ch. 49 Flashcards
what do all animals have
a nervous system
cnidarian examples
jellyfish, hydras, anemones
nervous system of cnidarians
- nerve net
- neurons connected to each other in network
- activation of neurons in one area lead to activation of all or most neurons
simplest of nervous systems
nerve net
nervous system of echinoderms
- nerve ring around mouth connected to larger radial nerves extending to arms
- mouth and arms operate independently
nervous system of planaria
- nerve cords extend by length of animal connected by transverse nerves
- collection of neurons in head form cerebral ganglia
- perform basic integration of sensory input and motor output
nervous system of annelids
- same basic structure as planaria
- more neurons
- ventral nerve cords have ganglia in each segment
- rudimentary brain
nervous system of simple mollusks
- similar to annelids
- pair of anterior ganglia
- paired nerve cords
cephalization
increasingly complex brain in head
brain of drosophila
several subdivisions with separate functions
brain of advanced mollusks
brains with well-developed subdivisions
glial cells/glia function
nourish, support, and regulate neurons
what do embryonic radial glia form
tracks along which newly formed neurons migrate
astrocytes
participate in formation of blood-brain barrier
blood-brain barrier
restricts entry of most substances into the brain
what can radial glial cells and astrocytes both act as
stem cells
where does the CNS develop from
hollow dorsal nerve cord
what does the cavity of the nerve cord give rise to
narrow central canal of the spinal cord and ventricles of the brain
what are the spinal canal and ventricles filled with
cerebrospinal fluid
cerebrospinal fluid
supplies CNS with nutrients and hormones, carries away waste
gray matter
- neuron cell bodies
- dendrites
- unmyelinated axons
white matter
- bundles of myelinated axons
what does the spinal cord do
- convey info to/from brain
- generate basic pattern of locomotion
- produces reflexes independently of the brain
reflex
body’s automatic response to a stimulus
function of PNS
- transmit info to/from CNS
- regulates movement and internal environment
afferent neurons in PNS
transmit info to CNS
efferent neurons in PNS
transmit information away from CNS
divisions of autonomic nervous system
- sympathetic
- parasympathetic
- enteric
2 efferent components of CNS
autonomic nervous system and motor system
motor system
carries signals to skeletal muscles and can be voluntary
autonomic nervous system
regulates smooth and cardiac muscles, generally involuntary
enteric nervous system
exerts direct control over the digestive tract, pancreas, and gallbladder
sympathetic division
regulates arousal and energy generation (fight/flight)
parasympathetic division
antagonistic effects of sympathetic on target organs
- promotes calming and return to rest/digest functions
functions of parasympathetic divison
- constricts eye pupil
- stimulates salivary gland secretion
- constricts bronchi in lungs
- slows heart
- stimulates activity of stomach/intestines/pancreas
- stimulates gallbladder
- promotes emptying of bladder
- promotes erection of genitalia
3 major regions of vertebrate brain
- forebrain
- midbrain
- hindbrain
forebrain
- processing of olfactory input, regulation of sleep, learning, and any complex procesing
midbrain
coordinates routing of sensory input
- receives and integrates sensory information and sends in to specific regions of the brain
hindbrain
controls involuntary activities and coordinates motor activities
what does the difference in size of particular brain regions among vertebrates show
relative importance of particular brain function
how many neurons and synapses in the human brain
- 100 billion neurons
- 100 trillion connections
anterior neural tube
gives rise to the forebrain, midbrain, and hindbrain during embryonic development
what form the brainstem?
midbrain and part of the hindbrain
where is the brainstem
joins with spinal cord at base of brain
what does the rest of the hindbrain give rise to
cerebellum
what does the forebrain divide into
- diencephalon
- telencephalon
diencephalon
forms endocrine tissues in brain
telencephalon
becomes cerebrum
what does the cerebrum control
- skeletal muscle contraction
- center for learning
- emotion
- memory
- perception
outer layer of the cerebrum
cerebral cortex
function of cerebral cortex
- perception
- voluntary movement
- learning
corpus callosum
thick band of axons that enables the right and left cerebral cortices to communicate
what does the cerebellum coordinate
- movement
- balance
- learning
- remembering motor skills
what does the diencephalon give rise to
- thalamus
- hypothalamus
- epithalamus
hypothalamus
control center that includes the body’s thermostat and central biological clock
brainstem composition
- midbrain
- pons
- medulla oblongata
major function of pons and medulla
to transfer information between the PNS and the midbrain/forebrain
medulla function (automatic)
- breathing
- heart/blood vessel activity
- swallowing
- vomiting
- digestion
what do the brainstem and cerebrum control
arousal and sleep
what is sleep for the brain
an active state
function of sleep
essential for survival and may play a role in the consolidation of learning and memory
reticular formation
network formed mainly of neurons in the midbrain and pons
- controls arousal and sleep
function of reticular formation
timing of sleep periods characterized by rapid eye movements and vivid dreams
bottlenose dolphins and sleep
- can swim while sleeping
- EEG data suggest that only one side of brain sleeps at a time
circadian rhythms
daily cycles of biological activity
- cycles of sleep and wakefulness
biological clock
molecular mechanism that directs periodic gene expression and cellular activity
what are biological clocks typically synchronized to
light and dark cycles
what coordinates circadian rhythms
group of neurons in the hypothalamus called the suprachiasmatic nucleus
- acts as pacemaker
what does generation and experience of emotions involve
limbic system:
- amygdala
- hippocampus
- parts of thalamus
amygala
mass of nuclei near the base of the cerebrum that is most important to the storage of emotion in the memory
PET (positron-emission tomography)
enables display of metabolic activity through injection of radioactive glucose
fMRI (functional magnetic resonance imaging)
brain activity detected through changes in local oxygen concentration
largest structure in the human brain
cerebrum
function of cerebrum
- language
- cognition
- memory
- consciousness
- awareness of our surroundings
4 regions/lobes of brain
- frontal
- temporal
- occipital
- parietal
where does cerebral cortex receive input from
sensory organs and somatosensory receptors
somatosensory receptors
provide information about touch, pain, pressure, temperature, and the position of muscles and limbs
what directs different types of input to distinct locations
thalamus
beginnings of somatosensory system
receptors located in the skin, joins, ligaments, muscles, and fascia
2 types of somatosensory receptors
- exteroceptive - dermis
- proprioceptive - within body
where does integrated sensory information pass to
prefrontal cortex, which helps plan actions and movements
neuron arrangment in somatosensory cortex and motor cortex
arranged according to the part of the body that generates input or receives commands
damage to Broca’s area
can understand language but cannot speak
damage to Wernicke’s area
unable to understand language, but can still speak
lateralization
differences in hemisphere function
how do 2 hemispheres work together
by communicating through the fiber of the corpus callosum
frontal lobe damage results in…
impaired decision making and emotional responses, but leave intellect and memory intact
what do the frontal lobes have a substantial effect on
executive functions
steps of embryonic development of nervous system
- regulated gene expression and signal transduction determine where neurons form
- neurons compete for growth-supporting factors to survive
- only half the synapses that form survive into adulthood
- synapse elimination
neuronal plasticity
ability of nervous system to be modified after birth
- changes can strengthen/weaken signaling at synapse
autism
developmental disorder that involves a disruption in activity-dependent remodeling at synapses
- impaired communication/social interaction
- repetitive behaviors
what is essential to the formation of memories
neuronal plasticity
where is short-term memory accessed
hippocampus
where is long-term memory formed
links in hippocampus replaced by connections in the cerebral cortex
when is some consolidation of memory thought to occur?
during sleep
disorders of the nervous system
- schizophrenia
- depression
- drug addiction
- Alzheimer’s disease
- Parkinson’s disease
how much of the world’s population suffers from schizophrenia
1%
symptoms of schizophrenia
- hallucinations
- delusions
schizophrenia
- affects neuronal pathways that use dopamine as a neurotransmitter
- Amy also alter glutamate signaling
2 broad forms of depressive illness
- major depressive disorder
- bipolar disorder
major depressive disorder
patients have persistent lack of interest or pleasure in most activities
bipolar disorder
manic (high-mood) and depressive (low-mood) phases
treatments for depression
drugs that increase the activity of biogenic amines in the brain
brain’s reward system
rewards motivation with pleasure
why are some drugs addictive
increase activity of brain’s reward system
addictive drugs
cocaine, amphetamine, heroin, alcohol, tobacco
what is drug addiction characterized by
compulsive consumption and an inability to control intake
what do addictive drugs enhance
activity of dopamine pathway
what does drug addiction lead to
long-lasting changes in the reward circuitry that cause a craving for the drug
Alzheimer’s disease
mental deterioration (dementia) characterized by confusion and memory loss
what does incidence of Alzheimer’s increase with
age
what is Alzheimer’s associated with
formation of neurofibrillary tangles and amyloid plaques in the brain
is there a cure for Alzheimer’s?
no, but some drugs relieve symptoms
Parkinson’s disease
motor disorder caused by death of dopamine-secreting neurons in the midbrain
what is Parkinson’s disease characterized by
muscle tremors, flexed posture, shuffling gait
cause of Parkinson’s disease
no identifiable cause, although one form is known to have a genetic basis
can Parkinson’s disease be cured
no but can be treated
- dopamine-related drug called L-dopa can reduce severity
- potential cure: implantation of dopamine-secreting neurons into the brain
