Nervous System and Endocrine System Flashcards
action potentials
electrochemical impulses that help cells transmit and process info from one part of the body to another
synaptic transmission
action potential being transformed into a chemical signal causing release of neurotransmitter into the synaptic cleft
neuron
basic functional and structural unit of the nervous system
synaptic cleft
small gap where chemical messengers travel across
resting membrane potential
created by Na+/K+ ATPase and potassium leak channels, causes cells to be polarized
Depolarization changes this potential and repolarization returns the potential to normal (-70)
depolarization
propagation of action potentials caused by voltage gated sodium channels allowing sodium ions to flow down their gradient into the cell
threshold potential
-50 mV, reached by opening of voltage gated sodium channels
repolarization steps
VG sodium channels inactivate very quickly, VG potassium channels open and potassium leaves cell, causing membrane potential to reach -90 mV
K+ leak channels and Na+/K+ ATPase also functioning to return membrane to resting potential
myelin
insulating sheath composed of Schwann cells, a type of glial cell. no membrane depolarization and no voltage gated sodium channels in regions of the axonal plasma membrane wrapped in myelin
saltatory conduction
rapid jumping of action potentials from node to node in myelinated cells
glial cells
specialized, non-neuronal cells that typically provide structural and metabolic support to neurons
equilibrium potential
where there is no net movement of ions across the membrane
Na+ has positive equilibrium potential and K+ has negative equilibrium potential
refractory period
when a cell can’t transmit another action potential, two different periods:
absolute refractory - neuron won’t fire another action potential no matter how strong a membrane depolarization is induced
relative refractory period - depolarization required is greater than normal because the membrane is hyperpolarized
steps for transmission of a signal across a chemical synapse in the nervous system
- action potential reaches end of axon
- Depolarization of presynaptic membrane opens voltage gated calcium channels
- Calcium influx into presynaptic cell causes release of NT stored in secretory vesicles
- NT diffuse across narrow synaptic cleft
- NT binds to postsynaptic receptors
- membrane polarization of postsynaptic cell changes
- Action potential in post synaptic cell initiates if depolarization of postsynaptic cell occurs
- Degradation of NT in synaptic cleft
Acetylcholine
neurotransmitter related at neuromuscular junction
excitatory vs inhibitory NTs
depolarizes postsynaptic membrane vs hyper polarizes postsynaptic membrane
summation
effect of all synapses on membrane potential measured by postsynaptic neuron to decide whether to fire an action potential, can be temporal (rapid firing of action potentials) or spatial (summing of EPSPs and IPSPs from all of the synapses)
efferent vs afferent neurons
carry info away from CNS vs carry info to CNS
reflex
sensory neuron transmits an action potential to a synapse with a motor neuron in the spinal cord
doesn’t involve brain
ex. knee jerk reflex where sensory neuron is activated that directly synapses with a motor neuron in the spinal cord, causing the quadriceps to contract
reciprocal inhibition
concurrent relaxation of one muscle and contraction of another
somatic vs autonomic systems
voluntary vs involuntary
parasympathetic vs sympathetic
parts of autonomic system
rest and digest vs fight or flight
grey matter vs white matter
unmyelinated neuronal cell bodies vs myelinated axons in CNS and PNS
CNS vs PNS
CNS - brain/spinal cord
PNS - includes all other axons, dendrites, and cell bodies
three subdivisions of the brain
hindbrain, midbrain, forebrain
what does the entire Brain float in
cerebrospinal fluid, which serves various functions in shock absorption and exchange of nutrients and waste
spinal cord function
pathway for info to and from the brain, processing and integration of info, primitive processes like walking, sex, and urination
hindbrain parts
medulla - controls autonomic processes such as blood pressure, blood flow, heart rate, swallowing
pons- connects spinal cord and medulla with upper regions of brain, controls balance
cerebellum - integrating center functioning in movement coordination
midbrain functions
responsible for arousal or wakefulness
forebrain parts
diencephalon, telencephlon
thalamus function
contains relay and processing centers for sensory info
hypothalamus
primary link between nervous and endocrine systems, controls homeostatic functions like temperature regulation, fluid balance, and appetite
corpus callosum
thick bundle of axons that connects cerebral hemisphere
function of cerebral hemispheres
conscious thought processes and intellectual functions
four lobes of cerebral cortex
frontal (voluntary movement), parietal (general sensations), temporal (auditory and olfactory sensation), occipital (visual sensation), involved in higher thought processes
basal nuclei
found deep within cerebral hemispheres, function in voluntary motor control and procedural learning related to habits
limbic system
located between cerebrum and diencephalon, important in emotion and memory
cranial nerves
convey sensory and motor info to and from the brainstem
vagus nerve effect
type of cranial nerve that decreases heart rate and increases GI activity
What is true about the somatic system
all somatic motor neurons innervate skeletal muscle cells, use ACh as their neurotransmitter, and have their cell bodies in the brain stem or the ventral position of the spinal cord
all somatic sensory neurons have a long dendrite extending from a sensory receptor toward the soma, an axon extends from the somatic sensory neuron into the spinal cord
anatomy of the autonomic system
preganglionic neuron has a cell body in the brainstem or spinal cord, which sends an axon to the autonomic ganglion, located outside the spinal column.
This axon synapses with the postganglionic neuron, which sends an axon to an effector.
sympathetic vs parasympathic preganglionic soma locaction
sympathetic - thoracic and lumbar spinal cord
parasympathetic - brainstem and sacral spinal cord
adrenal gland characteristics
includes inner medulla and outer cortex, part of sympathetic nervous system, releases epinephrine
types of sensory receptors
mechanoreceptors - respons to mechanical disturbances such as pressure
chemoreceptors
nociceptors - pain receptors
thermoreceptors
electromagnetic receptors
four properties of stimulus that need to be communicated to CNS
- type of stimulus
- location of stimulus
- intensity of stimulus coded by frequency of action potentials
- stimulation duration
adaptation
decreases in firing frequency when the intensity of a stimulus remains constant
proprioception
awareness of self (ex. awareness of body part position)
gustation vs olfaction
taste and smell, rely on chemoreceptors
ear structure
includes outer ear, middle ear, and inner ear
mechanism of hearing
- sound waves enter external ear to pass into auditory canal, causing eardrum to vibrate
- malleus attached to eardrum receives vibrations
- vibrations passed to incus then stapes (middle ear)
- Vibration of oval window creates pressure waves in perilymph and endolymph, fluids in the cochlea.
- Basilar membrane vibration occurs through cochlea, causing dendrites form bipolar auditory afferent neurons to be stimulated
What is the primary site at which auditory stimuli are detected
organ of Corti in the cochlea
how is pitch distinguished
by which regions of the basilar membrane vibrate
vestibular complex function
contains tubes filled with endolymph and contains hair cells that detect motion, important for balance
direction of light in eye
cornea (bends/refracts light) to sclera to choroid to retina, the surface upon which light is focused.
iris
colored part of eye, regulates diameter of pupil
vitreous chamber
where light passes through en route from lens to retina
rods and cones
synapse with bipolar cells ( cells with one axon and one dendrite)
rods function in night vision and cones are responsible for color vision and high acuity vision
optic disk
blind spot, where axons from ganglion cells converge to form optic nerve, contains no photoreceptors
opsin
bound to retinal, changes structure upon absorbing light
role of glutamate in rods and cones
glutamate released onto bipolar cells during their depolarization and less is released during hyperpolarization
on center vs off center bipolar cells
inhibited by more glutamate vs stimulated by more glutamate
on center cells are depolarized when light is shone directly on them
off center cells are depolarized when light is shone on surrounding areas (in the dark)
parallel processing
many aspects of a visual stimulus are processed simultaneously instead of in a step by step or serial fashion
absolute threshold
minimum stimulus required to activate a sensory receptor 50 percent of the time
bottom up and top down processing
bottom up - begins with sensory receptors and works up to the complex integration of info occurring in the brain
top down - brain applies experience and expectations to interpret sensory info
How are the nervous system and endocrine system connected
neurons can signal the release of hormones from endocrine glands
endocrine gland
ductless gland whose secretory products are picked up by capillaries supplying blood to the region
hydrophilic vs hydrophobic hormones
hydrophilic - bind to receptors on cell surface (ex. peptides)
hydrophobic - bind to receptors in cellular interior (ex. steroids)
tropic hormones
hormones that regulate hormones (ex. adrenocorticotropic hormone)
releasing/ inhibiting factors
released by hypothalamus to regulate other tropic hormones
hypothalamic pituitary portal system
special miniature circulatory system provided for efficient transport of hypothalamic releasing and inhibiting factors to anterior pituitary
anterior vs posterior pituitary
anterior - normal endocrine gland controlled by hypothalamic releasing/inhibiting factors
posterior - composed of axons which descend from hypothalamus
thyroid hormone/ cortisol function
broad effects on metabolism and energy usage
