bmsc midterm 2 cards Flashcards
the central nervous system
brain and spinal cord
seperated into gray matter a and white matter
gray consists: consists of unmyelinated somas, dendrites and axons,
white: mainly myelinated axons
spinal cord
major pathways for information flowing back and forth between the brain and the skin, joints and muscles of the body
divided into 4 segments:
cervical (8)
thoracic (12)
lumbar (5)
sacral (5)
coccygeal (1)
ascending tracts
descending tracts
ascending tracts: carry sensory information to the brain
dorsal and external lateral
descending tracts: carry commands to motor neurons
ventral and interior lateral
spinal reflex
the spinal cord can act as the integrating center to initiate a response to a stimulus without receiving input from the brain
important in body movement
brain
organ providing human species with its unique attributes
1400g, 1.4 kg, 85 billion neurons, many containing thousands of synapses
6 major divisions:
cerebrum
cerebellum
diencephalon
brainstem: midbrain, pons, medulla
ultimate emergent property
the brain
the ultimate emergent property: how do chemical and electrical signals in neurons lead to complex behaviours?
individual neurons reductionist, then groups of neurons (circuits, pathways, networks) then complex behaviour
brainstem
oldest region, 4 major regions
mid brain, pons, medulla, and recticular formation
ascending and descending tracts run through the brain stem
contain 11 of 12 cranial nerves: carry sensory and motor info for head and neck
contain many nuclei
involved in many basic processes in the body including arousal and sleep, muscle tone and stretch reflexes, coordination of breathing, blood pressure regulation and modulation of pain
medulla (part of brainstem)
right at the junction of the spinal cord
white matter contain all ascending somatosensory tracts and descending corticospinal tracts
90% of corticospinal tracts decussate (crossover) at the pyramids
why the left side of brain controls the right body
nuclei in the medulla control many involuntary functions, including the cardiovascular center and the medullary respiratory center
contains the vomiting center
contains the deglutition center (swallowing)
caughing, sneezing, hiccuping
nuclei and ganglia
nuclei: clusters of cell bodies in CNS
ganglia: clusters of cell bodies in PNS
dorsal horn and ventral horn (grey matter)
parts of the gray matter
info comes out (efferent) the ventral root and within the horns there are nuceli
the ventral horn consists of somatic motor nuclei and autonomic efferent nuclei
dorsal horn consists of somatic sensory nuclei ( info from the skin to the brain)
viscreal sensory nuceli carrys info from internal organs than to the brain
pons and midbrain
pons: contain nuceli and tracts
relays info between the cerebellum and cerebrum
assists the medulla in the coordination of breathing
midbrain (mesencephalon): junction between lower brainstem and diencephalon (nuclei and tracts)
primary function is controlling eye movement
also relay auditory and visual reflexes (movement of body in response to these stimuli)
contains the substania nigra
reticular formation
extends throughout the brainstem: small clusters of neuronal cell bodies interspersed among tracts (ascending and descending)
important in consciousness, arousal, attention, and alertness
reticular activating system RAS inactivated during sleep, damage can induce coma
regulates muscle tone, assists in vital functions (HR,BP, resp rate)
cerebellum
second largest brain structure
two cerebellar hemispheres
processes sensory info related to movement and coordinates the execution of movement
sends feedback signals to motor areas of the cerebral cortex, via its connections to the thalamus and pons helping to correct any erros and smooth the movements
main area regulating posture and balance
diencephalon
lies between the brain stem and cerebrum
two primary structures: thalamus and hypothalamus
two endocrine structures: pineal gland and pituitary
thalamus
part of the diencephalon
relay center: receives sensory info from optic tract, ears, spinal cord and relays it to relevant sensory areas in cortex
relays info from cerebellum to motor areas in cortex
pineal gland
part of the diencephalon
cyclically releases melatonin involved in sleep/wake
hypothalamus
part of the diencephalon
center for homeostasis
influences autonomic and endocrine function
functions: activates sympathetic nervous system
maintains body temp
controls body osmolarity
controls reproductive functions
controls food intake
influences behaviour/emotions
influences cardiovascular control
pituitary gland
endocrine structure in the diencephalon
output of the hypothalamus
posterior pituitary is neural tissue, an extension of the brain that secretes neurohormones made in the hypothalamus
anterior pituitary is endocrine tissue
one hormone releases that is involved in a series of hormones
cerebrum
largest part of the brain
gray matter includes the cerebral cortex, basal ganglia, and limbic system
white matter: tracts,
area of higher processing “seat of intelligence”
two hemispheres divided into 4 lobes, connected by corpus callosum
frontal lobe, pariental temporal, occipital
basal nuclei (ganglia) should be nuclei but can be called ganglia
three nuclei collectively termed the basal ganglia (nuclei)
-globus pallidus, putamen, caudate nucleus
major job is regulating the initiation and termination of movement
receives input from cerebral cortex and provides output to motor portions of the cortex
limbic system
“emotional brain” plays a role in a range of emotions, including pain, pleasure, anger, affection
also believed to play a primary role in learning and memory
3 major componetns: cingulate gyrus
amygdala (emotion)
hippocampus (memory)
cerebral cortex
outermost layer of the cerebrum
integrating center for CNS
functionally divided into 3 specializations:
1)sensory areas (translate sensory input into perception)
2) motor areas (direct skeletal muscle movement)
3) association areas (integrate info from sensory and motor areas and help direct voluntary behaviours and deal with complex integrative functions)
lobes
frontal lobe: primary motor cortex, motor association area (premotor cortex)
parietal lobe: primary somatic sensory cortex, sensory association areas
occipital lobe: vison,
temporal lobe: hearing, balance
cerebral laterlization (dominance)
distribution of functional areas in the two hemispheres is not symmetrical
writing in the right hemisphere why your dominant in the right hemisphere
this is just avg not for sure
sensory system purpose
provides infro about the environment inside and outside the body
special senses vs somatic sense (both processed consciouslly)
specical:vision, hearing, taste, smell, equilbrium
somatic: touch, temperature, pain, itch, proprioception
somatic stimuli vs viscreal stimuli (both subconscious)
somatic: muscle length and tension, proprioception
viscreal: blood pressure, distension of gastrointestinal tract, blood glucose concentration, internal body temp
general properties of sensory systems
a sensory neuron with a transducer (receptor), that converts a physical stimulus into a intracellular signal (change in membrane potential),
usually through the opening or closing of gated channels
simple, complex, special sensory receptors
simple receptors: are neurons with free nerve endings. may have myelinated or unmyelinated
complex neural receptors: have nerve endings enclosed in connective tissue capsules, touch/proprioception
most special senses are cells that release neurotransmitter onto sensory neurons, initiating action potenitals.
types of sensory receptors
chemoreceptors: oxygen, pH, various organic molecules such as glucose
blood chemoreceptors, nociceptors, taste, smell
mechanoreceptors: pressure (baroreceptors), cell stretch (osmoreceptors), vibration, sound
touch, proprioceptors, auditory, balance
photoreceptors: photons of light, vision (rodes and cones)
thermoreceptors: varying degrees of heat, thermal receptors, nociceptors
mechanically gated channels
coverts mechanical stimulus into electrical signal
receptor potential aka generator potential (equivalent to graded potential)
receptive fields
physical area where a sensory receptor can respond within
sensory neurons are activated by stimuli and fall within the physical area
size depends on the type of sensory receptor
if there is convergence of multiple primary neurons onto a secondary neuron, meaning multiple primary will synapses on a secondary
convergence creates a large receptive field
small fields in sensitive areas
CNS integrates sensory information
visceral sensory info is integrated in the brain stem and spinal cord
almost all special and somatic sensory info routed through the thalamus
thalamus directs it to the relevant cortical centers
olfactory pathwyas from the nose project through the olfactory bulb to the olfactory cortex
equilbrium pathways project primarily to the cerebellum
special senses and somatic senses
special senses: have dedicated cortical regions
somatic senses: integrated in the primary somatosensory cortex
CNS distinguishes four properties of stimulus.
this is how CNS detect one sensation from the other
1) modality- the physical stimuli being sensed, determined by the sensory receptor being activated, temperature vs touch receptor and where the pathways terminate in the brain
2)location
3)intensity
4)duration
location of stimulus
coded according to which receptive fields are being activated
Most sensory stimuli for specific regions of the body are projected to particular areas of the somatosensory cortex
determined by where in teh cerebral cortex sensory info is projected to
large regions of the cortex dedicated to large regions of the body such as touch
intensity and duration of stimulus
because AP amplitude is constant, intensity cannot be determined by amplitude.
intensity is determined by the number of receptors being activated (population coding) and the frequency of action potentials coming from those receptors (frequency coding)
duration of stimulus is determined by how long APs are being activated
duration also depends on receptor adaptation
tonic vs phasic
tonic receptors: slowly adapting receptors that respond for the duration of a stimulus
parameters that need to be constantly monitored
phasic receptors: rapidly adapt to a constant stimulus and turn off
respond of a change in parameter, stop once stimulus costant
sensory pathway specificity
1) Each receptor is most sensitive to a particular type of stimulus
2) a stimulus above threshold initiates AP’s in a sensory neuron that project to the CNS
3) stimulus intensity and duration are coded in the pattern of AP’s reaching the CNS
4) stimulus location and modality are coded according to which receptors are activated or by the timing of receptor activation
5) each sensory pathway projects to a specific region of the cerebral cortex dedicated to a particular receptive field. the brain can then tell the origin of each incoming signal
autonomic nervous system
involuntary control of smooth muscle, cardiac muscle, many glands and some adipose tissue
subdivided: sympathetic (fight of flight) and parasympathetic (rest and digest)
the autonomic nervous system works closely with the endocrine system and behavioural systems to maintain homeostasis
autonomic pathways have two efferent neurons in series
1 preganglionic will synapse with 8 or 9 postganglionic neuron
CNS—> preganglionic–> autonomic—> postganglionic—-> target tissue (smooth muscle, gland etc)
sympathetic (pre and post ganglionic)
ganglia are mainly found in two ganglion chains running along side vertebral column
preganglionic neurons orginate in thoracic and lumbar regions
short preganglionic, long post ganglionic neurons
parasympathetic
preganglionic neurons orginate in the brainstem and exit via cranial nerves or from the sacral region of the spinal cord
ganglia are mainly located on or near the target organs
long preganglionic, short postganglionic neurons
cranial nerve x (vagus) contains 75% of all parasympathetic neurons
the autonomic nervous system uses a variety of chemical signals (aCH and norepinephrine)
preganglionic always uses acetlycholine (para and symp) onto nicotinic receptors
postganglionic use nicotonic receptors (both in para and symp)
nicotinic=ionotropic
sympathetic pathways uses acetlycholine and norepinephrine
most post ganglionic use norepinephrine onto muscarinic
parasympathetic pathways uses just aCH meaning most of their post ganglionic receptors use acetlycholine onto muscarinic
adrenergic and muscarinic are metabotropic
the adrenal medulla secretes catecholamines
adrenal medulla is a specialized neuroendocrine structure associated with sympathetic nervous system
often described as a modified sympathetic ganglion, contain chromaffin cells (modified ganglion cells no axons and release epinephrine) which are modified postganglionic neurons
sits on top of the kidneys, it has 2 structures the adrenal cortex (true endocrine tissue) and adrenal medulla (neuroendocrine tissue)
autonomic pathways (postganglionic)
target smooth and cardiac muscle, many exocrine glands, a few endorcrine glands, lymphoid tissue, liver and some adipose tissue
autonomic varicosities has a whole bunch of terminals and receptors to cause a larger response in the target tissue
receptors exist across the tissue not under the varicosities, neurotransmitters diffuse
to receptors
varicosities
AP would go through the axon of postganglionic than into the varicosities
like axon terminals, they contain the enzymes necessary to create the neurotransmitters synethize/detachh them
aCH nonpinphrine,
neurotransmitters are synethesized in the axon/varicosities
travels down the axon into a bunch of varicosities
1) AP arrives at varicosity
2) depolarization opens voltaged gated Ca channels
3) Ca entry triggers exocytosis of synaptic vesicles
4) NE (neuroepinphrine) binds to adgrenergic receptor on target
5) receptor activation ceases when NE diffuses away from the synapse
6)NE is removed from the synapse
7) NE can be taken back into synaptic vesicles for re-release
8) NE is metabolized by monoamine oxidase (MAO)
aCH synthesized from choline and acetly CoA
1) acetlycholine is made from choline and acetyl CoA
2) in the synaptic cleft, ACH is rapidly broken down by the enzyme acetylcholinesterase
3) choline is transported back into the axon terminal by cotransport with Na
4) recycled choline is used to make more ACH
no transporter for ACH has to be broken down
autonomic receptors have multiple subtypes
(sympathetic adrenergic)
(parasympathetic cholinergic)
sympathetic adrenergic (NE and E) receptors are all g-protein coupled receptors (metabotropic receptors)
two main categories: alpha (most common) and beta with multiple subtypes
parasympathetic cholinergic (ACH) receptors in target tissues are g-protein coupled receptors: muscarinic receptors
M1, M2, M3
g protein coupled receptors
interaction with ion channels
and interaction with membrane bound enzyme
interaction with ion channels: can lead to opening or closing of channel depending on g protein
interaction with membrane bound enzymes: two main types:
phospholipase C signal transduction pathway -inc in intracellular Ca mediates cellular response
adenylyl cyclase signal transduction pathway -PKA phosphorylates proteins to cause a cellular response
summary of pre and post ganglionic and parasympathetic/sympathetic
autonomic pathwyas consist of pre and postganglioonic neurons in series, with adrenal medulla being the exception
preganglionic acetylcholine and post ganglionic is nictinic receptors
sympathetic: most active uring stressful times
most postgagnlionic is nonpinephrine–> target tissue
adrenergic receptors (beta/alpha)
preganglionic neurons orginate in lumbar and thoracic
ganglia is located just outside spinal cord (paraverterbral)
parasympathetic: most active during rest- and digest
most postganglionic neurons acetlycholine –target tissue muscarnic receptors
peganglionic orginate in brainsttem and sacral region of spine
ganglia located on or near target tissue
