nervous system IV - forebrain, cranial nerves

lecture 17: forebrain diencephalon and telencephalon; cranial nerves

prosencephalon - forebrain (2 sections; five-week embryo)

telencephalon, diencephalon; primary brain vesicle

telencephalon

becomes cerebrum; secondary brain vesicle

diencephalon

forms thalamus, hypothalamus, subthalamus, and epithalamus; secondary brain vesicle

diencephalon function

connects brainstem to the forebrain; located deep within the brain

hypothalamus

primary control center for endocrine system and autonomic nervous system; regulates temperature, hunger, and hormone release

thalamus

situated centrally and bilaterally within the brain (both sides have one); sensory relay station that processes and transmits sensory information to the appropriate areas of the cerebrum

subthalamus

regulates skeletal muscle movements; contains nucleus that is linked functionally to basal ganglia (plats a role in motor control)

epithalamus

involved in regulating emotions and circadian rhythms; contributes to maintaining the body’s internal clock and emotional responses

which signals bypass the thalamus?

olfactory (smell) and gustatory (taste)

thalamic nuclei

rely station for information traveling to and from different parts of the brain

medial group

emotions

anterior group

part of limbic system (memory and emotion)

ventral group

somatosensory output to primary cortex (postcentral gyrus); signals from cerebellum and basal nuclei to motor areas of cortex

lateral group

somatosensory output to association aeras of cortex

posterior group

relay of signals; lateral geniculate nucleus (visual - to occipital lobe) and medial geniculate nucleus (auditory - to temporal lobe)

components of epithalamus

habenula and pineal body

habenula

relay from limbic system to midbrain; helps communication and influences emotional and reward processing

pineal body

endocrine gland that produces melatonin; regulation of the body’s circadian rhythms

hypothalamus connection to limbic system

oversees emotional and behavioral responses with autonomic components (increasing heart rate during stress or fear)

amount of hypothalamus nuclei

11 total - all bilateral

suprachiasmatic nucleus

master circadian clock; influences sleep-wake cycles and other daily physicological processes

mammillary nucleus

memory formation; relay between limbic system and thalamus

dorsomedial nucleus

regulates emotions (rage and other emotions)

hormone secretion nuclei include

arcuate nucleus, medial preotic nucleus, paraventricular, and supraoptic nuclei

lateral hypothalamic area

“feeding center”; geenrates hunger sensations and promotes increased food intake

ventromedial nuclei

“satiety center”; reduce desire to eat; contain glucose-sensing neurons that detect and respond to changes in blood glucose by modifying action potential based on extracellular brain glucose concentration

arcuate nucleus

receives signals from GI tract and adipose tissue (leptin) and regulates both satiety and feeding centers

frontal lobe

planning judgment (“executive functions”: decision-making, impulse control, reasoning), speech production, and voluntary motor control

insula (hidden by other regions)

visceral sensation, empathy

temporal lobe

hearing, smell, verbal, visual, and auditory memory, and language comprehension (wernicke’s area)

occipital lobe

principal visual center of brain

parietal lobe

integrates general senses (pain, temperature, touch, pressure, vibration, and proprioception), and taste information

occipital lobe

principal visual center of brain

how many lobes in the cerebrum?

5 total

association areas

accomplishes cognition (the integration of information) in the cerebral cortex

association trats

connect different regions within the same cerebral hemisphere (intrahemispheric tracts); include long and short fibers

long fibers connect…?

lobes

short fibers connect…?

gyri within a lobe

commissural tracts

cross from one cerebral hemisphere to the other through bridges (ex. corpus callosum)

projection tracts

extend vertically between higher and lower brain and spinal cord centers; fibers of internal capsule arrange in a radiating pattern known as the corona radiata

internal capsule

thick sheet of white matter consisting of projection fibers passing to and from the cerebral cortex

basal nuclei (or ganglia)

group of subcortical nuclei (cluster or neuron cell bodies) responsiblle for motor control; situated deep in the white matter of brain, positioned laterally to thalamus; receive input from sustantia nigra and motor areas of cortex and transmit signals back to these regions to help regulate movement

basal ganglia components

caudate nucleus, putamen, globus pallidus

corpus striatum refers to …?

caudate (head) and putamen

cranial nerves

12 pairs that are part of the PNS (I and II are CNS); all except XI arise from the brainstem

olfactory nerve (I)

sensory, sense of smell

optic nerve (II)

sensory, transmits visual signals from retina to brain

oculomotor nerve (III)

motor; controls extraocular muscles, allowing for precise eyemovements; innervates pupil, lens, and upper eyelid

trochlear nerve (IV)

motor; allows us to look down and more our eyes towards or away from nose

tigeminal nerve (V)

3 branches (opthalamic division - sensory, maxillary divison - sensory, mandibular division - mixed); most important sensory neuron of the face

abducens nerve (VI)

motor; eye movement: lateral vision

facial nerve (VII)

mixed; major motor nerve controlling facial muscles; sensory for tatse; 5 branches (temporal, zygomatic, buccal, madibular, cervial)

vestibulocochlear nerve (VIII)

sensory; hearing and equilibrium

glossopharyngeal nerve (IX)

mixed; innervate pharynx, tongue, parotid gland

vagus nerve (X)

mixed; most extensive distribution of any cranial nerve - supplies the organs of the chest and abdomen; primarily associated with the parasympathetic division of the autonomic NS; major role in control of cardiac, pulmonary, digestive, and urinary function

spinal accessory nerve (XI)

motor; arises from upper spinal cord; controls swallowing and the neck and shoulder muscles

hypoglossal nerve (XII)

motor; controls tongue movements of speech, food manipulation, and swallowing