Anatomy: Nervous System Part 2

Telencephalon

Most rostral region of brain
Cerebrum
Cerebral hemispheres

Telencephalon overview

Gyri= ridges of brain tissue
Sulci= grooves between gyri
Lobes= large regions separated (mostly) by deep sulci; Frontal lobe, parietal lobe, occipital lobe, temporal lobe, insula
Three general “layers”
Cerebral cortex= outer region= gray matter
Cerebral white matter
Deep gray matter of cerebrum= Nuclei surrounded by the white matter

Cerebral cortex

Most complex part of the nervous system
Regional specializations discovered by:
lesions
Electrode studies
Imaging studies (e.g. fMRI= functional magnetic resonance imaging)- detect neuron activity

Cerebral cortex: Frontal lobe

Primary motor cortex: conscious control of voluntary movement
Premotor cortex: planning movements, coordinating with sensory info
Prefrontal cortex (anterior association area): most rostral region, long-term planning, problem solving, social skills, etc.

Prefrontal cortex clinical examples

Phineas Gage- injury
Prefrontal lobotomy- surgical destruction of prefrontal cortex or its connections

Cerebral cortex: Parietal lobe

Integration of sensory information, perception of spatial relationships
Somatosensory cortex
-receives and interprets general somatic senses (touch, pressure etc.)
-has somatotopy= body mapping (the map= sensory homunculus)
-contralateral (represents opposite side of body)
*primary motor cortex (in frontal lobe) also has somatotopy (map= motor homunculus), and is contalateral

Cerebral cortex: Occipital lobe

Primary visual cortex:
receives and processes information from eyes
has map of visual field (contralateral, inverted)
Visual association area:
further visual processing (e.g. form, movement)

Cerebral cortex: temporal lobe

Auditory cortex:
Receives and interprets auditory stimuli (hearing)
Exhibits tonotopy (mapping by sound frequency)
Olfactory cortex:
Receives and interprets olfactory stimuli (smell)
Close relationship with the limbic system (emotion and emotional memory)
Higher levels of visual processing- e.g. face recognition

Cerebral cortex: insula

Taste (gustatory cortex), general visceral senses, the conscious experience of balance
Integrate sensory information

Cerebral white matter (deep to cortex)

Myelinated fibers/tracts- for communication among different brain regions
Commissural fibers/tracts- connect corresponding areas of two hemispheres (e.g. corpus callosum)
Association fibers/tracts- connect regions within one cerebral hemisphere
Projection fibers/tracts- connect cerebral cortex to the rest of the system (e.g. internal capsule)

Deep gray matter of cerebrum

Surrounded by white matter
Basal ganglia= basal nuclei (not really ganglia)
Unconscious control of movement (e.g. repetitive rhythmic movement, habits)

Diencephalon

Thalamus
Hypothalamus
Epithalamus

Diencephalon: thalamus

Relay station and gateway to cerebral cortex
All incoming sensory inputs go through thalamus (except smell)
Amplify/filter sensations

Diencephalon: hypothalamus

Center of homeostasis/ control center for basic drives
Hunger, thirst, sex, etc.
Secrets hormones
Biological clock- master clock of circadian rhythm

Diencephalon: epithalamus

Pineal gland
Secretes melatonin (a hormone)
Conveys circadian rhythm from hypothalamus to rest of body

Mesencephalon

Midbrain
Corpora quadrigemina
Superior colliculi- visual reflexes
Inferior colliculi- auditory reflexes

Metencephalon

Pons= “bridge”
Tracts connecting midbrain, cerebellum, medulla
Cerebellum
Major coordinator of movement
Sends “smoothed out” blueprint to cerebral cortex
Also used in cognition
Half of all neurons in brain

Myelencephalon

Medulla oblongata
Most caudal brain region
relay between spinal cord and brain
Control of heart rate, blood pressure, ventilation rate

Functional brain systems

Scattered throughout the brain but serve closely- related function

Reticular formation

Primarily brain stem (midbrain, pons, medulla)
Arousal, alertness (reticular activating system= RAS)

Limbic system

Emotion, memory
Amygdala: fear
Cingulate gurus: reward-based decision-making
Hippocampus: forms long-term memories

The spinal cord

Conduction pathways between PNS and brain
Ascending pathway= TO brain
Descending pathway= FROM brain
A major reflex center (e.g. knee jerk reflex)

Spinal cord: gray matter

*nerves are NOT part of spinal cord
Has deep location
Contains:
Dorsal horns
Ventral horns
Lateral horns

Dorsal horns

Interneurons
Axon terminals of sensory neurons (somatic and visceral)

Ventral horns

Somatic motor neurons (cell body) and Interneurons
Sends signals out to skeletal muscles

Lateral horns

Visceral motor neurons (cell body) and Interneurons
Sends signals out to visceral organs- not used in somatic pathways

Spinal cord: white matter

Is superficial to the gray matter
Contains myelinated axons to and from brain
Dorsal, ventral, and lateral funiculi (columns)

Spinal cord: meninges

epidural space
Dura mater
subdural space
Arachnoid mater
Subarachnoid space (contains CSF)
Pia mater
Spinal tap (lumbar puncture)- take CSF sample from subarachnoid space