Flashcards in Test 4 Deck (298):
Embryonic development of the brain:
top of the brain, cerebrum
second part, thalamus and hypothalamus
cerebellum and pons
1. filled with CSF and lined with ependymal cells (neuroglia)
2. ventricles are a continuous tube running through the CNS
3. 2 lateral ventricles
4. septum pellucidum
5. 3rd ventricle
6. interventricular foramen
7. mesencephalic aqueduct
8. 4th ventricle
located in the cerebrum
2 lateral ventricles
separates the 2 lateral ventricles
located in the diencephalon
allows lateral ventricles to communicate with 3rd ventricle
connects 3rd ventricle to 4th ventricle
mesencephalic aqueduct (cerebral aqueduct/aqueduct of Sylvius)
Major areas and structures of the brain:
2. Cerebral hemisphere
3. Cerebral cortex
9. Pituitary gland
10. Brain stem
outer layer of gray matter
80% thalamus, hypothalamus
mesencephalon (midbrain), pons, medulla oblongata
Protection of the brain:
3. Liquid cushion--CSF
4. Blood-brain barrier--ensures the brain's environment remains stable
What are the aspects of the dura mater?
2. double layer of connective tissue--periosteal layer attached to inner surface of the skull and meningeal layer forms the true external covering of the brain and continues to the vertebral canal
3. Dural sinuses are located where two layers are not fused and collect venous blood from the brain and funnel to jugular veins
What are the aspects of arachnoid mater?
1. loose brain covering
2. separated from dura mater by subdural space
3. subarachnoid space separates arachnoid from pia mater--contains CSF and contains largest blood vessels serving the brain (poorly protected)
4. CSF is absorbed into the venous blood of the dural sinuses by the arachnoid villi
What are the aspects of pia mater?
1. clings tightly to the brain
2. anchored by processes of the astrocytes
3. composed of connective tissue and tiny blood vessels
4. external to the CNS
Membranes: dural folds
1. stabilise and support the brain
2. falx cerebri
3. tentorium cerebelli
4. falx cerebelli
projects at the longitudinal fissure, attaches at crista galli inferiorly and to internal occipital crest; encloses the superior sagittal sinus and inferior sagittal sinus
separates the hemispheres of cerebellum from those of cerebrum; encloses the transverse sinus
separates cerebellar hemispheres along the midsagittal line
Protection of the brain: Liquid cushion
1. gives buoyancy to CNS organs--reduces brain weight by 97%
2. protects from blows and trauma
3. may carry chemical signals--hormones
4. arises from blood plasma
5. choroid plexuses form CSF--filters tissue fluid from bloodstream and removes waste
7. circulation--replaces every 8 hours
8. arachnoid granulation
What are the aspects of the hydrocephalus?
1. failure to reabsorb fluid causes build up
2. in infants causes head to enlarge
3. in adults may result in brain damage because the skull is rigid
CSF returned to venous system by:
Protection of the brain: Blood-brain barrier
1. ensures the brain's environment remains stable
2. within most parts of the body, extracellular concentrations of hormones, amino acids, and ions are constantly changing, particularly after eating and exercise
2. Exposure to chemical variations of hormones, amino acids, and ions would cause neurons to fire uncontrollably since they serve as neurotransmitters and ions like K+ can modify threshold for nerves
4. Astrocytes stimulate endothelial cell of the brain capillaries to form tight junction
5. selective barrier rather than absolute barrier
6. nutrients, such as glucose, essential amino acids, and some electrolytes, move by passive transport through the endothelial cell membranes of capillaries
7. Blood-borne metabolic wastes, such as urea and creatinine, as well as proteins, certain toxins, and most drugs, are prevented from entering the brain
8. not well developed in newborns and preemies so toxic substance can readily enter the CNS
Blood-borne substances within the brain's capillaries are separated from the extracellular space and neurons by:
These three conditions do what?
1. the continuous endothelium of the capillary wall
2. a relative thick basal lamina surrounding the external face of the capillary
3. the bulb like "feet" of the astrocytes that cling to the capillaries
help provide tight joints and form "seamless" capillary walls
The blood-brain barrier is ineffective against what?
2. Fat-soluble molecules
3. fatty acids
5. carbon dioxide
Blood-brain barrier absent from the choroid plexuses causes what?
1. The brain allows blood-borne molecules easy access to the neural tissue.
2. The vomiting center of the medulla monitors blood for poisonous substances.
3. The hypothalamus samples the blood to regulate water balance, body temperature, and other metabolic activities.
The brain stem consists of:
1. medulla oblongata
2. Pons varolii
3. Mesencephalon or midbrain
contains vital centers necessary for survival; continuous with the spinal cord
What are the aspects of the medulla oblongata?
1. cardiac center
2. respiratory center
3. vasomotor center
4. Interconnections are made between all the vital centers so that responses of breathing, heart action, and blood pressure are coordinated
5. contains non-vital centers for vomiting, sneezing, coughing, and hiccuping
regulates heartbeat and force of contraction
contains two of the three centers initiating rate and depth of breathing
respiratory center (medullary rhythmicity center)
helps control blood pressure by controlling diameter of muscular blood vessels
What are the cranial nerves in the medulla oblongata that originate from the medulla?
1. Vestibulocochlear nerve-8
2. cochlear branch
3. Glossopharyngeal nerve-9
4. vagus nerve-10
5. accessory nerve-11
6. hypoglossal nerve-12
What are the aspects of the pons varolii?
1. the basal portion of the pons acts as a relay station for motor fibers from the cerebrum to the cerebellum
2. contains the pneumotaxic center
3. contains the apneustic area
inhibits sustained inspiration--contributes to expiration during breathing
sends stimulatory impulses to the respiratory area that activate and prolong inspiration and inhibit expiration
What are the cranial nerves that originate from the pons?
1. Trigeminal nerve-5
2. Abducens nerve-6
3. Facial nerve-7
4. Vestibulocochlear nerve-8
5. vestibular branch
What are the aspects of the mesencephalon/midbrain?
1. contains the cerebral aqueduct, corpora quadrigemina, and cerebral peduncles
2. cerebral peduncles serve as a motor relay station for fibers passing from the cerebrum to the spinal cord, cerebellum, and pons. Also contains sensory fibers that pass from the spinal cord to the thalamus.
3. Integrates visual and auditory reflexes.
4. Monitors certain righting reflexes concerned with maintaining normal posture relative to the eyes and head
5. contains red nucleus
6. contains RAS
What are the visual and auditory reflexes that the mesencephalon integrates?
1. Those concerned with objects seen that are approaching the body and that require muscular response to avoid them
2. Turning the head to achieve the greatest benefit from an auditory stimulus
two pairs of sensory nerves (auditory and visual) nuclei
nerve fiber bundles
blood vessels, subconscious control of upper limb position and muscle tone
helps maintain consciousness
RAS (reticular activating system)
What are the cranial nerves that originate from the midbrain?
1. Oculomotor nerve-3
2. Trochlear nerve-4
The diencephalon consists of:
composes 80% of the diencephalon's "gateway to the cerebral cortex"
The thalamus consists of:
1. intermediate mass
2. thalamic nuclei
projection of gray matter extending into the ventricle
each side is made of this
What are the aspects of thalamic nuclei?
1. Major relay station to the cerebral hemispheres for all types of sensory information, plays a part in the wakefulness or alerting mechanism
2. ventral group
3. medial group
4. anterior group
5. lateral group
6. posterior group
vague awareness of less critical sensory sensations--pain, temperature, touch
conscious awareness of emotions
part of the limbic system concerned with emotion and motivation
helps produce complex reflex movements--especially outward expression of rage and fear
visual and auditory information
What are the structures associated with the hypothalamus?
1. optic chiasma
3. pituitary gland
4. mammillary bodies
crossover area for optic tracts (eye nerves)
connects the hypothalamus to the pituitary gland
functions considered with endocrine systems
relay station for olfactory neurons and olfactory reflexes, 2 rounded structures behind the infundibulum, control reflex movements for chewing, licking, and swallowing
What are the functions of the hypothalamus?
1. it is the main visceral control center
2. it is important in overall body homeostasis
3. it links the nervous and endocrine systems
4. temperature regulation
5. pituitary functions
6. regulation of water balance
7. food intake
8. regulation of gastric secretions
10. maintains the waking state and sleep patterns; exhibits properties of a self-sustained oscillator and acts as a pacemaker to drive many biological rhythms
11. contains thirst center; certain cells in the hypothalamus are stimulated when the extracellular fluid volume is reduced. The stimulated cells produce the sensation of thirst
12. mind-over-body phenomenon
What are the aspects of temperature regulation in the hypothalamus?
1. heat loss--sweating, decreased muscle tone, dilation of skin blood vessels
2. heat gain--skin vessels constrict, shivering, cessation of sweating
What are the pituitary functions of the hypothalamus?
produces Pituitary Regulating Factors which stimulate or inhibit pituitary production and/or release hormones in the anterior pituitary, nine chemicals have been found
What are the aspects of the hypothalamus regulating water balance?
it monitors blood osmotic pressure, produces ADH (antidiuretic hormone) and stimulates release of ADH from the pituitary to regulate tonicity of body fluids
What are the aspects of the food intake of the hypothalamus?
the hunger or feeding center is stimulated by an empty stomach which leads to eating that stimulates the satiety center and inhibits the feeding center
What are the aspects of the hypothalamus regulating gastric secretions?
increased hypothalamic stimulation results in increased gastric juice production, emotion may trigger release of gastric juices when there is no food present, which may lead to ulcer formation
What are the aspects of emotion in the hypothalamus?
expression (somatic patterns) of reactions of rage, pain, pleasure, anger, and sexual arousal, subconscious skeletal muscle control; ANS response--increased blood pressure, sweating, etc.
The hypothalamus is:
one of the last CNS areas to mature and because it controls temperature, premature babies have trouble controlling loss of body heat
What are the aspects of the cerebellum?
1. Second largest part of the brain
2. Externally consists of gray matter; internally consists of white (myelinated) matter
4. Covered in a layer of neural cortex
6. Arbor vitae
bands of cortex
white matter of cerebellum
List the functions of the cerebellum:
1. Operates at the conscious and subconscious level--continually compares higher brain intentions with body performance and makes corrections
2. Coordinates muscular activity, integrates muscular movement, and predicts when to stop movements
3. Coordinates reflexes that serve to maintain posture and equilibrium. The sensory impulses involved in these reflexes come from recepters, called proprioceptors, that are found in muscles, tendons, and from special sense organs such as the eyes and ears. The inner ear sends information to the cerebellum concerning equilibrium, and it in turn coordinates balance.
4. Damage to the cerebellum results in tremors, loss of muscle tone, loss of equilibrium, inaccurate movements of voluntary muscles, and reeling walk.
What are the aspects of the cerebrum?
1. It is our conscious mind.
2. It is the largest part of the brain comprising 83% of the total brain.
3. It is divided into lobes.
4. It consists of two cerebral hemispheres connected by the corpus callosum.
5. The surface of the cerebrum has ridges called gyri separated by grooves.
What are the lobes in the cerebrum?
1. Frontal lobes
2. Parietal lobes
3. Temporal lobes
4. Occipital lobes
5. Island of Reil (Insula)
located deep within the brain and is covered by parts of the frontal, parietal, and temporal lobes. It is separated from these lobes by a circular sulcus. It is the area for the sense of taste.
Island of Reil (Insula)
Surface of the cerebrum:
1. Precentral gyrus
2. Postcentral gyrus
3. Front and behind central
Shallow grooves are called:
deep grooves are called:
What are the grooves/sulci of the cerebrum?
1. Longitudinal fissure
2. Transverse fissure
3. Central sulcus
4. Lateral sulcus
separates the two hemispheres
separates cerebral hemispheres from the cerebellum
separates frontal from parietal lobe
outlines temporal lobe
island of cortex buried deep within the lateral sulcus; area for sense of taste
3 regions of the cerebral hemisphere:
1. Superficial cortex of gray matter
2. internal white matter
3. Basal nuclei
islands of gray matter deep in the white matter
consists of neuron cell bodies, dendrites, unmyelinated axons--no fiber tracts
cerebral cortex (gray matter)
What are the aspects of cerebral white matter?
1. Communication between cerebral areas and between cerebral cortex and lower CNS centers.
2. Consists of myelinated fibers bundled into large tracts.
What are the bundles of myelinated fiber in cerebral white matter?
1. Association fibers
3. Projection fibers
What are the aspects of association fibers?
1. Connect different parts of the same hemisphere
2. arcuate fibers
3. longitudinal fasciculi
4. run horizontally
short, connect adjacent gyri
long, are bundled into tracts and connect different lobes
What are the aspects of commissures?
1. Connect the two hemispheres
2. Ex.: corpus collosum deep within the longitudinal fissure
3. runs horizontally
What are the aspects of projection fibers?
1. Fibers entering the cerebral hemisphere from lower brain or cord centers and fibers leaving cortex to travel to lower centers.
2. All projection fibers must pass through the diencephalon.
3. Tie the cortex to the rest of the nervous system and to receptors and effectors of the body.
What are the aspects of basal nuclei?
1. deep in the white matter of cerebrum are subcortical nuclei
2. Control activities at a subconscious level
3. May play a role in regulating attention and in cognition
4. Important in starting, stopping, and monitoring movements executed by cortex; Ex.: arm swinging, walking, also intensity
5. inhibit antagonistic or unneccessary movements
6. Disorders of basal nuclei result in either too much or too little movement as in Huntington's disease and Parkinson's disease
What are the aspects of the limbic system?
1. It is a functional brain system with networks of neurons that work together but span relatively large distance.
2. It is located on the medial aspect to each cerebral hemisphere and diencephalons.
4. System integrates and responds to a wide variety of environmental stimuli like odors
5. output relayed by hypothalamus
6. interacts with the prefrontal lobes so there is a relationship between our feelings and our thoughts, i.e. we react emotionally to things we consciously understand to be happening and are consciously aware of emotional richness of our lives
linnks the limbic system regions together
Communication between the cerebral cortex and limbic system explains:
why emotions sometimes override logic and why reason can stop us from expressing our emotions inappropriately
General characteristics of cerebral function:
1. The two sides are not equal in function--areas are unequal and upside down (as in face and hand regions of the brain)
2. Each hemisphere is concerned with sensory and motor function of opposite side of body
3. Three functional areas.
4. No functional area acts alone.
What are the three functional areas of cerebral function?
1. Motor areas--voluntary
2. Sensory areas
3. Association areas--integration
What are the parts of the motor areas in cerebral function?
1. Primary (somatic) motor cortex
2. Premotor cortex
3. Frontal eye field
What are the aspects of the primary motor cortex?
1. Located in the precentral gyrus of frontal lobe of each hemisphere
2. Pyramidal cells allow for voluntary movements of skeletal muscles. Long axons which project to spinal cord from large voluntary motor tracts called pyramidal or corticospinal tracts.
3. Most neurons in these gyri control muscles in body areas having the most precise motor control.
4. More area is given to those body parts where skilled or complex movement is required; ex. face, tongue, hands
5. Current research indicates that a given muscle is controlled by multiple spots on the cortex and individual cortical motor neurons actually send impulses to more than one muscle; i.e. individual motor neurons control muscles that work together in a synergistic way--kicking a soccer ball
What are the aspects of the premotor cortex?
1. anterior to precentral gyrus in frontal lobe
2. controls learned motor skills such as writing, playing musical instrument
3. coordinates eye and head movements
4. memory bank of skilled activities
What is an aspect of the frontal eye field?
controls voluntary movements of the eyes
Damage to the primary motor cortex:
paralyses the body muscles controlled by those areas--right hemisphere affects left side of the body. Only voluntary control is lost.
Damage to the premotor cortex:
loss of motor skills programmed in that region; ex. ability to type
What are the parts of the sensory areas in cerebral function?
1. Primary somatic sensory area
2. Visual areas
3. Auditory area
4. Olfactory area
5. Gustatory area
What are the aspects of the primary somatic sensory area?
1. Found in the postcentral gyrus of the parietal lobe.
2. Interprets most of the skin sensations--heat, cold, touch, pressure, and some pain
3. Receives information from the general sensory receptors located in the skin and from proprioceptors in skeletal muscles
4. Amount of sensory cortex devoted to a body region is dependent on the area's sensitivity--i.e. face and fingertrips are the most sensitive in humans
5. Responsible for comprehending what we touch
What are the aspects of the visual areas?
1. occipital lobe
2. receives impulses from the eyes and interprets shape, colour, and movement
3. primary and association areas
4. Damage to primary visual area results in blindness, but damage to visual association area can see but not comprehend what they are looking at
What are the aspects of the auditory area?
1. Primary and association areas
2. Temporal lobe
3. receives impulses from the cochlea of the inner ear
4. interprets the basic characteristics of sound such as pitch and rhythm
5. memories of sounds heard in the past stored here
What are the aspects of the olfactory area?
1. temporal lobe
2. interprets sensations of smell
What are the aspects of the gustatory area?
1. interprets sensations of taste
2. parietal lobe
Areas from which specific responses or sensations cannot be elicited when they are stimulated. These areas are related to memory, reasoning, verbalising, judgment, and emotional feelings.
List the parts of the association areas:
1. Prefrontal area
2. General interpretative area (Wernick's area or Temporal Association Area)
3. Broca's Speech area
4. Occipital association area
5. Parietal association area
concerned with higher intellectual processes--concentration, planning, complex problem solving, judgment; most complicated cortical region; closely linked to emotional part of the brain
concerned with interpretation of complex sensory experiences, visual and auditory memories--reading printed words, memory of visual scenes, music; generally found on the left side only
General Interpretative Area (Wernick's Area or Temporal Association Area)
What are the aspects of Broca's Speech Area?
1. In the temporal lobe
2. Includes parts of the motor, sensory, and auditory area
3. Present in one hemisphere only (left)
4. Concerned with the translation of thoughts into speech
Important in combining visual images with other sensory experiences; necessary, for instance, when one person recognises another person or object
occipital association area
concerned with interpretation of size, shape, texture, and the degree of heat of objects touched. It is also going to aid in understanding speech and choosing words needed to express thoughts and feelings.
parietal association area
Contains general interpretative and speech centers; analytical tasks; often called the dominant hemisphere. Also more important for right-handed control, spoken and written language, numerical and scientific skills, and reasoning in most people.
Interprets sensory information; emotions. Also more important for left-handed control, musical and artistic awareness, space and pattern perception, insight, imagination, and generating mental images of sight, sound, touch, taste, and smell in order to compare relationships (fun test)
What are the aspects of cranial nerves?
1. The brain gives rise to 12 pairs of cranial nerves (10 originate from the brain stem). These nerves supply motor and sensory fibers to structures in the head, neck, and shoulder regions and one pair that supplies fibers to the body viscera.
2. Designated by the number and a name. The number indicates the order in which the nerve arises from the front to the back of the brain, and the names describe their primary functions or general distribution of their fibers.
List the disorders of the nervous system:
1. Cerebral palsy
2. Multiple sclerosis
3. Cerebral vascular accident (stroke or cerebral apoplexy)
5. Alzheimer's Disease
6. Parkinson's Disease
7. Huntington's Disease
8. Transient Ischemic Attack (TIA)
9. Amyotropic Lateral Sclerosis
11. Reye's Syndrome
motor disorder caused by damage to the motor areas of the brain during fetal life, birth, or infancy, can be caused by German measles (Rubella) during the first three months of pregnancy; characterised by partial paralysis and lack of muscular coordination, it is irreversible, about 70% of victims appear to be mentally retarded but are not.
a disease of the CNS characterised by loss of myelin and the appearance of scar-like patches throughout the brain and spinal cord or both, impulse transmission is interrupted, the onset age is usually between the ages of 20 and 40, affecting females more than males (2X), death occurs from 7-30 years later, it is an autoimmune disorder
characterised by blockage of blood vessels to the brain such as hemorrhage, thrombosis, and atherosclerosis; most common brain disorder
cerebral vascular accident/stroke/cerebral apoplexy
the second most common disorder of the brain, characterised by temporary disturbances in normal brain impulses, may be accompanied by convulsive seizures and loss of consciousness, almost never affecting intelligence
associated with shortage of ACh and structural changes in the brain, particularly in the associative area; gyri shrink and neurons are lost, results in dementia, intellectual impairment, and personality changes; it is irreversible
occurs in older individuals resulting in tremors and muscle rigidity to lesion in the midbrain, the cause is unknown, the cells in the area stop producing dopamine, treatment is through the administration of levodopa, the patient's brain produces too much ACh, surgical destruction of a part of the cerebrum helps to stop some of the tremors and rigidity
hereditary disease, massive degeneration of basal nuclei and later the cerebral cortex, over stimulation of motor drive
temporary cerebral dysfunction caused by impaired blood flow to the brain, the attack usually persists for 5 to 10 minutes and only rarely lasts long as 24 hours, estimated that about 1/3 of patients that experience this will have a stroke within 5 years
Transient Ischemic Attack (TIA)
destruction of anterior horn and pyramidal tracts, loss of swallowing, speech, and difficulty breathing--does not affect intelligence--Stephen Hawking has this
Amyotropic Lateral Sclerosis
in babies the mesencephalon or diencephalons fail to develop, baby appears to be normal (movements, eating, following fingers) but death will occur within days to months
seems to occur following a viral infection, particularly chickenpox or influenza, aspirin at normal doses is believed to be a risk factor in the development of this, the majority of persons affected are children or teenagers, characterised by vomiting, brain dysfunction, and liver damage
involves an inability of an individual to comprehend written language, letter in words seem transposed, reversed, or upside down
respond to changes in the environment, both internal and external; each type is sensitive to a specific stimuli
area monitored by a specific receptor; the larger the field, the less fine tuned the sensation
awareness of stimuli, arriving information
interpretation of meaning of a stimulus, conscious awareness
Sensory receptors can be classified by:
1. Structural complexity
2. Stimulus type
Structural complexity: Simple
Structural complexity: Complex
sense organs- vision, hearing, smell, and tastes
What are the aspects of complex structural complexity?
2. peripheral adaptation
3. central adaptation
4. One type of sensory receptor that does not adapt is the proprioceptor
5. tonic receptors
6. phasic receptors
reduction in sensitivity in presence of constant stimuli, can be adjusted conscious or subconscious (say listen up then tend to)
sensory receptors subjected to an unchanging stimulus become less responsive over time; that is they adapt; give example
peripheral adaptation, ex. thermoreceptors
conscious awareness of a stimulus disappears; restricts info reaching the CNS; reduces reception of the stimulus; give example
central adaptation, ex. odors, pain
always active; increase or decrease in stimulus changes rate of action potential generation; slow adapting; give example
tonic receptors, ex. nociceptors
normally inactive, but become active when changes in condition occur; fast adapting receptors; give example
phasic receptors, ex. thermoreceptors
List the stimulus types:
generate nerve impulses when deformed by touch, pressure, vibration, or stretch; give example
mechanoreceptors, ex. hair cells
What are the 3 classes of mechanoreceptors?
1. tactile receptors
touch, pressure, vibration
What are the 6 types of tactile receptors?
1. Free nerve endings
2. Root hair plexus
3. Tactile discs
4. Tactile corpuscles
5. Lamellated corpuscles
6. Ruffini corpuscles
Tactile receptor: tonic, large field, touch and pressure
free nerve endings
Tactile receptor: phasic, movement of hair
root hair plexus
Tactile receptor: Merkels, tonic, small field, fine touch
Tactile receptor: Meissner's, phasic, fine touch, pressure, and texture
Tactile receptor: Pacinian, phasic, deep pressure, visceral
Tactile receptor: tonic, pressure and distortion of skin or joints
detect pressure changes in wall of blood vessels and structures of urinary, reproductive, and digestive tracts
monitor body position, no adaptation
What are the aspects of proprioceptors?
1. muscle spindles
2. Golgi tendon organs
3. Receptors in joint capsules, movement, pressure, tension
found in skeletal muscles to monitor stretch
pick up tension in a tendon, similar to Ruffini in structure
Golgi tendon organs
sense changes in temperature, 3-4X more cold than hot, phasic
sense changes in chemical concentration dissolved in fluid
cause the sensation of pain, tonic
What are the aspects of nociceptors?
1. Fast pain
2. Slow pain
Type A fibers, prickling pain
Type C fibers, burning or aching
Overstimulation of any type of receptor:
Sensory receptor locations:
receive stimuli from outside the body, most found near the body surface and include touch, pressure, temperature, pain, and most receptors of the special senses
respond to stimuli from inside the body, viscera and blood vessels, chemical changes, temperature, and stretch, sensations of pain
List the aspects of somatic sensory pathways:
1. First order neuron
2. Second order neuron
3. Third order neuron
4. Ascending tracts
carries impulse to the CNS; cell body in dorsal root ganglion or cranial nerve ganglion
first order neuron
located in spinal cord or brain stem; interneuron which synapses with a first order neuron; at some point crosses over to opposite side of CNS (decussion); so the right side of the brain controls left side of body and vice versa
second order neuron
located in the thalamus; synapses with a second order neuron
third order neuron
Tracts of the spinal cord:
1. conduct impulses between the peripheral nerves and the brain
2. can tell where to begin and end by name, ex.: spinocerebellar --> begin in spinal cord and end in the cerebellum
List the ascending pathways:
1. anterolateral pathway
2. spinocerebellar pathway
3. posterior column pathway/dorsal white column
List the two parts of the anterolateral pathway:
1. lateral spinothalamic tract
2. anterior spinothalamic tract
List the two parts of the spinocerebellar pathway:
1. posterior spinocerebellar tract
2. anterior spinocerebellar tract
List the two parts of the posterior column pathway (dorsal white column):
1. fasciculus gracilis
2. fasciculus cuneatus
first order neurons synapse on second order neurons in the posterior gray matter and cross over before ascending; synapse with third order neurons in the thalamus
pain and temperature
lateral spinothalamic tract
crude touch and pressure
anterior spinothalamic tract
muscle tone and posture; info arrives at the cerebellar cortex, not conscious awareness
axons do not cross over
posterior spinocerebellar tracts
most axons do cross over
anterior spinocerebellar tracts
first order neurons reach CNS through dorsal roots of spinal nerves and sensory roots of cranial nerves; second order neurons ascend and cross over at brain stem and synapse with third order neurons in the thalamus; fine touch, pressure, two-point discrimination, body position; info comes from skin, muscles, tendons, and joints
posterior column pathway (dorsal white column)
inferior half of spinal tracts in posterior white column
superior half of spinal tracts in posterior white column
What are the aspects of the somatic motor system?
1. controls skeletal muscles (somatic nervous system)
2. Somatic motor pathways
3. Upper motor neuron (cell body located in the CNS) --> lower motor neuron (cell body in nucleus of brain stem or spinal cord) --> motor unit in skeletal muscle
Somatic sensory pathways are:
Somatic motor system is made of:
List the descending pathways:
1. corticospinal pathway
2. medial and lateral pathways
List the parts of the corticospinal pathway:
1. corticobulbar tracts
2. corticospinal tracts
List the parts of the corticospinal tracts:
1. lateral corticospinal tracts
2. anterior corticospinal tracts
List the parts of medial pathways:
1. vestibulospinal tract
2. tectospinal tracts
3. reticulospinal tract
List the parts of lateral pathways:
1. rubrospinal tract
pyramidal system, 3 parts
synapse with lower motor neurons in cranial nerves III-VII, IX, XI, XII, conscious control over skeletal muscles of eye, jaw, face, neck, and pharynx
synapse on lower motor neurons in anterior gray matter horns of spinal cord
cross over at top of spinal cord right after the medulla (in some cases in the medulla), along pyramids, 85% of axons cross over descending to this tract
lateral corticospinal tracts
axons cross over at the anterior white commissure synapse anterior gray horns lower in the spinal cord
anterior corticospinal tracts
control of gross movements of trunk and proximal limbs to maintain balance and posture
in spinal cord to maintain balance
superior and inferior colliculi in brain, visual and auditory, ends in the neck to control the head mostly
network in brain stem to maintain muscle tone while conscious
control of upper distal limb muscles
involuntary impulses to skeletal muscles concerned with tone and posture, extend only into cervical spinal cord, not as extensive as in other mammals
What are the aspects of motor and sensory homunculus?
1. Graphical representation of motor or sensory areas of the brain
2. Areas of primary cortex that result in contraction of corresponding muscles (motor) or areas of sensory processing (sensory)
3. Disproportionate to actual size of area, ex. lot of area for hands
What are the aspects of basal nuclei?
1. deep in the white matter of cerebrum are subcortical nuclei
2. do not control lower motor neurons but adjust activity of upper motor neurons
3. axons may synapse on thalamic neurons or in the reticular formation
4. important in starting, stopping, monitoring movements and their intensity executed by the cortex; ex. walking, running, arm swinging
5. normally, the tracts leaving the basal nuclei have inhibitory effect on upper motor neurons
6. inhibit antagonist or unneccessary movements
7. Disorders of basal nuclei result in either too much or too little movement as in Huntington's chorea and Parkinson's disease
Comparison of somatic and autonomic nervous systems:
1. Somatic motor division lacks ganglia
2. All somatic motor neurons release ACh and the effect is always excitatory
3. Post ganglionic autonomic fibers release norepinephrine (most sympathetic fibers) or ACh (parasympathetic fibers) and the effects are either excitatory or inhibitory
4. Adrenal medulla secretions supplement sympathetic division
5. Embryologically adrenal medulla and sympathetic ganglia arise from the same tissue
6. All autonomic motor pathways consist of two motor neurons in series as opposed to somatic with one motor pathway which results in slower conduction
The autonomic nervous system innervates:
smooth and cardiac muscle and glands to regulate activity
The ANS is the motor subdivision of:
the peripheral nervous system
Is the ANS voluntary or involuntary?
involuntary and without conscious control
To operate the ANS depends on:
a continual flow of sensory input (autonomic sensory neurons) from the visceral organs and blood vessels into integrating centers in the CNS
Structurally the ANS includes:
autonomic sensory neurons, integrating centers in the CNS, and autonomic motor neurons
The ANS was originally named autonomic because:
it was thought to function autonomously or in a self-governing manner without control by the CNS
What are the 3 aspects of ANS control?
1. The ANS is regulated by centers in the brain, mainly the hypothalamus and brain stem
2. The hypothalamus and brain stem receive input from the limbic system and other regions of the cerebrum
3. The limbic system is found encircling the upper part of the brain stem and the corpus callosum. It is found on the inner border of the cerebrum and the floor of the diencephalons.
The main input to the ANS comes from:
autonomic sensory neurons
Autonomic sensory neurons are associated with:
interoceptors, such as chemoreceptors that monitor blood CO2 levels and mechanoreceptors that detect the degree of stretch in the walls of organs or blood vessels
What are the aspects of interoceptors?
1. They are located in blood vessels and viscera
2. They provide information about the internal environment
3. They transmit sensations such as pain, pressure, fatigue, hunger, thirst, and nausea from within the body
Autonomic sensory signals are not:
consciously perceived most of the time
Intense activation of interoceptors may give rise to:
regulate visceral activities by either increasing (exciting) or decreasing (inhibiting) ongoing activities in their effector tissues
autonomic motor neurons
List the autonomic motor neurons:
1. Preganglionic neurons
2. Ganglionic (postganglionic) neurons
What are the aspects of autonomic motor neurons?
1. Unlike skeletal muscle, cardiac and smooth muscle generally function even if their nerve supply is interrupted, ex. the heart continues to beat when it is removed for transplantation into another person
2. All autonomic motor pathways consist of two motor neurons in a series, that is, one following the other
What are the aspects of preganglionic neurons?
1. Visceral motor neurons in CNS
2. Perikaryon (body) in the CNS
3. Axon is small in diameter and exits the CNS as part of a cranial or spinal nerve
5. Extend from the CNS to the autonomic ganglion
6. Preganglionic fibers = axons; leaves the CNS and synapses on ganglionic neurons
What are the aspects of postganglionic neurons?
1. Perikaryon is in the autonomic ganglion
2. Found completely outside the CNS
3. Unmyelinated and small axon
4. Extends to the effector organ
5. Postganglionic fibers = axons of ganglionic neurons; extend to peripheral target organ
Examples of autonomic responses:
1. Changes in the diameter of the pupil
2. Dilation and constriction of blood vessels
3. Adjustment of the rate and force of the heartbeat
4. Increased or decreased secretions of glands
Can autonomic responses be altered?
Most autonomic responses cannot be consciously altered or suppressed to any great degree.
1. You probably cannot voluntarily slow your heartbeat to half of its normal rate on command but this can be done through yoga or other techniques of meditation
2. Some autonomic responses are the basis for polygraph tests
The ANS is divided into:
Sympathetic and parasympathetic divisions
Most organs in the ANS have:
dual innervation--they receive impulses from both sympathetic and parasympathetic neurons
What are aspects of impulses in the ANS?
1. In general, nerve impulses from one division stimulate the organ to increase its activity (excitation) whereas impulses from the other division decreases the organ activity (inhibition); ex. sympathetic impulses will increase the heart rate; sympathetic impulses decrease the heart rate
Fight or flight system
Sympathetic division (Thoracolumbar)
What are the aspects of the thoracolumbar (sympathetic) division?
1. Preganglionic neurons have their perikaryons in the lateral horns of the gray matter in the 12 thoracic segments and the first two lumbar segments of the spinal cord.
2. Most organs have dual innervation.
3. Preganglionic fibers enter the adrenal gland and synapse with neuroendocrine cells, which secrete hormones (epinephrine and norepinephrine)
What are the steps in the general pattern of a sympathetic response?
1. Increased heart rate and blood pressure
3. Decreased digestive and urinary activity
4. Increased respiratory rate
5. Increased energy demand
List the sympathetic pathways:
1. Sympathetic chain ganglion
2. Collateral ganglia
3. Adrenal medulla
preganglionic fiber will synapse in one or more sympathetic chain ganglia (head, thoracic cavity, body wall)
sympathetic chain ganglion
What are the aspects of collateral ganglia?
1. Innervate abdominopelvis viscera
2. Preganglionic fibers pass through sympathetic chain ganglia without synapsing but then synapse at collateral ganglia
3. Splanchnic nerves
preganglionic fibers that innervate collateral ganglia
What are the 3 collateral ganglia?
1. Celiac ganglia
2. Superior mesenteric ganglion
3. Inferior mesenteric ganglion
Collateral ganglia that are in the stomach, liver, gallbladder, pancreas, and spleen
Collateral ganglia that are in the small intestines, and some larger intestines
superior mesenteric ganglia
Collateral ganglia that are in the large intestines, kidney, bladder, and sex organs
inferior mesenteric ganglia
resting and digesting system
parasympathetic division (craniosacral)
What are the aspects of the craniosacral (parasympathetic) division?
1. Preganglionic neurons have their perikaryons in the nuclei of cranial nerves III (oculomotor), VII (facial), IX (glossopharyngeal), and X (vagus) in the brain stem and in the lateral horns of gray matter of the S2-S4 segments of the spinal cord
2. Major portion is controlled by the vagus nerve (75%)
3. Effects are very localised
What are the patterns of response in the craniosacral (parasympathetic) division?
1. Increased salivary and digestive secretions
2. Decreased heart rate and blood pressure
3. Increased digestive and urinary function
What are aspects of visceral reflexes?
1. Unlike somatic reflex, they have a two motor neuron chain, polysynaptic
2. ANS has sensory fibers, mostly visceral pain afferents
3. These travel along the same pathways as somatic pain fibers
4. Helps explain referred pain--pain stimuli arises in the viscera but is perceived as somatic in origin; ex. heart attack--chest and left arm pain
5. Long time to respond = CNS involved
6. Short time to respond = no CNS involvement
ANS neurotransmitter and receptors are classified (based on the neurotransmitter they produce) as either:
1. Cholinergic synapse
2. Adrenergic synapse
What are the aspects of cholinergic synapses?
1. Release ACh
2. Synaptic terminals are branching with varicosities
3. Effects are short lived because ACh is inactivated by acetylcholinesterase
4. Cholinergic receptors are found in the postsynaptic cell membrane
Cholinergic synapse neurons include:
1. All sympathetic and parasympathetic preganglionic neurons
2. Sympathetic ganglionic (post) neurons that innervate most sweat glands
3. All parasympathetic (post) neurons
What are the two types of cholinergic receptors?
1. Nicotinic receptors
2. Muscarinic receptors
What are the aspects of nicotinic receptors?
1. Always stimulatory
2. Present in the cell membrane of dendrites and perikaryons of sympathetic and parasympathetic ganglionic (post) neurons and the neuromuscular junction
3. Named because nicotine mimics the action of ACh by binding to these receptors
What are the aspects of muscarinic receptors?
1. Can be inhibitory or excitatory
2. Present in the cell membrane of all smooth muscle, cardiac muscle, and glands innervated by parasympathetic postganglionic axons
3. Named because a mushroom poison (muscarine) mimics the actions of ACh by binding to them
Nicotine does not activate muscarine receptors, and muscarine does not activate nicotinic receptors, but:
ACh does activate both types of cholinergic receptors
What are the aspects of adrenergic synapses?
1. Release neurotransmitter norepinephrine
2. Found in most sympathetic ganglionic neurons
3. Norepinephrine is inactivated by monoamine oxidase (MAO)
4. Norepinephrine binds to adrenergic receptors on the postsynaptic membrane causing either an excitatory or inhibitory response by the effector cell
5. Adrenergic receptors bind to both norepinephrine and epinephrine
6. Receptors are activated by NE released as a neurotransmitter by the sympathetic ganglionic neurons and by E and NE releases as hormones by the adrenal gland
What are the different adrenergic receptors?
1. Alpha receptors
2. Beta receptors
What are the subtypes of alpha receptors?
Alpha1 and Alpha2
What are the subtypes of beta receptors?
Beta1, Beta2, and Beta3
What are the aspects of adrenergic receptors?
1. Generally activation of Alpha1 and Beta1 receptors produces excitation
2. Generally activation of Alpha2 and Beta2 receptors causes inhibition
3. Beta3 receptors are present only on cells of brown adipose tissue (more widespread in the fetus and infant), where their activation causes thermogenesis
4. Cells of most effectors contain either alpha or beta receptors (some visceral effector cells contain both)
5. NE stimulates alpha-receptors more strongly than beta-receptors
6. Ephinephrine is a stimulator of both alpha and beta receptors
What are the aspects of NE stimulating alpha-receptors more strongly than beta-receptors?
1. The activity of NE at a synapse is terminated either when NE is taken up by the axon that released it or when it is enzymatically inactivated by either catechol-O-methyltranferase (CMOT) or monoamine (MAO)
2. Compared to ACh, NE lingers in the synaptic cleft for a longer period of time, especially in response to release by the adrenal medulla since blood has no MAO
What are aspects of beta-blocker drugs?
1. adrenergic blocker
2. Used to reduce blood pressure and prevent arrythmias
3. Most have an effect on Beta1 receptors
4. By blocking the Beta1 receptors the drug will decrease the heart rate and force of contraction and this will result in a decrease of blood pressure
What are the aspects of anticholinergics?
2. blocks parasympathetic effects
3. given before surgery to prevent salivation and to dry up respiratory system
What are the aspects of tricyclic antidepressants?
2. relieve depression by prolonging the activity of NE on the postsynaptic membrane
may result from overactive sympathetic vasoconstrictor response due to continuous high levels of stress
Effects of aging on the ANS:
1. efficiency decline
2. Structural changes in preganglionic axonal terminals that become congested with neurofilaments
What are the higher order functions?
What are the two types of memory?
1. Fact memories
2. Skill memories
memory that deals with color and smell
memory that deals with learned motor skills
What are the classes of memory?
1. short-term memories
2. long-term memories
class of memory that deals with primary, small bits
What are the types of long-term memories?
1. secondary memories
2. tertiary memories
long-term memory that is hard to recall after much time passes
long term memory that is part of consciousness
What are the aspects of memory storage?
1. memory consolidation
2. long-term memory storage in cerebral cortex
3. Information about a subject is stored in different areas of the brain
conversion of short-term memory to long-term memory; amygdala and hippocampus are essential
What are the two types of amnesia?
loss of memory of past events
inability to store new long-term memories; keeps old memories (valium, halcion)
alert, aware of external environment
varying states of unresponsiveness
What are the two aspects of unconsciousness?
unconscious but can be awakened
reticular activating system (RAS)
What are the types of sleep?
1. Deep sleep
2. REM sleep
slow wave, respiratory, heart, and blood pressure decline by 30%