Lecture 8 - Neuroanatomy

FINAL CUE CARDS

dorsal

Top (superior)

ventral

Bottom (inferior)

anterior (or rostral)

Toward the nose (front)

posterior (or caudal)

Toward the tail (back)

lateral

Toward the sides

medial

Toward the middle

Midsagittal plane

Divides brain into left and right halves.

horizontal plane

Divides brain into top and bottom halves.

coronal plane

Divides brain into front and back halves

ipsilateral

same side

contralateral

opposite side

Parts of CNS common to all mammals

Cerebrum (Cortex), Cerebellum, Brainstem, spinal cord

Spinal cord

part of CNS

sagittal fissure

deep groove that divides cerebrum into a left and right hemisphere

Five-Vesicle Stage (5 week in human)

• Neural tube differentiates into five primary vesicles:

  1. Telencephalon → Becomes the cerebral cortex and basal ganglia.

  2. Diencephalon → Forms the thalamus and hypothalamus.

  3. Midbrain (Mesencephalon) → Forms structures related to sensory and motor processing.

  4. Hindbrain (Rhombencephalon) → Becomes the pons, medulla, and cerebellum.

  5. Spinal Cord → Develops into the central nervous system (CNS) communication pathway

main divisions of forebrain

1. Telencephalon

2. Diencephalon

gray matter structure

neuronal cell bodies that process and relay information

• cerebral cortex

• thalamus (relay sensory information)

• hypothalamus (control centre - homeostasis control)

• basal telencephalon

white matter structures

myelinated axons that connect different brain regions.

• corpus callosum (main one, connects 2 sides of brain)

• cortical white matter

• internal capsule (lots of projections that go to and from cortex to different areas)

ventricles

fluid filled cavities that circulate cerebrospinal fluid (CSF)

1. lateral ventricles - adjacent from cortex

2. third ventricles - lines hypothalamus and thalamus

Gyri

bumps - raised ridges on the brain's surface.

sulci

grooves between gyri.

fissures

deep groves separating major brain regions.

central sulcus

groove separating precentral and postcentral gyrus

precentral gyrus

important for voluntary movement

postcentral gyrus

important for somatic sensation touch

lateral (sylvian) fissure

separates different lobes

superior temporal gyrus

important for auditory

cerebral lobes (in telencephalon)

1. frontal lobe

2. temporal lobe

3. parietal lobe

4. occipital lobe

5. insula

frontal lobe boarding

• largest lobe

• bordered by

  1. Lateral sulcus (sylvian fissure)

     • frontal and temporal

  2. central sulcus

     • frontal and parietal

frontal lobe function

• action (mental and physical)

  • executive functioning, ex. planning, problem solving, motivation, judgement, decision making, impulse control, social behaviour, personality, memory, learning, rewards, attention)

  • motor, ex. skeletal muscle movement, ocular movement, speech control, facial movement

functioning areas of frontal lobe

primary motor cortex - voluntary muscle movement

premotor/supplementary motor cotrex (MAC) - planning coordination of movement

frontal eye field - voluntary rapid eye movement

prefrontal cortex - executive functions, behaviour planning

brocas area - muscles of speech, production of speech (LEFT SIDE)

parietal lobe function

somatosensory

• awareness of somatic sensation

  • touch, pain, temperature, pressure vibration

• processing somatic sensation

  • analyzing, recognizing, memory of somatic sensation

• proprioception

  • coordination of visual, auditory, and somatosensory stimuli

  • spacial and body awareness

somatosensory cortex

• located in parietal lobe

• processes sensory information from the body, including touch, pain, temperature, and pressure.

• homunculus

functioning areas of parietal lobe

• primary somatosensory cortex - awareness signal

• somatosensory assoc. cortex (SAC) - processing and analyzing signal

• posterior association area - visual, auditory, somatosensory areas meet, spacial awareness

occipital lobe function

visual

• awareness of visual stimuli (seeing)

• processing visual stimuli (analyzing, recognizing, memory, shapes, colours, sizes)

functional areas of occipital lobe

• primary visual cortex - awareness visual stimuli

• visual assoc. cortex - processing visual stimuli

temporal lobe function

auditory

• awareness of auditory stimuli (hearing sounds, pitch, frequency)

• processing auditory stimuli (analyzing, recognizing, memory)

functional areas of temporal lobe

• primary auditory cortex - awareness auditory stimuli

• auditory assoc. cortex - processing sounds

• wernicke’s area -comprehend/understand written/spoken language

• primary olfactory cortex/association cortex - awareness and processing of smell

insular cortex

deep within lateral sulcus

responsible for taste, visceral sensation (ex. feeling full, bloated), autonomic control, vestibular information, equilibrium

neocortical evolution

cortex amount has changed (not structure)

• conserved primary sensory areas, secondary sensory areas, motor areas

• expansion of secondary sensory areas

  • ASSOCIATIVE AREAS - interpreting, organizing, remembering information

corpus callosum

part of telencephalon that joins 2 sides of brain

white matter structure

what side of brain is responsible for speech

LEFT side of brain

what side of brain is responsible for detecting faces

RIGHT side of brain

severed corpus callosum

separates 2 sides of brain, preventing left and side brain from communicating with each other

ex. if word flashed to right, it’s interpreted by left side of brain responsible for speech, so patient able to speak the word. but if flashed to left side, interpreted by right side of brain, and because 2 sides of brain can’t communicate, patient not able to speak.

amygdala

part of telencephalon

function: fear response

composed of

• corticomedial nuclei - receive olfactory (smell) nafferents

• basolateral nuclei - receive visual, auditory, gustatory, and tactile afferents

hippocampus

part of telencephalon

function: learning and memory

“sea horse” shape

proximity to lateral geniculate nucleus, and medial geniculate nucleus

hippocampus trisynaptic pathway

• Information enters via the entorhinal cortex → Sent to dentate gyrus (DG).

• Mossy fibers from DG synapse onto CA3 pyramidal neurons.

• Schaffer collaterals from CA3 synapse onto CA1 pyramidal neurons.

Brocas Limbic System (telencephalon)

cortex forming a ring around corpus callosum: Cingulate gyrus, medial surface temporal lobe, hippocampus

the papez circuit

important in memory and ability to process emotions

1. Cingulate Cortex → Receives emotional input from the neocortex (thinking part of the brain).

2. Hippocampus → Processes emotions and memory.

3. Fornix → A communication highway that sends signals from the hippocampus to the hypothalamus.

4. Hypothalamus → Controls physical emotional responses (e.g., heart rate, sweating).

5. Anterior Thalamus → Acts as a relay station, sending the processed emotion back to the cingulate cortex.

6. Cingulate Cortex → Completes the loop by helping process the emotion and connecting it to memories.

2 structures in diencephalon

thalamus

hypothalamus

thalamus function

gateway to cortex

it takes in sensory information to cerebral cortex

hypothalamus function

homeostasis - regulatory process (ex. body temp. and blood composition)

• commands in cold weather (shiver, goosebumps, turn blue)

• commands in hot weather (turn read, sweat)

• controls metabolism (eating energy)

structures of telencephalon

• cerebral cortex - 5 lobes (brodman’s area)

• subcortical structures

  • corpus callosum

  • amygdala

  • hippocampus

structures of brainstem

1. Mesencephalon (midbrain)

   • tegmentum and tectum

2. Rhombencephalon (hindbrain)

   • pons and medulla

Tectum

the roof of the mesencephalon

• superior colliculus - orientating, eye movements

• inferior colliculus - auditory responses

Tegmentum

the large covering of the mesencephalon

• motor

• attention, alertness

• autonomic function

• consists of cerebral aqueduct, periaqueductal gray, reticular formation, substantia nigra, and red nucleus

Pons

portion of hindbrain that connects the cortex with the medulla

communication and coordination centre between the two hemisphere of brain

(like white matter tracts)

Medulla

controls autonomic functions (ex. breathing, digestion, heart and blood vessel function, swallowing, and sneezing)

motor and sensory neurons from midbrain and forebrain travel through this

cerebellum

“little brain”

• contains as many neurons as BOTH cerebral hemispheres

• primary movement centre

• **left controls left, right controls right

ventricles

cerebrospinal fluid (CSF) filled caverns and canals inside brain

choroid plexus

specialized tissue in ventricles that secretes CSF. This circulates through ventricles, and is reabsorbed in subarachnoid space

hydrocephalus

abnormal accumulation of spinal fluid in the chambers of the brain. The most common symptoms include headaches, memory problems, walking difficulties and urinary incontinence.

cranial nerves

12 of them

• olfactory and optic nerves serve olfaction and vision

• other 10: contain axons of PNS