Neuroanatomy: structure and function

Rostral

toward the beak or nose; points to the front (anterior) of the brain

ex) the frontal lobe is rostral (anterior) compared to the occipital lobe

Caudal

toward the tail; points to the back (posterior) of the brain

ex) the occipital lobe is caudal (and posterior) to compared to the frontal lobe

Dorsal

toward the back; points to the top of the human brain

ex) the cerebral cortex sits dorsal (superior) to the brainstem

Ventral

toward the belly; points to the bottom (base) of the human brain

ex) the hypothalamus sits ventral (inferior) to the thalamus

Anterior/Posterior

synonymous with front and back of the head/brain in standard orientation

Medial/lateral

toward the middle (midline) or toward the outer edges

Why the meaning shifts between the brain and spinal cord?

Because of the upright posture of humans and the 90-degree ben (cephalic flexure) that occurs at the junction of the brainstem and forebrain

Central Nervous System (what it includes/functions)

consists of the brain and spinal cord; integrates and processes information, generates thoughts emotions and memories, initiates motor commands (processing)

Peripheral Nervous System (PNS)

cranial nerves, spinal nerves, ganglia; connects CNS to body, carries sensory input to CNS (afferent), carries motor output to muscles/glands (efferent) (detection)

Somatic

largely under voluntary control and involves a single neuron pathway from spinal cord to muscle; somatic reflex arc forces you to jump or flinch (subdivision of PNS)

Autonomic

controls involuntary, automatic functions (subdivision of PNS)

Sympathetic

(“fight or flight”) - mobilizes the body for action/stress (branch of autonomic nervous system)

Parasympathetic

(rest and digest) - conserves energy, promotes recovery

Explain how the central, peripheral, somatic, and autonomic divisions work together during an everyday event, such as reacting to a sudden loud noise

Sound waves hit your ears, activating sensory neurons within the PNS, the neurons instantly rush an electrical signal up toward your spine and brain, the auditory cortex in the CNS processes the sound, while the amygdala (brains alarm system) evaluates it as a threat, CNS sends split second orders back down through the PNS to initiate two types of responses (voluntary/internal survival tactics), before your brain fully comprehends what the noise was, a somatic reflex arc forces you to jump or flinch, as soon as the CNS processes the threat, your somatic system powers your muscles so u can turn your head toward the noise, duck or cover your ears, autonomic division (sympathetic branch - heart rate goes up, pupils widen —> parasympathetic branch - rest and digest, lowers heart rate, slows breathing)

Frontal lobe

movement, planning, decision-making, personality, executive functions

Parietal

touch, spatial awareness, integrating sensory information

Temporal

hearing, language comprehension, memory, spatial navigation

Occipital lobe

vision and perception

Damage to frontal lobe?

Will impair voluntary motor function, high-level executive cognition abilities, sensory and perceptual abilities will remain largely unaffected

Gray matter (in the brain)

made of neuronal cell bodies (somas), dendrites, synapses, unmyelinated axons, and glial cells

Function: processing and integration

Location: forms the outer surface layer, cortex

White matter (in the brain)

myelinated axons, forms the inner core, connects regions to each other

Function: transmission and connection

Limbic system

includes structures important for learning and memory, cognitive functions, emotional regulation, sense of smell

Components: hippocampus, cingulate gyrus, thalamus, hypothalamus, amygdala, mammillary bodies

Hippocampus

involved in learning, memory encoding, memory consolidation, and spatial navigation (not skill) —> Patient H.M.

Patient H.M.

lost some key cognitive functioning, kept the rest

the anterior temporal lobes on both sides were removed

patient could remember things for a very short time, which suggested that there is indeed a difference between short and long term memory (anterograde amnesia: inability to form new memories after onset of a disorder)

Amygdala

emotional processing, fear conditioning, modulation of memory, autonomic regulation

Thalamus

helps with integrating and relaying sensory information (central hub of the brain)

Hypothalamus

a small region located directly above the brainstem, helps maintain homeostasis

Cingulate gyrus

for emotional procession, pain perception, processing speed, memory, attention, etc

Mammillary bodies

important for memory and sense of direction; connected to the hippocampus via the fornix

Olfactory bulbs

receive, process, and relay neural signals representing odors from the nasal cavity to higher brain centers

Basal ganglia

includes the substantia nigra, caudate nucleus, globus pallidus, and putamen

looping neural system that is key in motor control

Substantia Nigra

located in the midbrain, “black substance”, produces chemical dopamine to help control movement, reward, and coordination

Parkinson’s disease affects nerve cells here

Brain stem

receives sensory information from the skin and muscles of the head and provides the motor control for the head’s musculature; conveys information from the spinal cord, and regulates levels of arousal and awareness through reticular formation

Midbrain

most superior of the subdivisions of the brain stem; aids in vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation

Superior and Inferior Colliculi

there are two of each on the midbrain, important for vision and hearing

Medulla Oblongata

directly rostral to the spinal cord; Includes several centers responsible for vital autonomic functions such as digestion, breathing, and the control of heart rate 

Pons

rostral to the medulla; conveys information about movement from the cerebral hemispheres to the cerebellum

taking drugs can over or under activate these functions

Diencephalon

lies rostral to the midbrain and contains two structures - the thalamus processes most of the information reaching the cerebral cortex from the rest of the central nervous system; the hypothalamus - regulates autonomic, endocrine, and visceral functions

Cerebrum

comprises two cerebral hemispheres, each consisting of a heavily wrinkled outer layer (the cerebral cortex) and three deep-lying structures (components of the basal ganglia the hippocampus, and amygdaloid nuclei); divided into two hemispheres, seperated by the longitudinal fissure

Spinal Cord

Receives and processes sensory information from the skin, joints, and muscles of the limbs and trunk; control movement of the limbs and the trunk

Dorsal horn (spinal cord)

processess afferent sensory information

Afferent neurons

carry sensory information from receptors in skin/other regions

Central nervous system

goes TO the brain

ventral horn (spinal cord)

processes efferent motor information

Efferent Neurons

exiting the brain

Dura mater

protective membrane that protects the brain; the outermost sheet; surrounds the CNS

Pia mater

delicate innermost layer

Arachnoid

substance between the dura mater and pia mater that cushions the brain in cerebrospinal fluid (CSF) 

Gyri and sulci

the brain’s surface is folded into ridges (gyri) and grooves (sulci); increases the brain’s surface area and houses various functional regions

Dendrites'/if it breaks

Receives messages from other neurons

If it breaks: the neuron never gets the message in the first place

Order signals travel

Dendrites, cell body (soma), axon hillock, axon, axon terminals

Cell body (soma)/if it breaks

adds up the messages and decides whether to fire

If it breaks: the neuron can’t make new proteins or keep its parts supplied, so over time the whole cell stops working

Axon/if it breaks

carries the signal over a long distance

If it breaks: the signal starts but never reaches the end

Axon terminals

passes the message to the next neuron

If it breaks: the signal reaches the end, but the next neuron never hears it

Axon hillock (axon initial segment)

junction between soma and axon; decision point where summation of inputs occurs; if threshold is reached, action potential starts here

Arbor Vitae

the tree-like pattern of white matter in the cerebellum responsible for transmitting information within this brain structure

Superior colliculi

paired structures in the midbrain that play a key role in visual processing; resembles a butt

Lateral ventricle

fluid-filled cavity in the brain that plays a role in cerebrospinal fluid circulation

Optic chiasma

the point where optic nerve fibers partially cross, allowing us to process visual information from both eyes

Pineal gland

Small structure in the brain that produces melatonin, a hormone involved in sleep-wake cycles; above the superior colliculus

Thalamus

A central relay station that processes sensory information to the cortex

Cerebellum

responsible for maintaining balance, and fine-tuning motor skills

Fornix

A bundle of nerve fibers that plays a role in memory and connects the hippocampus to other brain regions

Cerebellum

walnut little brain in the back; helps to coordinate muscle movement and fine motor control; behind the pons, functionally connected to the three main organs of the brain stem (medulla oblongata, the pons, the midbrain)

Corpus callosum

connects the left and right hemispheres

Explain how multiple brain structures contribute to a complex behavior catching a ball describing the sensory, motor, cognitive, or emotional role of each.

Catching a ball:

1) Occipital lobe - sensory processing

Receives raw visual data from the eyes to detect the ball’s shape, color, and initial movement

2) Parietal Lobe - sensory and cognitive

tracks the spatial location and trajectory of the ball. It calculates where the ball is in relation to your own body

3) Prefrontal cortex - cognitive

focuses attention on the ball, filters out background distractions, and makes the decision to initiate the catch

4) Motor cortex - motor execution

Sends specific electrical signals down the spinal cord to trigger muscle contractions in your arms, hands, fingers

5) basal ganglia - motor control

Prepares and smooths the motor plan ensuring you don’t overshoot or move too abruptly

6) Cerebellum - motor precision

Acts as the real-time error-corrector; constantly updates your movements based on the balls changing speed and wind adjustments

Explain how multiple brain structures contribute to a complex behavior feeling fear describing the sensory, motor, cognitive, or emotional role of each.

1) thalamus (sensory relay): receives the visual image of the snake

2) Amygdala: Processes the data; it instantly identifies the threat and triggers the survival instinct before you even consciously realize what you are looking at

3) Hypothalamus (autonomic control): receives the alarm from the amygdala and activates the fight-or-flight response, spiking your heart rate, blood pressure, and adrenaline

4) Prefrontal cortex (cognitive evaluation): decides if the snake for instance is real or just a rubber toy, ultimately signaling the amygdala to stand down if there is no actual danger

Myelination

dramatically increases both the speed and energy efficiency of action potential propagation by acting as an electrical insulator around the axon

Demyelination: slowed or blocked signaling, sensory and motor deficits, neurological diseases like MS

Dendritic Spine Loss

impaired learning and memory formation bc spine remodeling is essential for encoding new information, losing spines prevents the brain from strengthening new neural pathways, cognitive decline, synaptic failure

Sagittal

Coronal

Horizontal

Precentral Gyrus

located immediately anterior to the central sulcus, acts as the primary motor cortex, important for voluntary movement

Inferior Frontal Gyrus

the lower part of this gyrus houses Broca’s area; damage to it results in Broca’s aphasia where people can understand things normally but they can’t put a sentence together

Postcentral gyrus

located immediately posterior to the central sulcus; serves as the Primary Somatosensory cortex

Superior Temporal Gyrus

contains the Primary auditory cortex and wernicke’s area (in the dominant (left) hemisphere where language is)

Fusiform gyrus

located on the inferior/ventral surface, it is highly specialized for visual processing , particularly object and facial recognition

Damage: people cannot put together a pattern and recognize faces, even their own

Lingual gyrus

located on the medial surface below the calcarine sulcus, it is involved in vision and color perception

Damage: lose a quarter of their vision

Contralateral Communication

pertaining to the other side; most of our senses decussate to the contralateral hemisphere

Ipsilateral communication

belonging to or occurring on the same side of the body

Cerebrospinal spinal fluid (CSF)

bathes, cushions, and supports the brain and spinal cord within the central nervous system