Exam 4 Flashcards
these 2 systems share responsibility for maintaining homeostasis throughout the body.
The nervous system and the endocrine system
is specialized for rapid transmission of signals from one part of the body to another part of the body by way of nerves
nervous system
is specialized for sending chemical messengers from glands to target cells by way of blood stream
endocrine system
Sensory receptors
detect internal and/or external stimuli.
Incoming sensory information
gets processed and analyzed by neural integration.
Outgoing signals
are sent to effectors, which carry out the required response.
The central nervous system (CNS) consists of
the brain and the spinal cord.
The central nervous system (CNS)
integrates and correlates sensory information, generates thoughts and emotions, forms and stores memories, stimulates muscles to contract and glands to secrete
The peripheral nervous system (PNS) consists of
cranial nerves and spinal nerves that are located outside of the central nervous system.
somatic nervous system (SNS)sensory (afferent) component
carry towards the CNS
somatic nervous system (SNS) motor (efferent) component
carry away from the CNS
autonomic nervous system (ANS) sensory (afferent) component
contains neurons that carry information from visceral receptors toward CNS
autonomic nervous system (ANS) motor (efferent) component
contains neurons that conduct nerve signals from CNS to smooth muscle, cardiac muscle, glands
autonomic nervous system (ANS) motor (efferent) component sympathetic division
controls processes that tend to arouse the body and involve the expenditure of energy
autonomic nervous system (ANS) motor (efferent) component parasympathetic division
controls processes that tend to have a calming effect on the body and restore/conserve energy
Excitability
describes the ability of a nerve cell to respond to environmental stimuli.
Conductivity
describes the ability of a nerve cell to transmit signals to another nerve cell.
Nerve cells (neurons)
highly specialized components of the nervous system. (they are long lived; they cannot divide, so they cannot be replaced; they have a high metabolic rate)
Functional Classification of Neurons
is based upon the direction that a nerve signal travels in reference to the central nervous system.
Sensory (afferent) neurons
transmit signals about light, heat, pressure, and/or chemicals from various receptors toward the cental nervous system.
Interneurons (association neurons)
within the cental nervous system carry out integrative function by transferring signals between sensory neurons and motor neurons.
Motor (efferent) neurons
send signals away from the cental nervous system to various effectors, such as muscles or glands.
the cell body (soma; perikaryon) contains
a single, centrally located nucleus surrounded by cytoplasm and most of the organelles.
cytoskeleton
contains microtubules and actin neurofibrils that form Nissl bodies, compartments in rough ER
Nissl bodies
dark staining regions involved in protein synthesis
mature neurons
lack centrioles, which renders them incapable of undergoing mitosis
Unspecialized cells in CNS
can develop new neurons
Dendrites
short, branching processes with enormous surface area that allows them to receive signals from adjacent neurons.
Axons
long and thin cylindrical processes that conduct signals away from a cell body.
axon originates
from a conical elevation of the soma called an axon hillock
axoplasm
lacks Nissl bodies and Golgi apparatus; surrounded by axolemma
distal end of an axon
branches extensively and each axon terminal ends in a synaptic knob
synaptic knobs
contain synaptic vesicles that store chemical neurotransmitters
Proteins that are needed for a neuron to function properly
are synthesized in the cell body and transported to the axon.
slow axonal transport
moves materials down the axon and supplies new axoplasm needed for developing or regenerating neurons
fast axonal transport
uses protein “motors” to move materials and organelles in both directions between soma and axon terminals
Some pathogens can invade nervous system
by entering synaptic knobs and using fast axonal transport to travel to soma (herpes simplex virus, rabies virus, polio virus, tetanus toxin)
Neurons can be classified structurally
according to number of processes that extend from the soma.
unipolar neurons
have a single axon that extends away from the soma
location of unipolar neurons
Usually found in nerves that carry sensory signals to spinal cord
bipolar neurons
have a single axon and a single dendrite
location of bipolar neurons
Found in retina of eye, inner ear, nose
multipolar neurons
have a single axon and many dendrites
location of multipolar neurons
Most common neurons in brain and spinal cord
anaxonic neurons
have no axon and multiple dendrites
location of anaxonic neurons
Found in retina of eye
Neuroglia (glial cells)
fill spaces between neurons and provide support for neurons.
Neuroglia (glial cells) numbers
There may be 10 trillion neurons in body; glial cells may outnumber neurons 50 to 1 and they retain their ability to divide throughout life
gliomas
malignant brain tumors made of glial cells that actively undergo mitosis
Astrocytes
the most abundant glial cells in the cental nervous system.
Astrocytes description
star-shaped cells with many processes that cover the brain and form a support framework for nervous tissue
Astrocytes form
tight junctions with endothelial cells of blood capillaries to produce a blood-brain barrier that can regulate passage of materials into brain
Astrocytes maintain
the proper balance of potassium ions for generating nerve impulses
Astrocytes produce
scar tissue when neurons are damaged
Oligodendrocytes
also found in the cental nervous system.
possess fewer processes than astrocytes, but wrap around neurons to produce a myelin sheath, which forms insulating layer around neuron
Ependymal cells
also found in the cental nervous system.
resemble cuboidal epithelial cells and line cavities in the brain and spinal cord where they secrete cerebrospinal fluid that circulates through CNS
Microglia
small macrophages scattered throughout the cental nervous system.
phagocytize bacteria that invade the CNS and remove debris caused by tissue damage
Schwann cells
found in the PNS, where they form a neurilemma around neurons.
produce a myelin sheath around neurons in the PNS
assist in regenerating peripheral neurons
Satellite cells
found in the PNS around nerve cell bodies.
Myelin
a lipoprotein that forms an insulating sheath around an axon in order to increase the speed at which a nerve signal travels along a neuron.
myelin composition
20% protein and 80% lipid; fat intake is essential during childhood
In the peripheral nervous system, Schwann cells
wrap around the axons of neurons and form myelin sheaths that have multiple layers.
cytoplasm of the Schwann cell
gradually squeezed out, so the myelin sheath consists of many concentric layers of Schwann cell membranes with outermost forming a neurilemma that contains nucleus
Around neurilemma
endoneurium of fibrous connective tissue
nodes of Ranvier
narrow gaps in the myelin sheath between Schwann cells
In the cental nervous system, oligodendrocytes
spiral around axons to form myelin sheaths.
Neither neurilemma nor endoneurium form around neurons in CNS
If a neuron in the peripheral nervous system gets damaged
it can be regenerated if its cell body and some of the neurilemma remain intact.
regeneration tube
formed by neurilemma and endoneurium across the damaged area, which guides growth of new axonal processes
If a neuron in the central nervous system gets damaged,
it is not likely to be regenerated because it lacks the neurilemma and the endoneurium that are needed to form the regeneration tube.
Neurons
excitable cells and they communicate with one another by using electrical potentials and electrical currents.
electrical potential
the difference in concentration of charged particles on either side of the membrane of a neuron
electrical current
involves a flow of charged particles from one point to another
When a neuron is stimulated,
the electrical potential can change suddenly and produce local potentials and/or action potentials.
Potentials occur because
of ion channels in membrane of neuron
Ion channels allow
electrolytes to flow across the membrane, which establishes a current.
leakage channels
always open and allow sodium and potassium ions to flow
gated channels open and close in response to some stimulus
voltage-gated channels-
open and close in response to some kind of stimulus
ligand-gated channels
open and close in response to specific chemical stimulus
mechanically gated channels
open and close in response to vibration, pressure, or tissue stretching
There is a difference in electrical charges between extracellular fluid and intracellular fluid because
of an unequal distribution of ions on either side of the membrane of the neuron.
plasma membrane of the neuron is
selectively permeable
ions diffuse down their concentration gradient through the
plasma membrane
there is an electrical attraction between
cations and anions
The plasma membrane of a neuron
more permeable to potassium than any other ions.
concentration of potassium ions is higher in
the ICF than in the ECF
large organic anions
trapped inside the neuron and tend to draw some potassium ions back into neuron along electrical gradient
concentration of sodium ions is higher in
the ECF than in the ICF, so sodium ions tend to diffuse into neuron down their concentration and electrical gradients
inside of a neuron
is negative with respect to the outside and is polarized
Diffusion of sodium ions into the neuron and diffusion of potassium ions out of the neuron would
eventually eliminate the resting membrane potential.
ATP-driven membrane pump
actively transports three sodium ions out of the neuron and two potassium ions into the neuron per molecule of ATP spent to keep the RMP at -70 millivolts
A local potential
a small change in the resting membrane potential of a neuron caused by a stimulus that opens a ligand-regulated sodium gate in the membrane of the neuron.
local potential typically begins
at a dendrite, spreads through soma, then travels from axonal trigger zone to synaptic knob
local potentials are useful …
only for short-distance communication
Local potentials are graded because
they vary in size according to the stimulus strength.
strong stimulus causes a greater change in membrane potential and more gates open; allows current to flow further
Local potentials are decremental
because they become weaker as they spread away from the point of stimulation.
Plasma membrane is permeable to ions, so charge is lost and current dies out
Local potentials are reversible
because the resting membrane potential gets restored if the stimulation ceases prematurely.
A local potential is excitatory
if it depolarizes the plasma membrane of the neuron, which makes the potential difference less negative.
A local potential is inhibitory
if it hyperpolarizes the plasma membrane of the neuron, which makes the potential difference more negative.
An action potential
a dramatic change in the membrane potential of a neuron resulting from opening and closing voltage-gated ion channels during an interval of 1 millisecond.
An excitatory stimulus applied to a neuron
will generate an excitatory local potential that depolarizes the membrane and causes resting membrane potential to be less negative.
if the excitatory local potential spreads to the “trigger zone” and remains strong enough,
it can open enough voltage-regulated gates to generate an action potential
If the plasma membrane reaches a critical threshold voltage of about -55 mV,
voltage-gated sodium channels open.
Sodium ions rush into the neuron
and establish positive feedback that depolarizes the membrane potential from -55 mV to zero to +35 mV.
Depolarization
causes slow sodium inactivation gates to close, which prevents any more sodium ions from entering the neuron.
At peak depolarization,
slow voltage-gated potassium channels open and potassium ions rush out of the neuron to repolarize membrane potential from +30 mV to zero to -70 mV.
Voltage-gated potassium channels remain open longer than voltage-gated sodium channels,
so a loss of potassium ions may cause after-hyperpolarization; this makes membrane potential more negative than resting membrane potential until voltage gated potassium channels close and restore RMP
some of the characteristics of an action potential:
they follow an all-or-none principle because any stimulus that depolarizes membrane to threshold will generate action potential
they do not become weaker as they spread away from the point of stimulation
they are irreversible
The refractory period
a brief period of time during which a neuron may not be able to generate another action potential.
An absolute refractory period
lasts from threshold until repolarization is complete.
a neuron cannot be restimulated by a stimulus of any strength because voltage gated sodium channels open and are then inactivated
A relative refractory period
lasts until hyperpolarization ends.
a neuron can be restimulated if a stimulus is larger than threshold
Supra threshold stimulus
If one neuron is to going to communicate with another neuron,
the nerve signal must travel the length of the axon.
nerve signal is a traveling wave of excitation produced by a self-propagating chain of action potentials moving in only one direction
In unmyelinated fibers,
there is a step-by-step depolarization of each adjacent area of the plasma membrane, which produces continuous conduction; propagation is slow, but not decremental; last action potential generated at synaptic knob has same voltage as first action potential generated at trigger zone
In myelinated fibers
the nerve signal appears to “leap” along the neuron from one node of Ranvier to the next node of Ranvier by saltatory conduction.
propagation is much faster, but it is decremental
Signal gets weaker, but reaches next node of Ranvier just in time to open voltage-gated sodium channels to generate new action potential
Propagation speed
not determined by the strength of a stimulus, but by the presence or absence of myelin, by the diameter of the fiber, and by the temperature.
large diameter fibers
conduct signals faster than small diameter fibers because large fibers tend to be myelinated and small fibers tend to be unmyelinated; large diameter fibers conduct signals faster because there is more surface area
nerve fibers conduct signals faster when the temperature is warm
A synapse
a junction between two neurons across which a nerve signal is conducted.
pre-synaptic neuron
conducts information towards a synapse and a post-synaptic neuron conducts information away from the synapse
Synaptic knob of presynaptic neuron
separated from postsynaptic neuron by a narrow synaptic cleft
single neuron in the cerebellum of the brain
may have 100,000 synapses
synapse may be
axodendritic or axosomatic or axoaxonic
At an electrical synapse,
a nerve signal is transmitted by the flow of ions from one cell to another through gap junctions.
these synapses allow fast communication, synchronization among multiple neurons or muscle fibers, and two-way transmission of signals
At a chemical synapse,
a nerve signal is transmitted by small organic neurotransmitters.
neurotransmitter is synthesized by the pre-synaptic neuron and stored in vesicles
neurotransmitters are released from a pre-synaptic neuron in response to a stimulus
neurotransmitters bind to specific receptors on the post-synaptic neuron
neurotransmitters alter the physiology of the post-synaptic neuron
There are more than 100 substances that have been classified as
neurotransmitters
acetylcholine (ACh)
the most familiar and it can be excitatory or inhibitory
Responsible for neuromuscular activity
amino acids
can be excitatory or inhibitory
Glutamate
excitatory neurotransmitter involved in learning and memory (amino acid)
GABA
inhibitory neurotransmitter in brain (amino acid)
biogenic amines
modified amino acids that may be excitatory or inhibitory
Serotonin or catecholamines (dopamine, epinephrine, norepinephrine ) play roles in emotional behavior or operation of ones 'biological clock'
neuropeptides
amino acid chains that may be excitatory or inhibitory
Some neuropeptides are neuromodulators because they function like hormones
Neuropeptides may be responsible for
craving fat and/or sugar and may be a cause of some eating disorders
Substance P
mediates pain
Endorphins and enkephalins
act as natural opiates to reduce perception of pain (‘runners euphoria’; placebo effect)
Acetylcholine
the neurotransmitter at an excitatory cholinergic synapse. (Neuromuscular junction)
GABA
the neurotransmitter at an inhibitory synapse.
GABA works like acetylcholine, except it opens chloride channels and hyperpolarizes the post-synaptic membrane making it harder to generate action potential
Norepinephrine
the neurotransmitter at an excitatory adrenergic synapse.
norepinephrine operates through a second-messenger system that activates a transmembrane G protein and binds it to adenylate cyclase
adenylate cyclase catalyzes the conversion of ATP to cyclic AMP (cAMP)
cAMP binds to a ligand-regulated ion gate on the inside of the membrane and opens it to depolarize the membrane
cAMP activates cytoplasmic enzymes that catalyze changes in metabolic reactions
cAMP also induces transcription
Neurotransmitters
must be removed from synaptic cleft to stop the transmission of nerve signals.
they can diffuse out of the synaptic cleft into the extracellular fluid where they get absorbed by astrocytes to be returned to pre-synaptic neuron
they can be actively transported back into the neuron that released them
acetylcholine can be degraded in the synaptic cleft by acetylcholinesterase
Postsynaptic potentials
graded potentials, so their size varies according to the strength of the stimulus and the amount of neurotransmitter that was released.
If a neurotransmitter causes depolarization of the post-synaptic membrane,
an excitatory postsynaptic potential (EPSP) occurs because sodium ions flow into the cell.
membrane potential approaches threshold so neuron is easier to stimulate
If a neurotransmitter causes hyperpolarization of the post-synaptic membrane,
an inhibitory postsynaptic potential (IPSP) occurs because chloride ions flow into the cell or potassium ions flow out of the cell.
membrane potential moves away from threshold so neuron is harder to stimulate
A typical neuron receives signals from thousands of pre-synaptic neurons and integrates them at the trigger zone through a process known as
summation
Whether post synaptic neuron fires depends on
NET input of EPSPs and IPSPs
a typical EPSP is too weak and too short-lived to
depolarize the membrane to threshold
Temporal summation
occurs at a single synapse because each EPSP is generated at such a short interval that the previous EPSP hasn’t decayed.
if enough EPSPs are generated to depolarize the post-synaptic membrane to threshold, an action potential is generated
Spatial summation
occurs when several pre-synaptic neurons generate EPSPs at the same time.
a single synapse only allows a small number of sodium ions into the post-synaptic membrane, but if multiple synapses allow enough sodium ions to enter and the post-synaptic membrane is depolarized to threshold, an action potential can be generated
Several neurons may cooperate through _____________ to enhance the effects of one another.
facilitation
One pre-synaptic neuron may suppress another pre-synaptic neuron by
pre-synaptic inhibition in order to halt the transmission of a nerve signal.
Alzheimer disease
characterized by reduced attention span, progressive memory loss, disorientation, and a dramatic change in personality, resulting in dementia.
Alzheimer disease is due to
the degeneration of cholinergic neurons causing a deficiency in acetylcholine
Alzheimer disease treatment modalities include
acetylcholinesterase inhibitors and nerve growth factor
Alzheimer disease diagnosis
can only be confirmed by an autopsy that detects beta-amyloid plaques around neurons and neurofibrillary tangles inside brain neurons
Parkinson disease
involves a progressive loss of motor function that leads to involuntary tremors, facial rigidity, “gawking”, shuffling gait, slurred speech, and illegible handwriting.
Parkinson disease is due to
the degeneration of dopamine-releasing neurons in the brain; might be caused by exposure to environmental toxins
Parkinson disease treatment modalities include
drugs or dopamine-rich tissue transplants or surgery to remove brain tissue that might be responsible for the tremors
Gray matter contains
cell bodies, dendrites, unmyelinated axons, and neuroglia.
Gray matter nuclei
clusters of nerve cell bodies
gray matter is
the main site of synaptic contact between neurons
White matter contains
myelinated axons.
White matter tracts
bundles of myelinated axons that carry nerve signals within the CNS
The brain is divided into several principal _________
REGIONS
brainstem-
continuous with spinal cord; components include medulla oblongata, pons, mid brain, reticular formation
cerebellum-
posterior to brainstem; divided into hemispheres
diencephalon-
components include thalamus, hypothalamus, epithalamus
cerebrum-
occupies most of cranium; divided into hemispheres; components include basal nuclei and limbic system
Meninges
fibrous connective tissue coverings surrounding the brain and spinal cord.
The outermost meninx is the
dura mater, which consists of dense irregular connective tissue that lines the cranial cavity and surrounds the spinal cord.
between the dura mater and the wall of the vertebral canal is an ___________________________filled with blood vessels, adipose tissue, loose connective tissue
epidural space
cranial dura mater
lies tightly against the cranial bones and consists of two layers
Extensions of dura mater separate major parts of brain
The middle meninx is the
arachnoid mater, which consists of delicate collagen fibers and some elastic fibers.
arachnoid mater is separated from the dura mater by a fluid-filled
subdural space
The inner meninx is the
pia mater, which is a thin layer of transparent collagen and elastic fibers that adhere to the spinal cord and brain.
between the arachnoid mater and the pia mater is a _____________________ filled with cerebrospinal fluid
subarachnoid space
Meningitis
inflammation of the arachnoid mater and/or pia mater caused by bacteria and/or viruses that invade the central nervous system via the nose or throat.
Meningitis extremely serious disease among
infants and children between ages of 3 months and 2 years
in bacterial meningitis,
brain swells, ventricles enlarge, and brainstem may start to hemorrhage
Symptoms include go fever, stiff neck, drowsiness, intense headache, coma
Death may occur within hours of onset
Ventricles
four fluid-filled chambers in the brain.
What are the four ventricles in the brain?
two lateral ventricles extend into the cerebral hemispheres
third ventricle is located along the midline of the brain and it connects to the lateral ventricles by way of an interventricular foramen
fourth ventricle is connected to the third ventricle by the cerebral aqueduct
cerebral aqueduct
forms a central canal that extends through the spinal cord
These ventricles and canals are lined with
ependymal cells and capillary networks to form choroid plexuses that produce and secrete up to 500 mL of cerebrospinal fluid each day.
cerebrospinal fluid is constantly reabsorbed, so circulating volume is
100-160 mL
Cerebrospinal fluid (CSF)
a clear, colorless liquid containing proteins, glucose, urea, salts, and various ions that serves several useful purposes.
Cerebrospinal fluid (CSF) provides
provides buoyancy so the brain “floats” in the cranial cavity; a medium for exchanging nutrients and wastes between blood and nerve tissue
Cerebrospinal fluid (CSF) functions
a shock absorber to protect the brain and spinal cord from jolts
Cerebrospinal fluid circulates through the ventricles, into the central canal of the spinal cord, and into the subarachnoid space where it is gradually
reabsorbed into the blood.
Any obstruction or inflammation of the brain that interferes with the circulation of cerebrospinal fluid can cause
hydrocephalus
hydrocephalus
an accumulation of fluid in the ventricles that can compress delicate nervous tissue and damage the brain.
The brain must be well-supplied with oxygen and nutrients because it is
one of the most metabolically active organs of the body.
10 second interruption of blood flow can cause
loss of consciousness
1-2 minute interruption of blood flow can
impair neurological function
4 minute interruption of blood flow can
produce irreversible brain damage
There is a brain barrier system that is
highly permeable to water, glucose, oxygen, carbon dioxide, alcohol, caffeine, nicotine, and anaesthesia, but it blocks the delivery of most drugs.
blood-brain barrier forces
materials that leave the blood to pass through cells rather than pass between them, because brain capillaries are less permeable than most other capillaries
blood-CSF barrier regulates
the passage of materials from cerebrospinal fluid into the brain
medulla oblongata
the inferior brainstem continuous with the spinal cord.
The anterior surface of the medulla oblongata
exhibits two large, bulging pyramids.
pyramids
contain large motor tracts that connect the brain to the spinal cord
Fibers from left pyramid
cross to body’s right side i n phenomenon of decussation
fibers from right pyramid
cross to body’s left side in phenomenon of decussation
Lateral to each pyramid
an oval olive that contains nuclei to relay sensory information from the brain and/or spinal cord to the cerebellum.
The medulla oblongata contains
several control centers that are vital to homeostasis.
cardiac center regulates heart rate
vasomotor center adjusts the diameter of blood vessels to regulate blood pressure
respiratory centers adjust the rate and depth of breathing; Other centers control reflexes associated with coughing, sneezing, swallowing, vomiting.
The pons lies…
lies superior to the medulla oblongata and anterior to the cerebellum.
The pons is
a “bridge” with tracts and nuclei that connect the brain with the spinal cord and also connect parts of the brain with each other.
some pontine nuclei
nuclei work with the medullary respiratory center to control respiration
other pontine nuclei are associated with equilibrium/posture, taste/swallowing, and hearing
The midbrain
extends from the pons to the lower portion of the diencephalon.
A pair of cerebral peduncles
anchor the cerebrum to the brainstem and contain tracts that run through the midbrain to carry motor signals to the medulla oblongata.
The main mass of the midbrain contains
a highly vascular red nucleus, which connects with the cerebellum to permit fine motor control.
The substantia nigra
is a darkly pigmented nucleus that controls subconscious muscle actions by relaying inhibitory signals to various parts of the brain.
Degeneration of neurons in substantia nigra produces
muscle tremors characteristic of Parkinson’s disease
The posterior portion of the midbrain is the
tectum
tectum contains _______ corpora quadrigemina that protrude from its roof
four
superior colliculi
serve as reflex centers for blinking, focusing eyes, moving head and neck to visually track moving objects
inferior colliculi
serve as reflex centers for movements of head in response to auditory stimuli (sudden loud sounds)
The reticular formation contains
more than 100 small areas of gray matter interspersed throughout the medulla oblongata, pons, and midbrain.
Somatic motor control maintains
balance and posture in response to sensory signals from the eyes and ears about body position and the position of nearby objects.
The reticular formation contributes to
cardiovascular control by integrating the cardiac center and the vasomotor center in the medulla oblongata.
The reticular formation plays a central role in
maintaining consciousness and awakening from sleep.
The reticular formation allows us to
ignore traffic sounds or other inconsequential noises, but causes us to respond quickly to an alarm clock or a flash of lightning
The reticular formation transmits
pain signals from the lower body to the cerebral cortex.
Damage to the reticular formation can
produce an irreversible coma.
The cerebellum is
the second-largest portion of the brain, comprising about 11% of the brain’s mass, and it occupies the inferior and posterior region of the cranial cavity.
Contains about 100 billion neurons
The right and left cerebellar hemispheres are linked by a
medial vermis.
surface of the cerebellum consists of
leaf-like folia consisting of gray matter
arbor vitae
a deeper “tree-like” mass consisting of white matter
The cerebellum attaches to
the brainstem by three pairs of cerebellar peduncles.
inferior pair of cerebellar peduncles
connects with the medulla oblongata to facilitate muscle performance
middle pair of cerebellar peduncles
transmits signals from the pons to coordinate muscle responses
superior pair of cerebellar peduncles
transmits motor signals through the midbrain and the thalamus
The cerebellum serves mainly as
a reflex center to coordinate subconscious movements of skeletal muscle that are necessary for muscle coordination, balance, and posture.
also involved in time-keeping and the perception of elapsed time
The cerebellum receives
sensory information about the position of limbs, joints, and other body parts in order to maintain unconscious control over walking, dancing, or catching a ball.
The thalamus is
the largest component of the diencephalon and it contains paired oval masses of gray matter located beneath each cerebral hemisphere.
is a “gateway to the cerebral cortex” and it filters sensory impulses arriving from the spinal cord, brainstem, or cerebellum before relaying them to the cerebral cortex.
thalamus
Nuclei within the thalamus carry out a variety of functions:
some nuclei receive and integrate auditory, visual, and taste information
some nuclei receive and integrate information about pain, temperature, light touch, pressure
some nuclei relay signals to motor control areas in the cerebrum
some nuclei are involved in emotion, memory, and cognition
The hypothalamus is
inferior to the thalamus and also contains many nuclei.
there are two small, round ____________________ that play a role in memory
mammillary bodies
stalk-like __________ attaches the pituitary gland to the hypothalamus
infundibulum
supraoptic and preoptic regions
are involved in autonomic and endocrine activities (hypothalamus)
The hypothalamus maintains
homeostasis by regulating internal processes through the autonomic nervous system and the endocrine system.
Nuclei within the hypothalamus- integrating center for the autonomic nervous system regulates
heart rate, blood pressure, digestion, urination, and other visceral activities
some nuclei within the hypothalamus produce and release
hormones to control the pituitary gland
hypothalamic thermostat
monitors the blood in order to control body temperature
“heat-losing center” controls vasodilation in skin and sweating
“heat-producing center” controls vasoconstriction, shivering, "goose bump" formation
“hunger” and “satiety” centers within the hypothalamus
monitor levels of glucose and amino acids in the blood in order to regulate food intake
“thirst” center within the hypothalamus
monitors osmolarity and dehydration to regulate fluid intake
hypothalamus connection with the reticular formation
regulates circadian rhythms associated with sleeping/waking
some nuclei within the hypothalamus
control anger, aggression, fear, pain, pleasure, sexual behavior
Epithalamus- A pineal gland
involved in maintaining the body’s biological clock.
Habenular nuclei (Epithalamus)
involved in emotional response to odors.
The cerebrum
the largest region of the brain and accounts for 83% of total brain mass.
Cerebrum- There is a superficial layer of gray matter called the
cerebral cortex.
all neurons in the cerebral cortex are
interneurons
gyri
folds or ridges at the surface of the cerebrum
Gyri function
increase surface area to improve information processing capabilities
sulci
shallow grooves between gyri
fissures
deep grooves between gyri
The cerebrum is divided into
left and right hemispheres by the longitudinal fissure.
two hemispheres are connected internally by the
corpus callosum
Each hemisphere can be subdivided into
frontal, parietal, temporal, and occipital lobes.
central sulcus separates
the frontal lobe from the parietal lobe
precentral gyrus
anterior to central sulcus
postcentral gyrus
posterior to central sulcus
lateral sulcus separates
parietal lobe from the temporal lobe
insula
a small mass of cortex located deep to the lateral sulcus
Most of the cerebrum is located
beneath the cerebral cortex and comprised primarily of white matter.
association tracts
transmit nerve signals between gyri in the same hemisphere
commissural tracts
transmit nerve signals from gyri in one hemisphere to the corresponding gyri in the opposite hemisphere by way of the corpus callosum
projection tracts
form ascending tracts to carry nerve signals up to the cerebrum and form descending tracts to carry motor signals to the brainstem and spinal cord
The basal nuclei
masses of gray matter located lateral to the thalamus.
The basal nuclei receive
input from the red nuclei and the substantia nigra of the midbrain in order to control muscle tone required for gross voluntary movements (walking).
Damage to the basal nuclei
can produce the involuntary muscle movements that are associated with Parkinson disease.
The limbic system
a ring of structures around the corpus callosum and the thalamus.
The limbic system includes
the amygdala and hippocampus nuclei, the fornix tract, and the cingulate gyrus
The amygdala
involved in emotion and behavior associated with pleasure and pain.
The hippocampus
involved in memory storage and may facilitate links between memory and emotions, particularly those memories associated with pleasure or pain or smell.
The cerebrum interprets
sensory impulses, controls voluntary motor responses, directs intellectual processes, stores memories, and governs personality traits.
Although the two cerebral hemispheres appear identical,
anatomical and functional differences between them lead to cerebral lateralization. ( highly correlated with “handedness” and somewhat correlated with gender
prone to change as a person grows older)
The left hemisphere
appears to be more important for right-hand control, spoken and written language, numerical and scientific skills, and logic.
The right hemisphere
appears to be more important for left-hand control, musical and artistic awareness, perception of patterns and spatial relationships, insight, imagination, and mental imagery of sights, sounds, smells, and tastes.
The primary somatosensory area
is located in the postcentral gyrus of each parietal lobe.
The primary somatosensory area receives
sensory information about joint and muscle position
also receives sensory information about touch and pain and temperature from skin and muscle receptors to determine exact point of origin
The primary visual area
located in the posterior occipital lobe.
The primary visual area receives
signals from the eyes about shape, color, and movement of visual stimuli
The primary auditory area
located in the superior temporal lobe and partly in the insula.
The primary auditory area interprets
basic characteristics of sound, such as pitch and rhythm
The primary olfactory area
located on the medial surface of the temporal lobe and the inferior surface of the frontal lobe.
The primary olfactory area receives
signals related to smell
The primary gustatory area
located at the base of the postcentral gyrus.
The primary gustatory area receives
signals related to taste
Motor areas
control voluntary movement of skeletal muscles.
The primary motor area
located in the precentral gyrus of the frontal lobe.
The primary motor arealarge pyramidal neurons
project to spinal cord and form pyramidal motor tracts, which control voluntary contractions of specific muscles or groups of muscles on opposite side of body
Broca’s area
located in the left frontal lobe and contains the motor speech area.
Broca’s area coordinates
complex muscle actions of the tongue, mouth, and larynx that enable a person to translate his/her thoughts into spoken words
injury to Broca’s area can cause
aphasia
word deafness
inability to understand spoken words
word blindness
inability to recognize written words
The somatosensory association area
located in the parietal lobe behind the postcentral gyrus.
The somatosensory association area functions
integrates and interprets sensory information about the shape and/or texture of an object
makes us aware of the orientation of one object to another object and makes us aware of the position of our limbs
stores memories of past sensory experiences
The visual association area
located in the occipital lobe.
The visual association area function
allows us to recognize and evaluate what we see and what we have seen
The auditory association area
located in the superior temporal lobe.
The auditory association area functions
it helps us determine whether sound is speech or music or noise
it enables us to recall a song or melody; enables us to recognize a person’s voice
The premotor area
located in the frontal lobe, anterior to the primary motor area.
The premotor area function
enables us to “plan” the degree and sequence of muscle actions needed for learned motor activities that are complex and sequential (writing, typing, speaking)
Wernike’s area
located in the left temporal lobe, posterior to the lateral sulcus.
Wernike’s area function
responsible for recognizing speech and written language
Brain cells generate
considerable amount of electrical activity from nerve signal transmission and an electroencephalogram (EEG) can provide a record of the brain waves that result.
alpha waves
occur in individuals who are awake or resting with closed eyes
They disappear when person becomes mentally engaged or falls asleep
beta waves
present when a person is alert and mentally active
theta waves
normally occur in children or in sleeping adults
Presence in adults who are awake indicate emotional stress or brain disorders
delta waves
present in alert infants and in adults during deep sleep
Presence in adults who are awake may indicate serious brain damage
Sleep
a state of temporary unconsciousness from which an individual can be aroused.
cycle of sleep and waking
one of our circadian rhythms that repeats at 24 hour intervals
Timing of this cycle is controlled by nuclei in hypothalamus and brainstem
non-rapid eye movement (NREM).
One type of sleep in the sleep cycle
NREM Stage 1
a transition between wakefulness and sleep when we relax and close our eyes and let our mind wander
NREM Stage 2
(“light sleep”) is characterized by sleep spindle brain waves; more difficult to arouse individual
NREM during Stage 3
(“moderate sleep”), body temperature and blood pressure decrease and pulse and breathing rate slow down
NREM during Stage 4
(“deep sleep”), muscles are very relaxed
Nightmares, night terrors, bed-wetting, sleepwalking may occur in this stage
rapid eye movement (REM)
Another type of sleep in the sleep cycle, which begins about 90 minutes after sleep begins provided NREM stage 4 has been achieved
most individuals experience ________ episodes of REM during each sleep cycle
three to five (Eyes dart back and forth under closed eyelids)
vital signs during REM
increase and brain becomes more active; most dreaming occurs during REM sleep
Skeletal muscles during REM
inhibited and go limp to prevent one from ‘acting out’ his/her dreams
REM episodes
get progressively longer as the sleep cycle lengthens
REM sleep may give the brain
an opportunity to organize and/or strengthen desirable memories and/or forget unwanted memories
The spinal cord conducts
sensory information from the periphery of the body to the brain, and it conducts motor signals from the brain to peripheral effectors.
The spinal cord triggers
repetitive, coordinated muscle contractions necessary for walking.
The spinal cord establishes
reflex pathways.
The spinal cord
a slender cylindrical column extending from the medulla oblongata, through the foramen magnum into the vertebral canal, down to second lumbar vertebra.
The spinal cord is covered by
spinal meninges that extend from meninges that cover brain
spinal dura mater
not attached to the walls of the vertebral column, but is surrounded by a fat-filled epidural space
two conspicuous enlargements of the spinal cord
cervical enlargement and lumbar enlargement
cervical enlargement
extends from the fourth cervical vertebra to the first thoracic vertebra; nerves arise to innervate upper extremities
lumbar enlargement
extends from the ninth through the twelfth thoracic vertebrae; nerves arise to innervate pelvic region and lower limbs
Below the lumbar enlargement the spinal cord tapers to form the _____________________ which is anchored to the base of the spine by fibrous connective tissue.
medullary cone
spinal nerves that arise from the lower part of the spinal cord form the
cauda equina (‘horses tail’);
cauda equina innervates
pelvic organs and lower limbs
