Ch 8 Flashcards
Central Nervous System
spinal cord an brain
- receives input from sensory neurons –> motor neurons that innervate muscles/glands
- association neurons: integrate sensory info and help direct responses to maintain homeostasis/respond to the environment
Gray Matter
- unmyelinated nerve cell bodies (clusters = nuclei)
- dendrites
- axon terminals
White Matter
- myelinated axons
- -> tracts
- contains very few cell bodies
What are clusters of cell bodies in CNS called?
nuclei
What are tracts?
axon bundles connecting CNS regions
Brain
- gray matter forms the cortex + deep nuclei
- white matter is deep forming tracts
- adult brain: 100 billion neurons
- receives 15% of total body blood flow
- -> cerebrum, diencephalon, midbrain, hindbrain
Choroid Plexuses
consists of simple cuboidal to columnar epithelium in close association w/blood capillaries
- projects into the roofs of the ventricles (where fluid is)
- secrete CSF into ventricles and central canal of the cord
CSF
secreted from choroid plexuses
- ->made from blood and returned to blood
- not part of circulation
- composition is different than blood
- turned over rapidly
Cerebrum
- largest portion of the brain (80% of mass)
- responsible for higher mental functions
- consists of right/left cerebral hemisphere –> connected by corpus callosum
Cerebral Cortex
- outer region: composed of gray matter w/underlying white matter
- gyri + sulci = convolutions
- each hemisphere is divided into 5 lobes (frontal, parietal, temporal, occipital, insula)
Frontal/Parietal Lobes
-separated by central sulcus
- pre central gyrus:
- on frontal lobe
- motor control
- neurons called upper motor neurons - post central gyrus:
- on parietal lobe
- somatesthetic sensation (where we are in space)
- ->called somatosensory cortex
Temporal Lobe
auditory centers
Occipital Lobe
vision and coordination of eye movements
Insula
encoding of memory and integration of sensory info w/visceral responses
-receives olfactory, gustatory, auditory, and pain info
Cerebral Lateralization
- each side of pre central gyrus controls movements on the contralateral (opposite) side of body
- somatesthetic sensation from each side of body projects to contralateral sides of post central gyrus
- communcaiton between the sides occurs through the corpus callous
Corpus Callosum: right hemisphere
controls visuospatial tasks, recognizing faces, composing music
Corpus Callosum: left hemisphere
controls language, speech, writing, calculations
Limbic System
-group of brain regions responsible for emotional drives
What are the areas of cerebrum?
cingulate gyrus amygdala hippocampus septal nuclei anterior insula --> hypothalamus and thalamus (in the diencephalon) are part of the system
What emotions are controlled by the limbic system?
Aggression: areas of amygdala and hypothalamus
Fear: amygdala and hypothalamus
Hunger/satiety: hypothalamus
Sex Drive: whole system
Goal-directed behaviors: hypothalamus and other regions
Diencephalon
- part of forebrain
- includes: epithalamus, thalamus, hypothalamus, part of pituitary gland, and third ventricle
- surrounded by cerebral hemispheres
- regulates glands/hormones
Hypothalamus
*important for maintaining homeostasis and regulated autonomic system
Hypothalamus contains centers for…
LOTS of functions
- hunger/satiety and thirst
- regulation of body temp, sleep, and wakefulness
- sexual arousal and performance
- emotions of fear, anger, pain, and pleasure
- control of endocrine system
- controls hormone secretion from the pituitary gland
Regulation of Pituitary Gland
- ADH: regulated urine concentration
- Oxytocin: important in reproduction
- -> transported along hypothalami-hypophyseal tract to posterior pituitary gland (extension of neural tissue), where stored until needed
- hypothalamus produces releasing hormones and inhibiting hormones that are transported to the anterior pituitary via circulation to regulate secretion of pituitary hormones
Hindbrain
- composed of mesencephalon (pons and cerebellum) and myelencephalon (medulla oblongata)
- -> ons houses sensory/motor tracts heading from/to the spinal cord and respiratory centers
Cerebellum
- 2nd largest brain structure: gray matter outside, white matter inside
- receives input from proprioceptors which sense joint angle, muscle length, and tension
- works w/basal nuclei and motor cortex to coordinate movement
- needed for motor learning and proper timing and force required to move limbs in specific task
Myelencephalon
- made up of the medulla oblongata
- all ascending/descending tracts between brain and spinal cord pass through medulla
- contains nuclei required for regulation of breathing and CV response = vital centers
1. Vasomotor control: controls blood vessel diameter
2. Cardiac control center: controls HR
3. Respiratory center: works w/areas in the pons to control breathing
Spinal Cord
-composed of white matter surrounding a gray matter core
- gray matter is arranged with left/right dorsal horn and left/right ventral horn
- -> dorsal root carries sensory info, ventral root is where motor info is exiting to muscles/glands
-white matter composed of ascending/descending fiber tracts
Ascending Tracts
convey sensory info from receptors in skin, muscles, joins, and organs
-crossover of tracts (decussation) may occur in spinal cord or in medulla = contralateral
Descending Tracts
Two groups
- Corticospinal/Pyramidal: descend directly w/o synaptic interruption from cerebral cortex to the spinal cord (no synapse)
- Extrapyramidal tracts: originate in ain stem and are controlled by motor circuits of the corpus striatum, substantial nigra, and thalamus
Cranial Nerves
- part of PNS
- nerves that arise directly from nuclei in brain
- 12 pairs
- most are mixed nerves
- -> associated with vision, olfaction, and hearing are sensory only and have their cell bodies in ganglia located near the sensory organ
