separates the Dura from the arachnoid Mater
A subarachnoid space
separates the arachnoid mater the pia mater
Falx cerebri
dips into the longitudinal fissure two separate the right and left hemispheres
Tentorium cerebella
extends over the top of the cerebellum operating it from the cerebrum
brain Ventricles
four chambers in the brain
Lateral ventricles
2 arch to the cerebral hemispheres one in the right and one on the left
Third ventricle
connects to each of the lateral ventricles
Fourth ventricle
narrows to form the central canal which extends through the spinal cord
Cerebrospinal Fluid
A clear colourless fluid that fills a ventricle and central canal
Choroid plexus:
network of blood vessels lining the floor or wall of each ventricle
forms the cerebrospinal fluid
The division of the brain starting at the bottom
brain stem,
cerebellum,
diencephalon
cerebrum
The brain stem consist of
midbrain, pons, and medulla oblongata
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
The Pons
contains tracks that convey signals to and from different parts of the brain
cranial nerves that arise from the Pons
V (trigeminal),
VI (abducens),
VII (facial)
VII (vestibulochlear)
The medulla oblongata
attaches the brain to the spinal cord
contains nuclei that perform functions vital to human life
The cardiac center
which regulates heart rate
The Vasomotor center
Controls blood vessel diameter which affects blood pressure
Two respiratory centers
regulate breathing
Medulla houses…
reflect centers for coughing, sneezing, swallowing and vomiting
Several cranial nerves either begin or end in the medulla
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
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
Diencephalon
It’s a region deep inside the brain consisting of several structures with the chief on speaking the thalamus and hypothalamus
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
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
Reticular formation
a set of interconnected nuclei scattered throughout the brain stem
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
Cerebrum
the largest and most obvious portion of the brain
Ability to think, remember, feel, used judgement and move
Sulci (grooves)
divide the cerebrum into five distinct lobes
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
Parietal lobe
Central sulcus forms the anterior boundary
Concerned with receiving and interpreting bodily sensations
Governs proprioception
proprioception
the awareness of ones body and body parts in relation to each other
Occipital lobe
Concerned with analyzing and interpreting visual information
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
Temporal lobe
Braided from the Parietal lobe by the lateral sulcus
Governs hearing, smell, learning, memory, emotional behaviour and visual recognition
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
Temporal lobe lesion
an injury here can impair the ability to identify familiar objects
Frontal lobe lesion
a lesion or injury here can result in severe personality disorder and cost socially inappropriate behaviour
Occipital lobe lesion
damage here can result in blindness or other vision disturbances, hallucinations and difficulty reading and writing
Insula lesion
damage can trigger difficulties with sensory perception, language difficulties, emotional imbalances and addiction
White matter in the cerebrum
the bulk of the cerebrum
Corpus callosum
a bridge that most of the tracks pass from one hemisphere to the other
Cerebral cortex
surface of the cerebrum; a thin layer of gray matter
Basal nuclei (basal ganglia)
Masses of gray matter that lie deep within the cerebrum and play a role in the control of movement
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
Two key structures of the limbic system
hippocampus and amygdala
Hippocampus
charged with converting short-term memory into long-term memory
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
Primary somatic motor area of cerebral cortex
is the pre-central Gyrus
Motor association area
determine which movements are required to perform a specific task then sends appropriate signals to precentral gyrus
Precentral gyrus
send impulses through motor tracts in the brainstem and spinal cord which it travels to the Skelton muscles and movement occurs
Sensory nerve fibres of the cerebral cortex
transmit signals of the spinal cord to the thalamus which forward some to post central gyrus
Postcentral gyrus
the primary somatic sensory area of brain
It receives impulses of heat, cold in touch from receptors all over the body
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
Primary visual cortex
written words
Angular gyrus
translates to written words in a form that can be spoken
Wernicke’s area
housed in the left temporal lobe formulate the words into phrases that comply with learn to grammical rules
Broca’s area
located in left frontal lobe
Plans the muscle movement required of lyrics, tongue, cheeks and lips to form the words
Primary motor
cortex sends impulses to the muscles necessary to produce the word
functions of cerebral cortex
motor functions
sensory functions
language
memory
Cerebral Lateralization
The left hemisphere is more analytical side it
Right hemisphere is more connected with creativity and spiritual ability
left hemisphere
Motor control of right side of body
Sequential processing
Language
Analytical thought
Logical
Concrete
Science and math
right hemisphere
Motor control of left side of body
Simultaneous processing
Big picture
Creativity
Emotion
Imagination
Art and music
sleep NI stage
drowsy
easily arroused
2-5%
sleep N2 stage
light sleep
loss of environmental awareness
breathing and heart rate regular
45-55%
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%
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%
olfactory association area
interprets the sense of smell
primary gustatory complex
how does the interpretation of sensation and taste
visual association area interprets the information acquired through the primary visual cortex
Allows us to recognize familiar objects
Auditory association area
Gives us the ability to recognize familiar sounds including a persons voice or the name of a piece of music
Primary auditory complex
responsible for hearing
